首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   5047篇
  免费   481篇
  国内免费   1篇
农学   12篇
  8篇
综合类   3篇
农作物   2篇
水产渔业   5篇
畜牧兽医   5496篇
植物保护   3篇
  2024年   6篇
  2023年   91篇
  2020年   167篇
  2019年   3篇
  2018年   122篇
  2017年   134篇
  2016年   86篇
  2015年   145篇
  2014年   225篇
  2013年   243篇
  2012年   181篇
  2011年   210篇
  2010年   167篇
  2009年   247篇
  2008年   152篇
  2007年   96篇
  2006年   82篇
  2005年   81篇
  2004年   144篇
  2003年   147篇
  2002年   166篇
  2001年   159篇
  2000年   122篇
  1999年   118篇
  1998年   171篇
  1997年   180篇
  1996年   160篇
  1995年   159篇
  1994年   140篇
  1993年   153篇
  1992年   175篇
  1991年   148篇
  1990年   187篇
  1989年   131篇
  1988年   114篇
  1987年   145篇
  1986年   60篇
  1985年   78篇
  1984年   82篇
  1983年   80篇
  1982年   36篇
  1981年   12篇
  1980年   7篇
  1977年   4篇
  1974年   2篇
  1961年   2篇
  1960年   1篇
  1958年   1篇
  1956年   1篇
  1947年   1篇
排序方式: 共有5529条查询结果,搜索用时 140 毫秒
241.
Objective —To evaluate the outcomes and complications in a consecutive series of animals undergoing microvascular reconstructive procedures at two veterinary institutions. Study Design—Retrospective study. Animals or Sample Population—A total of 44 client-owned dogs and one red-necked wallaby. Methods —The medical records of all animals undergoing reconstructive microsurgical procedures at the Western College of Veterinary Medicine and Michigan State University were reviewed. Microvascular flap survival and related complications were described. Statistical analysis was performed to determine the significance of relationships between operative factors and outcome. Results —A total of 57 microvascular procedures were performed on 55 animals. Reconstruction was required after trauma in 42 animals, after ablative cancer surgery in 11 animals and for correction of congenital tissue aplasia in 1 animal. Donor tissues included the superficial cervical cutaneous, medial saphenous fasciocutaneous or musculofasciocutaneous, caudal superficial epigastric cutaneous, trapezius muscle or musculocutaneous, caudal sartorius muscle, latissimus dorsi muscle or musculocutaneous, cranial abdominal myoperitoneal, carpal footpad, digital footpad, and vascularized ulnar bone flaps. A total of 53 of 57 flaps (93%) survived. There was a significant relationship between flap failure and level of assistant surgeon experience (P < .05). Latissimus dorsi flaps were significantly more likely to fail when compared with pooled data from all other flap types (P < .01). Conclusions —The success of microvascular tissue transfer in this case series compares favorably with those reported in human reconstructive microsurgery. Both the primary and assistant surgeon should be practiced in microsurgical technique. Failure of latissimus dorsi flaps was not likely caused by an inherently deficient flap design, but was more likely attributed to the location and severity of trauma at the recipient site, the difficulty in isolating suitable recipient vessels for anastomosis or the absence of a trained assistant surgeon during these procedures. Clinical Relevance —This retrospective study documents the successful application of microvascular technique in a series of clinical cases requiring tissue reconstruction.  相似文献   
242.
Objective —To describe function and identify factors that affect outcome in dogs undergoing limb salvage surgery for osteosarcoma (OS) of the proximal humerus.
Study Design —A retrospective study of dogs in which OS of the proximal humerus was treated with limb salvage surgery.
Animals —17 client-owned dogs.
Methods: Records were analyzed for functional outcome, recurrence, metastasis, and survival.
Results —Outcome was good to excellent in 12% of dogs. Recurrence, metastasis, and survival were significantly affected by completeness of surgical margins. Double plating of the distal allograft-host junction significantly reduced frequency of biomechanical failure.
Conclusions —Limb salvage surgery for OS of the proximal humerus did not result in acceptable function and was fraught with postoperative complications. Outcome was significantly affected by completeness of surgical margins.
Clinical Relevance —Limb salvage surgery for OS of the proximal humerus in dogs cannot be recommended until improvement in functional outcome and reduction in postoperative complications can be achieved. The dependence of outcome on completeness of surgical margins supports aggressive en bloc resection and marking and evaluating surgical margins.  相似文献   
243.
Simple complete dorsal fractures of the proximal phalanx were repaired in 2 mature pleasure horses with cortical bone screws placed in lag fashion. Healing occurred within 12 weeks and both horses returned to their previous performance level of light pleasure riding within 6 months of injury.  相似文献   
244.
Objective—To determine the plasma concentrations and cardiovascular changes that occur in healthy dogs and dogs with aortic stenosis that are given an infusion of lidocaine during isoflurane anesthesia. Study Design—Phase 1, controlled randomized cross-over trial; Phase 2, before and after trial Animals—Phase 1, 6 healthy dogs (4 female, 2 male) weighing 23.8 ± 7.4 kg; Phase 2, 7 dogs (4 female, 3 male) with moderate to severe subaortic stenosis (confirmed by Doppler echocardiography) weighing 31.1 ± 14.5 kg. Methods—After mask induction, intubation, and institution of positive pressure ventilation, instrumentation was performed to measure hemodynamic variables. After baseline, measurement at an end-tidal isoflurane concentration of 1.9% (phase 1) or 1.85% (phase 2), a loading dose infusion of lidocaine at 400 μg/kg/min was given. Phase 1: Maintenance doses of lidocaine were administered consecutively (40, 120, and 200 μg/kg/min) after the loading dose (given for 10, 10, and 5 minutes, respectively) in advance of each maintenance concentrations. Measurements were taken at the end of each loading dose and at 25 and 35 minutes during each maintenance level. The same animals on a different day were given dextrose 5% and acted as the control. Phase 2: Dogs were studied on a single occasion during an infusion of lidocaine at 120 μg/kg/ min given after the loading dose (10 minutes). Measurements occurred after the loading dose and at 25 and 35 minutes. A blood sample for lidocaine concentration was taken at 70 minutes. Data were compared using a one-way ANOVA for phase 1, and between phase 1 and 2. Statistical analysis for phase 2 was performed using a paired r-test with a Bonferroni correction. A P value ± .05 was considered significant. Results—Phase 1: Plasma lidocaine concentrations achieved with 40, 120, and 200 μg of lidocaine/kg/min were 2.70, 5.27, and 7.17 μg/mL, respectively. A significant increase in heart rate (HR) (all concentrations), central venous pressure (CVP), mean pulmonary areterial pressure (PAP), and a decrease in stroke index (SI) (200 μg/kg/min) were observed. An increase in systemic vascular resistance (SVR) and mean PAP, and a decrease in SI also followed the loading dose given before the 200 μg/kg/min infusion. No other significant differences from the control measurements, during dextrose 5% infusion alone, were detected. Phase 2: Plasma lidocaine concentrations achieved were 5.35, 4.23, 4.23, and 5.60 μg/mL at 10, 25, 35, and 70 minutes, respectively. They were not significantly different from concentrations found in our healthy dogs at the same infusions. A significant but small increase in CVP compared with baseline was noted after the loading dose. There were no significant differences from baseline shown in all other cardiovascular data. There were no statistically significant differences in any measurements taken during the lidocaine infusion between the dogs in phase 1 and phase 2. Dogs with aortic stenosis tended to have a lower cardiac index than healthy dogs at baseline (88 v 121 mL/kg/min) and during lidocaine infusion (81 v 111 mL/kg/min). A small, statistically significant difference in systolic PAP was present at baseline. Conclusions—There does not appear to be any detrimental cardiovascular effects related to an infusion of lidocaine at 120 μg/kg/min during isoflurane anesthesia in healthy dogs or dogs with aortic stenosis. The technique used in this study resulted in therapeutic plasma concentrations of lidocaine. Clinical Relevance—Methods shown in the study can be used in clinical cases to achieve therapeutic lidocaine levels without significant cardiovascular depression during isoflurane anesthesia.  相似文献   
245.
Objective—To assess feasibility of insertion of 4.5-mm Herbert cannulated bone screws (HS) using fluoroscopic guidance and compare the mechanical shear strength of these HS and 4.5-mm AO cortical bone screws (AO) for fixation of dorsal plane slab osteotomies in equine cadaver third carpal bones (C3).
Animals or Sample Population—Eight equine cadavers.
Methods—Bone mineral composition and density of contralateral C3 were confirmed to be equivalent using dual-energy x-ray absorptiometry. A standard 10-mm C3 slab osteotomy was reduced using HS or AO instrumentation under fluoroscopic guidance. Specimens were loaded in shear until failure, using a materials testing apparatus.
Results—HS and AO instrumentation allowed accurate reconstruction of the osteotomy, but there was difficulty encountered seating the HS proximal self-tapping threads. There was no significant difference in maximal load to failure, stiffness, or mode of failure of constructs created with the HS and AO screws.
Conclusions —Use of 4.5-mm HS for repair of C3 radial facet, dorsal plane slab fractures may result in a mechanically comparable fixation to a repair using a 4.5-mm AO. Equine dorsal C3 may be too dense, however, to allow placement of the proximal self-tapping threads of the HS without potentially excessive application of torque to the screw itself.
Clinical Relevance —Dorsal plane, radial facet slab fractures of the equine C3 are a significant clinical problem. Accurate reconstruction and stabilization are necessary for return to athletic function.  相似文献   
246.
Objective —To determine if omentectomy would decrease the frequency of postoperative intraabdominal adhesions. Study Design —Retrospective study. Animals or Sample Population—44 horses that had either two ventral median celiotomies or a ventral median celiotomy and a necropsy more than 4 days later; 19 of these horses had their omentum removed at the initial surgery. Methods —Data retrieved from the records included location and type of intraabdominal adhesions; location of the surgical lesion; relationship of adhesions to the surgical lesion; surgical procedures; duration of initial surgery; time interval between procedures; age, gender, and breed of the horse; and clinical outcome. Fisher's exact test was used to evaluate the association between categorical explanatory and outcome variables. The effect of potential risk factors on the incidence rate of adhesion formation was estimated using a proportional hazards regression model. Results —Of 25 horses in the nonomentectomy group, 15 (60%) had postoperative adhesions that resulted in the need for a second surgical intervention, whereas of 19 horses that had omentectomy initially, only 4 (21%) had postoperative adhesions that required a second procedure. Rate of adhesion formation was higher in horses that did not have omentectomy initially (incidence ratio rate [IRR], 0.46; 90% confidence interval [CI], 0.18 to 1.19). At initial surgery, 24 horses had a small intestinal lesion, and 20 horses had a large intestinal lesion. Fifteen horses (63%) with small intestinal lesions subsequently developed adhesions compared with four horses (20%) with an initial large intestinal lesion (P= .006). At the second procedure, small intestine lesions were identified in 32 horses and large intestine lesions in 12 horses (1 horse had both small and large intestine lesions), and 1 horse had a gastric lesion. Adhesions were identified as the cause of colic signs in 19 (61%) horses with small intestinal lesions and in none of the horses with large intestine lesions. The frequency of adhesion development leading to colic associated with only the small intestine at the second surgery or necropsy was significantly greater (P= .001) than the frequency only in the large intestine. Conclusions —Omentectomy reduced the rate of postoperative adhesion formation. Adhesions are more likely to occur after small intestinal surgery and if they do occur likely involve the small intestine. Clinical Relevance —Omentectomy is a safe procedure and should be considered prophylactically for reduction of adhesion formation after abdominal surgery in horses.  相似文献   
247.
Objective—To compare plasma fentanyl concentrations attained after the application of three transdermal fentanyl patch sizes (50, 75, and 100 μg/hour) in dogs. Design—Repeated Latin square controlled study. Animals—Six intact, mixed-breed adult dogs (2 males, 4 females) weighing 19.9 ± 3.4 kg. Methods—Each dog was randomly assigned to receive each of three treatments: 50 (P50), 75 (P75), or 100 (P100) μg/hour transdermal patches. Patches were left in place for 72 hours. Jugular venous blood was collected at 1,2, 4, 8, 12, 24, 36, 48, 60, and 72 hours after patch application and for 1, 2, 4, 8, and 12 hours after patch removal. Plasma fentanyl concentrations were measured using a radioimmunoassay technique. After a 96-hour washout period, each dog was moved to another treatment group and received a different patch size. Results—The following results were obtained (mean ± SD): average plasma fentanyl concentration from 24 to 72 hours, 0.7 ± 0.2 ng/mL (P50), 1.4 ± 0.5 ng/mL (P75), 1.2 ± 0.5 ng/mL (P100); the total area under the concentration versus time curve (0 hours to infinity), 46 ± 12.2 ng/h/mL (P50), 101.2 ± 41.4 ng/h/mL (P75), 80.4 ± 38.3 ng/h/mL (P100); and the apparent elimination half-life, 3.6 ± 1.2 hours (P50), 3.4 ± 2.7 hours (P75), and 2.5 ± 2.0 hours (P100). There was a high degree of variability in plasma fentanyl concentrations achieved. Plasma fentanyl concentrations declined rapidly after patch removal. Conclusions—The attainment of steady-state plasma concentrations takes up to 24 hours, and there is a great deal of variability in the final concentrations reached in different individuals. In this study, the 100 μg/hour patches did not provide statistically increased plasma concentrations when compared with the 50 μg/hour patches. Clinical Relevance—Because of the interindividual and intraindividual variation in plasma fentanyl concentrations, patches should be applied 24 hours before the anticipated time that analgesia will be required. Adequacy of analgesia and potentially deleterious side effects, such as sedation and respiratory depression, should be monitored while the patches are in place. Skin reactions may occur, and the patches should be removed if such skin irritation is seen. After the patch is removed, it is expected that analgesia will wane rapidly because of the brief elimination half-life.  相似文献   
248.
This study reports data obtained from per-rectal 99mTc-pertechnetate portal scintigraphy in normal cats. It examines the effects of chemical restraint and the methods employed in defining regions of interest (ROIs) on the shunt index derived from this data. Six normal cats were used for the study; all six were chemically restrained for imaging using propofol and later four of them were manually restrained for comparison. Portal blood flow was studied and the mean shunt index was found to be 5.9%± 3.9 when ROIs were operator defined and 9.2%± 4.4 when ROIs were defined using an isocontour program. In cats that were restrained using propofol and operator defined ROIs, the mean value for the time between detection of radioactivity in the liver and in the heart was 14 ± 1 seconds.  相似文献   
249.
THE DURAL TAIL SIGN IN THE DIAGNOSIS OF MENINGIOMAS   总被引:3,自引:0,他引:3  
John P.  Graham  MVB  MSc  Susan M.  Newell  DVM  MS  Andra K.  Voges  DVM  Gregory D.  Roberts  DVM  MS  Jay M.  Harrison  MS 《Veterinary radiology & ultrasound》1998,39(4):297-302
In humans the dural tail is a sign seen on contrast enhanced T1 weighted magnetic resonance images. This finding is considered specific for meningioma. The purpose of this study was to determine how often the dural tail occurs in cats and dogs and whether it is a specific sign for meningiomas in these species. MR examinations for eighteen dogs and four cats with proven diagnoses were reviewed. Diagnoses included ten meningiomas (seven dogs and three cats), three gliomas, two pituitary tumors, single examples of two other tumor types and five patients with mass lesions due to inflammatory disease. Contrast enhanced T1 weighted images were evaluated independently by three of the authors for the presence of a dural tail, without knowledge of the diagnoses. The results were compared to the diagnosis for each patient and the performance of individual reviewers compared. When their results were averaged, the reviewers reported the presence of a dural tail in 6 of 10 (60%) meningiomas, although detection varied between observers from 40% to 80%. Each reviewer had one false positive result, two reported a dural tail with a chromophobe adenocarcinoma and one with a toxoplasma meningoencephalitis. When a dural tail is seen an associated mass is most likely a meningioma. It is uncertain whether the dural tail represents neoplastic infiltration beyond the margins of the meningioma. This should be considered when planning treatment.  相似文献   
250.
Image magnification is inherent in radiography. In digital fluoroscopy, the three components of magnification are geometric, electronic and photographic. In this study, the total magnification factor of a digital imaging system was determined by two methods, 1) comparison of measurements of a known object to its image and 2) calculation of geometric, electronic and photographic magnification from the imaging system specifications. Both methods were employed for various focal-film distances, image intensifier tube modes and laser printer formats. Results of these two methods were different due to the detrimental effect of penumbra on image quality with increasing magnification. If a radiographic image is to be used to approximate object size, then a technique should be used that will minimize magnification. In digital fluoroscopy this is achieved with the shortest object-film distance (assuming a fixed focal-object distance), largest image intensifler mode and greatest number of images per sheet of film.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号