全文获取类型
收费全文 | 112926篇 |
免费 | 5590篇 |
国内免费 | 79篇 |
专业分类
林业 | 5293篇 |
农学 | 3668篇 |
基础科学 | 738篇 |
12759篇 | |
综合类 | 20197篇 |
农作物 | 4291篇 |
水产渔业 | 5131篇 |
畜牧兽医 | 58885篇 |
园艺 | 1307篇 |
植物保护 | 6326篇 |
出版年
2018年 | 1380篇 |
2017年 | 1476篇 |
2016年 | 1430篇 |
2015年 | 1231篇 |
2014年 | 1449篇 |
2013年 | 3954篇 |
2012年 | 2766篇 |
2011年 | 3353篇 |
2010年 | 2209篇 |
2009年 | 2083篇 |
2008年 | 3174篇 |
2007年 | 3151篇 |
2006年 | 3055篇 |
2005年 | 2929篇 |
2004年 | 2762篇 |
2003年 | 2813篇 |
2002年 | 2669篇 |
2001年 | 3453篇 |
2000年 | 3349篇 |
1999年 | 2684篇 |
1998年 | 1126篇 |
1997年 | 1074篇 |
1995年 | 1195篇 |
1994年 | 1067篇 |
1992年 | 2356篇 |
1991年 | 2556篇 |
1990年 | 2669篇 |
1989年 | 2580篇 |
1988年 | 2438篇 |
1987年 | 2385篇 |
1986年 | 2348篇 |
1985年 | 2300篇 |
1984年 | 1915篇 |
1983年 | 1596篇 |
1982年 | 1172篇 |
1981年 | 1059篇 |
1979年 | 1801篇 |
1978年 | 1427篇 |
1977年 | 1210篇 |
1976年 | 1200篇 |
1975年 | 1276篇 |
1974年 | 1632篇 |
1973年 | 1583篇 |
1972年 | 1652篇 |
1971年 | 1565篇 |
1970年 | 1528篇 |
1969年 | 1311篇 |
1968年 | 1101篇 |
1967年 | 1259篇 |
1966年 | 1094篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
A rapid and strong laparoscopic-assisted gastropexy in dogs 总被引:1,自引:0,他引:1
Rawlings CA Foutz TL Mahaffey MB Howerth EW Bement S Canalis C 《American journal of veterinary research》2001,62(6):871-875
OBJECTIVE: To develop a technique for laparoscopic gastropexy in dogs and evaluate effects on stomach position and strength of the adhesion between the stomach and abdominal wall. ANIMALS: 8 healthy dogs. PROCEDURE: Dogs were anesthetized, and the abdomen was insufflated with carbon dioxide. A laparoscope was placed through a cannula inserted on the abdominal midline caudal to the umbilicus. Babcock forceps placed through a cannula inserted lateral to the right margin of the rectus abdominus muscle were used to exteriorize the pyloric antrum, a longitudinal incision was made through the serosa and muscular layer of the pyloric antrum, and the seromuscular layer of the pyloric antrum was sutured to the transversus abdominus muscle. After surgery, positive-contrast gastrography was used to evaluate stomach position and the onset of gastric emptying, and ultrasonography was used to assess stomach wall activity and mobility. Dogs were euthanatized 1 month after surgery, and tensile strength of the adhesion was tested. RESULTS: In all dogs, stomach position and the onset of gastric emptying were normal 25 days after surgery, and the pyloric antrum was firmly attached to the abdominal wall 30 days after surgery. Mean +/- SD ultimate load of the adhesion in tension was 106.5 +/- 45.6 N. CONCLUSIONS AND CLINICAL RELEVANCE: The laparoscopic gastropexy technique described in the present study could be performed quickly and easily by an experienced surgeon, resulted in a strong fibrous adhesion between the stomach and abdominal wall, and appeared to cause minimal stress to the dogs. 相似文献
992.
Mc Entee K Flandre T Dessy C Desmecht D Clercx C Balligand M Michaux C Jonville E Miserque N Henroteaux M Keene B 《American journal of veterinary research》2001,62(6):889-894
OBJECTIVE: To assess morphologic and metabolic abnormalities in dogs with early left ventricular dysfunction (ELVD) induced by rapid right ventricular pacing (RRVP). ANIMALS: 7 Beagles. PROCEDURE: Plasma carnitine concentrations were measured before and after development of ELVD induced by RRVP. At the same times, transvenous endomyocardial biopsy was performed, and specimens were submitted for determination of myocardial carnitine concentrations and histologic, morphometric, and ultrastructural examination. RESULTS: In 4 dogs in which baseline plasma total carnitine concentration was normal, RRVP induced a decrease in myocardial total and free carnitine concentrations and an increase in myocardial esterified carnitine concentration. In 3 dogs in which baseline plasma total carnitine concentration was low, plasma and myocardial carnitine concentrations were unchanged after pacing. Structural changes associated with pacing included perinuclear vacuolization in 3 dogs. Morphometric analyses indicated there was a decrease in myofiber cross-sectional diameter and area following pacing. Electron microscopy revealed changes in myofibrils and mitochondria following pacing. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicated that moderate to severe alterations in myocyte cytoarchitecture are present in dogs with ELVD induced by RRVP and that in dogs with normal plasma carnitine concentrations, myocardial carnitine deficiency may be a biochemical marker of ELVD. Results also indicated that transvenous endomyocardial biopsy can be used to evaluate biochemical and structural myocardial changes in dogs with cardiac disease. 相似文献
993.
Michail N. Patsikas DVM PhD Timoleon Rallis DVM PhD Stefanos E. Kladakis DVM Aggelos K. Dessiris DVM PhD 《Veterinary radiology & ultrasound》2001,42(3):235-237
Isolated splenic torsion in a dog was diagnosed using computed tomography (CT). The enlarged non enhanced spleen and a twisted soft tissue mass effect represented the rotated pedicle were the main findings. Abdominal radiography and ultrasonography were not conclusive. 相似文献
994.
R M Dabareiner J P Watkins G K Carter C M Honnas T Eastman 《Journal of the American Veterinary Medical Association》2001,219(1):82-86
OBJECTIVE: To determine clinical, radiographic, and scintigraphic abnormalities in and outcome of horses with septic or nonseptic osteitis of the axial border of the proximal sesamoid bones. DESIGN: Retrospective study. ANIMALS: 8 horses. PROCEDURE: Data collected from medical records included signalment; history; horse use; severity and duration of lameness; results of perineural anesthesia, radiography, ultrasonography, and scintigraphy; and outcome following surgery. RESULTS: Five horses did not have any evidence of sepsis; the other 3 had sepsis of the metacarpophalangeal or metatarsophalangeal joint or the digital synovial sheath. All horses had a history of chronic unilateral lameness. Three of 5 horses improved after diagnostic anesthesia of the metacarpophalangeal or metatarsophalangeal joint; the other 2 improved only after diagnostic anesthesia of the digital synovial sheath. Nuclear scintigraphy was beneficial in localizing the source of the lameness to the proximal sesamoid bones in 4 horses. Arthroscopy of the palmar or plantar pouch of the joint or of the digital synovial sheath revealed intersesamoidean ligament damage and osteomalacia of the axial border of the proximal sesamoid bones in all horses. All 5 horses without sepsis and 1 horse with sepsis returned to their previous uses. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that osteitis of the axial border of the proximal sesamoid bones is a distinct entity in horses that typically is associated with inflammation of the associated metacarpointersesamoidean or metatarsointersesamoidean ligament and may be a result of sepsis or nonseptic inflammation. Arthroscopic debridement may allow horses without evidence of sepsis to return to their previous level of performance. 相似文献
995.
Advanced reproductive techniques in goats. 总被引:2,自引:0,他引:2
K N Bretzlaff J E Romano 《Veterinary Clinics of North America: Food Animal Practice》2001,17(2):421-34, viii
The use of ultrasonography for pregnancy diagnosis and reproductive tract evaluation in the goat has become more common in the past decade. Pregnancy-specific hormone assays are commercially available for pregnancy determination in goats. Hormonal methods of synchronization of estrus for artificial insemination have been refined, but a number of factors still make pregnancy results variable. Caprine embryo transfer is widely used commercially. More advanced reproductive techniques such as in-vitro production of embryos and cloning have been accomplished in goats; success rates with these techniques will likely rapidly improve. 相似文献
996.
Naganobu K Hagio M Sonoda T Kagawa K Mammoto T 《American journal of veterinary research》2001,62(1):127-129
OBJECTIVE: To determine effects of hypercapnia on arrhythmias in ducks anesthetized with halothane. ANIMALS: 12 ducks, 6 to 8 months old, weighing 1.1 to 1.6 kg. PROCEDURES: Each duck was anesthetized with a 1.5% mixture of halothane in oxygen, and anesthetic depth was stabilized during a 20-minute period. We added CO2 to the inspired oxygen to produce CO2 partial pressures of 40, 60, and 80 mm Hg in the inspired gas mixture.The CO2 partial pressure was increased in a stepwise manner. When arrhythmias were not evident during inhalation of the gas mixture at a specific CO2 partial pressure, the CO2 partial pressure was maintained for 10 minutes before a sample was collected for blood gas analysis. When arrhythmias were detected, a sample for blood gas analysis was collected after the CO2 partial pressure was maintained for at least 2 minutes, and CO2 inhalation then was terminated. RESULTS: During the stabilization period, PaCO2 (mean +/- SD) was 33 +/- 5 mm Hg,and arrhythmias were not detected. In 6 ducks, arrhythmias such as unifocal and multifocal premature ventricular contractions developed during inhalation of CO2. Mean PaCO2 at which arrhythmias developed was 67 +/- 12 mm Hg. In 5 of 6 ducks with arrhythmias, the arrhythmias disappeared after CO2 inhalation was terminated. CONCLUSION AND CLINICAL RELEVANCE: Analysis of data from this study indicated that hypercapnia can lead to arrhythmias in ducks during halothane-induced anesthesia. Thus, ventilatory support to maintain normocapnia is important for managing ducks anesthetized with halothane. 相似文献
997.
OBJECTIVE: To compare a DNA probe test with two cultivation methods for the detection of Mycobacterium avium subsp paratuberculosis in goat and sheep faeces. DESIGN: Comparison of the results of the three methods with histological examination as the reference standard. PROCEDURE: Faecal specimens were obtained from goats and sheep originating from flocks known to be affected with paratuberculosis and tested for Mycobacterium avium subsp paratuberculosis with a DNA probe test and two cultivation methods (old conventional culture and new double incubation method in Herrold's and Lowenstein-Jensen medium). RESULTS: In goats, the sensitivity of the various tests were for the DNA probe test 17.2%, for the double incubation culture method 25.4% and for the old conventional culture method 22.8% using the histopathological results as reference. In sheep the sensitivity of the various tests were for the DNA probe test 13.2%, for the double incubation culture method 8.8% and for the old conventional culture method 5.9% using the histopathological results as reference. The specificity of the above tests was 100% in goats and sheep and the specificity of the double incubation culture method in goats was 91%. CONCLUSIONS: The DNA probe test is a rapid and specific test that could be used in a control program if the sensitivity of the test were improved and possibly in combination with another test. 相似文献
998.
Seidler T Alter T Krüger M Fehlhaber K 《Berliner und Münchener tier?rztliche Wochenschrift》2001,114(9-10):375-377
On transport and at the abattoir animals are confronted with a lot of stressors, such as sound/noise, crowding/mixing, pollutants and infectious agents that act on the organism. After transport stress an endogenous contamination is often seen in slaughter carcasses and presents a hazard for the consumer. These events are often correlated with a rise in endotoxin level (Misawa et al., 1995; Morales et al., 1992) and a modified immune response. Previous own investigations confirm this hypothesis (Zucker and Krüger, 1998, Seidler et al., 2000). The attempt was made to investigate the impact of selected stressors (short term transport (1 h), long term transport (7-8 hrs), high temperature, high humidity and intense handling/moving) on bacterial translocation, endogenous contamination, endotoxin levels and bactericidal activity of body fluids. 相似文献
999.
1000.
Over a 6-year period seven adult horses of different breeds and genders developed multifocal, exudative, oozing dermatitis characterized histologically by epidermal spongiotic vesicles and perivascular eosinophilic, neutrophilic and mixed mononuclear inflammation. Three horses were pruritic. Systemic disease was not noted. Two horses had a history of recurrent urticaria (hives) and one horse had nodules or welt-type lesions that progressed to exudative, oozing lesions. Interepithelial immunoglobulin (Ig)G was detected by avidin-biotin complex-peroxidase staining, but the pattern of staining was more consistent with epithelial oedema than specific IgG deposition associated with pemphigus. The exudative oozing lesions developed under circumstances suggesting that dermal oedema progressed to intracellular and intercellular epidermal oedema, which in turn progressed to the spongiotic vesicular epidermal lesions. 相似文献