全文获取类型
收费全文 | 7746篇 |
免费 | 347篇 |
国内免费 | 6篇 |
专业分类
林业 | 504篇 |
农学 | 156篇 |
基础科学 | 38篇 |
1393篇 | |
综合类 | 1664篇 |
农作物 | 237篇 |
水产渔业 | 609篇 |
畜牧兽医 | 2769篇 |
园艺 | 201篇 |
植物保护 | 528篇 |
出版年
2023年 | 59篇 |
2022年 | 77篇 |
2021年 | 151篇 |
2020年 | 155篇 |
2019年 | 183篇 |
2018年 | 182篇 |
2017年 | 156篇 |
2016年 | 186篇 |
2015年 | 166篇 |
2014年 | 195篇 |
2013年 | 281篇 |
2012年 | 503篇 |
2011年 | 637篇 |
2010年 | 310篇 |
2009年 | 249篇 |
2008年 | 546篇 |
2007年 | 563篇 |
2006年 | 503篇 |
2005年 | 496篇 |
2004年 | 468篇 |
2003年 | 430篇 |
2002年 | 439篇 |
2001年 | 109篇 |
2000年 | 88篇 |
1999年 | 78篇 |
1998年 | 64篇 |
1997年 | 55篇 |
1996年 | 48篇 |
1995年 | 53篇 |
1994年 | 50篇 |
1993年 | 47篇 |
1992年 | 32篇 |
1991年 | 36篇 |
1990年 | 37篇 |
1989年 | 37篇 |
1988年 | 33篇 |
1987年 | 29篇 |
1986年 | 26篇 |
1985年 | 42篇 |
1984年 | 29篇 |
1983年 | 28篇 |
1982年 | 22篇 |
1981年 | 16篇 |
1980年 | 25篇 |
1979年 | 26篇 |
1978年 | 17篇 |
1977年 | 17篇 |
1976年 | 13篇 |
1974年 | 13篇 |
1973年 | 17篇 |
排序方式: 共有8099条查询结果,搜索用时 0 毫秒
61.
Effects of postoperative rehabilitation on limb function after cranial cruciate ligament repair in dogs 总被引:1,自引:0,他引:1
Marsolais GS Dvorak G Conzemius MG 《Journal of the American Veterinary Medical Association》2002,220(9):1325-1330
OBJECTIVE: To determine the effects of early postoperative rehabilitation on limb function in dogs after surgery for ruptured cranial cruciate ligament (RCCL). DESIGN: Prospective clinical study. ANIMALS: 51 client-owned dogs. PROCEDURE: Dogs weighing between 20 and 40 kg (44 to 88 lb) that had RCCL and medial meniscal injury were studied. After removal of the RCCL and complete medial meniscectomy, the stifle joint was stabilized by use of a lateral retinacular stabilization technique. Twenty-five dogs were included in a postoperative rehabilitation group, and 26 dogs were included in an exercise-restricted group. Limb function (peak vertical force [PVF] and vertical impulse [VI]) was determined before surgery and 6 months after surgery, using force platform gait analysis. RESULTS: Prior to surgery, mean PVF and VI in affected limbs were similar between groups. Six months after surgery, PVF and VI were significantly increased in dogs of both groups. However, PVF and VI in dogs in the rehabilitation group were significantly greater than those of dogs in the exercise-restricted group. At this time, differences in limb function (as measured by PVF and VI) between the repaired and normal limbs were not evident in dogs in the rehabilitation group. Conversely, limb function in the repaired limb of dogs in the exercise-restricted group was still significantly less than that of the normal limb. CONCLUSION AND CLINICAL RELEVANCE: Dogs that have surgery for RCCL and a torn medial meniscus benefit from postoperative rehabilitation; rehabilitation should be considered part of the postoperative management of these patients. 相似文献
62.
MJ Soares D Chakraborty SJ Renaud K Kubota P Bu T Konno MA Rumi 《The Journal of reproduction and development》2012,58(3):283-287
Hemochorial placentation is characterized by trophoblast-directed uterine spiral artery remodeling. The rat and human both possess hemochorial placentation and exhibit remarkable similarities regarding the depth of trophoblast invasion and the extent of uterine vascular modification. In vitro and in vivo research methodologies have been established using the rat as an animal model to investigate the extravillous/invasive trophoblast lineage. With these research approaches, two signaling pathways controlling the differentiation and invasion of the trophoblast cell lineage have been identified: i) hypoxia/hypoxia inducible factor and ii) phosphatidylinositol 3-kinase/AKT/Fos like antigen 1. Dissection of these pathways has facilitated identification of fundamental regulators of the invasive trophoblast cell lineage. 相似文献
63.
Regina Campbell-Malone Susan G Barco Pierre-Yves Daoust Amy R Knowlton William A McLellan David S Rotstein Michael J Moore 《Journal of zoo and wildlife medicine》2008,39(1):37-55
Vessel-whale collision events represented the ultimate cause of death for 21 (52.5%) of the 40 North Atlantic right whales (Eubalaena glacialis) necropsied between 1970 and December 2006. Injuries seen in vessel-struck whales fall into two distinct categories: 1) sharp trauma, often resulting from contact with the propeller, and 2) blunt trauma, presumably resulting from contact with a vessel's hull. This study analyzes four trauma cases that resulted from vessel-whale collisions, which together provide a framework for a more critical understanding of lethal blunt and sharp trauma resulting from vessel collisions with right whales. In case no. 1, contact with a propeller resulted in three deep lacerations. The animal survived acute trauma only to succumb nearly 14 years later when the lesions reopened and became infected. In case no. 2, anecdotal reports linked the laceration of large arteries of the peduncle and histologic evidence of perimortem trauma at a bone fracture site to vessel-whale collision trauma. Case no. 3 had a laceration of the oral rete and a fracture of the rostrum. Both of the areas displayed histologic evidence of perimortem blunt trauma. Finally, in case no. 4, an antemortem mandibular fracture, two additional skull fractures, and widespread hemorrhage were consistent with severe blunt trauma. Evidence from each case, including the timing of trauma relative to the time of death and identifying characteristics of both trauma types, are presented. Before this study, no detailed comparative analysis of trauma pathology that resulted from lethal interactions between vessels and right whales had been conducted. This study demonstrates the importance of detailed gross and histologic examination in determining the significance and timing of traumatic events. This work represents a new paradigm for the differential diagnosis of lethal sharp and blunt trauma in right whales hit by ships and will enhance the present understanding of the impact of anthropogenic mortality on this critically endangered species. 相似文献
64.
65.
Monde Mapekula Michael Chimonyo Cletos Mapiye Kennedy Dzama 《Tropical animal health and production》2010,42(7):1413-1419
Understanding the utilisation patterns of milk assists in designing appropriate dairy development schemes in rural communities.
The objective of the study was to determine milk utilisation patterns in different smallholder farming systems in the Eastern
Cape Province of South Africa. Data were collected through the administration of recording sheets to 130 randomly selected
households in Alice, Fort Beaufort and Queenstown districts. Amounts of milk produced per household ranged from 9 to 21 l
per household per day. Milk consumption/household/day was similar among the three districts. Milk consumption in the early
lactation doubled the amount consumed in late lactation (P < 0.05). Milk in the communal areas was largely utilised as fresh or sour milk. Fresh milk was mostly used in tea/coffee
or to make porridge for children. Sour milk was consumed with thick boiled maize meal. Fort Beaufort (10.2 ± 1.37 l/day) had
the highest sour milk sales whilst Queenstown had the highest fresh milk sales (9.7 ± 5.57 l/day). It was concluded that quantities
of milk consumed or sold as fresh or sour were generally low and varied across smallholder farming systems. 相似文献
66.
Michael Coad Derek Clifford Shelley G. Rhodes R. Glyn Hewinson H. Martin Vordermeier Adam O. Whelan 《Veterinary research》2010,41(2)
The principal surveillance tool used to control bovine tuberculosis in cattle is the removal of animals that provide a positive response to the tuberculin skin-test. In this study we performed a longitudinal investigation of the immunological and diagnostic consequences of repeated short-interval skin-tests in cattle naturally infected with Mycobacterium bovis. Tuberculin skin-test positive cattle were subjected to up to four further intradermal comparative cervical skin-tests at approximately 60-day intervals. A significant progressive reduction in the strength of the skin-test was observed after successive tests. In contrast, the magnitude of interferon-γ (IFN-γ) responses was not influenced by repeat skin-testing either transiently around the time of each skin-test or longitudinally following repeated tests. A significant boost in blood interleukin-10 (IL-10) production was observed within 3 days following each skin-test although the magnitude of this boosted response returned to lower levels by day 10 post-test. The application of a novel multiplex assay to simultaneously measure seven cytokines and chemokines also identified that skin-testing resulted in a significant and progressive reduction in antigen specific interleukin-1β (IL-1β) whilst confirming stable IFN-γ and elevated IL-10 responses in the blood. Therefore, we have demonstrated that in cattle naturally infected with M. bovis, repeat short-interval skin-testing can lead to a progressive reduction in skin-test responsiveness which has potential negative consequences for the detection of infected animals with marginal or inconclusive skin-test responses. The desensitising effect is associated with decreased IL-1β and elevated IL-10 responses, but importantly, does not influence antigen specific IFN-γ responses. 相似文献
67.
68.
Richards JR Elston TH Ford RB Gaskell RM Hartmann K Hurley KF Lappin MR Levy JK Rodan I Scherk M Schultz RD Sparkes AH 《Journal of the American Veterinary Medical Association》2006,229(9):1405-1441
Vaccination is a medical procedure, and the decision to vaccinate should be based on a risk-based assessment for each cat and each vaccine. 相似文献
69.
Moeller EM Steiner JM Williams DA Tetrick M Burr J 《American journal of veterinary research》2006,67(7):1110-1114
OBJECTIVE: To determine an optimal dose of carbon 13 ((13)C)-labeled aminopyrine for use in a (13)C-aminopyrine demethylation blood test in healthy dogs. ANIMALS: 9 adult dogs. PROCEDURES: Food was withheld from each dog for 12 hours. A 2-mL baseline blood sample was obtained from each dog and placed into an evacuated tube containing sodium heparin. Carbon 13-labeled aminopyrine was administered IV at doses of 1, 2, 5, or 10 mg/kg. Additional blood samples (2 mL) were obtained and placed into evacuated tubes containing sodium heparin 30, 45, 60, and 75 minutes after (13)C-aminopyrine administration. Hydrochloric acid was used to extract CO(2) from blood samples. The extracted gas was analyzed by fractional mass spectrometry to determine the percentage dose of (13)C administered as (13)C-aminopyrine and recovered in extracted gas (PCD). RESULTS: Gross evidence of clinical adverse effects was not detected in any dog after administration of (13)C-aminopyrine. The mean coefficient of variation (CV) for PCD was significantly lower than the mean CV for the summation of PCD values up to a given sampling time (CUMPCD). Mean PCD values among the 4 doses for each sample time were not significantly different. Administration of (13)C-aminopyrine at a dose of 2 mg/kg resulted in the lowest interindividual variability. CONCLUSIONS AND CLINICAL RELEVANCE: The PCD is superior to CUMPCD for the quantification of aminopyrine demethylation. Administration of (13)C-(13)C-aminopyrine at a dose of 2 mg/kg is appropriate for use in the (13)C-aminopyrine demethylation blood test in healthy dogs. 相似文献
70.
OBJECTIVE: To describe a technique for laparoscopic-assisted removal of cystic calculi in geldings and report outcome. STUDY DESIGN: Clinical report. ANIMALS: Four geldings with cystic calculi. METHODS: Laparoscopic-assisted cystotomy and urolith retrieval was performed in 4 anesthetized geldings positioned in dorsal recumbency. With a laparoscope portal located at the umbilicus, the abdomen was insufflated and then the surgical table was tilted (30 degrees head-down position) before an instrumental portal was created parallel and 2-3 cm medial to the left external inguinal ring. Laparoscopic grasping forceps were inserted to grasp the cranial aspect of the bladder and elevate it to the ventral abdominal wall. With the instrumental portal as mid-point, the parainguinal skin incision was longitudinally extended cranial and caudal (approximately 8-10 cm) to accommodate the size of the urolith. The apex of the bladder was exteriorized and sharply incised, the urolith extracted, and after cystotomy closure, the bladder was repositioned. The mini-laparotomy and trocar incisions were closed in layers. RESULTS: There were no intra- or post-operative complications. All horses had minor incisional swelling for 3-4 days. No signs of abdominal or incisional pain were observed. Hematuria and slight stranguria occurred until the 3rd or 4th day. Surgical time (skin incision to skin closure) was 35-40 minutes. On long-term follow-up (up to 12 months) no recurrence of clinical signs associated with cystic calculi occurred. CONCLUSION: Uroliths (6-8 cm diameter) can be removed by laparoscopic-assisted cystotomy in geldings. CLINICAL RELEVANCE: Laparoscopic-assisted cystotomy combines the advantages of the parainguinal laparocystotomy with laparoscopic technique for removal of cystic calculi while avoiding their disadvantages. 相似文献