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   3616篇
  免费   230篇
  国内免费   3篇
林业   153篇
农学   86篇
基础科学   12篇
  426篇
综合类   776篇
农作物   101篇
水产渔业   288篇
畜牧兽医   1758篇
园艺   82篇
植物保护   167篇
  2023年   34篇
  2022年   46篇
  2021年   68篇
  2020年   87篇
  2019年   104篇
  2018年   90篇
  2017年   78篇
  2016年   83篇
  2015年   66篇
  2014年   89篇
  2013年   152篇
  2012年   156篇
  2011年   248篇
  2010年   122篇
  2009年   89篇
  2008年   172篇
  2007年   142篇
  2006年   148篇
  2005年   124篇
  2004年   146篇
  2003年   123篇
  2002年   101篇
  2001年   58篇
  2000年   71篇
  1999年   53篇
  1998年   23篇
  1997年   27篇
  1996年   26篇
  1995年   24篇
  1994年   42篇
  1993年   58篇
  1992年   56篇
  1991年   60篇
  1990年   58篇
  1989年   56篇
  1988年   50篇
  1987年   41篇
  1986年   55篇
  1985年   40篇
  1984年   31篇
  1983年   28篇
  1981年   31篇
  1979年   38篇
  1978年   23篇
  1975年   25篇
  1973年   26篇
  1972年   30篇
  1971年   38篇
  1970年   26篇
  1969年   30篇
排序方式: 共有3849条查询结果,搜索用时 15 毫秒
151.
152.
An enzyme-linked immunosorbent assay (ELISA) was established for the rapid detection of specific antibodies against the causative agent of border disease in ovine sera. Polyethylene-glycol concentrated, equilibrium density gradient purified bovine virus diarrhea virus was used as test antigen. The optimal amount of antigen was 0.5 microgram/well, and the optimal concentration of conjugate was at 1/4,000 dilution. A total of 20 ovine serum samples, which had been collected from animals with or without border disease, were compared by ELISA and serum neutralization test for the detection of border disease-specific antibodies. ELISA was shown to be equally specific but less time-consuming and easier to perform than serum neutralization test. A positive correlation (r = 0.60) between the two tests was found.  相似文献   
153.
Segmental atresia of the transverse colon was observed at necropsy in a neonatal foal. The dorsal and ventral components of the large colon were fused, and ended blindly. The small colon was collapsed and completely closed at its cranial end. The right and left dorsal and ventral colons were fused into one blind-ended tube. Histologically, eosinophilic intranuclear inclusion bodies demonstrative of Equine Rhinopneumonitis were present in the thymus.  相似文献   
154.
Production of sheep-goat chimeras by inner cell mass transplantation   总被引:3,自引:0,他引:3  
Embryos were surgically flushed from goats and sheep on d 6 and 7, respectively, following the first day of estrus (d 0). After enzymatic removal of the zonae pellucidae, inner cell masses were isolated from caprine blastocysts by immunosurgery. The intact inner cell masses were injected into ovine blastocysts with the aid of a micromanipulator. Twenty-two manipulated blastocysts were surgically transferred into 12 ovine recipients. Nine ewes gave birth to a total of 13 young (59% embryo survival). Ten were classified by serum electrophoretic assays or karyotypes as lambs, one as a kid, and two as interspecific chimeras.  相似文献   
155.
ObjectiveTo review the immune response to anesthesia including mechanical ventilation, inhaled anesthetic gases, and injectable anesthetics and sedatives.Study designReview.Methods and databasesMultiple literature searches were performed using PubMed and Google Scholar from spring 2012 through fall 2013. Relevant anesthetic and immune terms were used to search databases without year published or species constraints. The online database for Veterinary Anaesthesia and Analgesia and the Journal of Veterinary Emergency and Critical Care were searched by issue starting in 2000 for relevant articles.ConclusionRecent research data indicate that commonly used volatile anesthetic agents, such as isoflurane and sevoflurane, may have a protective effect on vital organs. With the lung as the target organ, protection using an appropriate anesthetic protocol may be possible during direct pulmonary insults, including mechanical ventilation, and during systemic disease processes, such as endotoxemia, generalized sepsis, and ischemia-reperfusion injury.  相似文献   
156.
OBJECTIVE: To identify clinical, echocardiographic, and electrocardiographic abnormalities in Boxers with cardiomyopathy and echocardiographic evidence of left ventricular systolic dysfunction. DESIGN: Retrospective study. ANIMALS: 48 mature Boxers. PROCEDURE: Medical records were reviewed for information on age; sex; physical examination findings; and results of electrocardiography, 24-hour ambulatory electrocardiography, thoracic radiography, and echocardiography. RESULTS: Mean age of the dogs was 6 years (range, 1 to 11 years).Twenty (42%) dogs had a systolic murmur, and 9 (19%) had ascites. Congestive heart failure was diagnosed in 24 (50%) dogs. Seventeen (35%) dogs had a history of syncope. Mean fractional shortening was 14.4% (range, 1% to 23%). Mean left ventricular systolic and diastolic diameters were 4.5 cm (range, 3 to 6.3 cm) and 5.3 cm (range, 3.9 to 7.4 cm), respectively. Twenty-eight (58%) dogs had a sinus rhythm with ventricular premature complexes (VPCs), and 20 had supraventricular arrhythmias (15 with atrial fibrillation and 5 with sinus rhythm and atrial premature complexes). Sixteen of the dogs with supraventricular arrhythmias also had occasional VPCs. Morphology of the VPCs seen on lead II ECGs was consistent with left bundle branch block in 25 dogs, right bundle branch block in 8, and both in 11. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that Boxers with cardiomyopathy and left ventricular dysfunction frequently have arrhythmias of supraventricular or ventricular origin. Whether ventricular dysfunction was preceded by electrical disturbances could not be determined from these data, and the natural history of myocardial disease in Boxers requires further study.  相似文献   
157.
158.
159.
160.
Levels of aggression, activity and performance were determined in 270 pigs (initial wt 29.8 kg) injected with amperozide (1.0 mg/kg i.m.), azaperone (2.2 mg/kg i.m.) or saline (.1 ml/kg i.m.) immediately prior to mixing. Pigs had ad libitum access to feed in pens of 15, and six pens were allotted to each treatment. Each pen was video-taped for 48 h after injection. Aggression was determined by continuous observation and summarized for each 2-h period. Injuries on the ears and shoulders of each pig were scored prior to injection and 1, 2, 3 and 7 d after treatment. Eating, drinking and lying were determined by scan sampling at 2-min intervals and summarized for each 2-h period. Weight gain, feed consumption and efficiency were determined for periods ending on d 3, 7, 14, 28, 42, 56, 70 and 84. Both drugs reduced total fighting from 309.8 min for saline to 190.7 and 189.6 min for amperozide- and azaperone-treated pens, respectively (P less than .01). Treatment differences in aggression and lying were evident during the initial 6 h only. Amperozide resulted in fewer fights involving two pigs (197.3/pen) than did azaperone (260.2/pen) or saline (298.3/pen) (P less than .05). Injuries to the ears (P less than .01) and total injuries (P less than .05) were less severe in amperozide-treated pigs than in pigs on the other treatments.(ABSTRACT TRUNCATED AT 250 WORDS)  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