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   81371篇
  免费   4434篇
  国内免费   1951篇
林业   4743篇
农学   4171篇
基础科学   1468篇
  9435篇
综合类   17690篇
农作物   3643篇
水产渔业   3752篇
畜牧兽医   36164篇
园艺   1690篇
植物保护   5000篇
  2022年   801篇
  2021年   1145篇
  2020年   1146篇
  2019年   1264篇
  2018年   1435篇
  2017年   1738篇
  2016年   1495篇
  2015年   1686篇
  2014年   1760篇
  2013年   3702篇
  2012年   3192篇
  2011年   3572篇
  2010年   2711篇
  2009年   2582篇
  2008年   3230篇
  2007年   3068篇
  2006年   2872篇
  2005年   2515篇
  2004年   1977篇
  2003年   1948篇
  2002年   1862篇
  2001年   2160篇
  2000年   2159篇
  1999年   1887篇
  1998年   954篇
  1997年   899篇
  1996年   824篇
  1995年   901篇
  1994年   840篇
  1993年   803篇
  1992年   1414篇
  1991年   1522篇
  1990年   1401篇
  1989年   1396篇
  1988年   1260篇
  1987年   1213篇
  1986年   1240篇
  1985年   1222篇
  1984年   988篇
  1983年   920篇
  1979年   901篇
  1978年   703篇
  1976年   711篇
  1975年   714篇
  1974年   873篇
  1973年   844篇
  1972年   813篇
  1971年   727篇
  1970年   771篇
  1969年   734篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
151.
152.
153.
154.
A 4-year-old female donkey residing in an open field in Indiana was admitted for evaluation of facial lesions of 2 years duration. Cytologic and histologic examination of exudate and tissue from the lesions revealed a pyogranulomatous inflammatory reaction with numerous yeasts. Sporothrix schenckii was suspected to be the infectious agent; however, multiple culture attempts did not provide positive identification of the organism. Serologic examination supported infection with S. schenckii. A specific direct immunofluorescent antibody test performed on paraffin-embedded tissue sections confirmed the organism as S. schenckii. Clinical signs resolved after appropriate iodide therapy.  相似文献   
155.
1. Coir dust was evaluated as broiler litter in comparison with sawdust and rice husk using 135 commercial broilers. Forty-five broiler chicks were reared to 42 d on a 50 mm layer of each of these litters. 2. Birds reared on coir dust showed no difference in food consumption, body weight gain, food conversion efficiency production number and survivability in comparison to those reared on saw dust and rice husk. 3. It was concluded that coir dust is suitable as broiler litter when cheaply available.  相似文献   
156.
This paper provides a working framework for enhancing the well-being of senior pet dogs and cats. Approaches to screening the medical status of senior pets are described in detail, with particular emphasis on establishing baseline data in healthy animals, the testing of clinically ill animals, and assessing senior pets prior to anesthesia and surgery. The management of pain and distress and the application of hospice and palliative care are addressed. Advice on ways to approach euthanasia and dealing with end-of-life issues is also provided.  相似文献   
157.
158.
159.
OBJECTIVE: To objectively evaluate the effect of transecting the tendon of the biceps brachii muscle (BBT), tendon of the infraspinatus muscle (IFS), or medial glenohumeral ligament (MGHL) on shoulder joint stability in canine cadavers. SAMPLE POPULATION: 81 forelimbs from mature dogs. PROCEDURE: Cadaver forelimbs were placed in a testing frame and axially preloaded with 4 kg of weight. Shoulder joint stability was tested in neutral joint position, flexion, and extension before and after transection of the BBT (n = 37), IFS (37), or MGHL (7). Humeral translation relative to the glenoid was induced by applying a 3-kg load in each of 3 directions (cranial, lateral, and medial) and quantitatively measured by use of an electromagnetic motion tracking system. Peak translational data were compared in each joint position before and after transection of the BBT, IFS, or MGHL. RESULTS: When tested in neutral position, the cranial, lateral, and medial translation of the humerus was significantly increased after BBT transection. In the flexed position, translation of the humerus in the cranial and lateral directions was significantly increased after BBT transection. In the extended position, the medial translation of the humerus was significantly increased after BBT transection. Complete medial luxation of all humeral heads occurred following transection of the MGHL. CONCLUSIONS AND CLINICAL RELEVANCE: The BBT contributes to passive shoulder joint stability in dogs, particularly in the neutral and flexed positions. It also provides medial stability during shoulder joint extension. Complete luxation of the joint occurs when the MGHL is transected.  相似文献   
160.
The thalamic nuclei with their defined set of input-output connections are the primary channel for information flow to the cerebral cortex. Several data suggest that neurons of that area are involved in the response to various aversive stimulations. However the pattern of activation seems to depend on the stress model as well as the stage of maturation. In the present study we would like to check which nuclei of the thalamus show expression of c-fos in the response to the "open field test", and how this response pattern changes during the maturation process. 30 rats of age ranged from P0 to P120 (P-postnatal day) were studied. The experimental group was exposed to the "open field test" for 10 minutes. After perfusion and fixation, brains were cut and stained for c-fos with immunohistochemical method. Our results showed that during development the pattern of c-fos activity in the thalamic nuclei after stress stimulation undergoes significant changes. Distinct c-fos expression was observed in the paraventricular nucleus, intergeniculate leaflet and ventral lateral geniculate nucleus. These findings suggest that these nuclei may play a direct role in the stress reaction involved in the response to the "open field test".  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