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   1542篇
  免费   144篇
林业   68篇
农学   28篇
基础科学   6篇
  236篇
综合类   199篇
农作物   41篇
水产渔业   80篇
畜牧兽医   900篇
园艺   47篇
植物保护   81篇
  2024年   5篇
  2023年   29篇
  2022年   38篇
  2021年   69篇
  2020年   57篇
  2019年   66篇
  2018年   56篇
  2017年   62篇
  2016年   40篇
  2015年   47篇
  2014年   61篇
  2013年   75篇
  2012年   128篇
  2011年   159篇
  2010年   77篇
  2009年   63篇
  2008年   102篇
  2007年   82篇
  2006年   88篇
  2005年   55篇
  2004年   56篇
  2003年   52篇
  2002年   32篇
  2001年   12篇
  2000年   9篇
  1999年   13篇
  1998年   7篇
  1997年   8篇
  1996年   5篇
  1995年   5篇
  1993年   3篇
  1992年   7篇
  1991年   13篇
  1990年   8篇
  1989年   11篇
  1988年   5篇
  1987年   4篇
  1986年   3篇
  1985年   6篇
  1984年   4篇
  1983年   5篇
  1981年   3篇
  1980年   6篇
  1979年   5篇
  1978年   4篇
  1977年   4篇
  1973年   4篇
  1970年   3篇
  1930年   2篇
  1928年   3篇
排序方式: 共有1686条查询结果,搜索用时 31 毫秒
1.
Abnormally high or low blood glucose and insulin concentrations after standardized glucose tolerance tests can reflect disorders such as pituitary dysfunction, polysaccharide storage myopathies, and other clinical disorders. Glucose and insulin responses, however, are modified by the diet to which the animal has adapted, time since it was last fed, and what it was fed. Body fat (obesity), fitness level, physiologic status, and stress also alter glucose and insulin metabolism. Therefore, it is important to consider these factors when evaluating glucose and insulin tests, especially if only one sample it taken. This article describes the factors affecting glucose and insulin metabolism in horses and how they might influence the interpretation of standardized tests of glucose tolerance.  相似文献   
2.
优化蛋白质营养不再仅仅是对日粮进行大致的氨基酸平衡。蛋白质的形式对猪的健康和生长会产生长远的影响。  蛋白质摄入量是生长猪营养中的一个基本要素。要提高瘦肉生长率,就需要平衡良好的氨基酸以供蛋白质合成之用,这些氨基酸需要以一定的形式通过日粮来提供。现在能够对饲料进行精确的分析,并且有来源可靠的合成氨基酸,已经为猪的蛋白质营养提供了坚实的基础。然而,有时候这会导致过量氮的排泄,因为并非提供的所有的蛋白质都会被猪吸收。过量氮的排出,不但会造成浪费,而且还会对环境造成污染。近年来,新的证据表明,单独提供氨基酸可能…  相似文献   
3.
4.
A one month old Quarterhorse colt was presented after a week history of bilateral nasal discharge and respiratory difficulty. The cervical esophagus was greatly dilated, tortuous and filled with diluted milk. A nasogastric tube could not be passed beyond the base of the heart. An aspiration pneumonia was found at postmortem examination and the esophageal segment from the pharynx to the base of the heart was dilated, thin-walled, had degenerative muscular changes, and a reduction in size and number of ganglion cells of the myenteric plexus. Muscular hypertrophy of the terminal esophagus had reduced its lumen size. Some similarities and disparities of this condition to achalasia of man and megaesophagus of dogs are discussed.  相似文献   
5.
Lymphosarcoma in a six year old male Doberman pinscher was accompanied by hypercalcemia, generalized osteolysis and renal calcification. Tumor involvement of bone marrow was extensive. The possible pathogenesis of hypercalcemia was thought to be the result of a locally active bone-resorbing factor secreted by the tumor cells.  相似文献   
6.
Peptidases have been implicated in the pathogenicity of fungi that cause disease in plants. Expression of the secreted aspartic peptidase gene (gcsap), of a Glomerella cingulata isolate pathogenic on apples, is induced during appressorium formation. To determine whether the secreted aspartic peptidase (GcSAP) is essential to pathogenicity, gcsap was disrupted using a vector containing a 637 bp fragment of genomic DNA that encodes the sequence spanning the two active site aspartic acid (Asp) residues. To ensure that the truncated gcsap gene products could not have residual peptidase activity the codons for the active site residues Asp112 and Asp297 were both mutated to histidine residues. Both PCR and Southern analysis confirmed disruption of gcsap. Neither gcsap mRNA nor GcSAP activity was detected in the disruption mutant. Pathogenicity tests on fruit from three apple cultivars showed that GcSAP was not required for pathogenicity. The disruption mutant grew on medium containing protein as the sole source of nitrogen because G. cingulata secretes a previously undetected peptidase(s). A serine peptidase that had a pH optimum between pH 7.0 and 8.0 and a K m of 0.25 mM for the synthetic substrate succinyl-Ala–Ala–Pro–Phe-p-nitroanilide was identified.  相似文献   
7.
8.
Tropical Animal Health and Production - Serological studies have characterized the presence of the bovine viral diarrhea virus (BVDV) infection in water buffalo herds worldwide. However, the...  相似文献   
9.
10.
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