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   50942篇
  免费   2789篇
  国内免费   33篇
林业   2622篇
农学   1538篇
基础科学   220篇
  5747篇
综合类   10156篇
农作物   1960篇
水产渔业   2355篇
畜牧兽医   25474篇
园艺   560篇
植物保护   3132篇
  2019年   450篇
  2018年   737篇
  2017年   790篇
  2016年   688篇
  2015年   640篇
  2014年   772篇
  2013年   1760篇
  2012年   1488篇
  2011年   1668篇
  2010年   1079篇
  2009年   1161篇
  2008年   1635篇
  2007年   1649篇
  2006年   1537篇
  2005年   1466篇
  2004年   1378篇
  2003年   1345篇
  2002年   1281篇
  2001年   1529篇
  2000年   1485篇
  1999年   1218篇
  1998年   456篇
  1997年   474篇
  1996年   470篇
  1995年   523篇
  1994年   470篇
  1993年   483篇
  1992年   926篇
  1991年   921篇
  1990年   911篇
  1989年   919篇
  1988年   869篇
  1987年   902篇
  1986年   890篇
  1985年   897篇
  1984年   723篇
  1983年   652篇
  1979年   647篇
  1978年   540篇
  1977年   459篇
  1976年   463篇
  1975年   503篇
  1974年   691篇
  1973年   605篇
  1972年   675篇
  1971年   673篇
  1970年   598篇
  1969年   591篇
  1968年   451篇
  1967年   511篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
321.
322.
A study was undertaken to determine the efficacy of the novel avermectin, doramectin, against experimental larval and adult infections of three species of nematode parasite important to cattle production in New Zealand. Eighteen worm-free dairy bull beef calves were randomly allocated on live weight to three similar treatment groups. Each calf was given 30,000 Ostertagia ostertagi, 20,000 Cooperia spp. and 10,000 Trichostrongylus axei infective larvae as a single dose. One group was treated with doramectin 6 days after infection while the remaining groups received saline or doramectin 27 days after infection. Given as a single subcutaneous injection behind the ear, doramectin at 200 microg/kg removed 99.9-100% of adult and larval stages of O. ostertagi, Cooperia spp. and T. axei when compared to infections established in untreated controls (p<0.001). No adverse reactions were observed following treatment in the doramectin-treated animals. No injection site lesions were found by palpation following treatment or by injection site examination at necropsy.  相似文献   
323.
324.
325.
326.
1. Semen of White Leghorn and Rhode Island Red males was stored for 24 h in diluents hypertonic (460 mOsm/kg H2O) and isotonic (340 mOsm/kg H2O) to cock seminal plasma.

2. Compared with the fertility results with semen that had been stored in the hypertonic diluent or was fresh, the fertility of the White Leghorns was not affected after storage in the isotonic diluent; a decrease (P < 0.lb05) was observed, however, using Rhode Island Red semen and isotonic diluent.

3. Fresh RIR semen contained 2.lb31% “neck‐bent spermatozoa” (NBS) which was increased to 4.lb23% and 5.lb76% after dilution in hypertonic and isotonic diluents respectively and stored for 24 h. It is doubtful whether this increase (P < 0.lb05) is the sole reason for the lowered fertility obtained with this breed after storage in the isotonic diluent.  相似文献   

327.
1. Treatment of rapeseed meal with calcium hydroxide suspension decreased the sinapine content by up to 90%. Smaller decreases were obtained by autolysis, steaming and treatment with ammonia.

2. When this treated meal was fed to susceptible ("tainting") hens the concentration of trimethylamine in the eggs was decreased to much less than that required to cause taint.  相似文献   

328.
329.
A 10-month-old male domestic short-haired cat was examined because of progressive lameness, a broad face with depressed nasal bridge, small ears, corneal clouding, and multiple bone dysplasia. The cat excreted excessive amounts of glycosaminoglycan (a component of connective tissue) in its urine and had evidence of lysosomal storage of glycosaminoglycans in fibroblasts and neurons. Activity of alpha-L-iduronidase, a lysosomal enzyme involved in glycosaminoglycan degradation, was deficient in cultured fibroblasts and leukocytes. The mucopolysaccharidosis was distinct from that seen in Siamese cats in terms of the pathologic changes and the specific enzyme deficiency.  相似文献   
330.
An 11-month-old male Miniature Poodle was found to regurgitate small volumes of fluid and food particles due to a diverticulum in the thoracic oesophagus. The diverticulum was removed surgically. Histologically the wall contained extensive scar tissue. Longterm recovery was uneventful and 5 months after surgery the dog is in good health  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