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   132511篇
  免费   7275篇
  国内免费   93篇
林业   5389篇
农学   4269篇
基础科学   831篇
  17039篇
综合类   21492篇
农作物   5394篇
水产渔业   6689篇
畜牧兽医   67993篇
园艺   1800篇
植物保护   8983篇
  2020年   1177篇
  2019年   1375篇
  2018年   2031篇
  2017年   2331篇
  2016年   2098篇
  2015年   1743篇
  2014年   2226篇
  2013年   5296篇
  2012年   4118篇
  2011年   5094篇
  2010年   3245篇
  2009年   3390篇
  2008年   4972篇
  2007年   4669篇
  2006年   4354篇
  2005年   4089篇
  2004年   3852篇
  2003年   3975篇
  2002年   3543篇
  2001年   4150篇
  2000年   4252篇
  1999年   3374篇
  1998年   1474篇
  1997年   1388篇
  1996年   1288篇
  1995年   1529篇
  1994年   1359篇
  1993年   1231篇
  1992年   2586篇
  1991年   2701篇
  1990年   2593篇
  1989年   2615篇
  1988年   2368篇
  1987年   2349篇
  1986年   2428篇
  1985年   2340篇
  1984年   1884篇
  1983年   1678篇
  1982年   1150篇
  1979年   1749篇
  1978年   1397篇
  1977年   1151篇
  1976年   1214篇
  1975年   1293篇
  1974年   1501篇
  1973年   1514篇
  1972年   1405篇
  1971年   1305篇
  1970年   1251篇
  1969年   1283篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
251.
Two cats with chronic eosinophilic skin disease were investigated. The clinical investigation of the skin disease in one cat was limited and inflammatory bowel disease was diagnosed post mortem. A history of weight loss and a palpably thickened bowel in the second cat suggested concurrent gastrointestinal disease. Diagnosis of inflammatory bowel disease was confirmed on biopsy. Treatment with azathioprine and methylprednisolone acetate resolved the signs of gastrointestinal disease, the pruritus and 95% of the skin lesions. The concurrence of eosinophilic papulocrustous dermatitis and eosinophilic bowel disease raises the possibility of their being linked bv a common aetiology or pathophysiology.  相似文献   
252.
Veterinarians commonly predict mature heart scores for yearling and 2-year-old horses to aid clients in assessing a horse's racing potential. Sixty-six thoroughbreds were assessed as a yearlings or 2-year-olds, then re-assessed as a mature horse (over the age of 3). Of these horses, 82% of the yearlings and 87% of the 2-year-olds had a correctly predicted mature heart score within one heart score range (i.e. three points).  相似文献   
253.
254.
255.
1. The significance of fat accumulation during physiological development of layers was studied using White Leghorn x Australorp pullets from 12 weeks of age.

2. Liver fat, carcass fat, liver weight and body weight increased markedly at the onset of sexual maturity.

3. Within the liver, the protein to DNA ratio did not alter significantly during development; glycogen was not consistently depleted by egg production.

4. Liver fat content was significantly correlated with carcass fat, liver weight and DNA concentration, and plasma total lipid and cholesterol, independent of stage of development; with body weight, liver protein, moisture, and protein to DNA ratio, excluding the period prior to commencement of sexual maturation; and with plasma phospholipid during lay.

5. Obesity was a feature of faster growing fowls which matured earlier, consumed more, utilised food less efficiently for egg production and produced fewer saleable eggs.  相似文献   

256.
1. Agonistic interactions were observed over a 24‐week period in Rhode Island Red and in Nigerian local fowl aged 32 weeks or 12 weeks at the start of the experiments.

2. Agonistic interactions were both more numerous and more severe (fights and peck avoidances) in groups of the local breed than in those of Rhode Island Reds.

3. The outcome of severe interactions favoured local males and Rhode Island females in the first experiment and Rhode Island males in the second.

4. Small body and comb size might account for the relatively high number of agonistic interactions and the submissiveness of local females and young males while physical strength or some other breed characteristic might account for the high number of agonistic interactions of local males as well as their dominance in breed encounters.  相似文献   

257.
258.
259.
Two experiments, using the ligated intestinal segment technique, were conducted to determine whether the pituitary hormone prolactin (PRL) could reduce Escherichia coli-induced fluid loss into the small intestine of 2- to 3-week-old pigs. Inoculation of 10(6) to 10(8) enteropathogenic E coli organisms into ligated jejunal segments caused a significant accumulation of luminal fluid within 12 hours. In the first experiment, intraluminal inoculation with 0.5 mg of ovine PRL along with the bacteria did not have any effect on fluid accumulation. Systemic IV treatment of the animals with 1.0 mg of ovine PRL at 3-hour intervals, beginning either immediately after or 9 to 10 hours before intestinal ligation, did not significantly (P less than 0.05) reduce fluid accumulation as compared with control animals. In the second experiment, IM administration of 100 microgram of thyrotropin-releasing hormone (TRH) at 3-hour intervals, beginning 6 hours before intestinal ligation, significantly (P less than 0.05) increased circulating PRL concentrations, as measured by radioimmunoassay. However, TRH treatment did not reduce the accumulation of luminal fluid in E coli-inoculated segments.  相似文献   
260.
Intranuclear cisternal and vesicular structures, bound by a single membrane, were observed for the first time in some glandular "bird's eye" cells of canine circummanal gland carcinomas. The role of these intranuclear structures is not clear. It is suggested that they may be involved in cellular adaptation to an environment of nutrient deficiency, as a result of cell overcrowding.  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