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   163822篇
  免费   8583篇
  国内免费   142篇
林业   6946篇
农学   4636篇
基础科学   1089篇
  18290篇
综合类   32592篇
农作物   6503篇
水产渔业   7253篇
畜牧兽医   83886篇
园艺   1891篇
植物保护   9461篇
  2018年   1993篇
  2017年   2235篇
  2016年   2056篇
  2015年   1762篇
  2014年   2181篇
  2013年   5875篇
  2012年   4138篇
  2011年   5094篇
  2010年   3307篇
  2009年   3359篇
  2008年   5115篇
  2007年   4729篇
  2006年   4525篇
  2005年   4246篇
  2004年   4280篇
  2003年   4284篇
  2002年   4049篇
  2001年   4972篇
  2000年   4972篇
  1999年   3754篇
  1998年   1590篇
  1997年   1595篇
  1995年   1854篇
  1994年   1665篇
  1993年   1682篇
  1992年   3384篇
  1991年   3733篇
  1990年   3624篇
  1989年   3614篇
  1988年   3276篇
  1987年   3395篇
  1986年   3564篇
  1985年   3474篇
  1984年   2747篇
  1983年   2509篇
  1982年   1675篇
  1981年   1630篇
  1979年   2584篇
  1978年   2045篇
  1977年   1709篇
  1976年   1618篇
  1975年   1730篇
  1974年   2277篇
  1973年   2325篇
  1972年   2303篇
  1971年   2211篇
  1970年   2103篇
  1969年   1930篇
  1968年   1606篇
  1967年   1720篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
Quantitative and qualitative bacterial assays were performed on the skin of three dogs with endocrine-related primary metabolic seborrhea. After the dogs were treated (thyroid supplementation or castration, bacterial analyses were again performed on the same sites. Before therapy, the dogs had a cutaneous flora composed mainly of Staphylococcus aureus coagulase-positive organisms. After therapy, there was a significantly lower bacterial count, and two of the dogs had floras consisting mainly of coagulase-negative cocci. During the study, the two dogs that reverted bacteriologically to a normal cutaneous microenvironment became normal dermatologically. The third dog improved, but continued to have minor signs of seborrhea.  相似文献   
992.
Silicified anthoecia (fertile le'mmas and paleas) of grasses (Berriochloa communis, Berriochloa primaeva, and Berriohldoa cf. nova) were found in, the oral cavity and rib cage articulated skeletons of Teleoceras major buried in late Clarendonian volcanic ash in. Nebraska The plant fossils, thought to be food residues, help clarify, the enigmatic paleobiological role, of Teleocears, which had hippotamus-like porportions but very high-crowned teeth. Telecoceras was probably amphbious, but siliceous grasses formed a significant portion of its diet.  相似文献   
993.
994.
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   
995.
Blood from calves infected with Theileria annulata and T parva was freed from host cell elements and the piroplasms liberated from the red cells by ammonium chloride lysis. Lysates of the purified piroplasms and control host cell material were examined electrophoretically for several enzymes. Zymograms stained for glucose phosphate isomerase showed distinct differences between the host cell enzyme pattern and parasite enzyme patterns. The isoenzyme pattern of T annulata piroplasms differed from the isoenzyme pattern of T parva piroplasms.  相似文献   
996.
While both Brucella abortus and Yersinia enterocolitica IX have O antigens in common, they differ significantly with respect to motility. Thus Br abortus is always non-motile while Y enterocolitica is motile when grown at room temperature. The presence of yersinia H agglutinins in serum can be shown to be evidence of previous exposure to Y enterocolitica. These agglutinins are not generated by brucella infection. A rapid H agglutination test will serve to provide this differentiation without interference from cross-reacting O antigens.  相似文献   
997.
Two strains of bovine Theileria from northern Nigeria were shown to be identical to Theileria mutans in the indirect immunofluorescent antibody test. One of the strains was transmitted by the tick Amblyomma variegatum; large macroschizonts, typical for T mutans, could be demonstrated in infected cattle. It is concluded from these experiments and from the literature that there is reliable evidence so far for the occurrence in Nigeria of only two bovine Tehileria species, T mutans and T velifera.  相似文献   
998.
999.
1000.
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