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   124628篇
  免费   5522篇
  国内免费   52篇
林业   8100篇
农学   4427篇
基础科学   873篇
  15700篇
综合类   22183篇
农作物   6447篇
水产渔业   6472篇
畜牧兽医   55632篇
园艺   2207篇
植物保护   8161篇
  2018年   4164篇
  2017年   4273篇
  2016年   2548篇
  2015年   1171篇
  2014年   1274篇
  2013年   3935篇
  2012年   3437篇
  2011年   5595篇
  2010年   4569篇
  2009年   3761篇
  2008年   4825篇
  2007年   5012篇
  2006年   2826篇
  2005年   2756篇
  2004年   2852篇
  2003年   2869篇
  2002年   2703篇
  2001年   3279篇
  2000年   3343篇
  1999年   2440篇
  1998年   1070篇
  1997年   1081篇
  1995年   1252篇
  1994年   1164篇
  1993年   1138篇
  1992年   2396篇
  1991年   2530篇
  1990年   2439篇
  1989年   2511篇
  1988年   2291篇
  1987年   2351篇
  1986年   2484篇
  1985年   2394篇
  1984年   1918篇
  1983年   1773篇
  1982年   1165篇
  1981年   1123篇
  1980年   1025篇
  1979年   1764篇
  1978年   1424篇
  1977年   1163篇
  1976年   1130篇
  1975年   1165篇
  1974年   1524篇
  1973年   1610篇
  1972年   1585篇
  1971年   1516篇
  1970年   1408篇
  1969年   1265篇
  1967年   1102篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
971.
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   
972.
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   
973.
974.
975.
Absorption of endotoxin from the gastrointestinal tract was evaluated in hay-fed and lactic acidotic sheep duodenally infused with 10 mg of Escherichia coli endotoxin, and in lactic acidotic sheep not infused. The effect of abomasal fluid on biological activity of endotoxin was also evaluated. Leukopenia was the criterion used for detecting endotoxemia. Absorption of endotoxin from the gastrointestinal tract was not detected in either hay-fed or lactic acidotic sheep. Endotoxin appeared to maintain its activity after incubation with abomasal fluid, and the presence of endogenous endotoxin in abomasal contents was indicated. The results indicate that endotoxin of alimentary origin may not be involved in the lactic acidosis syndrome in ruminants.  相似文献   
976.
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   
977.
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   
978.
The minimal infectious dose of the H52 strain of infectious bronchitis virus for organ cultures of oviduct and kidney was compared in chickens of different ages. Organ cultures of oviduct were found to be highly susceptible to infection regardless of the age of chicken and no difference in susceptibility could be demonstrated between cultures of the magnum and uterus regions of the mature oviduct. Kidney organ cultures were less susceptible and resistance to infection increased significantly (P less than 0.001) with the age of the chicken from which cultures were prepared.  相似文献   
979.
980.
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