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   363509篇
  免费   28169篇
  国内免费   96篇
  391774篇
  2018年   4266篇
  2017年   4093篇
  2016年   5182篇
  2015年   5066篇
  2014年   6714篇
  2013年   9649篇
  2012年   11257篇
  2011年   12115篇
  2010年   8424篇
  2009年   7414篇
  2008年   10721篇
  2007年   11193篇
  2006年   10722篇
  2005年   9976篇
  2004年   10178篇
  2003年   9799篇
  2002年   9772篇
  2001年   15869篇
  2000年   15754篇
  1999年   12069篇
  1998年   3849篇
  1997年   3794篇
  1996年   3447篇
  1995年   3190篇
  1992年   9562篇
  1991年   9765篇
  1990年   9514篇
  1989年   9519篇
  1988年   8777篇
  1987年   8269篇
  1986年   7551篇
  1985年   7882篇
  1984年   6352篇
  1983年   5348篇
  1982年   3627篇
  1981年   3200篇
  1980年   3148篇
  1979年   6003篇
  1978年   4674篇
  1977年   4244篇
  1976年   4015篇
  1975年   4830篇
  1974年   5341篇
  1973年   5290篇
  1972年   4809篇
  1971年   4510篇
  1970年   3919篇
  1969年   3818篇
  1968年   3577篇
  1967年   3219篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
141.
The infection of Planorbarius banaticus with sporocysts of Cotylurus cornutus is accompanied by an increase in aldolase activity of molluscs' haemolymph of 1.2 fold. In solutions of nitroammofoska (0.1, 1 and 10 mg/1) the activity of this ferment in infected individuals increases much higher than in non-infected ones. This results in fast carbohydrate expenditures by molluscs, intermediate hosts of trematodes, and their death from exhaustion.  相似文献   
142.
Infravesical obstruction in 300 male patients was determined by prostatic sclerosis (PS). PS is a polyetiological disease developing more frequently as a result of prostatitis, autoimmune, allergic and congestive factors. Sclerosis and shriveling of the gland cause topographo-anatomic changes in the infravesical area, well revealed during a combined roentgeno-urological study. Direct signs of PS are the following: stenosis, deformity and shortening of the prostatic part of the urethra, a high position of the lower outline of the bladder resembling braces over the public symphysis; indirect signs: change of the bladder shape, megacyst, trabecular mucosa and diverticulosis, congestion in the upper urinary tracts, uni- or bilateral urethero-hydronephrosis.  相似文献   
143.
The effects of corticotropin-releasing hormone (CRH) injected into the dorsal neostriatum on the open-field and shuttle-box behavior were studied in rats with high (Koltushi high avoidance, KHA) and low (Koltushi low avoidance, KLA) capability for avoidance learning. The effects of this hormone on the behavior of these rat strains were different. In KLA rats with passive strategy of behavior the CRH injection led to a rapid locomotor activation in the open field, while the rats with active behavioral strategy (KHA) reacted to the injection by a significant decrease in locomotion and change for the passive mode of behavior. The same CRH effects on locomotion were obtained in the shuttle-box experiments. Moreover, in the KLA rats the neurohormone injection resulted in an improvement of avoidance learning in contrast to the KHA rats, in which CRH substantially impaired avoidance learning. The obtained evidence is discussed in terms of the important role of striatal CRH in the choice of behavioral strategy in stress.  相似文献   
144.
X-IRRADIATION of mammalian cells in culture yields a survival curve of the threshold type (for review see ref. 1). It isjnter-esting to ask how one can enhance the radiation response by small changes of the physical environment of the cells, as can be done chemically, for example, by incorporation of 5-bromo-deoxyuridine into DNA1,2. Elevation of the temperature is a likely prospect for enhancement of radiosensitivity for the following reasons. It is known that proteins are heat labile and that temperature sensitive mutants of bacteria and phage can be obtained for many different enzymes3 which are operative at 37° C but not at 42° or 43°C. For example4, DNA polymerase is reversibly temperature sensitive; it is rendered inoperative above 42°C, but will be functional again when the temperature is lowered. It is not unreasonable to expect that temperature sensitive mutations for many enzymes occur frequently and that the use of temperatures somewhat higher than the normal range at which the cells grow might disclose sensitivities for specific enzymes in normal cells of higher organisms.  相似文献   
145.
146.
147.
148.
149.
150.
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