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   85216篇
  免费   2064篇
  国内免费   45篇
  87325篇
  2018年   981篇
  2017年   1154篇
  2016年   2901篇
  2015年   6199篇
  2014年   5803篇
  2013年   5578篇
  2012年   4758篇
  2011年   2006篇
  2010年   2120篇
  2009年   2063篇
  2008年   539篇
  2007年   501篇
  2006年   542篇
  2005年   6608篇
  2004年   5294篇
  2003年   3516篇
  2002年   1077篇
  2001年   1118篇
  2000年   357篇
  1999年   1512篇
  1998年   353篇
  1994年   204篇
  1992年   1942篇
  1991年   2047篇
  1990年   2095篇
  1989年   2023篇
  1988年   1976篇
  1987年   1828篇
  1986年   1642篇
  1985年   1690篇
  1984年   1114篇
  1983年   863篇
  1982年   489篇
  1981年   459篇
  1980年   392篇
  1979年   1100篇
  1978年   783篇
  1977年   628篇
  1976年   646篇
  1975年   894篇
  1974年   1021篇
  1973年   1025篇
  1972年   975篇
  1971年   947篇
  1970年   846篇
  1969年   854篇
  1968年   760篇
  1967年   778篇
  1966年   611篇
  1965年   444篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
The total and unsedimentable activity of acid DNase, RNase, phosphatase and arylsulfatases A and B was examined in the rat kidneys during long-term compression of soft tissues in the presence of high excitability of the sympathoadrenal system. Injection of adrenalin to rats with trauma reduced the total activity of DNase, acid phosphatase and arylsulfatases A and B, particularly at the late periods of soft tissue compression, whereas the total activity of acid RNase slightly increased as compared with control. Compression of soft tissues after adrenalin preinjection was accompanied by a substantial rise of unsedimentable activity of the lysosomal enzymes under study in the kidneys. The activity of the enzymes in cytosol progressively ascended as the time of soft tissue injury increased.  相似文献   
92.
The bacterial flagellum is composed of more than 20 different proteins. The filament, which constitutes the major extracellular part of the flagellum, is built up of approximately 20,000 FliC molecules that assemble at the growing distal end of the filament. A capping structure composed of five FliD molecules located at the tip of the filament promotes polymerization of FliC. Lack of FliD leads to release of the subunits into the growth medium. We show here that FliD can be successfully used in bacterial surface display. We tested various insertion sites in the capping protein, and the optimal region for display was at the variable region in FliD. Deletion and/or insertion at other sites resulted in decreased formation of flagella. We further developed the technique into a multihybrid display system in which three foreign peptides are simultaneously expressed within the same flagellum, i.e., D repeats of FnBPA from Staphylococcus aureus at the tip and fragments of YadA from Yersinia enterocolitica as well as SlpA from Lactobacillus crispatus along the filament. This technology can have biotechnological applications, e.g., in simultaneous delivery of several effector molecules.  相似文献   
93.
Character of conditioned reaction of passive avoidance was analyzed in Wistar line male rats after neurochemical destruction of terminal dopaminergic fields of the amygdalar complex. 6-hydroxydopamine was bilaterally administered to the central nucleus of the amygdalar complex after preliminary treating with desmethylimipramine for selective destruction of dopaminergic terminals. Lowering of dopamine level in the amygdalar complex led to a weakening of reproduction and to prolongation of spontaneous extinction of conditioned reaction. Features of conditioned reaction are highly similar to the effect of latent inhibition connected with attention deficit. It is suggested that activity of terminal fields of the amygdalar complex is one of the mechanisms providing for attention and intensifying selection of information in learning.  相似文献   
94.
95.
Injection of mouse scrotum with the bull seminal ribonuclease (BS RNase) isolated from bull seminal vesicle fluid inhibited spermatogenesis and caused a decrease in the weight of the testes. Long-term injection of BS RNase evoked the production of antibodies which reached the titre 524448. These antibodies did not prevent the aspermatogenic action of BS RNase in vivo when a twofold higher amount of this enzyme was injected into mouse scrotum. Aspermatogenesis was reversible in both the first and second part of the experiment. During the period of aspermatogenesis the males were sterile. Increasing the amount of BS RNase injections in the second part of experiments caused aspermatogenesis around 3 months. No malformations were observed among offspring of males recovered from the first stage of aspermatogenesis. The antigen—antibody complex prepared in vitro and injected into testes of mice evoked the same degree of aspermatogenesis as the enzyme itself.  相似文献   
96.
97.
98.
99.
100.
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