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   504592篇
  免费   54556篇
  国内免费   740篇
  2018年   5743篇
  2017年   5503篇
  2016年   7630篇
  2015年   10770篇
  2014年   12081篇
  2013年   16316篇
  2012年   19464篇
  2011年   19610篇
  2010年   12807篇
  2009年   11171篇
  2008年   16832篇
  2007年   17158篇
  2006年   16118篇
  2005年   15181篇
  2004年   15173篇
  2003年   14113篇
  2002年   13611篇
  2001年   20165篇
  2000年   20141篇
  1999年   16096篇
  1998年   5983篇
  1997年   5883篇
  1996年   5621篇
  1995年   5392篇
  1994年   5052篇
  1993年   5040篇
  1992年   13183篇
  1991年   13174篇
  1990年   12924篇
  1989年   12367篇
  1988年   11583篇
  1987年   10877篇
  1986年   10367篇
  1985年   10099篇
  1984年   8382篇
  1983年   7233篇
  1982年   5379篇
  1981年   4829篇
  1980年   4509篇
  1979年   7699篇
  1978年   6280篇
  1977年   5540篇
  1976年   5229篇
  1975年   6132篇
  1974年   6689篇
  1973年   6522篇
  1972年   5806篇
  1971年   5358篇
  1970年   4568篇
  1969年   4477篇
排序方式: 共有10000条查询结果,搜索用时 78 毫秒
921.
A survey was done of Canadians who had been interned by the Japanese during World War II to assess the prevalence of latent infection with Strongyloides stercoralis in this group. Packages containing three mail-in kits and a questionnaire were sent to 992 men, 694 (70%) of whom responded. Larvae were found in the stool specimens of four of the respondents. Examination of stool specimens after formalin-ether concentration was the most successful method of detecting Strongyloides larvae. The Baermann concentration technique yielded negative results in all four men. Three of the four cases of strongyloidiasis were detected after sampling of three fecal specimens. In the fourth case additional specimens were requested on the basis of data derived from the questionnaire. The most frequently cited clinical manifestations were abdominal pain, weight loss, diarrhea and rashes.  相似文献   
922.
923.
The influence of brain acid extract products, isolated by high-performance liquid chromatography on H3-diazepam binding was investigated in synaptosomal membranes of C57BL/6 and BALB/c mice. Fractions with stimulatory and inhibitory activity were isolated. Quantitative and qualitative differences in the effects and structure of ACTH-immunoreactive peptide fractions under study were established.  相似文献   
924.
The introduction of either PGF (10?7 M) or TPA (10?7 M) stimulated, ouabain-sensitive 86Rb+ influx at 30 min in postconfluent 3T3-4 mouse fibroblast cultures by 117% and 124%, respectively. Both TPA and PGF at these concentrations stimulated the incorporation of 3H-TdR into DNA. TPA had the greatest stimulatory effect, which was similar to that obtained with 10% fetal calf serum. In accord with the idea that modulation of membrane processes such as Na+/K+ pump activity in fibroblasts may reflect important events related to the initiation of DNA synthesis, it was observed that in both 3T3-4 and C3H-1 0T½ cells there were parallel increases in 3H-TdR incorporation and ouabain-sensitive 86Rb+ influxes with 10?7 M TPA, whereas PGF stimulated a significant increase in 3H-TdR incorporation in 3T3-4 but not C3H-10T½ cells and only marginal increases in ouabain-sensitive 86Rb+ influx in both. Therefore, although there appears to be a close correlation between Na+/K+ pump activation and subsequent S-phase entry following TPA stimulation, a similar correlation for PGF cannot be confirmed.  相似文献   
925.
Astrocytes have long been considered as just providing trophic support for neurons in the central nervous system, but recently several studies have highlighted their importance in many functions such as neurotransmission, metabolite and electrolyte homeostasis, cell signaling, inflammation, and synapse modulation. Astrocytes are, in fact, part of a bidirectional crosstalk with neurons. Moreover, increasing evidence is stressing the emerging role of astrocyte dysfunction in the pathophysiology of neurological disorders, including neurodegenerative disease, stroke, epilepsy, migraine, and neuroinflammatory diseases.  相似文献   
926.
Results are presented from experimental investigations of the angular distributions and energy spectra of fast ions produced in deuterium polyethylene targets under irradiation by picosecond laser pulses with intensities of up to 2 × 1018 W/cm2 in the SOKOL-P facility. The parameters of ion fluxes were measured by time-of-flight spectrometers based on semiconductor detectors.  相似文献   
927.
928.
929.
930.
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