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   36269篇
  免费   2754篇
  国内免费   2600篇
  41623篇
  2024年   88篇
  2023年   454篇
  2022年   1112篇
  2021年   1798篇
  2020年   1256篇
  2019年   1547篇
  2018年   1496篇
  2017年   1095篇
  2016年   1526篇
  2015年   2300篇
  2014年   2651篇
  2013年   2866篇
  2012年   3256篇
  2011年   2825篇
  2010年   1825篇
  2009年   1570篇
  2008年   1871篇
  2007年   1667篇
  2006年   1471篇
  2005年   1237篇
  2004年   1081篇
  2003年   966篇
  2002年   777篇
  2001年   723篇
  2000年   529篇
  1999年   521篇
  1998年   317篇
  1997年   313篇
  1996年   311篇
  1995年   264篇
  1994年   265篇
  1993年   179篇
  1992年   236篇
  1991年   205篇
  1990年   142篇
  1989年   118篇
  1988年   87篇
  1987年   120篇
  1986年   86篇
  1985年   72篇
  1984年   56篇
  1983年   39篇
  1982年   40篇
  1981年   27篇
  1980年   21篇
  1979年   25篇
  1978年   17篇
  1975年   21篇
  1974年   18篇
  1972年   17篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
Disodium palmityl phosphonoformate, a novel lipid phosphoester of the anti HIV agent phosphonoformate (foscarnet), inhibits HIV replication in H9 cells and syncytia formation in MOLT-3 cells as effectively as foscarnet itself, as shown by dose-response data from assays for expression of p17 and p24 viral antigens and syncytia formation. Protein binding studies indicate that in serum, the derivative exists bound to albumin and the lipoproteins, and would therefore be likely to exhibit improved serum lifetime in vivo.  相似文献   
32.
The differentiation of mammalian urothelium culminates in the formation of asymmetrical unit membrane (AUM). Using gradient centrifugation and detergent wash, we purified milligram quantities of AUMs which, interestingly, contained three major proteins (15, 27, and 47 kDa) that appeared to be identical to the three immunoaffinity purified, putatively AUM-associated proteins that we described earlier (Yu, J., Manabe, M., Wu, X.-R., Xu, C., Surya, B., and Sun, T.-T. (1990) J. Cell Biol., 111, 1207-1216). Peptide mapping and immunoblotting established that these three proteins were distinct molecules. Using monospecific antibodies to these three proteins, we showed that they were all restricted to the superficial urothelial cells and were AUM-associated. The 27- and 15-kDa proteins were detected exclusively on the luminal side of mature, apical AUMs. In contrast, epitopes of the 47-kDa protein were detected on both sides of apical AUMs suggesting a transmembranous configuration. These results (i) provide the strongest evidence thus far that AUM contains three major proteins (the 27-kDa uroplakin I, 15-kDa uroplakin II, and 47-kDa uroplakin III) which form an extremely insoluble complex, (ii) suggest that uroplakin II, like uroplakin I (Yu, J., Manabe, M., Wu, X.-R., Xu, C., Surya, B., and Sun, T.-T. (1990) J. Cell. Biol. 111, 1207-1216), translocates from one side of the membrane to another during AUM maturation, (iii) indicate that uroplakin III may play a different structural role than uroplakins I and II in AUM formation, and (iv) establish the three uroplakins as markers for an advanced stage of urothelial differentiation.  相似文献   
33.
An agar medium, LL-agar (lactate-lead acetate) was designed to selectively differentiate members of the genus Pectinatus (S. Y. Lee, M. S. Mabee, and N. O. Jangaard, Int. J. Syst. Bacteriol. 28:582-594, 1978; S. Y. Lee, M. S. Mabee, N. O. Jangaard, and E. K. Horiuchi, J. Inst. Brew. 86:28-30, 1980) from other brewery microorganisms. Selectivity was achieved by the use of sodium lactate as the sole source of carbon and phenylethyl alcohol as an inhibitor for aerobic gram-negative bacteria and yeast. Differentiation was established by the introduction of lead acetate into the medium, which reacted with the H2S liberated by Pectinatus and resulted in a blackening of the Pectinatus colonies while the other brewery organisms, when present, remained white. In combination with the Lee tube (J. E. Ogg, S. Y. Lee, and B. J. Ogg, Can. J. Microbiol. 25:987-990, 1979) and this medium, isolation of Pectinatus organisms from beer samples was accomplished with convenience and simplicity.  相似文献   
34.
The transformation of 6-keto-PGF to two prostacyclin metabolites, 2,3-dinor-6-keto-PGF (I) and 2,3-dinor-6,15-diketo-13,14-dihydro-PGF (II) by Mycobacterium rhodochrous UC-6176 is described. The finding that the bacterium oxidized 6-keto-PGF to the 6,15-diketo metabolite II shows that it contains 15-hydroxy prostaglandin dehydrogenase and Δ13 reductase enzyme systems.  相似文献   
35.
36.
Schistosomiasis is a serious and widespread parasitic disease caused by infection with Schistosoma. Because the parasite’s eggs are primarily responsible for schistosomiasis dissemination and pathogenesis, inhibiting egg production is a potential approach to control the spread and severity of the disease. The bromodomain and extra-terminal (BET) proteins represent promising targets for the development of epigenetic drugs against Schistosoma. JQ-1 is a selective inhibitor of the BET protein family. In the present study, JQ-1 was applied to S. japonicum in vitro. By using laser confocal scanning microscopy and EdU incorporation assays, we showed that application of JQ-1 to worms in vitro affected egg laying and the development of both the male and female reproductive systems. JQ-1 also inhibited the expression of the reproductive-related genes SjPlk1 and SjNanos1 in S. japonicum. Mice infected with S. japonicum were treated with JQ-1 during egg granuloma formation. JQ-1 treatment significantly reduced the size of the liver granulomas and levels of serum alanine aminotransferase and aspartate aminotransferase in mice and suppressed both egg laying and the development of male and female S. japonicum reproductive systems in vivo. Moreover, the mRNA expression levels of some proinflammatory cytokines were decreased in the parasites. Our findings suggest that JQ-1 treatment attenuates S. japonicum egg–induced hepatic granuloma due at least in part to suppressing the development of the reproductive system and egg production of S. japonicum. These findings further suggest that JQ-1 or other BET inhibitors warrant additional study as a new approach for the treatment or prevention of schistosomiasis.  相似文献   
37.
Aging is a major risk factor for many diseases,especially in highly prevalent cardiopulmonary comorbidities and infectious diseases including Coronavirus Diseas...  相似文献   
38.
39.
40.
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