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   333643篇
  免费   37323篇
  国内免费   188篇
  2018年   2858篇
  2017年   2713篇
  2016年   3892篇
  2015年   5361篇
  2014年   6272篇
  2013年   8799篇
  2012年   10049篇
  2011年   10009篇
  2010年   6842篇
  2009年   6170篇
  2008年   8895篇
  2007年   9333篇
  2006年   8622篇
  2005年   8320篇
  2004年   8042篇
  2003年   7785篇
  2002年   7792篇
  2001年   18170篇
  2000年   18395篇
  1999年   14120篇
  1998年   4237篇
  1997年   4505篇
  1996年   4309篇
  1995年   4014篇
  1994年   3947篇
  1993年   3790篇
  1992年   11496篇
  1991年   11139篇
  1990年   10691篇
  1989年   10254篇
  1988年   9498篇
  1987年   8858篇
  1986年   8095篇
  1985年   7976篇
  1984年   6405篇
  1983年   5577篇
  1982年   4110篇
  1981年   3603篇
  1980年   3362篇
  1979年   6118篇
  1978年   4577篇
  1977年   4139篇
  1976年   3770篇
  1975年   4340篇
  1974年   4510篇
  1973年   4405篇
  1972年   4104篇
  1971年   3503篇
  1970年   3179篇
  1969年   2987篇
排序方式: 共有10000条查询结果,搜索用时 437 毫秒
981.
Mammalian target of Rapamycin C1 (mTORC1) inhibition limits plaque progression in atherosclerosis. The present study evaluated the protective effect of sulfamethizole on poloxamer 407-induced atherosclerotic neointima formation in C57BL/6 mice via mTOR inhibition. Poloxamer 407 (P-407) (0.5 g/kg body weight) was administered intraperitoneally to male C57BL/6 mice every third day for 148 days to induce chronic hyperlipidemia. From Day 121 to 148, animals were additionally administered Sulfamethizole (5, 10, and 50 mg/kg, p.o.), Rapamycin (0.5 mg/kg, positive control), or vehicle (1 ml/kg). Plasma lipid levels were measured on Days 120 and 148. Upon sacrifice, histological studies were performed, and aortic tissue interleukin (IL)-6, tumor necrosis factor-α (TNF-α), and mTOR levels were evaluated. A molecular docking study was carried out to mimic the interaction of sulfamethizole with mTOR protein. Chronic P-407 administration significantly (p < 0.001) elevated plasma lipid levels, compared with those of the normal control group. Chronic hyperlipidemia resulted in increased tunica intima thickness, collagen deposition, and IL-6, TNF-α, and mTOR levels. Treatment with Sulfamethizole attenuated these parameters significantly in a dose-dependent manner. Molecular docking studies showed a significant interaction of Sulfamethizole with mTOR. In conclusion, this study suggests that sulfamethizole significantly limits poloxamer 407-induced atherosclerotic neointima formation in C57BL/6 mice via mTOR inhibition.  相似文献   
982.
983.
984.
985.
986.
987.
A Ca2+-dependent sialic acid-binding protein was purified on fetuin-Sepharose from various types of human tissue. The molecular mass was determined to be 10,315 Da by laser desorption mass spectrometry. Partial sequence analysis after cyanogen bromide cleavage that yielded one N-terminus accessible for Edman degradation revealed an identity to an internal stretch following the only methionine residue within a putative amino acid sequence (Mr 10,048), deduced from the cDNA of a cell cycle-specific gene. The reported biochemical identification is a prerequisite to infer the biological role of the so far undetected gene product. Initial glycohistochemical studies with sialic acid-(BSA-biotin) raised evidence for nuclear localization of sialic acid-binding sites that might reflect, at least in part, detection of this protein.  相似文献   
988.
The results of a detailed analysis of 100 supernumerary limbs generated by 180° ipsilateral rotation (on the same limb stump) of regeneration blastemas is presented. The limbs were analyzed in terms of their position of origin, frequency, cartilage structure by Victoria blue staining, and muscle structure by serial sections. Single, double, or triple supernumeraries can be produced at no unique position of origin, although the posterodorsal quadrant was preferred. Four classes of supernumerary limbs were generated by such operations—normal; double dorsal or double ventral; part normal/part mirror imaged; part normal/part inverted in approximately equal frequencies. After amputation of these supernumeraries the same muscle patterns are faithfully regenerated. A hypothesis to explain the production of these abnormal limbs is proposed based on the observed phenomenon of fusion of supernumerary blastemata, but their regenerative behaviour presents problems for current models of pattern formation. Similar results have been obtained with developing limb buds and the relation between development and regeneration is discussed.  相似文献   
989.
The biosynthesis of the haemagglutinin glycoproteins of infectious influenza virus particles involves proteolytic cleavage of the primary translation products and the amino acid sequences at the two sites of processing are presented. In addition, details of the primary structure of the haemagglutinin of A/Japan/305/57 (H2N1) are reported and compared with information available for haemagglutinins of other subtypes.  相似文献   
990.
MAT alpha haploids with mutations in the STE13 or KEX2 gene, and MATa haploids with mutations in the STE6 or STE14 gene, do not mate with wild-type cells of the opposite mating type. We found that such mutants were able to mate with partners that carry mutations (sst1 and sst2) that cause cells to be supersensitive to yeast mating pheromone action. Mating ability of MAT alpha ste13 and MAT alpha kex2 mutants could also be restored by adding normal MAT alpha cells to mating mixtures or by adding just the appropriate purified pheromone (alpha-factor). Therefore, the mating deficiencies caused by the ste13 and kex2 lesions, and by inference, the ste6 and ste14 mutations, appear to result only from secretion of an insufficient amount of pheromone or a nonfunctional pheromone.  相似文献   
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