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   644847篇
  免费   171360篇
  国内免费   30336篇
  2018年   7827篇
  2017年   7404篇
  2016年   9620篇
  2015年   12219篇
  2014年   14258篇
  2013年   18492篇
  2012年   21619篇
  2011年   22866篇
  2010年   17446篇
  2009年   20701篇
  2008年   21134篇
  2007年   21711篇
  2006年   19535篇
  2005年   18687篇
  2004年   18834篇
  2003年   17510篇
  2002年   17810篇
  2001年   28910篇
  2000年   27105篇
  1999年   25459篇
  1998年   14431篇
  1997年   14059篇
  1996年   13141篇
  1995年   13113篇
  1994年   12393篇
  1993年   12072篇
  1992年   22419篇
  1991年   22360篇
  1990年   22631篇
  1989年   21674篇
  1988年   20055篇
  1987年   18519篇
  1986年   17338篇
  1985年   16910篇
  1984年   13704篇
  1983年   11638篇
  1982年   9508篇
  1981年   8579篇
  1980年   8236篇
  1979年   12555篇
  1978年   10367篇
  1977年   9427篇
  1976年   8828篇
  1975年   9623篇
  1974年   10673篇
  1973年   10423篇
  1972年   9994篇
  1971年   9164篇
  1970年   8002篇
  1969年   7813篇
排序方式: 共有10000条查询结果,搜索用时 671 毫秒
991.
992.
Conclusion Since the EPG method is increasingly utilized in the investigation of plant-Homoptera interactions, this software has been developed to enable fast processing of abundant data. The objective seems to have been achieved and, with a little practice, a 2-hour experiment may be analysed in about 10–15 minutes. Mac-Stylet is stand-alone shareware, freely distributed to all persons interested (request to G. Febvay, email: febvay@jouy.inra.fr).  相似文献   
993.
The structure of the tightly bound complex of the globular myosin head with F-actin is the key to understanding important details of the mechanism of how the actin-myosin motor functions. The current notion on this complex is based on the docking of known atomic structures of constituent proteins into low-resolution electron-density maps. The atomic structure of the complex was refined by the molecular mechanics method, which consists in minimizing the energy of molecular interaction and which makes it possible to optimize not only the relative position of protein backbones as rigid bodies, but also the position of side chains on the protein interface. The structure calculated using ICM-Pro software, on the one hand, is close to the model obtained using electron microscopy; on the other hand, it ensures the best calculated interaction energy and accounts for the results of mutagenesis experiments. On the basis of the structure obtained, we can suggest the molecular mechanisms underlying the actin-activated release of ATP hydrolysis products from myosin and the decrease in the affinity of myosin for actin upon binding of nucleotides.  相似文献   
994.
995.
996.
The morphology of dissociated single cerebellar Purkinje cells obtained from wild-type P1 CD1 mice was assessed in the absence and in the presence of glia. A dedicated noninvasive technique based on optical microscopy was developed. Image processing algorithms were implemented to extract metrical features characterizing cell structure and dendritic arborization. The morphological features were analyzed in order to identify quantitative differences in Purkinje cell morphology due to interactions with astrocytes.  相似文献   
997.
998.
Fourteen fresh run salmon Satmo salar L. with early extant lesions of ulcerative dermal necrosis (UDN) were kept in separate tanks and treated with zinc free malachite green. Ten of the fish were held at 10° C and 4 at 2° C. The treatment precluded infection with Saprolegnia fungus and allowed natural resolution of the lesions. There was a marked difference in rate of healing between warm and cold water conditions.
Histological examination of healing lesions at different stages showed that there was a primary invasion of cuboidal epithelium over the collagen scar followed by a phase of disorganized proliferation which eventually organized itself into normal epithelium. Melanocytes were very obvious in the dermis of healing lesions.  相似文献   
999.
1000.
The 1701-base nucleotide sequence (not including the poly(A) tail) of a cDNA for the gamma subunit of the ATP synthase from Chlamydomonas reinhardtii was determined. A start translation sequence, 23 bases in from the 5' end, initiates an 1074-base-long open reading frame. The sequence of the first 21 amino acids at the amino-terminal end of the mature gamma subunit from C. reinhardtii was determined and compared to the deduced amino acid sequence of the open reading frame. From this it was determined that the mature protein contains 323 amino acids, with the first 35 amino acids probably being part of the transit peptide. The length of the mature protein is the same as that for the mature gamma subunit from spinach, for which only a few of the amino acids of the transit peptide are known. The similarity of the two mature proteins at the nucleotide level is 56% while at the amino acid level it is 77%. In addition, the 3 cysteines, which in spinach are involved in the energy-linked catalytic functions of the ATP synthase, are conserved in the predicted amino acid sequence for the gamma subunit from C. reinhardtii. In contrast, the mature C. reinhardtii gamma subunit contains 3 additional cysteine residues not found in the spinach gamma subunit.  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