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   2276篇
  免费   159篇
  2435篇
  2023年   4篇
  2022年   25篇
  2021年   30篇
  2020年   16篇
  2019年   35篇
  2018年   60篇
  2017年   44篇
  2016年   82篇
  2015年   115篇
  2014年   99篇
  2013年   163篇
  2012年   199篇
  2011年   191篇
  2010年   122篇
  2009年   114篇
  2008年   150篇
  2007年   130篇
  2006年   108篇
  2005年   109篇
  2004年   123篇
  2003年   104篇
  2002年   121篇
  2001年   15篇
  2000年   11篇
  1999年   4篇
  1998年   22篇
  1997年   15篇
  1996年   17篇
  1995年   15篇
  1994年   13篇
  1993年   17篇
  1992年   18篇
  1991年   12篇
  1990年   6篇
  1989年   5篇
  1988年   6篇
  1987年   5篇
  1986年   3篇
  1985年   6篇
  1984年   12篇
  1983年   11篇
  1982年   11篇
  1981年   11篇
  1980年   7篇
  1979年   9篇
  1978年   3篇
  1977年   4篇
  1975年   10篇
  1974年   7篇
  1963年   2篇
排序方式: 共有2435条查询结果,搜索用时 15 毫秒
171.
Sleep and Biological Rhythms - The aim of the present work was to validate the reduced version of the Morningness-Eveningness Questionnaire (MEQr) using circadian motor activity as external...  相似文献   
172.
The major lipid component of the brown seaweed Zonaria tournefortii was identified as the acylphlorogluconol (all Z)-2′-icosa-5,8,11,14,17-pentae  相似文献   
173.
Cisgenesis is a genetic modification of a recipient organism with genetic material from a crossable organism. Trying to free cisgenics from the regulatory guidelines of genetically modified organisms (GMOs), some scientists have suggested to classify the genetically modified products by the origin of transferred genes. Aiming at exploring how scientists frame cisgenics in relation to current legal frameworks, we have sent an extensive survey to the totality of researchers working on cisgenics. Trying to provide cisgenics with a new, uncontroversial identity, the respondents present cisgenics as a method of obtaining “natural,” environmentally friendly and economically sustainable crops. However, such strategy is challenged by GMO corporations opposing a segmentation of the sector, and by the opponents of GMOs, who fear that deregulation on cisgenics leads to the deregulation of GMOs. Drawing from the concepts of bio-objectification and bio-identification, we show how the status of this bio-object is likely to remain contested and contestable.  相似文献   
174.
175.
Methenyltetrahydromethanopterin cyclohydrolase (Mch) is involved in the methanogenesis pathway of archaea as a C1 unit carrier where N5‐formyl‐tetrahydromethanopterin is converted to methenyl‐tetrahydromethanopterin. Mch from Methanobrevibacter ruminantium was cloned, purified, crystallized and its crystal structure solved at 1.37 Å resolution. A biologically active trimer, the enzyme is composed of two domains including an N‐terminal domain of six α‐helices encompassing a series of four β‐sheets and a predominantly anti‐parallel β–sheet at the C‐terminus flanked on one side by α‐helices. Sequence and structural alignments have helped identify residues involved in substrate binding and trimer formation. Proteins 2013; 81:2064–2070. © 2013 Wiley Periodicals, Inc.  相似文献   
176.
177.
178.
179.
We describe the molecular mechanisms of apoptosis and its relationships with hematologic malignancies, stressing the concept that, both positive and negative deregulation of apoptosis, may be involved in hematologic human diseases. So, this fundamental process must be balanced by so far unknown mechanisms, involving caspases (cysteine proteases, cleaving the protein substrate after an aspartate residue). These, so far known, ten proteases, are interconnected in a molecular cascade, initiated by the release of cytochrome C from mitochondrial membranes and its interaction with APAF-1 (the homolog of the Caenorhabditis e. CED-4) and with caspase 9, that initiates the proteolitic cascade (1,2). The conclusion is that apoptosis is a very important process, but yet poorly known in molecular details, in spite of the efforts of many scientists. Even the role of bcl-2, the main gene protecting from apoptosis, is still unknown. We close this chapter with a list of ten different technical approaches that can be useful tools to study apoptosis, and tracing the molecular principles on which they are based.  相似文献   
180.
The amino acid sequence of wheatwin1, a monomeric protein of 125 residues isolated from wheat kernel (variety S. Pastore), is reported. Wheatwin1 is highly homologous (95%) to barwin, a protein from barley seed, which was shown to be related to the C-terminal domain of two proteins encoded by the wound-induced geneswin1 andwin2 in potato and to a protein encoded by the same domain of the hevein gene (hev1) in rubber tree. Similarly to barwin, wheatwin1 contains six cysteine residues all linked in disulfide bridges and the N-terminal residue is pyroglutamate. Moreover, structural studies performed on wheatwin1 andwin1 protein by predictive methods demonstrated that these proteins and barwin are closely related in the secondary structure also. The high level of homology found with the product ofwin1,win2, andhev1 genes strongly suggests that barwin and wheatwin1 play a common role in the mechanism of plant defence.  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