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   19414篇
  免费   1439篇
  国内免费   1588篇
  22441篇
  2024年   50篇
  2023年   337篇
  2022年   672篇
  2021年   1113篇
  2020年   686篇
  2019年   923篇
  2018年   826篇
  2017年   576篇
  2016年   884篇
  2015年   1177篇
  2014年   1490篇
  2013年   1545篇
  2012年   1834篇
  2011年   1585篇
  2010年   1005篇
  2009年   855篇
  2008年   960篇
  2007年   822篇
  2006年   666篇
  2005年   586篇
  2004年   487篇
  2003年   445篇
  2002年   388篇
  2001年   288篇
  2000年   295篇
  1999年   306篇
  1998年   196篇
  1997年   200篇
  1996年   189篇
  1995年   155篇
  1994年   140篇
  1993年   99篇
  1992年   140篇
  1991年   116篇
  1990年   100篇
  1989年   78篇
  1988年   52篇
  1987年   31篇
  1986年   29篇
  1985年   41篇
  1984年   18篇
  1983年   23篇
  1982年   13篇
  1981年   7篇
  1980年   3篇
  1979年   4篇
  1965年   1篇
  1963年   1篇
  1962年   1篇
  1950年   1篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
度下的动态变化对虹鳟南移温水驯化养殖具有参考价值.  相似文献   
62.
Mycosin-1 protease (MycP1) is a serine protease anchored to the inner membrane of Mycobacterium tuberculosis, and is essential in virulence factor secretion through the ESX-1 type VII secretion system (T7SS). Bacterial physiology studies demonstrated that MycP1 plays a dual role in the regulation of ESX-1 secretion and virulence, primarily through cleavage of its secretion substrate EspB. MycP1 contains a putative N-terminal inhibitory propeptide and a catalytic triad of Asp-His-Ser, classic hallmarks of a subtilase family serine protease. The MycP1 propeptide was previously reported to be initially inactive and activated after prolonged incubation. In this study, we have determined crystal structures of MycP1 with (MycP124-422) and without (MycP163-422) the propeptide, and conducted EspB cleavage assays using the two proteins. Very high structural similarity was observed in the two crystal structures. Interestingly, protease assays demonstrated positive EspB cleavage for both proteins, indicating that the putative propeptide does not inhibit protease activity. Molecular dynamic simulations showed higher rigidity in regions guarding the entrance to the catalytic site in MycP124-422 than in MycP163-422, suggesting that the putative propeptide might contribute to the conformational stability of the active site cleft and surrounding regions.  相似文献   
63.
Initial functional studies have demonstrated that RNA‐binding motif protein 10 (RBM10) can promote apoptosis and suppress cell proliferation; however, the results of several studies suggest a tumour‐promoting role for RBM10. Herein, we assessed the involvement of RBM10 in lung adenocarcinoma cell proliferation and explored the potential molecular mechanism. We found that, both in vitro and in vivo, RBM10 overexpression suppresses lung adenocarcinoma cell proliferation, while its knockdown enhances cell proliferation. Using complementary DNA microarray analysis, we previously found that RBM10 overexpression induces significant down‐regulation of RAP1A expression. In this study, we have confirmed that RBM10 decreases the activation of RAP1 and found that EPAC stimulation and inhibition can abolish the effects of RBM10 knockdown and overexpression, respectively, and regulate cell growth. This effect of RBM10 on proliferation was independent of the MAPK/ERK and P38/MAPK signalling pathways. We found that RBM10 reduces the phosphorylation of CREB via the AKT signalling pathway, suggesting that RBM10 exhibits its effect on lung adenocarcinoma cell proliferation via the RAP1/AKT/CREB signalling pathway.  相似文献   
64.
Eukaryotes segregate chromosomes in "open" or "closed" mitosis, depending on whether their nuclear envelopes (NEs) break down or remain intact. Here we show that the control of the nuclear surface area may determine the choice between these two modes. The dividing nucleus does not expand its surface in the fission yeast Schizosaccharomyces japonicus, confining the mitotic spindle and causing it to?buckle. The NE ruptures in anaphase, releasing the compressive stress and allowing chromosome segregation.?Blocking the NE expansion in the related species Schizosaccharomyces pombe that undergoes closed mitosis induces spindle buckling and collapse in the absence of an intrinsic NE rupture mechanism. We propose that scaling considerations could have shaped the evolution of eukaryotic mitosis by necessitating either nuclear surface expansion or the NE breakdown.  相似文献   
65.
66.
A novel pink-coloured, non-spore-forming, non-motile, Gram-negative bacterium, designated YIM 48858T, is described by using a polyphasic approach. The strain can grow at pH 6.5–9 (optimum at pH 7) and 25–30°C (optimum at 28°C). NaCl is not required for its growth. Positive for oxidase and catalase. Urease activity, nitrate reduction, starch and Tween 80 tests are negative reaction. 16S rRNA gene sequence similarity studies showed that strain YIM 48858T is a member of the genus Rubellimicrobium, with similarities of 96.3, 95.7 and 95.5% to Rubellimicrobium mesophilum MSL-20T, Rubellimicrobium aerolatum 5715S-9T and Rubellimicrobium thermophilum DSM 16684T, respectively. Q-10 was the predominant respiratory ubiquinone as in the other members of the genus Rubellimicrobium. The major polar lipids were diphosphatidylglycerol, phosphatidylcholine, phosphoglycolipid, glycolipid and the major fatty acids were C18:1 ω7c, C16:0 and C10:0 3-OH, which are very different from the valid published species. The DNA G + C content was 67.7 mol%. Both phylogenetic and chemotaxonomic evidence supports that YIM 48858T is a novel species of the genus Rubellimicrobium, for which the name Rubellimicrobium roseum sp. nov. is proposed. The type strain is YIM 48858T (=CCTCC AA 208029T =KCTC 23202T).  相似文献   
67.

Necroptosis is a programmed necrosis that is mediated by receptor-interacting protein kinases RIPK1, RIPK3 and the mixed lineage kinase domain-like protein, MLKL. Necroptosis must be strictly regulated to maintain normal tissue homeostasis, and dysregulation of necroptosis leads to the development of various inflammatory, infectious, and degenerative diseases. Ubiquitylation is a widespread post-translational modification that is essential for balancing numerous physiological processes. Over the past decade, considerable progress has been made in the understanding of the role of ubiquitylation in regulating necroptosis. Here, we will discuss the regulatory functions of ubiquitylation in necroptosis signaling pathway. An enhanced understanding of the ubiquitylation enzymes and regulatory proteins in necroptotic signaling pathway will be exploited for the development of new therapeutic strategies for necroptosis-related diseases.

  相似文献   
68.
69.
用鲜花循环式动态顶空技术采集红厚壳鲜花的香气成分,TCT-GC-MS联用技术分析鉴定。4-羟基-2-丁酮,双烯酮,1、2-环氧-2-甲基丁烷,1、2-环氧-3-甲基丁烷,2-乙基戊烷,3-己醇,甲基环戊烷,2-丁醇等24个成分被检测出,占总离子流出峰面积的90.28%。并对结果进行了分析讨论。  相似文献   
70.
iQPR技术处理污水是一项新型尖端的技术,此技术可以成功降低污水乃至受到污染的地下水中的各种污染指标。但是,iQPR技术处理污水尤其是地下水是否存在潜在的生物安全性问题有待于进一步研究。因此,为评估iQPR技术对生物安全性的影响,本研究首先分析了三种不同iQPR法处理水的水质成分;其次系统研究了iQPR水对SD鼠在个体水平、组织水平和病理形态学损伤的研究。研究表明:iQPR处理的水质成分较对照组普通饮用水好,在个体组织水平检测未见异常,尽管其中一组iQPR处理水造成了SD鼠的脾小体增大,但是可能的原因是水处理环节存在微生物污染现象,因此,初步认定此技术未造成SD大鼠的个体损伤。本研究为揭示iQPR处理的水对生物体的安全性评价提供一个理论依据。  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