全文获取类型
收费全文 | 33516篇 |
免费 | 205篇 |
国内免费 | 357篇 |
专业分类
系统科学 | 300篇 |
丛书文集 | 560篇 |
教育与普及 | 203篇 |
理论与方法论 | 152篇 |
现状及发展 | 13436篇 |
研究方法 | 1410篇 |
综合类 | 17495篇 |
自然研究 | 522篇 |
出版年
2013年 | 371篇 |
2012年 | 657篇 |
2011年 | 1155篇 |
2010年 | 348篇 |
2009年 | 309篇 |
2008年 | 747篇 |
2007年 | 838篇 |
2006年 | 734篇 |
2005年 | 761篇 |
2004年 | 796篇 |
2003年 | 685篇 |
2002年 | 760篇 |
2001年 | 1048篇 |
2000年 | 969篇 |
1999年 | 837篇 |
1996年 | 267篇 |
1992年 | 660篇 |
1991年 | 486篇 |
1990年 | 504篇 |
1989年 | 474篇 |
1988年 | 481篇 |
1987年 | 459篇 |
1986年 | 482篇 |
1985年 | 599篇 |
1984年 | 426篇 |
1983年 | 340篇 |
1982年 | 317篇 |
1981年 | 333篇 |
1980年 | 397篇 |
1979年 | 930篇 |
1978年 | 734篇 |
1977年 | 721篇 |
1976年 | 541篇 |
1975年 | 538篇 |
1974年 | 842篇 |
1973年 | 693篇 |
1972年 | 780篇 |
1971年 | 814篇 |
1970年 | 1132篇 |
1969年 | 900篇 |
1968年 | 772篇 |
1967年 | 818篇 |
1966年 | 758篇 |
1965年 | 570篇 |
1959年 | 274篇 |
1958年 | 533篇 |
1957年 | 369篇 |
1956年 | 279篇 |
1955年 | 261篇 |
1954年 | 301篇 |
排序方式: 共有10000条查询结果,搜索用时 859 毫秒
881.
882.
Lubka-Pathak M Shah AA Gallozzi M Müller M Zimmermann U Löwenheim H Pfister M Knipper M Blin N Schimmang T 《Cellular and molecular life sciences : CMLS》2011,68(16):2739-2749
Introduction
Tff3 peptide exerts important functions in cytoprotection and restitution of the gastrointestinal (GI) tract epithelia. Moreover, its presence in the rodent inner ear and involvement in the hearing process was demonstrated recently. However, its role in the auditory system still remains elusive. Our previous results showed a deterioration of hearing with age in Tff3-deficient animals.Results
Present detailed analysis of auditory brain stem response (ABR) measurements and immunohistochemical study of selected functional proteins indicated a normal function and phenotype of the cochlea in Tff3 mutants. However, a microarray-based screening of tissue derived from the auditory central nervous system revealed an alteration of securin (Pttg1) and serpina3n expression between wild-type and Tff3 knock-out animals. This was confirmed by qRT-PCR, immunostaining and western blots.Conclusions
We found highly down-regulated Pttg1 and up-regulated serpina3n expression as a consequence of genetically deleting Tff3 in mice, indicating a potential role of these factors during the development of presbyacusis. 相似文献883.
Freinbichler W Colivicchi MA Stefanini C Bianchi L Ballini C Misini B Weinberger P Linert W Varešlija D Tipton KF Della Corte L 《Cellular and molecular life sciences : CMLS》2011,68(12):2067-2079
The so-called reactive oxygen species (ROS) are defined as oxygen-containing species that are more reactive than O(2) itself, which include hydrogen peroxide and superoxide. Although these are quite stable, they may be converted in the presence of transition metal ions, such as Fe(II), to the highly reactive oxygen species (hROS). hROS may exist as free hydroxyl radicals (HO·), as bound ("crypto") radicals or as Fe(IV)-oxo (ferryl) species and the somewhat less reactive, non-radical species, singlet oxygen. This review outlines the processes by which hROS may be formed, their damaging potential, and the evidence that they might have signaling functions. Since our understanding of the formation and actions of hROS depends on reliable procedures for their detection, particular attention is given to procedures for hROS detection and quantitation and their applicability to in vivo studies. 相似文献
884.
F.A.Zhang L.Chen J.Q.Ma X.Yang 《复旦学报(自然科学版)》2007,46(5)
1 Results Nanocomposite has attracted more and more interest all over the world.Polystyrene (PS) is a commercialized and mass-productive polymer,continuous research efforts have been devoted to the development of polystyrene/montmorillonite (PS/MMT) nanocomposites[1-2].But the polarity of styrene (St) is too small to intercalate the space between the clay layers.The polarity of hydrophilic monomer is so strong that it can intercalate the MMT easily,the intercalated smectic clays maybe exfoliated by usin... 相似文献
885.
Jérémie Gautheron Gilles Courtois 《Cellular and molecular life sciences : CMLS》2010,67(18):3101-3113
Ubiquitination has emerged over the years as the most sophisticated way to modify proteins to affect their fate and function.
In particular, it has been reported to be instrumental in regulating several steps of the NF-κB signalling pathway which controls
inflammation, immunity, adhesion and cell survival. Integrating ubiquitination into NF-κB activation requires the regulatory
subunit of IKK, NEMO, which not only displays affinity for polyubiquitin chains, but is also posttranslationally modified
by a complex set of reactions involving ubiquitin. Here, we examine how studies of the NEMO/ubiquitin relationship have provided
novel insights into the IKK activation process and have uncovered molecular mechanisms that should represent in the future
attractive targets for specifically modulating NF-κB function. 相似文献
886.
887.
888.
介绍了全钒液流电池的结构、原理、特点及其发展过程,对制约全钒液流电池发展的电极材料这一关键组成作了论述.从电极材料的对比分析、电极改性方法的介绍及其电化学性能的优化机制等方面,综述了钒电池电极材料的发展过程及现状. 相似文献
889.
组织机构相当于公司的中枢神经,掌控着公司各项功能的运转.要经营好一家公司,一定要建立一套科学、合理的组织机构体系,均衡地行使各项职能,这样才能有效处理公司发展过程中遇到的问题和困难;混沌的组织机构,只会导致公司的衰退和灭亡. 相似文献
890.
<正>Dedication.This Special Issue on Parameterized Complexity of Tsinghua Science and Technology is a tribute to the influential contributions of Jianer Chen to parameterized complexity algorithmics.It is an occasion to celebrate the many important contributions to this new and prospering branch of theoretical computer science made by Jianer Chen,as he reaches the ripe young age of 60.Happy birthday,Jianer,from 相似文献