全文获取类型
收费全文 | 18839篇 |
免费 | 526篇 |
国内免费 | 359篇 |
专业分类
化学 | 11785篇 |
晶体学 | 110篇 |
力学 | 570篇 |
综合类 | 30篇 |
数学 | 2790篇 |
物理学 | 4439篇 |
出版年
2022年 | 248篇 |
2021年 | 275篇 |
2020年 | 273篇 |
2019年 | 267篇 |
2018年 | 258篇 |
2017年 | 203篇 |
2016年 | 500篇 |
2015年 | 442篇 |
2014年 | 535篇 |
2013年 | 1045篇 |
2012年 | 939篇 |
2011年 | 1039篇 |
2010年 | 667篇 |
2009年 | 689篇 |
2008年 | 922篇 |
2007年 | 954篇 |
2006年 | 774篇 |
2005年 | 776篇 |
2004年 | 771篇 |
2003年 | 721篇 |
2002年 | 715篇 |
2001年 | 486篇 |
2000年 | 439篇 |
1999年 | 342篇 |
1998年 | 262篇 |
1997年 | 239篇 |
1996年 | 270篇 |
1995年 | 260篇 |
1994年 | 257篇 |
1993年 | 198篇 |
1992年 | 201篇 |
1991年 | 197篇 |
1990年 | 215篇 |
1989年 | 174篇 |
1988年 | 159篇 |
1987年 | 153篇 |
1986年 | 138篇 |
1985年 | 251篇 |
1984年 | 258篇 |
1983年 | 184篇 |
1982年 | 208篇 |
1981年 | 164篇 |
1980年 | 171篇 |
1979年 | 151篇 |
1978年 | 135篇 |
1977年 | 176篇 |
1976年 | 156篇 |
1975年 | 121篇 |
1974年 | 121篇 |
1973年 | 118篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
Triesterase and Promiscuous Diesterase Activities of a Di‐CoII‐Containing Organophosphate Degrading Enzyme Reaction Mechanisms 下载免费PDF全文
Dr. Marta E. Alberto Gaspar Pinto Prof. Nino Russo Dr. Marirosa Toscano 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(9):3736-3745
The reaction mechanism for the hydrolysis of trimethyl phosphate and of the obtained phosphodiester by the di‐CoII derivative of organophosphate degrading enzyme from Agrobacterium radiobacter P230(OpdA), have been investigated at density functional level of theory in the framework of the cluster model approach. Both mechanisms proceed by a multistep sequence and each catalytic cycle begins with the nucleophilic attack by a metal‐bound hydroxide on the phosphorus atom of the substrate, leading to the cleavage of the phosphate‐ester bond. Four exchange‐correlation functionals were used to derive the potential energy profiles in protein environments. Although the enzyme is confirmed to work better as triesterase, as revealed by the barrier heights in the rate‐limiting steps of the catalytic processes, its promiscuous ability to hydrolyze also the product of the reaction has been confirmed. The important role played by water molecules and some residues in the outer coordination sphere has been elucidated, while the binuclear CoII center accomplishes both structural and catalytic functions. To correctly describe the electronic configuration of the d shell of the metal ions, high‐ and low‐spin arrangement jointly with the occurrence of antiferromagnetic coupling, have been herein considered. 相似文献
2.
The Effect of the Spacer of Bis(biurea) Ligands on the Structure of A2L3‐type (A=anion) Phosphate Complexes 下载免费PDF全文
Prof. Biao Wu Dr. Shaoguang Li Prof. Yibo Lei Prof. Huaiming Hu Dr. Nader de Sousa Amadeu Prof. Dr. Christoph Janiak Dr. Jennifer S. Mathieson Dr. De‐Liang Long Prof. Leroy Cronin Prof. Xiao‐Juan Yang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(6):2588-2593
By tuning the length and rigidity of the spacer of bis(biurea) ligands L, three structural motifs of the A2L3 complexes (A represents anion, here orthophosphate PO43?), namely helicate, mesocate, and mono‐bridged motif, have been assembled by coordination of the ligand to phosphate anion. Crystal structure analysis indicated that in the three complexes, each of the phosphate ions is coordinated by twelve hydrogen bonds from six surrounding urea groups. The anion coordination properties in solution have also been studied. The results further demonstrate the coordination behavior of phosphate ion, which shows strong tendency for coordination saturation and geometrical preference, thus allowing for the assembly of novel anion coordination‐based structures as in transition‐metal complexes. 相似文献
3.
Functional Binding Surface of a β‐Hairpin VEGF Receptor Targeting Peptide Determined by NMR Spectroscopy in Living Cells 下载免费PDF全文
Dr. Donatella Diana Anna Russomanno Dr. Lucia De Rosa Dr. Rossella Di Stasi Dr. Domenica Capasso Dr. Sonia Di Gaetano Dr. Alessandra Romanelli Dr. Luigi Russo Dr. Luca D. D'Andrea Prof. Roberto Fattorusso 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(1):91-95
In this study, the functional interaction of HPLW peptide with VEGFR2 (Vascular Endothelial Growth Factor Receptor 2) was determined by using fast 15N‐edited NMR spectroscopic experiments. To this aim, 15N uniformly labelled HPLW has been added to Porcine Aortic Endothelial Cells. The acquisition of isotope‐edited NMR spectroscopic experiments, including 15N relaxation measurements, allowed a precise characterization of the in‐cell HPLW epitope recognized by VEGFR2. 相似文献
4.
5.
6.
7.
8.
9.
Zuo LIU Zhen De WU 《数学学报(英文版)》2005,21(5):997-1000
Let κ be non-negative integer. The unoriented bordism classes, which can be represented as [RP(ξ^κ)] where ξ^κ is a k-plane bundle, form an ideal of the unoriented bordism ring MO.. A group of generators of this ideal expressed by a base of MO. and a necessary and sufficient condition for a bordism class to belong to this ideal are given. 相似文献
10.
In this paper we obtain a number of Maharam-type slice integral representations, with respect to scalar measures, for positive
projections in Dedekind complete vector lattices and f-algebras.
AMS Classification: 47B65, 46A40, 06F25 相似文献