全文获取类型
收费全文 | 3135篇 |
免费 | 125篇 |
国内免费 | 24篇 |
专业分类
化学 | 2105篇 |
晶体学 | 19篇 |
力学 | 98篇 |
数学 | 528篇 |
物理学 | 534篇 |
出版年
2023年 | 21篇 |
2022年 | 62篇 |
2021年 | 71篇 |
2020年 | 72篇 |
2019年 | 79篇 |
2018年 | 74篇 |
2017年 | 57篇 |
2016年 | 117篇 |
2015年 | 96篇 |
2014年 | 137篇 |
2013年 | 231篇 |
2012年 | 235篇 |
2011年 | 316篇 |
2010年 | 161篇 |
2009年 | 138篇 |
2008年 | 222篇 |
2007年 | 194篇 |
2006年 | 181篇 |
2005年 | 144篇 |
2004年 | 118篇 |
2003年 | 101篇 |
2002年 | 96篇 |
2001年 | 47篇 |
2000年 | 41篇 |
1999年 | 19篇 |
1998年 | 24篇 |
1997年 | 20篇 |
1996年 | 22篇 |
1995年 | 15篇 |
1994年 | 20篇 |
1993年 | 22篇 |
1992年 | 15篇 |
1991年 | 8篇 |
1988年 | 3篇 |
1987年 | 4篇 |
1985年 | 11篇 |
1984年 | 5篇 |
1983年 | 6篇 |
1982年 | 6篇 |
1981年 | 6篇 |
1979年 | 4篇 |
1978年 | 9篇 |
1977年 | 3篇 |
1976年 | 4篇 |
1975年 | 3篇 |
1974年 | 3篇 |
1973年 | 3篇 |
1961年 | 3篇 |
1942年 | 6篇 |
1940年 | 3篇 |
排序方式: 共有3284条查询结果,搜索用时 15 毫秒
1.
2.
The influence of different referencing methods on the accuracy of δ13C value measurement of ethanol fuel by gas chromatography/combustion/isotope ratio mass spectrometry 下载免费PDF全文
3.
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
4.
5.
6.
Ozonolysis of a Series of Methylated Alkenes: Reaction Rate Coefficients and Gas‐Phase Products 下载免费PDF全文
Tristan Braure Véronique Riffault Alexandre Tomas Romeo Iulian Olariu Cecilia Arsene Yuri Bedjanian Patrice Coddeville 《国际化学动力学杂志》2015,47(9):596-605
The gas‐phase ozonolysis of three methylated alkenes, i.e., trans‐2,2‐dimethyl‐3‐hexene (22dM3H), trans‐2,5‐dimethyl‐3‐hexene (25dM3H), and 4‐methyl‐1‐pentene (4M1P), has been investigated in the presence of sufficient hydroxyl radical scavenger in a laminar flow reactor at ambient temperature (296 ± 2 K) and P = 1 atm of dry air (RH ≤ 5%). Ozone levels in the reactor were monitored by an automatic analyzer. Alkene and gas‐phase product concentrations were determined via online sampling either on three‐bed adsorbent cartridges followed by thermodesorption and GC/FID‐MS analysis or on 2,4‐dinitrophenylhydrazine (DNPH) cartridges for subsequent HPLC/UV analysis. Reaction rate coefficients of (3.38 ± 0.12) × 10?17 for 22dM3H and (2.71 ± 0.26) × 10?17 for 25dM3H, both in cm3 molecule?1 s?1 units, have been obtained under pseudo–first‐order conditions. Primary carbonyl products have been identified for the three investigated alkenes, and branching ratios are reported. In the case of 4M1P ozonolysis, the yield of a Criegee intermediate was indirectly determined. Kinetics and product study results are compared to those of literature when available. This work represents the first investigation of reaction products in the ozonolysis of 22dM3H, 25dM3H, and 4M1P in a flow reactor. 相似文献
7.
8.
9.
10.
Alexandre Munnier 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》2003,9(2):977-1000
This article deals with stability and small linear
oscillations of liquid bridges between fixed solid surfaces
(parallel plates, spheres, ...) under zero gravity. A general
investigation method for any kind of axisymmetric liquid bridge is
exposed but the author focus his work on the spherical liquid
bridge cases. In particular, he exposes a full theoretical study
of spherical liquid bridges between two spheres, plates and
cones. 相似文献