全文获取类型
收费全文 | 1690篇 |
免费 | 72篇 |
国内免费 | 4篇 |
专业分类
化学 | 872篇 |
晶体学 | 31篇 |
力学 | 104篇 |
数学 | 417篇 |
物理学 | 342篇 |
出版年
2024年 | 7篇 |
2023年 | 19篇 |
2022年 | 22篇 |
2021年 | 19篇 |
2020年 | 49篇 |
2019年 | 52篇 |
2018年 | 62篇 |
2017年 | 54篇 |
2016年 | 98篇 |
2015年 | 67篇 |
2014年 | 81篇 |
2013年 | 287篇 |
2012年 | 77篇 |
2011年 | 70篇 |
2010年 | 63篇 |
2009年 | 64篇 |
2008年 | 47篇 |
2007年 | 48篇 |
2006年 | 53篇 |
2005年 | 20篇 |
2004年 | 37篇 |
2003年 | 23篇 |
2002年 | 32篇 |
2001年 | 30篇 |
2000年 | 15篇 |
1999年 | 25篇 |
1998年 | 23篇 |
1997年 | 24篇 |
1996年 | 17篇 |
1995年 | 21篇 |
1994年 | 22篇 |
1993年 | 13篇 |
1992年 | 10篇 |
1990年 | 8篇 |
1989年 | 8篇 |
1988年 | 13篇 |
1987年 | 9篇 |
1985年 | 15篇 |
1984年 | 11篇 |
1983年 | 9篇 |
1982年 | 7篇 |
1981年 | 14篇 |
1980年 | 11篇 |
1979年 | 9篇 |
1978年 | 5篇 |
1977年 | 6篇 |
1975年 | 10篇 |
1973年 | 5篇 |
1971年 | 5篇 |
1927年 | 5篇 |
排序方式: 共有1766条查询结果,搜索用时 15 毫秒
991.
992.
993.
Purification and characterization of organic solvent stable serine alkaline protease from newly isolated Bacillus circulans M34
下载免费PDF全文
![点击此处可从《Biomedical chromatography : BMC》网站下载免费的PDF全文](/ch/ext_images/free.gif)
A protease from newly isolated Bacillus circulans M34 was purified by Q‐Sepharose anion exchange chromatography and Sepharose–bacitracin affinity chromatography followed by (NH4)2SO4 precipitation. The molecular mass of the purified enzyme was determined using SDS–PAGE. The optimum pH and temperature for protease activity were 11 and 50°C, respectively. The effect of various metal ions on protease activity was investigated. Alkaline protease from Bacillus circulans M34 wase activated by Zn2+, Cu2+ and Co2+ up to 31%. The purified protease was found to be stable in the organic solvents, surfactants and oxidizing agent. The substrate specificity of purified protease was investigated towards different substrates. The protease was almost completely inhibited by the serine protease inhibitor phenylmethanesulfonyl fluoride. The kinetic parameters of the purified protease, maximum rate (Vmax) and Michaelis constant (Km), were determined using a Lineweaver–Burk plot. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
994.
995.
Synthesis,spectral, theoretical studies and in vitro antimicrobial activities of novel diphenyltin(IV) complexes of Schiff bases derived from phenacylamine
下载免费PDF全文
![点击此处可从《应用有机金属化学》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Gökhan Şirikci Nilgün Ancın Selma Gül Öztaş Gülgün Yenişehirli Nurşen Altuntaş Öztaş 《应用有机金属化学》2014,28(7):537-544
A series of new diphenyltin(IV) complexes of the type Ph2SnL (L1: N‐phenacyl‐5‐bromosalicylideneimine, Ph2SnL1; L2: N‐phenacyl‐3,5‐dichlorosalicylideneimine, Ph2SnL2; L3: N–phenacyl‐4‐methoxysalicylideneimine, Ph2SnL3) were synthesized and characterized by elemental analysis, IR, 1H, 13C, 119Sn NMR spectroscopy and mass spectrometry techniques. The C―Sn―C angles in the complexes were calculated using equations with the 1J(117/119Sn―13C) values from 13C NMR spectra. The possible structures, NMR and electronic properties of the studied molecules were calculated through density functional theory and results compared with experimental data. All the complexes were found to be mildly active against several microorganisms and some fungi. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
996.
Alexander Pöcheim Dr. Gül Altınbaş Özpınar Prof. Dr. Thomas Müller Dr. Judith Baumgartner Prof. Dr. Christoph Marschner 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(71):17252-17260
Reaction of a 2,5-dilithiated silole with excess dichlorodimethylsilane gives the respective 2,5-bis(chlorodimethylsilyl) substituted silole. This compound can be converted to 2,5-bis(oligosilanyl) substituted siloles by addition of a suitable oligosilanide. In the UV spectra of the thus obtained compounds the lowest energy absorptions are bathochromically shifted compared to the absorptions of the two constituents, namely the 2,5-disilyl substituted silole and a trisilane. The bathochromic shift is interpreted as being caused by a mixed σ-conjugation/cross-hyperconjugation. This assumption is supported by TD-DFT calculations, which show a significant contribution from Si−Si bonds to the HOMO of the molecule. 相似文献
997.
RAVI RAMAMURTI RAINALD LÖHNER WILLIAM C. SANDBERG 《International Journal of Computational Fluid Dynamics》2013,27(1):83-99
A 3-D incompressible unsteady flow solver based on simple finite elements with adaptive remeshing and grid movement for both moving and deforming surfaces is described. We demonstrate the combination of adaptive remeshing techniques with the incompressible flow solver with the computation of flow past an eel in 2-D and a blue-fin tuna in 3-D. The flow past a swimming tuna was computed for two extreme cases of the caudal fin frequency and swimming speed. A grid refinement study was performed and a grid converged solution for the force produced by the caudal fin was obtained. 相似文献
998.
999.
In this paper, we obtain some oscillation criteria for a class of neutral difference equations with time delays. We also investigate the behavior of the eventually positive solutions of these equations. To verify our results we give various numerical simulations by using the MATLAB programming. 相似文献
1000.
We use B-spline functions to develop a numerical method for computing approximations to the solution of non-linear singular boundary value problems associated with physiology science. The original differential equation is modified at singular point then the boundary value problem is treated by using B-spline approximation. The numerical method is tested for its efficiency by considering three model problems from physiology. 相似文献