全文获取类型
收费全文 | 25505篇 |
免费 | 5篇 |
国内免费 | 218篇 |
专业分类
化学 | 7677篇 |
晶体学 | 217篇 |
力学 | 1849篇 |
数学 | 8078篇 |
物理学 | 7907篇 |
出版年
2022年 | 7篇 |
2020年 | 7篇 |
2018年 | 1976篇 |
2017年 | 2236篇 |
2016年 | 970篇 |
2015年 | 632篇 |
2014年 | 520篇 |
2013年 | 798篇 |
2012年 | 1803篇 |
2011年 | 1057篇 |
2010年 | 39篇 |
2009年 | 140篇 |
2008年 | 119篇 |
2007年 | 112篇 |
2006年 | 121篇 |
2005年 | 5821篇 |
2004年 | 5628篇 |
2003年 | 3087篇 |
2002年 | 269篇 |
2001年 | 23篇 |
2000年 | 15篇 |
1999年 | 19篇 |
1998年 | 32篇 |
1997年 | 15篇 |
1996年 | 11篇 |
1995年 | 11篇 |
1994年 | 8篇 |
1993年 | 12篇 |
1992年 | 17篇 |
1991年 | 10篇 |
1990年 | 8篇 |
1989年 | 23篇 |
1988年 | 16篇 |
1987年 | 14篇 |
1986年 | 14篇 |
1985年 | 5篇 |
1984年 | 5篇 |
1983年 | 8篇 |
1982年 | 5篇 |
1981年 | 9篇 |
1979年 | 6篇 |
1978年 | 10篇 |
1977年 | 10篇 |
1976年 | 8篇 |
1975年 | 11篇 |
1973年 | 8篇 |
1972年 | 7篇 |
1971年 | 6篇 |
1970年 | 5篇 |
1960年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
The present paper reports on exfoliated graphite (EG) used for the cyclic electrochemical process of phenol oxidation in alkaline solution. It is shown that the electrochemical activity of anode-produced EG decreases considerably in the second cycle due to the deposition of an oligomer film, composed of the products of phenol oxidation, on the EG surface. Thermal treatment of the inactive graphite anode in air at 500 °C provided a regenerated material of activity three times higher for the first cycle and 2.6 times higher for three cycles as compared to the original anode. The reason for such a behavior is assigned to a carbon film formed on the EG surface during the carbonization/oxidation processes involving the products of phenol oxidation. Comparative studies showed that electroactivity of the original EG can also be enhanced if before the process of phenol oxidation the original EG is activated by heat treatment. Unfortunately, the electrochemical activity of the product of such a treatment is higher only for the first cycle of phenol oxidation and drops dramatically in the following cycles.Contribution to the 3rd Baltic Conference on Electrochemistry, Gdask-Sobieszewo, 23–26 April 2003. Dedicated to the memory of Harry B. Mark, Jr. (28 February 1934–3 March 2003) 相似文献
42.
43.
The discovery of selective cyclooxygenase-2 (COX-2) inhibitors represents a major achievement of the efforts over the past few decades to develop therapeutic treatments for inflammation. To gain insights into designing new COX-2-selective inhibitors, we address the energetic and structural basis for the selective inhibition of COX isozymes by means of a combined computational protocol involving docking experiment, force field design for the heme prothetic group, and free energy perturbation (FEP) simulation. We consider both COX-2- and COX-1-selective inhibitors taking the V523I mutant of COX-2 to be a relevant structural model for COX-1 as confirmed by a variety of experimental and theoretical evidences. For all COX-2-selective inhibitors under consideration, we find that free energies of binding become less favorable as the receptor changes from COX-2 to COX-1, due to the weakening and/or loss of hydrogen bond and hydrophobic interactions that stabilize the inhibitors in the COX-2 active site. On the other hand, COX-1-selective oxicam inhibitors gain extra stabilization energy with the change of residue 523 from valine to isoleucine because of the formations of new hydrogen bonds in the enzyme-inhibitor complexes. The utility of the combined computational approach, as a valuable tool for in silico screening of COX-2-selective inhibitors, is further exemplified by identifying the physicochemical origins of the enantiospecific selective inhibition of COX-2 by -substituted indomethacin ethanolamide inhibitors. 相似文献
44.
45.
46.
N. A. Malysheva A. I. Prokof'ev N. N. Bubnov S. P. Solodovnikov T. I. Prokof'eva V. B. Vol'eva V. V. Ershov M. I. Kabachnik 《Russian Chemical Bulletin》1988,37(5):907-914
1. | Conformational transitions characteristic of nonplanar rings were detected in the radical-cation of the 3,6-di-tert-butylpyrocatechol ester of ethylene glycol. |
2. | Cyclic radical-cations are formed during the oxidation of 2-acyloxyphenols. |
47.
48.
Th.?Monovasilis Z.?Kalogiratou T.E.?SimosEmail author 《Journal of mathematical chemistry》2005,37(3):263-270
The computation of the energy eigenvalues of the one-dimensional time-independent Schrödinger equation is considered. Exponentially fitted and trigonometrically fitted symplectic integrators are obtained, by modification of the first and second order Yoshida symplectic methods. Numerical results are obtained for the one-dimensional harmonic oscillator and Morse potential.AMS subject classification: 65L15Funding by research project 71239 of Prefecture of Western Macedonia and the E.U. is gratefully acknowledged. 相似文献
49.
Xianfeng?You Feng?Chen Jinlong?ZhangEmail author 《Journal of Sol-Gel Science and Technology》2005,34(2):181-187
TiO2 powders were prepared by sol–gel template method and calcined under different conditions. XRD, BET and TEM were used to characterize the TiO2 powders obtained. The photocatalytic activity of TiO2 was investigated by the degradation of methyl orange. It was found that TiO2 powder has the highest photocatalytic activity at a calcination temperature of 673 K. The effects of physical properties such as surface area, crystallinity and crystal phase on the photocatalytic activity of TiO2 were discussed. 相似文献
50.