全文获取类型
收费全文 | 59450篇 |
免费 | 2022篇 |
国内免费 | 306篇 |
专业分类
化学 | 34848篇 |
晶体学 | 324篇 |
力学 | 1411篇 |
综合类 | 6篇 |
数学 | 9706篇 |
物理学 | 15483篇 |
出版年
2022年 | 507篇 |
2021年 | 690篇 |
2020年 | 933篇 |
2019年 | 907篇 |
2018年 | 882篇 |
2017年 | 792篇 |
2016年 | 1652篇 |
2015年 | 1357篇 |
2014年 | 1472篇 |
2013年 | 2855篇 |
2012年 | 2872篇 |
2011年 | 3244篇 |
2010年 | 2015篇 |
2009年 | 1711篇 |
2008年 | 2744篇 |
2007年 | 2540篇 |
2006年 | 2518篇 |
2005年 | 2281篇 |
2004年 | 1953篇 |
2003年 | 1571篇 |
2002年 | 1439篇 |
2001年 | 1192篇 |
2000年 | 973篇 |
1999年 | 769篇 |
1998年 | 684篇 |
1997年 | 666篇 |
1996年 | 789篇 |
1995年 | 687篇 |
1994年 | 701篇 |
1993年 | 696篇 |
1992年 | 735篇 |
1991年 | 530篇 |
1990年 | 530篇 |
1989年 | 478篇 |
1988年 | 485篇 |
1987年 | 496篇 |
1986年 | 459篇 |
1985年 | 635篇 |
1984年 | 634篇 |
1983年 | 486篇 |
1982年 | 557篇 |
1981年 | 528篇 |
1980年 | 516篇 |
1979年 | 504篇 |
1978年 | 482篇 |
1977年 | 473篇 |
1976年 | 450篇 |
1975年 | 424篇 |
1974年 | 420篇 |
1967年 | 474篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
The electrochemical reduction of 1-([(4-halophenyl)imino]methyl)-2-naphthols on graphite electrodes was studied using cyclic voltammetry, chronoamperometry, constant-potential coulometry and preparative constant-potential electrolysis techniques. The data revealed that the reduction on graphite was irreversible and followed an EC mechanism. The diffusion coefficients and the number of electrons transferred were determined using the chronoamperometric Cottrell slope and the ultramicro disc Pt-electrode steady-state current. The number of electrons was also determined by bulk electrolysis. The compounds were subjected to constant-potential preparative electrolysis and the electrolysis products were purified and identified by spectroscopic methods. Based on these findings, a mechanism for the electro-reduction process is proposed. 相似文献
72.
73.
We consider a spinning charge coupled to the Maxwell field. Through the appropriate symmetry in the initial conditions the charge remains at rest. We establish that any time-dependent finite energy solution converges to a sum of a soliton wave and an outgoing free wave. The convergence holds in global energy norm. Under a small constant external magnetic field the soliton manifold is stable in local energy seminorms and the evolution of the angular velocity is guided by an effective finite-dimensional dynamics. The proof uses a non-autonomous integral inequality method. 相似文献
74.
75.
76.
77.
Selecting, modifying or creating appropriate problems for mathematics class has become an activity of increaing importance in the professional development of German mathematics teachers. But rather than asking in general: “What is a good problem?” there should be a stronger emphasis on considering the specific goal of a problem, e.g.: “What are the ingredients that make a problem appropriate for initiating a learning process” or “What are the characteristics that make a problem appropriate for its use in a central test?” We propose a guiding scheme for teachers that turns out to be especially helpful, since the newly introduced orientation on outcome standards a) leads to a critical predominance of test items and b) expects teachers to design adequate problems for specific learning processes (e.g. problem solving, reasoning and modelling activities). 相似文献
78.
A. Hoffknecht O. Uwira A. Frank S. Schennach W. Spies M. Wagner S. Schippers A. Müller R. Becker M. Kleinod N. Angert P.H. Mokler 《Hyperfine Interactions》1998,114(1-4):257-261
The origin of the widely observed enhancement of rates for electron-ion recombination at very low energies is still unknown.
We investigated the recombination of Au25+ with free electrons in a merged-beams experiment at the UNILAC accelerator of the GSI in Darmstadt. At E
rel= 0 eV we found an enormous enhancement factor of 365 compared to the theory of radiative recombination. An increase of the
electron density by a factor of 10 had not much influence on the measured rate coefficient.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
79.
80.
S. Pumplün 《manuscripta mathematica》1998,97(1):93-108
For a Brauer–Severi variety X over a field k of characteristic not two, every symmetric bilinear space over X up to Witt equivalence is defined over k.
Received: 2 February 1998 相似文献