全文获取类型
收费全文 | 26241篇 |
免费 | 726篇 |
国内免费 | 172篇 |
专业分类
化学 | 14107篇 |
晶体学 | 158篇 |
力学 | 825篇 |
综合类 | 59篇 |
数学 | 3503篇 |
物理学 | 8487篇 |
出版年
2023年 | 122篇 |
2022年 | 324篇 |
2021年 | 397篇 |
2020年 | 363篇 |
2019年 | 326篇 |
2018年 | 422篇 |
2017年 | 369篇 |
2016年 | 636篇 |
2015年 | 530篇 |
2014年 | 613篇 |
2013年 | 977篇 |
2012年 | 1255篇 |
2011年 | 1587篇 |
2010年 | 940篇 |
2009年 | 838篇 |
2008年 | 1231篇 |
2007年 | 1267篇 |
2006年 | 1161篇 |
2005年 | 1588篇 |
2004年 | 1643篇 |
2003年 | 1241篇 |
2002年 | 921篇 |
2001年 | 745篇 |
2000年 | 642篇 |
1999年 | 386篇 |
1998年 | 306篇 |
1997年 | 291篇 |
1996年 | 358篇 |
1995年 | 318篇 |
1994年 | 311篇 |
1993年 | 329篇 |
1992年 | 320篇 |
1991年 | 265篇 |
1990年 | 217篇 |
1989年 | 205篇 |
1988年 | 180篇 |
1987年 | 176篇 |
1986年 | 173篇 |
1985年 | 225篇 |
1984年 | 214篇 |
1983年 | 183篇 |
1982年 | 190篇 |
1981年 | 183篇 |
1980年 | 168篇 |
1979年 | 150篇 |
1978年 | 176篇 |
1977年 | 138篇 |
1976年 | 134篇 |
1974年 | 132篇 |
1973年 | 122篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
22.
Christelle de Bellefontaine Flore Josse Martine Domurado Dominique Domurado 《Applied biochemistry and biotechnology》1994,48(2):117-123
In order to detect low levels of enzyme activity, specifically glucose oxidase, in biological samples, an immunoenzymatic assay was developed since currently available methods could not be used because of either their lack of sensitivity or the conditions prevailing in our samples: turbidity of the medium, presence of redox systems other than glucose oxidase, and high concentration of proteins. The principle of the method is to coat a polystyrene surface with a fragment Fc-specific anti-IgG, then with an antibody directed against the looked-for enzyme, which is simultaneously the antigen and the enzyme activity required for immunoenzymatic detection. We applied this concept to biological samples after glucose oxidase administration to mice. This method achieves specificity and sensitivity (20 ng/mL or 1 ng) with samples of biological origin. No marker is needed since the antigen itself possesses an enzyme activity. This method, which requires a small sample volume (50 ΜL, 20 ΜL, if necessary), can be extended easily to the many enzymes currently used as markers. It could also be applied to the native enzymes of medical interest for which antibodies and a colorimetric reaction are available. 相似文献
23.
NaY zeolite samples loaded with sodium metal by vapor phase deposition have been investigated using129Xe NMR spectroscopy. At low sodium concentration, the129Xe NMR spectrum showed three resonance lines which clearly indicate the existence of distinct domains in the zeolite sample. Such an observation suggests that the diffusion of the xenon atoms into each domain only occurs with respect to the NMR time scale (2.9 ms). As the sodium concentration increases, observation of a single broad line indicate a macroscopic homogenization of the system. The shift of this line is explained in part due to a paramagnetic interaction between the xenon atoms and the unpaired electrons of particles containing an odd number of sodium atoms. The linewidth is due to the distribution of the local magnetic fields partially averaged by the rapid motion of the xenon atoms and to the statistical distribution of the sodium particles in the supercage cavities. The paramagnetic interaction vanishes with the oxidation of the sample leading to a narrowing and a shift of the line to higher magnetic fields. 相似文献
24.
We study spectral properties of discrete Schrödinger operators with potentials obtained via dimerization of a class of aperiodic sequences. It is shown that both the nature of the autocorrelation measure of a regular sequence and the presence of generic (full probability) singular continuous spectrum in the hull of primitive and palindromic (four block substitution) potentials are robust under dimerization. Generic results also hold for circle potentials. We illustrate these results with numerical studies of the quantum mean square displacement as a function of time. The numerical techniques provide a very fast algorithm for the time evolution of wave packets. 相似文献
25.
26.
27.
J.V.P. de OliveiraA.V. Cardona M.T. VilhenaR.C. Barros 《Journal of Quantitative Spectroscopy & Radiative Transfer》2002,73(1):55-62
We describe a semi-analytical numerical method for coherent isotropic scattering time-dependent radiative transfer problems in slab geometry. This numerical method is based on a combination of two classes of numerical methods: the spectral methods and the Laplace transform (LTSN) methods applied to the radiative transfer equation in the discrete ordinates (SN) formulation. The basic idea is to use the essence of the spectral methods and expand the intensity of radiation in a truncated series of Laguerre polynomials in the time variable and then solve recursively the resulting set of “time-independent” SN problems by using the LTSN method. We show some numerical experiments for a typical model problem. 相似文献
28.
J. C. Fabris S. V. B. Gonçalves P. E. de Souza 《General Relativity and Gravitation》2002,34(12):2111-2126
The mass power spectrum for a Universe dominated by the Chaplygin gas is evaluated numerically from scales of the order of the Hubble horizon to 100 Mpc. The results are compared with a pure baryonic Universe and a cosmological constant model. In all three cases, the spectrum increases with k, the wavenumber of the perturbations. The slope of the spectrum is higher for the baryonic model and smaller for the cosmological constant model, the Chaplygin gas interpolating these two models. The results are analyzed in terms of the sound velocity of the Chaplygin gas and the moment the Universe begins to accelerate. 相似文献
29.
用Java实现网上结构图实验仿真 总被引:2,自引:0,他引:2
基于线性系统仿真的连接矩阵方法,用Java语言开发面向结构图的实验仿真程序,以Applet小应用程序的形式插入网页中运行,实现了信号与系统网上实验教学中的结构图实验仿真。经试用,程序在浏览器中运行正常,可以完成一般线性系统仿真,与以MATLAB,LABView等程序开发的实验仿真程序相比,该程序运行环境简单,几乎所有常用的Web浏览器都支持Java运行,不需另行安装相应组件。对于线性系统结构图,实现了所见即所得的图形化编程环境,具有较好的人机交互性。 相似文献
30.