全文获取类型
收费全文 | 28834篇 |
免费 | 703篇 |
国内免费 | 230篇 |
专业分类
化学 | 19524篇 |
晶体学 | 130篇 |
力学 | 652篇 |
综合类 | 1篇 |
数学 | 5438篇 |
物理学 | 4022篇 |
出版年
2022年 | 183篇 |
2021年 | 276篇 |
2020年 | 351篇 |
2019年 | 314篇 |
2018年 | 280篇 |
2017年 | 295篇 |
2016年 | 610篇 |
2015年 | 623篇 |
2014年 | 664篇 |
2013年 | 1425篇 |
2012年 | 1421篇 |
2011年 | 1737篇 |
2010年 | 965篇 |
2009年 | 823篇 |
2008年 | 1480篇 |
2007年 | 1478篇 |
2006年 | 1562篇 |
2005年 | 1409篇 |
2004年 | 1338篇 |
2003年 | 1113篇 |
2002年 | 1060篇 |
2001年 | 462篇 |
2000年 | 420篇 |
1999年 | 403篇 |
1998年 | 386篇 |
1997年 | 440篇 |
1996年 | 404篇 |
1995年 | 369篇 |
1994年 | 398篇 |
1993年 | 351篇 |
1992年 | 327篇 |
1991年 | 328篇 |
1990年 | 282篇 |
1989年 | 288篇 |
1988年 | 262篇 |
1987年 | 223篇 |
1986年 | 247篇 |
1985年 | 366篇 |
1984年 | 374篇 |
1983年 | 323篇 |
1982年 | 360篇 |
1981年 | 322篇 |
1980年 | 348篇 |
1979年 | 278篇 |
1978年 | 308篇 |
1977年 | 288篇 |
1976年 | 229篇 |
1975年 | 201篇 |
1974年 | 204篇 |
1973年 | 166篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Design theory crosses the boundary between mathematics and statistics, and includes a wide range of disparate types of design. In this paper we present a classification scheme which aims to include as many important types as possible, based on a balance among concept, representation and use. 相似文献
52.
Manfred Brun Peter Hubner Dieter Oelkrug 《Fresenius' Journal of Analytical Chemistry》1992,344(4-5):209-213
Summary A theoretical model is derived that describes the influence of lateral light diffusion in a scattering medium on the absorptivity of an absorber spot on top of the substrate. The model uses the lateral resolved reflectivity under point irradiation that has been analyzed experimentally with a scanning-micro-laser-reflectometer. The model allows quantification of the absorptivity by one single equation that contains only the mean radial diffusion length of light and the spot area. Experiment and theory are applied to typical substrates for thin layer chromatography (alumina, silica, cellulose). The diffusion lengths in these substrates are given and the absorptivities of the spots are calculated as a function of the spot area. 相似文献
53.
54.
Capillary gas chromatography coupled to microwave-inducedplasma detection furnishes sensitivity adequate for trace analysis when the signal is monitored at a carbon emission line. Work performed with one of these systems at high electronic gain for the carbon signal has revealed solvent band widths in excess of four minutes; these impeded quantification of peaks eluting after the solvent. This report discusses two phenomena which could be related to the unexpected intensity of this solvent response: photomultiplier tube saturation and carbon deposits in the quartz plasma discharge tube. 相似文献
55.
J. Schulte 《Journal of statistical physics》1993,70(5-6):1343-1347
The thermodynamic stability of4He4–13 at 3.2 K is investigated with the classical Monte Carlo method, with the semiclassical path-integral Monte Carlo (PIMC) method, and with the semiclassical all-order many-body method. In the all-order many-body simulation the dipole-dipole approximation including short-range correction is used. The resulting stability plots are discussed and related to recent TOF experiments by Stephens and King. It is found that with classical Monte Carlo of course the characteristics of the measured mass spectrum cannot be resolved. With PIMC, switching on more and more quantum mechanics. by raising the number of virtual time steps results in more structure in the stability plot, but this did not lead to sufficient agreement with the TOF experiment. Only the all-order many-body method resolved the characteristic structures of the measured mass spectrum, including magic numbers. The result shows the influence of quantum statistics and quantum mechanics on the stability of small neutral helium clusters. 相似文献
56.
The transmission and diffraction of radiation through dense monolayers of monodisperse opaque spheres were studied for the Fraunhofer domain. Theoretical considerations, numerical calculations and experiments on ultrasonic transmission and on laser light transmission and diffraction yielded corresponding results. Complementary studies included the cases of sterically non-interacting particles (by numerical simulation) and of small particle size parameters (by ultrasonic extinction). Transmission was found to be, in general, a non-linear function of the monolayer density. Secondary effects on the transmission can be attributed to the effect of the monolayer structure (characterized by the pair correlation function) on the angular distribution of diffracted intensity. The results were found to be in accordance with experimental results on extinction in three-dimensional systems. 相似文献
57.
Graham R. Knox Peter L. Pauson Debra Willison 《Journal of organometallic chemistry》1993,450(1-2):177-184
Phenylazoferrocene undergoes nickelation and palladation exclusively on the phenyl group. Lithium phenylazocyclopentadienide has been converted into derivatives of Mo, Mn, Fe, Ru and Rh. 相似文献
58.
59.
W. Hoheisel U. Schulte M. Vollmer F. Träger 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1991,20(1):381-383
This paper reports new results on the optical spectra of Na particles and on laser-induced photodissociation of Na atoms from the surface of these particles. In continuation of our earlier studies we have performed experiments to elucidate the mechanism of thenonthermal dissociation process. Furthermore, theoretical calculations have been carried out with the goal to correlate the wavelength dependence of the photodissociation yield with the optical absorption spectra of the metal particles. In addition, manipulation of the size distribution of metal particles on supports is outlined as an application of the effect. This allows for the preparation of very special surfaces with novel physical and chemical properties. 相似文献
60.