全文获取类型
收费全文 | 754947篇 |
免费 | 8217篇 |
国内免费 | 2525篇 |
专业分类
化学 | 395298篇 |
晶体学 | 11079篇 |
力学 | 35225篇 |
综合类 | 24篇 |
数学 | 94740篇 |
物理学 | 229323篇 |
出版年
2021年 | 6369篇 |
2020年 | 6973篇 |
2019年 | 7623篇 |
2018年 | 9789篇 |
2017年 | 9837篇 |
2016年 | 14789篇 |
2015年 | 9377篇 |
2014年 | 14491篇 |
2013年 | 35472篇 |
2012年 | 27039篇 |
2011年 | 33195篇 |
2010年 | 23441篇 |
2009年 | 23217篇 |
2008年 | 30137篇 |
2007年 | 30128篇 |
2006年 | 27852篇 |
2005年 | 24866篇 |
2004年 | 23112篇 |
2003年 | 20368篇 |
2002年 | 20272篇 |
2001年 | 22520篇 |
2000年 | 17254篇 |
1999年 | 13610篇 |
1998年 | 11244篇 |
1997年 | 10965篇 |
1996年 | 10614篇 |
1995年 | 9341篇 |
1994年 | 9204篇 |
1993年 | 8906篇 |
1992年 | 9832篇 |
1991年 | 10038篇 |
1990年 | 9581篇 |
1989年 | 9301篇 |
1988年 | 9178篇 |
1987年 | 9111篇 |
1986年 | 8606篇 |
1985年 | 11415篇 |
1984年 | 11595篇 |
1983年 | 9413篇 |
1982年 | 9760篇 |
1981年 | 9468篇 |
1980年 | 8988篇 |
1979年 | 9593篇 |
1978年 | 9764篇 |
1977年 | 9638篇 |
1976年 | 9543篇 |
1975年 | 9082篇 |
1974年 | 8915篇 |
1973年 | 8938篇 |
1972年 | 6217篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
3.
The European Physical Journal E - The isothermal gas adsorption of two hexane isomers (n-hexane and cyclohexane) in the mesopores of MCM-41 silica have been investigated by small angle neutron... 相似文献
4.
5.
We investigate theoretically the effects of optical absorption and saturation of the non-linear index of refraction on the
bistability of non-linear distributed feedback structures (NLDFBs). By assuming that the Kerr non-linearity saturates in an
exponential fashion, we obtain for the first time closed-form expressions for the so-called self-phase and cross-phase modulation
terms. Our investigation shows that both absorption and, in particular, saturation significantly affect the bistable properties
of this structure and in many cases eliminate this response completely. In some cases, however, saturation alters the NLDFB's
transfer characteristics in a potentially useful manner. We find that weak levels of saturation may increase the contrast
ratio between the intensities of the high and low bistable states. At increasing levels of saturation, where bistability is
no longer observed, we find regimes where the NLDFB structure could possibly be used for optical amplification.
This revised version was published online in November 2006 with corrections to the Cover Date. 相似文献
6.
The formation of singularities in the three-dimensional Euler equation is investigated. This is done by restricting the number of Fourier modes to a set which allows only for local interactions in wave number space. Starting from an initial large-scale energy distribution, the energy rushes towards smaller scales, forming a universal front independent of initial conditions. The front results in a singularity of the vorticity in finite time, and has scaling form as function of the time difference from the singularity. Using a simplified model, we compute the values of the exponents and the shape of the front analytically. The results are in good agreement with numerical simulations. 相似文献
7.
E. Jackiewicz M. Lukasiak M. Kopcewicz K. Szpila N. Bakun-Czubarow 《Hyperfine Interactions》1992,70(1-4):993-996
Terrestrial basalt rocks considered to be a good analogues of the Martian regolith were studied by using the Mössbauer spectroscopy and X-ray diffraction. The weathering of basalts was followed by the changes of the Fe2+/Fe3+ ratio. The basalt rock undergoes alteration from primary mineral composition (olivine+pyroxene+plagioclase) through smectite to kaolinite clay with oxides and hydroxides with the increase of the Fe2+/Fe3+ ratio. 相似文献
8.
S. A. Gurevich T. A. Zaraiskaya S. G. Konnikov V. M. Mikushkin S. Yu. Nikonov A. A. Sitnikova S. E. Sysoev V. V. Khorenko V. V. Shnitov Yu. S. Gordeev 《Physics of the Solid State》1997,39(10):1691-1695
The concentration and chemical state of copper in the subsurface region of Cu/SiO2 composite films obtained by simultaneous magnetron sputtering from two sources (Cu and SiO2) are determined by x-ray photoelectron spectroscopy (XPS). It is established that copper in the as-grown film is primarily in the form of unoxidized atoms dispersed in a SiO2 matrix. Annealing of the film results in practically no oxidation, but about 70% of the copper atoms condense into metallic clusters with sizes below 10 Å in the subsurface region and about 50 Å in the bulk of the film. The changes in the binding energy of core electrons, and especially in the energies of Auger electrons, are so large in this situation that photoelectron and Auger spectroscopy are efficient methods for monitoring the chemical state of this composite material. 相似文献
9.
Ya. V. Fattakhov M. F. Galyautdinov T. N. L’vova I. B. Khaibullin 《Technical Physics》1997,42(12):1457-1459
The first results regarding the formation of a two-dimensional periodic structure of local melting regions on a silicon surface
upon pulsed light irradiation are presented. The conditions are established, and the mechanism of the formation of such structures
is discussed.
Zh. Tekh. Fiz. 67, 97–99 (December 1997) 相似文献
10.
The changes in the magnetization of yttrium iron garnet (YIG) when irradiated by a pulsed neodymium laser beam with wavelength
λ=1.06 μm are investigated. Measurements are performed in the temperature range from 100 K to 600 K in various external magnetic
fields. YIG single crystals grown along the crystallographic (100), (110), and (111) directions are chosen so that the external
anisotropy of the indicated processes can be determined. Characteristic temperature intervals dominated by different mechanisms
of variation of the magnetization under the influence of a laser pulse are discussed.
Fiz. Tverd. Tela (St. Petersburg) 39, 1263–1266 (July 1997) 相似文献