全文获取类型
收费全文 | 433944篇 |
免费 | 4381篇 |
国内免费 | 1076篇 |
专业分类
化学 | 233860篇 |
晶体学 | 7179篇 |
力学 | 18916篇 |
综合类 | 19篇 |
数学 | 47017篇 |
物理学 | 132410篇 |
出版年
2019年 | 3901篇 |
2018年 | 4954篇 |
2017年 | 5019篇 |
2016年 | 7403篇 |
2015年 | 4523篇 |
2014年 | 7243篇 |
2013年 | 18462篇 |
2012年 | 13495篇 |
2011年 | 16543篇 |
2010年 | 11766篇 |
2009年 | 11604篇 |
2008年 | 15204篇 |
2007年 | 15282篇 |
2006年 | 14268篇 |
2005年 | 12909篇 |
2004年 | 11871篇 |
2003年 | 10886篇 |
2002年 | 10571篇 |
2001年 | 12294篇 |
2000年 | 9452篇 |
1999年 | 7272篇 |
1998年 | 6092篇 |
1997年 | 6078篇 |
1996年 | 5719篇 |
1995年 | 5368篇 |
1994年 | 5414篇 |
1993年 | 5000篇 |
1992年 | 6008篇 |
1991年 | 5924篇 |
1990年 | 5811篇 |
1989年 | 5682篇 |
1988年 | 5848篇 |
1987年 | 5714篇 |
1986年 | 5411篇 |
1985年 | 7108篇 |
1984年 | 7351篇 |
1983年 | 6034篇 |
1982年 | 6188篇 |
1981年 | 6180篇 |
1980年 | 5993篇 |
1979年 | 6244篇 |
1978年 | 6542篇 |
1977年 | 6525篇 |
1976年 | 6431篇 |
1975年 | 5917篇 |
1974年 | 5931篇 |
1973年 | 6037篇 |
1972年 | 4239篇 |
1968年 | 3573篇 |
1967年 | 3555篇 |
排序方式: 共有10000条查询结果,搜索用时 912 毫秒
251.
A. Hagfeldt S. Lunell H. O. G. Sieghbahn 《International journal of quantum chemistry》1994,49(2):97-104
The energy levels of small titanium oxide clusters [(TiO2)2, and (TiO2H)3, and (TiO2H)2] have been calculated using ab initio SCF methods. Both crystal and relaxed geometries have been considered. Systematic changes in the valencelevel structure resulting from geometry relaxation are found, which may be related to band-gap changes experimentally observed for small titanium oxide particles. In addition, a Ti? OH local surface state is found to be well described within a limited cluster model. © 1994 John Wiley & Sons, Inc. 相似文献
252.
Robert G. Parr 《International journal of quantum chemistry》1994,49(3):135-144
The helium atom in its ground state, subject to strong magnetic fields, is treated using a variational method. Trial functions consisting of Gaussians with nonlinear parameters variationally optimized are used. The form of these functions is a generalized s-symmetry-state properly modified to admit spatial deformation along the direction on which the magnetic field is applied. © 1994 John Wiley & Sons, Inc. 相似文献
253.
254.
255.
256.
The capability of gated saturable absorbers for single-pulse selection is studied theoretically using the classical space-time-dependent rate-equation model. The dynamics of operation is followed experimentally by the well-known pump—probe technique. Comparing the theoretical and experimental results, it is found that gated saturable absorbers can efficiently be used for pulse forming and pulse selection of pulses longer than picosecond. 相似文献
257.
E. N. Yurchenko G. E. Kramareva N. G. Zubritskaya T. P. Gaidei 《Reaction Kinetics and Catalysis Letters》1995,55(2):425-432
In the Russian Scientific Center Applied Chemistry catalysts have been developed for the gas-phase fluorination of organics, including chlorine-containing substances, hydrogenation and reductive amination of organic substances, decomposition of liquid substances to gases, complete oxidation and reduction, suitable for environment at protection. 相似文献
258.
F. G. Vagizov 《Hyperfine Interactions》1995,95(1):85-95
We present the results of an experimental investigation of a RF splitting of57Fe hyperfine lines in the regime of NMR and Mössbauer double resonance. The experiments have been performed as a function of RF field intensity and static magnetic field magnitude. The intensity of the RF components and the separation between them are extremely sensitive to the frequency and amplitude of the RF magnetic field. The RF splitting of hyperfine lines is inversely proportional to the strength of the static magnetic field. 相似文献
259.
The electrical conductivity of hydrosols of ultradispersed diamonds was studied. The electromembrane method for cleaning and concentrating of ultradispersed diamonds in hydrosols was considered. The influence exerted by the concentration of the dispersed phase on the electrical characteristics of the cleaning process was analyzed. A mathematical relation making it possible to evaluate the output characteristics of the process and to determine the geometrical characteristics of the apparatus was proposed. 相似文献
260.
The dependence of the beam propagation factor (M
2 parameter) with the absorbed pump power in the case of monolithic microchip laser under face-cooled configuration is extensively
studied. Our investigations show that the M
2 parameter is related to the absorbed pump power through two parameters (α and β) whose values depend on the laser material properties and laser configuration. We have shown that one parameter arises due
to the oscillation of higher order modes in the microchip cavity and the other parameter accounts for the spherical aberration
associated with the thermal lens induced by the pump beam. Such dependency of M
2 parameter with the absorbed pump power is experimentally verified for a face-cooled monolithic microchip laser based on Nd3+ -doped GdVO4 crystal and the values of α and β parameters were estimated from the experimentally measured data points. 相似文献