全文获取类型
收费全文 | 583669篇 |
免费 | 10161篇 |
国内免费 | 5861篇 |
专业分类
化学 | 303130篇 |
晶体学 | 8336篇 |
力学 | 29781篇 |
综合类 | 339篇 |
数学 | 76052篇 |
物理学 | 182053篇 |
出版年
2021年 | 6391篇 |
2020年 | 7109篇 |
2019年 | 7870篇 |
2018年 | 10022篇 |
2017年 | 9989篇 |
2016年 | 13658篇 |
2015年 | 7930篇 |
2014年 | 12752篇 |
2013年 | 26741篇 |
2012年 | 21904篇 |
2011年 | 25433篇 |
2010年 | 19135篇 |
2009年 | 18990篇 |
2008年 | 23544篇 |
2007年 | 23077篇 |
2006年 | 21050篇 |
2005年 | 18779篇 |
2004年 | 17345篇 |
2003年 | 15556篇 |
2002年 | 15570篇 |
2001年 | 16276篇 |
2000年 | 12583篇 |
1999年 | 9828篇 |
1998年 | 8596篇 |
1997年 | 8279篇 |
1996年 | 7763篇 |
1995年 | 6974篇 |
1994年 | 7018篇 |
1993年 | 6706篇 |
1992年 | 6989篇 |
1991年 | 7453篇 |
1990年 | 7173篇 |
1989年 | 7002篇 |
1988年 | 6749篇 |
1987年 | 6523篇 |
1986年 | 6255篇 |
1985年 | 7838篇 |
1984年 | 8164篇 |
1983年 | 6896篇 |
1982年 | 7158篇 |
1981年 | 6630篇 |
1980年 | 6294篇 |
1979年 | 6845篇 |
1978年 | 7088篇 |
1977年 | 6973篇 |
1976年 | 7003篇 |
1975年 | 6682篇 |
1974年 | 6510篇 |
1973年 | 6834篇 |
1972年 | 5061篇 |
排序方式: 共有10000条查询结果,搜索用时 562 毫秒
951.
952.
953.
A lithium(I) coordination polymer has been formed from LiClO4 and the 2,2′‐bipyrimidine (bpym) ligand in which each square pyramidal lithium(I) atom is coordinated in the basal plane by four nitrogen donor atoms derived from two bpym ligands and one water molecule at the apical position. These are connected into a layer structure via hydrogen‐bonding interactions involving the perchlorate anions. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
954.
955.
Blokhina S. V. Bykova V. V. Sharapova A. V. Ol'khovich M. V. Trostin A. N. 《Russian Journal of General Chemistry》2003,73(2):257-259
The sorption properties of stationary phases based on nematic p-substituted azoxybenzenes were studied. Correlations were revealed between the structural selectivity of mesogens, chemical nature of terminal substituents, capability for dispersion interactions and polarity of the sorbents, temperature gradient of the retention indices, and thermodynamic parameters of solution of xylene isomers in the sorbents. 相似文献
956.
Amorphization of Al32Ge68 at normal pressure, starting from the thermobarically quenched high-pressure crystalline metallic γ-phase, was studied in a slow heating run by performing NMR field-sweep experiments. In the temperature interval from 77 to 300 K the 27Al central line exhibits a continuous broadening and a positive frequency shift. Close to 300 K rather abrupt changes were observed, where the shift changed its sign, and the line width jumped to its highest value. The discontinuous course of the phase changes indicates that the amorphization process proceeds via a sequence of intermediate metastable states, which can be ‘overheated’ in a slow heating run and consequently transform in an explosion-like manner to the final amorphous state at a well-defined temperature. The frequency shift could be decomposed into the negative second-order quadrupolar shift and the positive Knight shift. The change of the shift sign from positive to negative at 300 K reflects the vanishing tendency of the Knight shift upon heating and is compatible with the conduction-electron localization upon structure amorphization. 相似文献
957.
A group representation of radiation propagation in an anisotropic medium is developed. The system of wave equations for electromagnetic potentials, obtained from the Maxwell equations with account for the constitutive equations, has been factorized. It is shown that the linear differential operator of the factorized system is orthogonal in transparent crystals and unitary in gyrotropic ones and is represented through the momentum operator. On the basis of the commutation relations for the components of this operator, the eigenvalue problem has been solved and the expression for the change in the radiant energy in the crystal in the form of spherical waves has been obtained. The dependences of the ray and phase velocities and the polarization vectors of waves on the birefringence anisotropy and gyrotropy as well as on the angular momentum, displacement current, and bound charge determining them have been analyzed. It has been established that in the general case of gyrotropic crystals where the nonreciprocity phenomenon takes place and in magnetoelectrics Maxwell equations are represented in a form similar to the Dirac equations and the electromagnetic radiation is correctly described by means of bispinors and is quantized as fermions. 相似文献
958.
959.
A tomographic reconstruction method based on Monte Carlo random searching guided by the information contained in the projections
of radiographed objects is presented. In order to solve the optimization problem, a multiscale algorithm is proposed to reduce
computation. The reconstruction is performed in a coarse-to-fine multigrid scale that initializes each resolution level with
the reconstruction of the previous coarser level, which substantially improves the performance. The method was applied to
a real case reconstructing the internal structure of a small metallic object with internal components, showing excellent results. 相似文献
960.
The influence of the well width fluctuations on the dependence of the binding energy of excitonic complexes in quantum wells is studied by using the path-integral Monte-Carlo technique. The results are compared with available experimental data and a good agreement is found.Postdoctoral researcher of FWO-Vlaanderen 相似文献