全文获取类型
收费全文 | 356072篇 |
免费 | 2375篇 |
国内免费 | 640篇 |
专业分类
化学 | 170369篇 |
晶体学 | 5410篇 |
力学 | 18521篇 |
综合类 | 9篇 |
数学 | 52541篇 |
物理学 | 112237篇 |
出版年
2019年 | 2291篇 |
2018年 | 11088篇 |
2017年 | 11869篇 |
2016年 | 8210篇 |
2015年 | 3410篇 |
2014年 | 4388篇 |
2013年 | 10777篇 |
2012年 | 12033篇 |
2011年 | 21168篇 |
2010年 | 13568篇 |
2009年 | 13463篇 |
2008年 | 18860篇 |
2007年 | 22218篇 |
2006年 | 9055篇 |
2005年 | 13927篇 |
2004年 | 10448篇 |
2003年 | 9878篇 |
2002年 | 7943篇 |
2001年 | 7474篇 |
2000年 | 5963篇 |
1999年 | 4396篇 |
1998年 | 3897篇 |
1997年 | 3861篇 |
1996年 | 3756篇 |
1995年 | 3434篇 |
1994年 | 3580篇 |
1993年 | 3266篇 |
1992年 | 3731篇 |
1991年 | 3735篇 |
1990年 | 3672篇 |
1989年 | 3540篇 |
1988年 | 3655篇 |
1987年 | 3543篇 |
1986年 | 3359篇 |
1985年 | 4444篇 |
1984年 | 4730篇 |
1983年 | 3959篇 |
1982年 | 4091篇 |
1981年 | 4017篇 |
1980年 | 3990篇 |
1979年 | 3975篇 |
1978年 | 4293篇 |
1977年 | 4140篇 |
1976年 | 4229篇 |
1975年 | 3897篇 |
1974年 | 3938篇 |
1973年 | 4127篇 |
1972年 | 2883篇 |
1971年 | 2399篇 |
1970年 | 2205篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
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
82.
83.
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
84.
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
85.
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
86.
A. E. Dorokhov 《Czechoslovak Journal of Physics》2002,52(3):C79-C90
Nonperturbative nolocal structure of QCD vacuum is well described by instanton model. Specific helicity and flavor structure of zero modes of quarks, in instanton field allows simultaneously to explain some important features of low-and high-energy hadron phenomemology. The basic characteristics of hadron spectrum, partonic sum rules, heavyquark potential etc within the instanton liquid model are briefly discussed. 相似文献
87.
The radiation emitted by charged, scalar particles in a Schwarzschild field with maximal acceleration corrections is calculated classically and in the tree approximation of quantum field theory. In both instances the particles emit radiation that has characteristics similar to those of gamma-ray bursters. 相似文献
88.
D. V. Vyalykh A. M. Shikin G. V. Prudnikova A. Yu. Grigor’ev A. G. Starodubov V. K. Adamchuk 《Physics of the Solid State》2002,44(1):164-170
This paper reports on the first experimental observation of quantum-well states and sp-type resonances in thin single-crystal gold, silver, and copper layers formed on single-crystal W(110) surfaces, which result from spatial localization of Bloch-type electronic wave functions in a quantum well with potential barriers at the vacuum/metal and metal/W(110) interfaces. The quantization of the valence-band electronic structure in Au/W(110), Ag/W(110), and Cu/W(110) systems was studied experimentally using angle-resolved photoelectron spectroscopy. 相似文献
89.
J. Berny 《The Journal of the Operational Research Society》1989,40(12):1121-1127
This paper presents an alternative to the beta continuous probability distribution for risk analysis. Particular attention has been given to two major applications of distributions, namely project management risk and critical path analysis (PERT). In conjunction with the beta, the triangular and normal distributions are frequently employed in order to give sufficient robustness to risk analysis. The beta distribution, as used in PERT, has a major theoretical implementation flaw. The new distribution was developed to give a possible alternative method of assessing risk. It is shown that the requirement to estimate the most pessimistic variate may be replaced by the probability to exceed the mode. Proposals for other simplifications in risk analysis are discussed. Practical means to validate the most appropriate distributions for risk analysis are outlined, and a cost-data case study is included. 相似文献
90.
G. L. Booth 《Acta Mathematica Hungarica》1989,54(3-4):201-208