全文获取类型
收费全文 | 511873篇 |
免费 | 4860篇 |
国内免费 | 1248篇 |
专业分类
化学 | 257719篇 |
晶体学 | 7561篇 |
力学 | 24221篇 |
综合类 | 13篇 |
数学 | 70382篇 |
物理学 | 158085篇 |
出版年
2021年 | 3768篇 |
2020年 | 4187篇 |
2019年 | 4523篇 |
2018年 | 12404篇 |
2017年 | 12934篇 |
2016年 | 11901篇 |
2015年 | 6203篇 |
2014年 | 8646篇 |
2013年 | 20297篇 |
2012年 | 18942篇 |
2011年 | 28675篇 |
2010年 | 19086篇 |
2009年 | 18986篇 |
2008年 | 25876篇 |
2007年 | 28394篇 |
2006年 | 16421篇 |
2005年 | 19830篇 |
2004年 | 16197篇 |
2003年 | 14600篇 |
2002年 | 12882篇 |
2001年 | 13568篇 |
2000年 | 10337篇 |
1999年 | 7953篇 |
1998年 | 6605篇 |
1997年 | 6332篇 |
1996年 | 6236篇 |
1995年 | 5561篇 |
1994年 | 5484篇 |
1993年 | 5281篇 |
1992年 | 5899篇 |
1991年 | 6008篇 |
1990年 | 5735篇 |
1989年 | 5551篇 |
1988年 | 5575篇 |
1987年 | 5458篇 |
1986年 | 5167篇 |
1985年 | 6644篇 |
1984年 | 6792篇 |
1983年 | 5388篇 |
1982年 | 5470篇 |
1981年 | 5447篇 |
1980年 | 5040篇 |
1979年 | 5449篇 |
1978年 | 5592篇 |
1977年 | 5418篇 |
1976年 | 5396篇 |
1975年 | 4963篇 |
1974年 | 4941篇 |
1973年 | 4971篇 |
1972年 | 3495篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
We develop an approach to the solution of the spinless Bethe-Salpeter equation for the different-mass case. Although the calculations are developed for spinzero particles in any arbitratry spherically symmetric potential, the non-Coulombic effective power-law potential is used as a kernel to produce the spin-averaged bound states of the non-self-conjugate mesons. The analytical formulas are also applicable to the self-conjugate mesons in the equal-mass case. The flavor-independent case is investigated in this work. The calculations are carried out to the third-order correction of the energy series. Results are consistent with those obtained before. 相似文献
22.
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
23.
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
24.
The problem of the vector and axial-vector dominance of weak interactions within the framework of the quark model of superconductivity type is discussed. 相似文献
25.
26.
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
27.
28.
29.
M. Mirvaliev 《Journal of Mathematical Sciences》1987,38(6):2357-2363
One obtains a formula for the transformation of a vector with a given covariance matrix. The sum of the squares of the components of the transformed vector is equal to a chi-square type quadratic form, constructed with the aid of the initial vector. Taking into account this property, one finds the components of the Pearson statistic, Pearson-Fisher statistic, etc.Translated from Veroyatnostnye Raspredeleniya i Matematicheskaya Statistika, pp. 337–350, 1986. 相似文献
30.
Transport as a consequence of state-dependent diffusion 总被引:1,自引:0,他引:1
M. Büttiker 《Zeitschrift für Physik B Condensed Matter》1987,68(2-3):161-167
Overdamped particles subject to a drift in a force field with sinusoidal space dependence and also a sinusoidally modulated space-dependent diffusion, with the same period as the drift, experience a net driving force. The resulting current depends on the amplitude of the modulation of the diffusion and is a periodic function of the phase difference between the sinusoidal drift and the sinusoidal modulation of the diffusion. For small modulation amplitudes a particle subject to state-dependent noise behaves the same way as a particle subject to thermal noise but with a drift which, in addition to the sinusoidal term, contains a net force term.Dedicated to Professor Harry Thomas on the occasion of his 60th birthday 相似文献