全文获取类型
收费全文 | 246790篇 |
免费 | 1884篇 |
国内免费 | 759篇 |
专业分类
化学 | 133317篇 |
晶体学 | 3859篇 |
力学 | 9840篇 |
综合类 | 8篇 |
数学 | 26652篇 |
物理学 | 75757篇 |
出版年
2021年 | 2037篇 |
2020年 | 2234篇 |
2019年 | 2523篇 |
2018年 | 3633篇 |
2017年 | 3472篇 |
2016年 | 4842篇 |
2015年 | 2709篇 |
2014年 | 4412篇 |
2013年 | 10634篇 |
2012年 | 8166篇 |
2011年 | 10029篇 |
2010年 | 7235篇 |
2009年 | 7076篇 |
2008年 | 9434篇 |
2007年 | 9499篇 |
2006年 | 8831篇 |
2005年 | 7940篇 |
2004年 | 7113篇 |
2003年 | 6461篇 |
2002年 | 6301篇 |
2001年 | 7071篇 |
2000年 | 5493篇 |
1999年 | 4182篇 |
1998年 | 3546篇 |
1997年 | 3538篇 |
1996年 | 3280篇 |
1995年 | 2736篇 |
1994年 | 2784篇 |
1993年 | 2783篇 |
1992年 | 3000篇 |
1991年 | 3059篇 |
1990年 | 2963篇 |
1989年 | 2897篇 |
1988年 | 2852篇 |
1987年 | 2806篇 |
1986年 | 2670篇 |
1985年 | 3411篇 |
1984年 | 3607篇 |
1983年 | 2851篇 |
1982年 | 3146篇 |
1981年 | 3025篇 |
1980年 | 2766篇 |
1979年 | 3062篇 |
1978年 | 3157篇 |
1977年 | 3192篇 |
1976年 | 3192篇 |
1975年 | 2991篇 |
1974年 | 2952篇 |
1973年 | 3108篇 |
1972年 | 2133篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
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
12.
The theory of tree-growing (RECPAM approach) is developed for outcome variables which are distributed as the canonical exponential family. The general RECPAM approach (consisting of three steps: recursive partition, pruning and amalgamation), is reviewed. This is seen as constructing a partition with maximal information content about a parameter to be predicted, followed by simplification by the elimination of ‘negligible’ information. The measure of information is defined for an exponential family outcome as a deviance difference, and appropriate modifications of pruning and amalgamation rules are discussed. It is further shown how the proposed approach makes it possible to develop tree-growing for situations usually treated by generalized linear models (GLIM). In particular, Poisson and logistic regression can be tree-structured. Moreover, censored survival data can be treated, as in GLIM, by observing a formal equivalence of the likelihood under random censoring and an appropriate Poisson model. Three examples are given of application to Poisson, binary and censored survival data. 相似文献
13.
14.
15.
Supposa that f(x) is a quasidifferentiable function, defined on S(?)R~n where S is an open set, with a -equivalent bounded quasidifferential subfam ily. Lenma I 相似文献
16.
Mark L. Agranovsky E. K. Narayanan 《Proceedings of the American Mathematical Society》2006,134(7):2117-2123
A test for a function to be a solution of an elliptic PDE is given in terms of extensions, as solutions, from the boundaries inside the domains belonging to an isotopic family. It generalizes a result of Ehrenpreis for spheres moved along a straight line.
17.
M. V. Kartikeyan G. Singh E. Borie B. Piosczyk M. Thumm 《International Journal of Infrared and Millimeter Waves》2006,27(5):657-670
The feasibility of an 84 GHz, 500 kW, CW gyrotron for ECRH on an experimental tokamak will be presented in this paper. Mode
competition and mode selection procedures are carefully investigated by considering various candidate modes and the TE10,4 mode is chosen as the operating mode. A conventional cylindrical cavity resonator with weak input and output tapers and parabolic
roundings is considered for interaction studies. Self-consistent, both single mode and time-dependent, calculations are carried
out and power and efficiencies are computed for a typical set of beam parameters. The results show that an output power of
well over 500 kW, CW and efficiency around 40% can be reached without a depressed collector. 相似文献
18.
J. C. Fabris S. V. B. Gonçalves P. E. de Souza 《General Relativity and Gravitation》2002,34(12):2111-2126
The mass power spectrum for a Universe dominated by the Chaplygin gas is evaluated numerically from scales of the order of the Hubble horizon to 100 Mpc. The results are compared with a pure baryonic Universe and a cosmological constant model. In all three cases, the spectrum increases with k, the wavenumber of the perturbations. The slope of the spectrum is higher for the baryonic model and smaller for the cosmological constant model, the Chaplygin gas interpolating these two models. The results are analyzed in terms of the sound velocity of the Chaplygin gas and the moment the Universe begins to accelerate. 相似文献
19.
In the study of the behaviors of barriers in an enclosed field, one should take into account such phenomena as sound energy reflection, absorption, scattering and diffraction. Therefore, the study is much more difficult than that in free field. In this paper, sound barriers are classified into four kinds according to their size, number and shape. Each kind of barriers is modelled by a corresponding method based on a computer program—SOFIS. The program combines the ray-tracing technique and statistical method. The impulse response and some acoustical parameters such as sound pressure level at different positions can be calculated by the program, no matter there are a certain kind of barriers in the field or the field is empty. The ray-tracing program and the algorithms for various barriers are validated by the comparison between measurement and prediction of the reverberation room and the anechoic room of the Northwestern Polytechnic University. 相似文献
20.
Yu. K. Voron'ko A. B. Kudryavtsev V. V. Osiko E. V. Sorokin 《Journal of Applied Spectroscopy》1991,55(4):953-957
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 55, No. 4, pp. 535–540, October, 1991. 相似文献