全文获取类型
收费全文 | 134455篇 |
免费 | 9005篇 |
国内免费 | 17692篇 |
专业分类
化学 | 110479篇 |
晶体学 | 1858篇 |
力学 | 4014篇 |
综合类 | 1117篇 |
数学 | 15620篇 |
物理学 | 28064篇 |
出版年
2024年 | 206篇 |
2023年 | 1140篇 |
2022年 | 3063篇 |
2021年 | 2912篇 |
2020年 | 3496篇 |
2019年 | 4318篇 |
2018年 | 3112篇 |
2017年 | 4863篇 |
2016年 | 4535篇 |
2015年 | 3966篇 |
2014年 | 5290篇 |
2013年 | 10000篇 |
2012年 | 8752篇 |
2011年 | 7797篇 |
2010年 | 6271篇 |
2009年 | 8352篇 |
2008年 | 8564篇 |
2007年 | 8851篇 |
2006年 | 8118篇 |
2005年 | 7053篇 |
2004年 | 6722篇 |
2003年 | 5460篇 |
2002年 | 6411篇 |
2001年 | 4118篇 |
2000年 | 3782篇 |
1999年 | 3339篇 |
1998年 | 2966篇 |
1997年 | 2386篇 |
1996年 | 2104篇 |
1995年 | 1997篇 |
1994年 | 1727篇 |
1993年 | 1379篇 |
1992年 | 1331篇 |
1991年 | 897篇 |
1990年 | 728篇 |
1989年 | 707篇 |
1988年 | 572篇 |
1987年 | 437篇 |
1986年 | 383篇 |
1985年 | 334篇 |
1984年 | 331篇 |
1983年 | 179篇 |
1982年 | 297篇 |
1981年 | 289篇 |
1980年 | 310篇 |
1979年 | 320篇 |
1978年 | 265篇 |
1977年 | 196篇 |
1976年 | 175篇 |
1973年 | 94篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
The characterization of the clusters formed on alkaline hydrolysis of [PdCl4]2– was performed using17O,23Na,35Cl,133Cs NMR and UV spectroscopy. The chemical composition of the clusters was found to be [Pd(OH)2]
n
·nNaCl. No mononuclear oxo- or hydroxocomplexes were detected. The spatial structure of the clusters is stabilized by alkali metal cations.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 675–679, April, 1993. 相似文献
82.
Phase Relations and Sodium Ion Conductivity within the Quasi-binary System Na2SiF6/Na2AIF6 . The phase diagram of the Na2SiF6/Na3AlF6 system has been determined by means of x-ray powder diffraction, thermal analysis and conductivity measurements in the sub-solidus region. Na3AlF6 accomodates up to 73 mol.-% Na2SiF6 maintaining the crystal structure type. The sodium ion conductivity increases by about five orders of magnitude upon doping Na3AlF6 with Na2SiF6. 相似文献
83.
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
84.
Summary We present an approximation method of a space-homogeneous transport equation which we prove is convergent. The method is very promising for numerical computation. Comparison of a numerical computation with an exact solution is given for the Master equation. 相似文献
85.
86.
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
87.
88.
Knut Smoczyk 《Mathematische Zeitschrift》2002,240(4):849-883
We prove that symplectic maps between Riemann surfaces L, M of constant, nonpositive and equal curvature converge to minimal symplectic maps, if the Lagrangian angle for the corresponding Lagrangian submanifold in the cross product space satisfies . If one considers a 4-dimensional K?hler-Einstein manifold of nonpositive scalar curvature that admits two complex structures J, K which commute and assumes that is a compact oriented Lagrangian submanifold w.r.t. J such that the K?hler form w.r.t.K restricted to L is positive and , then L converges under the mean curvature flow to a minimal Lagrangian submanifold which is calibrated w.r.t. .
Received: 11 April 2001 / Published online: 29 April 2002 相似文献
89.
Volker Elling. 《Mathematics of Computation》2006,75(256):1721-1733
A particular case of initial data for the two-dimensional Euler equations is studied numerically. The results show that the Godunov method does not always converge to the physical solution, at least not on feasible grids. Moreover, they suggest that entropy solutions (in the weak entropy inequality sense) are not well posed.
90.