全文获取类型
收费全文 | 1866篇 |
免费 | 65篇 |
国内免费 | 69篇 |
专业分类
化学 | 879篇 |
晶体学 | 10篇 |
力学 | 68篇 |
综合类 | 2篇 |
数学 | 464篇 |
物理学 | 577篇 |
出版年
2023年 | 11篇 |
2022年 | 44篇 |
2021年 | 56篇 |
2020年 | 51篇 |
2019年 | 52篇 |
2018年 | 51篇 |
2017年 | 55篇 |
2016年 | 76篇 |
2015年 | 43篇 |
2014年 | 59篇 |
2013年 | 95篇 |
2012年 | 69篇 |
2011年 | 100篇 |
2010年 | 74篇 |
2009年 | 69篇 |
2008年 | 60篇 |
2007年 | 54篇 |
2006年 | 74篇 |
2005年 | 78篇 |
2004年 | 142篇 |
2003年 | 129篇 |
2002年 | 87篇 |
2001年 | 78篇 |
2000年 | 23篇 |
1999年 | 18篇 |
1998年 | 29篇 |
1997年 | 22篇 |
1996年 | 11篇 |
1995年 | 7篇 |
1994年 | 10篇 |
1993年 | 25篇 |
1992年 | 23篇 |
1991年 | 15篇 |
1990年 | 10篇 |
1989年 | 13篇 |
1988年 | 23篇 |
1987年 | 9篇 |
1986年 | 6篇 |
1985年 | 8篇 |
1984年 | 11篇 |
1983年 | 9篇 |
1982年 | 6篇 |
1981年 | 6篇 |
1978年 | 8篇 |
1977年 | 12篇 |
1976年 | 11篇 |
1975年 | 5篇 |
1974年 | 8篇 |
1973年 | 8篇 |
1911年 | 4篇 |
排序方式: 共有2000条查询结果,搜索用时 15 毫秒
1.
In this paper, a two-dimensional finite volume unstructured mesh method (FVUM) based on a triangular background interpolation mesh is developed for analysing the evolution of the saltwater intrusion into single and multiple coastal aquifer systems. The model formulation consists of a ground-water flow equation and a salt transport equation. These coupled and non-linear partial differential equations are transformed by FVUM into a system of differential/algebraic equations, which is solved using backward differentiation formulas of order one through five. Simulation results are compared with previously published solutions where good agreement is observed. 相似文献
2.
The OPAL Collaboration G. Abbiendi et al. 《The European Physical Journal C - Particles and Fields》2003,27(3):311-329
This paper describes topological searches for neutral scalar bosons S0 produced in association with a Z0 boson via the Bjorken process at centre-of-mass energies of 91 GeV and 183-209 GeV. These searches are based on studies of the recoil mass spectrum of
and events and on a search for with and S or photons. They cover the decays of the S0 into an arbitrary combination of hadrons, leptons, photons and invisible particles as well as the possibility that it might
be stable.
No indication for a signal is found in the data and upper limits on the cross section of the Bjorken process are calculated.
Cross-section limits are given in terms of a scale factor k with respect to the Standart Model cross section for the Higgs-strahlung process .
These results can be interpreted in general scenarios independently of the decay modes of the S0. The examples considered here are the production of a single new scalar particle with a decay width smaller than the detector
mass resolution, and for the first time, two scenarios with continuous mass distributions, due to a single very broad state
or several states close in mass.
Received: 13 March 2002 / Published online: 19 February 2003 相似文献
3.
4.
5.
Yu. A. Mitropol’skii Nguyen Dong Anh Nguyen Dyk Tynh 《Ukrainian Mathematical Journal》1998,50(11):1731-1737
We construct the second approximation for random oscillations described by the Van der Pol equation which are under the action
of a broadband random process.
Translated from Ukrainskii Matematicheskii Zhurnal, Vol. 50, No. 11, pp. 1517–1521, November, 1998. 相似文献
6.
7.
8.
9.
全固态多波长飞秒脉冲激光系统 总被引:1,自引:1,他引:0
利用棱镜对引进频谱空间啁啾来补偿飞秒脉冲激光二次谐波产生中的相位失配,提高了倍频效率建立了一套全固态、多波长(1065nm, 532nm,823.1nm, 402nm)飞秒脉冲激光系统自制的Nd:YVO4激光器输出532nm绿光激光,最高平均功率可达5.6W当用2.5W绿光激光泵浦时,从自制的钛宝石激光器及经BBO倍频可分别输出中心波长为823.1nm和402nm,平均功率300mW和73mW,谱宽32.3nm和5.1nm,脉宽22fs和33.3fs、重复率108MHz的近红外和蓝光激光整个系统具有结构紧凑、倍频效率高、运行稳定的特点. 相似文献
10.
Pham Huu Anh Ngoc 《Journal of Differential Equations》2007,243(1):101-122
We study stability radii of linear Volterra-Stieltjes equations under multi-perturbations and affine perturbations. A lower and upper bound for the complex stability radius with respect to multi-perturbations are given. Furthermore, in some special cases concerning the structure matrices, the complex stability radius can precisely be computed via the associated transfer functions. Then, the class of positive linear Volterra-Stieltjes equations is studied in detail. It is shown that for this class, complex, real and positive stability radius under multi-perturbations or multi-affine perturbations coincide and can be computed by simple formulae expressed in terms of the system matrices. As direct consequences of the obtained results, we get some results on robust stability of positive linear integro-differential equations and of positive linear functional differential equations. To the best of our knowledge, most of the results of this paper are new. 相似文献