首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   2120篇
  免费   188篇
  国内免费   135篇
化学   1372篇
晶体学   31篇
力学   83篇
综合类   11篇
数学   518篇
物理学   428篇
  2023年   33篇
  2022年   79篇
  2021年   80篇
  2020年   84篇
  2019年   93篇
  2018年   94篇
  2017年   87篇
  2016年   121篇
  2015年   89篇
  2014年   107篇
  2013年   154篇
  2012年   119篇
  2011年   144篇
  2010年   101篇
  2009年   86篇
  2008年   101篇
  2007年   96篇
  2006年   83篇
  2005年   74篇
  2004年   55篇
  2003年   47篇
  2002年   42篇
  2001年   29篇
  2000年   36篇
  1999年   24篇
  1998年   19篇
  1997年   22篇
  1996年   23篇
  1995年   24篇
  1994年   17篇
  1993年   19篇
  1992年   17篇
  1991年   20篇
  1990年   11篇
  1989年   8篇
  1988年   14篇
  1987年   13篇
  1986年   9篇
  1985年   13篇
  1983年   11篇
  1982年   14篇
  1981年   7篇
  1980年   6篇
  1978年   14篇
  1977年   12篇
  1976年   20篇
  1975年   7篇
  1974年   12篇
  1973年   14篇
  1966年   5篇
排序方式: 共有2443条查询结果,搜索用时 15 毫秒
1.
Zhan  Yang  Dang  Chuangyin 《Mathematical Programming》2021,190(1-2):585-613
Mathematical Programming - In the general equilibrium with incomplete asset markets (GEI) model, the excess demand functions are typically not continuous at the prices for which the assets have...  相似文献   
2.
Journal of Statistical Physics - In this paper, we will study the long time behavior of the simple symmetric exclusion process in the “channel” $$\varLambda _N=[1,N]\cap \mathbb {N}$$...  相似文献   
3.
4.
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   
5.
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.
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   
7.
This paper proposes a floating-point genetic algorithm (FPGA) to solve the unit commitment problem (UCP). Based on the characteristics of typical load demand, a floating-point chromosome representation and an encoding–decoding scheme are designed to reduce the complexities in handling the minimum up/down time limits. Strategic parameters of the FPGA are characterized in detail, i.e., the evaluation function and its constraints, population size, operation styles of selection, crossover operation and probability, mutation operation and probability. A dynamic combination scheme of genetic operators is formulated to explore and exploit the FPGA in the non-convex solution space and multimodal objective function. Experiment results show that the FPGA is a more effective technique among the various styles of genetic algorithms, which can be applied to the practical scheduling tasks in utility power systems.  相似文献   
8.
Using Fourier integral operators with special amplitude functions, we analyze the stabilization of the wave equation in a three-dimensional bounded domain on which exists a trapped ray bouncing up and down infinitely between two parallel parts of the boundary.  相似文献   
9.
Transformations of chemical species formed by the reaction of gaseous BF3 with high pressure and silica preheated at 473 and 1093 K were studied with the use of infrared absorption spectrometry. The species containing -BF2 and the species containing >BF were transformed to each other on the highly-reacted silica depending on the pressure of BF3 in cell, and some of the species containing -BF2 were also desorbed without their transformations to the species containing >BF. H2O played important roles in these transformations.  相似文献   
10.
Alignment carbon nanotubes (ACNTs) were synthesized on silicon substrate coated with Ni catalyst film and Ta buffer layer by plasma-enhanced hot filament chemical vapor deposition using CH4, NH3, and H2 as the reaction gas, and they were investigated by scanning electron microscopy and transmission electron microscopy. It is found that the diameter of the bamboo-structured ACNTs is increased from 62 to 177 nm when the substrate temperature was changed from 626 to 756 °C. Their growth rate is enhanced by the substrate temperature in a range of 626-683 °C and it is reversely reduced with the substrate temperature after the substrate temperature is over 683 °C. Beginning with wetting phenomenon, the effects of the substrate temperature on the structure and growth rate of the ACNTs are analyzed.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号