全文获取类型
收费全文 | 51683篇 |
免费 | 6025篇 |
国内免费 | 4646篇 |
专业分类
化学 | 14592篇 |
晶体学 | 1005篇 |
力学 | 10440篇 |
综合类 | 657篇 |
数学 | 19713篇 |
物理学 | 15947篇 |
出版年
2024年 | 124篇 |
2023年 | 642篇 |
2022年 | 1138篇 |
2021年 | 1286篇 |
2020年 | 1608篇 |
2019年 | 1402篇 |
2018年 | 1434篇 |
2017年 | 1880篇 |
2016年 | 2017篇 |
2015年 | 1637篇 |
2014年 | 2730篇 |
2013年 | 4186篇 |
2012年 | 3108篇 |
2011年 | 3460篇 |
2010年 | 2878篇 |
2009年 | 3382篇 |
2008年 | 3308篇 |
2007年 | 3148篇 |
2006年 | 2836篇 |
2005年 | 2672篇 |
2004年 | 2256篇 |
2003年 | 1962篇 |
2002年 | 1741篇 |
2001年 | 1426篇 |
2000年 | 1361篇 |
1999年 | 1258篇 |
1998年 | 1144篇 |
1997年 | 981篇 |
1996年 | 832篇 |
1995年 | 669篇 |
1994年 | 617篇 |
1993年 | 504篇 |
1992年 | 507篇 |
1991年 | 380篇 |
1990年 | 301篇 |
1989年 | 241篇 |
1988年 | 199篇 |
1987年 | 148篇 |
1986年 | 105篇 |
1985年 | 159篇 |
1984年 | 150篇 |
1983年 | 72篇 |
1982年 | 96篇 |
1981年 | 77篇 |
1980年 | 46篇 |
1979年 | 64篇 |
1978年 | 46篇 |
1977年 | 49篇 |
1976年 | 22篇 |
1974年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
The Monte Carlo ray-tracing method (MCRT) based on the concept of radiation distribution factor is extended to solve radiative heat transfer problem in turbulent fluctuating media under the optically thin fluctuation approximation. A one-dimensional non-scattering turbulent fluctuating media is considered, in which the mean temperature and absorption coefficient distribution are assumed and the shape of probability density function is given. The distribution of the time-averaged volume radiation heat source is solved by MCRT and direct integration method. It is shown that the results of MCRT based on the concept of radiation distribution factor agree with these of integration solution very well, but results of MCRT based on the concept of radiative transfer coefficient do not agree with these of integration solution. The solution of time-averaged radiative transfer equation by the concept of radiative transfer coefficient should be treated with caution. 相似文献
113.
Huimin Xie Biao Li Robert Geer Bai Xu James Castracane 《Optics and Lasers in Engineering》2003,40(3):163-177
A focused ion beam (FIB) Moiré method is proposed to measure the in-plane deformation of object in a micrometer scale. The FIB Moiré is generated by the interference between a prepared specimen grating and FIB raster scan lines. The principle of the FIB Moiré is described. The sensitivity and accuracy of deformation measurement are discussed in detail. Several specimen gratings with 0.14 and 0.20 μm spacing are used to generate FIB Moiré patterns. The FIB Moiré method is successfully used to measure the residual deformation in a micro-electro-mechanical system structure after removing the SiO2 sacrificial layer with a 5000 lines/mm grating. The results demonstrate the feasibility of this method. 相似文献
114.
本文使用变分方法证明了三维标准切触球的标准勒让德扭结,至少存在一个弦连结适应于标准切触结构的任何选定切触形式,这部分证明了著名的阿诺德弦猜想。 相似文献
115.
类比方法与光的本性的探索 总被引:2,自引:0,他引:2
简要回顾了人类对光的本性的探索历程,介绍了物理学家在研究过程中对类比方法的运用。 相似文献
116.
溃坝问题的间断有限元方法 总被引:2,自引:0,他引:2
本文研究90年代初提出的Runge-Kutta间断Galerkin有限元方法,给出该方法的精度分析,通过经典算例验证该方法处理间断问题、捕捉锐利波形的能力,并将其推广到求解浅水问题.针对坝底无摩擦,无坡度的理想情形进行讨论,给出方溃坝和圆溃坝问题的数值模拟结果. 相似文献
117.
118.
New Exact Solutions to the Combined KdV and mKdV Equation 总被引:2,自引:0,他引:2
Yan-ze Peng 《International Journal of Theoretical Physics》2003,42(4):863-868
The modified mapping method is developed to obtain new exact solutions to the combined KdV and mKdV equation. The method is applicable to a large variety of nonlinear evolution equations, as long as odd- and even-order derivative terms do not coexist in the equation under consideration. 相似文献
119.
Piaoping Yang Jianfeng Yu Zhenlü Wang Qingsheng Liu Tonghao Wu 《Reaction Kinetics and Catalysis Letters》2004,83(2):275-282
Mg-Al, Zn-Al and Ni-Al hydrotalcite-like compounds with high crystallinity were synthesized by using the decomposing property
of urea at high temperature. The crystallinity and the regularly of the samples were much preferable to those synthesized
by other methods.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
120.
The system design must be started from the concept with low cost and high performance. In this point, the topological shape of the structure is very important in the view of the structural rigidities and light-weight design.In this paper, the optimization methodology is presented in the design stage of the large optical mirror. We obtain the optimal layout through the topology optimization and then design the details through the size or shape optimization for structural rigidity. 相似文献