全文获取类型
收费全文 | 148069篇 |
免费 | 12670篇 |
国内免费 | 7627篇 |
专业分类
化学 | 73182篇 |
晶体学 | 1385篇 |
力学 | 11032篇 |
综合类 | 319篇 |
数学 | 39418篇 |
物理学 | 43030篇 |
出版年
2024年 | 279篇 |
2023年 | 1603篇 |
2022年 | 2716篇 |
2021年 | 2919篇 |
2020年 | 3107篇 |
2019年 | 2913篇 |
2018年 | 12307篇 |
2017年 | 11953篇 |
2016年 | 9237篇 |
2015年 | 4272篇 |
2014年 | 4409篇 |
2013年 | 5592篇 |
2012年 | 10302篇 |
2011年 | 16742篇 |
2010年 | 9861篇 |
2009年 | 9981篇 |
2008年 | 10888篇 |
2007年 | 12547篇 |
2006年 | 3950篇 |
2005年 | 4384篇 |
2004年 | 3886篇 |
2003年 | 3818篇 |
2002年 | 2722篇 |
2001年 | 1704篇 |
2000年 | 1640篇 |
1999年 | 1682篇 |
1998年 | 1490篇 |
1997年 | 1433篇 |
1996年 | 1484篇 |
1995年 | 1164篇 |
1994年 | 995篇 |
1993年 | 856篇 |
1992年 | 728篇 |
1991年 | 644篇 |
1990年 | 550篇 |
1989年 | 443篇 |
1988年 | 393篇 |
1987年 | 331篇 |
1986年 | 306篇 |
1985年 | 250篇 |
1984年 | 185篇 |
1983年 | 138篇 |
1982年 | 121篇 |
1981年 | 105篇 |
1980年 | 111篇 |
1979年 | 77篇 |
1978年 | 64篇 |
1977年 | 58篇 |
1976年 | 46篇 |
1973年 | 53篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
In this article, we construct and analyze a residual-based a posteriori error estimator for a quadratic finite volume method (FVM) for solving nonlinear elliptic partial differential equations with homogeneous Dirichlet boundary conditions. We shall prove that the a posteriori error estimator yields the global upper and local lower bounds for the norm error of the FVM. So that the a posteriori error estimator is equivalent to the true error in a certain sense. Numerical experiments are performed to illustrate the theoretical results. 相似文献
2.
The structure, chemical composition, and magnetic properties of electrochemically deposited nanocrystalline Co-Ni-Fe films
were investigated using a number of techniques. A high saturation magnetic induction up to B
s
= 21 kG was attained. An enhancement of the saturation magnetization compared to the ideal anticipated one was revealed,
which correlated with the nonlinear behavior of the structural phase composition and lattice parameters with the change of
the composition.
The text was submitted by the authors in English. 相似文献
3.
玻璃陶瓷材料中Tm3+离子红外到蓝色上转换发光 总被引:4,自引:0,他引:4
系统研究了PbF2+GeO2+WO3ⅩⅣTmF3玻璃陶瓷材料中,在近红外光(1.06μm)激发下,Tm3+离子的发光特性.实验中观测到Tm3+离子的两组峰值位置分别在20920cm-1和22173cm-1的蓝色上转换发光,并证实这两组上转换发光分别与吸收三个和四个光子有关,同时建立了上转换发光的模型.为了选择最佳掺杂浓度,详细地测量了Tm3+离子峰值为20920cm-1的蓝色上转换发光强度与TmF3浓度的关系. 相似文献
4.
5.
本文用B-网方法确定了△_(nm)~((2))剖分上二次双周期样条函数空间的维数,给出了插值条件的几种提法,证明了解的存在唯一性. 相似文献
6.
Liu Heping 《分析论及其应用》1991,7(2):106-117
We give the estimate for the growth of the group Fourier transforms of the Hardy spaces and establish and Hp-multipleir theorem satisfying Michlin condition on the Heisenberg group. 相似文献
7.
Claudia-Elisabeth Wulz 《Czechoslovak Journal of Physics》2002,52(3):C155-C170
The principal physics goals of the Compact Muon Solenoid experiment under construction at the Large Hadron Collider at CERN in Geneva are reviewed. Procedures to search for the Standard Model Higgs boson, supersymmetric Higgses and other supersymmetric particles are described. 相似文献
8.
Guofen Yu Yuanci Gao Shenggang Liu Wenxiang Wang Jin Wu 《International Journal of Infrared and Millimeter Waves》2002,23(8):1261-1269
Analysis of the field distributions in a single biological cell under electromagnetic wave is given. With Debye approximation, the dielectric relaxation of each part of the cell, including the extracellular and cellular media, the cell membrane and the nuclear membrane, was taken into account. Making use of some typical parameters for a cell, the voltage across nuclear and cytoplasma membranes under electromagnetic waves are calculated up to millimeter wave frequency range. The calculated result indicates that it is unlikely to generate electroporation by present available millimeter wave sources. 相似文献
9.
In this paper, we consider a class of functional equations and prove three theorems which give the approximation properties
and error estimates of the optimal polynomial approximation of slution of those functional equations. 相似文献
10.
The drawbacks of our earlier report of preparing fuel cell catalyst arrays by borohydride reduction of inkjet prepared arrays of metal salts are discussed along with the need for inclusion of state-of-the-art metrics in all array screening. An alternative method for screening of hydrogen/air cathode catalysts, direct methanol fuel cell (DMFC) anode catalysts, and catalyst loading studies is provided. State-of-the-art Johnson Matthey catalysts were used in control experiments to demonstrate the utility of the array fuel cell for high throughput screening of fuel cell catalysts in the 3-4 mg/cm2 range. This report lays out hard learned rules for high throughput screening and demonstrates that the array fuel cell can be used for very precise screening of libraries of membrane electrode assembly (MEA) components without the pitfalls discussed in the introduction. 相似文献