全文获取类型
收费全文 | 74640篇 |
免费 | 8818篇 |
国内免费 | 7078篇 |
专业分类
化学 | 39749篇 |
晶体学 | 642篇 |
力学 | 6963篇 |
综合类 | 1025篇 |
数学 | 11809篇 |
物理学 | 30348篇 |
出版年
2024年 | 104篇 |
2023年 | 867篇 |
2022年 | 1291篇 |
2021年 | 2564篇 |
2020年 | 2024篇 |
2019年 | 1982篇 |
2018年 | 1602篇 |
2017年 | 1864篇 |
2016年 | 2366篇 |
2015年 | 2343篇 |
2014年 | 3080篇 |
2013年 | 5405篇 |
2012年 | 3691篇 |
2011年 | 4171篇 |
2010年 | 3724篇 |
2009年 | 4499篇 |
2008年 | 4805篇 |
2007年 | 5003篇 |
2006年 | 4197篇 |
2005年 | 3255篇 |
2004年 | 2805篇 |
2003年 | 2756篇 |
2002年 | 5044篇 |
2001年 | 2450篇 |
2000年 | 2034篇 |
1999年 | 1783篇 |
1998年 | 1708篇 |
1997年 | 1244篇 |
1996年 | 1193篇 |
1995年 | 974篇 |
1994年 | 991篇 |
1993年 | 921篇 |
1992年 | 872篇 |
1991年 | 631篇 |
1990年 | 487篇 |
1989年 | 412篇 |
1988年 | 411篇 |
1987年 | 358篇 |
1986年 | 310篇 |
1985年 | 467篇 |
1984年 | 318篇 |
1983年 | 189篇 |
1982年 | 392篇 |
1981年 | 526篇 |
1980年 | 467篇 |
1979年 | 509篇 |
1978年 | 401篇 |
1977年 | 299篇 |
1976年 | 269篇 |
1973年 | 169篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
101.
P. E. Cladis 《Journal of statistical physics》1991,62(5-6):899-925
We first discuss nonlinear aspects of phase transition theory applied to a particular liquid crystal phase transition. A simple derivation is given to show how two coupled Goldstone modes (one appearing as gauge fluctuations of the ordered phase) can force a phase transition, against all expectations, to take place discontinuously (theory of Halperin, Lubensky, and Ma)-but the discontinuity may be immeasurably small. Then, we describe a new dynamical test of phase transition order, developed by Cladiset al., that turns out to be more sensitive than x-ray diffraction and adiabatic calorimetry. Quantitative data found by this new method are in excellent agreement with the measurements of adiabatic calorimetry and x-ray diffraction as well as expectations implicit in the predictions of HLM.This is the text of an after-banquet talk given at the CNLS Workshop on the Dynamics of Concentrated Systems. 相似文献
102.
Summary In this paper a Gauss-Jordan algorithm with column interchanges is presented and analysed. We show that, in contrast with Gaussian elimination, the Gauss-Jordan algorithm has essentially differing properties when using column interchanges instead of row interchanges for improving the numerical stability. For solutions obtained by Gauss-Jordan with column interchanges, a more satisfactory bound for the residual norm can be given. The analysis gives theoretical evidence that the algorithm yields numerical solutions as good as those obtained by Gaussian elimination and that, in most practical situations, the residuals are equally small. This is confirmed by numerical experiments. Moreover, timing experiments on a Cyber 205 vector computer show that the algorithm presented has good vectorisation properties. 相似文献
103.
用分子动力学方法对5%负失配条件下面心立方晶体铝薄膜的原子沉积外延生长进行了三维模拟.铝原子间的相互作用采用嵌入原子法(EAM)多体势计算.模拟结果再现了失配位错的形成现象.分析表明,失配位错在形成之初即呈现为Shockley扩展位错,即由两个伯格斯矢量为〈211〉/6的部分位错和其间的堆垛层错组成,两个部分位错的间距、即层错宽度为1.8 nm,与理论计算结果一致;外延晶体薄膜沉积生长中,位错对会发生滑移,但其间距保持稳定.进一步观察发现,该扩展位错产生于一种类似于“局部熔融-重结晶”的表层局部无序紊乱-
关键词:
失配位错
外延生长
薄膜
分子动力学
铝 相似文献
104.
105.
106.
This paper reports that the m-plane GaN layer is grown on (200)-plane LiAlO2 substrate by metal-organic chemical wpour deposition (MOCVD) method. Tetragonal-shaped crystallites appear at the smooth surface. Raman measurement illuminates the compressive stress in the layer which is released with increasing the layer's thickness. The high transmittance (80%), sharp band edge and excitonic absorption peak show that the GaN layer has good optical quality. The donor acceptor pair emission peak located at -3.41 eV with full-width at half maximum of 120 meV and no yellow peaks in the photoluminescence spectra partially show that no Li incorporated into GaN layer from the LiAlO2 substrate. 相似文献
107.
Piotr Garbaczewski 《Journal of statistical physics》2006,123(2):315-355
We analyze the functioning of Gibbs-type entropy functionals in the time domain, with emphasis on Shannon and Kullback-Leibler entropies of time-dependent continuous probability distributions. The Shannon entropy validity is extended to probability distributions inferred from L
2(R
n
) quantum wave packets. In contrast to the von Neumann entropy which simply vanishes on pure states, the differential entropy quantifies the degree of probability (de)localization and its time development. The associated dynamics of the Fisher information functional quantifies nontrivial power transfer processes in the mean, both in dissipative and quantum mechanical cases.
PACS NUMBERS: 05.45.+b, 02.50.-r, 03.65.Ta, 03.67.-a 相似文献
108.
Toward Fuzzy Optimization without Mathematical Ambiguity 总被引:15,自引:0,他引:15
Baoding Liu 《Fuzzy Optimization and Decision Making》2002,1(1):43-63
Fuzzy programming has been discussed widely in literature and applied in such various disciplines as operations research, economic management, business administration, and engineering. The main purpose of this paper is to present a brief review on fuzzy programming models, and classify them into three broad classes: expected value model, chance-constrained programming and dependent-chance programming. In order to solve general fuzzy programming models, a hybrid intelligent algorithm is also documented. Finally, some related topics are discussed. 相似文献
109.
110.