全文获取类型
收费全文 | 112178篇 |
免费 | 13608篇 |
国内免费 | 11731篇 |
专业分类
化学 | 50006篇 |
晶体学 | 2033篇 |
力学 | 14356篇 |
综合类 | 1828篇 |
数学 | 25471篇 |
物理学 | 43823篇 |
出版年
2024年 | 175篇 |
2023年 | 883篇 |
2022年 | 1637篇 |
2021年 | 3206篇 |
2020年 | 2882篇 |
2019年 | 2724篇 |
2018年 | 2526篇 |
2017年 | 3524篇 |
2016年 | 4277篇 |
2015年 | 3637篇 |
2014年 | 5346篇 |
2013年 | 8464篇 |
2012年 | 6333篇 |
2011年 | 7075篇 |
2010年 | 6108篇 |
2009年 | 7039篇 |
2008年 | 6993篇 |
2007年 | 7286篇 |
2006年 | 6329篇 |
2005年 | 5198篇 |
2004年 | 4729篇 |
2003年 | 4414篇 |
2002年 | 6525篇 |
2001年 | 3681篇 |
2000年 | 3087篇 |
1999年 | 2751篇 |
1998年 | 2525篇 |
1997年 | 2108篇 |
1996年 | 1849篇 |
1995年 | 1633篇 |
1994年 | 1524篇 |
1993年 | 1340篇 |
1992年 | 1257篇 |
1991年 | 913篇 |
1990年 | 733篇 |
1989年 | 595篇 |
1988年 | 613篇 |
1987年 | 466篇 |
1986年 | 382篇 |
1985年 | 525篇 |
1984年 | 411篇 |
1983年 | 242篇 |
1982年 | 429篇 |
1981年 | 581篇 |
1980年 | 484篇 |
1979年 | 538篇 |
1978年 | 426篇 |
1977年 | 337篇 |
1976年 | 277篇 |
1973年 | 171篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
171.
The angular variations of the five-fold differential cross section obtained by using different wave functions of helium are
compared with experimental data. It is found that in the coplanar geometry two kinematical arrangements, (i) equal energy
sharing between the two ejected electrons with one of them ejected along the momentum transfer direction and the other along
varying direction and (ii) the Bethe ridge condition with fixed sum of ejected electron energies and varying angle between
them, are very sensitive to e-e correlations contained in the target wave function. This comparison has been used to show
that open-shell class of wave functions better incorporate e-e correlations than the closed-shell class. 相似文献
172.
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
173.
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
174.
根据栅控恒压电晕充电组合反极性电晕补偿充电法的实验结果计算出铁电驻极体的极化强度.结果说明,伴随着薄膜内孔洞气体的Paschen击穿,该铁电体的极化强度随栅压增加而显著上升.利用上述充电方法和热刺激放电(TSD)谱的分析讨论了这类空间电荷型宏观电偶极子,及与其补偿的空间电荷热退极化的电荷动态特性;阐明了这两类俘获电荷的能阱分布,即构成宏观电偶极子的位于孔洞上下介质层内的等值异号空间电荷分别被俘获在深、浅两种能值陷阱内,而位于薄膜表面层的注入空间电荷则被俘获在中等能值陷阱中.
关键词:
反极性电晕补偿充电法
铁电驻极体
充电电流
热刺激放电 相似文献
175.
176.
基于FPGA并行处理的实时图像相关速度计 总被引:3,自引:1,他引:2
研究制作了一种采用高速线阵CCD的实时相关速度计,其测量数据的输出速率可达每秒一万次。针对以往光学相关测速方法的问题进行了讨论,探讨了适合FPGA并行处理的算法,制作了高速线阵CCD摄像机及其处理装置。通过实验验证了系统的可行性和可实现性。 相似文献
177.
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
178.
179.
It is proved that the variety of relevant disjunction lattices has the finite embeddability property. It follows that Avron's relevance logic RMI min has a strong form of the finite model property, so it has a solvable deducibility problem. This strengthens Avron's result that RMI min is decidable. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
180.
S. K. Godunov V. T. Zhukov O. B. Feodoritova 《Computational Mathematics and Mathematical Physics》2006,46(6):971-982
An algorithm is constructed for calculating invariant subspaces of symmetric hyperbolic systems arising in electromagnetic, acoustic, and elasticity problems. Discrete approximations are calculated for subspaces that correspond to minimal eigenvalues and smooth eigenfunctions. Difficulties related to the presence of an infinite-dimensional kernel in the differential operator are successfully handled. The efficiency of the algorithm is demonstrated using acoustics equations. 相似文献