全文获取类型
收费全文 | 84325篇 |
免费 | 6688篇 |
国内免费 | 7441篇 |
专业分类
化学 | 35997篇 |
晶体学 | 477篇 |
力学 | 8715篇 |
综合类 | 1313篇 |
数学 | 26122篇 |
物理学 | 25830篇 |
出版年
2023年 | 611篇 |
2022年 | 1194篇 |
2021年 | 1469篇 |
2020年 | 1629篇 |
2019年 | 1900篇 |
2018年 | 1574篇 |
2017年 | 1938篇 |
2016年 | 2218篇 |
2015年 | 2022篇 |
2014年 | 2829篇 |
2013年 | 6120篇 |
2012年 | 3476篇 |
2011年 | 3791篇 |
2010年 | 3186篇 |
2009年 | 4443篇 |
2008年 | 4954篇 |
2007年 | 5195篇 |
2006年 | 4812篇 |
2005年 | 4199篇 |
2004年 | 3891篇 |
2003年 | 3848篇 |
2002年 | 4989篇 |
2001年 | 3001篇 |
2000年 | 2839篇 |
1999年 | 2553篇 |
1998年 | 2379篇 |
1997年 | 1998篇 |
1996年 | 1795篇 |
1995年 | 1667篇 |
1994年 | 1500篇 |
1993年 | 1281篇 |
1992年 | 1256篇 |
1991年 | 971篇 |
1990年 | 774篇 |
1989年 | 680篇 |
1988年 | 654篇 |
1987年 | 505篇 |
1986年 | 440篇 |
1985年 | 486篇 |
1984年 | 478篇 |
1983年 | 222篇 |
1982年 | 386篇 |
1981年 | 435篇 |
1980年 | 329篇 |
1979年 | 326篇 |
1978年 | 235篇 |
1977年 | 222篇 |
1976年 | 164篇 |
1974年 | 114篇 |
1973年 | 116篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
131.
A. D. Matveev 《Journal of Applied Mechanics and Technical Physics》2003,44(5):721-726
Modified three-dimensional formulations of bending problems of homogeneous elastic plates and beams are considered. Modification of the known three-dimensional formulations reduces to using additional constraints imposed on displacement functions. An advantage of the formulations proposed is that complex fixing conditions of plates and beams can be taken into account. 相似文献
132.
Fillmore在[1]中得到一个定理:设A,T是Banach空间X上的线性变换,A有界,若Lat(A) Lat(T)且AT=TA,则T是A的多项式.在本文里,以此作为引理,讨论了Banach空间上可逆线性变换A在什么情况下,A-1可表示为A的多项式.本文最主要的结论是定理3.4:设X是Banach空间,A是X上的有界线性变换,且可逆,则A-1是A的多项式当且仅当A-1是A的局部多项式. 相似文献
133.
A. Khrennikov 《Annalen der Physik》2003,12(10):575-585
We study the probabilistic consequences of the choice of the basic number field in the quantum formalism. We demonstrate that by choosing a number field for a linear space representation of quantum model it is possible to describe various interference phenomena. We analyse interference of probabilistic alternatives induced by real, complex, hyperbolic (Clifford) and p‐adic representations. 相似文献
134.
平行机半在线排序问题研究(Ⅰ) 总被引:15,自引:1,他引:14
对半在线平行机排序问题的研究进展作了详细综述和进一步探讨。文章给出半在线排序问题的背景、定义、分类和求解。介绍它们定义和在不同机器环境和目标函数下半在线排序问题分类,以及第一类半在线模型的近似算法的设计及其竞争比分析。 相似文献
135.
136.
A.J.?Lpez-Moreno 《Acta Mathematica Hungarica》2005,106(4):343-354
Summary We obtain preservation inequalities for Lipschitz constants of higher order in simultaneous approximation processes by Bernstein type operators. From such inequalities we derive the preservation of the corresponding Lipschitz spaces. 相似文献
137.
GU Bai-Ping REN Zhong-Zhou 《理论物理通讯》2005,44(2):337-342
The Dirac optical potential for p-^14 Be elastic scattering is evaluated by the relativistic impulse approximation. Each of the real part and the imaginary part of the potential shows a pronounced “long tail” for the proton elastic scattering from halo nucleus ^14Be compared with the potentials for proton scattering from its adjacent nuclei ^12C and ^16O, which do not have halo structures.This kind of “long tail” phenomenon suggests another signature for halo nuclei. 相似文献
138.
《Magnetic resonance in chemistry : MRC》2003,41(6):417-430
A systematic study of the one‐bond and long‐range J(C,C), J(C,H) and J(H,H) in the series of nine bicycloalkanes was performed at the SOPPA level with special emphasis on the coupling transmission mechanisms at bridgeheads. Many unknown couplings were predicted with high reliability. Further refinement of SOPPA computational scheme adjusted for better performance was carried out using bicyclo[1.1.1]pentane as a benchmark to investigate the influence of geometry, basis set and electronic correlation. The calculations performed demonstrated that classical ab initio SOPPA applied with the locally dense Dunning's sets augmented with inner core s‐functions used for coupled carbons and Sauer's sets augmented with tight s‐functions used for coupled hydrogens performs perfectly well in reproducing experimental values of different types of coupling constants (the estimated reliability is ca 1–2 Hz) in relatively large organic molecules of up to 11 carbon atoms. Additive coupling increments were derived for J(C,C), J(C,H) and J(H,H) based on the calculated values of coupling constants within SOPPA in the model bicycloalkanes, in reasonably good agreement with the known values obtained earlier on pure empirical grounds. Most of the bridgehead couplings in all but one bicycloalkane appeared to be essentially additive within ca 2–3 Hz while bicyclo[1.1.1]pentane demonstrated dramatic non‐additivity of ?14.5 Hz for J(C,C), +16.6 Hz for J(H,H) and ?5.5 Hz for J(C,H), in line with previous findings. Non‐additivity effects in the latter compound established at the SOPPA level should be attributed to the through‐space non‐bonded interactions at bridgeheads due to the essential overlapping of the bridgehead rear lobes which provides an additional and effective non‐bonding coupling path for the bridgehead carbons and their protons in the bicyclopentane framework. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
139.
姜德元 《浙江大学学报(理学版)》2003,30(5):499-502
研究了NA序列重对数律收敛速度的一般形式,把Davis和Gut的结果推广到了NA的情形,并使梁汉营等人关于对数律一个结果成为特例;作为推论,得到了关于NA序列重对数律收敛速度的充分条件. 相似文献
140.
采用溶解-反应量热法在具有恒温环境的溶解-反应热量计内,测定了[Gd(Gly)4(Im)(H2O)](ClO4)3和[Y(Gly)4(Im)(H2O)](ClO4)3两种稀土甘氨酸咪唑配合物的标准生成焓分别为(-3 461.46 ±0.22) kJ·mol-1 和(-3 926.6±0.90) kJ·mol-1. 相似文献