全文获取类型
收费全文 | 16491篇 |
免费 | 1266篇 |
国内免费 | 1322篇 |
专业分类
化学 | 3999篇 |
晶体学 | 322篇 |
力学 | 1522篇 |
综合类 | 401篇 |
数学 | 8196篇 |
物理学 | 4639篇 |
出版年
2023年 | 196篇 |
2022年 | 263篇 |
2021年 | 291篇 |
2020年 | 291篇 |
2019年 | 296篇 |
2018年 | 302篇 |
2017年 | 368篇 |
2016年 | 400篇 |
2015年 | 342篇 |
2014年 | 647篇 |
2013年 | 1044篇 |
2012年 | 801篇 |
2011年 | 1012篇 |
2010年 | 1028篇 |
2009年 | 1266篇 |
2008年 | 1179篇 |
2007年 | 1233篇 |
2006年 | 1058篇 |
2005年 | 794篇 |
2004年 | 702篇 |
2003年 | 675篇 |
2002年 | 592篇 |
2001年 | 548篇 |
2000年 | 421篇 |
1999年 | 426篇 |
1998年 | 382篇 |
1997年 | 316篇 |
1996年 | 278篇 |
1995年 | 234篇 |
1994年 | 204篇 |
1993年 | 167篇 |
1992年 | 187篇 |
1991年 | 127篇 |
1990年 | 104篇 |
1989年 | 102篇 |
1988年 | 78篇 |
1987年 | 73篇 |
1986年 | 50篇 |
1985年 | 78篇 |
1984年 | 75篇 |
1983年 | 40篇 |
1982年 | 79篇 |
1981年 | 56篇 |
1980年 | 46篇 |
1979年 | 66篇 |
1978年 | 37篇 |
1977年 | 31篇 |
1976年 | 21篇 |
1974年 | 18篇 |
1973年 | 20篇 |
排序方式: 共有10000条查询结果,搜索用时 281 毫秒
71.
基础房价的相关指标及其走势一直是大众关心的热门话题.本文通过对上海基础房价相关指标的分析,建立了市场房价走势的两个数学模型.模型一:在相关性分析的基础上利用主成分分析消除指标间的共线性,再用回归拟合房价模型并进行预测;模型二:在相关性分析的基础上利用核估计方法预测出房价.继呵对2005年下半年的房价走势进行了预测,得出的结果与实际情况相吻合. 相似文献
72.
Chen Hao 《中国科学A辑(英文版)》2006,49(5):715-720
In this paper, for the the primes p such that 3 is a divisor of p − 1, we prove a result which reduces the computation of the linear complexity of a sequence over GF(p
m) (any positive integer m) with the period 3n (n and p
m − 1 are coprime) to the computation of the linear complexities of three sequences with the period n. Combined with some known algorithms such as generalized Games-Chan algorithm, Berlekamp-Massey algorithm and Xiao-Wei-Lam-Imamura
algorithm, we can determine the linear complexity of any sequence over GF(p
m) with the period 3n (n and p
m
− 1 are coprime) more efficiently. 相似文献
73.
S. Neukirch G.H.M. van der HeijdenJ.M.T. Thompson 《Journal of the mechanics and physics of solids》2002,50(6):1175-1191
We use three different approaches to describe the static spatial configurations of a twisted rod as well as its stability during rigid loading experiments. The first approach considers the rod as infinite in length and predicts an instability causing a jump to self-contact at a certain point of the experiment. Semi-finite corrections, taken into account as a second approach, reveal some possible experiments in which the configuration of a very long rod will be stable through out. Finally, in a third approach, we consider a rod of real finite length and we show that another type of instability may occur, leading to possible hysteresis behavior. As we go from infinite to finite length, we compare the different information given by the three approaches on the possible equilibrium configurations of the rod and their stability. These finite size effects studied here in a 1D elasticity problem could help us guess what are the stability features of other more complicated (2D elastic shells for example) problems for which only the infinite length approach is understood. 相似文献
74.
In this paper, nonconvex multiobjective optimization problems are studied. New characterizations of a properly efficient solution in the sense of Geoffrion's are established in terms of the stability of one scalar optimization problem and the existence of an exact penalty function of a scalar constrained program, respectively. One of the characterizations is applied to derive necessary conditions for a properly efficient control-parameter pair of a nonconvex multiobjective discrete optimal control problem with linear constraints. 相似文献
75.
M. A. Posypkin I. Kh. Sigal 《Computational Mathematics and Mathematical Physics》2006,46(12):2187-2202
The efficiency of parallel implementations of the branch-and-bound method in discrete optimization problems is considered. A theoretical analysis and comparison of two parallel implementations of this method is performed. A mathematical model of the computation process is constructed and used to obtain estimates of the maximum possible speedup. Examples of problems in which none of these two parallel implementations can speed up the computations are considered. 相似文献
76.
Youssef Randjiou 《Journal of Theoretical Probability》2006,19(3):701-720
Let μ+(t) and μ−(t) be the locations of the maximum and minimum, respectively, of a standard Brownian motion in the interval [0,t]. We establish a joint integral test for the lower functions of μ+(t) and μ−(t), in the sense of Paul Lévy. In particular, it yields the law of the iterated logarithm for max(μ+(t),μ−(t)) as a straightforward consequence. Our result is in agreement with well-known theorems of Chung and Erdős [(1952) Trans. Amer. Math. Soc. 72, 179–186.], and Csáki, F?ldes and Révész [(1987) Prob. Theory Relat. Fields
76, 477–497].
相似文献
77.
A. Shaporenko A. Terfort M. Grunze M. Zharnikov 《Journal of Electron Spectroscopy and Related Phenomena》2006
Analysis of photoemission spectra of complex thioaromatic self-assembled monolayers (SAMs) requires the knowledge and understanding of such spectra for the basic systems. Keeping this goal in mind, synchrotron-based high-resolution X-ray photoelectron spectroscopy was used to characterize SAMs formed from the simplest thioaromatic compounds, namely thiophenol, 1,1′-biphenyl-4-thiol and 1,1′;4′,1″-terphenyl-4-thiol on evaporated Au(1 1 1) and Ag(1 1 1) substrates. The acquired S 2p and C 1s spectra were analyzed in terms of fine structure and initial and final state effects in the photoemission process. The assignment of the individual spectral features was considered in detail. Conclusions on quality and chemical and structural homogeneity of the investigated SAMs were derived. 相似文献
78.
条件愈苦,意志愈坚 --记王淦昌早年的科研活动 总被引:1,自引:0,他引:1
文章介绍了中国物理学家王淦昌早期的科研工作,特别是在抗日战争时期的科研成绩.王淦昌早期的科研贡献并不是在先进的实验仪器上,在条件优裕的实验室内完成的,而是在实验设备缺乏,科学文献不足等极端困难的环境中完成的.从王淦昌身上,可以看到那个时代中国优秀科学家脚踏实地、执志若金的奋斗精神. 相似文献
79.
Silvia Vogel 《Annals of Operations Research》2006,142(1):269-282
The paper considers upper semicontinuous behavior in distribution of sequences of random closed sets. Semiconvergence in distribution
will be described via convergence in distribution of random variables with values in a suitable topological space. Convergence
statements for suitable functions of random sets are proved and the results are employed to derive stability statements for
random optimization problems where the objective function and the constraint set are approximated simultaneously.
The author is grateful to two anonymous referees for helpful suggestions. 相似文献
80.
对Hajek-Renyi不等式进行了推广,利用推广的不等式给出了随机变量序列绝对平均意义下的强大数定律的一个条件. 相似文献