全文获取类型
收费全文 | 23010篇 |
免费 | 2560篇 |
国内免费 | 2209篇 |
专业分类
化学 | 2389篇 |
晶体学 | 37篇 |
力学 | 1965篇 |
综合类 | 549篇 |
数学 | 15693篇 |
物理学 | 7146篇 |
出版年
2024年 | 29篇 |
2023年 | 190篇 |
2022年 | 388篇 |
2021年 | 406篇 |
2020年 | 466篇 |
2019年 | 475篇 |
2018年 | 503篇 |
2017年 | 670篇 |
2016年 | 752篇 |
2015年 | 563篇 |
2014年 | 1165篇 |
2013年 | 1493篇 |
2012年 | 1158篇 |
2011年 | 1452篇 |
2010年 | 1305篇 |
2009年 | 1547篇 |
2008年 | 1544篇 |
2007年 | 1666篇 |
2006年 | 1481篇 |
2005年 | 1367篇 |
2004年 | 1169篇 |
2003年 | 1073篇 |
2002年 | 878篇 |
2001年 | 795篇 |
2000年 | 739篇 |
1999年 | 650篇 |
1998年 | 573篇 |
1997年 | 546篇 |
1996年 | 389篇 |
1995年 | 337篇 |
1994年 | 272篇 |
1993年 | 207篇 |
1992年 | 180篇 |
1991年 | 156篇 |
1990年 | 153篇 |
1989年 | 110篇 |
1988年 | 107篇 |
1987年 | 93篇 |
1986年 | 76篇 |
1985年 | 100篇 |
1984年 | 78篇 |
1983年 | 54篇 |
1982年 | 70篇 |
1981年 | 69篇 |
1980年 | 44篇 |
1979年 | 42篇 |
1978年 | 36篇 |
1977年 | 32篇 |
1976年 | 35篇 |
1973年 | 26篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
91.
92.
n进制中非零数字之积函数的均值公式 总被引:8,自引:0,他引:8
设 N =a1nk1+ a2 nk2 +… + asnks( 1 aik2 >… >ks 0 ) ,a( N,n) =a1a2 … as,本文给出了均值 Ar( N ,n) =∑m相似文献
93.
94.
Hidetoshi Shimodaira 《Annals of the Institute of Statistical Mathematics》1997,49(3):395-410
The asymptotic error probability of Linhart's model selection test isevaluated, and compared with the nominal significance level. We examine thecase where the expected discrepancies of the candidate models from the truemodel are asymptotically equal. The local alternatives method is employed inthe limiting operation of the asymptotic evaluation. Although the errorprobability under the null hypothesis is actually shown to be equal to orless than the level for most situations, intolerable violations of the errorcontrol are observed for nested models: It is often erroneously concludedthat the smaller model is significantly better than the larger model. Toprevent this violation, a modification of Linhart's test statistic isproposed. The effectiveness of the proposed test is confirmed throughtheoretical analysis and numerical simulations. 相似文献
95.
本文提出了一类特殊的n人合作对策模型─—弱1—凸对策,研究了弱1—凸对策的解的性质,并证明弱1—凸对策的解满足所有常见的公理化特征. 相似文献
96.
Real-time packet traffic is characterized by a strict deadline on the end-to-end time delay and an upper bound on the information loss. Due to the high correlation among consecutive packets, the individual packet loss does not well characterize the performance of real-time packet sessions. An additional measure of packet loss is necessary to adequately assess the quality of each real-time connection. The additional measure considered here is the average number of consecutively lost packets, also called the average packet gap. We derive a closed form for the average packet gap for the multiclassG/G/m/B queueing system in equilibrium and show that it only depends on the loss behavior of two consecutive packets. This result considerably simplifies the monitoring process of real-time packet traffic sessions. If the packet loss process is markovian, the consecutive packet loss has a geometric distribution. 相似文献
97.
H. R. Ebrahimi-Vishki M. A. Pourabdollah 《Proceedings of the American Mathematical Society》1997,125(7):2171-2174
The purpose of this paper is to introduce an algebra of functions on a semitopological semigroup and to study these functions from the point of view of universal semigroup compactification. We show that the corresponding semigroup compactification of this algebra is universal with respect to the property of being a nilpotent group.
98.
谐振子薛定谔方程的简单解法 总被引:2,自引:0,他引:2
物质的许多物理与化学性质都可以用线性谐振子模型解释,本文用简单的数学运算求解线性谐振子的薛定谔方程,避免了特殊函数等复杂的数学运算,得出了量子力学教材完全相同的结果。 相似文献
99.
The aim of this paper is to present construction of finite element multiscaling function with three coefficients. In order to illuminate the result, two examples are given finally. 相似文献
100.
We prove that RANDOM EDGE, the simplex algorithm that always chooses a random improving edge to proceed on, can take a mildly exponential number of steps in the model of abstract objective functions (introduced by Williamson Hoke [Completely unimodal numberings of a simple polytope, Discrete Appl. Math. 20 (1988) 69-81.] and by Kalai [A simple way to tell a simple polytope from its graph, J. Combin. Theory Ser. A 49(2) (1988) 381-383.] under different names). We define an abstract objective function on the n-dimensional cube for which the algorithm, started at a random vertex, needs at least exp(const·n1/3) steps with high probability. The best previous lower bound was quadratic. So in order for RANDOM EDGE to succeed in polynomial time, geometry must help. 相似文献