全文获取类型
收费全文 | 6113篇 |
免费 | 975篇 |
国内免费 | 636篇 |
专业分类
化学 | 1744篇 |
晶体学 | 84篇 |
力学 | 945篇 |
综合类 | 124篇 |
数学 | 1696篇 |
物理学 | 3131篇 |
出版年
2024年 | 10篇 |
2023年 | 47篇 |
2022年 | 117篇 |
2021年 | 111篇 |
2020年 | 166篇 |
2019年 | 139篇 |
2018年 | 124篇 |
2017年 | 219篇 |
2016年 | 244篇 |
2015年 | 188篇 |
2014年 | 306篇 |
2013年 | 539篇 |
2012年 | 370篇 |
2011年 | 443篇 |
2010年 | 332篇 |
2009年 | 407篇 |
2008年 | 400篇 |
2007年 | 384篇 |
2006年 | 365篇 |
2005年 | 297篇 |
2004年 | 280篇 |
2003年 | 269篇 |
2002年 | 245篇 |
2001年 | 211篇 |
2000年 | 193篇 |
1999年 | 184篇 |
1998年 | 165篇 |
1997年 | 115篇 |
1996年 | 140篇 |
1995年 | 95篇 |
1994年 | 90篇 |
1993年 | 79篇 |
1992年 | 72篇 |
1991年 | 55篇 |
1990年 | 47篇 |
1989年 | 43篇 |
1988年 | 39篇 |
1987年 | 33篇 |
1986年 | 19篇 |
1985年 | 28篇 |
1984年 | 24篇 |
1983年 | 10篇 |
1982年 | 18篇 |
1981年 | 9篇 |
1980年 | 9篇 |
1979年 | 10篇 |
1978年 | 8篇 |
1977年 | 5篇 |
1976年 | 8篇 |
1957年 | 4篇 |
排序方式: 共有7724条查询结果,搜索用时 31 毫秒
21.
22.
Yang Woo Shin 《Operations Research Letters》2004,32(4):364-373
We consider a single server queue with disasters where the arrivals of customers and disasters are correlated. When a disaster occurs, it removes all the customers in the system and there requires repair time for the system to be operated normally. The stationary queue length distribution at the embedded points and at an arbitrary time are presented. 相似文献
23.
I. Peshko G. Galich M. Lopiychuk A. Khizhnyak V. Nakvasuk 《Optics & Laser Technology》1997,29(4):211-215
A laser system containing four CW Nd:YAG double-rod lasers, transforming optics and a fibre with input-output optics has been designed and investigated. It is shown that reduction of the beam parameter product of the non-Gaussian beams in the image space of the lens has made it possible to collect the emission of four lasers to the same fibre. Independent laser operation has provided the output power control in the range of 10–900 W with a stable light spot size on the input end of the fibre. 相似文献
24.
We establish the optimal asymptotic decay rate of per-session queue length tail distributions for a two-queue system where
a single constant rate server serves the two queues using the Generalized Processor Sharing (GPS) scheduling discipline. The
result is obtained using the sample-path large deviation principle and has implications in call admission control for high-speed
communication networks.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
25.
In this paper, we provide numerical means to compute the quasi-stationary (QS) distributions inM/GI/1/K queues with state-dependent arrivals andGI/M/1/K queues with state-dependent services. These queues are described as finite quasi-birth-death processes by approximating the general distributions in terms of phase-type distributions. Then, we reduce the problem of obtaining the QS distribution to determining the Perron-Frobenius eigenvalue of some Hessenberg matrix. Based on these arguments, we develop a numerical algorithm to compute the QS distributions. The doubly-limiting conditional distribution is also obtained by following this approach. Since the results obtained are free of phase-type representations, they are applicable for general distributions. Finally, numerical examples are given to demonstrate the power of our method. 相似文献
26.
Identification of nonlinear elliptic equations 总被引:1,自引:0,他引:1
An optimization theoretic approach and algorithm for the estimation of state-dependent coefficients in nonlinear elliptic equation is presented. It is based on a splitting method combined with convex analysis techniques. Convergence of the algorithm is established and numerical examples are included.The research of K. Kunisch was supported in part by a grant from the Bundesministerium für Wissenschaft und Forschung, Austria. 相似文献
27.
In this work two non-local problems for the parabolic-hyperbolic type equation with non-characteristic line of changing type
are considered. Unique solvability of these problems is proven. The uniqueness of the solution is proven by the method of
energy integrals and the existence is proven by the method of integral equations. 相似文献
28.
A. B. Vasil’eva A. A. Plotnikov 《Computational Mathematics and Mathematical Physics》2006,46(5):762-767
A singularly perturbed parabolic equation with a nonlinear right-hand side of a special form is examined. A numerical analytical study of such equations is performed. 相似文献
29.
Hong-Nian Li Xiao-Xiong WangWang-Feng Ding 《Journal of Electron Spectroscopy and Related Phenomena》2006
Using X-ray photoemission measurements, we have determined the attenuation length of C 1s photoelectrons in C60 film to be 21.5 Å with the incident photon energy of Mg Kα radiation. The inelastic mean free path calculated with the TPP-2M algorithm coincides fairly well with the experimentally determined attenuation length, indicating the validity of the algorithm to fullerene and fullerides. The inelastic mean free paths for some fullerides, i.e. K3C60, K6C60, Ba4C60, Sm2.75C60 and Sm6C60 are calculated to help the quantitative analyses of the photoemission spectra for these compounds. 相似文献
30.