全文获取类型
收费全文 | 221621篇 |
免费 | 2066篇 |
国内免费 | 535篇 |
专业分类
化学 | 118161篇 |
晶体学 | 3574篇 |
力学 | 10640篇 |
综合类 | 11篇 |
数学 | 24747篇 |
物理学 | 67089篇 |
出版年
2021年 | 2156篇 |
2020年 | 2281篇 |
2019年 | 2835篇 |
2018年 | 3835篇 |
2017年 | 3844篇 |
2016年 | 5192篇 |
2015年 | 2686篇 |
2014年 | 4725篇 |
2013年 | 9471篇 |
2012年 | 7761篇 |
2011年 | 9250篇 |
2010年 | 7046篇 |
2009年 | 7149篇 |
2008年 | 8582篇 |
2007年 | 8627篇 |
2006年 | 7712篇 |
2005年 | 6920篇 |
2004年 | 6479篇 |
2003年 | 5866篇 |
2002年 | 5849篇 |
2001年 | 5833篇 |
2000年 | 4382篇 |
1999年 | 3350篇 |
1998年 | 2907篇 |
1997年 | 2988篇 |
1996年 | 2804篇 |
1995年 | 2428篇 |
1994年 | 2526篇 |
1993年 | 2461篇 |
1992年 | 2713篇 |
1991年 | 2822篇 |
1990年 | 2710篇 |
1989年 | 2758篇 |
1988年 | 2667篇 |
1987年 | 2703篇 |
1986年 | 2543篇 |
1985年 | 3230篇 |
1984年 | 3344篇 |
1983年 | 2772篇 |
1982年 | 2776篇 |
1981年 | 2764篇 |
1980年 | 2510篇 |
1979年 | 2886篇 |
1978年 | 2885篇 |
1977年 | 3021篇 |
1976年 | 3026篇 |
1975年 | 2813篇 |
1974年 | 2764篇 |
1973年 | 2848篇 |
1972年 | 2153篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
981.
982.
The effect of annealing in a hydrogen atmosphere on the transmission spectra of GaP:N light-emitting diodes at temperatures of 550, 570, and 590 °C has been investigated. Temperature-induced rearrangement of defects has been observed. The band gap of the material studied is determined. The dependence of the transmission and difference transmission spectra on the annealing temperature and the effect of annealing on the electroluminescence spectra are shown. 相似文献
983.
Abakumov G. A. Druzhkov N. O. Kurskii Yu. A. Shavyrin A. S. 《Russian Chemical Bulletin》2003,52(3):712-717
Products of thermal transformation of substituted N-aryl-o-quinoneimines were studied using NMR spectroscopy. The formation of 4aH-phenoxazine, which was further dimerized by the Diels—Alder reaction, was established. 相似文献
984.
P. V. Pavlov I. V. Babushkin N. A. Loiko N. N. Rosanov S. V. Fedorov 《Radiophysics and Quantum Electronics》2004,47(10-11):898-904
We consider spatial dissipative solitons arising in the system of two nonlinear thin films which interact resonantly with light. Symmetric and nonsymmetric solitons and methods of their exciting and switching are studied. 相似文献
985.
986.
Transversely one-dimensional moving and oscillating solitons in a wide-aperture laser with saturable absorber with fast (inertialess) nonlinearity are found by numerical simulation. The regions of existence of such solitons and of their complexes are presented. 相似文献
987.
988.
The following areal objects are considered: an ether thread contracting two material points and a multidimensional ether fibre in the pseudo-Euclidean world of events. An ether space-time model with an arbitrarily determined Riemannian metric is constructed and the problem of the λ term in Einstein equations is discussed in this regard. 相似文献
989.
990.
A Network Simulation of High-congestion Road-traffic Flows in Cities with Marine Container Terminals
James A. Pope Terry R. Rakes Loren Paul Rees Ingrid W. M. Crouch 《The Journal of the Operational Research Society》1995,46(9):1090-1101
Port cities where marine cargo terminals are located are generally near urban areas characterized by high-congestion road traffic. Changes in cargo traffic volumes into a marine terminal, or in the surrounding traffic arteries, which carry this traffic, can significantly affect the terminal's operations. Conversely, activity at the terminal can have an impact on the traffic levels and congestion for a considerable distance from the terminal. This paper demonstrates a methodology useful for studying the impact of road traffic flows on marine container terminals located in highly congested areas. This model was developed at the request of the Virginia Center for World Trade and was used to answer three planning questions in the port of Hampton Roads, Virginia, USA-what would be the impact of: opening a new section of interstate highway, a projected doubling of container traffic at one terminal, and a daily unit train in the vicinity of another terminal. The problem was made more challenging by limited data-collection funds. None the less, the model was deemed valid by a panel of traffic experts and officials from several major state and private agencies involved in marine traffic management. The model results were subsequently a factor in two major decisions related to terminal management. 相似文献