全文获取类型
收费全文 | 20902篇 |
免费 | 547篇 |
国内免费 | 509篇 |
专业分类
化学 | 11489篇 |
晶体学 | 150篇 |
力学 | 1526篇 |
综合类 | 60篇 |
数学 | 2897篇 |
物理学 | 5836篇 |
出版年
2020年 | 313篇 |
2019年 | 387篇 |
2018年 | 443篇 |
2017年 | 406篇 |
2016年 | 567篇 |
2015年 | 308篇 |
2014年 | 491篇 |
2013年 | 687篇 |
2012年 | 709篇 |
2011年 | 723篇 |
2010年 | 676篇 |
2009年 | 680篇 |
2008年 | 672篇 |
2007年 | 678篇 |
2006年 | 555篇 |
2005年 | 512篇 |
2004年 | 484篇 |
2003年 | 505篇 |
2002年 | 556篇 |
2001年 | 545篇 |
2000年 | 380篇 |
1999年 | 314篇 |
1998年 | 288篇 |
1997年 | 270篇 |
1996年 | 254篇 |
1995年 | 246篇 |
1993年 | 256篇 |
1992年 | 253篇 |
1991年 | 259篇 |
1990年 | 295篇 |
1989年 | 275篇 |
1986年 | 245篇 |
1985年 | 277篇 |
1984年 | 281篇 |
1983年 | 260篇 |
1982年 | 274篇 |
1980年 | 255篇 |
1979年 | 303篇 |
1978年 | 333篇 |
1977年 | 322篇 |
1976年 | 404篇 |
1975年 | 358篇 |
1974年 | 391篇 |
1973年 | 396篇 |
1972年 | 368篇 |
1971年 | 331篇 |
1970年 | 314篇 |
1969年 | 298篇 |
1968年 | 253篇 |
1967年 | 250篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
薄原子蒸汽膜的单光子Dcike窄化吸收光谱可以拓展到双光子情形,以级联三能级系统为例,从理论上得到了亚多普勒结构的双光子吸收光谱,其线型表现出和单光子过程相似的与膜厚和探测光波长的比值(L/λ)相关的周期性.当L/λ=(2n+1)/2(膜厚为半波长的奇数倍)时,吸收谱线窄化现象明显.当L/λ=2n/2(膜厚为半波长的偶数倍)时,单光子情形的谱线窄化现象消失,而双光子情形的谱线仍表现为亚多普勒结构,尤其在异侧入射的情形下,可以获得极窄的双光子谱线结构. 这种结构来自原子与腔壁碰撞的消激发效应和双光子过程的抽运-探测机制的贡献.
关键词:
薄原子蒸汽膜
双光子光谱
Dicke窄化 相似文献
112.
The temporal characteristics of stimulated Raman scattering (SRS) under 22-ps laser excitation were studied in eight oxide crystals with a T 2 optical-phonon dephasing time variable by up to two orders of magnitude. The measured SRS pulse width was shortened from 13.8 ps for Ba(NO3)2 (T 2 = 26.5 ps) to 4 ps for the LiNbO3 (T 2 = 0.38 ps) crystal. The dependence of SRS pulse width on the dephasing time was analyzed in the framework of the known SRS theory. 相似文献
113.
Alexander Ya. Kruger 《Set-Valued Analysis》2006,14(2):187-206
The paper continues investigations of stationarity and regularity properties of collections of sets in normed spaces. It contains
a summary of different characterizations (both primal and dual) of regularity and a list of sufficient conditions for a collection
of sets to be regular. 相似文献
114.
We analyze the statistical behavior of signals in nonlinear circuits with delayed feedback in the presence of external Markovian noise. For the special class of circuits with intense phase mixing we develop an approach for the computation of the probability distributions and multitime correlation functions based on the random phase approximation. Both Gaussian and Kubo-Andersen models of external noise statistics are analyzed and the existence of the stationary (asymptotic) random process in the long-time limit is shown. We demonstrate that a nonlinear system with chaotic behavior becomes a noise amplifier with specific statistical transformation properties. 相似文献
115.
P. Ya. Malits 《Journal of Mathematical Sciences》1991,57(5):3417-3420
We consider the pressure of a plate on a half-space with a round cylindrical cavity. The surface of the cavity is reinforced by elastic elements that are modeled by very general operators. The problem is reduced to a Fredholm integral equation of second kind. A detailed study is made of the case of reinforcement described by the Winkler law. An approximate solution is obtained in the form of the asymptotics with respect to the radii of the plate and the cavity.Translated fromDinamicheskie Sistemy, No. 6, 1987, pp. 80–85. 相似文献
116.
V. N. Volynets D. I. Slovetskii A. Ya. Strochkov V. N. Trofimov 《Journal of Applied Spectroscopy》1991,54(6):613-619
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 54, No. 6, pp. 1004–1010, June, 1991. 相似文献
117.
118.
119.
An approach is proposed to solving multipoint boundary-value problems for linear differential equation of w-th order, based on reduction to two-point boundary-value problems. The two-point problems are solved by the stable discrete orthogonalization method. Some numerical examples are considered.Translated from Vychislitel'naya i Prikladnaya Matematika, No. 58, pp. 36–45, 1986. 相似文献
120.
We prove an existence theorem and establish the property of stochastic stability for processes determined by the Poisson stochastic differential equations with delay. 相似文献