全文获取类型
收费全文 | 13704篇 |
免费 | 1134篇 |
国内免费 | 725篇 |
专业分类
化学 | 1577篇 |
晶体学 | 46篇 |
力学 | 1945篇 |
综合类 | 85篇 |
数学 | 2007篇 |
物理学 | 3017篇 |
综合类 | 6886篇 |
出版年
2024年 | 46篇 |
2023年 | 160篇 |
2022年 | 300篇 |
2021年 | 362篇 |
2020年 | 395篇 |
2019年 | 313篇 |
2018年 | 320篇 |
2017年 | 390篇 |
2016年 | 463篇 |
2015年 | 488篇 |
2014年 | 639篇 |
2013年 | 824篇 |
2012年 | 737篇 |
2011年 | 802篇 |
2010年 | 587篇 |
2009年 | 727篇 |
2008年 | 642篇 |
2007年 | 856篇 |
2006年 | 717篇 |
2005年 | 586篇 |
2004年 | 548篇 |
2003年 | 547篇 |
2002年 | 437篇 |
2001年 | 413篇 |
2000年 | 462篇 |
1999年 | 362篇 |
1998年 | 302篇 |
1997年 | 328篇 |
1996年 | 223篇 |
1995年 | 224篇 |
1994年 | 203篇 |
1993年 | 202篇 |
1992年 | 173篇 |
1991年 | 150篇 |
1990年 | 124篇 |
1989年 | 97篇 |
1988年 | 109篇 |
1987年 | 87篇 |
1986年 | 43篇 |
1985年 | 32篇 |
1984年 | 16篇 |
1983年 | 10篇 |
1982年 | 18篇 |
1981年 | 14篇 |
1980年 | 9篇 |
1979年 | 19篇 |
1977年 | 8篇 |
1973年 | 13篇 |
1971年 | 6篇 |
1957年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 156 毫秒
71.
由于储存环中各种元件误差的存在, 机器的实际运行模式与设计模式有一定的偏差. 目前广泛开展的响应矩阵方法研究, 可以分析出磁铁元件以及束流位置测量元件的误差, 使束流基本参数得到校正. 介绍了用响应矩阵分析方法, 在BEPC储存环上进行的局部轨道校正的实验研究, 以及BEPC储存环束流参数校正的模拟研究. 相似文献
72.
Given a constant of motion for the one-dimensional harmonic oscillator with linear dissipation in the velocity, the problem to get the Hamiltonian for this system is pointed out, and the quantization up to second order in the perturbation approach is used to determine the modification on the eigenvalues when dissipation is taken into consideration. This quantization is realized using the constant of motion instead of the Hamiltonian.
PACS: 03.20.+i, 03.30.+p, 03.65.−w,03.65.Ca 相似文献
73.
王晓瑛 《纯粹数学与应用数学》2002,18(4):367-370
构造了一类新的分数布朗运动模型,它不同于Mandelbrot,Barton及Decreusefond等人所定义的分数布朗运动模型。 相似文献
74.
本文在M ogens B ladt和T ina H av iid R ydberg无市场假设,仅利用价格过程的实际概率的期权保险精算定价模型的基础上,得出了标的资产服从几何分数布朗运动的欧式期权定价公式,并说明了几何布朗运动是本文的一种特殊情况. 相似文献
75.
It is shown that the condition υ > υp (ω), which is necessary in order to trigger the Vavilov-Cherenkov effect, determines the interval of radiated frequencies
and it alone cannot establish a strong restriction to the velocity of the particle. It is exhibited that it is possible to
define a general lower bound for the velocity of the particle, which does not depend on the frequency when both, a specific
response of the medium is taken into account and the mentioned condition is considered. The minimum value of the phase velocity
of light in the medium determines the existence of such general lower bound. 相似文献
76.
3 - dimensional body measurement technology, the basis of developing high technology in industry, accelerates digital development of aplparel industry. This paper briefly introduces the history of 3 - dimensional body measurement technology, and recounts the principle and primary structure of some types of 3 - dimensional automatic body measurement system. With this understanding, it discusses prospect of 3 - dimensional CAD and virtual technology used in apparel industry. 相似文献
77.
报道淀积条件对以非晶态硒化镉(a-CdSe)为光敏介质的超快光电探测器瞬态响应特性的影响. 相似文献
78.
偶氮苯衍生物三阶非线性的四波混频研究 总被引:7,自引:0,他引:7
用皮秒Nd:YAG激光器的倍频光(532nm)对具有离域π-共轭电子云结构的偶氮苯类样品材料作简并四波混频补给,测得三阶非线性电极化率x^(3)和它们的时间响应分别为10^-9esu和20ps,并对影响x^(3)的瞬时光栅作用和x^(3)的响应时间人了讨论。 相似文献
79.
Hu Haiyan 《Acta Mechanica Solida Sinica》1994,7(2):137-150
This paper deals with the numerical solution of high dimensional dynamic systems with nonsmooth characteristics, such as structural elastoplasticity, mechanical clearance and dry friction. As a stable periodic response of the system attracts its transient response, it may be extracted from the transient response somehow. The paper suggests a novel iteration scheme to extrapolate the periodic response from a short time history of its transient response by curve fitting. Compared with the current schemes such as shooting and incremental harmonic balancing, the present scheme makes full use of the information within the transient response and the system characters, then its computation efficiency has increased by an order and the numerical convergence depending on the initial iteration has greatly improved.The subject supported by the Chinese Foundation of Aeronautical Science 相似文献
80.
Non-Markovian Brownian motion in a periodic potential is studied by means of an electronic analogue simulator. Velocity spectra, the Fourier transforms of velocity autocorrelation functions, are obtained for three types of random force, that is, a white noise, an Ornstein—Uhlenbeck process, and a quasimonochromatic noise. The analogue results are in good agreement both with theoretical ones calculated with the use of a matrix-continued-fraction method, and with the results of digital simulations. An unexpected extra peak in the velocity spectrum is observed for Ornstein-Uhlenbeck noise with large correlation time. The peak is attributed to a slow oscillatory motion of the Brownian particle as it moves back and forth over several lattice spaces. Its relationship to an approximate Langevin equation is discussed. 相似文献