全文获取类型
收费全文 | 13852篇 |
免费 | 2415篇 |
国内免费 | 778篇 |
专业分类
化学 | 2099篇 |
晶体学 | 79篇 |
力学 | 852篇 |
综合类 | 144篇 |
数学 | 4304篇 |
物理学 | 4201篇 |
无线电 | 5366篇 |
出版年
2024年 | 30篇 |
2023年 | 146篇 |
2022年 | 277篇 |
2021年 | 363篇 |
2020年 | 423篇 |
2019年 | 430篇 |
2018年 | 402篇 |
2017年 | 547篇 |
2016年 | 595篇 |
2015年 | 589篇 |
2014年 | 808篇 |
2013年 | 1136篇 |
2012年 | 920篇 |
2011年 | 989篇 |
2010年 | 793篇 |
2009年 | 802篇 |
2008年 | 897篇 |
2007年 | 846篇 |
2006年 | 782篇 |
2005年 | 678篇 |
2004年 | 592篇 |
2003年 | 594篇 |
2002年 | 529篇 |
2001年 | 452篇 |
2000年 | 389篇 |
1999年 | 342篇 |
1998年 | 253篇 |
1997年 | 258篇 |
1996年 | 198篇 |
1995年 | 165篇 |
1994年 | 123篇 |
1993年 | 93篇 |
1992年 | 75篇 |
1991年 | 75篇 |
1990年 | 54篇 |
1989年 | 49篇 |
1988年 | 35篇 |
1987年 | 36篇 |
1986年 | 32篇 |
1985年 | 53篇 |
1984年 | 33篇 |
1983年 | 18篇 |
1982年 | 28篇 |
1981年 | 25篇 |
1980年 | 9篇 |
1979年 | 19篇 |
1978年 | 14篇 |
1977年 | 13篇 |
1976年 | 11篇 |
1973年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
32.
ZHANG Zu-fan DU Hui-ping JIANG Ze Chongqing University of Posts Telecommunications Chongqing China University of Electronic Science Technology of China Chengdu China 《中国邮电高校学报(英文版)》2006,13(4):29-33
1 Introduction The calling dwell time characteristic is critical for the user network planning and deployment, e.g., global system for mobile communications (GSM), as well as the next generation wireless multimedia networks, such as, the currently standar… 相似文献
33.
ZhaoHongzhong ZhouJianxiong LiWeimin FuQiang 《电子科学学刊(英文版)》2003,20(6):401-406
High acceleration of radar targets is analyzed using Acceleration Ambiguity Function(AAF). The acceleration resolution based on AAF is defined. The AAF and acceleration resolution of rectangle pulse signal are derivated and the conclusion that its acceleration resolution is in inverse proportion with the square of its duration is drawn. In the end, these conclusions are applied to the parameter designing and performance evaluation for a certain type of pulse Doppler radar. 相似文献
34.
An algorithm for a time accurate incompressible Navier–Stokes solver on an unstructured grid is presented. The algorithm uses a second order, three‐point, backward difference formula for the physical time marching. For each time step, a divergence free flow field is obtained based on an artificial compressibility method. An implicit method with a local time step is used to accelerate the convergence for the pseudotime iteration. To validate the code, an unsteady laminar flow over a circular cylinder at a Reynolds number of 200 is calculated. The results are compared with available experimental and numerical data and good agreements are achieved. Using the developed unsteady code, an interaction of a Karman vortex street with an elliptical leading edge is simulated. The incident Karman vortex street is generated by a circular cylinder located upstream. A clustering to the path of the vortices is achieved easily due to flexibility of an unstructured grid. Details of the interaction mechanism are analysed by investigating evolutions of vortices. Characteristics of the interactions are compared for large‐ and small‐scale vortex streets. Different patterns of the interaction are observed for those two vortex streets and the observation is in agreement with experiment. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
35.
A time‐marching formulation is derived from the space–time integrated least squares (STILS) method for solving a pure hyperbolic convection equation and is numerically compared to various known methods. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
36.
通过理论分析和实验研究液晶分子附着能和液晶盒间隙对响应时间(τ0)的影响。用液晶盒有效间隙法和表面动力学方程法两种方法推出分析公式,由这两种方法推出的结果是一致的。实验数据与简化方程τ0-dx基本拟合(其中d是液晶盒的间隙,x是指数)。在两种极端的(极大或极小)附着能极限下,指数x分别接近2和1。这个结论有助于优化液晶显示器件的应用。 相似文献
37.
Nimrod Moiseyev Romanas Narevich 《International Journal of Theoretical Physics》2003,42(10):2131-2143
Resonances are defined as the poles of the scattering matrix. The poles are associated with the complex eigenvalues of the Hamiltonian which are embedded in the lower half of the complex plane. The asymptotes of the corresponding eigenfunctions are exponentially diverged. Therefore, the resonance eigenfunctions are not embedded in the Hermitian domain of the Hamiltonian. The time asymmetric problem is discussed for these types of non-Hermitian Hamiltonians and several solutions of this problem are proposed. 相似文献
38.
Alexander Afriat 《Foundations of Physics Letters》2003,16(3):293-301
An abstract treatment of Bell inequalities in proposed, in which the parameters characterizing Bell's observable can be times rather than directions. The violation of a Bell inequality might then be taken to mean that a property of a system can be changed by the timing of a distant measurement, which could take place in the future. 相似文献
39.
一种PN码自适应捕获门限的改进算法 总被引:1,自引:0,他引:1
文献[1]提出了一种用于直扩系统的PN码自适应门限算法。但该文献也指出,此算法对门限总数十分敏感。当门限总数设置不当时,系统的平均捕获时间将显著增加。这限制了该算法在实际中的应用。本文就此提出了改进,给出了算法及电路框图。仿真结果表明,与原方案相比,改进算法改善了对门限总数的敏感性,降低了PN码平均捕获时间。 相似文献
40.
We study the vessel arrival process in bulk ports handling either cargo containers or minerals. Then we introduce the SHIP/G/1 queue to be able to study the queueing behavior at the port. We present approximations for the asymptotic probabilities of delay and the number of vessels at the port. Numerical examples show the accuracy of the approximations. In appendices, we provide details of the analysis of the number of vessels at the port and the correlation properties of the vessel arrival process. 相似文献