全文获取类型
收费全文 | 5174篇 |
免费 | 784篇 |
国内免费 | 408篇 |
专业分类
化学 | 1335篇 |
晶体学 | 59篇 |
力学 | 681篇 |
综合类 | 30篇 |
数学 | 273篇 |
物理学 | 2127篇 |
无线电 | 1861篇 |
出版年
2024年 | 9篇 |
2023年 | 65篇 |
2022年 | 110篇 |
2021年 | 97篇 |
2020年 | 136篇 |
2019年 | 116篇 |
2018年 | 117篇 |
2017年 | 156篇 |
2016年 | 233篇 |
2015年 | 239篇 |
2014年 | 323篇 |
2013年 | 370篇 |
2012年 | 336篇 |
2011年 | 385篇 |
2010年 | 282篇 |
2009年 | 324篇 |
2008年 | 325篇 |
2007年 | 344篇 |
2006年 | 357篇 |
2005年 | 260篇 |
2004年 | 247篇 |
2003年 | 213篇 |
2002年 | 174篇 |
2001年 | 152篇 |
2000年 | 160篇 |
1999年 | 122篇 |
1998年 | 118篇 |
1997年 | 83篇 |
1996年 | 80篇 |
1995年 | 86篇 |
1994年 | 63篇 |
1993年 | 54篇 |
1992年 | 50篇 |
1991年 | 40篇 |
1990年 | 37篇 |
1989年 | 19篇 |
1988年 | 17篇 |
1987年 | 9篇 |
1986年 | 9篇 |
1985年 | 14篇 |
1984年 | 9篇 |
1983年 | 4篇 |
1982年 | 6篇 |
1981年 | 8篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1977年 | 2篇 |
1976年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有6366条查询结果,搜索用时 0 毫秒
1.
2.
3.
在目标信号检测模块的基础上增加了测有计算模块,构成一种新型的单脉冲雷达点迹提取器,显著提高了雷达系统潜在的处理能力。 相似文献
4.
Belov V. V. Dobrokhotov S. Yu. Maksimov V. A. 《Theoretical and Mathematical Physics》2003,135(3):765-791
Different versions of the Darboux–Weinstein theorem guarantee the existence of action–angle-type variables and the harmonic-oscillator variables in a neighborhood of isotropic tori in the phase space. The procedure for constructing these variables is reduced to solving a rather complicated system of partial differential equations. We show that this system can be integrated in quadratures, which permits reducing the problem of constructing these variables to solving a system of quadratic equations. We discuss several applications of this purely geometric fact in problems of classical and quantum mechanics. 相似文献
5.
CAO Wei-feng WANG Wen-boBeijing University of Posts Telecommunications Beijing P.R. China 《中国邮电高校学报(英文版)》2005,12(4)
1IntroductionCurrently,smart antenna technology can greatly en-hance system performance and i mprove the system ca-pacity so that it has been considered as a keytechnologyinthe third generation wireless communicationsystems .The researches on channel model , beamforming algo-rithms and receive algorithms have been widely carriedout and a great many of proposition have beensubmittedtothe 3th Generation Project Partner (3GPP) . Fromthe viewpoint of link-level and system-level research,many asp… 相似文献
6.
7.
通过用毛细管测量纯水表面张力系数实验,得到管内径d与接触角θ的相对误差之间的关系曲线,由此说明实验测得的表面张力系数α和理论公式相比呈现一定的偏差,并简单地讨论了实验的理想状态与实际情况的差别. 相似文献
8.
George Z. Papageorgiou George P. Karayannidis Dimitris N. Bikiaris Anagnostis Stergiou George Litsardakis Sofoklis S. Makridis 《Journal of Polymer Science.Polymer Physics》2004,42(5):843-860
The crystallization behavior of a series of poly(ethylene‐co‐butylene naphthalate) (PEBN) random copolymers was studied. Wide‐angle X‐ray diffraction (WAXD) patterns showed that the crystallization of these copolymers could occur over the entire range of compositions. This resulted in the formation of poly(ethylene naphthalate) or poly(butylene naphthalate) crystals, depending on the composition of the copolymers. Sharp diffraction peaks were observed, except for 50/50 PEBN. Eutectic behavior was also observed. This showed isodimorphic cocrystallization of the PEBN copolymers. The variation of the enthalpy of fusion of the copolymers with the composition was estimated. The isothermal and nonisothermal crystallization kinetics were studied. The crystallization rates were found to decrease as the comonomer unit content increased. The tensile properties were also measured and were found to decrease as the butylene naphthalate content of the copolymers increased. For initially amorphous specimens, orientation was proved by WAXD patterns after drawing, but no crystalline reflections were observed. However, the fast crystallization of drawn specimens occurred when they were heated above the glass‐transition temperature. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 843–860, 2004 相似文献
9.
Becky Lavi Abraham Marmur 《Colloids and surfaces. A, Physicochemical and engineering aspects》2004,250(1-3):409-414
An equation for the kinetics of partial drop spreading is proposed. This equation was empirically derived from experimental data for the spreading kinetics of partially wetting liquids in terms of the wet area versus time. The equation has the form of an exponential power law (EPL), and transforms into the well-known power law for complete wetting, when the equilibrium contact angle approaches zero. The EPL fits very well available experimental data. To lend additional support to the validity of this generalized equation, it will be demonstrated that when it is transformed to present the dynamic contact angle (DCA), it fits very well DCA experimental data for other wetting processes, such as capillary flow and tape coating. 相似文献
10.