全文获取类型
收费全文 | 5598篇 |
免费 | 754篇 |
国内免费 | 522篇 |
专业分类
化学 | 1425篇 |
晶体学 | 69篇 |
力学 | 862篇 |
综合类 | 38篇 |
数学 | 281篇 |
物理学 | 1417篇 |
无线电 | 2782篇 |
出版年
2024年 | 11篇 |
2023年 | 109篇 |
2022年 | 110篇 |
2021年 | 172篇 |
2020年 | 215篇 |
2019年 | 158篇 |
2018年 | 134篇 |
2017年 | 177篇 |
2016年 | 217篇 |
2015年 | 220篇 |
2014年 | 316篇 |
2013年 | 414篇 |
2012年 | 322篇 |
2011年 | 336篇 |
2010年 | 267篇 |
2009年 | 327篇 |
2008年 | 330篇 |
2007年 | 349篇 |
2006年 | 345篇 |
2005年 | 309篇 |
2004年 | 311篇 |
2003年 | 268篇 |
2002年 | 214篇 |
2001年 | 195篇 |
2000年 | 170篇 |
1999年 | 132篇 |
1998年 | 128篇 |
1997年 | 93篇 |
1996年 | 97篇 |
1995年 | 87篇 |
1994年 | 61篇 |
1993年 | 52篇 |
1992年 | 32篇 |
1991年 | 32篇 |
1990年 | 39篇 |
1989年 | 29篇 |
1988年 | 24篇 |
1987年 | 8篇 |
1986年 | 12篇 |
1985年 | 8篇 |
1984年 | 7篇 |
1983年 | 4篇 |
1982年 | 12篇 |
1981年 | 2篇 |
1980年 | 5篇 |
1979年 | 3篇 |
1977年 | 1篇 |
1975年 | 1篇 |
1971年 | 4篇 |
1957年 | 4篇 |
排序方式: 共有6874条查询结果,搜索用时 156 毫秒
61.
Excessive intermetallic compound (IMC) growth in solder joints will significantly decrease the reliability of the joints.
IMC growth is known to be influenced by numerous factors during the component fabrication process and in service. It is reported
that, other than temperature and holding time, stress can also influence the IMC growth behavior. However, no existing method
can be used to study the effect of stress state on IMC growth in a controlled manner. This paper presents a novel method to
study the effect of stress on interfacial IMC growth between Sn-Ag-Cu solder and a Cu substrate coated with electroless Ni
immersion Au (ENIG). A C-ring was used and in-plane bending induced tensile and compressive stresses were applied by tightening
the C-ring. Results revealed that in-plane compressive stress led to faster IMC growth as compared with in-plane tensile stress. 相似文献
62.
SDI接口数字监视设备的设计与实现 总被引:2,自引:0,他引:2
介绍了一种对SDV(串行数字视频)信号进行解码的设备设计方案,提出了该系统的总体构架,并对该系统的硬件设计、软件设计进行了全面的论述。设计的产品具有较高的性能价格比,已进入了推广阶段。 相似文献
63.
64.
界面应力的正确评价是分析薄膜涂层材料力学特性的难题之一。利用镜像点法和Dirichlet等值性原理,本文推导了等厚双层薄膜涂层材料受表面集中力作用的平面问题理论解。该显式理论解是以固定在各镜像点上的局部坐标系下的Goursat应力函数的形式给出的。对应于高阶镜像点的应力函数,可通过递推的方法,从对应于低阶镜像点的应力函数求得,而且也易于计算机编程。随着镜像点阶数的增大,它与界面的距离也越来越大,因而相对应的应力函数对界面应力的影响越来越小。最后的算例表明,只需考虑前面有限个镜像点,便可获得足够精度的解。该理论解可作为格林函数,以求解复杂问题的理论解,也可用作边界元法的基本解,提高数值计算的精度和效率。 相似文献
65.
66.
Charging of the surface of an oxide caused by the adsorption of hydrogen ions and ions of inert 1:1 electrolyte was investigated by using grand canonical Monte Carlo simulation technique. In particular, adsorption isotherms of protons as well as of ions of the electrolyte together with the resulting charge density of the surface were obtained for different system parameters. Also, the effect of the surface energetic heterogeneity and the concentration of the background electrolyte on the isotherms and the charge density curves was examined. Furthermore, lateral interactions in the mixed adsorbed phase were taken into account in the modeling of the system behavior. The obtained results, in general, suggest that the three factors mentioned above may have substantial influence on the charging mechanism at the liquid/oxide interface. 相似文献
67.
The article analyzes the influence of the Internet Protocol (IP) access interface on the packet loss probability and delay
times in the optical packet switched network. The network and node model have been proposed, and the structure of the IP access
interface, including assembler and holder, have been included in the analysis. It has been shown that the increase of the
maximum optical packet sizes, as well as use of the holding feature as contention resolution mechanism, decrease the packet
loss probability, but introduce delays at the optical network access points. Modeling and analysis were based on the discrete
event simulation assuming self-similar traffic sources. IP packet lengths were modeled using empirical data.
This work has been conducted while the author was affiliated with the Telecommunication Laboratory, Swiss Federal Institute
of Technology (EPFL-STI-ITOP-TCOM), Lausanne, Switzerland 相似文献
68.
69.
70.
杨力平 《应用数学学报(英文版)》1994,10(3):233-251
FREEBOUNDARYPROBLEMARISINGFROMEVAPORATIONFROMPOROUSMEDIUMYANGLIPING(杨力平)(DepartmentofAppliedMathematics,TsinghuaUniversity,Be... 相似文献