首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   135860篇
  免费   2799篇
  国内免费   844篇
电工技术   2117篇
综合类   156篇
化学工业   23645篇
金属工艺   4678篇
机械仪表   3887篇
建筑科学   5372篇
矿业工程   783篇
能源动力   3611篇
轻工业   11515篇
水利工程   1456篇
石油天然气   2495篇
武器工业   48篇
无线电   11387篇
一般工业技术   26836篇
冶金工业   22660篇
原子能技术   3044篇
自动化技术   15813篇
  2022年   1308篇
  2021年   2114篇
  2020年   1474篇
  2019年   1728篇
  2018年   2822篇
  2017年   2675篇
  2016年   3130篇
  2015年   2174篇
  2014年   3414篇
  2013年   7554篇
  2012年   5158篇
  2011年   6447篇
  2010年   5133篇
  2009年   5243篇
  2008年   5698篇
  2007年   5441篇
  2006年   4716篇
  2005年   4221篇
  2004年   3791篇
  2003年   3598篇
  2002年   3433篇
  2001年   2824篇
  2000年   2646篇
  1999年   2600篇
  1998年   4956篇
  1997年   3723篇
  1996年   2942篇
  1995年   2446篇
  1994年   2187篇
  1993年   2223篇
  1992年   1761篇
  1991年   1575篇
  1990年   1704篇
  1989年   1692篇
  1988年   1484篇
  1987年   1427篇
  1986年   1389篇
  1985年   1617篇
  1984年   1424篇
  1983年   1276篇
  1982年   1144篇
  1981年   1207篇
  1980年   1089篇
  1979年   1087篇
  1978年   1025篇
  1977年   1170篇
  1976年   1346篇
  1975年   919篇
  1974年   838篇
  1973年   813篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
A wafer level packaging technique has been developed with an inherent advantage of good solder joint co-planarity suitable for wafer level testing. A suitable weak metallization scheme has also been established for the detachment process. During the fabrication process, the compliancy of the solder joint is enhanced through stretching to achieve a small shape factor. Thermal cycling reliability of these hourglass-shaped, stretch solder interconnections has been found to be considerably better than that of the conventional spherical-shaped solder bumps.  相似文献   
52.
Porous carbon nanofibers are synthesized by CVD method from acetylene with use of iron-containing catalysts. Activation of the nanofibers in melted potassium hydroxide results in increasing surface area from initial 300–400 m2 g−1 to 1700 m2 g−1. As follows from XRD data, activated nanofibers do not contain regular packages of graphene layers, but retain high electric conductivity. Deposition of copper improves electrochemical hydrogen storing characteristics of carbon nanofibers. Carbon nanomaterials obtained can be used as hydrogen storing materials in batteries instead of hydride forming metals.  相似文献   
53.
54.
The results of a computational experiment with a neural-net model simulating the effect of the chemical composition on the plastic properties of ÉP-450 steel are presented. It is shown that computer-aided development of reactor steel with prescribed properties is, in principle, possible.  相似文献   
55.
串行多路传输总线如CAN或LIN可以解决车内因导线过多所带来的许多问题。低成本的LIN总线很适合应用于车门等这些对传输速率要求不高的场合,最高速率为20kbit/s的LIN总线完全可以满足要求。车外温度显示就是这样一个应用实例,外部温度传感器通常布置在后视镜中,数据产生于车门。但是实际显示位置是距此一定距离的车内,LIN总线可使布线简单,因为LIN节点只有3根导线:LIN数据线、电源线和地线。  相似文献   
56.
The dielectric and pyroelectric properties of Ge-doped (0.1 mol %) TlInS2 crystals are studied. The results demonstrate that TlInS2 is a ferroelectric relaxor. The experimental data are used to evaluate, using the Vogel–Fulcher relation, the activation energy (0.045 eV), preexponential factor (f 0 = 2 × 1013 Hz), and the dipole-freezing temperature (T F = 142 K) and to determine the temperature range of the stable relaxor (nanodomain) state and the temperature of the transition to the ferroelectric (macrodomain) state, accompanied by an anomaly in the temperature-dependent pyroelectric coefficient.  相似文献   
57.
58.
A rheological equation of state for wood which allows for the running values of its porosity and humidity is considered.  相似文献   
59.
In this paper we design an experiment which can be depicted as a simple scenario, a very limited 'world'. In this world, there are an actor that can pursue a project and an observer that is keeping its eyes on the actor. We try to show in the experiment that the observer can to some degree understand the actor based on its knowledge and some metaphors, i.e. understand what the actor is doing and why. As the conclusion of this experiment, we try to show some features of 'understanding'. These are (1) that 'understanding' has to be based on some preliminary knowledge; (2) that 'understanding' is a process of incremental learning; (3) that, as for symbolic systems, some metaphors are necessary for mapping real entities into concepts in mind.  相似文献   
60.
Conclusions The chemical mutagenesis method is recommended for use in local purification installations for cleaning up of caprolactam-containing wastewater.Use of this method permits one to carry out a biochemical clean-up of wastewater having a caprolactam content up to 600 mg/liter while increasing the oxidative power of the aeration tank by a factor of two.Translated from Khimicheskie Volokna, No. 6, p. 46, November–December, 1985.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号