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   28352篇
  免费   1854篇
  国内免费   1173篇
电工技术   633篇
综合类   2135篇
化学工业   3569篇
金属工艺   1044篇
机械仪表   1406篇
建筑科学   1872篇
矿业工程   509篇
能源动力   995篇
轻工业   1448篇
水利工程   175篇
石油天然气   817篇
武器工业   142篇
无线电   2963篇
一般工业技术   4086篇
冶金工业   1393篇
原子能技术   160篇
自动化技术   8032篇
  2024年   32篇
  2023年   337篇
  2022年   622篇
  2021年   558篇
  2020年   603篇
  2019年   712篇
  2018年   497篇
  2017年   686篇
  2016年   766篇
  2015年   709篇
  2014年   1043篇
  2013年   1058篇
  2012年   1400篇
  2011年   1525篇
  2010年   931篇
  2009年   1368篇
  2008年   1135篇
  2007年   1127篇
  2006年   1044篇
  2005年   875篇
  2004年   1502篇
  2003年   1229篇
  2002年   1810篇
  2001年   1474篇
  2000年   1311篇
  1999年   1116篇
  1998年   687篇
  1997年   718篇
  1996年   1631篇
  1995年   904篇
  1994年   656篇
  1993年   191篇
  1992年   160篇
  1991年   183篇
  1990年   152篇
  1989年   88篇
  1988年   71篇
  1987年   51篇
  1986年   70篇
  1985年   76篇
  1984年   53篇
  1983年   37篇
  1982年   39篇
  1981年   36篇
  1980年   14篇
  1979年   17篇
  1978年   10篇
  1977年   8篇
  1975年   6篇
  1973年   7篇
排序方式: 共有10000条查询结果,搜索用时 171 毫秒
151.
民族特色词语的英汉互译   总被引:1,自引:0,他引:1  
语言在其发展演变过程中,逐步具有了鲜明的民族文化色彩。阐述了民族特色词语的可译性,并提出了具体的翻译方法。  相似文献   
152.
郭传顺 《化工时刊》2003,17(3):49-50
对氨基二苯胺是性能优异的对苯二胺类防老剂的中间体。其质量好坏直接关系到防老剂4020、4010NA、688等品种的质量。对氨基二苯胺质量检验方法的提出则有助于我们开拓思路,更新质量观念,地症下药,分析原因,采取措施,全面提高其内在质量。  相似文献   
153.
We report the successful growth of Ga-polar GaN epilayers on O-polar ZnO templates pre-deposited on c-sapphire. Prior to GaN growth, NH3 is exposed onto the ZnO template. The polarity of the GaN layers is confirmed by etching of the surface and by conversion beam electron diffraction (CBED), while the O-polar ZnO is confirmed by CBED. It is suggested that the NH3 pre-exposure helps form a Zn3N2 layer, which possesses inversion symmetry and inverts the crystal from anion polar to cation polar.  相似文献   
154.
本文综述了随机度量理论在近十年来的重要进展及其具有代表性的某些应用。  相似文献   
155.
Decision support for AIDS control programmes in Eastern Africa   总被引:1,自引:1,他引:0  
The Acquired Immune Deficiency Syndrome (AIDS) constitutes the worst hazard to health care systems in Eastern Africa. Misallocation of scarce resources of AIDS Control Programmes will unavoidably lead to additional infections and casualties. The following paper discusses a system dynamics model which allows to assess the impact of different interventions on a pattern population in Eastern Africa. It becomes obvious that short- and long-term consequences of these programmes differ significantly. The optimal allocation of resources, therefore, is highly complex and calls for decision support systems to sustain AIDS control programmes.  相似文献   
156.
Argon blowing at the ladle shroud requires the best flow control strategy to effectively avoid the secondary oxidation of molten steel, slag entrapment and heat loss during the casting of the tundish, and at the same time, give full play to the role of bubbles to remove inclusions. Therefore, an automatic control system for argon blowing at the ladle shroud was proposed. The data collected by S7-300PLC and software programming were used to adjust the argon blowing flow online in real time according to factors such as pouring and continuous pouring. On this basis, PID control algorithm and closed loop control mechanism were used for real time adjustment. The flow control valve ensures theminimum deviation between the actual value of the flow and the set value. The production data of this system in the first quarter of 2021 in a special steel plant show that the proportion of furnaces with an acid soluble aluminum (Als) loss percentage of less than 10% of each steel grade has increased by 5.52%, and the proportion of furnaces with an Als loss percentage of more than 60% has increased from 1% decrease to 0. The actual application results show that the use of the system improves the surface quality of the continuous casting slab and the performance of the final product.  相似文献   
157.
The object of study is a stationary Gaussian white noise excited multi-degree-of-freedom (MDOF) linear elastic, ideal plastic, linearly damped, statically determinate oscillator with several potential elements of ideal plastic yielding. Specifically the study is exemplified for a plane multistory shear frame with rigid traverses where all the connecting columns except the columns in one or more of the bottom floors have finite symmetrical yield limits. The white noise excitation acts on the mass of the first floor making the movement of the elastic bottom floors simulate a ground motion that interacts with the structure above the bottom floors. The method of study is so-called Slepian model simulation and is in principle the same for other statically determinate MDOF elasto-plastic oscillators of the considered type. The method is fast as compared to direct simulation and provides results that give good insight in the behavior of the plastic displacement response process.  相似文献   
158.
转动玻璃圆筒激光器   总被引:1,自引:0,他引:1  
本文介绍了转动玻璃圆筒激光器的设计及实验结果,得到了脉冲能量为13J,重复频率为15Hz的激光输出。电光转换效率为2.2%,斜效率为3.4%。  相似文献   
159.
An yttria-stabilized zirconia powder, free of monoclinic phase, may be prepared by an oxalate method in an ethanol solution at strong acidity. This study demonstrates that the control of pH in the preparation of precursors has a significant effect on the ability of precursors to crystallize and hence plays an important role in determining the formation and fraction of various crystalline phases in the resulting yttria-stabilized zirconia powder. With the increase of pH, a precursor with a certain crystalline form may be transformed into an amorphous precursor, and a monoclinic phase appers in the phase composition of the resulting powder. The results of XRD analysis and Raman spectroscopy are discussed.  相似文献   
160.
水经磁场处理后,某些物理化学性质会发生变化。由于水对环境条件的影响极为敏感,准确地实验测定这些变化碰到了不少难以克服的困难。因此,文献上所报道的数据一致性较差。本工作采用比较法,对二次蒸馏水经过不同磁场强度处理后,其表面张力的变化进行了初步的实验研究和讨论。  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