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   17043篇
  免费   1095篇
  国内免费   520篇
电工技术   812篇
技术理论   1篇
综合类   655篇
化学工业   2885篇
金属工艺   857篇
机械仪表   836篇
建筑科学   1141篇
矿业工程   384篇
能源动力   540篇
轻工业   1101篇
水利工程   352篇
石油天然气   718篇
武器工业   147篇
无线电   1933篇
一般工业技术   2868篇
冶金工业   1374篇
原子能技术   257篇
自动化技术   1797篇
  2024年   57篇
  2023年   181篇
  2022年   388篇
  2021年   534篇
  2020年   407篇
  2019年   339篇
  2018年   442篇
  2017年   460篇
  2016年   419篇
  2015年   509篇
  2014年   627篇
  2013年   1017篇
  2012年   869篇
  2011年   994篇
  2010年   815篇
  2009年   806篇
  2008年   795篇
  2007年   744篇
  2006年   696篇
  2005年   664篇
  2004年   481篇
  2003年   458篇
  2002年   432篇
  2001年   385篇
  2000年   457篇
  1999年   460篇
  1998年   465篇
  1997年   409篇
  1996年   347篇
  1995年   292篇
  1994年   259篇
  1993年   227篇
  1992年   173篇
  1991年   186篇
  1990年   118篇
  1989年   120篇
  1988年   125篇
  1987年   117篇
  1986年   94篇
  1985年   132篇
  1984年   124篇
  1983年   134篇
  1982年   96篇
  1981年   96篇
  1980年   86篇
  1979年   89篇
  1978年   75篇
  1977年   66篇
  1976年   72篇
  1975年   57篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
A simple decoding procedure for algebraic-geometric codes C Ω(D,G) is presented. This decoding procedure is a generalization of Peterson's decoding procedure for the BCH codes. It can be used to correct any [(d*-1)/2] or fewer errors with complexity O(n3), where d * is the designed minimum distance of the algebraic-geometric code and n is the codelength  相似文献   
72.
PZT铁电薄膜的制备及电学性能研究   总被引:6,自引:1,他引:5  
使用硝酸锆作锆源的溶胶-凝胶方法制备PZT铁电薄膜。他们的电学性能被测试包括电滞回线,电流I(t)特性,漏电流,矫顽场疲劳和老化。测到的PZT薄膜剩余极化8.2μC/cm~2,矫顽场68kV/cm.簿膜的寿命可超过10~(11)周期。  相似文献   
73.
74.
High-T c Bi(Pb)-Sr-Ca-Cu-O thin films have been made on single-crystal MgO substrates using high-pressure dc sputtering technique. X-ray studies confirm the crystallinity and highly oriented structure withc-axis perpendicular to the substrate. By optimizing the annealing schedule the formation of the high-T c phase is stabilized. The best film exhibited superconducting transition temperature with zero-resistance temperature,T c(0), as high as 101 K. Temperature dependence ofJ c indicates the presence of Josephson-type weak links.  相似文献   
75.
K S Rao  P S Moharir 《Sadhana》1996,21(6):775-780
An algorithm called a Hamming scan was developed recently for obtaining sequences with large merit factors and is adopted here to obtain such sequences within which there are nontrivial segments of large merit factors. Correlative detection of the return signal can be based simultaneously on the entire sequence and its segments with large merit factors. Such a coincidence detection scheme can be characterized by a Schur merit factor of the sequence. Sequences with large Schur merit factors are listed.  相似文献   
76.
The Jade file system, which provides a uniform way to name and access files in an Internet environment, is introduced. Jade is a logical system that integrates a heterogeneous collection of existing file systems in which underlying file systems support different file access protocols. Because of autonomy, Jade is designed under the restriction that the underlying file systems may not be modified. In order to avoid the complexity of maintaining an Internet-wide, global name space, Jade permits each user to define a private name space. Jade's name space supports two features: it allows multiple file systems to be mounted under one directory, and it permits one logical name space to mount other logical name spaces. A prototype of Jade has been implemented to examine and validate its design. The prototype consists of interfaces to the Unix File System, the Sun Network File System, and the File Transfer Protocol. An overview of Jade's design is reported, and the authors' experiences in designing and implementing a large scale file system are reviewed  相似文献   
77.
In this report, the role of 34 kDa HA-binding protein in hyaluronic acid-induced cellular signalling in lymphocytes has been examined. The binding of 125I-HA to lymphocytes in vivo was found to be inhibited by pre-incubation of the cells with anti-34 kDa HA-binding protein antibodies, thus confirming 34 kDa HA-binding protein as the specific HA-receptor in lymphocytes. This observation was substantiated by anti-34 kDa HA-binding protein antibodies immunoblotting and 125I-HA ligand blotting of lymphocytes cell lysate. The HA-induced cell aggregation, tyrosine phosphorylation and cytoskeletal protein phosphorylation demonstrate the HA-induced early cellular signalling events in lymphocytes. Further, to study the involvement of 34 kDa HA-binding protein in mitogen induced lymphocyte signalling, we studied in vivo phosphorylation and secondary messenger formation. The enhanced 34 kDa HA-binding protein phosphorylation by HA and the inhibition of cellular aggregation and IP3 formation by anti-HA-binding protein antibodies revealed that 34 kDa HA-binding protein is one of the potential mediators in HA-induced signal transduction.  相似文献   
78.
天然竹芋淀粉及其接枝共聚   总被引:1,自引:0,他引:1  
分析了竹芋淀粉的伴生物组成,粒径分布及直链淀粉的含量,研究了竹芋淀粉与甲基丙烯酸甲酯的接枝共聚,用偏光显微镜,X射线衍射等方法研究了淀粉接枝共聚反应前后的结构与形态,认为淀粉的结晶区和非晶区均为接权共聚反应的场所。  相似文献   
79.
SynthesisandCrystalStructureofRE[CH2(CH2)4CONC4H9]3(NO3)3(RE=Dy,La)WangHanzhang(王汉章),XuQingfeng(徐庆锋),QianPu(钱朴)SunJianping(孙建...  相似文献   
80.
The pressure variations during polymer flooding of oil reservoirs for oil recovery projects can be used to analyze the flow in the reservoir which is especially useful for the partially perforated reservoirs. This paper presents a relationship between the viscosity and the shear rate which is similar to forms developed for radial flow (Odeh, A. S., Yang, H. T. ([1979]). SPEJ. AIME (Jun.) 155). The power-law viscosity model is used to give the variation of the fluid viscosity with the spherical radius for a mathematical model of unsteady spherical flow for non-Newtonian fluids with wellbore storage and skin. An analytical solution for the wellbore pressure responses derived in Laplace space is used to analyze the behavior characteristics at early and later times to interpret the well-test parameters. The pressure variations are similar to those for a Newtonian fluid at the early times, but at later times, the variation of the viscosity with the power-law exponent is important, so the pressure response differs from that for a Newtonian fluid. The solution has significance for interpreting well test parameters for non-Newtonian spherical flow.  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