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   264929篇
  免费   13255篇
  国内免费   6795篇
电工技术   9852篇
技术理论   9篇
综合类   11511篇
化学工业   41381篇
金属工艺   15630篇
机械仪表   13647篇
建筑科学   12490篇
矿业工程   4775篇
能源动力   4875篇
轻工业   13693篇
水利工程   4788篇
石油天然气   11073篇
武器工业   1138篇
无线电   27368篇
一般工业技术   46373篇
冶金工业   15354篇
原子能技术   5713篇
自动化技术   45309篇
  2023年   2361篇
  2022年   4814篇
  2021年   6523篇
  2020年   4930篇
  2019年   4292篇
  2018年   19426篇
  2017年   18923篇
  2016年   15195篇
  2015年   6675篇
  2014年   8010篇
  2013年   9741篇
  2012年   13200篇
  2011年   19999篇
  2010年   17259篇
  2009年   14443篇
  2008年   15492篇
  2007年   15997篇
  2006年   7842篇
  2005年   7741篇
  2004年   6225篇
  2003年   6270篇
  2002年   5859篇
  2001年   4956篇
  2000年   4208篇
  1999年   3543篇
  1998年   2792篇
  1997年   2358篇
  1996年   2148篇
  1995年   1858篇
  1994年   1582篇
  1993年   1373篇
  1992年   1357篇
  1991年   1248篇
  1990年   1244篇
  1989年   1211篇
  1988年   1091篇
  1987年   1021篇
  1986年   965篇
  1985年   919篇
  1984年   921篇
  1981年   875篇
  1979年   962篇
  1978年   1057篇
  1977年   1007篇
  1976年   1037篇
  1975年   989篇
  1974年   1049篇
  1973年   1037篇
  1972年   1002篇
  1971年   922篇
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
1.
2.
Specifications require that all the welds in 12-m-diam. decomposers with a capacity of 3600 m3 be subjected to high-temperature tempering before going into service in order to alleviate the stresses from the welding operation. Specialists at the organizations VNIIPTkhimnefteapparatury and VNIImontazhspetsstroi have proposed out-of-furnace volumetric (complete) of the assembled decomposer with the use of special heaters. The use of this heating method has shortened assembly operations while providing the welds with a highquality heat treatment and reducing the stresses overall (including welding stresses, stresses from assembly of the decomposer, etc.) The technology ensures uniform heating of the housing of the decomposer and provides for close control over the process. The experience gained in heat-treating decomposers can also be used in the construction of other containers that come into contact with corrosive media. __________ Translated from Metallurg, No. 3, pp. 61–64, March, 2006.  相似文献   
3.
The basic methods of verifying continuous automatic belt weighers are described. A comparative analysis of these methods on the basis of experimental studies is made and ways of implementing the results in industry are recommended.  相似文献   
4.
The effect of crystal orientation on the photogeneration of free charge carriers was studied for C60 single crystals in a weak magnetic field. The photoconductivity sharply depends on the orientation of magnetic field with respect to the crystallographic directions, showing a 5–8% increase for seven axes of the C60 crystal.  相似文献   
5.
Ferrite particles coated with biocompatible phases can be used for hyperthermia treatment of cancer. We have synthesized substituted calcium hexaferrite, which is not stable on its own but is stabilized with small substitution of La. Hexaferrite of chemical composition (CaO)0.75(La203)0.20(Fe2O3)6 was prepared using citrate gel method. Hydroxyapatite was prepared by precipitating it from aqueous solution of Ca(NO3)2 and (NH4)2HPO4 maintaining pH above 11. Four different methods were used for coating of hydroxyapatite on ferrite particles. SEM with EDX and X-ray diffraction analysis shows clear evidence of coating of hydroxyapatite on ferrite particles. These coated ferrite particles exhibited coercive field up to 2 kOe, which could be made useful for hysteresis heating in hyperthermia. Studies by culturing BHK-21 cells and WBC over the samples show evidence of biocompatibility. SEM micrographs and cell counts give clear indication of cell growth on the surface of the sample. Finally coated ferrite particle was implanted in Kasaulli mouse to test its biocompatibility. The magnetic properties and biocompatibility studies show that these hydroxyapatite coated ferrites could be useful for hyperthermia.  相似文献   
6.
Amphiphilic magnetic microspheres ranging in diameter from 5 to 100 µm were prepared by dispersion copolymerization of styrene and poly(ethylene oxide) vinylbenzyl (PEO‐VB) macromonomer (MPEO) in the presence of Fe3O4 magnetic fluid. The effects of various polymerization parameters on the average particle size were systematically investigated. The average particle size was found to increase with increasing styrene concentration and initiator concentration. It also increased with decreasing stabilizer concentration and molecular weight of MPEO. The content of the hydroxyl groups localized in the microspheres ranged from 0.01 to 0.2 mmol g?1. © 2003 Society of Chemical Industry  相似文献   
7.
Chloride doped polyaniline conducting polymer films have been prepared in a protic acid medium (HCl) by potentiodynamic method in an electrochemical cell and studied by cyclic voltammetry and FTIR techniques. The FTIR spectra confirmed Cl- ion doping in the polymers. The polymerization rate was found to increase with increasing concentration of aniline monomer. But the films obtained at high monomer concentration were rough having a nonuniform flaky polyaniline distribution. Results showed that the polymerization rate did not increase beyond a critical HCl concentration. Cyclic voltammetry suggested that, the oxidation-reduction current increased with an increase in scan rate and that the undoped polyaniline films were not hygroscopic whereas chloride doped polyaniline films were found to be highly hygroscopic.  相似文献   
8.
华风气象影视大楼总面积4万平方米,根据空间功能不同分为办公大楼和商务写字楼两部分,办公大楼是集演播室、制作机房、办公室为一体的九层综合性建筑。设计师杨宇在刚接触到这个项目的时候,面对的是一个既成事实的建筑。  相似文献   
9.
首次对茂金属聚丙烯(miPP)/齐格勒-纳塔聚丙烯(ziPP)共混体系的流动性进行了系统的研究。研究发现,在miPP/ziPP共混体系中,miPP含量的变化改变了共混体系的相结构,这种相结构会随着温度和剪切速率的变化而产生明显的变化,从而改变了体系的流动性能,且该共混体系在不同剪切速率下的流动曲线可以分别通过两个模型进行模拟。  相似文献   
10.
徐玉 《世界电信》2004,17(10):29-32
主要对各国3G许可证与使用技术标准的抽绑政策.各国对2G/3G网络漫游的管制规定。以及3G网络之间共享的种类及实施方式等方面做了详尽的讲解,并进行比较和分析。  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