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   433510篇
  免费   5056篇
  国内免费   1238篇
电工技术   7159篇
综合类   2498篇
化学工业   65014篇
金属工艺   21430篇
机械仪表   16372篇
建筑科学   10573篇
矿业工程   3054篇
能源动力   8787篇
轻工业   30788篇
水利工程   5196篇
石油天然气   8616篇
武器工业   17篇
无线电   45999篇
一般工业技术   88409篇
冶金工业   62181篇
原子能技术   8721篇
自动化技术   54990篇
  2021年   2313篇
  2019年   2204篇
  2018年   22794篇
  2017年   22302篇
  2016年   16281篇
  2015年   3679篇
  2014年   4936篇
  2013年   13384篇
  2012年   12056篇
  2011年   24383篇
  2010年   21240篇
  2009年   19375篇
  2008年   20393篇
  2007年   22663篇
  2006年   8711篇
  2005年   11905篇
  2004年   9919篇
  2003年   9416篇
  2002年   8152篇
  2001年   6980篇
  2000年   6779篇
  1999年   6650篇
  1998年   15264篇
  1997年   11450篇
  1996年   8980篇
  1995年   6902篇
  1994年   6244篇
  1993年   6166篇
  1992年   4806篇
  1991年   4700篇
  1990年   4552篇
  1989年   4562篇
  1988年   4513篇
  1987年   3847篇
  1986年   3865篇
  1985年   4442篇
  1984年   4249篇
  1983年   3894篇
  1982年   3647篇
  1981年   3796篇
  1980年   3658篇
  1979年   3606篇
  1978年   3649篇
  1977年   4131篇
  1976年   5239篇
  1975年   3334篇
  1974年   3169篇
  1973年   3192篇
  1972年   2756篇
  1971年   2560篇
排序方式: 共有10000条查询结果,搜索用时 390 毫秒
21.
Antimony triselenide (Sb2Se3) nanoflake-based nitrogen dioxide (NO2) sensors exhibit a progressive bifunctional gas-sensing performance, with a rapid alarm for hazardous highly concentrated gases, and an advanced memory-type function for low-concentration (<1 ppm) monitoring repeated under potentially fatal exposure. Rectangular and cuboid shaped Sb2Se3 nanoflakes, comprising van der Waals planes with large surface areas and covalent bond planes with small areas, can rapidly detect a wide range of NO2 gas concentrations from 0.1 to 100 ppm. These Sb2Se3 nanoflakes are found to be suitable for physisorption-based gas sensing owing to their anisotropic quasi-2D crystal structure with extremely enlarged van der Waals planes, where they are humidity-insensitive and consequently exhibit an extremely stable baseline current. The Sb2Se3 nanoflake sensor exhibits a room-temperature/low-voltage operation, which is noticeable owing to its low energy consumption and rapid response even under a NO2 gas flow of only 1 ppm. As a result, the Sb2Se3 nanoflake sensor is suitable for the development of a rapid alarm system. Furthermore, the persistent gas-sensing conductivity of the sensor with a slow decaying current can enable the development of a progressive memory-type sensor that retains the previous signal under irregular gas injection at low concentrations.  相似文献   
22.
Chemical and Petroleum Engineering - The processes of separation of impurities of particles of different sizes are analyzed under conditions of irregularity of structural and kinematic parameters...  相似文献   
23.
24.
25.
26.
27.
Theoretical Foundations of Chemical Engineering - New research results, as well as those published earlier by the authors, on the synthesis of azo compounds based on nitroanilines obtained by the...  相似文献   
28.
The bromodomain and extra terminal (BET) family of bromodomain-containing proteins (BCPs) have been the subject of extensive research over the past decade, resulting in a plethora of high-quality chemical probes for their tandem bromodomains. In turn, these chemical probes have helped reveal the profound biological role of the BET bromodomains and their role in disease, ultimately leading to a number of molecules in active clinical development. However, the BET subfamily represents just 8/61 of the known human bromodomains, and attention has now expanded to the biological role of the remaining 53 non-BET bromodomains. Rapid growth of this research area has been accompanied by a greater understanding of the requirements for an effective bromodomain chemical probe and has led to a number of new non-BET bromodomain chemical probes being developed. Advances since December 2015 are discussed, highlighting the strengths/caveats of each molecule, and the value they add toward validating the non-BET bromodomains as tractable therapeutic targets.  相似文献   
29.
Seed processing technologies are essential for seed safety and functionality through protection of physicochemical quality, pathogen inactivation, aflatoxin detoxification and alleviation of mutagenicity. Design of a pilot-scale unit of pulsed electric fields (PEF) to treat sesame seeds with respect to quality parameters, Aspergillus parasiticus inactivation and aflatoxin reduction as well as alleviation of aflatoxin mutagenicity were prompted in this study. PEF energy ranged from 0.97 to 17.28 J achieved maximum reductions of peroxide value and acidity number of 67.4 and 85.7%, respectively, and did not change color L*, a*, b* and hue values. A 60% reduction of A. parasiticus counts occurred at the maximum PEF energy. Aflatoxins G1, G2, B1, and B2 contents decreased by 94.7, 92.7, 86.9, and 98.7%, respectively. Except for the samples treated by 2.16 J with 100 μg/plate and by 6.80 J with 10 μg/plate, PEF treatment provided elimination of aflatoxin mutagenity. It is concluded that PEF treatment can be used to treat sesame seeds with preservation of physicochemical properties, inactivation of A. parasiticus and decomposition of aflatoxins with reduced mutagenicity.  相似文献   
30.
Theoretical Foundations of Chemical Engineering - The extraction of nitric and oxalic acids by neutral compounds TBP, DBBP, and TBPO have been studied. The optimal conditions of their separation...  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