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   172375篇
  免费   1835篇
  国内免费   189篇
电工技术   2566篇
综合类   120篇
化学工业   26907篇
金属工艺   9540篇
机械仪表   5797篇
建筑科学   3206篇
矿业工程   1905篇
能源动力   2819篇
轻工业   10162篇
水利工程   2788篇
石油天然气   8723篇
武器工业   12篇
无线电   14714篇
一般工业技术   39279篇
冶金工业   27871篇
原子能技术   6954篇
自动化技术   11036篇
  2019年   1751篇
  2018年   3272篇
  2017年   3402篇
  2016年   3627篇
  2015年   1879篇
  2014年   3225篇
  2013年   6948篇
  2012年   4686篇
  2011年   5792篇
  2010年   4742篇
  2009年   5199篇
  2008年   5263篇
  2007年   5178篇
  2006年   4391篇
  2005年   3951篇
  2004年   3750篇
  2003年   3641篇
  2002年   3454篇
  2001年   3428篇
  2000年   3266篇
  1999年   3144篇
  1998年   6949篇
  1997年   5090篇
  1996年   3740篇
  1995年   2948篇
  1994年   2615篇
  1993年   2723篇
  1992年   2258篇
  1991年   2307篇
  1990年   2415篇
  1989年   2314篇
  1988年   2316篇
  1987年   2174篇
  1986年   2244篇
  1985年   2296篇
  1984年   2218篇
  1983年   2138篇
  1982年   1974篇
  1981年   2187篇
  1980年   2057篇
  1979年   2255篇
  1978年   2428篇
  1977年   2423篇
  1976年   3086篇
  1975年   2242篇
  1974年   2298篇
  1973年   2337篇
  1972年   2152篇
  1971年   1904篇
  1970年   1694篇
排序方式: 共有10000条查询结果,搜索用时 93 毫秒
1.
Atomic Energy - The physical aspects and main results of reactor tests of a two-stage core consisting of fresh fuel assemblies and a significant number of fuel assemblies from the previous core,...  相似文献   
2.
Journal of Communications Technology and Electronics - An option of multicriteria collision risk ranking of aircraft by data from an onboard radar station (OBRS) is proposed. This method can be...  相似文献   
3.
Protection of Metals and Physical Chemistry of Surfaces - Impedance spectroscopy was used to study the adsorption of the IFKhAN-92 inhibitor, a triazole derivative, on cathodically polarized...  相似文献   
4.
Amides from indole-3-glyoxylic acid and 4-benzoyl-2-methylpiperazine, which are related to entry inhibitors developed by Bristol-Myers Squibb (BMS), have been synthesized with aliphatic chains located at the C7 position of the indole ring. These spacers contain an azido group suitable for the well-known Cu(I)-catalyzed (3+2)-cycloaddition or an activated triple bond for the nucleophilic addition of thiols under physiological conditions. Reaction with polyols (β-cyclodextrin and hyperbranched polyglycerol) decorated with complementary click partners has afforded polyol-BMS-like conjugates that are not cytotoxic (TZM.bl cells) and retain the activity against R5-HIV-1NLAD8 isolates. Thus, potential vaginal microbicides based on entry inhibitors, which can be called of 4th generation, are reported here for the first time.  相似文献   
5.
Combustion, Explosion, and Shock Waves - This paper touches upon the effect of a polyvinyl butyral content (0–2.3%) on the combustion of a Ti + C granular...  相似文献   
6.
Chronic stress is a combination of nonspecific adaptive reactions of the body to the influence of various adverse stress factors which disrupt its homeostasis, and it is also a corresponding state of the organism’s nervous system (or the body in general). We hypothesized that chronic stress may be one of the causes occurence of several molecular and cellular types of stress. We analyzed literary sources and considered most of these types of stress in our review article. We examined genes and mutations of nuclear and mitochondrial genomes and also molecular variants which lead to various types of stress. The end result of chronic stress can be metabolic disturbance in humans and animals, leading to accumulation of reactive oxygen species (ROS), oxidative stress, energy deficiency in cells (due to a decrease in ATP synthesis) and mitochondrial dysfunction. These changes can last for the lifetime and lead to severe pathologies, including neurodegenerative diseases and atherosclerosis. The analysis of literature allowed us to conclude that under the influence of chronic stress, metabolism in the human body can be disrupted, mutations of the mitochondrial and nuclear genome and dysfunction of cells and their compartments can occur. As a result of these processes, oxidative, genotoxic, and cellular stress can occur. Therefore, chronic stress can be one of the causes forthe occurrence and development of neurodegenerative diseases and atherosclerosis. In particular, chronic stress can play a large role in the occurrence and development of oxidative, genotoxic, and cellular types of stress.  相似文献   
7.
In the current study two different batches of X7R-0603 BME-MLCCs displayed dissimilar electrical performance, despite having the same chemical composition, tape casting, and sintering conditions; with the only difference between them being the ore deposits where the raw materials were extracted from to synthesize the BaTiO3. Specifically, they presented different electrical response to highly accelerated life tests (HALT). Although the chemical analysis of each slip showed the same composition, the trace elements of the BaTiO3 sources could have acted as dopants or produced different secondary phases. A search for precipitates in the two samples was conducted by means of Scanning (SEM) and Transmission Electron Microscopy (TEM) techniques. SEM observations confirmed the presence of precipitates formed within the structure of the MLCCs exhibiting the greatest decrement in their electrical resistance results during the HALT. In order to further characterize the observed precipitates, samples were prepared by Focused Ion Beam (FIB) lift-out method, to make TEM characterization of specific precipitates feasible. TEM studies were performed on the precipitates to obtain electron diffraction patterns and complementary Energy Dispersive X-Ray Spectroscopy (EDXS) chemical analysis. Based on the crystal and chemical data obtained, it can be concluded that the precipitates are a hexagonal anhydrous silicate oxyapatite phase with a stoichiometry of Ca3Y16Si10O13, and lattice parameters of a = 0.9353 nm and c = 0.6970 nm; this phase was not found in the JCPDS data base. Differences in raw materials coming from different ore deposits can produce undesired precipitates that affect the electrical performance of MLCCs.  相似文献   
8.
Journal of Chemical Ecology - Entomopathogenic fungi (EPF) can be experimentally established in several plant species as endophytes. Ecological effects of EPF inoculations on plant growth and...  相似文献   
9.
Refractories and Industrial Ceramics - Technology for producing alumina-periclase-carbon refractories of the brands APUK-D and APU-D is developed and implemented. Use of complex antioxidant and...  相似文献   
10.
Kirovskaya  I. A.  Filatova  T. N.  Nor  P. E. 《Semiconductors》2021,55(2):228-233
Semiconductors - According to developed methods, in the fields of the mutual solubility of initial binary compounds (InP, InSb, and CdS), solid solutions of the InP–CdS and InSb–CdS...  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