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   861215篇
  免费   10890篇
  国内免费   2096篇
电工技术   15914篇
综合类   759篇
化学工业   130512篇
金属工艺   36876篇
机械仪表   28273篇
建筑科学   19262篇
矿业工程   5673篇
能源动力   22748篇
轻工业   65188篇
水利工程   10019篇
石油天然气   18479篇
武器工业   46篇
无线电   95965篇
一般工业技术   176148篇
冶金工业   152060篇
原子能技术   19345篇
自动化技术   76934篇
  2021年   7653篇
  2020年   5776篇
  2019年   7366篇
  2018年   16022篇
  2017年   16168篇
  2016年   15554篇
  2015年   8753篇
  2014年   14370篇
  2013年   39230篇
  2012年   23629篇
  2011年   34210篇
  2010年   27968篇
  2009年   30328篇
  2008年   31090篇
  2007年   31599篇
  2006年   24268篇
  2005年   23367篇
  2004年   21793篇
  2003年   21492篇
  2002年   20033篇
  2001年   19315篇
  2000年   18391篇
  1999年   18583篇
  1998年   45426篇
  1997年   32212篇
  1996年   25013篇
  1995年   18912篇
  1994年   16929篇
  1993年   16721篇
  1992年   12506篇
  1991年   11913篇
  1990年   11757篇
  1989年   11343篇
  1988年   10785篇
  1987年   9731篇
  1986年   9370篇
  1985年   10697篇
  1984年   9732篇
  1983年   9099篇
  1982年   8276篇
  1981年   8445篇
  1980年   7885篇
  1979年   7955篇
  1978年   7792篇
  1977年   8792篇
  1976年   11174篇
  1975年   6899篇
  1974年   6620篇
  1973年   6725篇
  1972年   5684篇
排序方式: 共有10000条查询结果,搜索用时 187 毫秒
201.
202.
The paper describes the results of a study on the temperature and frequency dependences of the dielectric permeability and dielectric loss tangent of composite materials composed of low density polyethylene filled with cadmium sulfide (LDPE/CdS) and indium(III) selenide (LDPE/In2Se3) in the temperature range of 300–450 K and a frequency range of 0–1014 Hz. It is revealed that a variation in the filler content and the effect of external factors can yield novel composite materials with desired dielectric characteristics.  相似文献   
203.
204.
205.
206.
Currently, the extracellular matrix (ECM) is considered a pivotal complex meshwork of macromolecules playing a plethora of biomolecular functions in health and disease beyond its commonly known mechanical role. Only by unraveling its composition can we leverage related tissue engineering and pharmacological efforts. Nevertheless, its unbiased proteomic identification still encounters some limitations mainly due to partial ECM enrichment by precipitation, sequential fractionation using unfriendly-mass spectrometry (MS) detergents, and resuspension with harsh reagents that need to be entirely removed prior to analysis. These methods can be technically challenging and labor-intensive, which affects the reproducibility of ECM identification and induces protein loss. Here, we present a simple new method applicable to tissue fragments of 10 mg and more. The technique has been validated on human ovarian tissue and involves a standardized procedure for sample processing with an MS-compatible detergent and combined centrifugation. This two-step protocol eliminates the need for laborious sample clarification and divides our samples into 2 fractions, soluble and insoluble, successively enriched with matrisome-associated (ECM-interacting) and core matrisome (structural ECM) proteins.  相似文献   
207.
In eukaryotes, microRNAs (miRNAs) have roles in development, homeostasis, disease and the immune response. Recent work has shown that plant and mammalian miRNAs also mediate cross-kingdom and cross-domain communications. However, these studies remain controversial and are lacking critical mechanistic explanations. Bacteria do not produce miRNAs themselves, and therefore it is unclear how these eukaryotic RNA molecules could function in the bacterial recipient. In this review, we compare and contrast the biogenesis and functions of regulatory RNAs in eukaryotes and bacteria. As a result, we discovered several conserved features and homologous components in these distinct pathways. These findings enabled us to propose novel mechanisms to explain how eukaryotic miRNAs could function in bacteria. Further understanding in this area is necessary to validate the findings of existing studies and could facilitate the use of miRNAs as novel tools for the directed remodelling of the human microbiota.  相似文献   
208.
JOM - Alpha-radiation damage in metals is a concern for long-term radioactive storage and systems that produce nuclear energy. Accurate prediction of irradiated material properties and failure...  相似文献   
209.
210.
Powder Metallurgy and Metal Ceramics - The theoretical strength of LaB6 and MeB2 borides and a eutectic LaB6–TiB2 system is calculated with quasiharmonic approximation for uniaxial strain in...  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