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   1732469篇
  免费   40502篇
  国内免费   14222篇
电工技术   44286篇
技术理论   12篇
综合类   17687篇
化学工业   297418篇
金属工艺   75053篇
机械仪表   55957篇
建筑科学   59041篇
矿业工程   16591篇
能源动力   54559篇
轻工业   132322篇
水利工程   19070篇
石油天然气   47356篇
武器工业   1538篇
无线电   214340篇
一般工业技术   313666篇
冶金工业   210725篇
原子能技术   36003篇
自动化技术   191569篇
  2021年   21385篇
  2020年   16317篇
  2019年   18278篇
  2018年   21843篇
  2017年   21828篇
  2016年   26560篇
  2015年   23551篇
  2014年   36126篇
  2013年   96820篇
  2012年   47668篇
  2011年   62233篇
  2010年   54100篇
  2009年   61752篇
  2008年   56877篇
  2007年   54407篇
  2006年   55195篇
  2005年   49123篇
  2004年   48284篇
  2003年   47409篇
  2002年   45833篇
  2001年   42698篇
  2000年   40553篇
  1999年   40253篇
  1998年   60451篇
  1997年   48903篇
  1996年   42438篇
  1995年   35394篇
  1994年   32629篇
  1993年   31892篇
  1992年   27671篇
  1991年   24667篇
  1990年   24838篇
  1989年   23878篇
  1988年   22398篇
  1987年   20418篇
  1986年   19862篇
  1985年   23157篇
  1984年   22893篇
  1983年   20832篇
  1982年   19611篇
  1981年   19774篇
  1980年   18370篇
  1979年   18842篇
  1978年   18008篇
  1977年   18434篇
  1976年   20449篇
  1975年   16221篇
  1974年   15715篇
  1973年   15832篇
  1972年   13264篇
排序方式: 共有10000条查询结果,搜索用时 296 毫秒
101.
Fluorescent fusion proteins are powerful tools for studying biological processes in living cells, but universal application is limited due to the voluminous size of those tags, which might have an impact on the folding, localization or even the biological function of the target protein. The designed biocatalyst trypsiligase enables site-directed linkage of small-sized fluorescence dyes on the N terminus of integral target proteins located in the outer membrane of living cells through a stable native peptide bond. The function of the approach was tested by using the examples of covalent derivatization of the transmembrane proteins CD147 as well as the EGF receptor, both presented on human HeLa cells. Specific trypsiligase recognition of the site of linkage was mediated by the dipeptide sequence Arg-His added to the proteins’ native N termini, pointing outside the cell membrane. The labeling procedure takes only about 5 minutes, as demonstrated for couplings of the fluorescence dye tetramethyl rhodamine and the affinity label biotin as well.  相似文献   
102.
Journal of Communications Technology and Electronics - Abstract—The matrix coefficients of projection models of strip lines obtained using the Chebyshev basis are presented as a sum of...  相似文献   
103.
Analog Integrated Circuits and Signal Processing - This paper presents the complete design of a phase locked loop-based clock synthesizer for reconfigurable analog-to-digital converters. The...  相似文献   
104.
Catalysis Letters - An environmentally benign process for synthesizing 4-methoxyphenol through methylation of hydroquinone using polystyrene immobilized Bronsted acidic ionic liquid is presented....  相似文献   
105.
106.
安俊理 《机械管理开发》2021,36(4):140-141,161
以寺河矿南区回风大巷为工程背景,在分析巷道地质条件的基础上,通过理论计算分析了锚杆及锚索的主要支护参数,并确定了锚杆及锚索的型号;结合以往的生产实践经验,确定了巷道联合支护方案.实践表明,巷道支护方案合理,可以满足安全生产要求.  相似文献   
107.
Calmodulin (CaM) is an important intracellular protein that binds Ca2+ and functions as a critical second messenger involved in numerous biological activities through extensive interactions with proteins and peptides. CaM’s ability to adapt to binding targets with different structures is related to the flexible central helix separating the N- and C-terminal lobes, which allows for conformational changes between extended and collapsed forms of the protein. CaM-binding targets are most often identified using prediction algorithms that utilize sequence and structural data to predict regions of peptides and proteins that can interact with CaM. In this review, we provide an overview of different CaM-binding proteins, the motifs through which they interact with CaM, and shared properties that make them good binding partners for CaM. Additionally, we discuss the historical and current methods for predicting CaM binding, and the similarities and differences between these methods and their relative success at prediction. As new CaM-binding proteins are identified and classified, we will gain a broader understanding of the biological processes regulated through changes in Ca2+ concentration through interactions with CaM.  相似文献   
108.
Grass pea (Lathyrus sativus) is a leguminous plant of outstanding tolerance to abiotic stress. The aim of the presented study was to describe the mechanism of grass pea (Lathyrus sativus L.) photosynthetic apparatus acclimatisation strategies to salinity stress. The seedlings were cultivated in a hydroponic system in media containing various concentrations of NaCl (0, 50, and 100 mM), imitating none, moderate, and severe salinity, respectively, for three weeks. In order to characterise the function and structure of the photosynthetic apparatus, Chl a fluorescence, gas exchange measurements, proteome analysis, and Fourier-transform infrared spectroscopy (FT-IR) analysis were done inter alia. Significant differences in the response of the leaf and stem photosynthetic apparatus to severe salt stress were observed. Leaves became the place of harmful ion (Na+) accumulation, and the efficiency of their carboxylation decreased sharply. In turn, in stems, the reconstruction of the photosynthetic apparatus (antenna and photosystem complexes) activated alternative electron transport pathways, leading to effective ATP synthesis, which is required for the efficient translocation of Na+ to leaves. These changes enabled efficient stem carboxylation and made them the main source of assimilates. The observed changes indicate the high plasticity of grass pea photosynthetic apparatus, providing an effective mechanism of tolerance to salinity stress.  相似文献   
109.
110.
With liquefied natural gas becoming increasingly prevalent as a flexible source of energy, the design and optimization of industrial refrigeration cycles becomes even more important. In this article, we propose an integrated surrogate modeling and optimization framework to model and optimize the complex CryoMan Cascade refrigeration cycle. Dimensionality reduction techniques are used to reduce the large number of process decision variables which are subsequently supplied to an array of Gaussian processes, modeling both the process objective as well as feasibility constraints. Through iterative resampling of the rigorous model, this data-driven surrogate is continually refined and subsequently optimized. This approach was not only able to improve on the results of directly optimizing the process flow sheet but also located the set of optimal operating conditions in only 2 h as opposed to the original 3 weeks, facilitating its use in the operational optimization and enhanced process design of large-scale industrial chemical systems.  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