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   304061篇
  免费   4194篇
  国内免费   704篇
电工技术   6101篇
综合类   555篇
化学工业   44011篇
金属工艺   10246篇
机械仪表   8710篇
建筑科学   7537篇
矿业工程   861篇
能源动力   8479篇
轻工业   30426篇
水利工程   2512篇
石油天然气   3627篇
武器工业   8篇
无线电   39472篇
一般工业技术   57812篇
冶金工业   56626篇
原子能技术   5458篇
自动化技术   26518篇
  2021年   2164篇
  2019年   2139篇
  2018年   3607篇
  2017年   3449篇
  2016年   3538篇
  2015年   2540篇
  2014年   4439篇
  2013年   14271篇
  2012年   7361篇
  2011年   10110篇
  2010年   7899篇
  2009年   9131篇
  2008年   9599篇
  2007年   9577篇
  2006年   8504篇
  2005年   7887篇
  2004年   7759篇
  2003年   7496篇
  2002年   7084篇
  2001年   7107篇
  2000年   6636篇
  1999年   7117篇
  1998年   17216篇
  1997年   12467篇
  1996年   9690篇
  1995年   7785篇
  1994年   7132篇
  1993年   6833篇
  1992年   5220篇
  1991年   4991篇
  1990年   4874篇
  1989年   4686篇
  1988年   4593篇
  1987年   3817篇
  1986年   3938篇
  1985年   4651篇
  1984年   4210篇
  1983年   3949篇
  1982年   3532篇
  1981年   3698篇
  1980年   3401篇
  1979年   3359篇
  1978年   3173篇
  1977年   3766篇
  1976年   4795篇
  1975年   2733篇
  1974年   2623篇
  1973年   2636篇
  1972年   2195篇
  1971年   1924篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
91.
Neutrophils readily infiltrate infection foci, phagocytose and usually destroy microbes. In tuberculosis (TB), a chronic pulmonary infection caused by Mycobacterium tuberculosis (Mtb), neutrophils harbor bacilli, are abundant in tissue lesions, and their abundances in blood correlate with poor disease outcomes in patients. The biology of these innate immune cells in TB is complex. Neutrophils have been assigned host-beneficial as well as deleterious roles. The short lifespan of neutrophils purified from blood poses challenges to cell biology studies, leaving intracellular biological processes and the precise consequences of Mtb–neutrophil interactions ill-defined. The phenotypic heterogeneity of neutrophils, and their propensity to engage in cellular cross-talk and to exert various functions during homeostasis and disease, have recently been reported, and such observations are newly emerging in TB. Here, we review the interactions of neutrophils with Mtb, including subcellular events and cell fate upon infection, and summarize the cross-talks between neutrophils and lung-residing and -recruited cells. We highlight the roles of neutrophils in TB pathophysiology, discussing recent findings from distinct models of pulmonary TB, and emphasize technical advances that could facilitate the discovery of novel neutrophil-related disease mechanisms and enrich our knowledge of TB pathogenesis.  相似文献   
92.
Agelaia-MPI and protonectin are antimicrobial peptides isolated from the wasp Parachartergus fraternus that show antimicrobial and neuroactive activities. Previously, two analogues of these peptides, neuroVAL and protonectin-F, were designed to reduce nonspecific toxicity and improve potency. Here, the three-dimensional structures of neuroVAL, protonectin and protonectin-F were determined by using circular dichroism and NMR spectroscopy. Antibacterial, antifungal, cytotoxic and hemolytic activities were tested for the parent peptides and analogues. All peptides showed moderate antimicrobial activity against Gram-positive bacteria, with agelaia-MPI being the most active. Protonectin and protonectin-F were found to be toxic to cancerous and noncancerous cell lines. Internalization experiments revealed that these peptides accumulate inside both cell types. By contrast, neuroVAL was nontoxic to all tested cells and was able to enter cells without accumulating. In summary, neuroVAL has potential as a nontoxic cell-penetrating peptide, while protonectin-F needs further modification to realize its potential as an antitumor peptide.  相似文献   
93.
Multidimensional Systems and Signal Processing - In medical Image processing, the chief objective is to detect Neoplasm effectively. Neoplasm is basically a sort of abnormal excessive cell growth...  相似文献   
94.
Russian Engineering Research - Practical approaches are described for introducing an energy management system at a high-tech enterprise so as to centralize and automate the regulation of energy...  相似文献   
95.
Enhanced gravity concentrators such as Knelson concentrator (KC) are extensively used in the mineral processing industry. The complexities of KC bowl geometry and variation of feed characteristics have forced process engineers to design empirically new units using laboratory and pilot-scale Knelson concentrators. However, numerical modelling methods such as computational fluid dynamics (CFD) and discrete element method (DEM) provide a better insight of flow behaviour of fluid and particulate solid phases inside these processing units. This article reports findings of CFD simulations for single-phase water flow inside the laboratory KC. An available standard 7.5-cm laboratory KC bowl was numerically simulated using realisable k-ε turbulence model to resolve the turbulence dispersion of existing transitional flow regime. The effects of relative centrifugal force (RCF) intensity and bed fluidisation water flow rate on the water velocity and pressure distributions were studied. Simulations confirmed the swirling flow pattern governing inside the bowl. The results revealed that the impact of RCF intensity on the water field values is greater than that of bed fluidisation water flow rate. Both velocity and pressure variations inside the bowl rings followed a linear trend.  相似文献   
96.
Kulikov  V. Yu.  Aubakirov  D. R.  Kvon  S. S.  Dostaeva  A. M.  Shcherbakova  E. P. 《Metallurgist》2019,62(9-10):1068-1072
Metallurgist - We provide an overview of requirements for wear-resistant materials in the Kazakhstani ore mining and smelting industry, and describe the basic variety of metallurgical parts and...  相似文献   
97.
Universal Access in the Information Society - Movement-based interaction has brought about new possibilities in healthcare environments. Concretely, rehabilitation therapies represent an adequate...  相似文献   
98.
Multidimensional Systems and Signal Processing - In general, the fusion of visible-light and infrared images produces a composite representation where both data are pictured in a single image. The...  相似文献   
99.
The synergistic interactions and corrosion protection properties of 2-amino 4-methyl benzothiazole, (AMBT) and 1, 2, 3-benzotriazole (BTZ) have been studied for mild steel in HCl at elevated temperatures. The extent of synergistic interaction increases with temperature. The methods of study include the conventional weight loss studies, computational screening, surface characterization and electrochemical studies. Quantum chemical approach was used to calculate some electronic properties of the molecules and to ascertain the synergistic interaction, inhibitive effect and molecular structures. The corrosion inhibition efficiencies and the global chemical reactivity relate to parameters like total energy, EHOMO, ELUMO and gap energy (ΔE). Condensed atom Fukui functions also calculated using DFT at B3LYP/6-31G* level, and were found to be correlating with the experimental results.  相似文献   
100.
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