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   516216篇
  免费   8084篇
  国内免费   1439篇
电工技术   9429篇
综合类   513篇
化学工业   74087篇
金属工艺   19791篇
机械仪表   14988篇
建筑科学   12243篇
矿业工程   2267篇
能源动力   14375篇
轻工业   46005篇
水利工程   5192篇
石油天然气   9267篇
武器工业   37篇
无线电   59622篇
一般工业技术   100660篇
冶金工业   103757篇
原子能技术   10562篇
自动化技术   42944篇
  2021年   4623篇
  2020年   3476篇
  2019年   4555篇
  2018年   7814篇
  2017年   7617篇
  2016年   7933篇
  2015年   5568篇
  2014年   9257篇
  2013年   24084篇
  2012年   14642篇
  2011年   20170篇
  2010年   15816篇
  2009年   17717篇
  2008年   18108篇
  2007年   17798篇
  2006年   15518篇
  2005年   14222篇
  2004年   13568篇
  2003年   13233篇
  2002年   11986篇
  2001年   12098篇
  2000年   10930篇
  1999年   11849篇
  1998年   32201篇
  1997年   22306篇
  1996年   16835篇
  1995年   12945篇
  1994年   11175篇
  1993年   10910篇
  1992年   7820篇
  1991年   7317篇
  1990年   7209篇
  1989年   6894篇
  1988年   6384篇
  1987年   5673篇
  1986年   5580篇
  1985年   6195篇
  1984年   5837篇
  1983年   5101篇
  1982年   4821篇
  1981年   4913篇
  1980年   4665篇
  1979年   4566篇
  1978年   4360篇
  1977年   5291篇
  1976年   6924篇
  1975年   3748篇
  1974年   3510篇
  1973年   3632篇
  1972年   2960篇
排序方式: 共有10000条查询结果,搜索用时 17 毫秒
61.
Journal of Inorganic and Organometallic Polymers and Materials - Zn1?xCdxO (x?=?0, 0.001, 0.01, 0.1) nanoparticles were prepared using polyol technique. The prepared nanoparticles...  相似文献   
62.
Chronic infection with Helicobacter pylori increases risk of gastric diseases including gastric cancer. Despite development of a robust immune response, H. pylori persists in the gastric niche. Progression of gastric inflammation to serious disease outcomes is associated with infection with H. pylori strains which encode the cag Type IV Secretion System (cag T4SS). The cag T4SS is responsible for translocating the oncogenic protein CagA into host cells and inducing pro-inflammatory and carcinogenic signaling cascades. Our previous work demonstrated that nutrient iron modulates the activity of the T4SS and biogenesis of T4SS pili. In response to H. pylori infection, the host produces a variety of antimicrobial molecules, including the iron-binding glycoprotein, lactoferrin. Our work shows that apo-lactoferrin exerts antimicrobial activity against H. pylori under iron-limited conditions, while holo-lactoferrin enhances bacterial growth. Culturing H. pylori in the presence of holo-lactoferrin prior to co-culture with gastric epithelial cells, results in repression of the cag T4SS activity. Concomitantly, a decrease in biogenesis of cag T4SS pili at the host-pathogen interface was observed under these culture conditions by high-resolution electron microscopy analyses. Taken together, these results indicate that acquisition of alternate sources of nutrient iron plays a role in regulating the pro-inflammatory activity of a bacterial secretion system and present novel therapeutic targets for the treatment of H. pylori-related disease.  相似文献   
63.
Cell surface and secreted proteins provide essential functions for multicellular life. They enter the endoplasmic reticulum (ER) lumen co-translationally, where they mature and fold into their complex three-dimensional structures. The ER is populated with a host of molecular chaperones, associated co-factors, and enzymes that assist and stabilize folded states. Together, they ensure that nascent proteins mature properly or, if this process fails, target them for degradation. BiP, the ER HSP70 chaperone, interacts with unfolded client proteins in a nucleotide-dependent manner, which is tightly regulated by eight DnaJ-type proteins and two nucleotide exchange factors (NEFs), SIL1 and GRP170. Loss of SIL1′s function is the leading cause of Marinesco-Sjögren syndrome (MSS), an autosomal recessive, multisystem disorder. The development of animal models has provided insights into SIL1′s functions and MSS-associated pathologies. This review provides an in-depth update on the current understanding of the molecular mechanisms underlying SIL1′s NEF activity and its role in maintaining ER homeostasis and normal physiology. A precise understanding of the underlying molecular mechanisms associated with the loss of SIL1 may allow for the development of new pharmacological approaches to treat MSS.  相似文献   
64.
Journal of Inorganic and Organometallic Polymers and Materials - In this work, a borosilicate glass sample (5SiO2–45B2O3–20Na2O–25CaO–5Ag2O) was added to nano-sized...  相似文献   
65.
Refractories and Industrial Ceramics - The paper introduces a promising technology for utilizing a traditional scheme for implementing a flow-through micro-arc oxidation method to restore localized...  相似文献   
66.
Sakthivelu  S.  Sethusundaram  P. P.  Ravichandran  M.  Meignanamoorthy  M. 《SILICON》2021,13(4):1285-1294
Silicon - Aluminium alloy finds widespread applications in numerous engineering industries because of its tremendous properties. However aluminium alloy possess poor wear resistance. This study...  相似文献   
67.
Mesoscale order can lead to emergent properties including phononic bandgaps or topologically protected states. Block copolymers offer a route to mesoscale periodic architectures, but their use as structure directing agents for metallic materials has not been fully realized. A versatile approach to mesostructured metals via bulk block copolymer self-assembly derived ceramic templates, is demonstrated. Molten indium is infiltrated into mesoporous, double gyroidal silicon nitride templates under high pressure to yield bulk, 3D periodic nanocomposites as free-standing monoliths which exhibit emergent quantum-scale phenomena. Vortices are artificially introduced when double gyroidal indium metal behaves as a type II superconductor, with evidence of strong pinning centers arrayed on the order of the double gyroid lattice size. Sample behavior is reproducible over months, showing high stability. High pressure infiltration of bulk block copolymer self-assembly based ceramic templates is an enabling tool for studying high-quality metals with previously inaccessible architectures, and paves the way for the emerging field of block-copolymer derived quantum metamaterials.  相似文献   
68.
Wireless Personal Communications - A GPS spoofing attack broadcasts counterfeit signals to resemble standard GPS satellite signals to take control of the correlation peaks of GPS signals to force...  相似文献   
69.
Present assembly systems are often based on rigid, line-based approaches and are hindered in their reconfiguration capability. Line-less Mobile Assembly Systems (LMAS) are a novel approach for assembly organization. They improve flexibility through mobile resources, permitting spatiotemporal freedom in scheduling and resource assignment. This paper presents a method for a priori assessment of LMAS during the early stages of the assembly system design process. The method applies a modified, extended mean value analysis to a closed queuing network representation of LMAS to estimate performance. The method is validated model analysis and comparison on two use cases indicating plausible model behavior.  相似文献   
70.
In the present study we made an effort to deploy eco-friendly synthesized reduced graphene oxide/Lanthanum Alluminate nanocomposites (RGO-LaAlO3) and Lanthanum Alluminate (LaAlO3) as adsorbents to remove dye from the synthetic media. XRD, SEM, BET surface area and EDX have been used to characterize the above-mentioned adsorbents. The impacts of different factors like adsorbent dosage, the concentration of adsorbate and PH on adsorption were studied. The best fit linear and nonlinear equations for the adsorption isotherms and kinetic models had been examined. The sum of the normalized errors and the coefficient of determination were used to determine the best fit model. The experimental data were more aptly fitted for nonlinear forms of isotherms and kinetic equations. Pseudo-second-order and Freundlich isotherm model fits the equilibrium data satisfactorily. Methyl orange (MO) has been used as model dye pollutant and maximum adsorption capacity was found to be 469.7 and 702.2 mg g?1 for LaAlO3 and RGO-LaAlO3, respectively.  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