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   256035篇
  免费   3622篇
  国内免费   812篇
电工技术   5082篇
综合类   326篇
化学工业   35325篇
金属工艺   10201篇
机械仪表   8373篇
建筑科学   5910篇
矿业工程   1074篇
能源动力   6343篇
轻工业   22442篇
水利工程   2537篇
石油天然气   3877篇
武器工业   68篇
无线电   34599篇
一般工业技术   49554篇
冶金工业   46519篇
原子能技术   5418篇
自动化技术   22821篇
  2021年   1969篇
  2019年   2033篇
  2018年   3467篇
  2017年   3532篇
  2016年   3727篇
  2015年   2319篇
  2014年   4046篇
  2013年   11283篇
  2012年   6561篇
  2011年   8872篇
  2010年   6979篇
  2009年   7848篇
  2008年   8676篇
  2007年   8613篇
  2006年   7802篇
  2005年   7139篇
  2004年   6885篇
  2003年   6731篇
  2002年   6339篇
  2001年   6099篇
  2000年   5710篇
  1999年   5877篇
  1998年   13957篇
  1997年   9997篇
  1996年   7796篇
  1995年   6355篇
  1994年   5660篇
  1993年   5533篇
  1992年   4496篇
  1991年   4159篇
  1990年   4018篇
  1989年   3732篇
  1988年   3580篇
  1987年   3133篇
  1986年   3031篇
  1985年   3567篇
  1984年   3343篇
  1983年   2983篇
  1982年   2812篇
  1981年   2910篇
  1980年   2731篇
  1979年   2623篇
  1978年   2476篇
  1977年   2911篇
  1976年   3520篇
  1975年   2299篇
  1974年   2297篇
  1973年   2286篇
  1972年   1841篇
  1971年   1720篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Virtual Reality - Do apparatuses and eyestrain have effects on learning performances and quality of experience? Materials and Methods: 42 participants played a serious game simulating a job...  相似文献   
22.
Fine-tuning of the scaffolds structural features for bone tissue engineering can be an efficient approach to regulate the specific response of the osteoblasts. Here, we loaded magnetic nanoparticles aka superparamagnetic iron oxide nanoparticles (SPIONs) into 3D composite scaffolds based on biological macromolecules (chitosan, collagen, hyaluronic acid) and calcium phosphates for potential applications in bone regeneration, using a biomimetic approach. We assessed the effects of organic (chitosan/collagen/hyaluronic acid) and inorganic (calcium phosphates, SPIONs) phase over the final features of the magnetic scaffolds (MS). Mechanical properties, magnetic susceptibility and biological fluids retention are strongly dependent on the final composition of MS and within the recommended range for application in bone regeneration. The MS architecture/pore size can be made bespoken through changes of the final organic/inorganic ratio. The scaffolds undertake mild degradation as the presence of inorganic components hinders the enzyme catalytic activity. In vitro studies indicated that osteoblasts (SaOS-2) on MS9 had similar cell behaviour activity in comparison with the TCP control. In vivo data showed an evident development of integration and resorption of the MS composites with low inflammation activity. Current findings suggest that the combination of SPIONs into 3D composite scaffolds can be a promising toolkit for bone regeneration.  相似文献   
23.
Theoretical Foundations of Chemical Engineering - The results of numerical modeling of the heat and mass transfer of drops during drying of a liquid under the conditions of...  相似文献   
24.
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   
25.
Volkovich  A. G.  Kolyadin  V. I.  Lemus  A. V.  Pavlenko  V. I.  Potapov  V. N.  Semenov  S. G.  Simirskii  Yu. N.  Chesnokov  A. V.  Shisha  A. D. 《Atomic Energy》2021,129(6):349-355
Atomic Energy - The results of the dismantling of the active drain system and the decontamination of technological enclosures of the loop installations of the MR reactor, which is being...  相似文献   
26.
Free fatty acid receptor 2 (FFA2) is a sensor for short-chain fatty acids that has been identified as an interesting potential drug target for treatment of metabolic and inflammatory diseases. Although several ligand series are known for the receptor, there is still a need for improved compounds. One of the most potent and frequently used antagonists is the amide-substituted phenylbutanoic acid known as CATPB ( 1 ). We here report the structure-activity relationship exploration of this compound, leading to the identification of homologues with increased potency. The preferred compound 37 (TUG-1958) was found, besides improved potency, to have high solubility and favorable pharmacokinetic properties.  相似文献   
27.
Automation and Remote Control - We consider the NP-hard integer three-index axial assignment problem. The task of optimal combination of the pairs of feasible solutions of the problem is posed, and...  相似文献   
28.
Theoretical Foundations of Chemical Engineering - The paper focuses on synthesis of bioactive glass with tailored properties achieved by doping it with oxides of different elements. The bioglass...  相似文献   
29.
The conventional S-alkylation of cysteine relies upon using activated electrophiles. Here we demonstrate high-yielding and selective S-alkylation and S-lipidation of cysteines in unprotected synthetic peptides and proteins by using weak electrophiles and a Zn2+ promoter. Linear or branched iodoalkanes can S-alkylate cysteine in an unprotected 38-residue Myc peptide fragment and in a 91-residue miniprotein Omomyc, thus highlighting selective late-stage synthetic modifications. Metal-assisted cysteine alkylation is also effective for incorporating dehydroalanine into unprotected peptides and for peptide cyclisation via aliphatic thioether crosslinks, including customising macrocycles to stabilise helical peptides for enhanced uptake and delivery to proteins inside cells. Chemoselective and efficient late-stage Zn2+-promoted cysteine alkylation in unprotected peptides and proteins promises many useful applications.  相似文献   
30.
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   
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