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   408篇
  免费   24篇
电工技术   3篇
化学工业   188篇
金属工艺   1篇
机械仪表   9篇
建筑科学   13篇
能源动力   7篇
轻工业   51篇
水利工程   2篇
石油天然气   1篇
无线电   26篇
一般工业技术   80篇
冶金工业   20篇
自动化技术   31篇
  2024年   1篇
  2023年   9篇
  2022年   55篇
  2021年   46篇
  2020年   10篇
  2019年   14篇
  2018年   14篇
  2017年   16篇
  2016年   12篇
  2015年   7篇
  2014年   21篇
  2013年   9篇
  2012年   29篇
  2011年   29篇
  2010年   23篇
  2009年   19篇
  2008年   16篇
  2007年   16篇
  2006年   14篇
  2005年   7篇
  2004年   7篇
  2003年   5篇
  2002年   6篇
  2001年   3篇
  2000年   5篇
  1999年   5篇
  1998年   7篇
  1997年   9篇
  1996年   6篇
  1995年   1篇
  1994年   3篇
  1992年   1篇
  1991年   3篇
  1989年   1篇
  1985年   1篇
  1984年   1篇
  1980年   1篇
排序方式: 共有432条查询结果,搜索用时 15 毫秒
71.
72.
Photoactive membranes coated with TiO2 and Pt/TiO2 nanostructured thin films were produced by one-step deposition of gas phase nanoparticles on glass fiber filters. Pt/TiO2 nanoparticles (0–1.5 wt.% Pt content) were produced by flame spray pyrolysis, starting from liquid solutions of the Ti and Pt precursors, and then expanded in a supersonic beam to be deposited on the filters. The nanostructured coatings were composed of crystalline nanoparticles (mainly anatase phase), without any need of post-deposition annealing. The so obtained photocatalytic membranes were tested in hydrogen production by photo-steam reforming of ethanol in an expressly set-up diffusive photoreactor. The reaction rate was found to increase with increasing the Pt content in the photoactive material, up to 1.5 wt.% Pt. The use of these membranes allowed a significant increase of the hydrogen production rate compared to that obtained with the same photoactive Pt/TiO2 films deposited on a quartz substrate.  相似文献   
73.
The purpose of this work was the preparation and characterization of polymeric membranes for the selective recognition of saccharides using molecular imprinting technology associated with phase inversion. A system able to bind saccharides with high selectivity is particularly important in the pharmaceutical sector, since some of these compounds are constituents of molecules which can exert serious toxic effects even at very low concentrations. Two polymeric matrices were prepared using poly(ethylene‐co‐vinyl alcohol) copolymers, with an ethylene molar content of 32% and 44%, and were imprinted with two different saccharide molecules: maltose and 2‐keto‐3‐deoxy‐d ‐manno‐octulosonate (KDO). Matrices imprinted against maltose and KDO showed an easy template extraction, high binding capability and satisfactory selectivity, particularly for the matrix with an ethylene molar content of 44%. © 2017 Society of Chemical Industry  相似文献   
74.
The rheology of suspensions and mechanical properties of green bodies with cordierite composition (raw materials 37 wt% kaolin, 41 wt% talc, 22 wt% alumina, resulting in 46.6 wt% SiO2, 38.1 wt% Al2O3, 13.6 wt% MgO) and two types of starch (corn or potato) are investigated. Rotational viscometry of suspensions with solids loading 50, 60, and 70 wt% without starch showed that all tend to be shear‐thinning with a small degree of thixotropy. Suspensions with a total solids loading of 60 wt% with 25 wt% replaced by starch exhibited higher viscosity and thixotropy, but the viscometric behavior is almost identical for the two starch types (apparent viscosities 130–50 mPa ·s). Oscillatory rheometry shows that for suspensions with potato starch the onset temperature for gelatinization is 61°C–63°C, that is, lower than for corn starch (72°C–73°C). Maximum storage moduli and phase shift values after gelatinization are similar for both systems. The mechanical properties of green disks, measured via diametral compression tests, reveal clear differences between materials prepared with corn and potato starch, with the latter showing higher elastic modulus, higher strength, and higher deformation at fracture, obviously because of incompletely gelatinized starch granules in the green bodies prepared with corn starch .  相似文献   
75.
This work introduces a numerical methodology for the computation of the effective thermal conductivity (ETC) of random micro-heterogeneous materials using representative volume elements and the Fast Multipole Boundary Element Method (FMBEM). The methodology is applied to solve two-dimensional foam-like materials consisting of random distributions of circular isolated holes. The computed ETC values are successfully used to predict the temperature fields of two materials with functionally graded ETCs. Numerical and analytical results are experimentally validated. The proposed methodology is flexible and versatile, as it is capable to account for both, the geometrical and topological details of the material microstructure.  相似文献   
76.
Cordierite disks were obtained by slip casting and sintering at 1,450 °C for 2 h. Sintered disks were indented at the center of one flat surface. The fracture strength of indented disks was measured in biaxial flexure. The critical temperature differential was determined by sudden cooling of the center of the indented surface at high temperature, using a high-velocity air jet at room temperature. The initial temperature was successively increased by 10 °C until crack propagation was detected with the naked eye. Temperature and stress distributions during air impinging were calculated by a finite element analysis. The heat transfer coefficient was estimated by fitting experimental temperature profiles. A radial variation of the coefficient that considers its increment beyond the stagnation region and a diminution toward the disk periphery was assumed. The calculated cordierite thermal stresses were analysed in relation to experimental data. Also, the comparison with alumina tested in similar conditions was included.  相似文献   
77.
Testicular cancer (TC) is the most frequent tumor in young males. In the vast majority of cases, it is a curable disease; therefore, very often patients experience a long survival, also due to their young age at diagnosis. In the last decades, the role of the vitamin D deficiency related to orchiectomy has become an increasingly debated topic. Indeed, vitamin D is essential in bone metabolism and many other metabolic pathways, so its deficiency could lead to various metabolic disorders especially in long-term TC survivors. In our article, we report data from studies that evaluated the incidence of hypovitaminosis D in TC survivors compared with cohorts of healthy peers and we discuss molecular mechanisms and clinical implications.  相似文献   
78.
We investigated the effects of in vivo intraperitoneal treatment with the rat monoclonal antibody (mAb), YN1.7.4 (YN1) against intercellular adhesion molecule-1 (ICAM-1) on the ovalbumin (OA)-inhalation-induced infiltration of leukocytes into the airways of OA-sensitized mice. YN1 (100 to 400 microg) given over a period of 72 h dose-dependently reduced the influx of lymphocytes and eosinophils into the bronchial lumen by > 60% and > or = 70%, respectively, when compared with saline or purified rat IgG-treated controls. Alveolar macrophages (AM) in the bronchoalveolar lavage fluid (BALF) were also decreased by > 50%. Lung tissue inflammation as determined by histopathologic examination was reduced. The number of neutrophils in the blood of OA-sensitized mice 3 days after challenge was significantly increased by treatment with YN1. However, at 24 h and 72 h after OA-challenge, the numbers of eosinophils and mononuclear cells in the bone marrow were reduced by YN1 treatment. Additionally, at 72 h after OA-challenge, the numbers of bone-marrow neutrophils were depressed. BALF levels of interleukin-5 (IL-5) and of IgA were lower for YN1-treated mice than for controls. With increasing doses of YN1, the levels of anti-ICAM-1 mAb in the plasma were proportionally increased. To correlate these results with YN1 treatment, blood and BALF T cells and BALF eosinophils were examined with flow cytometry. Blood T cells from YN1-treated mice were unable to bind phycoerythrin (PE)-labeled anti-ICAM- mAb ex vivo. These results implied that ICAM-1 on these cells was bound (occupied) by YN1 administered in vivo. Dose-related decreases were observed in the percentage and mean channel fluorescence (MCF) values of ICAM-1+ BALF T cells and eosinophils. The percentages of CD11a+ or CD49d+ eosinophils were also suppressed. Our data suggest that ICAM-1 is an important molecule involved in the recruitment of leukocytes into the airways of sensitized mice after pulmonary challenge.  相似文献   
79.
The catalytic activity of the antibody H11 is shown to reside chiefly in its ability to hydrolyze 1-acetoxybutadiene to crotonaldehyde and to promote the cycloaddition of the intermediate enol with N-alkylmaleimides. This conclusion is based upon the demonstration that the enol tautomerizes too rapidly in solution to be a competent intermediate and that under the reaction conditions for H11, no cycloaddition occurs with crotonaldehyde and N-ethylmaleimide. As a first step towards a structural understanding of the chemistry of H11, chemical modification experiments have shown that reactions of acidic amino acids, tyrosine, lysine, and histidine, but not arginine, inhibit the reactions mediated by H11.  相似文献   
80.
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