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   507篇
  免费   35篇
  国内免费   1篇
电工技术   4篇
化学工业   105篇
金属工艺   7篇
机械仪表   19篇
建筑科学   22篇
矿业工程   1篇
能源动力   10篇
轻工业   71篇
水利工程   3篇
石油天然气   4篇
无线电   29篇
一般工业技术   98篇
冶金工业   62篇
原子能技术   5篇
自动化技术   103篇
  2023年   7篇
  2022年   7篇
  2021年   28篇
  2020年   11篇
  2019年   17篇
  2018年   30篇
  2017年   16篇
  2016年   31篇
  2015年   10篇
  2014年   26篇
  2013年   42篇
  2012年   33篇
  2011年   38篇
  2010年   27篇
  2009年   23篇
  2008年   22篇
  2007年   19篇
  2006年   17篇
  2005年   16篇
  2004年   9篇
  2003年   5篇
  2002年   11篇
  2001年   8篇
  2000年   2篇
  1999年   2篇
  1998年   8篇
  1997年   6篇
  1996年   4篇
  1995年   6篇
  1994年   4篇
  1993年   3篇
  1992年   3篇
  1991年   2篇
  1989年   3篇
  1988年   2篇
  1987年   2篇
  1986年   3篇
  1985年   6篇
  1984年   3篇
  1983年   2篇
  1980年   2篇
  1979年   4篇
  1978年   2篇
  1976年   7篇
  1975年   3篇
  1974年   2篇
  1973年   1篇
  1971年   1篇
  1969年   1篇
  1968年   2篇
排序方式: 共有543条查询结果,搜索用时 46 毫秒
1.
Enzymatic nanoreactors were obtained by galactose-1-phosphate uridylyl-transferase (GALT) encapsulation into plant virus capsids by a molecular self-assembly strategy. The aim of this work was to produce virus-like nanoparticles containing GALT for an enzyme-replacement therapy for classic galactosemia. The encapsulation efficiency and the catalytic constants of bio-nanoreactors were determined by using different GALT and virus coat protein ratios. The substrate affinity of nanoreactors was slightly lower than that of the free enzyme; the activity rate was 16 % of the GALT free enzyme. The enzymatic nanoreactors without functionalization were internalized into different cell lines including fibroblast and kidney cells, but especially into hepatocytes. The enzymatic nanoreactors are an innovative enzyme preparation with potential use for the treatment of classic galactosemia.  相似文献   
2.
Recent studies have shown the involvement of GluN2A subunit-containing NMDA receptors in various neurological and pathological disorders. In the X-ray crystal structure, TCN-201 ( 1 ) and analogous pyrazine derivatives 2 and 3 adopt a U-shape (hairpin) conformation within the binding site formed by the ligand binding domains of the GluN1 and GluN2A subunits. In order to mimic the resulting π/π-interactions of two aromatic rings in the binding site, a [2.2]paracyclophane system was designed to lock these aromatic rings in a parallel orientation. Acylation of [2.2]paracyclophane ( 5 ) with oxalyl chloride and chloroacetyl chloride and subsequent transformations led to the oxalamide 7 , triazole 10 and benzamides 12 . The GluN2A inhibitory activities of the paracyclophane derivatives were tested with two-electrode voltage clamp electrophysiology using Xenopus laevis oocytes expressing selectively functional NMDA receptors with GluN2A subunit. The o-iodobenzamide 12 b with the highest similarity to TCN-201 showed the highest GuN2A inhibitory activity of this series of compounds. At a concentration of 10 μM, 12 b reached 36 % of the inhibitory activity of TCN-201 ( 1 ). This result indicates that the [2.2]paracyclophane system is well accepted by the TCN-201 binding site.  相似文献   
3.
Mine Water and the Environment - Reducing the amount of water in a milled tailings storage facility (TSF) is the primary way to reduce the risk of a catastrophic failure. In addition, a significant...  相似文献   
4.

The implementation of periodic boundary conditions (PBCs) is one of the most important and difficult steps in the computational analysis of structures and materials. This is especially true in cases such as mechanical metamaterials which typically possess intricate geometries and designs which makes finding and implementing the correct PBCs a difficult challenge. In this work, we analyze one of the most common PBCs implementation technique, as well as implement and validate an alternative generic method which is suitable to simulate any possible 2D microstructural geometry with a quadrilateral unit cell regardless of symmetry and mode of deformation. A detailed schematic of how both these methods can be employed to study 3D systems is also presented.

  相似文献   
5.
6.
7.
High‐shear impellers (HSIs) are mixers used in industrial stirred tanks to incorporate powders into liquids and break down particle agglomerates. A detailed numerical study of two commercial ring‐style HSIs of laboratory scale was carried out and their performance was compared with the Rushton turbine (RT). It was found that power and pumping numbers or their ratio cannot be simply connected for properly selecting an impeller in applications where highly localized viscous dissipation is desirable. The ratio of the average viscous dissipation in the impeller swept volume to the mean in the entire volume at two constant values of power input turned out to be lower for HSIs compared to that evaluated for RT. However, at higher power input, the dimensionless average viscous dissipation in the blade swept volume was found to be similar for the HSI of two rings and the RT, corroborating the high local viscous dissipation of this HSI when operated at higher speeds.  相似文献   
8.
An explanation for the low innovation activity in construction is put forward. The central argument is that the current theory of construction is one root cause for low innovation activity. Instead, an explicit and more powerful theory of construction is needed for further innovation, which is ‘to manage new ideas into good currency’. There are three main mechanisms in the current theory of construction which are identified as causing this hindrance. Firstly, production theories in general, as well as construction theories specifically, have been implicit. Therefore, it has not been possible to transfer radical managerial innovations, such as lean production, from manufacturing to construction at a theoretical level. Direct application of this production template to construction has been limited due to the different context of construction in comparison with manufacturing. Secondly, the current theoretical model of construction is based on the transformation model of production. It is argued that the principles of this model are counterproductive, because uncertainty and interdependence are abstracted away. This leads to fragmented and myopic management and inflated variability. Practical examples show that these deficiencies and related practical constraints hinder the implementation of top-down innovations. Thirdly, empirical research shows that also bottom-up innovations - systematic learning and problem solving - are being hindered by the current theory. Thus, the advancement of innovations in construction requires that a new, explicit and valid theory of construction is created, and business models and control methods are developed on the basis of that new theory. Cet article propose une explication concernant le taux bas de l'activité d'innovation dans la secteur du bâtiment. L'argument central étant que la théorie actuelle de la construction est une des raisons fondamentales de cette activité basse d'innover. Au lieu de cela, on a besoin d'une théorie de la construction explicite et plus efficace afin d'innover. Dans la théorie actuelle du bâtiment, il y a trois mécanismes fondamentaux qui sont identifiés comme causes gênant cette innovation. Premièrement, les théories de production en général, ainsi que les théories de la construction en particulier, ont été implicites. Ainsi, il était impossible de transférer des innovations gestionnaires radicales, comme la production allégée (lean production), à partir du domaine de la fabrication à celui du bâtiment à un niveau théorique. L'application directe de ce modèle de production au secteur bâtiment a été limitée à cause du contexte différent de celui-ci en comparaison de celui de la fabrication. Deuxièmement, le modèle théorique actuel de la construction bâtiment est basé sur le modèle de la transformation de production. On avance que les principes de ce modèle agissent négativement sur la productivité parce que l'incertitude et l'interdépendance en sont exclues. Ceci mène à une gestion fragmentée et myope ainsi qu'à une inflation de la variabilité. Des exemples pratiques montrent que ces déficiences et les contraintes pratiques qui leur sont liées, gênent les implémentations des innovations de haut en bas. Troisièmement, une étude empirique montre que les innovations de bas en haut - c'est-à-dire l'apprentissage systématique et la résolution de problèmes - sont gênés par la théorie actuelle. Ainsi, le progrès dan les innovations du secteur bâtiment exige qu'une nouvelle théorie explicite et valide soit créée, et que des modèles d'affaires et des méthodes de contrôle soient développés sur la base de cette nouvelle théorie.  相似文献   
9.
Image acquisition technology is improving very fast from a performance point of view. However, there are physical restrictions that can only be solved using software processing strategies. This is particularly true in the case of super resolution (SR) methodologies. SR techniques have found a fertile application field in airborne and space optical acquisition platforms. Single-frame SR methods may be advantageous for some remote-sensing platforms and acquisition time conditions. The contributions of this article are basically two: (1) to present an overview of single-frame SR methods, making a comparative analysis of their performance in different and challenging remote-sensing scenarios, and (2) to propose a new single-frame SR taxonomy, and a common validation strategy. Finally, we should emphasize that, on the one hand, this is the first time, to the best of our knowledge, that such a review and analysis of single SR methods is made in the framework of remote sensing, and, on the other hand, that the new single-frame SR taxonomy is aimed at shedding some light when classifying some types of single-frame SR methods.  相似文献   
10.
Organic waste generated from industrial sweet potato canning is estimated to be 30% of incoming raw material with significant residual carbohydrate content. The purpose of this study was to evaluate the potential of waste generated from sweet potato processing material to support the growth of lactic acid bacteria and the production of lactic acid. The waste was comprised of 16.5% solids consisting of 18.5% ash, 4.4% protein, 20.5% simple sugars and 19% soluble starch. Following a screening of three lactic acid bacteria strains, Lactobacillus rhamnosus was deemed the best candidate for lactic acid production. The potential of various dilutions of the enzyme‐hydrolysed waste, with and without pH control, as a fermentation substrate was evaluated. Lactic acid production was highest in hydrolysed waste (without dilution) at pH set point 5.0, yielding 10 g L?1 in 72 h. Thus, lactic acid, a valuable organic compound, can be generated from sweet potato waste.  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