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   3703篇
  免费   340篇
  国内免费   3篇
电工技术   28篇
综合类   7篇
化学工业   923篇
金属工艺   65篇
机械仪表   53篇
建筑科学   141篇
矿业工程   77篇
能源动力   39篇
轻工业   681篇
水利工程   24篇
石油天然气   8篇
无线电   205篇
一般工业技术   632篇
冶金工业   775篇
原子能技术   19篇
自动化技术   369篇
  2023年   43篇
  2022年   70篇
  2021年   121篇
  2020年   84篇
  2019年   70篇
  2018年   92篇
  2017年   134篇
  2016年   168篇
  2015年   138篇
  2014年   170篇
  2013年   271篇
  2012年   182篇
  2011年   214篇
  2010年   161篇
  2009年   143篇
  2008年   172篇
  2007年   173篇
  2006年   111篇
  2005年   103篇
  2004年   93篇
  2003年   74篇
  2002年   71篇
  2001年   55篇
  2000年   47篇
  1999年   53篇
  1998年   206篇
  1997年   134篇
  1996年   78篇
  1995年   60篇
  1994年   64篇
  1993年   40篇
  1992年   18篇
  1991年   23篇
  1990年   16篇
  1989年   15篇
  1988年   31篇
  1987年   17篇
  1986年   18篇
  1985年   17篇
  1984年   30篇
  1983年   20篇
  1982年   16篇
  1981年   16篇
  1980年   15篇
  1979年   14篇
  1977年   21篇
  1976年   27篇
  1975年   9篇
  1943年   8篇
  1940年   8篇
排序方式: 共有4046条查询结果,搜索用时 15 毫秒
101.
This study was performed to characterize pear protease proteolytic activity and investigate the use of pear protease as a meat tenderizer. Pear protease was purified and stabilized by 5% dextrin during lyophilization (dry) or concentration (liquid). Pear protease was further characterized with respect to pH, thermodynamics, and enzyme kinetics. Pear protease was stable at a pH range of 5-8 with an optimum pH of 6.5. From Arrhenius plots, liquid protease showed higher temperature dependency (23.49 kJ/mol) than dry protease (18.62 kJ/mol) due to its higher activation energy. The kcat/Km, catalytic efficiency of enzyme, was similar with 2.9 and 2.7 µM/min with dry and liquid proteases. Pear protease was evaluated for its proteolytic activities with casein and beef myofibrillar proteins by individually and combination with fig and kiwifruit proteases. These result indicated that pear and kiwifruit proteases could be complementary to be a desirable product for meat tenderization.  相似文献   
102.
A highly nonlinear increase in electrical conductivity and concomitant photoemission occurs not only during “flash sintering” but also in presintered, dense specimens. We report results from experiments with dense specimens that show a strong correspondence between the intensity of photoemission and electrical conductivity of specimens under a variety of conditions of the electrical parameters. It is proposed that both properties are related to the concentration of electron–hole pairs generated in such experiments.  相似文献   
103.
Generating sentences from a library of signs implemented through a sparse set of key frames derived from the segmental structure of a phonetic model of ASL has the advantage of flexibility and efficiency, but lacks the lifelike detail of motion capture. These difficulties are compounded when faced with real-time generation and display. This paper describes a technique for automatically adding realism without the expense of manually animating the requisite detail. The new technique layers transparently over and modifies the primary motions dictated by the segmental model and does so with very little computational cost, enabling real-time production and display. The paper also discusses avatar optimizations that can lower the rendering overhead in real-time displays.  相似文献   
104.
105.
The grafting mechanism of poly(vinyl acetate) macroradicals prepared by cobalt-mediated radical polymerization onto C60 is investigated. The experimental conditions directly impact the nature and stability of the PVAc/C60 adducts. In the presence of residual initiating radicals that can compete with PVAc° macroradicals for addition onto C60, mixtures of PVAc/C60 adducts having between one and eight polymer chains per C60 are formed. PVAc/C60 adducts prepared with low [PVAc]:[C60] ratios may contain weak C60–C60 bonds that further dissociate and account for the instability of the products. The formation of such dimers can be lessened by increasing the temperature from 30 °C to 100 °C. The temperature increase also allows a complete dissociation of the PVAc-Co dormant species into PVAc° macroradicals and an almost quantitative grafting of eight PVAc chains onto C60, leading to well-defined C60(PVAc)8 octa-adducts. These results might shed new light on the grafting onto C60 of macroradicals prepared by other CRP techniques.  相似文献   
106.
This competency model of a crisis manager has been developed based on cooperation with managers and experts in the field of crisis management. The brainwriting method was used to generate an overview of the competencies expected of a crisis manager. Using a mind map three basic groups of competencies were developed. The participants used Saaty's method to determine the significance of individual competencies. The different attributes of individual competencies according to the level of their development were established. Finally all individual competencies were assigned a target value which indicates the expected level of competence for the position of a crisis manager. The model of competencies is a practical tool for the establishment of crisis management system in a company.  相似文献   
107.
Each film preparation technique affects the physical properties of the resulting coating and thus defines its applicability in modern device construction. In this context solvent based spin coated and solvent‐free physical vapor deposited molecular glass photoresist films are systematically investigated for their dissolution behavior, sensitivity, and overall lithographic performance. These investigations demonstrate that the solvent‐free physical vapor deposition leads to a marked increase in sensitivity. This could be explained by the individual molecule by molecule deposition step producing a more homogeneous distribution of the multicomponent resist system, especially the photoacid generator. In addition, this assumption is supported by former published simulations focusing on aggregate formation within thin films. This work demonstrates that the lithographic sensitivity of multicomponent resist system is an intrinsic parameter to investigate molecular material distribution and indicates that the applied film preparation technique is crucial for the corresponding performance and applicability.  相似文献   
108.
Flange forming is a process which is wide spread in macro range for blanks with thicknesses from less than 1?mm up to several millimeters. Flange formed geometries are used as preforms for threads but also as device to give guidance and contact face to bolts and axles in sheet metal. A great advantage of flange forming compared to other machining processes is low process cycle time combined with high material utilization. Thus, a reasonable repertoire of knowledge has been gained for flange forming in macro range. Due to ongoing miniaturization of today??s products, flange forming is an interesting process applicable in micro range as well whereas size effects do not generally allow transfer of process limits from macro to micro range. Therefore the maximum flaring ratio for flange forming in micro range for sheet metal foil of 10?C25???m for a stainless steel 1.4301 and Copper E-Cu58 is investigated and compared with results in macro range. It is shown that the maximum flaring ratio decreases with decreasing sheet metal thickness. The resulting flange heights of experiments are compared with theoretical estimations which show a good accordance.  相似文献   
109.
Cold forming generally allows the fast generation of parts with very low tolerances. In addition, mechanical properties are improved, if work hardening materials are used. Transferring the cold forming process to micro range leads to a decrease in the maximum achievable upset ratio so that the forming process becomes inefficient. Therefore, a laser-based free form heading process has been developed to generate preforms which can be calibrated in a secondary cold forming step. The achievable upset ratios reach values of several hundreds instead of 2.1 which is common for single step mechanical upsetting. In this article, heat losses arising in the material accumulation process using laser-based free form heading are analyzed and discussed. For this purpose, the process is modeled within the framework of continuum mechanics and simulated by a finite element method. By using a numerical approach, a systematic study on heat losses is performed in order to identify the influence of radiation, heat transfer due to convection and thermal conduction during laser irradiation time. The simulation results, which are validated with experimental data, show that the radiation is the most important mechanism reducing the efficiency of the accumulation process.  相似文献   
110.
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