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   840篇
  免费   31篇
  国内免费   6篇
电工技术   21篇
综合类   2篇
化学工业   167篇
金属工艺   20篇
机械仪表   22篇
建筑科学   22篇
矿业工程   3篇
能源动力   22篇
轻工业   53篇
水利工程   12篇
石油天然气   3篇
无线电   80篇
一般工业技术   248篇
冶金工业   88篇
原子能技术   14篇
自动化技术   100篇
  2024年   12篇
  2023年   9篇
  2022年   17篇
  2021年   39篇
  2020年   28篇
  2019年   32篇
  2018年   33篇
  2017年   33篇
  2016年   21篇
  2015年   20篇
  2014年   38篇
  2013年   64篇
  2012年   43篇
  2011年   48篇
  2010年   38篇
  2009年   37篇
  2008年   36篇
  2007年   34篇
  2006年   34篇
  2005年   38篇
  2004年   15篇
  2003年   16篇
  2002年   19篇
  2001年   11篇
  2000年   9篇
  1999年   6篇
  1998年   11篇
  1997年   11篇
  1996年   13篇
  1995年   12篇
  1994年   9篇
  1993年   8篇
  1992年   7篇
  1991年   11篇
  1990年   2篇
  1989年   10篇
  1988年   6篇
  1987年   6篇
  1986年   4篇
  1985年   2篇
  1984年   3篇
  1983年   7篇
  1982年   6篇
  1981年   3篇
  1980年   2篇
  1973年   4篇
  1971年   2篇
  1968年   1篇
  1965年   1篇
  1962年   1篇
排序方式: 共有877条查询结果,搜索用时 0 毫秒
11.
Wireless Personal Communications - Finding the best path between a given source and a destination in a road network is an important problem. It has its applications in various map services and...  相似文献   
12.
For efficient charge separations, multimaterial hetero‐nanostructures are being extensively studied as photocatalysts. While materials with one heterojunction are widely established, the chemistry of formation of multijunction heterostructures is not explored. This needs a more sophisticated approach and modulations. To achieve these, a generic multistep seed mediated growth following controlled ion diffusion and ion exchange is reported which successfully leads to triple‐material hetero‐nanostructures with bimetallic‐binary alloy‐binary/ternary semiconductors arrangements. Ag2S nanocrystals are used as primary seeds for obtaining AuAg‐AuAgS bimetallic‐binary alloyed metal–semiconductor heterostructures via partial reduction of Ag(I) using Au(III) ions. These are again explored as secondary seeds for obtaining a series of triple‐materials heterostructures, AuAg‐AuAgS‐CdS (or ZnS or AgInS2), with introduction of different divalent and trivalent ions. Chemistry of each step of the gold ion–induced changes in the rate of diffusion and/or ion exchanges are investigated and the formation mechanism for these nearly monodisperse triple material heterostructures are proposed. Reactions without gold are also performed, and the change in the reaction chemistry and growth mechanism in presence of Au is also discussed.  相似文献   
13.
While a query result in a traditional database is a subset of the database, in a video database, it is a set of subintervals extracted from the raw video sequence. It is very hard, if not impossible, to predetermine all the queries that will be issued in the future, and all the subintervals that will become necessary to answer them. As a result, conventional query frameworks are not applicable to video databases. We propose a new video query model that computes query results by dynamically synthesizing needed subintervals from fragmentary indexed intervals in the database. We introduce new interval operations required for that computation. We also propose methods to compute relative relevance of synthesized intervals to a given query. A query result is a list of synthesized intervals sorted in the order of their degree of relevance  相似文献   
14.
Nickel was vacuum-deposited at high temperature (1000–1600°C) on alumina and at room temperature on Hiflosupercel (diatomaceous earth). Light microscopy/Scanning electron microscopy/Energy Dispersive x-ray analysis investigations on the coated materials indicate structural features such as uniform dispersal and firm binding of nickel crystallites on the oxide surfaces and suggests that the feasibility of vacuum technology may offer certain advantages over the conventional processes for making dispersed metal catalysts.  相似文献   
15.
A new approach for dynamic job scheduling in mesh-connected multiprocessor systems, which supports a multiuser environment, is proposed in this paper. Our approach combines a submesh reservation policy with a priority-based scheduling policy to obtain high performance in terms of high throughput, high utilization, and low turn-around times for jobs. This high performance is achieved at the expense of scheduling jobs in a strictly fair, FCFS fashion; in fact, the algorithm is parameterized to allow trade-offs between performance and (short-term) POPS fairness. The proposed scheduler can be used with any submesh allocation policy. A fast and efficient implementation of the proposed scheduler has also been presented. The performance of the proposed scheme has been compared with the FCFS policy, the only existing scheduling strategy for meshes, to demonstrate the effectiveness of the proposed approach. Simulation results indicate that our scheduling strategy outperforms the FCFS policy significantly. Specifically, our strategy significantly reduces the average waiting delay of jobs over the FCFS policy. The fast implementation of the proposed scheduler results in low allocation and deallocation time overhead, as well as low space overhead  相似文献   
16.
The experimental thermodynamic of MgB2 synthesis process and phase compositions have been investigated by diffraction thermal analysis (DTA) technology and X-ray diffraction. The fabrication of MgB2 bulks and superconducting properties at the temperatures range from 600 to 800°C were reported. And microstructure of MgB2 bulks were observed by scanning electron microscope (SEM). A method was developed to determine the porosity of MgB2 and the highest density can be obtained in MgB2 prepared at 650°C at ambient pressure. It is found that the vapor pressure of Mg increases remarkably at high temperature, leading to the high porosity in MgB2 samples. MgB2 bulk with good superconducting property and fine microstructure was synthesized at 750°C.  相似文献   
17.
An error tolerant hardware efficient verylarge scale integration (VLSI) architecture for bitparallel systolic multiplication over dual base, which canbe pipelined, is presented. Since this architecture has thefeatures of regularity, modularity and unidirectionaldata flow, this structure is well suited to VLSIimplementations. The length of the largest delay pathand area of this architecture are less compared to the bitparallel systolic multiplication architectures reportedearlier. The architecture is implemented using Austria Micro System's 0.35 μm CMOS (complementary metaloxide semiconductor) technology. This architecture canalso operate over both the dual-base and polynomialbase.  相似文献   
18.
19.
Chloride induced reinforcement corrosion in concrete is a serious durability problem. Different sources of chloride, i.e. chloride introduced at the fresh stage of concrete (i.e. internal chloride) and chloride entered during the hardened state (i.e. external chloride) may affect the performance of concrete in different ways. For the performance evaluation of reinforced concrete in chloride environment (i.e. both internal and external chloride), there is a need for performing different electrochemical tests to obtain various corrosion parameters that will specify the possibility and the magnitude of corrosion in concrete. In the present study, the results of an experimental investigation that includes different corrosion tests namely potential measurement, corrosion rate measurement and potentiodynamic polarization test have been presented and analyzed to evaluate the performance of concrete both in internal chloride and external chloride exposure conditions. In addition an attempt is made to correlate the corrosion parameters obtained from internal and external chloride exposure conditions. From the results it was observed that, dropped half-cell potential value obtained from external chloride exposure mostly lie in the active zone obtained from internal chloride exposure. In addition it was observed that there was significant difference in corrosion current values obtained from both internal and external chloride exposure conditions. Further on the basis of overall ranking obtained from the results of critical parameters from different exposure conditions, the performance of different cement–steel combinations against chloride induced rebar corrosion has been evaluated.  相似文献   
20.
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