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   31243篇
  免费   1194篇
  国内免费   111篇
电工技术   379篇
综合类   228篇
化学工业   5228篇
金属工艺   643篇
机械仪表   596篇
建筑科学   981篇
矿业工程   96篇
能源动力   948篇
轻工业   4003篇
水利工程   246篇
石油天然气   163篇
武器工业   6篇
无线电   2255篇
一般工业技术   4224篇
冶金工业   8514篇
原子能技术   243篇
自动化技术   3795篇
  2024年   51篇
  2023年   155篇
  2022年   504篇
  2021年   809篇
  2020年   549篇
  2019年   616篇
  2018年   701篇
  2017年   779篇
  2016年   738篇
  2015年   573篇
  2014年   873篇
  2013年   1450篇
  2012年   1299篇
  2011年   1616篇
  2010年   1182篇
  2009年   1236篇
  2008年   1129篇
  2007年   995篇
  2006年   807篇
  2005年   844篇
  2004年   913篇
  2003年   835篇
  2002年   807篇
  2001年   698篇
  2000年   545篇
  1999年   617篇
  1998年   2792篇
  1997年   1784篇
  1996年   1192篇
  1995年   764篇
  1994年   605篇
  1993年   657篇
  1992年   230篇
  1991年   309篇
  1990年   240篇
  1989年   211篇
  1988年   233篇
  1987年   170篇
  1986年   184篇
  1985年   196篇
  1984年   132篇
  1983年   95篇
  1982年   136篇
  1981年   132篇
  1980年   131篇
  1979年   90篇
  1978年   79篇
  1977年   175篇
  1976年   305篇
  1975年   84篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
National policies may have heterogeneous effects at the regional level. When coming to programmes aimed at increasing human capital, worker mobility from poorer to richer regions can reduce the benefits of the policy for the former areas. We focus on Italy and estimate the impact of education on the probability of migrating from a lagging area to a leading one. Endogeneity is addressed by exploiting an increase in the minimum school-leaving age in an instrumental variable framework. We find that one additional year of education increases the probability to migrate by 1.7 percentage points (9% of the average migration rate).  相似文献   
992.
This paper describes the design and implementation of SAPPHIRE – a novel middleware and software development kit for stream programing on a heterogeneous system of multi-core multi-CPUs with optional hardware accelerators such as graphics processing unit (GPU). A stream program consists of a set of tasks where the same tasks are repeated over multiple iterations of data (e.g., video frames). Examples of such programs are video analysis applications for computer-aided diagnosis and computer-assisted surgeries. Our design goal is to reduce the implementation efforts and ease collaborative software development of stream programs while supporting efficient execution of the programs on the target hardware. To validate the toolkit, we implemented EM-Automated-RT software with the toolkit and reported our experience. EM-Automated-RT performs real-time video analysis for quality of a colonoscopy procedure and provides visual feedback to assist the endoscopist to achieve optimal inspection of the colon during the procedure. The software has been deployed in a hospital setting to conduct a clinical trial.  相似文献   
993.
The Medical and Pharmaceutical industries have shown high interest in the precise engineering of protein hormones and enzymes that perform existing functions under a wide range of conditions. Proteins are responsible for the execution of different functions in the cell: catalysis in chemical reactions, transport and storage, regulation and recognition control. Computational Protein Design (CPD) investigates the relationship between 3-D structures of proteins and amino acid sequences and looks for all sequences that will fold into such 3-D structure. Many computational methods and algorithms have been proposed over the last years, but the problem still remains a challenge for Mathematicians, Computer Scientists, Bioinformaticians and Structural Biologists. In this article we present a new method for the protein design problem. Clustering techniques and a Dead-End-Elimination algorithm are combined with a SAT problem representation of the CPD problem in order to design the amino acid sequences. The obtained results illustrate the accuracy of the proposed method, suggesting that integrated Artificial Intelligence techniques are useful tools to solve such an intricate problem.  相似文献   
994.
995.
996.
We present a multidisciplinary design optimization method for the profile and structural reinforcement layout of a ram‐air kite rib. The aim is to minimize the structural elastic energy and to maximize the traction power of a ram‐air kite used for airborne wind energy generation. Because of the large deformations occurring during flight, a fluid‐structure interaction (FSI) routine is included in the optimization, which determines the actual deformed rib geometry and its corresponding aerodynamic characteristics. A qualitative comparison between FSI inclusion and exclusion in the optimization is given. Discrepancies in airfoil profile and structural layout are observed.  相似文献   
997.

Rational use of cars in smart cities can represent an economical and cheaper way to decrease the quantity of cars on the roads to better the life quality of the populations. This paper presents a low-cost deployment proposal called “URCa project” to reach these goals and proposes a paradigm change by sharing the cars considering some logistic aspects including car ride mechanism. Technical feasibility to deploy this solution was checked by means of a proof of concept. The concept was proven by passenger counting and license plate that are essential information in this solution were obtained taking photographs, applying two types of recognition algorithms and sending the results to be stored and evaluated by analytic data processes of a transit regulatory agency showing that this project is technically viable. The low-cost solution was justified by a financial analysis based on both costs (URCa solution and a bridge) that has shown a ratio of 1:10,000.

  相似文献   
998.
Olive mill wastewater (OMWW) from 3‐ and 2‐phase mills was subjected to a two‐step membrane filtration process. The obtained reverse osmosis retentate (RO‐R) is a phenolic‐rich coproduct stream, and the reverse osmosis permeate is a near‐pure water stream. A pilot‐scale spray dryer was used for the production of RO‐R powder. The optimum temperature/feed pump conditions were obtained for 3‐phase (150°C/4.4 Hz) and for 2‐phase RO‐R (175°C/3.8 Hz). The powders obtained by spray drying under these conditions were analysed for physicochemical properties, including identification and quantification of phenolic compounds. Protocatechuic acid, 3‐hydroxytyrosol, tyrosol, vanillic acid and p‐coumaric acid were quantified in both RO‐R powders, which show the possibility to obtain a phenolic‐rich powder from an OMWW filtration fraction. This will lead towards better usage of by‐products from olive oil production.  相似文献   
999.
Research on performance management (PM) of networks and radical innovation has largely developed along two isolated paths. On the one hand, a growing body of knowledge addresses the use of performance management systems in the context of networks (notably for production and incremental innovation). On the other hand, radical innovation scholars have shown how innovation initiatives that are more uncertain demand the use of new approaches (e.g., new project management routines or different evaluative tools for portfolios). Some scholars even suggest that traditional PM may suppress radical innovation. Our study takes a different approach. It aims to bridge radical innovation and network performance management through a systematic review of the literature. Here, we adopt a hybrid approach that combines bibliometrics with content analysis. Whereas the literature often separates the issues of network performance management and radical innovation, our contribution expands the theory of network management and radical innovation by developing a conceptual framework based on these concepts, thus combining them. We also offer suggestions for further research on this approach. Our framework suggests that overall, the performance management of radical innovation networks presents different features (e.g., recursive rather than linear) and constructs (e.g., openness and unintended performance) from those of innovation network management.  相似文献   
1000.
ABSTRACT

In this paper, we use the Delphi method to identify the main motivations that have led IT professionals to intend to move to another area. We found that the pursuit of career growth and the quest for acquiring new experiences and abilities have a marked impact on the IT professional turnaway intention. Moreover, female IT professionals and IT professionals oriented by the career advancement paradigm have a higher propensity to abandon the IT area.  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