全文获取类型
收费全文 | 49777篇 |
免费 | 2672篇 |
国内免费 | 57篇 |
专业分类
电工技术 | 290篇 |
综合类 | 33篇 |
化学工业 | 9856篇 |
金属工艺 | 774篇 |
机械仪表 | 863篇 |
建筑科学 | 1401篇 |
矿业工程 | 85篇 |
能源动力 | 1266篇 |
轻工业 | 8323篇 |
水利工程 | 435篇 |
石油天然气 | 208篇 |
武器工业 | 3篇 |
无线电 | 1820篇 |
一般工业技术 | 6611篇 |
冶金工业 | 14383篇 |
原子能技术 | 230篇 |
自动化技术 | 5925篇 |
出版年
2024年 | 67篇 |
2023年 | 366篇 |
2022年 | 679篇 |
2021年 | 1295篇 |
2020年 | 954篇 |
2019年 | 1063篇 |
2018年 | 1565篇 |
2017年 | 1560篇 |
2016年 | 1685篇 |
2015年 | 1326篇 |
2014年 | 1650篇 |
2013年 | 3293篇 |
2012年 | 2592篇 |
2011年 | 2805篇 |
2010年 | 2160篇 |
2009年 | 2037篇 |
2008年 | 1934篇 |
2007年 | 1715篇 |
2006年 | 1292篇 |
2005年 | 1129篇 |
2004年 | 1050篇 |
2003年 | 958篇 |
2002年 | 847篇 |
2001年 | 612篇 |
2000年 | 572篇 |
1999年 | 833篇 |
1998年 | 4963篇 |
1997年 | 2998篇 |
1996年 | 1971篇 |
1995年 | 1065篇 |
1994年 | 870篇 |
1993年 | 951篇 |
1992年 | 220篇 |
1991年 | 223篇 |
1990年 | 183篇 |
1989年 | 201篇 |
1988年 | 211篇 |
1987年 | 203篇 |
1986年 | 168篇 |
1985年 | 190篇 |
1984年 | 115篇 |
1983年 | 97篇 |
1982年 | 109篇 |
1981年 | 137篇 |
1980年 | 169篇 |
1978年 | 66篇 |
1977年 | 322篇 |
1976年 | 642篇 |
1975年 | 68篇 |
1973年 | 62篇 |
排序方式: 共有10000条查询结果,搜索用时 115 毫秒
991.
Juan Manuel González Calleros Josefina Guerrero García Jean Vanderdonckt 《Universal Access in the Information Society》2013,12(4):387-401
The need for accessibility evaluation tools is motivated by several endogenous and exogenous reasons coming from the end user (the designer and the developer) and companies releasing information systems. Existing evaluation tools mainly concentrate on examining the code of Web pages: Web pages more and more frequently contain non-HTML parts that entirely escape from being treated by existing techniques. This is the case of the advanced human–machine interface (AHMI), a piece of software programmed in C/C++, used for controlling the advanced flight management system in the aircraft cockpit. Studying this new user interface (UI) requires a structured approach to evaluate and validate AHMI designs. The goal in this work is to develop an evaluation tool to automate the process of evaluating the AHMI. The method addresses: support of multiple bases of guidelines (accessibility or usability or both) on-demand (partial or total evaluation), with different levels of details (a presentation for developers and for those responsible for certifying accessibility). The method goes a step toward the automatic evaluation of UI containing non-HTML parts. 相似文献
992.
Roberto R. Expósito Guillermo L. Taboada Sabela Ramos Juan Touriño Ramón Doallo 《Personal and Ubiquitous Computing》2013,17(8):1709-1719
Cloud computing is posing several challenges, such as security, fault tolerance, access interface singularity, and network constraints, both in terms of latency and bandwidth. In this scenario, the performance of communications depends both on the network fabric and its efficient support in virtualized environments, which ultimately determines the overall system performance. To solve the current network constraints in cloud services, their providers are deploying high-speed networks, such as 10 Gigabit Ethernet. This paper presents an evaluation of high-performance computing message-passing middleware on a cloud computing infrastructure, Amazon EC2 cluster compute instances, equipped with 10 Gigabit Ethernet. The analysis of the experimental results, confronted with a similar testbed, has shown the significant impact that virtualized environments still have on communication performance, which demands more efficient communication middleware support to get over the current cloud network limitations. 相似文献
993.
Algorithm based on simulated annealing for land-use allocation 总被引:1,自引:0,他引:1
Inés Santé-Riveira Marcos Boullón-Magán Rafael Crecente-Maseda David Miranda-Barrós 《Computers & Geosciences》2008,34(3):259-268
This article describes the use of simulated annealing for allocation of land units to a set of possible uses on, the basis of their suitability for those uses, and the compactness of the total areas allotted to the same use or kind of use, which are fixed a priori. The results obtained for the Terra Chá district of Galicia (N.W. Spain) using different objective weighting schemes are compared with each other and with those obtained for this district under the same area constraints, using hierarchical optimization, ideal point analysis, and multi-objective land allocation (MOLA) to maximize average use suitability. Inclusion of compactness in the simulated annealing objective function avoids the highly disperse allocations typical of optimizations that ignore this sub-objective. 相似文献
994.
A randomized model verification strategy for RANSAC is presented. The proposed method finds, like RANSAC, a solution that is optimal with user-specified probability. The solution is found in time that is (i) close to the shortest possible and (ii) superior to any deterministic verification strategy. A provably fastest model verification strategy is designed for the (theoretical) situation when the contamination of data by outliers is known. In this case, the algorithm is the fastest possible (on average) of all randomized \\RANSAC algorithms guaranteeing a confidence in the solution. The derivation of the optimality property is based on Wald's theory of sequential decision making, in particular a modified sequential probability ratio test (SPRT). Next, the R-RANSAC with SPRT algorithm is introduced. The algorithm removes the requirement for a priori knowledge of the fraction of outliers and estimates the quantity online. We show experimentally that on standard test data the method has performance close to the theoretically optimal and is 2 to 10 times faster than standard RANSAC and is up to 4 times faster than previously published methods. 相似文献
995.
The main purpose of a gene interaction network is to map the relationships of the genes that are out of sight when a genomic study is tackled. DNA microarrays allow the measure of gene expression of thousands of genes at the same time. These data constitute the numeric seed for the induction of the gene networks. In this paper, we propose a new approach to build gene networks by means of Bayesian classifiers, variable selection and bootstrap resampling. The interactions induced by the Bayesian classifiers are based both on the expression levels and on the phenotype information of the supervised variable. Feature selection and bootstrap resampling add reliability and robustness to the overall process removing the false positive findings. The consensus among all the induced models produces a hierarchy of dependences and, thus, of variables. Biologists can define the depth level of the model hierarchy so the set of interactions and genes involved can vary from a sparse to a dense set. Experimental results show how these networks perform well on classification tasks. The biological validation matches previous biological findings and opens new hypothesis for future studies. 相似文献
996.
Dimas?Martínez?MoreraEmail author Paulo?Cezar?Carvalho Luiz?Velho 《The Visual computer》2008,24(12):1025-1037
This paper discusses the problem of modeling on triangulated surfaces with geodesic curves. In the first part of the paper
we define a new class of curves, called geodesic Bézier curves, that are suitable for modeling on manifold triangulations. As a natural generalization of Bézier curves, the new curves
are as smooth as possible. In the second part we discuss the construction of C
0 and C
1 piecewise Bézier splines. We also describe how to perform editing operations, such as trimming, using these curves. Special
care is taken to achieve interactive rates for modeling tasks. The third part is devoted to the definition and study of convex
sets on triangulated surfaces. We derive the convex hull property of geodesic Bézier curves.
相似文献
Luiz VelhoEmail: |
997.
In order to be capable of exploiting context for pro-active information recommendation, agents need to extract and understand
user activities based on their knowledge of the user interests. In this paper, we propose a novel approach for context-aware
recommendation in browsing assistants based on the integration of user profiles, navigational patterns and contextual elements.
In this approach, user profiles built using an unsupervised Web page clustering algorithm are used to characterize user ongoing
activities and behavior patterns. Experimental evidence show that using longer-term interests to explain active browsing goals
user assistance is effectively enhanced.
相似文献
Analía AmandiEmail: |
998.
In this work, a review and comprehensive evaluation of heuristics and metaheuristics for the m-machine flowshop scheduling problem with the objective of minimising total tardiness is presented. Published reviews about this objective usually deal with a single machine or parallel machines and no recent methods are compared. Moreover, the existing reviews do not use the same benchmark of instances and the results are difficult to reproduce and generalise. We have implemented a total of 40 different heuristics and metaheuristics and we have analysed their performance under the same benchmark of instances in order to make a global and fair comparison. In this comparison, we study from the classical priority rules to the most recent tabu search, simulated annealing and genetic algorithms. In the evaluations we use the experimental design approach and careful statistical analyses to validate the effectiveness of the different methods tested. The results allow us to clearly identify the state-of-the-art methods. 相似文献
999.
1000.
Our study investigated the effect of team knowledge on new product development (NPD). By investigating 207 NPD projects, we found that the declarative and procedural knowledge of the team and their use of IT had a positive influence on the team's knowledge base; and that the higher the functional diversity of the project team, the greater their overall knowledge. We also found that team knowledge positively impacted new product creativity and success in the market place. 相似文献