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   19774篇
  免费   1382篇
  国内免费   795篇
电工技术   1015篇
技术理论   4篇
综合类   1022篇
化学工业   3595篇
金属工艺   882篇
机械仪表   1176篇
建筑科学   1327篇
矿业工程   521篇
能源动力   551篇
轻工业   1077篇
水利工程   289篇
石油天然气   1120篇
武器工业   127篇
无线电   2611篇
一般工业技术   2626篇
冶金工业   1026篇
原子能技术   166篇
自动化技术   2816篇
  2024年   62篇
  2023年   309篇
  2022年   520篇
  2021年   752篇
  2020年   548篇
  2019年   509篇
  2018年   570篇
  2017年   587篇
  2016年   548篇
  2015年   682篇
  2014年   890篇
  2013年   1210篇
  2012年   1133篇
  2011年   1275篇
  2010年   990篇
  2009年   1024篇
  2008年   1004篇
  2007年   964篇
  2006年   1014篇
  2005年   914篇
  2004年   610篇
  2003年   596篇
  2002年   519篇
  2001年   442篇
  2000年   525篇
  1999年   579篇
  1998年   528篇
  1997年   458篇
  1996年   441篇
  1995年   317篇
  1994年   301篇
  1993年   213篇
  1992年   170篇
  1991年   139篇
  1990年   125篇
  1989年   95篇
  1988年   77篇
  1987年   52篇
  1986年   44篇
  1985年   37篇
  1984年   21篇
  1983年   18篇
  1982年   30篇
  1981年   22篇
  1980年   15篇
  1979年   10篇
  1978年   11篇
  1977年   11篇
  1976年   12篇
  1971年   8篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
141.
How to express the designer’s creative intent in a simple and intuitive way is the main problem in 3d modeling, especially for novice designers. This paper presents a free shape 3d modeling system for creative design based on modified Catmull-Clark subdivision. The system contains a series of easy but novel operations which can be used to change the topology of models, such as creating holes and handles. In order to create sharp features, feature marking operations are provided to specify where the sharp feature is. This system also provides surface conversion function to make the modeling results be compatible with the traditional CAD systems. Firstly, a simple but efficient quad domain division scheme is adopted to generate quad sub-meshes. In order to improve the smoothness at the regular vertices, long boundary curves which across multiple sub-meshes are used to be the boundary constraints while fitting. In this way, the smoothness at regular vertex can be C2 continuous. We perform experiments for both skilled and novice designers. Results show that our system is easy to operate and can be used to construct complex models with less time.  相似文献   
142.
We construct two sets of incomplete and extendible quantum pure orthogonal product states (POPS) in general bipartite high-dimensional quantum systems, which are all indistinguishable by local operations and classical communication. The first set of POPS is composed of two parts which are \(\mathcal {C}^m\otimes \mathcal {C}^{n_1}\) with \(5\le m\le n_1\) and \(\mathcal {C}^m\otimes \mathcal {C}^{n_2}\) with \(5\le m \le n_2\), where \(n_1\) is odd and \(n_2\) is even. The second one is in \(\mathcal {C}^m\otimes \mathcal {C}^n\) \((m, n\ge 4)\). Some subsets of these two sets can be extended into complete sets that local indistinguishability can be decided by noncommutativity which quantifies the quantumness of a quantum ensemble. Our study shows quantum nonlocality without entanglement.  相似文献   
143.
In this paper, the distributed control of the LQR problem for continuous-time multi-agent systems is considered. Based on the centralized optimal control, we prove that the solution of the algebraic Riccati equation is the maximal solution of the algebraic Riccati inequality. The algebraic relations of the solutions of the algebraic Riccati equations for different weighted matrices are shown and two distributed controllers are designed: the fully distributed one and the interconnected distributed one. They can provide an upper bounds and a lower bounds of the centralized optimal cost function. The optimal closed-loop feedback control systems for the two distributed controllers are also asymptotically stable. Some examples are given to show the correctness of the proposed results.  相似文献   
144.
How the Kano model contributes to Kansei engineering in services   总被引:1,自引:0,他引:1  
Hartono M  Chuan TK 《Ergonomics》2011,54(11):987-1004
Recent studies show that products and services hold great appeal if they are attractively designed to elicit emotional feelings from customers. Kansei engineering (KE) has good potential to provide a competitive advantage to those able to read and translate customer affect and emotion in actual product and services. This study introduces an integrative framework of the Kano model and KE, applied to services. The Kano model was used and inserted into KE to exhibit the relationship between service attribute performance and customer emotional response. Essentially, the Kano model categorises service attribute quality into three major groups (must-be [M], one-dimensional [O] and attractive [A]). The findings of a case study that involved 100 tourists who stayed in luxury 4- and 5-star hotels are presented. As a practical matter, this research provides insight on which service attributes deserve more attention with regard to their significant impact on customer emotional needs. STATEMENT OF RELEVANCE: Apart from cognitive evaluation, emotions and hedonism play a big role in service encounters. Through a focus on delighting qualities of service attributes, this research enables service providers and managers to establish the extent to which they prioritise their improvement efforts and to always satisfy their customer emotions beyond expectation.  相似文献   
145.
In this paper, we will investigate the implementation of the parallelization approaches used in the program of discharge simulation along resin insulator surfaces in SF6/N2 gas mixture which initially consumes a great deal of computational time. In a general way, this simulation program spent 10 days of execution to achieve satisfactory research results. For this reason, the goal of our paper is to reduce the execution time by parallelizing this program. Three parallelization approaches were used in our simulation: (i) splitting by different types of the charged particles using a distributed-memory approach, (ii) splitting by physical domain using a distributed-memory approach, and (iii) splitting by both domain and charged particles using multi-level distributed and shared memory approach. At last, the three approaches are tested on a Linux cluster composed of six dual-core PCs, and the experimental results show that all the parallelization approaches achieve the goal of reducing the execution time to a certain extent. In addition, among these approaches, the multi-level approach offers the most effective parallelization method for implementing this simulation on symmetrical multi-processing (SMP) clusters.  相似文献   
146.
This paper describes a novel linearly-weighted gradient smoothing method (LWGSM). The proposed method is based on irregular cells and thus can be used for problems with arbitrarily complex geometrical boundaries. Based on the analysis about the compactness and the positivity of coefficients of influence of their stencils for approximating a derivative, one favorable scheme (VIII) is selected among total eight proposed discretization schemes. This scheme VIII is successively verified and carefully examined in solving Poisson equations, subjected to changes in the number of nodes, the shapes of cells and the irregularity of triangular cells, respectively. Strong form of incompressible Navier–Stokes equations enhanced with artificial compressibility terms are tackled, in which the spatial derivatives are approximated by consistent and successive use of gradient smoothing operation over smoothing domains at various locations. All the test cases using LWGSM solver exhibits its robust, stable and accurate behaviors. The attained incompressible LWGSM solutions show good agreements with experimental and literature data. Therefore, the proposed LWGSM can be reliably used for accurate solutions to versatile fluid flow problems.  相似文献   
147.
一种基于ARM-Linux的分布式管道泄漏监测系统   总被引:2,自引:1,他引:1  
针对中国输油管道现场具体情况,设计一套基于嵌入式ARM-Linux和LabVIEW的分布式管道泄漏监测系统,包括远程测控终端(RTU)、监测PC以及工业局域网.详细论述了系统架构、硬件组成、软件流程等.通过实际开发与应用,证明此设计完全适用于输油管道特殊现场,不仅降低了成本与功耗,还提高了效率,为长距离石油管道运输系统...  相似文献   
148.
提出了一种基于DPT的宽带非线性调频信号的DOA估计算法.首先将非线性调频(NLFM)信号建模为高阶多项式相位信号(PPS)模型,然后通过高阶瞬时矩进行多项式相位变换.接收信号将变换为单个正弦信号和新的噪声.再利用ROOT-MUSIC或者ESPRIT算法对变换得到的正弦信号的波达方向进行估计.理论分析和仿真结果表明,该...  相似文献   
149.
基于Web与组件技术的企业应用系统设计模型   总被引:40,自引:2,他引:38  
文章介绍了“Browse-WebServe-DBMS”体系结构的三种模式及相关的程序设计技术[1],提出了一个基于Web与组件技术的企业应用系统软件设计模型,开发了一个应用实例,并统计分析了相关数据,说明了基于Web与组件技术的软件设计方法对于提高组件重用率,缩短开发周期,提高开发效率,提高系统的可维护性等具有明显的优势。  相似文献   
150.
教学软件的模糊多层次综合评价   总被引:1,自引:0,他引:1  
由于影响教学软件质量的因素很多,因而对它的评价困难较大.文章提出了采用模糊多层次综合评价方法对教学软件质量进行评价,并讨论了利用层次分析法来确定各评价因素的权重.  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