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   24430篇
  免费   557篇
  国内免费   124篇
电工技术   793篇
综合类   106篇
化学工业   4244篇
金属工艺   1337篇
机械仪表   1704篇
建筑科学   487篇
矿业工程   314篇
能源动力   264篇
轻工业   951篇
水利工程   405篇
石油天然气   862篇
武器工业   11篇
无线电   2418篇
一般工业技术   5789篇
冶金工业   2190篇
原子能技术   460篇
自动化技术   2776篇
  2023年   121篇
  2022年   522篇
  2021年   729篇
  2020年   481篇
  2019年   638篇
  2018年   1262篇
  2017年   1300篇
  2016年   1568篇
  2015年   932篇
  2014年   1337篇
  2013年   1803篇
  2012年   1600篇
  2011年   1482篇
  2010年   1414篇
  2009年   1614篇
  2008年   1502篇
  2007年   1377篇
  2006年   1132篇
  2005年   710篇
  2004年   446篇
  2003年   242篇
  2002年   243篇
  2001年   198篇
  2000年   493篇
  1999年   387篇
  1998年   392篇
  1997年   389篇
  1996年   88篇
  1995年   45篇
  1994年   37篇
  1993年   34篇
  1992年   29篇
  1991年   24篇
  1990年   30篇
  1989年   17篇
  1988年   15篇
  1985年   25篇
  1984年   28篇
  1983年   23篇
  1982年   16篇
  1981年   19篇
  1980年   30篇
  1979年   20篇
  1978年   29篇
  1977年   20篇
  1976年   27篇
  1975年   15篇
  1974年   15篇
  1969年   24篇
  1968年   15篇
排序方式: 共有10000条查询结果,搜索用时 11 毫秒
81.
Quality function deployment (QFD) is a customer-oriented design tool for developing new or improved products to achieve higher customer satisfaction by integrating various functions of an organization. The engineering characteristics (ECs) affecting the product performances are designed to match the customer attributes (CAs). However, from the viewpoint of the QFD team, product design processes are performed in imprecise environments, and more than one factor must be taken into account in determining the target levels of ECs, especially the limited resources and increased market competition. This paper presents an imprecise goal programming (GP) approach to determine the optimum target levels of ECs in QFD for maximizing customer satisfaction under resource limitation and considerations of market competition. Based on benchmarking data of CAs, the concept of satisfaction functions is utilized to formulate explicitly the customer's preferences and to integrate the competitive analysis of target market into the modelling and solution process. In addition, the relationships linking CAs and ECs and the ECs to each other are integrated by functional relationships. The proposed approach will be illustrated through a car door design example.  相似文献   
82.
In infrastructure financed projects, in order to attract private investors, host governments often provide some guarantees. This paper develops a value model of minimum revenue guarantee with multiple-exercise real options under the impact of the emergency incident. The model is applied to infrastructure financed projects using the minimum revenue guarantee under simulation. The simulation results indicate that, before quantifying the value of the minimum revenue guarantee, it is necessary to forecast the jump degree and intensity of the emergency incident, as well as prevent and control risks arising from such emergencies. Otherwise, underestimation of the guarantee value will occur and the government will have to bear huge debt in this condition. We also analyze the dependence of the guaranteed value on the minimum guaranteed revenue level, initial revenue and number of exercise rights. For various conditions, the diagrams of the guaranteed value are also presented.  相似文献   
83.
For a linear controllable system, the problem of reconstruction of all input signals, which are compatible with the measured signal, is considered. It is assumed that information can be transmitted in a processing center only via digital communication channel at discrete time instants, and the word length is limited. In this connection, there are encoding and decoding devices in the communication channel. For simplicity, the communication channel is assumed to be noiseless and delay-free. Defining relationships are obtained for the set of compatible input signals, as well as relationships between reconstruction precision, length of transmitted word and transmission frequency.  相似文献   
84.
The paper is devoted to developing methods for control of ecological-economic systems consisting of three hierarchically subordinate subjects of control. In describing the dynamics of a system state, equations in partial derivatives that are solved numerically according to a semi-implicit scheme of the finite-difference method are used. To achieve its main goal (maintenance of an ecological subsystem in stable state), the subject of control of the upper level applies different control methods. Methods of hierarchical control (motivation, enforcement, and persuasion) that differ in the direction of action (on the objective function or domain of admissible controls) are proposed; examples of their use are represented and a comparative analysis of the obtained results is made.  相似文献   
85.
In this study, an optimization of the airfoil of a sailplane is carried out by a recently developed multi-objective genetic algorithm based on microevolution, containing crowding, range adaptation, knowledge-based reinitialization and ε-dominance. Its efficiency was tested on a set of test problems. The results are encouraging, suggesting that very small populations can be used effectively to solve real-world multi-objective optimization problems in many cases of interest.  相似文献   
86.
High user interaction capability of mobile devices can help improve the accuracy of mobile visual search systems. At query time, it is possible to capture multiple views of an object from different viewing angles and at different scales with the mobile device camera to obtain richer information about the object compared to a single view and hence return more accurate results. Motivated by this, we propose a new multi-view visual query model on multi-view object image databases for mobile visual search. Multi-view images of objects acquired by the mobile clients are processed and local features are sent to a server, which combines the query image representations with early/late fusion methods and returns the query results. We performed a comprehensive analysis of early and late fusion approaches using various similarity functions, on an existing single view and a new multi-view object image database. The experimental results show that multi-view search provides significantly better retrieval accuracy compared to traditional single view search.  相似文献   
87.
This paper presents an approach to automatic course generation and student modeling. The method has been developed during the European funded projects Diogene and Intraserv, focused on the construction of an adaptive e-learning platform. The aim of the platform is the automatic generation and personalization of courses, taking into account pedagogical knowledge on the didactic domain as well as statistic information on both the student’s knowledge degree and learning preferences. Pedagogical information is described by means of an innovative methodology suitable for effective and efficient course generation and personalization. Moreover, statistic information can be collected and exploited by the system in order to better describe the student’s preferences and learning performances. Learning material is chosen by the system matching the student’s learning preferences with the learning material type, following a pedagogical approach suggested by Felder and Silverman. The paper discusses how automatic learning material personalization makes it possible to facilitate distance learning access to both able-bodied and disabled people. Results from the Diogene and Intraserv evaluation are reported and discussed.  相似文献   
88.
A technique for measuring the charges of relativistic nuclei in thick emulsion layers irradiated in a longitudinal direction is described. This technique has been implemented on the PAVICOM completely automated facility at the Lebedev Physical Institute. The calibration curves for relativistic nuclei with Z > 3 are presented. The advantages of this technique are demonstrated using charge measurements of 28Si nuclear fragments as an example.  相似文献   
89.
A new method for manufacturing multiwall carbon nanotubes by the current annealing in vacuum of the graphite paper saturated with Ni, Co, and Fe catalysts is designed. By using a scanning tunnel microscope, structural characteristics of the modified graphite paper are studied. Y- and V-shaped nanotubes are found.  相似文献   
90.
We study perfect colorings of the Johnson graph in two colors. We give sufficient conditions for a perfect coloring of the Johnson graph to be k-regular and present examples of perfect colorings. The proof of the theorem is in many respects similar to the proof of the result by Etzion and Schwartz [1] on k-regularity of perfect codes.  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