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   23155篇
  免费   1720篇
  国内免费   935篇
电工技术   2359篇
技术理论   6篇
综合类   1936篇
化学工业   289篇
金属工艺   461篇
机械仪表   1787篇
建筑科学   9457篇
矿业工程   359篇
能源动力   456篇
轻工业   86篇
水利工程   792篇
石油天然气   124篇
武器工业   225篇
无线电   1002篇
一般工业技术   1137篇
冶金工业   316篇
原子能技术   53篇
自动化技术   4965篇
  2024年   73篇
  2023年   296篇
  2022年   523篇
  2021年   609篇
  2020年   696篇
  2019年   527篇
  2018年   463篇
  2017年   670篇
  2016年   715篇
  2015年   840篇
  2014年   1824篇
  2013年   2005篇
  2012年   1449篇
  2011年   1638篇
  2010年   1331篇
  2009年   1482篇
  2008年   1332篇
  2007年   1558篇
  2006年   1374篇
  2005年   1144篇
  2004年   903篇
  2003年   749篇
  2002年   669篇
  2001年   587篇
  2000年   479篇
  1999年   362篇
  1998年   264篇
  1997年   229篇
  1996年   167篇
  1995年   167篇
  1994年   151篇
  1993年   104篇
  1992年   79篇
  1991年   73篇
  1990年   53篇
  1989年   37篇
  1988年   30篇
  1987年   26篇
  1986年   8篇
  1985年   36篇
  1984年   24篇
  1983年   26篇
  1982年   15篇
  1981年   4篇
  1980年   5篇
  1979年   8篇
  1963年   1篇
  1962年   1篇
  1958年   1篇
  1955年   1篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
81.
An investigation is made into the ways proof planning can enhance the capability of a rule based prover for the theory of integration. The integrals are of the Riemann type and are defined in a way to maximize the theorem proving methods of predicate calculus. Approximately fifty theorems have been proved and several examples are discussed. A major shortcoming was found to be the inability of the system to work with or produce a proof plan. As a result, a planning scheme based on the idea of subgoals or milestones was considered. With user defined plans, there was a substantial increase in performance and capability of the system and, in some cases, proofs which were previously unsuccessful were completed.  相似文献   
82.
Although the gas metal arc welding (GMAW) process is widely used for joining metals, its planning is still a cumbersome task. The planning procedure involves many complex interrelationships among the process variables and depends heavily on empirical knowledge. Therefore, a solution method that allows a convenient way to represent the domain knowledge and evaluate the process variable relationships is needed. Further, the lack of a strong domain theory to quantify these interrelationships is a deficiency in the planning of the GMAW process. This paper presents a solution method that overcomes this deficiency and introduces a convenient knowledge representation scheme. The solution method considers the planning procedure to be a constraint satisfaction problem (CSP). The AC-4 algorithm is used to obtain arc consistency among nodes in the constraint network and the PC-4 algorithm is applied to obtain path consistency in the network. A modified version of the AC-4 algorithm is developed to reduce the search space and correspondingly reduce the computation time. An example is presented to demonstrate the capability of the method and its potential to reduce lead time.  相似文献   
83.
In this paper questions related to the occurrence of departures of a legged climbing robot from the given trajectory are considered. The basic idea of the paper is to show that, if there are slackness and non-rigidities, the legged climbing robot moving upon an inclined or vertical plane, departs systematically from the planned trajectory. It is demonstrated that these departures result from the gravity and are of systematic character. It is also shown how the inclusion of torsion effect changes substantially the nature of systematic errors arising from robot's movement along the inclined surface.  相似文献   
84.
刘庆薇 《山西建筑》2004,30(17):21-22
探讨了深圳前海物流园区的地理条件及发展的重要因素,针对其存在的交通设施不足,管理不到位等问题进行了分析,并结合功能定位从用地规模、功能布局等方面提出了规划设计构想。  相似文献   
85.
探讨低收入阶层住区建设的公共政策   总被引:5,自引:5,他引:0  
郭红旗 《山西建筑》2006,32(2):25-26
探讨了低收入阶层住区建设的现状及弊端,从旧城改造、新城建设及住房政策三方面对解决低收入阶层住区建设问题的对策进行了研究,以妥善解决低收入阶层的住房问题,从而达到构建和谐社会的目的。  相似文献   
86.
基于非确定性思考下的城市规划新思维探讨   总被引:2,自引:2,他引:0  
王卓 《山西建筑》2006,32(6):25-26
通过对城市规划编制与实施过程中的问题分析,提出非确定性城市规划思想的理念以及非确定性规划思想与确定性规划思想的差别,并在分析非确定性规划思想内涵的基础上,提出非确定性规划思想指导下的城市规划的新程式。  相似文献   
87.
This paper presents a method of solving planning problems that involve actions whose effects change according to the situations in which they are performed. The approach is an extension of the conventional planning methodology in which plans are constructed through an iterative process of scanning for goals that are not yet satisfied, inserting actions to achieve them, and introducing subgoals to these actions. This methodology was originally developed under the assumption that one would be dealing exclusively with actions that produce the same effects in every situation. The extension involves introducing additional subgoals to actions above and beyond the preconditions of execution normally introduced. These additional subgoals, called secondary preconditions, ensure that the actions are performed in contexts conducive to producing the effects we desire. This paper defines and analyzes secondary preconditions from a mathematically rigorous standpoint and demonstrates how they can be derived from regression operators.  相似文献   
88.
Reasoning about actions necessarily involves tracking the truth of assertions about the world over time. The SIPE planning system retains the efficiency of the STRIPS assumption for this while enhancing expressive power by allowing the specification of a causl theory. Separation of knowledge about causality from knowledge about actions relieves operators of much of their representational burden and allows them to be applicable in a wide range of contexts. The implementation of causal theories is described, together with examples and evaluations of the system's expressive power and efficiency.  相似文献   
89.
提出了ERP编码的原则,介绍了常见的四种编码方法:顺序码、分类码、结构码和组合码.最后结合实例介绍了编码系统中各模块的设计。  相似文献   
90.
Analogical planning provides a means of solving engineering problems where other machine learning methods fail. Unlike many machine learning paradigms, analogy does not require numerous previous examples or a rich domain theory. Instead, analogical planners adapt knowledge of solved problems in similar domains to the current problem. Unfortunately, the analogical planning task is an expensive one. While the process of forming correspondences between a known problem and a new problem is complex, the problem of selecting a base case for the analogy is virtually intractable.This paper addresses the issue of efficiently forming analogical plans. The Anagram planning system is described, which takes advantage of the massively parallel architecture of the Connection Machine to perform base selection and map formation. Anagram provides a tractable solution to analogical planning, with a complexity that is sublinear in the size of the plans.This paper describes the Anagram system and its parallel algorithms. The paper also presents theoretical analyses and empirical results of testing the system on a large database of plans from the domain of automatic programming.  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