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   4886篇
  免费   193篇
  国内免费   5篇
电工技术   39篇
综合类   5篇
化学工业   1165篇
金属工艺   82篇
机械仪表   79篇
建筑科学   216篇
矿业工程   20篇
能源动力   166篇
轻工业   371篇
水利工程   35篇
石油天然气   36篇
武器工业   2篇
无线电   446篇
一般工业技术   806篇
冶金工业   896篇
原子能技术   14篇
自动化技术   706篇
  2023年   33篇
  2022年   59篇
  2021年   91篇
  2020年   62篇
  2019年   72篇
  2018年   90篇
  2017年   93篇
  2016年   90篇
  2015年   89篇
  2014年   132篇
  2013年   368篇
  2012年   225篇
  2011年   306篇
  2010年   193篇
  2009年   226篇
  2008年   224篇
  2007年   240篇
  2006年   203篇
  2005年   162篇
  2004年   123篇
  2003年   123篇
  2002年   129篇
  2001年   98篇
  2000年   79篇
  1999年   83篇
  1998年   120篇
  1997年   104篇
  1996年   80篇
  1995年   96篇
  1994年   62篇
  1993年   58篇
  1992年   49篇
  1991年   51篇
  1990年   64篇
  1989年   47篇
  1988年   45篇
  1987年   39篇
  1986年   40篇
  1985年   57篇
  1984年   58篇
  1983年   45篇
  1982年   42篇
  1981年   36篇
  1980年   42篇
  1979年   47篇
  1978年   49篇
  1977年   40篇
  1976年   40篇
  1975年   36篇
  1973年   35篇
排序方式: 共有5084条查询结果,搜索用时 234 毫秒
41.
An efficient algorithm for mining frequent inter-transaction patterns   总被引:1,自引:0,他引:1  
In this paper, we propose an efficient method for mining all frequent inter-transaction patterns. The method consists of two phases. First, we devise two data structures: a dat-list, which stores the item information used to find frequent inter-transaction patterns; and an ITP-tree, which stores the discovered frequent inter-transaction patterns. In the second phase, we apply an algorithm, called ITP-Miner (Inter-Transaction Patterns Miner), to mine all frequent inter-transaction patterns. By using the ITP-tree, the algorithm requires only one database scan and can localize joining, pruning, and support counting to a small number of dat-lists. The experiment results show that the ITP-Miner algorithm outperforms the FITI (First Intra Then Inter) algorithm by one order of magnitude.  相似文献   
42.
Recent research has indicated that many people faced with highly aversive events suffer only minor, transient disruptions in functioning and retain a capacity for positive affect and experiences. This article reports 2 studies that replicate and extend these findings among bereaved parents, spouses, and caregivers of a chronically ill life partner using a range of self-report and objective measures of adjustment. Resilience was evidenced in half of each bereaved sample when compared with matched, nonbereaved counterparts and 36% of the caregiver sample in a more conservative, repeated-measures ipsative comparison. Resilient individuals were not distinguished by the quality of their relationship with spouse/partner or caregiver burden but were rated more positively and as better adjusted by close friends. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
43.
Implicit social cognition: Attitudes, self-esteem, and stereotypes.   总被引:1,自引:0,他引:1  
Social behavior is ordinarily treated as being under conscious (if not always thoughtful) control. However, considerable evidence now supports the view that social behavior often operates in an implicit or unconscious fashion. The identifying feature of implicit cognition is that past experience influences judgment in a fashion not introspectively known by the actor. The present conclusion--that attitudes, self-esteem, and stereotypes have important implicit modes of operation--extends both the construct validity and predictive usefulness of these major theoretical constructs of social psychology. Methodologically, this review calls for increased use of indirect measures--which are imperative in studies of implicit cognition. The theorized ordinariness of implicit stereotyping is consistent with recent findings of discrimination by people who explicitly disavow prejudice. The finding that implicit cognitive effects are often reduced by focusing judges' attention on their judgment task provides a basis for evaluating applications (such as affirmative action) aimed at reducing such unintended discrimination. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
44.
Interactive expert systems seek relevant information from a user in order to answer a query or to solve a problem that the user has posed. A fundamental design issue for such a system is therefore itsinformation-seeking strategy, which determines the order in which it asks questions or performs experiments to gain the information that it needs to respond to the user. This paper examines the problem of optimal knowledge acquisition through questioning in contexts where it is expensive or time-consuming to obtain the answers to questions. An abstract model of an expert classification system — considered as a set of logical classification rules supplemented by some statistical knowledge about attribute frequencies — is developed and applied to analyze the complexity and to present constructive algorithms for doing probabilistic question-based classification. New heuristics are presented that generalize previous results for optimal identification keys and questionnaires. For an important class of discrete discriminant analysis problems, these heuristics find optimal or near-optimal questioning strategies in a small fraction of the time required by an exact solution algorithm.  相似文献   
45.
In this paper we present a simple, general methodology for the generation of high-order operator decomposition (splitting) techniques for the solution of time-dependent problems arising in ordinary and partial differential equations. The new approach exploits operator integration factors to reduce multiple-operator equations to an associated series of single-operator initial-value subproblems. Two illustrations of the procedure are presented: the first, a second-order method in time applied to velocity-pressure decoupling in the incompressible Stokes problem; the second, a third-order method in time applied to convection-Stokes decoupling in the incompressible Navier-Stokes equations. Critical open questions are briefly described.  相似文献   
46.
Despite the possible benefits of implementing healthcare information technologies, successful implementation of effective healthcare information technology is constrained by cultural and regulatory concerns and technical obstacles encountered when establishing or upgrading an organisation's enterprise infrastructure. In this paper, we advance Ross' four‐stage model of enterprise architecture maturity as a valuable IT resource for helping healthcare organisations sustain a competitive advantage. We use partial least squares (PLS) structural equation modelling to analyse survey data from 164 US hospitals at different stages of EA maturity. Our results provide evidence that enterprise architecture maturity directly influences the effectiveness of hospitals' IT resources for achieving strategic goals. Further, enterprise architecture maturity indirectly influences the effectiveness of IT resources when IT alignment is incorporated as a mediating variable. We discuss the implications of our findings for research and practice and suggest opportunities for future research.  相似文献   
47.
A logic computer system consists of an inference machine and a compatible logic operating system. This paper describes prospective models for a logic computer system, and its hardware and software components. The language Concurrent Prolog serves as the single implementation, specification, and machine language. The computer system is represented as a logic programming goallogic_computer_system. Specification of the system corresponds to resolution of this goal. Clauses used to solve the goal — and ensuing subgoals — progressively refine the machine, operating system, and computer system designs. In addition, the accumulation of all clauses describing the logic operating system constitute its implementation. Logic computer systems with vastly different fundamental characteristics can be concisely specified in this manner. Two contrasting examples are given and discussed. An important characteristic of both peripheral devices and the overall computer system, whether they are restartable or perpetual, is examined. As well, a method for operational initialization of the logic computer system is presented. The same clauses which incrementally specify characteristics of the computer system also describe the manner in which this initialization takes place.  相似文献   
48.
49.
50.
Metallurgical and Materials Transactions A - Hot cracking is one of the major defects that can occur in laser-based additive manufacturing. During the terminal stage of solidification, hot cracking...  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