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   4328篇
  免费   108篇
  国内免费   2篇
电工技术   26篇
综合类   3篇
化学工业   661篇
金属工艺   28篇
机械仪表   35篇
建筑科学   206篇
矿业工程   85篇
能源动力   56篇
轻工业   443篇
水利工程   29篇
石油天然气   6篇
无线电   126篇
一般工业技术   465篇
冶金工业   1797篇
原子能技术   10篇
自动化技术   462篇
  2023年   15篇
  2022年   36篇
  2021年   68篇
  2020年   41篇
  2019年   50篇
  2018年   51篇
  2017年   63篇
  2016年   76篇
  2015年   58篇
  2014年   62篇
  2013年   223篇
  2012年   150篇
  2011年   195篇
  2010年   173篇
  2009年   156篇
  2008年   207篇
  2007年   203篇
  2006年   152篇
  2005年   171篇
  2004年   139篇
  2003年   159篇
  2002年   128篇
  2001年   99篇
  2000年   85篇
  1999年   107篇
  1998年   117篇
  1997年   107篇
  1996年   114篇
  1995年   86篇
  1994年   90篇
  1993年   103篇
  1992年   99篇
  1991年   40篇
  1990年   89篇
  1989年   69篇
  1988年   70篇
  1987年   73篇
  1986年   75篇
  1985年   61篇
  1984年   53篇
  1983年   49篇
  1982年   42篇
  1981年   33篇
  1980年   21篇
  1979年   34篇
  1978年   30篇
  1977年   14篇
  1976年   20篇
  1975年   18篇
  1973年   17篇
排序方式: 共有4438条查询结果,搜索用时 0 毫秒
41.
This paper discusses the adoption of a pluralist theoretical framework – one that is also multiparadigmatic – for conducting and publishing information system (IS) research. The discussion is illustrated by a single case study involving the Australian cotton industry. The theoretical framework is informed by three sociological theories, each with its particular paradigmatic assumptions: structuration theory as a meta‐theory, and diffusion of innovations and gender relations as lower‐level theories from notionally opposing paradigms. Theoretical pluralism helped to produce rich findings, illuminating both the social nature of women farmers' roles, the materiality of the cotton farming context, the characteristics of the decision support systems in use and the recursive way in which human agency and institutional pressures shape each other. Because users of so‐called divergent paradigms often face criticism based on the incommensurability issue, one of the main contributions of this paper is to discuss the value of a pluralist and multiparadigmatic theoretical framework in dealing with complex IS social phenomena.  相似文献   
42.
The pyrrolidide and picolinyl ester derivatives of the fatty acids in two natural lipid samples rich in unsaturated fatty acids, pig testis lipids and cod liver oil were satisfactorily resolved on capillary columns of fused silica coated with stationary phases of varying polarity. The picolinyl esters, in particular, when subjected to gas chromatography-mass spectrometry on a column containing a cross-linked methyl silicone, gave distinctive mass spectra, which could be interpreted in terms of both the numbers and positions of the double bonds.  相似文献   
43.
Online social networks (OSN) are technology-enabled relationship tools in which a user creates a profile, connects to other individuals, and shares user-generated content with them. One of the many features OSN offer is the ability to post messages in the form of product and service recommendations. Although word-of-mouth research has examined this type of personal communication to intentionally influence consumer decisions, limited understanding exists regarding when a user acts upon a recommendation received from one of their contacts. In this study, we draw on relationship theories and research on trust to analyze the impact relationship characteristics and behaviors of the OSN contacts have on trust in the recommendation that subsequently leads a user to act on this OSN contact’s recommendation. The results of a survey of 116 OSN users showed that closeness, excessive posting behavior, and past recommendation experience have a positive impact on trust and intention to act on the recommendation. One characteristic of the relationships, that is, similarity, however, does not affect recommendation trust in the context of OSN. The findings enhance our understanding of relationships and their defining characteristics in OSN. The results also provide insights into how companies might leverage OSN in their marketing efforts.  相似文献   
44.

Comprehension of computer programs involves identifying important program parts and inferring relationships between them. The ability to comprehend a computer program is a skill that begins its development in the novice programmer and reaches maturity in the expert programmer. This research examined the beginning of this process, that of comprehension of computer programs by novice programmers. The mental representations of the program text that novices form, which indicate the comprehension strategies being used, were examined. In the first study, 80 novice programmers were tested on their comprehension of short program segments. The results suggested that novices form detailed, concrete mental representations of the program text, supporting work that has previously been done with novice comprehension. Their mental representations were primarily procedural in nature, with little or no modeling using real‐world referents. In a second study, the upper and lower quartile comprehenders from Study 1 were tested on their comprehension of a longer program. Results supported the conclusions from Study 1 in that the novices tended towards detailed representations of the program text with little real‐world reference. However, the comprehension strategies used by high comprehenders differed substantially from those used by low comprehenders. Results indicated that the more advanced novices were using more abstract concepts in their representations, although their abstractions were detailed in nature.  相似文献   
45.
46.
Many network applications requires access to most up-to-date information. An update event makes the corresponding cached data item obsolete, and cache hits due to obsolete data items become simply useless to those applications. Frequently accessed but infrequently updated data items should get higher preference while caching, and infrequently accessed but frequently updated items should have lower preference. Such items may not be cached at all or should be evicted from the cache to accommodate items with higher preference. In wireless networks, remote data access is typically more expensive than in wired networks. Hence, an efficient caching scheme considers both data access and update patterns can better reduce data transmissions in wireless networks. In this paper, we propose a step-wise optimal update-based replacement policy, called the Update-based Step-wise Optimal (USO) policy, for wireless data networks to optimize transmission cost by increasing effective hit ratio. Our cache replacement policy is based on the idea of giving preference to frequently accessed but infrequently updated data, and is supported by an analytical model with quantitative analysis. We also present results from our extensive simulations. We demonstrate that (1) the analytical model is validated by the simulation results and (2) the proposed scheme outperforms the Least Frequently Used (LFU) scheme in terms of effective hit ratio and communication cost.  相似文献   
47.
Abstract

The ability to use and interpret algebraic variables as generalized numbers and changing quantities is fundamental to the learning of calculus. This study considers the use of variables in these advanced ways as a component of algebraic thinking. College introductory calculus students' (n = 174) written responses to algebra problems requiring the use and interpretation of variables as changing quantities were examined for evidence of algebraic and arithmetic thinking. A framework was developed to describe and categorize examples of algebraic, transitional, and arithmetic thinking reflected in these students' uses of variables. The extent to which students' responses showed evidence of algebraic or arithmetic thinking was quantified and related to their course grades. Only one third of the responses of these entering calculus students were identified as representative of algebraic thinking. This study extends previous research by showing that evidence of algebraic thinking in students' work was positively related to successful performance in calculus.  相似文献   
48.
Software developers often need to understand a large body of unfamiliar code with little or no documentation, no experts to consult, and little time to do it. A post appeared in January 2008 on Slashdot, a technology news Web site, asking for tools and techniques that could help. This article analyzes 301 often passionate and sometimes articulate responses to this query, including the themes and the associated tool recommendations. The most common suggestions were to use a code navigation tool, use a design recovery tool, use a debugger to step through the code, create a runtime trace, use problem-based learning, ask people for help, study the code from top down, and print out all the code. This analysis presents an intriguing snapshot of how software developers in industry go about comprehending big code.  相似文献   
49.
Asimov’s “three laws of robotics” and machine metaethics   总被引:1,自引:1,他引:0  
Using Asimov’s “Bicentennial Man” as a springboard, a number of metaethical issues concerning the emerging field of machine ethics are discussed. Although the ultimate goal of machine ethics is to create autonomous ethical machines, this presents a number of challenges. A good way to begin the task of making ethics computable is to create a program that enables a machine to act an ethical advisor to human beings. This project, unlike creating an autonomous ethical machine, will not require that we make a judgment about the ethical status of the machine itself, a judgment that will be particularly difficult to make. Finally, it is argued that Asimov’s “three laws of robotics” are an unsatisfactory basis for machine ethics, regardless of the status of the machine.
Susan Leigh AndersonEmail:
  相似文献   
50.
Triangulation is the means by which an alternate perspective is used to validate, challenge or extend existing findings. It is frequently used when the field of study is difficult, demanding or contentious and presence research meets all of these criteria. We distinguish between the use of hard and soft triangulation—the former emphasising the challenging of findings, the latter being more confirmatory in character. Having reviewed a substantial number of presence papers, we conclude that strong triangulation is not widely used while soft triangulation is routinely employed. We demonstrate the usefulness of hard triangulation by contrasting an ontological analysis of in-ness with an empirical study of (computer) game playing. We conclude that presence research would be well served by the wider use of hard triangulation and for the reporting of anomalous and ill-fitting results.
Susan TurnerEmail:
  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