全文获取类型
收费全文 | 15058篇 |
免费 | 885篇 |
国内免费 | 145篇 |
专业分类
电工技术 | 337篇 |
综合类 | 117篇 |
化学工业 | 2805篇 |
金属工艺 | 334篇 |
机械仪表 | 313篇 |
建筑科学 | 964篇 |
矿业工程 | 102篇 |
能源动力 | 415篇 |
轻工业 | 1177篇 |
水利工程 | 232篇 |
石油天然气 | 128篇 |
武器工业 | 21篇 |
无线电 | 1121篇 |
一般工业技术 | 2721篇 |
冶金工业 | 2780篇 |
原子能技术 | 90篇 |
自动化技术 | 2431篇 |
出版年
2024年 | 31篇 |
2023年 | 160篇 |
2022年 | 275篇 |
2021年 | 478篇 |
2020年 | 316篇 |
2019年 | 291篇 |
2018年 | 383篇 |
2017年 | 335篇 |
2016年 | 404篇 |
2015年 | 331篇 |
2014年 | 473篇 |
2013年 | 944篇 |
2012年 | 727篇 |
2011年 | 968篇 |
2010年 | 765篇 |
2009年 | 695篇 |
2008年 | 799篇 |
2007年 | 783篇 |
2006年 | 653篇 |
2005年 | 608篇 |
2004年 | 533篇 |
2003年 | 425篇 |
2002年 | 501篇 |
2001年 | 305篇 |
2000年 | 297篇 |
1999年 | 258篇 |
1998年 | 313篇 |
1997年 | 262篇 |
1996年 | 212篇 |
1995年 | 267篇 |
1994年 | 209篇 |
1993年 | 214篇 |
1992年 | 178篇 |
1991年 | 90篇 |
1990年 | 151篇 |
1989年 | 138篇 |
1988年 | 122篇 |
1987年 | 132篇 |
1986年 | 92篇 |
1985年 | 159篇 |
1984年 | 138篇 |
1983年 | 91篇 |
1982年 | 76篇 |
1981年 | 71篇 |
1980年 | 53篇 |
1979年 | 60篇 |
1978年 | 48篇 |
1977年 | 36篇 |
1976年 | 47篇 |
1974年 | 32篇 |
排序方式: 共有10000条查询结果,搜索用时 703 毫秒
941.
942.
The current trend in constructing high-performance computing systems is to connect a large number of machines via a fast interconnect or a large-scale network such as the Internet. This approach relies on the performance of the interconnect (or Internet) to enable fast, large-scale distributed computing. A detailed understanding of the communication traffic is required in order to optimize the operation of the entire system. Network researchers traditionally monitor traffic in the network to gain the insight necessary to optimize network operations. Recent work suggests additional insight can be obtained by also monitoring traffic at the application level. The Monitor for Application-Generated Network Traffic toolkit (MAGNeT) we describe here monitors application traffic patterns in production systems, thus enabling more highly optimized networks and interconnects for the next generation of high-performance computing systems. 相似文献
943.
Abstract. In an increasingly dynamic business environment characterized by fast cycle times, shifting markets and unstable technology, a business organization’s survival hinges on its ability to align IT capabilities with business goals. To facilitate the successful introduction of new IT applications, issues of project risk must be addressed, and the expectations of multiple stakeholders must be managed appropriately. To the extent that users and developers may harbour different perceptions regarding project risk, areas of conflict may arise. By understanding the differences in how users and project managers perceive the risks, insights can be gained that may help to ensure the successful delivery of systems. Prior research has focused on the project manager’s perspective of IT project risk. This paper explores the issue of IT project risk from the user perspective and compares it with risk perceptions of project managers. A Delphi study reveals that these two stakeholder groups have different perceptions of risk factors. Through comparison with a previous study on project manager risk perceptions, zones of concordance and discordance that must be reconciled are identified. 相似文献
944.
945.
Traditional executive information systems (EIS) user support tends to focus on technical support rather than information support. Letting executives use EIS directly for strategic information has not been successful. Adopting a combined method of case study and survey, this study explored and examined the role of information support functions from U.K. executives' point of view. It found that the use of information specialists for external information scanning, information refining, and information reporting has been perceived as important to support executives in acquiring strategic information. However, information specialists' knowledge and capability in sensing and interpreting information, executive culture, the cost of establishing such a support role are the main concerns of executives. the paper suggests that EIS users need information support, as opposed to technical support. To be effective and successful, managers' knowledge in sensing, interpreting, and using information should be elicited and shared among information specialists in light of knowledge management. 相似文献
946.
The fundamental goal of the GeoVISTA Studio project is to improve geoscientific analysis by providing an environment that operationally integrates a wide range of analysis activities, including those both computationally and visually based. Improving the infrastructure used in analysis has far-reaching potential to better integrate human-based and computationally based expertise, and so ultimately improve scientific outcomes. To address these challenges, some difficult system design and software engineering problems must be overcome.This paper illustrates the design of a component-oriented system, GeoVISTA Studio, as a means to overcome such difficulties by using state-of-the-art component-based software engineering techniques. Advantages described include: ease of program construction (visual programming), an open (non-proprietary) architecture, simple component-based integration and advanced deployment methods. This versatility has the potential to change the nature of systems development for the geosciences, providing better mechanisms to coordinate complex functionality, and as a consequence, to improve analysis by closer integration of software tools and better engagement of the human expert. Two example applications are presented to illustrate the potential of the Studio environment for exploring and better understanding large, complex geographical datasets and for supporting complex visual and computational analysis. 相似文献
947.
采用金相、X射线衍射、电子探讨显微分析、交流初始磁化率和标准应变测试技术研究了Dy0.65Tb0.25Pr0.1Fex合金的显微组织、居里温度和磁致伸缩.结果表明:合金的基体为MgCu2型立方结构的(Dy,Tb,Pr)Fe2相,当X≤1.80时,第二相为富稀土相,当X≥1.85时,为(Dy,Tb,Pr)Fe3e相,合金的居里温度在1.80≤X≤1.85区间略有增加,当X>1.85时,变化很小.合金的磁致伸缩约在x=1.80时呈现出一个峰值. 相似文献
948.
Valentin G. Peschansky Mark V. Kartsovnik 《Journal of Low Temperature Physics》1999,117(5-6):1717-1721
The dependence of the resistance and the Hall field in organic metals with the quasi-two-dimensional electron energy spectrum on the magnetic field strength and orientation is analyzed in the strong field limit. The inter-plane resistance is shown to be strongly dependent on the of magnetic field orientation. When the angle between the field and the highly conducting plane is zero, the resistance increases linearly in a relatively wide field range. The angle dependence of magnetoresistance at small is nonmonotonic: it exhibits a local minimum and then a sharp peak around = 0. The Hall constant in strong magnetic field does not depend on the field orientation. 相似文献
949.
Phillips Mark R.; McAuliff Bradley D.; Kovera Margaret Bull; Cutler Brian L. 《Canadian Metallurgical Quarterly》1999,84(6):940
[Correction Notice: An erratum for this article was reported in Vol 85(2) of Journal of Applied Psychology (see record 2007-17253-001). On page 947, the graphs within Figure 1 were incorrectly labeled. The corrected figure appears in this erratum.] This experiment examined whether a photoarray administrator's knowledge of a suspect's identity increased false identification rates. Fifty participant–administrators (PAs) presented 50 participant–witnesses (PWs) two perpetrator-absent photoarrays following a live staged crime involving two perpetrators. For one photoarray per trial, the experimenter revealed the suspect's identity to the PA. Each PA presented the photoarrays sequentially or simultaneously in the presence or absence of an observer. When the observer was present, PA knowledge of the suspect's identity had a biasing effect in sequential photoarrays only. This pattern did not emerge when the observer was absent. The experimental manipulations did not affect PAs' and PWs' ratings of photoarray fairness or PWs' ratings of pressure to make an identification. These data suggest that only administrators who are blind to the suspect's identity should present sequential photoarrays. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
950.