全文获取类型
收费全文 | 17430篇 |
免费 | 1417篇 |
国内免费 | 761篇 |
专业分类
电工技术 | 993篇 |
技术理论 | 3篇 |
综合类 | 1185篇 |
化学工业 | 3053篇 |
金属工艺 | 849篇 |
机械仪表 | 949篇 |
建筑科学 | 1406篇 |
矿业工程 | 459篇 |
能源动力 | 505篇 |
轻工业 | 988篇 |
水利工程 | 292篇 |
石油天然气 | 1164篇 |
武器工业 | 113篇 |
无线电 | 2042篇 |
一般工业技术 | 2446篇 |
冶金工业 | 774篇 |
原子能技术 | 179篇 |
自动化技术 | 2208篇 |
出版年
2024年 | 61篇 |
2023年 | 292篇 |
2022年 | 450篇 |
2021年 | 674篇 |
2020年 | 468篇 |
2019年 | 456篇 |
2018年 | 499篇 |
2017年 | 493篇 |
2016年 | 444篇 |
2015年 | 612篇 |
2014年 | 792篇 |
2013年 | 905篇 |
2012年 | 1042篇 |
2011年 | 1141篇 |
2010年 | 1011篇 |
2009年 | 1005篇 |
2008年 | 973篇 |
2007年 | 915篇 |
2006年 | 972篇 |
2005年 | 855篇 |
2004年 | 561篇 |
2003年 | 555篇 |
2002年 | 482篇 |
2001年 | 413篇 |
2000年 | 451篇 |
1999年 | 480篇 |
1998年 | 423篇 |
1997年 | 406篇 |
1996年 | 364篇 |
1995年 | 332篇 |
1994年 | 238篇 |
1993年 | 190篇 |
1992年 | 151篇 |
1991年 | 88篇 |
1990年 | 103篇 |
1989年 | 105篇 |
1988年 | 68篇 |
1987年 | 32篇 |
1986年 | 29篇 |
1985年 | 21篇 |
1984年 | 13篇 |
1983年 | 8篇 |
1982年 | 15篇 |
1981年 | 7篇 |
1980年 | 8篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1976年 | 2篇 |
1959年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
961.
962.
在实际工程中,由有限元模型得到的计算值与通过试验获得的测量值之间往往存在偏差,为了能够精确预测结构的动力响应,依据测量信息修正存在的动力模型是非常必要的。运用代数特征值反问题的理论和方法,研究了满足正交性条件的质量矩阵的修正问题,得到了Frobenius范数意义下的最优修正矩阵。 相似文献
963.
真空碳热还原氯化法从铝土矿炼铝 总被引:4,自引:9,他引:4
采用真空碳热还原氯化法从铝土矿炼铝,实验结果表明:用这种方法可以从铝土矿一步得到纯度为93.82%的金属铝,而铝土矿中的其他杂质与碳会发生反应,但因为这些杂质及其反应产物没有挥发性而留在反应残渣中,因此它们的存在对用该炼铝法所得到的铝的纯度不会有太大的影响。 相似文献
964.
基于模糊评判法的信息安全风险评估模型 总被引:1,自引:0,他引:1
论文依照风险评估的理论,提出了安全域划分的概念,并在划分的基础上提出了基于模糊综合评判法的信息安全风险评估模型。模型采用多层结构,将多因素问题简化为单因素的问题,降低了复杂度,并引入关系矩阵描述各个评价因素之间相互影响的关系,对综合评价得出的结果提出了分析方法来获得企业信息系统的综合风险评价。 相似文献
965.
Management and Construction of the Three Gorges Project 总被引:1,自引:0,他引:1
The owner-responsibility system is conducted for implementation of the Three Gorges Project (TGP). For the construction management of the project, the contracting system, the contract administration system, and the construction supervision system are executed for the project management. Contractors for civil projects are determined through bidding and contracting. The permanent equipment and construction materials are purchased through bidding. Some of large-sized construction machines and mechanical and electrical equipment are procured by the international competitive bids. Qualified engineers from qualified engineering bodies, scientific research organizations, and construction companies are selected for the construction supervision. This paper covers the construction of the TGP in some detail, particularly the main dam structure, diversion work, the construction program, and management, project cost, and financing. 相似文献
966.
Comments on the original article "Sex Differences in Intrinsic Aptitude for Mathematics and Science?: A Critical Review," by E. S. Spelke (see record 2005-15840-001). Spelke's critical review is a research-based rebuttal (though implicitly) of Summers's (2005) speech that posited a hypothesis that one of the reasons why women are underrepresented in math, science, and engineering may be sex differences in intrinsic aptitude for mathematics and science. Putting aside the question of whether the empirical evidence was sufficiently reviewed, the way Spelke conceptualized aptitude as a static rather than a dynamic quality (namely, cognitive capacities) rendered her critique of the "differences in intrinsic aptitude" hypothesis less effective in many respects. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
967.
This work investigates the fabrication of a micromechanical tunable resonator using the commercial 0.35 μm complementary metal oxide semiconductor (CMOS) process and the post-process of only one maskless wet etching. The post-process has advantages of easy execution and low cost. The post-process employs an etchant (silox vapox III) to etch the silicon dioxide layer to release the suspended structures of the resonator. The tunable resonator comprises a driving unit, a tuning unit and a sensing unit. The resonant frequency of the resonator can be tuned using a dc-biased electrostatic comb of linearly varied finger-length. Experimental results show that the resonant frequency of the resonator is about 4.8 kHz, and it has a frequency-tuning range of 6.8% at the tuning voltage of 0–25 V. 相似文献
968.
本文介绍了一种基于单片机AT89C52的自行开发、构思新颖的“Parkinson”药物药理反应测试仪的工作原理及软、硬件的设计与实现方法。 相似文献
969.
A challenging problem that confronts unstructured peer-to-peer (P2P) computing systems is how to provide efficient support
to locate desired files. This paper addresses this problem by using some quantitative information in the form of probabilistic
knowledge. Two types of probabilistic knowledge are considered in this paper: overlap between topics shared in the network
and coverage of topics at each individual peer. Based on the probabilistic knowledge, this paper proposes an adaptive probabilistic
search algorithm that can efficiently support file locating operation in the unstructured P2P network. Then, an update algorithm
is devised to keep the freshness of the probabilistic knowledge of individual peers by taking advantage of feedback from the
previous user queries. Finally, some extensive experiments are conducted to evaluate the efficiency and effectiveness of the
proposed method.
This work is partially supported by the National Natural Science Foundation of China under grant No. 60496325 and 60496327
and MoE Doctorate Subject Program under project No. 20030246023, and this work was done when the first author was visiting
University of California at Berkeley. 相似文献
970.
Continuous-Time Negotiation Mechanism for Software Agents 总被引:2,自引:0,他引:2
Bo An Kwang Mong Sim Liang Gui Tang Shuang Qing Li Dai Jie Cheng 《IEEE transactions on systems, man, and cybernetics. Part B, Cybernetics》2006,36(6):1261-1272
While there are several existing mechanisms and systems addressing the crucial and difficult issues of automated one-to-many negotiation, this paper develops a flexible one-to-many negotiation mechanism for software agents. Unlike the existing general one-to-many negotiation mechanism, in which an agent should wait until it has received proposals from all its trading partners before generating counterproposals, in the flexible one-to-many negotiation mechanism, an agent can make a proposal in a flexible way during negotiation, i.e., negotiation is conducted in continuous time. To decide when to make a proposal, two strategies based on fixed waiting time and a fixed waiting ratio is proposed. Results from a series of experiments suggest that, guided by the two strategies for deciding when to make a proposal, the flexible negotiation mechanism achieved more favorable trading outcomes as compared with the general one-to-many negotiation mechanism. To determine the amount of concession, negotiation agents are guided by four mathematical functions based on factors such as time, trading partners' strategies, negotiation situations of other threads, and competition. Experimental results show that agents guided by the four functions react to changing market situations by making prudent and appropriate rates of concession and achieve generally favorable negotiation outcomes 相似文献