全文获取类型
收费全文 | 108898篇 |
免费 | 13653篇 |
国内免费 | 5464篇 |
专业分类
电工技术 | 51855篇 |
技术理论 | 4篇 |
综合类 | 8603篇 |
化学工业 | 5202篇 |
金属工艺 | 2776篇 |
机械仪表 | 5457篇 |
建筑科学 | 3403篇 |
矿业工程 | 2271篇 |
能源动力 | 8112篇 |
轻工业 | 2323篇 |
水利工程 | 2851篇 |
石油天然气 | 1049篇 |
武器工业 | 857篇 |
无线电 | 15119篇 |
一般工业技术 | 4146篇 |
冶金工业 | 2009篇 |
原子能技术 | 2209篇 |
自动化技术 | 9769篇 |
出版年
2024年 | 441篇 |
2023年 | 1414篇 |
2022年 | 2720篇 |
2021年 | 3283篇 |
2020年 | 3518篇 |
2019年 | 2863篇 |
2018年 | 2639篇 |
2017年 | 3788篇 |
2016年 | 4120篇 |
2015年 | 4724篇 |
2014年 | 7720篇 |
2013年 | 6403篇 |
2012年 | 8828篇 |
2011年 | 9516篇 |
2010年 | 6968篇 |
2009年 | 7060篇 |
2008年 | 6867篇 |
2007年 | 8272篇 |
2006年 | 7335篇 |
2005年 | 5911篇 |
2004年 | 4774篇 |
2003年 | 3884篇 |
2002年 | 2975篇 |
2001年 | 2604篇 |
2000年 | 2163篇 |
1999年 | 1603篇 |
1998年 | 1077篇 |
1997年 | 853篇 |
1996年 | 801篇 |
1995年 | 615篇 |
1994年 | 554篇 |
1993年 | 352篇 |
1992年 | 308篇 |
1991年 | 193篇 |
1990年 | 159篇 |
1989年 | 128篇 |
1988年 | 100篇 |
1987年 | 69篇 |
1986年 | 46篇 |
1985年 | 45篇 |
1984年 | 68篇 |
1983年 | 54篇 |
1982年 | 57篇 |
1981年 | 25篇 |
1980年 | 16篇 |
1979年 | 13篇 |
1978年 | 17篇 |
1977年 | 8篇 |
1959年 | 15篇 |
1951年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 109 毫秒
951.
Cognitive radios such as intelligent phones and Bluetooth devices have been considered essential goods in next-generation communication systems.Such devices will have to share the same frequency band owing to the limited bandwidth resource.To improve spectrum efciency,we formulate multi-channel power allocation as a market competitive equilibrium(CE)problem,and prove that its solution exists and is unique under the condition of weak interference.We then propose two distributed power allocation algorithms achieving CE,namely the fast convergent power allocation algorithm(FCPAA)and the social-fairness-aware FCPAA(SFAF).Theoretical analysis and simulation results demonstrate that the proposed algorithms lead to better system performance in terms of the guaranteed interference temperature constraint using the price mechanism instead of a strategy based on the Nash equilibrium.Moreover,it is shown that the FCPAA maximizes total utility,and converges more quickly than the method addressed in prior research with the help of improved round-robin rules.However,the FCPAA cannot ensure the same social fairness among secondary users as the SFAF scheme in both the non-fading channel and Rayleigh fading channel;the SFAF balances the individual utility by adjusting each user’s budget at the expense of a small quantity of system total throughput. 相似文献
952.
Software systems can be represented as complex networks and their artificial nature can be investigated with approaches developed in network analysis.Influence maximization has been successfully applied on software networks to identify the important nodes that have the maximum influence on the other parts.However,research is open to study the effects of network fabric on the influence behavior of the highly influential nodes.In this paper,we construct class dependence graph(CDG)networks based on eight practical Java software systems,and apply the procedure of influence maximization to study empirically the correlations between the characteristics of maximum influence and the degree distributions in the software networks.We demonstrate that the artificial nature of CDG networks is reflected partly from the scale free behavior:the in-degree distribution follows power law,and the out-degree distribution is lognormal.For the influence behavior,the expected influence spread of the maximum influence set identified by the greedy method correlates significantly with the degree distributions.In addition,the identified influence set contains influential classes that are complex in both the number of methods and the lines of code(LOC).For the applications in software engineering,the results provide possibilities of new approaches in designing optimization procedures of software systems. 相似文献
953.
LIAO Kai CUI XiaoXin LIAO Nan MA KaiSheng WU Di WEI Wei LI Rui YU DunShan 《中国科学:信息科学(英文版)》2014,(4):269-281
With the technology scaling down, low power dissipation has become one of the research focuses in the field of integrated circuit design. Various types of adiabatic logics have been invented for low-power applications. However, the expanding leakage current degrades the performance of conventional adiabatic logics. In this article, a novel improved complementary pass-transistor adiabatic logic (ICPAL) based on fin-type field- effect transistor (FinFET) devices with ultra-low power dissipation has been presented. The proposed ICPAL takes full advantage of different FinFET operating modes, that is, shorted-gate mode, independent-gate mode, and low-power mode, to make a tremendous reduction in power dissipation. For explication and verification, the power dissipation of different ICPAL standard cells has been investigated and compared with other types of adiabatic circuits based on FinFETs. The results show that the ICPAL circuits have ultra-low power dissipation in a wide range of clock frequencies(30-800 MHz) under the condition of similar number of transistors, and the average reduction in power dissipation is about 23.1%, 75.0%, and 50.0% relative to 2N-2N2P, improved pass- transistor adiabatic logic, and complimentary pass-transistor adiabatic logic, respectively. Furthermore, ICPAL supports a better pre-evaluation of system power dissipation in VLSI design and has an intrinsic characteristic for the resistance to some types of side channel attacks. 相似文献
954.
介绍贵港地区电网基于软分区的三级自动电压控制(AVC)系统,并对该系统的三级控制原理及区域变电站的控制规则进行说明。 相似文献
955.
Jim D. Earls Jerry E. White Marvin L. Dettloff Marty J. Null 《Journal of Coatings Technology and Research》2004,1(3):243-245
Epoxidized 10-undecenoic acid triglyceride, an experimental seed oil derivative that has a terminal epoxy group on each of
the three acyl glyceride segments, has been found to have good reactivity with amine curatives and allows room temperature
cures to be obtained. Coatings based on epoxidized 10-undercenoic acid triglyceride have also shown excellent UV stability.
As an example, coatings samples placed in a QUVA chamber exhibit no loss in gloss after 3000 hr of a cycled exposure to high
intensity UV lamps and moisture at temperatures of 50–60°C. In comparison, coatings based on standard liquid epoxy resins
(LERs) and commercially available hydrogenated LERs lose gloss due to chalking/decomposition within 200–800 hr.
Presented at the 81 st Annual Meeting of the Federation of Societies for Coatings Technology, November 12–14, 2003, in Philadelphia,
PA. 相似文献
956.
根据厂区所使用的调节阀自身具备的功能以及生产工艺需求,选择合适的(三断)保位方案,分析了所选择方案的工作原理及优、缺点及适用条件. 相似文献
957.
958.
959.
960.
以IEC61312规范为指导,对岭澳#3/4机组烟囱流量信号DCS侧保险在雷暴天气期间被烧毁,同时机组出现异常报警信息的事件进行分析,明确雷电侵害DCS的途径及影响,并提出改进措施. 相似文献