全文获取类型
收费全文 | 536209篇 |
免费 | 7676篇 |
国内免费 | 2587篇 |
专业分类
电工技术 | 10191篇 |
技术理论 | 5篇 |
综合类 | 1931篇 |
化学工业 | 83798篇 |
金属工艺 | 21416篇 |
机械仪表 | 15824篇 |
建筑科学 | 13195篇 |
矿业工程 | 3607篇 |
能源动力 | 11781篇 |
轻工业 | 48447篇 |
水利工程 | 6050篇 |
石油天然气 | 11621篇 |
武器工业 | 262篇 |
无线电 | 55710篇 |
一般工业技术 | 99584篇 |
冶金工业 | 106079篇 |
原子能技术 | 11729篇 |
自动化技术 | 45242篇 |
出版年
2021年 | 4328篇 |
2019年 | 3787篇 |
2018年 | 6907篇 |
2017年 | 7070篇 |
2016年 | 7964篇 |
2015年 | 5672篇 |
2014年 | 8462篇 |
2013年 | 22056篇 |
2012年 | 15072篇 |
2011年 | 20230篇 |
2010年 | 14994篇 |
2009年 | 16579篇 |
2008年 | 17381篇 |
2007年 | 17413篇 |
2006年 | 15338篇 |
2005年 | 16429篇 |
2004年 | 14597篇 |
2003年 | 13547篇 |
2002年 | 12555篇 |
2001年 | 12392篇 |
2000年 | 11237篇 |
1999年 | 11426篇 |
1998年 | 29522篇 |
1997年 | 21351篇 |
1996年 | 16255篇 |
1995年 | 12081篇 |
1994年 | 10841篇 |
1993年 | 10609篇 |
1992年 | 7845篇 |
1991年 | 7641篇 |
1990年 | 7504篇 |
1989年 | 7547篇 |
1988年 | 7215篇 |
1987年 | 6207篇 |
1986年 | 6167篇 |
1985年 | 6999篇 |
1984年 | 6680篇 |
1983年 | 6179篇 |
1982年 | 5671篇 |
1981年 | 6032篇 |
1980年 | 5693篇 |
1979年 | 5699篇 |
1978年 | 5692篇 |
1977年 | 6699篇 |
1976年 | 9027篇 |
1975年 | 5136篇 |
1974年 | 4855篇 |
1973年 | 4893篇 |
1972年 | 4201篇 |
1971年 | 3853篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Nucleation and growth mechanisms and kinetics of crystals of an amino acid salt were investigated in a methanol‐water system by measuring and evaluating the induction time as a function of the supersaturation ratio and temperature in batch salting out crystallization experiments. Discrimination between the possible crystallization mechanisms, and estimation of the kinetic parameters were carried out using nonlinear parameter identification. The results concerning the growth mechanism obtained were checked additionally by measuring the induction time as a function of number density of seed crystals. 相似文献
52.
Self-organized public-key management for mobile ad hoc networks 总被引:6,自引:0,他引:6
In contrast with conventional networks, mobile ad hoc networks usually do not provide online access to trusted authorities or to centralized servers, and they exhibit frequent partitioning due to link and node failures and to node mobility. For these reasons, traditional security solutions that require online trusted authorities or certificate repositories are not well-suited for securing ad hoc networks. We propose a fully self-organized public-key management system that allows users to generate their public-private key pairs, to issue certificates, and to perform authentication regardless of the network partitions and without any centralized services. Furthermore, our approach does not require any trusted authority, not even in the system initialization phase. 相似文献
53.
G. I. Glazov A. M. Garaiev R. V. Timerkhanov 《Chemistry and Technology of Fuels and Oils》2003,39(1-2):26-53
A series of small–capacity units has recently been constructed in regions of oil field development and crude oil and gas condensate production to satisfy the requirements for such petroleum products as naphtha, diesel fuel, kerosene, and boiler fuel and to reduce costs for delivery of these products. There are almost no data in the technical literature, particularly in periodicals, on the construction and operation of small–capacity units. We attempt to generalize the experience of Orgeneftekhimzavody Trust in this area. We hope that this experience will be useful to specialists in the development and management of small–capacity plants. 相似文献
54.
This paper presents the evolution of low-frequency, high-power transcontinental transmission, starting from the first successful transatlantic link from Poldhu up to the Italian transcontinental station of Coltano. The trend toward higher and higher transmitting power, and the dead end into which wireless was heading if it were not for research in the higher frequency ranges, are pointed out. 相似文献
55.
56.
Myers Nicholas D.; Payment Craig A.; Feltz Deborah L. 《Canadian Metallurgical Quarterly》2004,8(3):182
This study examined reciprocal relationships between collective efficacy and team performance over a season of competition in women's intercollegiate ice hockey within weekends where the opponent was constant for 2 games. Collective efficacy beliefs within 12 teams were assessed prior to both games for at least 7 weekends. Team performance indexes produced an overall measure of performance for each game. The average influence of Saturday collective efficacy on Saturday performance was moderate and positive after controlling for Friday performance. The average influence of Friday performance on Saturday collective efficacy was small and positive after removing the influence of Friday collective efficacy from Friday performance. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
57.
Stewart C. Kai Shen Dwarkadas S. Scott M.L. Jian Yin 《Distributed Systems Online, IEEE》2004,5(10):1-1
The growth of the Internet and of various intranets has spawned a wealth of online services, most of which are implemented on local-area clusters using remote invocation (for example, remote procedure call/remote method invocation) among manually placed application components. Component placement can be a significant challenge for large-scale services, particularly when application resource needs are workload dependent. Automatic component placement has the potential to maximize overall system throughput. The key idea is to construct (offline) a mapping between input workload and individual-component resource consumption. Such mappings, called component profiles, then support high-performance placement. Preliminary results on an online auction benchmark based on J2EE (Java 2 Platform, Enterprise Edition) suggest that profile-driven tools can identify placements that achieve near-optimal overall throughput. 相似文献
58.
G. Pfaff 《Inorganic Materials》2003,39(2):123-126
A new class of special effect pigments based on synthetically manufactured silica flakes coated with metal oxides was developed and introduced into the market. Silica flake pigments show extraordinary color effects such as improved interference and strong angle-dependent behavior. They can be used in automotive paints, industrial paints, plastics, and printing inks. 相似文献
59.
60.
Removal of gold from basic solutions containing [Au(CN)2]? has been demonstrated using the inherently conducting polymer polypyrrole. Polymers containing sulfonated aromatic dopants have been found to display a significant ability to remove gold from such solutions. Experiments performed in solutions containing both gold and copper cyanide complexes indicate that the recovery process is not highly selective. However, the polypyrroles used display significantly faster rates of gold recovery than activated carbon. © 2003 Society of Chemical Industry 相似文献