全文获取类型
收费全文 | 86247篇 |
免费 | 7102篇 |
国内免费 | 3119篇 |
专业分类
电工技术 | 4297篇 |
技术理论 | 4篇 |
综合类 | 4344篇 |
化学工业 | 15363篇 |
金属工艺 | 4354篇 |
机械仪表 | 5440篇 |
建筑科学 | 5117篇 |
矿业工程 | 1298篇 |
能源动力 | 2819篇 |
轻工业 | 6548篇 |
水利工程 | 1302篇 |
石油天然气 | 2614篇 |
武器工业 | 484篇 |
无线电 | 12200篇 |
一般工业技术 | 13318篇 |
冶金工业 | 4594篇 |
原子能技术 | 1116篇 |
自动化技术 | 11256篇 |
出版年
2024年 | 202篇 |
2023年 | 1110篇 |
2022年 | 1906篇 |
2021年 | 3091篇 |
2020年 | 2226篇 |
2019年 | 2067篇 |
2018年 | 2387篇 |
2017年 | 2518篇 |
2016年 | 2710篇 |
2015年 | 3131篇 |
2014年 | 4075篇 |
2013年 | 5371篇 |
2012年 | 5554篇 |
2011年 | 6379篇 |
2010年 | 5456篇 |
2009年 | 5159篇 |
2008年 | 5074篇 |
2007年 | 4497篇 |
2006年 | 4332篇 |
2005年 | 3733篇 |
2004年 | 2936篇 |
2003年 | 2749篇 |
2002年 | 3016篇 |
2001年 | 2553篇 |
2000年 | 2083篇 |
1999年 | 1893篇 |
1998年 | 2028篇 |
1997年 | 1508篇 |
1996年 | 1344篇 |
1995年 | 1065篇 |
1994年 | 850篇 |
1993年 | 667篇 |
1992年 | 485篇 |
1991年 | 411篇 |
1990年 | 320篇 |
1989年 | 287篇 |
1988年 | 232篇 |
1987年 | 175篇 |
1986年 | 154篇 |
1985年 | 113篇 |
1984年 | 89篇 |
1983年 | 70篇 |
1982年 | 61篇 |
1981年 | 66篇 |
1980年 | 65篇 |
1979年 | 31篇 |
1977年 | 40篇 |
1976年 | 66篇 |
1975年 | 34篇 |
1974年 | 18篇 |
排序方式: 共有10000条查询结果,搜索用时 312 毫秒
101.
In this paper we study the optimization issues of ring networks employing novel parallel multi‐granularity hierarchical optical add‐drop multiplexers (OADMs). In particular, we attempt to minimize the number of control elements for the off‐line case. We present an integer linear programming formulation to obtain the lower bound in optimization, and propose an efficient heuristic algorithm called global bandwidth resource assignment that is suitable for the design of large‐scale OADM networks. 相似文献
102.
结合工程实例,介绍了我国第一座可拆装高架火炬的基本原理及组成,并对可拆装高架火炬与普通高架火炬在安全、技术、安装、维修、占地面积、投资等方面进行了比较,还分析了高架火炬未来的发展趋势. 相似文献
103.
Many organisations use decision models in their processes such as tables or trees to provide decision support to their operational
divisions. For example, in fault management, customer contact centre operators usually use a decision model in the form of
prescribed interviews. Based on the answers given by customers, the operator navigates through the decision model to reach
an assessment of the problem. In order to achieve customer satisfaction and operational excellence, it is very important to
constantly monitor the performance of a decision model not only on an overall level, but also on the level of individual decisions.
In this paper we present a configurable business process analytics tool, known as the intelligent Universal Service Management
System, that constantly monitors decision data and is capable of optimising the decisions based on high-level business objectives.
We explain the various features of the software and show how it can be used to optimise decision processes. We also show how
we can easily provide a customised version to monitor the performance of provision processes. 相似文献
104.
叙述了石油库在发油过程中的HSE管理;发油过程中的危害识别,包括识别范围和内容;发油过程中风险评价的常用基本方法和常见问题;发油过程中危险源的管理控制,包括建立危险源网络图、加强现场监控和制定应急预案。 相似文献
105.
The aim of this study was to evaluate the use of total coliforms (TC) and faecal coliforms (FC) using a membrane filtration method for precise monitoring of faecal pollution in Korean surface water. The samples were collected in Korea from both main rivers and their tributaries. Presumptive TC * FC were enumerated. The ratios of presumptive FC to TC were not constant, but varied widely, and TC were difficult to enumerate because of overgrowth by background colonies. For FC this was not the case. Seven hundred and three purified strains of presumptive TC * FC and their background colonies were biotyped using API 20E. Among 272 presumptive TC, non-faecal related species, Aeromonas hydrophila dominated (34.6%) and E. coli accounted for only 5.1%. In contrast, E. coli made up 89% of the 209 presumptive FC. Furthermore, of 164 background colonies on Endo Agar LES, 54.9% was A. hydrophila, while background colonies on m-FC Agar were few (58 strains), and despite their atypical colony appearance, most of them were biotyped as enteric bacteria. These results reveal that the detection of FC rather than TC using m-FC Agar is more appropriate for faecal pollution monitoring in eutrophicated surface water located in a temperate region. 相似文献
106.
107.
Soo Jin Kim Wha Young Lee Yeungho Park Wansoo Huh Young Gwan Ko 《Polymer Engineering and Science》2003,43(5):1011-1017
Supported zirconcene catalysts on a new support, MgO, were prepared and tested in ethylene polymerization. Three types of impregnation methods were employed to find an optimum supporting method for MgO. The direct impregnation of Cp2ZrCl2 on MgO showed low metal loading and polymerization activity, while the catalyst had a higher metal loading and polymerization activity when MgO was treated with methylaluminoxane (MAO) before supporting. Treatment of MgO with MAO during the supporting step invoked two types of catalytic sites, which was evidenced by the bimodal molecular weight distribution of the polymer products. MgO is considered to have potential as a support for metallocenes. 相似文献
108.
109.
The multihop optical network is the most appropriate solution to satisfy the increasing applications of Internet services. This paper extends the regular Kautz graph to one with multiple layers in order to produce more architectural variations. The connectivity between adjacent layers utilizes the systematic connection patterns of a regular Kautz graph. A routing algorithm based on its property is presented. Optical passive star (OPS) couplers are adopted to implement our new topologies. Three scheduling criteria that can solve the contention problem in the intermediate nodes are evaluated and compared in terms of their capability to improve the accessibility. 相似文献
110.
Jin Tae Kim Keun Byoung Yoon Choon-Gi Choi 《Photonics Technology Letters, IEEE》2004,16(7):1664-1666
A novel fabrication process using a hot embossing technique has been developed for micromechanical passive alignment of polymer planar lightwave circuit (PLC) devices. With only one step of embossing, single-mode waveguide straight channels and micropedestals for passive aligning are simultaneously defined on a polymer thin film with an accuracy of /spl plusmn/0.5 /spl mu/m. This process reduces the steps for fabricating alignment structures. A fabricated polymer PLC chip and fibers are combined on a v-grooved silicon optical bench (SiOB) in a flip-chip manner. The process provides a coupling loss as low as 0.67 dB per coupling face and a cost-effective packaging solution for various polymer PLC devices. 相似文献