全文获取类型
收费全文 | 72517篇 |
免费 | 7340篇 |
国内免费 | 4171篇 |
专业分类
电工技术 | 5611篇 |
技术理论 | 3篇 |
综合类 | 5302篇 |
化学工业 | 11120篇 |
金属工艺 | 4007篇 |
机械仪表 | 4641篇 |
建筑科学 | 5572篇 |
矿业工程 | 1659篇 |
能源动力 | 2223篇 |
轻工业 | 5606篇 |
水利工程 | 1532篇 |
石油天然气 | 2694篇 |
武器工业 | 699篇 |
无线电 | 9630篇 |
一般工业技术 | 9008篇 |
冶金工业 | 2984篇 |
原子能技术 | 963篇 |
自动化技术 | 10774篇 |
出版年
2024年 | 388篇 |
2023年 | 1195篇 |
2022年 | 2330篇 |
2021年 | 3241篇 |
2020年 | 2457篇 |
2019年 | 1958篇 |
2018年 | 2097篇 |
2017年 | 2332篇 |
2016年 | 2298篇 |
2015年 | 3002篇 |
2014年 | 3773篇 |
2013年 | 4627篇 |
2012年 | 5277篇 |
2011年 | 5598篇 |
2010年 | 4964篇 |
2009年 | 4904篇 |
2008年 | 4926篇 |
2007年 | 4372篇 |
2006年 | 4114篇 |
2005年 | 3306篇 |
2004年 | 2460篇 |
2003年 | 2146篇 |
2002年 | 2434篇 |
2001年 | 2139篇 |
2000年 | 1636篇 |
1999年 | 1232篇 |
1998年 | 973篇 |
1997年 | 775篇 |
1996年 | 625篇 |
1995年 | 490篇 |
1994年 | 385篇 |
1993年 | 276篇 |
1992年 | 236篇 |
1991年 | 182篇 |
1990年 | 146篇 |
1989年 | 133篇 |
1988年 | 98篇 |
1987年 | 89篇 |
1986年 | 71篇 |
1985年 | 57篇 |
1984年 | 41篇 |
1983年 | 36篇 |
1982年 | 23篇 |
1981年 | 30篇 |
1980年 | 34篇 |
1979年 | 17篇 |
1978年 | 13篇 |
1977年 | 18篇 |
1976年 | 26篇 |
1975年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
易前 《水利水电工程设计》2006,25(4):12-13
镜面混凝土是水电工程建设中新兴的一门施工技术,在乌江索风营水电站地下厂房岩锚梁混凝土施工中采用了镜面混凝土,这在技术上是一次大胆的尝试和创新,既满足了功能上的要求,同时也达到了美观和装饰地下厂房的效果,为今后水电工程施工中广泛采用镜面混凝土技术提供了样本和宝贵经验。 相似文献
2.
Honour Index (HoI), a method to evaluate research performance within different research fields, was derived from the impact
factor (IF). It can be used to rate and compare different categories of journals. HoI was used in this study to determine
the scientific productivity of stem cell research in the Asian Four Dragons (Hong Kong, Singapore, South Korea and Taiwan)
from 1981 to 2001. The methodology applied in this study represents a synthesis of universal indicator studies and bibliometric
analyses of subfields at the micro-level. We discuss several comparisons, and conclude the developmental trend in stem cell
research for two decades.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
3.
4.
W. Shieh R. Hui X. Yi 《Photonics Technology Letters, IEEE》2006,18(10):1122-1124
We perform a systematic measurement of the degree-of-polarization (DOP) and eye-closure penalty for optical signals with orthogonal polarizations. We find that the symmetry of DOP is maintained for the orthogonal polarizations under both first and higher order polarization-mode dispersion (PMD), whereas the symmetry of eye-closure penalty is broken under second-order PMD. An orthogonal polarization pair can have large disparity of eye-closure penalty despite an identical DOP. We also demonstrate a novel approach to estimate the maximum eye-closure penalty asymmetry with three orthogonal polarizations on the Poincare/spl acute/ sphere. 相似文献
5.
6.
宽带DDS跳频源设计 总被引:1,自引:0,他引:1
直接数字合成(DDS)简单可靠、控制方便,具有很高的频率分辨率,高速转换,非常适合快速跳频的要求。在对DDS基本原理进行了简要介绍和分析后,提出宽带跳频源设计方案。 相似文献
7.
Data mining extracts implicit, previously unknown, and potentially useful information from databases. Many approaches have been proposed to extract information, and one of the most important ones is finding association rules. Although a large amount of research has been devoted to this subject, none of it finds association rules from directed acyclic graph (DAG) data. Without such a mining method, the hidden knowledge, if any, cannot be discovered from the databases storing DAG data such as family genealogy profiles, product structures, XML documents, task precedence relations, and course structures. In this article, we define a new kind of association rule in DAG databases called the predecessor–successor rule, where a node x is a predecessor of another node y if we can find a path in DAG where x appears before y. The predecessor–successor rules enable us to observe how the characteristics of the predecessors influence the successors. An approach containing four stages is proposed to discover the predecessor–successor rules. © 2006 Wiley Periodicals, Inc. Int J Int Syst 21: 621–637, 2006. 相似文献
8.
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
9.
10.
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