全文获取类型
收费全文 | 222781篇 |
免费 | 3172篇 |
国内免费 | 646篇 |
专业分类
电工技术 | 3768篇 |
综合类 | 183篇 |
化学工业 | 34305篇 |
金属工艺 | 8403篇 |
机械仪表 | 6506篇 |
建筑科学 | 6073篇 |
矿业工程 | 1396篇 |
能源动力 | 5712篇 |
轻工业 | 18822篇 |
水利工程 | 2502篇 |
石油天然气 | 4109篇 |
武器工业 | 8篇 |
无线电 | 24735篇 |
一般工业技术 | 44170篇 |
冶金工业 | 41446篇 |
原子能技术 | 5272篇 |
自动化技术 | 19189篇 |
出版年
2021年 | 2136篇 |
2020年 | 1491篇 |
2019年 | 1974篇 |
2018年 | 3075篇 |
2017年 | 3084篇 |
2016年 | 3376篇 |
2015年 | 2320篇 |
2014年 | 3781篇 |
2013年 | 10273篇 |
2012年 | 6136篇 |
2011年 | 8428篇 |
2010年 | 6622篇 |
2009年 | 7302篇 |
2008年 | 7527篇 |
2007年 | 7526篇 |
2006年 | 6462篇 |
2005年 | 5938篇 |
2004年 | 5701篇 |
2003年 | 5496篇 |
2002年 | 5044篇 |
2001年 | 5054篇 |
2000年 | 4918篇 |
1999年 | 5101篇 |
1998年 | 12066篇 |
1997年 | 8628篇 |
1996年 | 6820篇 |
1995年 | 5063篇 |
1994年 | 4619篇 |
1993年 | 4411篇 |
1992年 | 3471篇 |
1991年 | 3252篇 |
1990年 | 3117篇 |
1989年 | 3190篇 |
1988年 | 3022篇 |
1987年 | 2602篇 |
1986年 | 2510篇 |
1985年 | 2965篇 |
1984年 | 2712篇 |
1983年 | 2557篇 |
1982年 | 2285篇 |
1981年 | 2386篇 |
1980年 | 2180篇 |
1979年 | 2309篇 |
1978年 | 2273篇 |
1977年 | 2533篇 |
1976年 | 3405篇 |
1975年 | 1979篇 |
1974年 | 1877篇 |
1973年 | 1868篇 |
1972年 | 1525篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
Jānis Bārzdiņš Rūsiņš Freivalds Carl H. Smith 《Journal of Computer and System Sciences》2008,74(4):527-545
We study learning of predicate logics formulas from “elementary facts,” i.e. from the values of the predicates in the given model. Several models of learning are considered, but most of our attention is paid to learning with belief levels. We propose an axiom system which describes what we consider to be a human scientist's natural behavior when trying to explore these elementary facts. It is proved that no such system can be complete. However we believe that our axiom system is “practically” complete. Theorems presented in the paper in some sense confirm our hypothesis. 相似文献
102.
On the SEP of Cooperative Diversity with Opportunistic Relaying 总被引:1,自引:0,他引:1
We analyze the exact symbol error probability (SEP) of cooperative diversity with opportunistic amplify-and-forward (AF) relaying. The benefit of this opportunism to the SEP is assessed by comparing with maximal ratio combining of orthogonal multiple AF relay transmissions. 相似文献
103.
104.
Introducing new technology in a healthcare setting is a complex undertaking. In an environment in which accuracy, security, and reliability are critical elements, careful planning is the primary factor in ensuring a successful implementation. 相似文献
105.
This year, the 11th International Symposium on Wearable Computers returned to the city where it began: Boston, Massachusetts. ISWC is the premier conference in wearable computing, reporting the latest advances in research and technology. As in previous years, attendees came both from academia and industry, representing a broad spectrum of nationalities and technical interests. The year 2008's program emphasized gesture and activity recognition but also reported on power considerations, augmented reality, evaluation, and new interaction modalities, among other topics. 相似文献
106.
S.N. Al-Refaie H.S.B. Elayyan 《Science, Measurement & Technology, IET》2007,1(3):133-137
The dispersion of potassium niobate (KNbO3) ceramics is analysed using the multiple-arc approach. This has revealed a high frequency arc that is unattainable by the Cole-Cole single arc analysis. The temperature dependence of the new arc is derived through the spread parameter of the relaxation distribution and interpreted in terms of the ferroelectric property of the KNbO3 ceramics. It is shown that the overall dispersion behaviour of the ceramics is mainly due to the existence of two distinctly different polarisation mechanisms. The arc approach has also provided an effective tool for network simulation of dispersion whereby the ceramics are modelled by nine parallel R-C branches over the frequency range 102-105 Hz used 相似文献
107.
108.
A method is developed, based on word-searching, which provides a rapid test for the statistical significance of DNA sequence similarities for use in databank searching. The method makes allowance for the lengths and dinucleotide compositions of the sequences being compared. A way is also described to calculate the power of the test, i.e. the probability of detecting a given similarity as being statistically significant. The effects on the power of the test of the scoring method, word length, sequence length, and sequence composition are examined. A novel scoring method is shown to be superior to the method currently used in most word-searching algorithms. 相似文献
109.
110.
This article presents the development of a ceramic micro heat exchanger. Starting from its geometrical design, results obtained from a simplified simulation of the heat exchanger efficiency will be given. The alumina microcomponents were manufactured by a rapid prototyping process chain. Here, stereolithography was combined with a low‐pressure injection molding process for the rapid and precise manufacturing of ceramic components down to the micrometer range. A micro heat exchanger, joined from sintered components using a glass solder, was applied as a prototype and checked for its performance at a system pressure of 8 bar. 相似文献