全文获取类型
收费全文 | 162134篇 |
免费 | 9204篇 |
国内免费 | 4911篇 |
专业分类
电工技术 | 7118篇 |
技术理论 | 2篇 |
综合类 | 8263篇 |
化学工业 | 23019篇 |
金属工艺 | 9699篇 |
机械仪表 | 8442篇 |
建筑科学 | 7675篇 |
矿业工程 | 2746篇 |
能源动力 | 3723篇 |
轻工业 | 9000篇 |
水利工程 | 3156篇 |
石油天然气 | 3753篇 |
武器工业 | 1014篇 |
无线电 | 19160篇 |
一般工业技术 | 25207篇 |
冶金工业 | 6190篇 |
原子能技术 | 1254篇 |
自动化技术 | 36828篇 |
出版年
2024年 | 232篇 |
2023年 | 920篇 |
2022年 | 1888篇 |
2021年 | 2938篇 |
2020年 | 2161篇 |
2019年 | 1796篇 |
2018年 | 16216篇 |
2017年 | 15540篇 |
2016年 | 12189篇 |
2015年 | 3801篇 |
2014年 | 4438篇 |
2013年 | 5145篇 |
2012年 | 9309篇 |
2011年 | 15801篇 |
2010年 | 14236篇 |
2009年 | 11340篇 |
2008年 | 12442篇 |
2007年 | 12998篇 |
2006年 | 5042篇 |
2005年 | 5252篇 |
2004年 | 4303篇 |
2003年 | 4110篇 |
2002年 | 3618篇 |
2001年 | 2783篇 |
2000年 | 1854篇 |
1999年 | 1302篇 |
1998年 | 858篇 |
1997年 | 699篇 |
1996年 | 557篇 |
1995年 | 431篇 |
1994年 | 338篇 |
1993年 | 241篇 |
1992年 | 181篇 |
1991年 | 154篇 |
1990年 | 122篇 |
1989年 | 92篇 |
1988年 | 59篇 |
1987年 | 56篇 |
1986年 | 42篇 |
1968年 | 44篇 |
1967年 | 33篇 |
1966年 | 42篇 |
1965年 | 45篇 |
1960年 | 30篇 |
1959年 | 40篇 |
1958年 | 37篇 |
1957年 | 36篇 |
1956年 | 34篇 |
1955年 | 63篇 |
1954年 | 68篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
41.
42.
Functional expression and synergistic cooperation of xylan‐degrading enzymes from Hypocrea orientalis and Aspergillus niger 下载免费PDF全文
43.
Variations of Incomplete Open Cubes is the major project by the twentieth-century conceptual artist Sol LeWitt. In this paper we interpret the enumerative component of the project as embeddings of graphs. This formulation permits use of an algorithm to check the completeness of the list of the structures produced by the artist. Our conclusion is that the artist found the correct number of structures (that is, 122), but that his list contains a mistake in the presentation of a pair of incomplete cubes, a discovery that appears not to have been noted before. 相似文献
44.
45.
Yong Pan Chen Zhu Wen Bin Zeng Pei Fu Chi Chen Bao Ming Xu Zhong Feng Gao 《Chembiochem : a European journal of chemical biology》2021,22(24):3431-3436
Rapid and sensitive point-of-care testing (POCT) is an extremely critical mission in practical applications, especially for rigorous military medicine, home health care, and in the third world. Here, we report a visual POCT method for adenosine triphosphate (ATP) detection based on Taylor rising in the corner of quadratic geometries between two rod surfaces. We discuss the principle of Taylor rising, demonstrating that it is significantly influenced by contact angle, surface tension, and density of the sample, which are controlled by ATP-dependent rolling circle amplification (RCA). In the presence of ATP, RCA reaction effectively suppresses Taylor-rising behavior, due to the increased contact angle, density, and decreased surface tension. Without addition of ATP, untriggered RCA reaction is favorable for Taylor rising, resulting in a significant height. With this proposed method, visual sensitive detection of ATP without the aid of other instruments is realized with only a 5 μL droplet, which has good selectivity and a low detection limit (17 nM). Importantly, this visual method provides a promising POCT tool for user-friendly molecular diagnostics. 相似文献
46.
测向误差的减小一直以来都是无线电测向精度提高的一个难点,对于不同的测向体制所采用的减小测向误差的方法都不尽相同。本文主要介绍的是相关干涉仪测向体制的基本原理以及通过内插法的应用来减小测向误差的方法。 相似文献
47.
48.
49.
50.
Understanding semantic word shifts in scientific domains is essential for facilitating interdisciplinary communication. Using a data set of published papers in the field of information retrieval (IR), this paper studies the semantic shifts of words in IR based on mining per-word topic distribution over time. We propose that semantic word shifts not only occur over time, but also over topics. The shifts are examined from two perspectives, the topic-level and the context-level. According to the over-time word-topic distribution, stable words and unstable words are recognized. The diverging and converging trends in the unstable type reveal characteristics of the topic evolution process. The context-level shifts are further detected by similarities between word vectors. Our work associates semantic word shifts with the evolving of topics, which facilitates a better understanding of semantic word shifts from both topics and contexts. 相似文献