全文获取类型
收费全文 | 2108篇 |
免费 | 247篇 |
国内免费 | 159篇 |
专业分类
电工技术 | 202篇 |
综合类 | 192篇 |
化学工业 | 179篇 |
金属工艺 | 159篇 |
机械仪表 | 83篇 |
建筑科学 | 68篇 |
矿业工程 | 24篇 |
能源动力 | 265篇 |
轻工业 | 25篇 |
水利工程 | 8篇 |
石油天然气 | 15篇 |
武器工业 | 9篇 |
无线电 | 475篇 |
一般工业技术 | 505篇 |
冶金工业 | 61篇 |
原子能技术 | 15篇 |
自动化技术 | 229篇 |
出版年
2024年 | 10篇 |
2023年 | 87篇 |
2022年 | 87篇 |
2021年 | 99篇 |
2020年 | 125篇 |
2019年 | 95篇 |
2018年 | 66篇 |
2017年 | 77篇 |
2016年 | 100篇 |
2015年 | 97篇 |
2014年 | 99篇 |
2013年 | 122篇 |
2012年 | 125篇 |
2011年 | 156篇 |
2010年 | 120篇 |
2009年 | 164篇 |
2008年 | 110篇 |
2007年 | 122篇 |
2006年 | 113篇 |
2005年 | 91篇 |
2004年 | 98篇 |
2003年 | 69篇 |
2002年 | 63篇 |
2001年 | 42篇 |
2000年 | 34篇 |
1999年 | 24篇 |
1998年 | 21篇 |
1997年 | 14篇 |
1996年 | 14篇 |
1995年 | 15篇 |
1994年 | 10篇 |
1993年 | 8篇 |
1992年 | 3篇 |
1991年 | 5篇 |
1990年 | 6篇 |
1989年 | 5篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1983年 | 3篇 |
1982年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1976年 | 1篇 |
1959年 | 1篇 |
排序方式: 共有2514条查询结果,搜索用时 15 毫秒
1.
Thin Film Thermoelectric Metal–Organic Framework with High Seebeck Coefficient and Low Thermal Conductivity
下载免费PDF全文
![点击此处可从《Advanced materials (Deerfield Beach, Fla.)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
2.
This paper proposes a thermoelectric-assisted vapor compression cycle (TVCC) for applications in air-source heat pump systems which could enhance the heating capacity of the system. Performances of TVCC are calculated and then compared with that of basic vapor compression cycle (BVCC). The simulation results show that when coefficients of performance (COPs) of the two cycles are almost equal, the TVCC under maximum COP condition of the thermoelectric modules still performs better than BVCC by 13.0% in heating capacity through selecting the appropriate intermediate temperature. In addition, the TVCC can also achieve an improvement of 16.4%–21.7% in both the heating COP and capacity when compared with the BVCC with an assistant electric heater that is provided with the equivalent power input of thermoelectric heat exchanger. Thus, the TVCC could be beneficial to the applications in small heat pumps if there is always need for auxiliary electric heat. 相似文献
3.
We present a two-sorted algebra, called aPeirce algebra, of relations and sets interacting with each other. In a Peirce algebra, sets can combine with each other as in a Boolean algebra, relations can combine with each other as in a relation algebra, and in addition we have both a set-forming operator on relations (the Peirce product of Boolean modules) and a relation-forming operator on sets (a cylindrification operation). Two applications of Peirce algebras are given. The first points out that Peirce algebras provide a natural algebraic framework for modelling certain programming constructs. The second shows that the so-calledterminological logics arising in knowledge representation have evolved a semantics best described as a calculus of relations interacting with sets. 相似文献
4.
Mg-Si基热电化合物的研究现状 总被引:1,自引:0,他引:1
重点综述了Mg-Si基热电化合物的基本特性,该体系热电材料的制备方法与掺杂改性的研究进展,并提出了要重点解决的问题。 相似文献
5.
6.
7.
A new principle and arrangement for directly determining the angle of incidence of an optical beam on an object are proposed and demonstrated. The novelty of the approach lies in the realization of a ‘smart object’, which extracts a portion of the incident beam's power into an optical waveguide attached to the object's surface or embedded in its body for converting the angle of incidence into the position of a guided beam with finite lateral extent. This ‘integrated optical light pointer’ beam is accomplished by means of creating additional degrees of freedom on the target in two different ways. While a first type is based on introducing spatial variations of the waveguide thickness, a second type makes use of a chirp of the grating periodicity. The feasibility for practical applications has been experimentally demonstrated by a direct comparison with a commercial high-resolution encoder, resulting in an r.m.s. error of <30′'. Measurements have been performed for chips fabricated based on replicated polycarbonate substrates and with no external optics, showing the great potential of this approach for realizing low-cost yet high-performance miniature goniometers. 相似文献
8.
9.
We consider an extension of the functional programming language Standard ML with a modular structure based upon concepts in category theory such as categories, functors, natural transformations and adjunctions. In essence, we are following the categorical imperative of considering arrows as well as objects. This is intended to enforce a certain mathematical rigour on the programmer, so that the only programs that can be expressed are those with a categorical significance. The essentially algebraic nature of category theory means that we may generate equational correctness conditions for the modular structure of programs, thus separating the correctness of individual functions from that of modules. We describe this programming language, give examples of its use, and explain how it is implemented in a type system. 相似文献
10.