全文获取类型
收费全文 | 83575篇 |
免费 | 957篇 |
国内免费 | 406篇 |
专业分类
电工技术 | 771篇 |
综合类 | 2316篇 |
化学工业 | 11393篇 |
金属工艺 | 4784篇 |
机械仪表 | 3013篇 |
建筑科学 | 2152篇 |
矿业工程 | 562篇 |
能源动力 | 1100篇 |
轻工业 | 3571篇 |
水利工程 | 1266篇 |
石油天然气 | 344篇 |
无线电 | 9233篇 |
一般工业技术 | 16261篇 |
冶金工业 | 2621篇 |
原子能技术 | 253篇 |
自动化技术 | 25298篇 |
出版年
2020年 | 7篇 |
2019年 | 11篇 |
2018年 | 14455篇 |
2017年 | 13380篇 |
2016年 | 9968篇 |
2015年 | 604篇 |
2014年 | 230篇 |
2013年 | 185篇 |
2012年 | 3131篇 |
2011年 | 9394篇 |
2010年 | 8272篇 |
2009年 | 5540篇 |
2008年 | 6762篇 |
2007年 | 7766篇 |
2006年 | 106篇 |
2005年 | 1201篇 |
2004年 | 1121篇 |
2003年 | 1165篇 |
2002年 | 531篇 |
2001年 | 94篇 |
2000年 | 174篇 |
1999年 | 54篇 |
1998年 | 49篇 |
1997年 | 26篇 |
1996年 | 43篇 |
1995年 | 8篇 |
1994年 | 11篇 |
1993年 | 8篇 |
1992年 | 11篇 |
1991年 | 22篇 |
1988年 | 9篇 |
1969年 | 24篇 |
1968年 | 43篇 |
1967年 | 33篇 |
1966年 | 42篇 |
1965年 | 44篇 |
1964年 | 11篇 |
1963年 | 28篇 |
1962年 | 22篇 |
1961年 | 18篇 |
1960年 | 30篇 |
1959年 | 35篇 |
1958年 | 37篇 |
1957年 | 36篇 |
1956年 | 34篇 |
1955年 | 63篇 |
1954年 | 68篇 |
1952年 | 6篇 |
1950年 | 6篇 |
1949年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
141.
142.
We present some sufficient and necessary conditions for convergent splitting of a non-Hermitian indefinite matrix. Some sufficient
conditions to determinate a matrix with a (strongly) dominant symmetric part for a class of boundary value problem are also
obtained. These results are applicable to identify the convergence of iterative methods for solving large sparse systems of
linear equations. 相似文献
143.
Keng Siau 《Requirements Engineering》2007,12(4):199-201
144.
145.
Phase-change read-and-write memory (PRAM) is a promising memory that can solve the problems of conventional memory—scalability, read/write speed, and reliability. We will review the opportunities and technical challenges of PRAM. The most important challenge of PRAM is the reduction of the writing current. Various approaches to reduce the writing current will be reviewed and the prospects of PRAM are discussed. 相似文献
146.
147.
Feature-based classifiers for design optimization 总被引:1,自引:0,他引:1
We present a design optimization method for systems with high-dimensional parameter spaces using inductive decision trees.
The essential idea is to map designs into a relatively low-dimensional feature space, and to derive a classifier to search
for high-performing design alternatives within this space. Unlike learning classifier systems that were pioneered by Holland
and Goldberg, classifiers defined by inductive decision trees were not originally developed for design optimization. In this
paper, we explore modifications to such classifiers to make them more effective in the optimization problem. We expand the
notions of feature space, generalize the tree construction heuristic beyond the original information-theoretic definitions,
increase the reliance on domain expertise, and facilitate the transfer of design knowledge between related systems. There
is a relatively small but rapidly growing body of work in the use of inductive trees for engineering design; the method presented
herein is complementary to this research effort. 相似文献
148.
Sebastián Bruque-Cámara Alfonso Vargas-Sánchez M. Jesús Hernández-Ortiz 《欧洲信息系统杂志》2004,13(2):133-146
The aim of this paper is to propose new organizational factors that might explain the differences in the extent and the speed of IT adoption. With this in mind, we carried out an analysis of 16 cases in the pharmaceutical distribution sector in Spain. The results indicate that there are certain intangible assets that favour the introduction and development of IT. Among these are a frank and fluid communication between departments and members of the organization, low levels of conflict, the explicit support of top management towards IT adoption and learning and creative skills of IT-staff. In addition to these factors, we found others that we propose as catalysts of IT adoption. Among these we might mention the special relationship between the member-clients and the company in the case of cooperative firms. 相似文献
149.
150.