全文获取类型
收费全文 | 290624篇 |
免费 | 3171篇 |
国内免费 | 832篇 |
专业分类
电工技术 | 5058篇 |
综合类 | 166篇 |
化学工业 | 46105篇 |
金属工艺 | 11988篇 |
机械仪表 | 8672篇 |
建筑科学 | 6920篇 |
矿业工程 | 1841篇 |
能源动力 | 6829篇 |
轻工业 | 26026篇 |
水利工程 | 3207篇 |
石油天然气 | 7097篇 |
武器工业 | 16篇 |
无线电 | 31714篇 |
一般工业技术 | 57566篇 |
冶金工业 | 51975篇 |
原子能技术 | 7556篇 |
自动化技术 | 21891篇 |
出版年
2021年 | 2158篇 |
2018年 | 3737篇 |
2017年 | 3677篇 |
2016年 | 3974篇 |
2015年 | 2515篇 |
2014年 | 4296篇 |
2013年 | 12195篇 |
2012年 | 6933篇 |
2011年 | 9350篇 |
2010年 | 7696篇 |
2009年 | 8793篇 |
2008年 | 9047篇 |
2007年 | 8928篇 |
2006年 | 7926篇 |
2005年 | 7396篇 |
2004年 | 6898篇 |
2003年 | 6634篇 |
2002年 | 6705篇 |
2001年 | 6568篇 |
2000年 | 6235篇 |
1999年 | 6297篇 |
1998年 | 14859篇 |
1997年 | 11096篇 |
1996年 | 8628篇 |
1995年 | 6567篇 |
1994年 | 5964篇 |
1993年 | 5842篇 |
1992年 | 4537篇 |
1991年 | 4488篇 |
1990年 | 4325篇 |
1989年 | 4351篇 |
1988年 | 4296篇 |
1987年 | 3624篇 |
1986年 | 3629篇 |
1985年 | 4201篇 |
1984年 | 4002篇 |
1983年 | 3655篇 |
1982年 | 3443篇 |
1981年 | 3583篇 |
1980年 | 3450篇 |
1979年 | 3378篇 |
1978年 | 3465篇 |
1977年 | 3948篇 |
1976年 | 5067篇 |
1975年 | 3172篇 |
1974年 | 3022篇 |
1973年 | 3044篇 |
1972年 | 2660篇 |
1971年 | 2483篇 |
1970年 | 2109篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
A chronological review and methodological critique of action research on redlining in 15 communities is presented. Redlining studies have been conducted or sponsored by three types of researchers: 1) non-profit neighborhood organizations, 2) academic or governmental institutions, and 3) lending institutions. Their findings vary according to the methods employed, and these methods vary according to the sponsors. Despite the methodological difficulties and inadequacies of this type of research, the findings have been used by local neighborhood organizations as a strategy to achieve constructive change in neighborhood reinvestment and revitalization. 相似文献
992.
993.
V. G. Vizing 《Cybernetics and Systems Analysis》1991,27(1):108-115
We consider extremum points of compact sets with a weak majorization relation. Examples of problems are presented for which these extremum points are optimal solutions.Translated from Kibernetika, No. 1, pp. 80–85, January–February, 1991. 相似文献
994.
Computers for symbolic processing 总被引:1,自引:0,他引:1
Wah B.W. Lowrie M.B. Li G.-J. 《Proceedings of the IEEE. Institute of Electrical and Electronics Engineers》1989,77(4):509-540
A detailed survey on the motivations, design, applications, current status, and limitations of computers designed for symbolic processing is provided. Symbolic processing computations are performed at the word, relation, or meaning levels, and the knowledge used in symbolic applications may be fuzzy, uncertain, indeterminate, and ill represented. Various techniques for knowledge representation and processing are discussed from both the designers' and users' points of view. The design and choice of a suitable language for symbolic processing and the mapping of applications into a software architecture are then considered. The process of refining the application requirements into hardware and software architectures is treated, and state-of-art sequential and parallel computers designed for symbolic processing are discussed 相似文献
995.
A.G. Youtsos 《Nuclear Engineering and Design》1989,114(1)
The effect of gaps present in the seismic supports of nuclear piping systems and of the flexibility of the steel structure to which intermediate supports are attached, is studied in this paper. An actual piping system is used to investigate the impact of structural steel and mechanical snubber gaps on the dynamic behaviour of piping. An evaluation is thus performed of the finite element modeling techniques employed by the designers in the dynamic analysis of piping systems. 相似文献
996.
997.
N S Sergeeva M Iu Vasil'ev T I Kovalenko N V Sokolova G I Avdeev 《Eksperimental?nai?a onkologii?a》1989,11(2):35-37
The indirect immunofluorescent technique was used to study the distribution of the ascitic fluid antigen (AgD) on histological sections from surgical specimens of gastric and colon tumours from proximal to distal lines of resection. AgD was found in gastric tumours exceptionally in the tumour area and in colon cancer--both in the tumour stroma and in surrounding histologically normal mucosa. 相似文献
998.
Transmit/receive modules 总被引:1,自引:0,他引:1
This paper begins with a discussion of the microwave functions performed by transmit/receive (T/R) modules for phased-array antenna applications. The paper then addresses performance and cost aspects of semiconductor, packaging, and assembly technologies associated with T/R modules 相似文献
999.
This article reports the results of a study conducted to examine the ability of the Situational Outlook Questionnaire (SOQTM) to effectively discern climates that either encourage or discourage creativity and the ability to initiate change in a team setting. The purpose of the study is to examine the concurrent criterion–related validity of the SOQ. The article explores the characteristics in an organisational climate that promote teamwork and some of the tripwires one needs to be aware of in the formation and management of teams. Nine dimensions of the climate for creativity and change as measured by the Situational Outlook Questionnaire are put forward and defined in relation to teams. The methodology and results of the study are reported. The results show that when subjects (N7equals;154) complete the SOQ based on their recollection of a best– and worst–case team experience, the measure is able to consistently and significantly discriminate between the two types of experiences. Conclusions, implications, and areas for future research to further examine the validity of the SOQ are explored. 相似文献
1000.