全文获取类型
收费全文 | 23099篇 |
免费 | 1245篇 |
国内免费 | 851篇 |
专业分类
电工技术 | 1106篇 |
综合类 | 1532篇 |
化学工业 | 2873篇 |
金属工艺 | 1010篇 |
机械仪表 | 1391篇 |
建筑科学 | 690篇 |
矿业工程 | 544篇 |
能源动力 | 657篇 |
轻工业 | 1924篇 |
水利工程 | 279篇 |
石油天然气 | 918篇 |
武器工业 | 120篇 |
无线电 | 3018篇 |
一般工业技术 | 1889篇 |
冶金工业 | 708篇 |
原子能技术 | 376篇 |
自动化技术 | 6160篇 |
出版年
2024年 | 32篇 |
2023年 | 227篇 |
2022年 | 384篇 |
2021年 | 421篇 |
2020年 | 433篇 |
2019年 | 422篇 |
2018年 | 366篇 |
2017年 | 548篇 |
2016年 | 577篇 |
2015年 | 662篇 |
2014年 | 1208篇 |
2013年 | 1255篇 |
2012年 | 1575篇 |
2011年 | 2013篇 |
2010年 | 1565篇 |
2009年 | 1739篇 |
2008年 | 1655篇 |
2007年 | 1785篇 |
2006年 | 1603篇 |
2005年 | 1211篇 |
2004年 | 982篇 |
2003年 | 871篇 |
2002年 | 658篇 |
2001年 | 527篇 |
2000年 | 503篇 |
1999年 | 316篇 |
1998年 | 223篇 |
1997年 | 184篇 |
1996年 | 152篇 |
1995年 | 143篇 |
1994年 | 161篇 |
1993年 | 118篇 |
1992年 | 82篇 |
1991年 | 77篇 |
1990年 | 62篇 |
1989年 | 64篇 |
1988年 | 36篇 |
1987年 | 33篇 |
1986年 | 32篇 |
1985年 | 31篇 |
1984年 | 26篇 |
1983年 | 19篇 |
1982年 | 33篇 |
1981年 | 31篇 |
1980年 | 75篇 |
1979年 | 17篇 |
1978年 | 7篇 |
1977年 | 12篇 |
1975年 | 8篇 |
1973年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
This essay examines a politically engaged research genre, which follows the biography of the author who founded two journals: one on mathematical models published in English (Quality and Quantity) and one on politically committed social and economic research published in Italian (Inchiesta). The research considered focuses on Italy in the 1950s, the research by Lazarsfeld in Vienna in the 1920s and in the United States in the 1950s and 1960s, and post-1968 politically committed research in Italy. The analysis of such politically committed types of research (all very different from one another in terms of the interpretative model of reality, the methods used and the relations with the tendering party and the people observed) allows one to understand how this kind of research can be performed with very different methods—all of which do, however, seek to modify reality on the grounds of the research results. The metaphor of the crystal and the flame presented by Italo Calvino in order to classify facts and ideas and styles and feelings can also be used to visualise the polarity (and the difficulty/impossibility of contact) that has always been present in sociology between two different tendencies: towards a discipline that offers the most abstract and objective interpretative model of reality possible with the use of mathematical models (the crystal), and, instead, towards a discipline in which an interpretative model of reality is central, one that produces a social change and in which the qualitative and quantitative methods utilised are at the service of this change (the flame). This polarity thus allows us to separate first and foremost all the politically committed research performed by others for different purposes (market research, research to verify some theoretical hypotheses, etc.) but the same polarity also lies within the politically committed research. We can, indeed, identify a type of politically committed research in an area that has, at one extreme, research tending towards the utmost objectivity and scientific quality of the results and where the co-ordinators try to have all the information on the subjects maintaining the greatest possible distance (the subjects must not know they are being observed); at the other extreme, there is a type of research in which the coordinator completely involves the subjects in the gathering of information that will serve to realise a piece of research whose political aims are explicitly shared. For the identification of a sufficiently articulated typology it has been important to consider five dimensions of politically committed research: (a) the characteristics of the research coordinator (his/her belonging to the type and the academic/non-academic professional status) and his/her interpretative model of reality (b) some general characteristics of the research (the tender and funding, the topic choice, the aims, the contributions to the sociological theory, the duration); (c) the research coordinators relations with the political actors (the intensity of the relations, the political use of the research); (d) the relations of the research co-ordinator with the research subjects; (e) the methodological choices (the basic strategies, the methods used, the use of mathematical procedures). The research that exemplifies this typology is all politically committed to the left and was realised in different times and contexts. I start by considering a kind of politically engaged research (co-research) that appeared in Italy in the 1950s; I then analyse two types of politically engaged research realised in Austria at the end of the 1920s and one in the United States in the 1950s; there then follow two kinds of research realised in the 1960s and 1970s in the United States and a further two kinds realised in Italy in the 1970s and early 1980s. In order to have other kinds of research please refer to the two Journals of which I am the editor: one is an English language journal of mathematical models (Quality and Quantity, International Journal of Methodology, founded in 1966 and published today by Kluwer of Amsterdam), and a politically engaged review (Inchiesta, founded in 1971 and still published today by Dedalo of Bari). 相似文献
72.
73.
结合嵌入式实时操作系统VxWorks实现某测控系统的实际应用,以其中的TCP通信为例,讨论了在VxWorks下实现C/S通信的关键技术。 相似文献
74.
该仪器是基于89C52的单片机系统,采用12位AD574A转换器,针对现有风压测量仪器功能上的不足,实现了实时送显和平均送显功能,满足了测量风压时不同情况下的使用要求,尤其适用于风机系统管道内各种压力参数的测量.系统设计了RS232通讯接口,为进一步开发风机性能测试系统奠定了基础. 相似文献
75.
针对现有服装销售管理的现状及信息化需求,研究了基于B/S结构的服装销售管理系统,并利用asp加以实现。通过三层结构实现了系统的原型设计,介绍了基于B/S结构的服装销售管理系统的体系结构、功能及系统实现的关键技术。 相似文献
76.
介绍了一种基于AT89C2051单片机为核心的晶闸管触发电路,并详细阐述了其软硬件结构,具有高集成度、智能化、体积小、安全、迅速、可靠稳定等优点,今后必将被广泛应用。 相似文献
77.
设计了家庭智能浇花器,实现花卉的自动浇水.利用单片机实现自动浇花,根据不同的花种,设置了不同的控制方式,即定时定量浇花方式与根据湿度浇花.定时定量浇花是实现每天在规定的时间自动打开电磁阀浇花,根据不同的花卉所需水量不同,用一个按钮来设置浇花时间的长短,即电磁阀打开的时间,其余时间电磁阀闭合,水流不经过;根据湿度控制浇花... 相似文献
78.
本文以历年《中国体育事业统计年鉴》中的积累数据为研究对象,通过对各类统计数据表的分析,运用数据库技术和软件工程方法,确定表的结构,建立年鉴数据库;研究运用c#语言设计开发基于网络的c/s模式前端客户端,对数据库进行添加、删除、修改、查询、导出等相关操作,实现对《中国体育事业统计年鉴》数据的网络化管理。 相似文献
79.
介绍S5-135U PLC在大板堆垛系统技改项目中的应用,阐述I/O远程扩展、软件编程应数据通信等方面的设计。 相似文献
80.
目的分析某天然气净化厂康索夫(Cansolv)尾气处理装置烟气加热器出现严重腐蚀失效的原因。 方法分析了烟气加热器管束的腐蚀环境,开展了材料理化性能、腐蚀产物成分及微观形貌等失效原因分析。 结果失效管束的理化性能符合要求,管束泄漏处呈坑状和蜂窝状,部分沟槽尖端有裂纹,且深入基体,呈现应力腐蚀的特征。 结论烟气加热器在高温、高酸液含量的环境下发生了电化学腐蚀和应力腐蚀,导致管束出现腐蚀泄漏。 相似文献