全文获取类型
收费全文 | 20127篇 |
免费 | 2120篇 |
国内免费 | 1526篇 |
专业分类
电工技术 | 772篇 |
技术理论 | 7篇 |
综合类 | 2605篇 |
化学工业 | 1896篇 |
金属工艺 | 208篇 |
机械仪表 | 613篇 |
建筑科学 | 1925篇 |
矿业工程 | 2320篇 |
能源动力 | 696篇 |
轻工业 | 1082篇 |
水利工程 | 4218篇 |
石油天然气 | 405篇 |
武器工业 | 69篇 |
无线电 | 950篇 |
一般工业技术 | 1017篇 |
冶金工业 | 1586篇 |
原子能技术 | 127篇 |
自动化技术 | 3277篇 |
出版年
2024年 | 99篇 |
2023年 | 284篇 |
2022年 | 742篇 |
2021年 | 852篇 |
2020年 | 640篇 |
2019年 | 543篇 |
2018年 | 541篇 |
2017年 | 627篇 |
2016年 | 680篇 |
2015年 | 787篇 |
2014年 | 1257篇 |
2013年 | 1216篇 |
2012年 | 1368篇 |
2011年 | 1438篇 |
2010年 | 1263篇 |
2009年 | 1139篇 |
2008年 | 1153篇 |
2007年 | 1522篇 |
2006年 | 1454篇 |
2005年 | 1230篇 |
2004年 | 943篇 |
2003年 | 853篇 |
2002年 | 639篇 |
2001年 | 512篇 |
2000年 | 403篇 |
1999年 | 287篇 |
1998年 | 204篇 |
1997年 | 154篇 |
1996年 | 124篇 |
1995年 | 100篇 |
1994年 | 90篇 |
1993年 | 69篇 |
1992年 | 54篇 |
1991年 | 46篇 |
1990年 | 41篇 |
1989年 | 34篇 |
1988年 | 25篇 |
1987年 | 21篇 |
1986年 | 29篇 |
1985年 | 28篇 |
1984年 | 24篇 |
1983年 | 28篇 |
1982年 | 16篇 |
1981年 | 18篇 |
1964年 | 13篇 |
1960年 | 10篇 |
1959年 | 10篇 |
1957年 | 17篇 |
1956年 | 11篇 |
1955年 | 23篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
随着工农业发展和人口的增长,南流江流域水资源供需矛盾日益突出,水资源的可持续利用日益显得重要,针对流域水资源特点,提出加强水资源统一管理,实施跨流域调水,加强水资源保护等对策。 相似文献
92.
The tendencies characterizing worsening of natural, mining and technical, as well as mining and geological conditions of deposit mining are analyzed for the last 100 years. The change in prices for mineral raw material is shown, and the influence exerted by scientific and technical progress in the sphere of mining and processing of copper-containing ores is established. An approach to the estimate of available mineral reserves and possibility of their involvement in mining is stated. 相似文献
93.
94.
国际水资源保护和管理的最近动态——水与可持续发展 总被引:9,自引:1,他引:8
阐述了可持续发展及其要求 ,水在可持续发展中的作用 ,国际关于水资源保护和管理的最近动态。最后提出 ,可持续发展是经济社会以及人口、资源和环境的协调统一 ,应从根本上将“先污染后治理”及“防治污染”改为“避免污染”的战略 ;从传统的整体规划向机能整体性规划发展 ;保护和建立河流系统环境 ;着手研究和解决全球环境问题。 相似文献
95.
油气资源勘探开发的经济边际分析是从石油企业的边际利润出发,确定石油企业的最优投入产出水平,为作出科学的投资决策和生产决策提供依据,界定了有关油气资源勘探开发经济边际的概念和内涵,探讨了石油企业边际成本和边际收入的确定方法。 相似文献
96.
P. Powell 《Information Systems Journal》1992,2(4):269-280
Abstract. Expert systems proliferate. They are now a usable and used tool in a variety of organizations. However, little research has been undertaken on the quantification of success or failure of expert system projects. By and large the only test carried out for expert system validation is one of comparison of the conclusions of the system with those of an expert or team of experts. While questioning the validity, this paper accepts that this method is being used and analyses whether or not the results obtained from this type of test should be a surprise. That is, what sort of results should be expected and to what extent do the reported ones live up to these expectations? Earlier research from the field of human information processing casts doubts on the success claims made for current expert systems. The implications of this research are then analysed in order to explore the possible redeeming features of expert systems which are not taken into account in such comparisons. The use of linear models as comparators for expert systems may prove beneficial. 相似文献
97.
对天津及其滨海新区生态城市水利建设进行了分析。研究了在淡水资源极度匮乏的条件下,有效开发利用非常规水资源的必要性、重要性和现实性。认为天津市对水资源应遵循节水、治污、高效配置,妥善处理生活、生产、生态之间的关系,力求平衡调配。供水水源应是多元的,增加非常规水资源(污水、海/咸水、雨/洪水)的利用,同时增加可用地下水,外调来水等,逐步进入可持续发展配置。 相似文献
98.
99.
Reviews the book, The mind's we: Contextualism in cognitive psychology by Diane Gillespie (1992). In this text the author has both expanded on several of the key insights previously outlined in the critical literature and provided a congenial introductory text for the newcomer; a text to serve as a conceptual bridge between traditional cognitive psychological approaches and their newly emergent contextualist alternatives. As stated in her preface, Gillespie's purpose in preparing this book was to "bring together the work of psychologists who are interested in telling the contextualist story of cognition" and to "reveal and strengthen their insights and perspectives" (p. xiv). Given the philosophical range and theoretical diversity of those interested in telling such a story, the task is certainly a formidable one, but it is nonetheless one that she accomplishes with a commendable degree of elegance. Gillespie clearly articulates the diverse work of a large number of psychological theorists into a coherent and meaningful account that will do much toward imposing order on a field that is, by its very nature, somewhat scattered and contentious. Each of the book's six chapters proceeds carefully through a detailed and representative historical and conceptual analysis of traditional mechanistic approaches to human cognition prior to advancing their contextualist critiques and alternatives. Through a systematic analysis of the manner in which this "contextualist story" has arisen within the mechanistic milieu of traditional scientific psychology, she is able to clarify both the implications and relative merits and liabilities of two, quite often antithetical, conceptualizations of human cognitive phenomena. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
100.