全文获取类型
收费全文 | 37888篇 |
免费 | 3954篇 |
国内免费 | 1651篇 |
专业分类
电工技术 | 2253篇 |
技术理论 | 13篇 |
综合类 | 4215篇 |
化学工业 | 2206篇 |
金属工艺 | 513篇 |
机械仪表 | 865篇 |
建筑科学 | 13790篇 |
矿业工程 | 2852篇 |
能源动力 | 1018篇 |
轻工业 | 855篇 |
水利工程 | 3006篇 |
石油天然气 | 3722篇 |
武器工业 | 184篇 |
无线电 | 1978篇 |
一般工业技术 | 1477篇 |
冶金工业 | 1251篇 |
原子能技术 | 191篇 |
自动化技术 | 3104篇 |
出版年
2024年 | 180篇 |
2023年 | 544篇 |
2022年 | 1115篇 |
2021年 | 1283篇 |
2020年 | 1391篇 |
2019年 | 1144篇 |
2018年 | 957篇 |
2017年 | 1355篇 |
2016年 | 1379篇 |
2015年 | 1406篇 |
2014年 | 2771篇 |
2013年 | 2390篇 |
2012年 | 2809篇 |
2011年 | 3050篇 |
2010年 | 2469篇 |
2009年 | 2299篇 |
2008年 | 2290篇 |
2007年 | 2480篇 |
2006年 | 2338篇 |
2005年 | 1901篇 |
2004年 | 1504篇 |
2003年 | 1339篇 |
2002年 | 1132篇 |
2001年 | 948篇 |
2000年 | 706篇 |
1999年 | 491篇 |
1998年 | 348篇 |
1997年 | 273篇 |
1996年 | 193篇 |
1995年 | 205篇 |
1994年 | 155篇 |
1993年 | 121篇 |
1992年 | 116篇 |
1991年 | 66篇 |
1990年 | 64篇 |
1989年 | 48篇 |
1988年 | 38篇 |
1987年 | 17篇 |
1986年 | 30篇 |
1985年 | 28篇 |
1984年 | 19篇 |
1983年 | 19篇 |
1982年 | 16篇 |
1981年 | 24篇 |
1980年 | 9篇 |
1979年 | 5篇 |
1964年 | 3篇 |
1960年 | 2篇 |
1959年 | 3篇 |
1956年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
首先简单叙述了C3I系统在军事上的应用,然后针对我国各类大中型城市的交通现状及特点,涉及到城市交通管理、道路管理、车辆管理和城市交通管理指挥中心站、区域指挥站及各交叉路口控制站,提出将C3I系统体系结构运用到民用城市交通管理中去的构想。 相似文献
62.
Three-dimensional (3-D) cell morphology is important for the understanding of cell function and can by quantified in terms of volume and surface area. Differential interference contrast (DIC, or Nomarski) imaging can enable cell edges to be clearly visualized in unstained tissue due to the slight difference in refractive index between aqueous media and cytoplasm. DIC is affected in only one direction - the direction of the optical shear. A 1-D edge detector was used in that direction with a scale length equal to that of an in-focus edge to highlight cell boundaries. By comparison with the signal from the edge detector on an out-of-focus slice, the in-focus slices could be segmented and, after noise suppression, cell outlines obtained. A voxel paradigm was used to calculate cell volume and differential geometry was used for surface area estimation. We applied this approach to obtain 3-D dimensional information by optical sectioning of motile Amoeba proteus. 相似文献
63.
64.
During the day, there are considerable variations in the climatic factors prevailing in these regions. This is especially so during the 24-hour daily cycle of the long, hot and dry summer (mid-May to midOctober). Such climatic conditions have had a considerable impact on the daily living pattern of family life in the same season, particularly in the urban areas. During the same 24-hour cycle, they have compelled the inhabitants to shift their living activities both vertically in section and horizontally in plan; they do this in pursuit of more acceptable, if not, desirable internal thermal environmental ambience. 相似文献
65.
66.
This article is the second of two papers that review the field of spatially sensitive social scientific research into the links between social status and transport disadvantage. The first paper undertook a comprehensive review of the social scientific and transport planning literature to mark the level of development in the field and identify conceptual and methodological issues and constraints in this field of inquiry. The present article supports the advancement of socially and geographically sensitive transport research by opportunities for the development of more sophisticated spatial analytical methodologies. The approach we present is able to account for factors not previously addressed in either social or transport planning research, in particular the temporal dimensions of transport service accessibility. The article articulates the methodology through an empirical case study of socio-spatial transport disadvantage within the Gold Coast City. The article demonstrates that there are important theoretical and practical lessons to be gained for researchers and policy makers in addressing the social dimensions of transport and infrastructure provision. Further, the article argues that an attentiveness to new ways of combining and representing social and transport data-sets can promote policy relevant empirical social inquiry. The article also contributes in a productive way to the empirical knowledge of Australia's sixth-largest metropolitan area, which is often overlooked by urban scholars. 相似文献
67.
珠江口盆地惠州地区中新统地层岩性圈闭形成条件分析 总被引:7,自引:0,他引:7
区域地质背景反映珠江口盆地惠州地区中新统具有形成地层岩性圈闭的条件。研究惠州地区地层岩性圈闭的形成条件、控制因素和分布规律,对于该区油气勘探持续发展有重要意义。建立了惠州地区中新统高精度的层序地层格架,在此基础上分析不同类型层序的构型特点,研究不同类型坡折带的形成机制、分布范围及对沉积体系的控制作用。层序地层边界和坡折带是控制本区地层岩性圈闭形成的重要因素。惠州地区存在3种具有勘探前景的地层岩性圈闭,选择HZ27-3低位体钻探获得成功。 相似文献
68.
Qingyuan Hu 《Carbon》2006,44(7):1349-1352
69.
本文通过工程实例分析了山区建筑的结构设计特点,并提出了结构设计中应注意的问题。 相似文献
70.