全文获取类型
收费全文 | 18764篇 |
免费 | 2116篇 |
国内免费 | 972篇 |
专业分类
电工技术 | 627篇 |
技术理论 | 1篇 |
综合类 | 1868篇 |
化学工业 | 1725篇 |
金属工艺 | 745篇 |
机械仪表 | 664篇 |
建筑科学 | 3907篇 |
矿业工程 | 1334篇 |
能源动力 | 1619篇 |
轻工业 | 1077篇 |
水利工程 | 1880篇 |
石油天然气 | 414篇 |
武器工业 | 106篇 |
无线电 | 799篇 |
一般工业技术 | 1383篇 |
冶金工业 | 1281篇 |
原子能技术 | 90篇 |
自动化技术 | 2332篇 |
出版年
2024年 | 102篇 |
2023年 | 304篇 |
2022年 | 596篇 |
2021年 | 660篇 |
2020年 | 791篇 |
2019年 | 638篇 |
2018年 | 543篇 |
2017年 | 637篇 |
2016年 | 794篇 |
2015年 | 804篇 |
2014年 | 1127篇 |
2013年 | 1267篇 |
2012年 | 1234篇 |
2011年 | 1555篇 |
2010年 | 1192篇 |
2009年 | 1178篇 |
2008年 | 1124篇 |
2007年 | 1281篇 |
2006年 | 1123篇 |
2005年 | 899篇 |
2004年 | 728篇 |
2003年 | 639篇 |
2002年 | 516篇 |
2001年 | 407篇 |
2000年 | 304篇 |
1999年 | 257篇 |
1998年 | 193篇 |
1997年 | 149篇 |
1996年 | 129篇 |
1995年 | 110篇 |
1994年 | 109篇 |
1993年 | 61篇 |
1992年 | 62篇 |
1991年 | 42篇 |
1990年 | 34篇 |
1989年 | 33篇 |
1988年 | 25篇 |
1987年 | 17篇 |
1986年 | 28篇 |
1985年 | 12篇 |
1984年 | 14篇 |
1983年 | 8篇 |
1982年 | 11篇 |
1964年 | 10篇 |
1961年 | 8篇 |
1960年 | 6篇 |
1959年 | 6篇 |
1957年 | 12篇 |
1955年 | 6篇 |
1951年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
72.
73.
全文围绕树立和落实科学发展观这一主题 ,研究和探索如何在新时期、新阶段进一步做好国土资源管理工作的新思路、新途径和新方法。提出要进一步加强国土资源宏观管理 ,更好地为甘肃省经济社会的协调、可持续发展提供保障服务。 相似文献
74.
75.
The fabrication of functional textiles able to provide thermal regulation and comfort for the body has attracted increasing interest in recent years. This research investigated fabric coatings containing energy absorbing, temperature stabilizing, phase‐change material microcapsules (PCMMcs), and their methods of application. Specifically, a coated fabric was directly prepared by a dual‐type coating method, in which the PCMMcs were dispersed in a polyurethane coating solution with no binder. The thermal performances of the dual‐coated samples were evaluated by differential scanning calorimetry, and their physical characteristics were examined by scanning electron microscopy, thermal vision camera, porosity, water vapor transmission rate (WVTR), and water entry pressure (WEP) analyses. Furthermore, the microclimate characteristics of the thermally enhanced fabrics were investigated under experimental conditions using a human‐clothing‐environment (HCE) simulator system. The study results confirmed the superior performance of the dual‐coated fabrics in terms of thermal regulation and body comfort, compared with those coated by the dry or wet coating method, because of the improved WEP, WVTR, and thermal performance. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
76.
77.
As cropland and pasture have replaced forest and cerrado in Brazilian Amazônia, concern has mounted over the effects of changing the biogeochemical and hydrological properties of one of the world's great storehouses of biomass and biodiversity. Although much recent effort has focused on the location, effects, and causes of deforestation and cerrado conversion, much less is known about the basin-wide spatial distribution and density of the land use following conversion for crops or pasture.In this paper, we use census and satellite records to develop maps of the distribution and abundance of major agricultural land uses across 4.5×108 ha of Brazilian Amazônia in 1980 and 1995. Results indicate an overall expansion of 7.0×106 ha in total agricultural area in Brazilian Amazônia between 1980 and 1995. The net change during this period is estimated for three different land-use types: croplands (an increase of 0.8×106 ha), natural pastures (a decrease of 8.4×106 ha), and planted pastures (an increase of 14.7×106 ha). These estimates, the first spatially explicit quantifications of agricultural land-use activities in 1980 and 1995 across Brazilian Amazônia, are shown to be consistent with the results of applying a land use change and secondary regrowth model to published deforestation rates for the period.The resulting time slices, presented for each land-use category at 5-min (∼9 km) spatial resolution, allow for the quantification of land-use changes in this region for biogeochemical, demographic and economic models. Several foci of agricultural change existed within Brazilian Amazônia during this period: in the state of Pará, cropland was lost and planted pasture increased markedly; in Mato Grosso, both cropland and planted pasture increased; in Rondônia, planted pasture replacing forest was the primary route to agricultural expansion. 相似文献
78.
中国城市土地利用结构优化研究述评 总被引:9,自引:0,他引:9
城市土地利用结构的确定和优化是城市总体规划的核心内容,从土地使用制度变迁,学科交叉,数理模型方法三方面回顾了中国城市土地利用结构优化研究的发展历程,分析了中国城市土地利用结构优化研究的新气象。在此基础上,指出当前研究工作的不足和问题,并提出未来研究的方向。 相似文献
79.
略谈政府垄断土地一级市场的问题和对策 总被引:1,自引:0,他引:1
政府垄断土地一级市场要强化对土地市场的监管、规范和垄断 ;完善土地市场机制 ,发挥市场配置土地资源的基础性作用 相似文献
80.
以加入世贸组织为契机 ,加强资源战略研究 ,抓好管理重点 ,为“工业强省”提供国土资源支持。规范市场 ,处理好 5种关系 ,全面清理法规、规章、政策 ,转变政府职能 相似文献