全文获取类型
收费全文 | 63780篇 |
免费 | 5431篇 |
国内免费 | 1984篇 |
专业分类
电工技术 | 4556篇 |
技术理论 | 6篇 |
综合类 | 4221篇 |
化学工业 | 9450篇 |
金属工艺 | 3740篇 |
机械仪表 | 3701篇 |
建筑科学 | 5266篇 |
矿业工程 | 1592篇 |
能源动力 | 1949篇 |
轻工业 | 3994篇 |
水利工程 | 1091篇 |
石油天然气 | 3216篇 |
武器工业 | 502篇 |
无线电 | 7858篇 |
一般工业技术 | 7945篇 |
冶金工业 | 2588篇 |
原子能技术 | 839篇 |
自动化技术 | 8681篇 |
出版年
2025年 | 235篇 |
2024年 | 1576篇 |
2023年 | 1440篇 |
2022年 | 1927篇 |
2021年 | 2725篇 |
2020年 | 2147篇 |
2019年 | 1849篇 |
2018年 | 1817篇 |
2017年 | 2008篇 |
2016年 | 1863篇 |
2015年 | 2400篇 |
2014年 | 2873篇 |
2013年 | 3491篇 |
2012年 | 3749篇 |
2011年 | 3980篇 |
2010年 | 3593篇 |
2009年 | 3340篇 |
2008年 | 3468篇 |
2007年 | 3322篇 |
2006年 | 3325篇 |
2005年 | 2817篇 |
2004年 | 1992篇 |
2003年 | 1806篇 |
2002年 | 1894篇 |
2001年 | 1682篇 |
2000年 | 1456篇 |
1999年 | 1565篇 |
1998年 | 1157篇 |
1997年 | 1018篇 |
1996年 | 995篇 |
1995年 | 811篇 |
1994年 | 666篇 |
1993年 | 488篇 |
1992年 | 440篇 |
1991年 | 327篇 |
1990年 | 213篇 |
1989年 | 181篇 |
1988年 | 159篇 |
1987年 | 99篇 |
1986年 | 68篇 |
1985年 | 62篇 |
1984年 | 40篇 |
1983年 | 24篇 |
1982年 | 34篇 |
1981年 | 19篇 |
1980年 | 20篇 |
1979年 | 8篇 |
1955年 | 2篇 |
1953年 | 3篇 |
1951年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
WuGang HeZhen-Li 《核技术(英文版)》1998,9(3):176-180
The influence of fertilization with urea and ryegrass on nitrogen utilization and transformation in red soil has been studied by using ^15N tracer method.When urea and ryegrass were applied alone or in combination,the percentage of N uptaken by ryegrass from labelled urea was 3 and 1.7 times that from labelled ryegrass for the application rate of 200mgN.kg^-1 and 100mgN.kg^-1,respectively;combining application of ryegrass and ureareduced uptake of urea N and increased uptake of ryegrass N by ryegrass plant,but the percentage of N residued in soil increased for urea and decreased for ryegrass.when urea and ryegrass were applied alone,the percentage of N residued in soil from labelled ryegrass was more than 69% while that from labelled urea was less than 25%,and much more ryegrass N was incorporated into humus than urea N. 相似文献
63.
Dingfang Liu Zheng Teng John J. Sansalone Frank K. Cartledge 《Canadian Metallurgical Quarterly》2001,127(10):879-888
Most current control strategies for storm water treatment utilize fixed or filter-bed media with specific gravity (ρs) greater than 1.0. In contrast to Part I, Part II focuses on such higher density (ρs > 1.0) manganese-oxide-coated media that can be used in combined unit operations and processes for in-situ treatment of storm water. Methods were developed to coat manganese oxides onto sand and cementitious media for storm water treatment. With respect to manganese, coatings of ramsdellite produced a point of zero charge (PZC) of 5.2, while mixtures of birnessite and cryptomelane produced a PZC of 2.6 Manganese oxide increased the specific surface area (SSA) of sand and cementitious media. Manganese-oxide-coated sand (MOCS) produced a larger SSA (2.48-m2∕g), as compared with birnessite-coated media (BCM) (1.51 m2∕g), while the two have a similar surface charge (PZC = 6.4). Manganese-oxide-coated cementitious media (MOCM) produced a significantly larger SSA (19.49 m2∕g), as compared with coated sand, and SEM analyses indicated the surface contained manganese oxide and calcite of thickness 10–30 μm. Based on the results, coated cementitious media provided surface characteristics that can significantly enhance filtration and adsorption of heavy metal in storm water, in comparison to sand. 相似文献
64.
本文将近期发展起来的研究溶液中分子络合物的折射法用于氯苯-苯酚体系。以侵入式折射仪测定了该体系在惰性溶剂四氯化碳中的络合常数,并对R.A.Singh等的论文中关于△n~2的求算问题进行了商榷。 相似文献
65.
An intelligent verification platform based on a structured analysis model is presented.Using an abstract model mechanism with specific signal interfaces for user callback,the unified structured analysis data,shared by the electronic system level design,functional verification,and performance evaluation,enables efficient management review,auto-generation of code,and modeling in the transaction level.We introduce the class tree,flow parameter diagram,structured flow chart,and event-driven finite state machine as structured analysis models.As a sand table to carry maps from different perspectives and levels via an engine,this highly reusable platform provides the mapping topology to search for unintended consequences and the graph theory for comprehensive coverage and smart test cases.Experimental results show that the engine generates efficient test sequences,with a sharp increase in coverage for the same vector count compared with a random test. 相似文献
66.
Wei Fang Rui Jiang Hao Zheng Yi Zheng Yi Sun Xin Liang Hong-Fa Xiang Yue-Zhan Feng Yan Yu 《稀有金属(英文版)》2021,(2):433-439
The practical application of sodium metal batteries (SMBs) is hampered due to the inferior interfacial stability between Na metal and conventional electrolytes.... 相似文献
67.
68.
Flexible Photodetectors: Low‐Temperature Heteroepitaxy of 2D PbI2/Graphene for Large‐Area Flexible Photodetectors (Adv. Mater. 36/2018)
下载免费PDF全文

69.
Ping Fan Jing-rong Chi Guang-xing Liang Xing-min Cai Dong-ping Zhang Zhuang-hao Zheng Peng-ju Cao Tiao-bao Chen 《Journal of Materials Science: Materials in Electronics》2012,23(11):1957-1960
Cu(In, Ga)Se2 (CIGS) thin films were fabricated by ion beam sputtering deposition from a single quaternary target at different substrate temperatures (T sub). The thin films were characterized with X-ray diffractometry, scanning electron microscopy, energy-dispersive X-ray spectroscopy and four-point probe technique to study the microstructures, surface morphology, composition and electrical properties, respectively. The results show that the films grown above 400?°C are of chalcopyrite structure. Cu(In0.7Ga0.3)Se2 thin film was obtained when T sub is 550?°C. The Cu and Se atomic percentage when T sub is above 500?°C is higher than when T sub is below 500?°C. With the increase in T sub, the surfaces morphology of the films is denser and the resistivity of the films decreases. 相似文献
70.