全文获取类型
收费全文 | 88855篇 |
免费 | 967篇 |
国内免费 | 1957篇 |
专业分类
电工技术 | 1372篇 |
技术理论 | 2篇 |
综合类 | 678篇 |
化学工业 | 8307篇 |
金属工艺 | 2710篇 |
机械仪表 | 4300篇 |
建筑科学 | 6355篇 |
矿业工程 | 3769篇 |
能源动力 | 544篇 |
轻工业 | 16147篇 |
水利工程 | 2401篇 |
石油天然气 | 2207篇 |
武器工业 | 358篇 |
无线电 | 8823篇 |
一般工业技术 | 25574篇 |
冶金工业 | 1845篇 |
原子能技术 | 826篇 |
自动化技术 | 5561篇 |
出版年
2023年 | 365篇 |
2022年 | 473篇 |
2021年 | 464篇 |
2020年 | 330篇 |
2019年 | 377篇 |
2018年 | 424篇 |
2015年 | 416篇 |
2014年 | 843篇 |
2013年 | 850篇 |
2012年 | 7895篇 |
2011年 | 9826篇 |
2010年 | 2380篇 |
2009年 | 1556篇 |
2008年 | 6798篇 |
2007年 | 6280篇 |
2006年 | 5403篇 |
2005年 | 4817篇 |
2004年 | 4047篇 |
2003年 | 3587篇 |
2002年 | 3288篇 |
2001年 | 2705篇 |
2000年 | 2523篇 |
1999年 | 1620篇 |
1998年 | 973篇 |
1997年 | 1055篇 |
1996年 | 1002篇 |
1995年 | 1000篇 |
1994年 | 955篇 |
1993年 | 664篇 |
1992年 | 869篇 |
1991年 | 947篇 |
1990年 | 952篇 |
1989年 | 934篇 |
1988年 | 914篇 |
1987年 | 1112篇 |
1986年 | 1019篇 |
1985年 | 1085篇 |
1984年 | 1049篇 |
1983年 | 933篇 |
1982年 | 982篇 |
1981年 | 915篇 |
1980年 | 718篇 |
1979年 | 529篇 |
1978年 | 345篇 |
1977年 | 356篇 |
1976年 | 413篇 |
1975年 | 411篇 |
1974年 | 412篇 |
1967年 | 378篇 |
1965年 | 430篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
Covalent triazine frameworks (CTFs) have been recently employed for visible light-driven photocatalysis due to their unique optical and electronic properties. However, the usually highly hydrophobic nature of CTFs, which originates from their overall aromatic backbone, leads to limitations of CTFs for applications in aqueous media. In this study, we aim to extend the range of the application media of CTFs and design hybrid material of a CTF and mesoporous silica (SBA-15) for efficient photocatalysis in aqueous medium. A thiophene-containing CTF was directly synthesized in mesopores of SBA-15. Due to the high surface area and the added hydrophilic properties by silica, the hybrid material demonstrated excellent adsorption of organic molecules in water. This leads not only to high photocatalytic performance of the hybrid material for the degradation of organic dyes in water, but also for efficient photocatalysis in solvent-free and solid state. Furthermore, the reusability, stability and easy recovery of the hybrid material offers promising metal-free heterogeneous photocatalyst for broader applications in different reaction media. 相似文献
12.
The objective of this research is the rapid reconstruction of ancient buildings of historical importance using a single image. The key idea of our approach is to reduce the infinite solutions that might otherwise arise when recovering a 3D geometry from 2D photographs. The main outcome of our research shows that the proposed methodology can be used to reconstruct ancient monuments for use as proxies for digital effects in applications such as tourism, games, and entertainment, which do not require very accurate modeling. In this article, we consider the reconstruction of ancient Mughal architecture including the Taj Mahal. We propose a modeling pipeline that makes an easy reconstruction possible using a single photograph taken from a single view, without the need to create complex point clouds from multiple images or the use of laser scanners. First, an initial model is automatically reconstructed using locally fitted planar primitives along with their boundary polygons and the adjacency relation among parts of the polygons. This approach is faster and more accurate than creating a model from scratch because the initial reconstruction phase provides a set of structural information together with the adjacency relation, which makes it possible to estimate the approximate depth of the entire structural monument. Next, we use manual extrapolation and editing techniques with modeling software to assemble and adjust different 3D components of the model. Thus, this research opens up the opportunity for the present generation to experience remote sites of architectural and cultural importance through virtual worlds and real-time mobile applications. Variations of a recreated 3D monument to represent an amalgam of various cultures are targeted for future work. 相似文献
13.
正1.引言世界日益增长的人口使粮食需求增加,加之农业集约化生产导致农药的广泛使用,目的是使作物产量最大化。历史表明,农药管理不善可能会对人类和动物的健康以及环境造成严重的危害。监管机构要求合理使用杀虫剂,减少食品和环境中的农药残留,并提供关于农药及其残留物风险的更多信息。从这个意义上讲,国家和国际机构以及环保机构都对保护公众健康和环境进行了严格的监管。 相似文献
14.
正一个为巴黎而建的广场,一座为法国而建的图书馆这座图书馆是一座缘起之地,而不是一半寺庙一半超市的庞然巨物——请参考巴黎东区。图书馆的所在地位于塞纳河沿岸,是协和广场、战神广场和荣誉军人院等一系列连续场地中的一块。塞纳河沿岸的场地,是区域活化的决定性因素。第十三区的山岗朝向塞纳河,身后是Porte de Choisy和Porte d'Ivry大厦。法国国家图书馆无私地用自己的影响力和光彩推动了区域性保护与复兴。为了对 相似文献
15.
The critical properties of the mixed manganite La0.67–x Y x Ba0.23Ca0.1Mn O3 with x=0.10 and x=0.15 around the paramagnetic(PM)-ferromagnetic(FM) phase transition were investigated through various techniques. These involved modified Arrott plots, Kouvel-Fisher method and Widom scaling relation. Magnetic data, analyzed in the critical region, using the above methods, yielded the critical exponents for(x=0.10) La0.57Y0.10Ba0.23Ca0.1Mn O3(β=0.312±0.002 and γ=1.147±0.003 at T C=299.23±0.05 K). Moreover, the estimated critical exponents of(x=0.15) La0.52Y0.15Ba0.23Ca0.1Mn O3 were β=0.286±0.004 and γ=0.943±0.002 at T C=289.53±0.06 K. The critical exponents’ values were close to the theoretical values of 3D-Ising model and tricritical mean-field model. These results suggested that the present composition should be close to a tricritical point in the La0.67–x Y x Ba0.23Ca0.1Mn O3 phase diagram. Expressing the field dependence as ΔS M∝H n allowed us to establish a relationship between the exponent n and the critical exponents of the material and to propose a phenomenological universal curve for the field dependence of ΔS M. 相似文献
16.
在这个泛偶像的时代,有太多风采照人、气质高雅的“星”和学富五车、雄韬伟略的“家”,他们固然值得仰望和崇拜;但是,这也是一个反偶像的时代,当正统的“偶像文化”被推到极致后,许多人产生“审美疲劳”,他们开始有意识地颠覆传统,告别英雄、躲避崇高。“芙蓉姐姐”的出现和风起云涌正是如此:“她颠覆了理想型偶像的高大全假大空,掏出大众心中的真、小乃至庸常的一面,甚至以反讽、自嘲的面目出现。”殊途同归的是,在民众的集体狂欢之后,所谓的反偶像,最终又走上了炮制偶像的路子——在博客江湖,一切成为平民的现实:一个渺小的,甚至和明星毫无关联的 相似文献
17.
18.
1 Introduction High power laser diode arrays (LDA) have many advan- tages such as small volume, long working life, high slope efficiency and high optical density, so they have many applications in medical treatment, material pro- cessing, and for the pumping source of solid laser and etc. But unfortunately, the LDA can not be easy to use directly in these fields because of their poor beam quality and extremely asymmetric divergent beams (!x≈ 5°~10°and !y≈20°~35°, for example), so it … 相似文献
19.
20.
与昌圆双雄(台积电、联电)有着密不可分的IC设计服务公司创意与智原,于2003年8、9月接二连三的成立IP Mall,其希望透过IP(Intellectual Property)交易平台的建立,授权给IC设计业者加速重复使用IP以缩短芯片开发时间,也迫使SoC(System-on-a-Chip)与SiP(System-in-a-Package)的争夺战再一次浮上台面。 相似文献