全文获取类型
收费全文 | 12081篇 |
免费 | 1204篇 |
国内免费 | 946篇 |
学科分类
工业技术 | 14231篇 |
出版年
2024年 | 29篇 |
2023年 | 125篇 |
2022年 | 246篇 |
2021年 | 317篇 |
2020年 | 324篇 |
2019年 | 321篇 |
2018年 | 277篇 |
2017年 | 333篇 |
2016年 | 413篇 |
2015年 | 439篇 |
2014年 | 593篇 |
2013年 | 707篇 |
2012年 | 792篇 |
2011年 | 907篇 |
2010年 | 750篇 |
2009年 | 779篇 |
2008年 | 822篇 |
2007年 | 823篇 |
2006年 | 843篇 |
2005年 | 719篇 |
2004年 | 635篇 |
2003年 | 572篇 |
2002年 | 445篇 |
2001年 | 340篇 |
2000年 | 281篇 |
1999年 | 277篇 |
1998年 | 208篇 |
1997年 | 147篇 |
1996年 | 124篇 |
1995年 | 101篇 |
1994年 | 119篇 |
1993年 | 84篇 |
1992年 | 67篇 |
1991年 | 55篇 |
1990年 | 49篇 |
1989年 | 41篇 |
1988年 | 28篇 |
1987年 | 16篇 |
1986年 | 13篇 |
1985年 | 13篇 |
1984年 | 10篇 |
1982年 | 3篇 |
1981年 | 8篇 |
1980年 | 4篇 |
1979年 | 3篇 |
1978年 | 3篇 |
1976年 | 3篇 |
1975年 | 6篇 |
1964年 | 2篇 |
1954年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
YAG:Ce Phosphors for WLED via Nano-Pesudoboehmite Sol-Gel Route 总被引:5,自引:0,他引:5
The sub-micron sized YAG : Ce phosphors were synthesized via a modified sol-gel method by peptizing nano-pesudoboehmite particulate. It is found that YAG phase from the dried gel powders appears at 1000 ℃ then the pure YAG phase exists at a relatively lower sintering temperature of 1400 ℃. The smaller sizes of phosphors in the ranges of 1 - 3 μm are obtained due to the contribution of seeding effects of nano-sized alumina particles to strengthen each step of the processes. Both the excitation and emission spectra of photoluminescence of the phosphor obtained at 1400 ℃ meet well with the spectroscopic requirements of the WLED phosphors. 相似文献
62.
63.
64.
Two elements enter the choice between 2 and 3SLS for full-system estimation: statistical efficiency and computational cost. 2SLS always has the computational edge, but 3SLS can be more efficient, a relative advantage that increases with the strength of the interrelations among the error terms. A measure of these interrelations is thus helpful in making the choice, and, when there are only two equations, this has suggested using a high pairwise error correlation as an indicator of when to use 3SLS. In larger systems of equations, however, these pairwise correlations can remain small even though more general interrelations give 3SLS the relative advantage. More general indicators are therefore needed, and this paper suggests three such and demonstrates their efficacy.Professor of Economics, Boston College, and Principal Research Associate, Center for Computational Research in Economics and Management Science, MIT. All computation was done on the TROLL system at MIT. My thanks go to Josh Charap for his able research assistance. This research was sponsored in part by the National Science Foundation under grant #IST-8420614. 相似文献
65.
66.
67.
本文介绍亚州第一台模拟分量电视车视频系统的设计思想,比较详细地阐述了该车的各种功能,总结了不同于复合电视车的新特点。 相似文献
68.
Paul Camion Bernard Courteau Philippe Delsarte 《Applicable Algebra in Engineering, Communication and Computing》1992,2(3):147-162
The concept of the combinatorial matrix of an unrestricted code and the notion of anr-partition design admitted by a code are introduced and discussed in detail. The theory includes a characterization of completely regular codes, and a combinatorial interpretation of the fact that the distinct rows of the distance distribution matrix of a code are linearly independent. In general, it is possible to compute the distance distribution matrix of any code admitting a given partition design by solving a well-defined system of linear equations; this is an efficient technique provided the number of classes in the partition is relatively small. 相似文献
69.
The application of irradiation in silicon crystal is introduced.The defects caused by irradiation are reviewed and some major ways of studying defects in irradiated silicon are summarized.Furthermore the problems in the investigation of irradiated silicon are discussed as well as its properties. 相似文献
70.
Safe and Economic Operation of Power Plants – Research Results in the Field of Materials, Design and Maintenance Components of power plants which undergo high temperatures are subjected to complex loading situations. The requirements on the used materials result from the special operation conditions of the plants and have to be adjusted to the steadily growing requirements on higher efficiency of the complete power plant as well as to those of safe and economic operation. The expenses for control and downtimes are directly connected with economic efficiency and availability. However, in case of new procedures or components it is not possible to revert to the existing know‐how. Different failure mechanisms than known before can occur. The same goes for the load situation. Therefore the knowledge base has to be extended to in‐advance or even parallely running scientific examinations that life assessment and maintenance strategies can be applied which guarantee the operational reliability and the efficiency of the plant. The main emphasis of these F&E works has to be put on condition monitoring based on actual operational data, the standard materials’ and component’s behaviour (deformation, damage and failure behaviour) in connection with design of components and the related material laws. In the framework of applied AVIF projects, following problems are handled:. – qualification of materials by determinating parameters related to practise. – optimal design of components by making available material laws and numerical tools. – economic manufacturing of components by qualifying processing methods such as welding. – The results can be transferred to concepts for safe and economic operation of power plants, especially for newly introduced materials for which there is no operational experience available. 相似文献