全文获取类型
收费全文 | 109599篇 |
免费 | 1644篇 |
国内免费 | 439篇 |
专业分类
电工技术 | 1087篇 |
综合类 | 2330篇 |
化学工业 | 17144篇 |
金属工艺 | 5205篇 |
机械仪表 | 3458篇 |
建筑科学 | 3314篇 |
矿业工程 | 886篇 |
能源动力 | 1751篇 |
轻工业 | 5282篇 |
水利工程 | 1488篇 |
石油天然气 | 586篇 |
无线电 | 10885篇 |
一般工业技术 | 20203篇 |
冶金工业 | 8817篇 |
原子能技术 | 520篇 |
自动化技术 | 28726篇 |
出版年
2022年 | 247篇 |
2021年 | 417篇 |
2020年 | 271篇 |
2019年 | 352篇 |
2018年 | 14773篇 |
2017年 | 13643篇 |
2016年 | 10357篇 |
2015年 | 989篇 |
2014年 | 833篇 |
2013年 | 1841篇 |
2012年 | 4040篇 |
2011年 | 10509篇 |
2010年 | 9104篇 |
2009年 | 6426篇 |
2008年 | 7810篇 |
2007年 | 8730篇 |
2006年 | 1081篇 |
2005年 | 2065篇 |
2004年 | 1843篇 |
2003年 | 1864篇 |
2002年 | 1236篇 |
2001年 | 583篇 |
2000年 | 569篇 |
1999年 | 505篇 |
1998年 | 528篇 |
1997年 | 463篇 |
1996年 | 529篇 |
1995年 | 458篇 |
1994年 | 467篇 |
1993年 | 451篇 |
1992年 | 445篇 |
1991年 | 295篇 |
1990年 | 412篇 |
1989年 | 394篇 |
1988年 | 343篇 |
1987年 | 405篇 |
1986年 | 352篇 |
1985年 | 448篇 |
1984年 | 463篇 |
1983年 | 402篇 |
1982年 | 377篇 |
1981年 | 298篇 |
1980年 | 298篇 |
1979年 | 357篇 |
1978年 | 300篇 |
1977年 | 240篇 |
1976年 | 220篇 |
1975年 | 246篇 |
1974年 | 219篇 |
1973年 | 224篇 |
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
131.
Georgios D. Styliaras Georgios K. Tsolis Chris M. Papaterpos 《International Journal on Digital Libraries》2007,8(1):61-78
In this paper, AssetCollector is presented, which is a system for managing collections of cultural assets. AssetCollector
covers the needs of collection curators towards defining, populating and searching a collection in a flexible way, while supporting
them in generating reports based on the collection’s assets and reusing them in order to build web sites and CD-ROMs. In order
to support the above functionality, the system provides the content structuring subsystem, the content input subsystem, the
search subsystem and the report subsystem. The use of the subsystems is straightforward and requires no technical skills from
the curators. AssetCollector has been successfully applied for organizing various collections of cultural assets in Greece,
such as archaeological sites, museums and published books. In the future, an evaluation procedure is planned in order to further
refine the use of the system according to the targeted users’ needs. Furthermore, more import and export facilities will be
provided, which will make the system compliant with widely accepted standards. 相似文献
132.
Jules Sadefo Kamdem 《Computing and Visualization in Science》2007,10(4):197-210
In this paper, we generalize the Linear VaR method from portfolios with normally distributed risk factors to portfolios with
mixture of elliptically distributed ones. We treat both the Expected Shortfall and the Value-at-Risk of such portfolios. Special
attention is given to the particular case of a mixture of multivariate t-distributions.
This is a part of J. SADEFO-KAMDEM PhD Thesis[12] of the Université de Reims, France . It has been presented at the workshop
on modelling and computation in Financial Engineering at Bad Herrenalb, Germany May 6-8, 2003. The author is an associate
professor at the Department of mathematics, université d’Evry Val d’Essonne. 相似文献
133.
134.
Compared to other fields of engineering, in mechanical engineering, the Discrete Element Method (DEM) is not yet a well known
method. Nevertheless, there is a variety of simulation problems where the method has obvious advantages due to its meshless
nature. For problems where several free bodies can collide and break after having been largely deformed, the DEM is the method
of choice. Neighborhood search and collision detection between bodies as well as the separation of large solids into smaller
particles are naturally incorporated in the method. The main DEM algorithm consists of a relatively simple loop that basically
contains the three substeps contact detection, force computation and integration. However, there exists a large variety of
different algorithms to choose the substeps to compose the optimal method for a given problem. In this contribution, we describe
the dynamics of particle systems together with appropriate numerical integration schemes and give an overview over different
types of particle interactions that can be composed to adapt the method to fit to a given simulation problem. Surface triangulations
are used to model complicated, non-convex bodies in contact with particle systems. The capabilities of the method are finally
demonstrated by means of application examples.
Commemorative Contribution. 相似文献
135.
136.
137.
138.
Ronald R. Delyser Sheila S. Thompson Jerry Edelstein Corinne Lengsfeld Albert J. Rosa Paul J. Rullkoetter Robert Whitman Margaret Whitt 《工程教育杂志》2003,92(3):269-273
A team of faculty members at the University of Denver changed the learning environment in key courses in the Department of Engineering from predominately teacher centered to student centered. Through this funded project new grading methods were implemented, classrooms were renovated and wired with studio layouts to facilitate learning, the Engineering Circuits Laboratory was rewired and instrumented for automated data acquisition and reporting, and two new pedagogical approaches were developed. At the onset of the project, six goals were established related to student learning. The introduction of industry standard hardware and software provided students with unprecedented hands‐on experience and project related activities stimulated faculty innovations in other current and future courses. Assessment results indicate that the new grading system improved the clarity of expectations for students before assignments were given resulting in increased reported motivation for learning in many courses. Even though course GPAs did not always reflect higher achievement on graded work, faculty members firmly believe that deeper understanding was achieved because more complex material was assimilated. 相似文献
139.
Robert R. Gillies Jayne Brim Box Jürgen Symanzik Eli J. Rodemaker 《Remote sensing of environment》2003,86(3):411-422
Impervious surface area (ISA) was derived for a period from 1979 to 1997 from Landsat MSS and TM data for the Line Creek watershed that lies to the south of the city of Atlanta, GA. The change in ISA is presented as an ecological indicator to examine the cumulative water resource impacts on mussel population in three sub-watersheds of Line Creek—namely, Line, Flat, and Whitewater creeks. The satellite analysis shows that ISA expansion occurred substantially from 1987 to 1997 and is predominantly in industrial, commercial, and shopping center (ICS) complexes but also in smaller lot-size residential development. Evidence of mussel habitat degradation is indicated and loss of species (in the region of 50 to 70%) is present in areas where ISA expansion is observed—specifically in ICS complex development in and around Peachtree City that drains directly into the Line and Flat creeks. This is in marked contrast to Whitewater Creek where overall development of ISA is less and no major loss of mussel species is observed. 相似文献
140.