全文获取类型
收费全文 | 84516篇 |
免费 | 1049篇 |
国内免费 | 409篇 |
专业分类
电工技术 | 779篇 |
综合类 | 2317篇 |
化学工业 | 11626篇 |
金属工艺 | 4802篇 |
机械仪表 | 3041篇 |
建筑科学 | 2170篇 |
矿业工程 | 562篇 |
能源动力 | 1158篇 |
轻工业 | 3671篇 |
水利工程 | 1277篇 |
石油天然气 | 342篇 |
无线电 | 9367篇 |
一般工业技术 | 16452篇 |
冶金工业 | 2706篇 |
原子能技术 | 262篇 |
自动化技术 | 25442篇 |
出版年
2023年 | 20篇 |
2022年 | 59篇 |
2021年 | 66篇 |
2020年 | 48篇 |
2019年 | 56篇 |
2018年 | 14500篇 |
2017年 | 13409篇 |
2016年 | 9989篇 |
2015年 | 626篇 |
2014年 | 266篇 |
2013年 | 295篇 |
2012年 | 3180篇 |
2011年 | 9444篇 |
2010年 | 8318篇 |
2009年 | 5575篇 |
2008年 | 6809篇 |
2007年 | 7797篇 |
2006年 | 147篇 |
2005年 | 1227篇 |
2004年 | 1139篇 |
2003年 | 1181篇 |
2002年 | 552篇 |
2001年 | 108篇 |
2000年 | 179篇 |
1999年 | 65篇 |
1998年 | 79篇 |
1997年 | 53篇 |
1996年 | 56篇 |
1995年 | 16篇 |
1994年 | 17篇 |
1993年 | 15篇 |
1992年 | 17篇 |
1991年 | 27篇 |
1988年 | 11篇 |
1969年 | 24篇 |
1968年 | 43篇 |
1967年 | 33篇 |
1966年 | 42篇 |
1965年 | 44篇 |
1964年 | 11篇 |
1963年 | 28篇 |
1962年 | 22篇 |
1961年 | 18篇 |
1960年 | 30篇 |
1959年 | 35篇 |
1958年 | 37篇 |
1957年 | 36篇 |
1956年 | 34篇 |
1955年 | 63篇 |
1954年 | 68篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
151.
Emergency department status boards: user-evolved artefacts for inter- and intra-group coordination 总被引:1,自引:1,他引:0
Robert L. Wears Shawna J. Perry Stephanie Wilson Julia Galliers James Fone 《Cognition, Technology & Work》2007,9(3):163-170
Large, easily viewed status boards are commonly used in some healthcare settings such as emergency departments, operating
theaters, intensive care units, and inpatient wards. Because these artefacts were developed by front-line users, and have
little to no supervisory or regulatory control, they offer valuable insights into the theories of work and hazard held by
those users. Although the status boards case were locally developed over many years for within-group coordination, they have
also become useful for between-group coordination across organizational boundaries. In this paper, we compare and contrast
the use of such status boards in two disparate settings: a US emergency department, and a UK pediatric ward, and note striking
similarities in their form and usage, despite the large differences in setting. 相似文献
152.
Artem Sokolov Darrell Whitley Andre’ da Motta Salles Barreto 《Genetic Programming and Evolvable Machines》2007,8(3):221-237
This paper evaluates different forms of rank-based selection that are used with genetic algorithms and genetic programming.
Many types of rank based selection have exactly the same expected value in terms of the sampling rate allocated to each member
of the population. However, the variance associated with that sampling rate can vary depending on how selection is implemented.
We examine two forms of tournament selection and compare these to linear rank-based selection using an explicit formula. Because
selective pressure has a direct impact on population diversity, we also examine the interaction between selective pressure
and different mutation strategies. 相似文献
153.
154.
The multi-homogeneous Bezout number is a bound for the number of solutions of a system of multi-homogeneous polynomial equations,
in a suitable product of projective spaces. Given an arbitrary, not necessarily multi-homogeneous, system, one can ask for
the optimal multi-homogenization that would minimize the Bezout number. In this paper it is proved that the problem of computing,
or even estimating, the optimal multi-homogeneous Bezout number is actually NP-hard. In terms of approximation theory for
combinatorial optimization, the problem of computing the best multi-homogeneous structure does not belong to APX, unless P
= NP. Moreover, polynomial-time algorithms for estimating the minimal multi-homogeneous Bezout number up to a fixed factor
cannot exist even in a randomized setting, unless BPP ⫆ NP. 相似文献
155.
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
156.
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
157.
158.
159.
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
160.