全文获取类型
收费全文 | 328956篇 |
免费 | 3655篇 |
国内免费 | 1007篇 |
专业分类
电工技术 | 6629篇 |
综合类 | 460篇 |
化学工业 | 45799篇 |
金属工艺 | 16030篇 |
机械仪表 | 13224篇 |
建筑科学 | 7649篇 |
矿业工程 | 1706篇 |
能源动力 | 8078篇 |
轻工业 | 22534篇 |
水利工程 | 3315篇 |
石油天然气 | 4742篇 |
武器工业 | 31篇 |
无线电 | 41560篇 |
一般工业技术 | 69423篇 |
冶金工业 | 54754篇 |
原子能技术 | 6138篇 |
自动化技术 | 31546篇 |
出版年
2021年 | 2333篇 |
2020年 | 1721篇 |
2019年 | 2047篇 |
2018年 | 11468篇 |
2017年 | 12029篇 |
2016年 | 8085篇 |
2015年 | 2904篇 |
2014年 | 4267篇 |
2013年 | 11948篇 |
2012年 | 9051篇 |
2011年 | 16925篇 |
2010年 | 14808篇 |
2009年 | 14715篇 |
2008年 | 14874篇 |
2007年 | 16788篇 |
2006年 | 7659篇 |
2005年 | 10227篇 |
2004年 | 8358篇 |
2003年 | 8232篇 |
2002年 | 6788篇 |
2001年 | 6705篇 |
2000年 | 6262篇 |
1999年 | 6577篇 |
1998年 | 16737篇 |
1997年 | 11610篇 |
1996年 | 8987篇 |
1995年 | 6747篇 |
1994年 | 6060篇 |
1993年 | 5986篇 |
1992年 | 4255篇 |
1991年 | 4130篇 |
1990年 | 3927篇 |
1989年 | 3721篇 |
1988年 | 3626篇 |
1987年 | 3078篇 |
1986年 | 2999篇 |
1985年 | 3283篇 |
1984年 | 2995篇 |
1983年 | 2899篇 |
1982年 | 2684篇 |
1981年 | 2599篇 |
1980年 | 2512篇 |
1979年 | 2351篇 |
1978年 | 2155篇 |
1977年 | 2615篇 |
1976年 | 3561篇 |
1975年 | 1769篇 |
1974年 | 1734篇 |
1973年 | 1660篇 |
1972年 | 1459篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
A new spreadsheet-cell-object-oriented algorithm for the first-order reliability method is proposed and illustrated for cases with correlated nonnormals and explicit and implicit performance functions. The new approach differs from the writers earlier algorithm by obviating the need for computations of equivalent normal means and equivalent normal standard deviations. It obtains the solution faster and is more efficient, robust, and succinct. Other advantages include ease of initialization prior to constrained optimization, ease of randomization of initial values for checking robustness, and fewer required optimization constraints during spreadsheet-automated search for the design point. Two cases with implicit performance functions, namely an asymmetrically loaded beam on Winkler medium and a strut with complex supports are analyzed using the new approach and discussed. Comparisons are also made between the proposed approach and that based on Rosenblatt transformation. 相似文献
992.
Practical Equivalent Continuum Model for Simulation of Jointed Rock Mass Using FLAC3D 总被引:1,自引:0,他引:1
A simple practical equivalent continuum numerical model for simulating the behavior of jointed rock mass has been extended to three-dimensional using FLAC3D. This model estimates the properties of jointed rock mass from the properties of intact rock and a joint factor (Jf), which is the integration of the properties of joints to take care of the effects of frequency, orientation, and strength of joint. A new FISH function has been written in FLAC3D specifically for modeling jointed rocks using the Duncan and Chang hyperbolic model. This model has been validated first with simple element tests at different confining pressures for different rocks with different joint configurations. Explicit modeling of the joints has also been done in element tests and results obtained compare well with the results of equivalent continuum model and also with experimental results. Further, this has been applied for a case study of a large underground power house cavern in the Himalayas. The analysis has been done under various stages of excavation, assigning a null model available in FLAC3D for simulating the excavation. 相似文献
993.
William D. Tape John B. Kennedy Murty K. S. Madugula 《Canadian Metallurgical Quarterly》2007,11(1):91-98
The current methods of connecting the flanges of precast double tee members, and their respective short comings in specific situations, are described. A new carbon fiber-reinforced polymer (CFRP) flange-to-flange connection is proposed to eliminate the problems associated with repair requirements for the current connections. Design expressions for the currently used mechanical anchorage and the proposed CFRP connection are presented. A comparative calculation for the two systems is given. 相似文献
994.
995.
996.
We show new upper bounds for problems in the W-hierarchy of fixed-parameter complexity. A crucial ingredient of our proofs
is an extension to the W-RAM model, which permits more-powerful operations but remains equivalent to the original. We use
the extended model to give new upper bounds for Subsetsum, Maximum Irredundant Set, and various problems concerning intersection
of finite-state machines. 相似文献
997.
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
998.
999.
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
1000.