全文获取类型
收费全文 | 214613篇 |
免费 | 15379篇 |
国内免费 | 8987篇 |
专业分类
电工技术 | 12436篇 |
技术理论 | 6篇 |
综合类 | 13266篇 |
化学工业 | 29512篇 |
金属工艺 | 12950篇 |
机械仪表 | 12239篇 |
建筑科学 | 12696篇 |
矿业工程 | 4973篇 |
能源动力 | 5095篇 |
轻工业 | 12654篇 |
水利工程 | 4686篇 |
石油天然气 | 6772篇 |
武器工业 | 1979篇 |
无线电 | 25086篇 |
一般工业技术 | 28894篇 |
冶金工业 | 8250篇 |
原子能技术 | 2001篇 |
自动化技术 | 45484篇 |
出版年
2024年 | 542篇 |
2023年 | 1828篇 |
2022年 | 4037篇 |
2021年 | 5816篇 |
2020年 | 4202篇 |
2019年 | 3269篇 |
2018年 | 17725篇 |
2017年 | 17307篇 |
2016年 | 13722篇 |
2015年 | 6426篇 |
2014年 | 7534篇 |
2013年 | 8717篇 |
2012年 | 13745篇 |
2011年 | 20341篇 |
2010年 | 18513篇 |
2009年 | 15340篇 |
2008年 | 16346篇 |
2007年 | 16577篇 |
2006年 | 8396篇 |
2005年 | 8067篇 |
2004年 | 6068篇 |
2003年 | 5211篇 |
2002年 | 4640篇 |
2001年 | 3672篇 |
2000年 | 2702篇 |
1999年 | 1934篇 |
1998年 | 1102篇 |
1997年 | 973篇 |
1996年 | 866篇 |
1995年 | 681篇 |
1994年 | 496篇 |
1993年 | 368篇 |
1992年 | 304篇 |
1991年 | 220篇 |
1990年 | 173篇 |
1989年 | 121篇 |
1988年 | 100篇 |
1987年 | 71篇 |
1986年 | 56篇 |
1968年 | 43篇 |
1967年 | 33篇 |
1966年 | 43篇 |
1965年 | 44篇 |
1960年 | 30篇 |
1959年 | 48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
991.
992.
993.
994.
Xiaodan Zhang Wei Liu Dale Sun Youguo Li 《Metallurgical and Materials Transactions A》2007,38(3):499-505
The transformation of carbides with austenization time of a high speed steel (HSS) roll material, manufactured by a centrifugal
casting method, has been studied. The correlation between wear resistance and the type, morphology, volume fraction, and distribution
of the carbides has also been investigated. Microstructural observations, X-ray diffraction (XRD) analysis, hardness measurements,
and energy dispersive spectroscopy (EDS) have been used to characterize the carbides. The type and volume fraction of carbides
were found to change with austenizing time. During austenization, the transformation of the M3C carbides can be postulated as M3C + γ-Fe → M2C, with much finer nodular and rodlike MC carbides also forming through a solid-state transformation. The M2C carbide decomposes as M2C + γ-Fe → MC + M7C3 + M6C. The decomposed carbide substantially maintains a platelike shape until the end of decomposition. The most important finding
of this study is that austenization results in changes in the type, morphology, volume fraction, and distribution of carbides
and that it can be controlled to produced a homogeneous distribution of hard carbides, resulting in an improvement in the
wear resistance of HSS rolls. This finding may be of great use for the industrial production of HSS rolls. 相似文献
995.
Following the original model for a single cell/dendrite growth by Hunt,[5] systematic numerical simulations are carried out with focus on cell shape evolution and tip radius selection in a directional
solidification process conducted in a capillary tube. Computations indicate that the anisotropy of solid/liquid interfacial
energy and the diameter of a capillary tube have significant influences on the selection of a tip shape. The anisotropy in
dilute SCN-salol alloys has been determined through the equilibrium droplet shape method and its value is 1.09 pct. The calculated
cell/dendrite shapes with this value of anisotropy agree with experimental observations where a single cell/dendrite of SCN-salol
alloys grows in a capillary tube. 相似文献
996.
主要介绍了土工布和膨润土防水毯(GCL)在垃圾卫生填埋场应用中的特点和作用,阐述了在卫生填埋场设计中选择土工布和GCL应注意的一些问题。 相似文献
997.
Real-time homogenous translucent material editing 总被引:4,自引:0,他引:4
This paper presents a novel method for real-time homogenous translucent material editing under fixed illumination. We consider the complete analytic BSSRDF model proposed by Jensen et al. [ [JMLH01] ], including both multiple scattering and single scattering. Our method allows the user to adjust the analytic parameters of BSSRDF and provides high-quality, real-time rendering feedback. Inspired by recently developed Precomputed Radiance Transfer (PRT) techniques, we approximate both the multiple scattering diffuse reflectance function and the single scattering exponential attenuation function in the analytic model using basis functions, so that re-computing the outgoing radiance at each vertex as parameters change reduces to simple dot products. In addition, using a non-uniform piecewise polynomial basis, we are able to achieve smaller approximation error than using bases adopted in previous PRT-based works, such as spherical harmonics and wavelets. Using hardware acceleration, we demonstrate that our system generates images comparable to [ [JMLH01] ]at real-time frame-rates. 相似文献
998.
In the design of algorithms for large-scale applications it is essential to consider the problem of minimizing I/O communication.
Geographical information systems (GIS) are good examples of such large-scale applications as they frequently handle huge amounts
of spatial data. In this paper we develop efficient external-memory algorithms for a number of important problems involving
line segments in the plane, including trapezoid decomposition, batched planar point location, triangulation, red--blue line
segment intersection reporting, and general line segment intersection reporting. In GIS systems the first three problems are
useful for rendering and modeling, and the latter two are frequently used for overlaying maps and extracting information from
them. 相似文献
999.
Confluent graphs capture the connection properties of train tracks, offering a very natural generalization of planar graphs,
and—as the example of railroad maps shows—are an important tool in graph visualization. In this paper we continue the study
of confluent graphs, introducing strongly confluent graphs and tree-confluent graphs. We show that strongly confluent graphs
can be recognized in NP (the complexity of recognizing confluent graphs remains open). We also give a natural elimination
ordering characterization of tree-confluent graphs, and we show that this class coincides with the (6,2)-chordal bipartite
graphs. Finally, we define outerconfluent graphs and identify the bipartite permutation graphs as a natural subclass. 相似文献
1000.
文章通过对夏热冬冷地区建筑节能应考虑的因素及相关技术指标,及高舒适的低能耗技术构成等方面的论述,从理论和实践中加以分析了目前建筑节能面临的问题和误区,从技术角度分析入手,提出了相应的解决措施和方法,以达到舒适和节能的要求为目的.同时还从另一个方面提醒购房者在购房时要增强节能意识,警惕假节能. 相似文献