全文获取类型
收费全文 | 8578篇 |
免费 | 692篇 |
国内免费 | 470篇 |
专业分类
电工技术 | 145篇 |
综合类 | 977篇 |
化学工业 | 1324篇 |
金属工艺 | 114篇 |
机械仪表 | 148篇 |
建筑科学 | 524篇 |
矿业工程 | 188篇 |
能源动力 | 517篇 |
轻工业 | 363篇 |
水利工程 | 147篇 |
石油天然气 | 541篇 |
武器工业 | 24篇 |
无线电 | 1268篇 |
一般工业技术 | 848篇 |
冶金工业 | 343篇 |
原子能技术 | 59篇 |
自动化技术 | 2210篇 |
出版年
2024年 | 35篇 |
2023年 | 108篇 |
2022年 | 174篇 |
2021年 | 294篇 |
2020年 | 355篇 |
2019年 | 219篇 |
2018年 | 241篇 |
2017年 | 300篇 |
2016年 | 336篇 |
2015年 | 306篇 |
2014年 | 478篇 |
2013年 | 602篇 |
2012年 | 504篇 |
2011年 | 576篇 |
2010年 | 490篇 |
2009年 | 536篇 |
2008年 | 463篇 |
2007年 | 573篇 |
2006年 | 542篇 |
2005年 | 468篇 |
2004年 | 354篇 |
2003年 | 366篇 |
2002年 | 264篇 |
2001年 | 210篇 |
2000年 | 162篇 |
1999年 | 148篇 |
1998年 | 128篇 |
1997年 | 79篇 |
1996年 | 80篇 |
1995年 | 69篇 |
1994年 | 58篇 |
1993年 | 39篇 |
1992年 | 32篇 |
1991年 | 25篇 |
1990年 | 17篇 |
1989年 | 23篇 |
1988年 | 20篇 |
1987年 | 9篇 |
1986年 | 13篇 |
1985年 | 10篇 |
1984年 | 8篇 |
1983年 | 3篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1958年 | 1篇 |
1957年 | 1篇 |
1951年 | 2篇 |
排序方式: 共有9740条查询结果,搜索用时 15 毫秒
21.
Yvon Maday Frédéric Magoulès 《Computer Methods in Applied Mechanics and Engineering》2007,196(8):1541-1553
In this paper an original variant of the Schwarz domain decomposition method is introduced for heterogeneous media. This method uses new optimized interface conditions specially designed to take into account the heterogeneity between the sub-domains on each sides of the interfaces. Numerical experiments illustrate the dependency of the proposed method with respect to several parameters, and confirm the robustness and efficiency of this method based on such optimized interface conditions. Several mesh partitions taking into account multiple cross points are considered in these experiments. 相似文献
22.
Christine Bernardi Frédéric Hecht 《Computer Methods in Applied Mechanics and Engineering》2007,196(8):1554-1573
Darcy’s equations model the flow of a viscous incompressible fluid in a rigid porous medium. One of the parameters of the system depends on the permeability of the medium and, when this medium is not homogeneous, the variations of the parameter could be very high. To handle this phenomenon, we propose a discretization of the model that relies on the mortar finite element method. Indeed, the idea is to construct a decomposition of the domain such that the permeability is constant on each element of the partition and to use independent meshes on the different subdomains. We perform the a priori and a posteriori analysis of this discretization and present some numerical experiments which are in good coherency with the results of the analysis. 相似文献
23.
24.
利用分形几何确定多孔介质的孔尺寸分布 总被引:5,自引:0,他引:5
提出了利用分形几何确定多孔介质孔尺寸分布的方法。考虑多孔介质中孔间的屏蔽,采用此方法得到的孔尺寸分布范围比采用平行孔模型宽,分别采用本方法和平行孔模型测定γ-Al2O3催化剂的孔尺寸分布,构造简单立方体三维网络模型模拟压汞过程,并将模拟曲线与γ-Al2O3压汞实验曲线比较,结果表明,采用本方法所得孔尺雨分布优于平行孔模型所得孔尺寸分布。 相似文献
25.
现代信息化的技术的进步给我们的社会生活带来的很大帮助,而网络媒体就是信息化技术的一个产物,它能迅速成为市场的一大宠儿,不仅有着他自身独有的优势和特点,还有与之相适应的外部条件,传统媒体在某些方面已经不能适应现代产业的发展,人们正在寻求一种迅速、容量大的传播方式,于是网络媒体的出现众望所归。但是由于我国的网络媒体的出现时间尚短,难免有着这样那样的问题,随着网络媒体为越来越多的人所接受,其问题也更加严重,尤其是传播不良的信息荼毒青少年的思想健康,网络受到黑客、病毒的侵袭,网上传播虚假信息、盗窃数据库资料等等,信息安全问题突出,这些问题越来越受到全世界的关注,成为全球共同注意的事情。 相似文献
26.
教学录像是精品课程建设的重要内容之一。为了开发集教学性、科学性、技术性与艺术性于一体的精品课程教学录像,针对精品课程教学录像的性质,参照其上网技术指标及网上浏览的特点,对其建设现状进行分析,并提出了精品课程教学录像建设的建议。 相似文献
27.
孙俊菊 《计算机光盘软件与应用》2012,(2):235-236
实验室网络教学资源与人才培养创新理论的研究,要灵活多样,寻求多种途径,利用虚拟实验室及网络等现有资源,开展开放式实验实训和校外实训,利用远程教学,将实训教学与职业技能鉴定相结合,以网络资讯平台为基础,通过电视式校园媒体平台,以市场为导向的方针,规划人力资源,以就业为核心的现代化的传输手段,实现适应市场需求的各类人才的培养计划,努力建设一个以高校校园市场为基础的、完善的、能沟通企业、学校和学生的产、教、学信息平台。 相似文献
28.
T. Yang B.H. LiDepartment of Materials Physics University of Science Technology Beijing Beijing ChinaK. Kang T. SuzukiInformation Storage Materials Laboratory Toyota Technological Institute Nagoya - Japan 《金属学报(英文版)》2003,16(4):261-265
(FePt/Ag)n nano-multilayers were deposited on MgO (100) single crystal with laser ablation and then subjected to annealing. FePt L1o grains with (001) texture and thus a large perpendicular magnetic anisotropy constant Ku of the order of 106 J/m3 were formed. A thick Ag layer is found to be favorable for decreasing the dispersion of the easy axis for magnetization. The measurement of time decay of magnetization gave rise to a small activation volume of the order of 10-25m3, showing the promising of being the recording medium for future high density perpendicular recording. 相似文献
29.
Fluid flow in coupled free and porous domain, particularly when the porous medium is heterogeneous, is encountered in many hydro-environmental conditions, e.g., leakage from underground pipe, combined groundwater lake-subsurface interactions. One of the most difficult problems in the study of coupled flow behaviour has been the development of a universally applicable modelling scheme for combining the flow regimes. This is because the free/porous interfacial properties (e.g., shear-stress; velocity slip) that govern the coupled flow behaviour are difficult to determine experimentally under hydro-environmental conditions. On the other hand, the implications of various forms of heterogeneity in the porous media properties can be very different on the fluid-flow behaviour. Difficulties may also arise in direct coupling of the model equations that govern the fluid flow in the individual regions (e.g., Navier-Stokes for free-flow region and the Darcy's equation for the porous flow region). Consequently, models of coupled free and porous flow for hydro-environmental conditions are not very well developed at the moment. While there are some indications that fluids in coupled free and porous domains may circulate (i.e., development of flow cells), there is a lack of appropriate 3D analysis on how heterogeneities in porous media may affect such flow patterns. In this paper, we aim to analyse how porous media heterogeneity affects the dynamics of flow circulation in the porous side of a coupled free and porous domain. For this purpose, we analyse flow patterns in several model domains made up of two porous layers with differing permeabilities. The governing model equations are discretised and solved using the standard finite volume method on a staggered cell-centred mesh. The temporal discretisation is done using the explicit method. An in-house graphical user interface (GUI) has been created specifically to aid in the visualisation of otherwise complex flow patterns. The GUI contains many post-processing options and provides a comprehensive tool for the analysis of hydrodynamics and contaminant motion (not discussed in this paper) in coupled free and porous flow domains. This GUI is described in this paper briefly. The effects of altering the aspect ratio (i.e., multi-scale) of the domain on the coupled flow pattern have also been discussed. 相似文献
30.
This paper investigates Internet studies in two leading developing countries (i.e. China and India) and finds that the Chinese scholarly community relies on the discourse of liberation from the state as a form of critique, whereas Indian Internet studies question the discourse of modernization to contemplate about the success and failure factors of information and communication technologies in development. The difference generally reflects the academic responses to the development discourses embraced by the two governments. We suggest that Internet studies should not only respond to the realities but also transcend the contextual constraints to direct attention to the often neglected dimensions of development, which are to make actual impacts through allowing the people and the communities to define their own development discourses as well as building research institutions that are oriented to influence policy-making. 相似文献