全文获取类型
收费全文 | 14156篇 |
免费 | 419篇 |
国内免费 | 34篇 |
专业分类
电工技术 | 198篇 |
综合类 | 21篇 |
化学工业 | 2186篇 |
金属工艺 | 275篇 |
机械仪表 | 326篇 |
建筑科学 | 536篇 |
矿业工程 | 27篇 |
能源动力 | 262篇 |
轻工业 | 1784篇 |
水利工程 | 127篇 |
石油天然气 | 31篇 |
武器工业 | 1篇 |
无线电 | 1464篇 |
一般工业技术 | 2023篇 |
冶金工业 | 3459篇 |
原子能技术 | 167篇 |
自动化技术 | 1722篇 |
出版年
2023年 | 53篇 |
2022年 | 131篇 |
2021年 | 260篇 |
2020年 | 141篇 |
2019年 | 200篇 |
2018年 | 239篇 |
2017年 | 227篇 |
2016年 | 293篇 |
2015年 | 181篇 |
2014年 | 323篇 |
2013年 | 661篇 |
2012年 | 518篇 |
2011年 | 676篇 |
2010年 | 546篇 |
2009年 | 514篇 |
2008年 | 572篇 |
2007年 | 579篇 |
2006年 | 453篇 |
2005年 | 457篇 |
2004年 | 373篇 |
2003年 | 341篇 |
2002年 | 313篇 |
2001年 | 315篇 |
2000年 | 304篇 |
1999年 | 337篇 |
1998年 | 1022篇 |
1997年 | 644篇 |
1996年 | 480篇 |
1995年 | 360篇 |
1994年 | 293篇 |
1993年 | 304篇 |
1992年 | 164篇 |
1991年 | 144篇 |
1990年 | 153篇 |
1989年 | 152篇 |
1988年 | 146篇 |
1987年 | 115篇 |
1986年 | 123篇 |
1985年 | 161篇 |
1984年 | 112篇 |
1983年 | 101篇 |
1982年 | 75篇 |
1981年 | 100篇 |
1980年 | 92篇 |
1979年 | 94篇 |
1978年 | 48篇 |
1977年 | 112篇 |
1976年 | 162篇 |
1975年 | 59篇 |
1973年 | 62篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Martin C.A. Van Zuijlen 《Sequential Analysis》2013,32(2):159-162
A generalization to the non-i.i.d. case of an inequality for the empirical df. due to Mason (1981) is proved 相似文献
992.
993.
Tammy Ben-Yaacov Tommy Ive Chris G. Van de Walle Umesh K. Mishra James S. Speck Steven P. Denbaars 《Journal of Electronic Materials》2010,39(5):608-611
We investigated the properties of indium-doped zinc oxide layers grown by metalorganic chemical vapor deposition on semi-insulating
GaN(0001) templates. Specular and transparent films were grown with n-type carrier concentrations up to 1.82 × 1019 cm−3 as determined by Hall measurements, and all In-doped films had carrier concentrations significantly higher than that of a
comparable undoped film. For low In flows, the carrier concentration increased accordingly with trimethyl-indium (TMIn) flow
until a maximum carrier concentration of 1.82 × 1019 cm−3 was realized. For higher In flows, the carrier concentration decreased with increasing TMIn flow rate. Sheet resistance as
low as 185 Ω/sq was achieved for the In-doped films, which is a significant decrease from that of a comparable undoped ZnO
film. Our n-type doping studies show that In is an effective dopant for controlling the n-type conductivity of ZnO. 相似文献
994.
<正>法国珠宝商、Jean Dinh Van,是世界知名的珠宝商卡地亚(Cartier)的学徒。1965年,Dinh Van在巴黎推出其同名珠宝品牌时,他就想创建一个集人性化、活泼、有性格的珠宝品牌,而最重要的是这些珠宝要能体现出现代的元素。正是基于这种理念,Stefarno Tordiglione Design设计了在香港国际金融中心和利园商场两家当代珠宝店。 相似文献
995.
Takanori Sugawara Massimo Sarotto Alexey Stankovskiy Gert Van den Eynde 《Annals of Nuclear Energy》2011
The XT-ADS, an accelerator-driven system for an experimental demonstration, has been investigated in the framework of IP EUROTRANS FP6 project. In this study, the sensitivity and uncertainty analyses were performed to comprehend the reliability of the XT-ADS neutronic design. 相似文献
996.
Stephanie Lansing Jay F. Martin Raúl Botero Botero Tatiana Nogueira da Silva Ederson Dias da Silva 《Biomass & bioenergy》2010,34(12):1711-1720
A nine-month co-digestion investigation was conducted in Costa Rica to optimize animal wastewater treatment, renewable energy production, and fertilizer creation using 12 Taiwanese-model, plug-flow digesters (250 L each) constructed of tubular polyethylene and PVC piping, operating without mechanical or heating components. The experiment tested three replications of four treatment groups: the control (T0), which contained only swine manure, and T2.5, T5, and T10, which contained 2.5%, 5%, and 10% used cooking grease (by volume) combined with swine manure.T2.5 had the greatest methane production (45 L d?1), a 124% increase from the control. No adverse effects were observed from co-digesting 2.5% grease in terms of organic matter removal, pathogen reduction, grease removal, and pH. Chemical oxygen demand (COD) was reduced 94.7% to 1.96 g L?1, fecal coliforms and Escherichia coli were reduced 99.2 and 97.1%, respectively, and grease removal was 99.9%. The average effluent pH (7.05) and alkalinity in T2.5 was within the optimal range for methanogens and increased significantly during the nine-month experiment, likely due to adaptation of the methanogenic organisms to the influent grease concentrations. Total nitrogen concentration decreased 34.0%, and NH4-N increased 97.1% during digestion in T2.5, with no significant differences between T2.5 and T0. There was less phosphorus reduction with co-digestion, with 181 mg g?1 of total phosphorus (TP) in T2.5 and only 90.6 mg g?1 of TP in T0, resulting in lower N:P ratios in the grease treatment groups due to the greater concentration of phosphorus in the effluent. 相似文献
997.
从社会、产品和应用的角度,举例说明未来数年照明的"热点"。从社会的角度,说明可持续发展以及相关节能产品和应用设计的持续重要性。要更加关注完全无废料的设计,即"从摇篮到摇篮"(from cradle to cradle)的设计。从产品的角度,说明固态将成为许多产品应用的标准。在固态照明方面,由于所提供的数据常常有误而令新用户不满,因此向固态照明转变的脚步会放缓。若有效控制固态照明中的眩光,须有新型的光学设计。目前的评价体系,是通过经验方法获得,完全不适用于固态照明环境,因此需要全新的眩光评价体系。普通室内照明的显色性和色表规格,过去以白炽灯为基准,现在须设定严格的新标准。在应用方面,若要达到非视觉生物效应,智能动态照明也要成为一种标准。我们将看到,为减少因生物钟失调而出现的问题,会广泛应用光学治疗。在固定路灯方面,随着汽车系统本身的发展,不会再优先考虑物体的能见度。我们需要的不再是路灯亮度概念,而是更加三维的概念。若综合考虑中间视觉的所有效果,路灯光源的最有效光谱应该偏暖白光。老年人会丧失短波长视觉能力,是其中的主要原因。 相似文献
998.
999.
N. Smets S. Van Damme D. De Wilde G. Weyns J. Deconinck 《Journal of Applied Electrochemistry》2007,37(3):315-324
Pulse Electrochemical Machining (PECM) is a manufacturing process which provides an economical and effective method for machining
hard materials into complex shapes. One important drawback of ECM is the lack of quantitative simulation software to predict
the tool shape and machining parameters necessary to produce a given work-piece profile. Calculating temperature distributions
in the system allows more accurate simulations, as well as the determination of the thermal limits of the system. In this
paper temperature transients over multiple pulses are calculated. It is found that the way the system is modeled has a great
impact on the temperature evolution in the thermal boundary layer. The presence of massive electrodes introduces extra time
scales which may not be negligible. It is advantageous to identify the thermal time scales in the system, to see whether the
heat produced during separate pulses will accumulate or not during the process. The occurring thermal time scales in the system
are discussed in detail. 相似文献
1000.
Visualization is often invaluable to understand the behavior of optimization algorithms, identify their bottlenecks or pathological
behaviors, and suggest remedial techniques. Yet developing visualizations is often a tedious activity requiring significant
time and expertise. This paper presents a framework for the visualization of constraint-based local search (CBLS) algorithms.
Given a high-level model and a declarative visualization specification, the CBLS visualizer systematically produces animations
to visualize constraints and objectives, violations, and conflicts, as well as the temporal behavior of these measures. The
visualization specification is declarative and typically composed of a triple (what,where,how) indicating what to display, where, and with which graphical objects. The visualizer architecture is compositional and extensible.
It provides building blocks which can be assembled freely by the user and focuses almost exclusively on static aspects, the
dynamic aspects being automated by the use of invariants. The paper highlights various functionalities of the visualizer and
describes a blueprint for its implementation. 相似文献