全文获取类型
收费全文 | 1433篇 |
免费 | 46篇 |
专业分类
电工技术 | 21篇 |
化学工业 | 145篇 |
金属工艺 | 29篇 |
机械仪表 | 17篇 |
建筑科学 | 60篇 |
矿业工程 | 27篇 |
能源动力 | 30篇 |
轻工业 | 125篇 |
水利工程 | 15篇 |
石油天然气 | 22篇 |
武器工业 | 1篇 |
无线电 | 205篇 |
一般工业技术 | 170篇 |
冶金工业 | 246篇 |
原子能技术 | 4篇 |
自动化技术 | 362篇 |
出版年
2023年 | 9篇 |
2022年 | 10篇 |
2021年 | 23篇 |
2020年 | 19篇 |
2019年 | 28篇 |
2018年 | 28篇 |
2017年 | 42篇 |
2016年 | 46篇 |
2015年 | 35篇 |
2014年 | 54篇 |
2013年 | 77篇 |
2012年 | 60篇 |
2011年 | 104篇 |
2010年 | 87篇 |
2009年 | 72篇 |
2008年 | 86篇 |
2007年 | 84篇 |
2006年 | 76篇 |
2005年 | 63篇 |
2004年 | 59篇 |
2003年 | 54篇 |
2002年 | 31篇 |
2001年 | 29篇 |
2000年 | 13篇 |
1999年 | 22篇 |
1998年 | 20篇 |
1997年 | 21篇 |
1996年 | 56篇 |
1995年 | 26篇 |
1994年 | 14篇 |
1993年 | 16篇 |
1992年 | 13篇 |
1991年 | 4篇 |
1990年 | 7篇 |
1989年 | 6篇 |
1988年 | 9篇 |
1987年 | 10篇 |
1986年 | 7篇 |
1985年 | 11篇 |
1984年 | 10篇 |
1983年 | 5篇 |
1982年 | 5篇 |
1981年 | 5篇 |
1980年 | 3篇 |
1979年 | 3篇 |
1978年 | 4篇 |
1977年 | 5篇 |
1976年 | 5篇 |
1973年 | 1篇 |
1958年 | 1篇 |
排序方式: 共有1479条查询结果,搜索用时 15 毫秒
11.
Xing Gu Shariar Sabuktagin Ali Teke Daniel Johnstone Hadis Morkoç Bill Nemeth Jeff Nause 《Journal of Materials Science: Materials in Electronics》2004,15(6):373-378
ZnO is a highly efficient photon emitter, and has optical and piezoelectric properties that are attractive for a variety of applications in sensors and potentially optoelectronic devices such as emitters. Due to its identical stacking order and close lattice match to GaN, it is also being developed as a substrate material for GaN epitaxy. However, the surface finish of the ZnO is such that much of the damage induced by sawing and follow up mechanical polishing remains. We developed a thermal treatment method to eliminate surface damage on the 0 face of ZnO (0 0 0 1) to prepare it for epitaxial growth. Atomic force microscopy images of ZnO (0 0 0 1) annealed at 1050 °C for 3 h etc. show that residual scratches from mechanical polishing are removed and atomically flat, terrace-like surfaces are attained. In addition, low-temperature photoluminescence and high-resolution X-ray diffraction measurements have been employed to investigate the effect of annealing on ZnO substrates. 相似文献
12.
基于电子设备的处理器系统设计人员经常在选择最佳电源架构时遇到困难。有时最佳的解决方案是插入式电源,而有时采用分立的元件组成的电源才是最佳解决方案。选择插入式电源解决方案相对来说比较直接,但对于缺乏电源设计经验的数字设计人员来说,设计一个分立电源解决方案可能会使他望而却步。大多 DC/DC 电源控制 IC 供应商均可提供有助于电路设计的详细辅助材料。但是,在开始电源设计之前,设计人员必须选择正确的拓扑。本文将介绍以下方法,来帮助为某些用于MCU、DSP及基于FPGA 的电子产品的最常用结构选择正确的电源拓扑。线性调节… 相似文献
13.
14.
Johnson J 《Environmental science & technology》1996,30(11):476A-477A
Science. 相似文献
15.
Johnson J 《Environmental science & technology》1996,30(7):286A
Government. 相似文献
16.
Johnson J 《Environmental science & technology》1996,30(6):243A
Science. 相似文献
17.
Lawrence E. Holloway Yu Gong Jeff Ashley 《Mathematics and computers in simulation》2006,70(5-6):275-286
This paper introduces the concepts of state observability and condition observability for condition systems, a class of systems composed of discrete state components which interact via discrete binary signals called conditions. Given a set of externally observed conditions, state observability implies that the state of the system can be determined from the observations, and condition observability implies that all unobserved input and output conditions of the system can be determined from the observations. In this paper, we present a class of systems which is state observable and condition observable. We present a method to synthesize an observer system to provide state and condition signal estimates for a single component subsystem. 相似文献
18.
Name resolution using the Domain Name System (DNS) is integral to today’s Internet. The resolution of a domain name is often dependent on namespace outside the control of the domain’s owner. In this article we review the DNS protocol and several DNS server implementations. Based on our examination, we propose a formal model for analyzing the name dependencies inherent in DNS. Using our name dependency model we derive metrics to quantify the extent to which domain names affect other domain names. It is found that under certain conditions, more than half of the queries for a domain name are influenced by namespaces not expressly configured by administrators. This result serves to quantify the degree of vulnerability of DNS due to dependencies that administrators are unaware of. When we apply metrics from our model to production DNS data, we show that the set of domains whose resolution affects a given domain name is much smaller than previously thought. However, behaviors such as using cached addresses for querying authoritative servers and chaining domain name aliases increase the number and diversity of influential domains, thereby making the DNS infrastructure more vulnerable. 相似文献
19.
Arman Bonakdarpour George D. Vernstrom Alison K. Schmoeckel Jeff R. Dahn 《Electrochimica acta》2007,53(2):688-694
We report on extensive measurements of oxygen reduction activity of Pt and Pt-Co-Mn electrocatalysts using the rotating ring-disk electrode (RRDE) method. The electrocatalysts were prepared by sputtering from Pt or Pt, Co and Mn targets onto 3M's nano-structured thin film support (NSTF) structures. The area specific activity of Pt/NSTF, measured in 0.1 M HClO4 and at room temperature, is similar to that of bulk Pt. The area specific measurements show a 20 mV reduction in the Pt-Co-Mn/NSTF overpotential compared to Pt/NSTF. The corresponding kinetic gain in the area specific activity of the ternary alloy is about a factor of two. This ORR enhancement factor observed in the ternary Pt-Co-Mn/NSTF by RRDE measurements is similar to the results obtained in 50 cm2 H2/air fuel cells. 相似文献
20.
Shampa Kandoi Jeff Greeley Marco A. Sanchez-Castillo Steven T. Evans Amit A. Gokhale James A. Dumesic Manos Mavrikakis 《Topics in Catalysis》2006,37(1):17-28
A microkinetic model for methanol decomposition on platinum is presented. The model incorporates competitive decomposition
pathways, beginning with both O–H and C–H bond scission in methanol, and uses results from density functional theory (DFT)
calculations [Greeley and Mavrikakis, J. Am. Chem. Soc. 124 (2002) 7193, Greeley and Mavrikakis, J. Am. Chem. Soc. 126 (2004)
3910]. Results from reaction kinetics experiments show that the rate of H2 production increases with increasing temperature and methanol concentration in the feed and is only nominally affected by
the presence of CO or H2 with methanol. The model, based on the values of binding energies, pre-exponential factors and activation energy barriers
derived from first principles calculations, accurately predicts experimental reaction rates and orders. The model also gives
insight into the most favorable reaction pathway, the rate-limiting step, the apparent activation energy, coverages, and the
effects of pressure. It is found that the pathway beginning with the C–H bond scission (CH3OH→H2COH→HCOH→CO) is dominant compared with the path beginning with O–H bond scission. The cleavage of the first C–H bond in methanol
is the rate-controlling step. The surface is highly poisoned by CO, whereas COH appears to be a spectator species. 相似文献