全文获取类型
收费全文 | 1509篇 |
免费 | 15篇 |
专业分类
电工技术 | 14篇 |
综合类 | 1篇 |
化学工业 | 101篇 |
金属工艺 | 18篇 |
机械仪表 | 13篇 |
建筑科学 | 38篇 |
矿业工程 | 3篇 |
能源动力 | 24篇 |
轻工业 | 144篇 |
水利工程 | 7篇 |
石油天然气 | 4篇 |
无线电 | 113篇 |
一般工业技术 | 157篇 |
冶金工业 | 785篇 |
原子能技术 | 14篇 |
自动化技术 | 88篇 |
出版年
2022年 | 10篇 |
2021年 | 22篇 |
2018年 | 11篇 |
2016年 | 8篇 |
2015年 | 11篇 |
2014年 | 13篇 |
2013年 | 31篇 |
2012年 | 24篇 |
2011年 | 22篇 |
2010年 | 17篇 |
2009年 | 21篇 |
2008年 | 30篇 |
2007年 | 32篇 |
2006年 | 32篇 |
2005年 | 34篇 |
2004年 | 22篇 |
2003年 | 30篇 |
2002年 | 28篇 |
2001年 | 22篇 |
2000年 | 22篇 |
1999年 | 52篇 |
1998年 | 236篇 |
1997年 | 165篇 |
1996年 | 94篇 |
1995年 | 45篇 |
1994年 | 46篇 |
1993年 | 45篇 |
1992年 | 17篇 |
1991年 | 16篇 |
1990年 | 21篇 |
1989年 | 12篇 |
1988年 | 20篇 |
1987年 | 16篇 |
1986年 | 19篇 |
1985年 | 17篇 |
1984年 | 12篇 |
1983年 | 12篇 |
1982年 | 8篇 |
1981年 | 14篇 |
1980年 | 19篇 |
1979年 | 7篇 |
1978年 | 12篇 |
1977年 | 24篇 |
1976年 | 43篇 |
1975年 | 15篇 |
1974年 | 10篇 |
1973年 | 10篇 |
1972年 | 10篇 |
1970年 | 8篇 |
1926年 | 6篇 |
排序方式: 共有1524条查询结果,搜索用时 15 毫秒
101.
Gabriela González Castro Hassan Ugail Philip Willis Ian Palmer 《The Visual computer》2008,24(3):213-225
Computer-aided geometric design is an area where the improvement of surface generation techniques is an everlasting demand,
since faster and more accurate geometric models are required. Traditional methods for generating surfaces were initially mainly
based upon interpolation algorithms. Recently, partial differential equations (PDE) were introduced as a valuable tool for
geometric modelling, since they offer a number of features from which these areas can benefit. This work summarizes the uses
given to PDE surfaces as a surface generation technique together with some other applications to computer graphics. 相似文献
102.
CV Ward MG Leakey B Brown F Brown J Harris A Walker 《Canadian Metallurgical Quarterly》1999,36(1):69-95
New fossils discovered south of the Turkwel River in northern Kenya include an associated metacarpal, capitate, hamate, lunate, pedal phalanx, mandibular fragment, and teeth. These fossils probably date to around 3.5 m.y.a. Faunal information suggests that the environment at South Turkwel was predominantly bushland. The mandibular and dental remains are fragmentary, but the postcranial fossils are informative. Comparisons with Australopithecus, modern human, chimpanzee and gorilla hand bones suggest that the Turkwel hominid was most like Australopithecus afarensis and A. africanus. Carpometacarpal articulations are intermediate between those of modern humans and African apes, suggesting enhanced gripping capabilities compared with extant apes. The hamulus was strikingly large, similar in proportion only to Neandertals and some gorillas, suggesting the presence of powerful forearms and hands. There are no indicators of adaptations to knuckle-walking or suspensory locomotion in the hand, and the pedal phalanx suggests that this hominid was habitually bipedal. 相似文献
103.
104.
In this work the design and construction of a simple fiber-optic pressure sensor based on the principle of frustrated-total-internal-reflection in a fiber cut beyond the critical angle are described. The characteristic of the device is obtained and compared with the predictions of a simple theory. Modifications to alter its sensitivity by the use of different wavelengths and fiber cut angle are discussed. 相似文献
105.
106.
Hounsell N.B. Shrestha B.P. Head J.R. Palmer S. Bowen T. 《Intelligent Transport Systems, IET》2008,2(3):193-200
London has a long history of successful schemes for bus priority at traffic signals. Recently, transport for London (TfL) has procured a modern automatic vehicle location (AVL) system for bus fleet management, passenger information and bus priority. The new system is known as iBUS and is based on Global Positioning System (GPS) and supporting technologies for bus location. The system eliminates the need for on-street hardware for detecting buses and provides more flexibility and opportunity for using bus detectors. However, bus location based on this system is less accurate than location based on fixed infrastructure (e.g. beacons) and could result in reduced benefits from bus priority. This paper first summarises how bus priority at traffic signals works within iBUS, and then explores the effects of GPS locational errors on bus priority benefits. This is followed by a discussion of opportunities available in the context of iBUS to build an even more efficient and beneficial bus priority system by taking advantage of its cost-effective multiple detection capabilities. The paper is based on various studies carried out by the Transportation Research Group (TRG) at the University of Southampton for TfL. 相似文献
107.
People often coordinate their actions with sequences that exhibit temporal variability and unfold at multiple periodicities. We compared oscillator- and timekeeper-based accounts of temporal coordination by examining musicians' coordination of rhythmic musical sequences with a metronome that gradually changed rate at the end of a musical phrase (Experiment 1) or at the beginning of a phrase (Experiment 2). The rhythms contained events that occurred at the same periodic rate as the metronome and at half the period. Rate change consisted of a linear increase or decrease in intervals between metronome onsets. Musicians coordinated their performances better with a metronome that decreased than increased in tempo (as predicted by an oscillator model), at both beginnings and ends of musical phrases. Model performance was tested with an oscillator period or timekeeper interval set to the same period as the metronome (1:1 coordination) or half the metronome period (2:1 coordination). Only the oscillator model was able to predict musicians' coordination at both periods. These findings suggest that coordination is based on internal neural oscillations that entrain to external sequences. (PsycINFO Database Record (c) 2011 APA, all rights reserved) 相似文献
108.
The influence of a linear loading profile on a slitted bow-tie antenna is discussed. Improvements of the radiation characteristics are achieved by bending the antenna. Simulations and measurements show a S 11 10 dB bandwidth of more than 8:1 and a gain larger than 4.5 dBi. A complete antenna system matched to 50 Ω is proposed 相似文献
109.
Phase Relationships and Physical Properties of Homologous Compounds in the Zinc Oxide-Indium Oxide System 总被引:1,自引:0,他引:1
Toshihiro Moriga Doreen D. Edwards Thomas O. Mason George B. Palmer Kenneth R. Poeppelmeier Jon L. Schindler Carl R. Kannewurf Ichiro Nakabayashi 《Journal of the American Ceramic Society》1998,81(5):1310-1316
Equilibrium phase relationships in the ZnO-In2 O3 system were determined between 1100° and 1400°C using solid-state reaction techniques and X-ray diffractometry. In addition to ZnO and In2 O3 , nine homologous compounds, Zn k In2 O k +3 (where k = 3, 4, 5, 6, 7, 9, 11, 13, and 15), were observed. Electrical conductivity and diffuse reflectance of the k = 3, 4, 5, 7 and 11 members were measured before and after annealing at 400°C for 1 h under forming gas (4%2 -96% N2 ). Room-temperature conductivity increased as k decreased, because of increased carrier concentration as well as increased mobility. In general, transparency in the wavelength range of 450-900 nm increased as k increased. Reduction in forming gas resulted in increased conductivity and reduced transparency for all compounds measured. The highest room-temperature conductivity measured, 270 S/cm, was that of reduced Zn3 In2 O6 . 相似文献
110.
A high-efficiency ground heat exchanger has been developed for use with ground-source heat pumps. The exchanger is made of copper tubing, shaped in the form of a spiral, which can be installed in a vertical borehole backfilled with sand. Thermal performance of a full-scale prototype indicated that this heat exchanger can achieve very high heat extraction rates if subfreezing operating temperatures are used. For most soil types cyclic freezing and thawing is not a problem; however, for the sensitive Leda clay in which the prototype tests were conducted, substantial settlement occurred after the first freeze-thaw cycle owing to initial collapse of the soil structure. 相似文献