全文获取类型
收费全文 | 1243篇 |
免费 | 101篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 12篇 |
化学工业 | 232篇 |
金属工艺 | 55篇 |
机械仪表 | 96篇 |
建筑科学 | 19篇 |
能源动力 | 80篇 |
轻工业 | 117篇 |
水利工程 | 4篇 |
无线电 | 239篇 |
一般工业技术 | 270篇 |
冶金工业 | 61篇 |
原子能技术 | 32篇 |
自动化技术 | 132篇 |
出版年
2024年 | 1篇 |
2023年 | 25篇 |
2022年 | 25篇 |
2021年 | 55篇 |
2020年 | 34篇 |
2019年 | 31篇 |
2018年 | 48篇 |
2017年 | 55篇 |
2016年 | 55篇 |
2015年 | 45篇 |
2014年 | 72篇 |
2013年 | 100篇 |
2012年 | 97篇 |
2011年 | 98篇 |
2010年 | 70篇 |
2009年 | 70篇 |
2008年 | 76篇 |
2007年 | 39篇 |
2006年 | 45篇 |
2005年 | 36篇 |
2004年 | 52篇 |
2003年 | 34篇 |
2002年 | 26篇 |
2001年 | 21篇 |
2000年 | 26篇 |
1999年 | 16篇 |
1998年 | 28篇 |
1997年 | 22篇 |
1996年 | 11篇 |
1995年 | 2篇 |
1994年 | 6篇 |
1993年 | 4篇 |
1992年 | 5篇 |
1991年 | 2篇 |
1990年 | 4篇 |
1989年 | 5篇 |
1988年 | 1篇 |
1987年 | 4篇 |
1986年 | 1篇 |
1981年 | 1篇 |
1974年 | 1篇 |
排序方式: 共有1349条查询结果,搜索用时 22 毫秒
71.
Cesari V Colautti P Magrin G De Nardo L Baek WY Grosswendt B Alkaa A Khamphan C Ségur P Tornielli G 《Radiation protection dosimetry》2002,99(1-4):337-342
This paper illustrates a tissue-equivalent proportional counter designed to have high gas gain and good energy resolution at nanometric simulated site sizes. Microdosimetric neutron and gamma spectra were measured in dimethyl ether and in propane-based tissue-equivalent gas mixture down to 35 nm. The comparison of experimental data with the results of Monte Carlo calculations shows a satisfactory agreement. 相似文献
72.
Web image retrieval using majority-based ranking approach 总被引:1,自引:0,他引:1
Web image retrieval has characteristics different from typical content-based image retrieval; web images have associated textual cues. However, a web image retrieval system often yields undesirable results, because it uses limited text information such as surrounding text, URLs, and image filenames. In this paper, we propose a new approach to retrieval, which uses the image content of retrieved results without relying on assistance from the user. Our basic hypothesis is that more popular images have a higher probability of being the ones that the user wishes to retrieve. According to this hypothesis, we propose a retrieval approach that is based on a majority of the images under consideration. We define four methods for finding the visual features of majority of images; (1) majority-first method, (2) centroid-of-all method, (3) centroid-of-top K method, and (4) centroid-of-largest-cluster method. In addition, we implement a graph/picture classifier for improving the effectiveness of web image retrieval. We evaluate the retrieval effectiveness of both our methods and conventional ones by using precision and recall graphs. Experimental results show that the proposed methods are more effective than conventional keyword-based retrieval methods. 相似文献
73.
Proposed is an all-fibre retro-reflector realised via shaping a fibre end into a right-angled cone for a pump reflector in cladding-pumped fibre lasers. The conical-shaped fibre-optic retro-reflector allows folded, total internal reflections for pump beams that propagate in the inner cladding of a double-clad fibre. The proposed scheme was applied to a cladding-pumped ytterbium-doped fibre laser and readily achieved over 55% of reflection for the unabsorbed pump throughput, thereby generating 29% more signal output power than without the pump retro-reflector 相似文献
74.
Youn Tae Kim Chi Hoon Jun Jong-Tae Baek Hyung Joun Yoo Sang-Koo Chung 《Journal of Electronic Materials》1995,24(10):1413-1417
In this study, we have investigated sensitivities of the ion implanted silicon wafers processed by rapid thermal annealing
(RTA), which can reveal the variation of sheet resistance as a function of annealing temperature as well as implantation parameters.
All the wafers were sequentially implanted by the arsenic or phosphorous implantations at 40, 80, and 100 keV with the dose
level of 1014 to 2 × 1016 ions/cm2. Rapid thermal annealing was carried out for 10 s by the infrared irradiation at a temperature between 850 and 1150°C in
the nitrogen ambient. The activated wafer was characterized by the measurements of the sheet resistance and its uniformity
mapping. The values of sensitivities are determined from the curve fitting of the experimental data to the fitting equation
of correlation between the sheet resistance and process variables. From the sensitivity values and the deviation of sheet
resistance, the optimum process conditions minimizing the effects of straggle in process parameters are obtained. As a result,
a strong dependence of the sensitivity on the process variables, especially annealing temperatures and dose levels is also
found. From the sensitivity analysis of the 10 s RTA process, the optimum values for the implant dose and annealing temperature
are found to be in the range of 1016 ions/cm2 and 1050-1100°C, respectively. The sensitivity analysis of sheet resistance will provide valuable data for accurate activation
process, offering a guideline for dose monitoring and calibration of ion implantation process. 相似文献
75.
B.-M.?HanEmail author H.-J.?Kim S.-T.?Baek 《Electrical Engineering (Archiv fur Elektrotechnik)》2004,86(5):285-291
This paper proposes a soft-switching CSI for a photovoltaic power system which has an H-type switched-capacitor module composed of two semiconductor switches, two diodes and an L-C resonant circuit. The operation of the proposed system was analyzed using a theoretical approach with equivalent circuits and verified by computer simulations using a simulation program with integrated circuit emphasis and experimental work with a hardware prototype. The proposed system could be effectively applied to the power converter of a photovoltaic power system interconnected with an a.c. power system. 相似文献
76.
Seongmin?Baek Seungyong?Lee Email author Gerard Jounghyun?Kim 《The Visual computer》2003,19(4):222-242
Virtual reality (VR) has emerged as one of the important and effective tools for education and training. Most VR-based training systems are situation based, where the trainees are trained for discrete decision making in special situations presented by the VR environments. In contrast, this paper discusses the application of VR to a different class of training, for learning free motion, often required in sports and the arts. We propose a VR-based motion-training framework that contains an intuitive motion-guiding interface, posture-oriented motion retargeting, and an evaluation and advice scheme for corrective feedback. Applications of the proposed framework to simple fencing training and a dance imitation game are demonstrated. 相似文献
77.
Wonihl?ChoEmail author Seung-Ho?Lee Youngsoon?Baek Seong-Min?Lee Young?Tai?Kho 《Korean Journal of Chemical Engineering》2003,20(2):230-234
Catalytic combustion for applying heat shrink sleeves (HSS) to a pipeline in KOGAS was investigated. We used a low temperature
catalytic combustor in order to place HSS in the conduit. The surface temperature of the catalytic combustor maintained the
conditions at which HSS can become well-adhesive at the conduit. Therefore, the automatic HSS construction provided the chance
to establish gas pipeline safety by an automatic catalytic combustor device. 相似文献
78.
In a fin-tube heat exchanger the contact between fin collar and tube surface is obtained through mechanical expansion of tubes. Since the interfaces between the tubes and fins consist partially of metal-to-metal contact and partially of air, the features of heat transfer through the contact interfaces have not been fully investigated. The present study aims at the development of a new tool including an experiment and a numerical calculation for the estimation of the thermal contact conductance between the fin collar and tube surface, and pursues the evaluation of the factors affecting the thermal contact conductance in a fin-tube heat exchanger. Heat exchangers fabricated for the current study have been put to the test for heat balance in a vacuum chamber with water as an internal fluid. And a finite difference numerical scheme has been used for the data reduction of the experimental data to evaluate the thermal contact conductance. Fin-tube heat exchangers employed in the current research are of tube diameter of 7 mm with different tube expansion ratios, fin spacings, and fin types. The results of the present study imply that these parameters as well as hydrophilic fin coating have a significant effect on the thermal contact conductance. It has been discovered that the portion of the thermal contact resistance is not negligible compared with the total thermal resistance in a fin-tube heat exchanger, and this means that in order to reduce the thermal contact resistance thoughtful care should be taken in fabricating heat exchangers. 相似文献
79.
Physicochemical characterization of diclofenac sodium-loaded poloxamer gel as a rectal delivery system with fast absorption 总被引:1,自引:0,他引:1
Yong CS Sah H Jahng Y Chang HW Son JK Lee SH Jeong TC Rhee JD Baek SH Kim CK Choi HG 《Drug development and industrial pharmacy》2003,29(5):545-553
Rectal poloxamer gel systems composed of poloxamers and bioadhesive polymers were easy to administer to the anus and were mucoadhesive to the rectal tissues without leakage after the dose. However, a poloxamer gel containing diclofenac sodium could not be developed using bioadhesive polymers, since the drug was precipitated in this preparation. To develop a poloxamer gel using sodium chloride instead of bioadhesive polymers, the physicochemical properties such as gelation temperature, gel strength, and bioadhesive force of various formulations composed of diclofenac sodium, poloxamers, and sodium chloride were investigated. Furthermore, the pharmacokinetic study of diclofenac sodium delivered by the poloxamer gel was performed. Diclofenac sodium significantly increased the gelation temperature and weakened the gel strength and bioadhesive force, while sodium chloride did the opposite. The poloxamer gels with less than 1.0% sodium chloride, in which the drug was not precipitated, were inserted into the rectum without difficulty and leakage, and were retained in the rectum of rats for at least 6 hr. Furthermore, poloxamer gel gave significantly higher initial plasma concentrations and faster Tmax of diclofenac sodium than did solid suppository, indicating that drug from poloxamer gel could be absorbed faster than that from the solid one in rats. Our results suggested that a rectal poloxamer gel system with sodium chloride and poloxamers was a more physically stable, convenient, and effective rectal dosage form for diclofenac sodium. 相似文献
80.
Aluminum nitride (AlN) films were deposited using pulsed laser deposition (PLD) onto sapphire (0001) substrates with varying processing conditions (temperature, pressure, and laser fluence). We have studied the dependence of optical properties, structural properties and their correlations for these AlN films. The optical transmission spectra of the produced films were measured, and a numerical procedure was applied to accurately determine the optical constants for films of non-uniform thickness. The microstructure and texture of the films were studied using various X-ray diffraction techniques. The real part of the refractive index was found to not vary significantly with processing parameters, but absorption was found to be strongly dependent on the deposition temperature and the nitrogen pressure in the deposition chamber. We report that low optical absorption, textured polycrystalline AlN films can be produced by PLD on sapphire substrates at both low and high laser fluence using a background nitrogen pressure of 6.0 × 10− 2 Pa (4.5 × 10− 4 Torr) of 99.9% purity. 相似文献