全文获取类型
收费全文 | 3416篇 |
免费 | 73篇 |
国内免费 | 7篇 |
专业分类
电工技术 | 104篇 |
综合类 | 1篇 |
化学工业 | 665篇 |
金属工艺 | 122篇 |
机械仪表 | 42篇 |
建筑科学 | 50篇 |
能源动力 | 80篇 |
轻工业 | 276篇 |
水利工程 | 4篇 |
石油天然气 | 4篇 |
无线电 | 355篇 |
一般工业技术 | 602篇 |
冶金工业 | 914篇 |
原子能技术 | 113篇 |
自动化技术 | 164篇 |
出版年
2023年 | 15篇 |
2022年 | 40篇 |
2021年 | 64篇 |
2020年 | 16篇 |
2019年 | 25篇 |
2018年 | 38篇 |
2017年 | 49篇 |
2016年 | 52篇 |
2015年 | 31篇 |
2014年 | 70篇 |
2013年 | 111篇 |
2012年 | 103篇 |
2011年 | 138篇 |
2010年 | 86篇 |
2009年 | 112篇 |
2008年 | 113篇 |
2007年 | 118篇 |
2006年 | 96篇 |
2005年 | 104篇 |
2004年 | 103篇 |
2003年 | 100篇 |
2002年 | 90篇 |
2001年 | 63篇 |
2000年 | 59篇 |
1999年 | 65篇 |
1998年 | 382篇 |
1997年 | 216篇 |
1996年 | 155篇 |
1995年 | 95篇 |
1994年 | 122篇 |
1993年 | 97篇 |
1992年 | 42篇 |
1991年 | 45篇 |
1990年 | 49篇 |
1989年 | 42篇 |
1988年 | 41篇 |
1987年 | 35篇 |
1986年 | 33篇 |
1985年 | 43篇 |
1984年 | 15篇 |
1983年 | 20篇 |
1982年 | 27篇 |
1981年 | 14篇 |
1980年 | 16篇 |
1979年 | 18篇 |
1978年 | 14篇 |
1977年 | 14篇 |
1976年 | 43篇 |
1975年 | 13篇 |
1972年 | 9篇 |
排序方式: 共有3496条查询结果,搜索用时 796 毫秒
971.
Aida T Yamazaki A Akutsu M Ono T Kanno A Hoshina TA Ota M Watanabe M Sato Y Smith RL Inomata H 《The Review of scientific instruments》2007,78(11):115111
A laser-Doppler vibrometer was used to measure the vibration of a vibrating tube densimeter for measuring P-V-T data at high temperatures and pressures. The apparatus developed allowed the control of the residence time of the sample so that decomposition at high temperatures could be minimized. A function generator and piezoelectric crystal was used to excite the U-shaped tube in one of its normal modes of vibration. Densities of methanol-water mixtures are reported for at 673 K and 40 MPa with an uncertainty of 0.009 g/cm3. 相似文献
972.
As the Internet has been commonly used in our everyday lives, we have been able to obtain large amount of information from
it, whereas we have simultaneously had a problem that it is difficult to find proper information for us from the large amount
of information on the Web. Although many information recommendation methods have been proposed in order to solve this problem,
most recommendation methods are based on a large amount of user’s personal data such as operation log, schedule, etc – which
means that we have to manage a large amount of personal data in the system in order to provide proper information to users,
and it would be expensive to construct such a system.
With this background, in this study, against aiming to construct a sophisticated information recommendation system based on
large personal data, we propose a handy and not expensive information recommendation method, working beside a normal search
engine, which does not depend on user profile data, but on topical news information.
相似文献
Ichiro KobayashiEmail: |
973.
Junko Yotani Sashiro Uemura Takeshi Nagasako Hiroyuki Kurachi Takehiro Nakao Masaaki Ito Akira Sakurai Hideo Shimoda Tomotaka Ezaki Kazuhiko Fukuda Yahachi Saito 《Journal of the Society for Information Display》2009,17(4):361-367
Abstract— A high‐luminance 1.8‐mm‐pixel‐pitch CNT‐FED for color character displays has been developed. The display panel has 32 × 256 color pixels, and the subpixel size is 0.6 × 1.8 mm. The display panel can provide good visibility when installed even in outdoor locations. The power consumption is low enough for the display to be battery driven. The practical application is the display of important messages regarding the evacuation from disaster areas, even under emergent no‐power conditions similar to the messages on vending machines. 相似文献
974.
Marenori Kawamura Takumi Sano Susumu Sato 《Journal of the Society for Information Display》2009,17(10):833-839
Abstract— A two‐dimensional cell‐parameter measurement for determining the pretilt angle in addition to both the cell thickness and twist angle of liquid‐crystal (LC) cells is proposed. Because the measurement images of an LC cell is perfectly focused by using a telecentric lens, the 2‐D cell‐parameter distribution can be determined by measuring the Stokes parameters of the LC cell at several different wavelengths by changing the oblique angle of the incident light on the LC cell. 相似文献
975.
Wireless sensor networks (WSNs) have been widely studied and usefully employed in many applications such as monitoring environments and embedded systems. WSNs consist of many nodes spread randomly over a wide area; therefore, the sensing regions of different nodes may overlap partially. This is called the “sensing coverage problem”. In this paper, we define a maximum sensing coverage region (MSCR) problem and present a novel gossip-based sensing-coverage-aware algorithm to solve the problem. In the algorithm, sensor nodes gossip with their neighbors about their sensing coverage region. In this way, nodes decide locally to forward packets (as an active node) or to disregard packets (as a sleeping or redundant node). Being sensing-coverage-aware, the redundant node can cut back on its activities whenever its sensing region is k-covered by enough neighbors. With the distributed and low-overhead traffic benefits of gossip, we spread energy consumption to different sensor nodes, achieve maximum sensing coverage with minimal energy consumption in each individual sensor node, and prolong the whole network lifetime. We apply our algorithm to improve LEACH, a clustering routing protocol for WSNs, and develop a simulation to evaluate the performance of the algorithm. 相似文献
976.
A method is introduced to calculate wedge factors for an enhanced dynamic wedge (EDW). An analytic formula has been derived that allows the determination of wedge factors at the center of symmetric and asymmetric photon fields. The formalism is an extension of the "MU fraction approximation," which holds that the dynamic wedge factor is equal to the fraction of MU delivered to the point of calculation. Extensive data are presented, comparing measured enhanced dynamic wedge factors with the current method and the MU fraction model for both symmetric and asymmetric fields. For both 6 and 18 MV photons, the current method demonstrates improved results: Agreement to within 1% is obtained in all symmetric fields and within 2% for all asymmetric fields compared with discrepancies of up to 4% obtained with the MU fraction model. 相似文献
977.
A novel approach to the optical implementation of second-order neural networks that can recognize multiple patterns is reported. The systems issues, especially the accuracy required for the weighted interconnections, are discussed for numeric character (0-9) recognition. It is shown that the accuracy of the weighted interconnections has a far greater influence on the network performance during training than on classification. To lessen the problem, we introduce an adaptive learning rule, whereby the optical power is adjusted during training. Finally, numeric character recognition using an experimental system with a liquid-crystal display is demonstrated. 相似文献
978.
Spherical polycrystalline particles of Na4Zr2Si3O12 (NZS) have been prepared by a mist pyrolysis technique with alkoxide ethanol solution. Firing the precursor particles, obtained by pyrolysing at 550 °C, yielded the NZS with the highest S/N ratio and the least second phase at 1000 °C. Each spherical particle with an average size of 0.5 m was composed of primary particles of 0.1 m diameter after firing. Comparing the particle formation process with the sol-gel, alkoxide pyrolysis and the aqueous solution processes, it would appear that the primary particle size of the mist-pyrolysed NZS depends on the size and residual alkyl group content of the precursor polymers. 相似文献
979.
Yu. V. Sushko H. Ito T. Ishiguro K. Andres S. Horiuchi G. Saito N. D. Kushch E. B. Yagubskii 《Journal of Superconductivity》1994,7(6):937-941
Systematic experimental study of the electrical transport and static magnetization reveals a direct and delicate interplay between magnetism and superconductivity in the organic material-(BEDT-TTF)2Cu[N(CN)2]Cl, displayed through the specific temperature-pressure phase diagram, and such new effects for organic solids as the reentrant superconductivity in zero applied magnetic field and high-field-induced interchange between superconductivity and the nonmetallic resistive phase in the high-pressure region. 相似文献
980.
Neil S. Grigg Marvin E. Criswell Darrell G. Fontane Laurel Saito Thomas J. Siller Daniel K. Sunada 《Canadian Metallurgical Quarterly》2004,130(3):160-165
An integrated curriculum, which draws material from different areas to teach students about design and problem-solving, offers civil engineering educators an option for accommodating new topics without increasing the number of courses. Freshman engineering and the senior capstone course are two examples of integrated courses, and the writers present a 5-year perspective on an approach that extends the concept of integration to six additional courses, comprised of an 8-course, integrated civil engineering core curriculum. Drawing on their combined experiences with the courses and assessment in a review by the Accreditation Board for Engineering and Technology, the writers conclude that the curriculum offers a useful vehicle by which to add material to the 4-year program without increasing the number of credit hours, and offers flexible courses to meet goals of professional groups. The paper describes lessons learned, challenges that remain, and current approaches to improvement. 相似文献