全文获取类型
收费全文 | 524739篇 |
免费 | 5572篇 |
国内免费 | 1045篇 |
专业分类
电工技术 | 8275篇 |
综合类 | 2650篇 |
化学工业 | 82315篇 |
金属工艺 | 26240篇 |
机械仪表 | 18321篇 |
建筑科学 | 11129篇 |
矿业工程 | 5085篇 |
能源动力 | 9573篇 |
轻工业 | 36066篇 |
水利工程 | 7258篇 |
石油天然气 | 15723篇 |
武器工业 | 55篇 |
无线电 | 49993篇 |
一般工业技术 | 111973篇 |
冶金工业 | 74301篇 |
原子能技术 | 14958篇 |
自动化技术 | 57441篇 |
出版年
2021年 | 4240篇 |
2019年 | 4104篇 |
2018年 | 21451篇 |
2017年 | 20631篇 |
2016年 | 17843篇 |
2015年 | 5219篇 |
2014年 | 8277篇 |
2013年 | 18580篇 |
2012年 | 14948篇 |
2011年 | 24444篇 |
2010年 | 20324篇 |
2009年 | 19045篇 |
2008年 | 20672篇 |
2007年 | 21505篇 |
2006年 | 12076篇 |
2005年 | 11618篇 |
2004年 | 11306篇 |
2003年 | 11022篇 |
2002年 | 10421篇 |
2001年 | 9724篇 |
2000年 | 9622篇 |
1999年 | 8916篇 |
1998年 | 18736篇 |
1997年 | 13864篇 |
1996年 | 10687篇 |
1995年 | 8497篇 |
1994年 | 7729篇 |
1993年 | 7731篇 |
1992年 | 6394篇 |
1991年 | 6219篇 |
1990年 | 6461篇 |
1989年 | 6267篇 |
1988年 | 6034篇 |
1987年 | 5636篇 |
1986年 | 5590篇 |
1985年 | 6148篇 |
1984年 | 5934篇 |
1983年 | 5575篇 |
1982年 | 5259篇 |
1981年 | 5356篇 |
1980年 | 5286篇 |
1979年 | 5388篇 |
1978年 | 5575篇 |
1977年 | 5894篇 |
1976年 | 7113篇 |
1975年 | 5041篇 |
1974年 | 5046篇 |
1973年 | 5163篇 |
1972年 | 4502篇 |
1971年 | 4151篇 |
排序方式: 共有10000条查询结果,搜索用时 265 毫秒
991.
992.
993.
994.
Reviews available research on the meaning and measurement of denial and strategies for treating maladaptive denial, with special reference to its occurrence in traumatic head injuries. Questionnaire or interview measures, rather than behavioral indices, are used to assess denial. Denial may be manifested with respect to past, present, or future status; and it may have both positive and negative consequences for coping, motivation, and rehabilitation. Where denial limits a patient's functioning or recovery, several treatment strategies are possible. Intervention should involve a balance between supportive and confrontational elements, with a focus on behaviors rather than verbalizations. Computer feedback, videotaping, focused group therapy, and supervised activities are possible interventions for confronting maladaptive forms of denial. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
995.
Howard George S.; Maxwell Scott E.; Berra Susan M.; Sternitzke Mary E. 《Canadian Metallurgical Quarterly》1985,70(1):233
Updated the report of W. M. Cox and V. Catt (see record 1978-21651-001) by determining the 40 top contributing institutions to the Journal of Applied Psychology, 1976–1982, and assessed the generalizability of productivity rankings based solely on contributions to this journal. A number of industrial and organizational psychologists were asked to indicate all the journals in which psychologists in the field were likely to publish. Five journals suggested by these nominators were used for comparison in the review. A list of the 40 most productive graduate programs based on these 5 journals is included. Results show the inadequacy of Cox and Catt's decision to base productivity ratings solely on contributions to 1 journal. Using 5 journals, 4 programs were catapulted into the top 10 rankings, while 7 programs dropped from top rankings in the Cox study (1970–1975) to below the 65th rank in the present study. Using only the Journal of Applied Psychology contributions, 2 of these programs ranked in the top 10, 1976–1982. (5 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
996.
M. Delgado-Pinar J. Mora A. Diez J.L. Cruz M.V. Andres 《Photonics Technology Letters, IEEE》2005,17(3):552-554
We report a wavelength-switchable fiber ring laser that includes a Bragg grating-based acoustooptic superlattice modulator. Wavelength switching of the laser emission is achieved by controlling the peak reflectivity of the different reflection bands that appear on both sides of the Bragg wavelength when a longitudinal acoustic wave propagates along the grating. 相似文献
997.
On the macroscopic optimization of multicell wireless systems with multiuser detection and multiple antennas - uplink analysis 总被引:1,自引:0,他引:1
In this paper, we consider a system with K single-antenna client users, n/sub B/ base stations (each base station has n/sub R/ antennas), as well as a centralized controller. A client user could be associated with a single base station at any time. All the base stations operate at the same frequency and have optimal multiuser detection per base station which cancels intracell interference only. We consider a general problem of uplink macroscopic resource management where the centralized controller dynamically determines an appropriate association mapping of the K users with respect to the n/sub B/ base stations over a macroscopic time scale. We propose a novel analytical framework for the above macroscopic scheduling problems. A simple rule is to associate a user with the strongest base station (camp-on-the-strongest-cell), and this has been widely employed in conventional cellular systems. However, based on the optimization framework, we found that this conventional approach is in fact not optimal when multiuser detection is employed at the base station. We show that the optimal macroscopic scheduling algorithm is of exponential complexity, and we propose a simple greedy algorithm as a feasible solution. 相似文献
998.
Lewis V. McCarty Richard Donelson Robert f. Hehemann 《Metallurgical and Materials Transactions A》1991,22(1):969-974
A mathematical model describes the carburization kinetics of tungsten powders mixed with carbon and heated in hydrogen. It
is based on diffusion of carbon through a shell of WC growing into particles which are modeled as spheres. The activation
energy is 58 kcal/mole in the temperature range 1056 to 1833 °C. Hydrogen gas is important to transport carbon as methane
or acetylene, but increased hydrogen pressure increases the rate of carburization so little that an adsorbed species such
as CH probably controls the carbon concentration at the particle surface.
Formerly with the Lamp Metals Laboratory, deceased, was Professor of Metallurgy at Case Western Reserve University Cleveland
OH. 相似文献
999.
1000.
V. Anjos M.J.V. Bell E.F. da Silva Jr. R.W.A. Franco I.A. Esquef 《Microelectronics Journal》2005,36(11):977-980
In this paper we report the use of photothermal techniques such as Thermal lens (TL) spectrometry, Photoacoustic and heat capacity, ρcp, to determine the thermo-optical parameters, such as thermal conductivity (K), thermal diffusivity (D), specific heat (cp) and the optical path dependence with temperature (ds/dT), of an undoped polycrystalline 3C-SiC. To our knowledge, this is the first time that Thermal lens technique is used for wide band-gap systems. Results obtained for the polycrystalline sample with TL technique indicates that ds/dT is negative at room temperature. Moreover, the obtained values of thermal diffusivity and thermal conductivity are in good agreement with that found in the literature, indicating that the phototermal techniques can be used to obtain the referred parameters in circumstances where other techniques cannot be used, for example, in harsh environments. 相似文献