全文获取类型
收费全文 | 309961篇 |
免费 | 3721篇 |
国内免费 | 714篇 |
专业分类
电工技术 | 6223篇 |
综合类 | 560篇 |
化学工业 | 46772篇 |
金属工艺 | 10325篇 |
机械仪表 | 8824篇 |
建筑科学 | 7903篇 |
矿业工程 | 862篇 |
能源动力 | 8571篇 |
轻工业 | 31087篇 |
水利工程 | 2533篇 |
石油天然气 | 3669篇 |
武器工业 | 8篇 |
无线电 | 39723篇 |
一般工业技术 | 58459篇 |
冶金工业 | 56701篇 |
原子能技术 | 5462篇 |
自动化技术 | 26714篇 |
出版年
2021年 | 2277篇 |
2019年 | 2140篇 |
2018年 | 3607篇 |
2017年 | 3448篇 |
2016年 | 3540篇 |
2015年 | 2540篇 |
2014年 | 4440篇 |
2013年 | 14277篇 |
2012年 | 7366篇 |
2011年 | 10117篇 |
2010年 | 7903篇 |
2009年 | 9133篇 |
2008年 | 9607篇 |
2007年 | 9584篇 |
2006年 | 8505篇 |
2005年 | 7892篇 |
2004年 | 7763篇 |
2003年 | 7501篇 |
2002年 | 7339篇 |
2001年 | 7547篇 |
2000年 | 7211篇 |
1999年 | 7556篇 |
1998年 | 17679篇 |
1997年 | 12853篇 |
1996年 | 10107篇 |
1995年 | 7878篇 |
1994年 | 7208篇 |
1993年 | 6921篇 |
1992年 | 5290篇 |
1991年 | 5069篇 |
1990年 | 4939篇 |
1989年 | 4781篇 |
1988年 | 4676篇 |
1987年 | 3891篇 |
1986年 | 4012篇 |
1985年 | 4718篇 |
1984年 | 4279篇 |
1983年 | 4022篇 |
1982年 | 3604篇 |
1981年 | 3762篇 |
1980年 | 3459篇 |
1979年 | 3419篇 |
1978年 | 3225篇 |
1977年 | 3815篇 |
1976年 | 4849篇 |
1975年 | 2780篇 |
1974年 | 2660篇 |
1973年 | 2675篇 |
1972年 | 2215篇 |
1971年 | 1963篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
871.
872.
Noncontacting inductive sensors are applicable on a large scale for position detection or travel measurement in industrial applications. Reasons for such broad acceptance in many sectors of industry are noncontact and wear-free sensing of the target (any metal object), reliability and robustness, resistance to fouling, water tightness and compact size. The present work is intended to be a systematic, complete, and consistent presentation of the technological innovations, recent implementations and current trends regarding the analog distance and travel sensing offered by noncontacting inductive sensors for industrial applications. It starts with the fundamentals of inductive sensing and presents the physical basics gained by modern analytic and simulation methods, as well as high-level integrated circuits for inductive sensors. The following sections deal with present-day inductive analog proximity sensors and with the distinctive technological innovation offered by the new inductive linear displacement sensors and with miniaturization results achieved through consistent integration. 相似文献
873.
874.
Madden Gregory J.; Begotka Andrea M.; Raiff Bethany R.; Kastern Lana L. 《Canadian Metallurgical Quarterly》2003,11(2):139
The degree to which real and hypothetical rewards were discounted across delays ranging from 6 hr to 1 year was explored in a within-subjects design. An adjusting-amounts procedure was used to estimate the subjective value of real and hypothetical rewards at each delay. A hyperbolic discounting function provided a significantly better fit to individual participants' preferences than did an exponential function. No significant effect of reward type on degree of hyperbolic discounting or area under the discounting curves was detected. These findings offer some support for the validity of using hypothetical rewards to estimate discounting rates in substance-abusing and other populations, but caution is suggested because this support is gleaned from a failure to detect an effect of reward type. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
875.
Intact and ovariectomized oxytocin (OT)-deficient (OT-/-) and wild-type (OT+/+) mice were tested for consumption of 0.5 M NaCl solution or tap water in a 2-bottle choice test. During 3 days of acclimation, voluntary ingestion of NaCl was equal between genotypes. After overnight fluid deprivation, intact OT-/- mice ingested 2 times more NaCl solution than OT+/+ mice in the 6th hr, but not the 1 st hr, after reintroduction of fluid. Ovariectomized mice consumed less than intact mice after overnight fluid deprivation. When a 0.2 M NaCl solution was administered for 6 days in ovariectomized mice, OT-/- mice voluntarily consumed greater amounts than OT+/+ mice. After overnight fluid deprivation, consumption by OT-/- mice was 3 times that of OT+/+ mice at 1 hr and 2-fold greater after 6 hr. Enhanced intake of NaCl-containing solutions in female OT-/- mice suggests that central OT may be an important inhibitor of sodium consumption. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
876.
Seeing a talker's face influences auditory speech recognition, but the visible input essential for this influence has yet to be established. Using a new seamless editing technique, the authors examined effects of restricting visible movement to oral or extraoral areas of a talking face. In Experiment 1, visual speech identification and visual influences on identifying auditory speech were compared across displays in which the whole face moved, the oral area moved, or the extraoral area moved. Visual speech influences on auditory speech recognition were substantial and unchanging across whole-face and oral-movement displays. However, extraoral movement also influenced identification of visual and audiovisual speech. Experiments 2 and 3 demonstrated that these results are dependent on intact and upright facial contexts, but only with extraoral movement displays. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
877.
The results of experimental investigation of an Er-doped fiber bidirectional ring laser with a 90° Faraday rotator in the cavity are presented. Two theoretically predicted regimes of the bidirectional generation of modes propagating in opposite directions with either complex-conjugate or orthoconjugate polarization states have been realized in practice. In each of these regimes, stable bidirectional generation of only one longitudinal mode propagating in each direction is possible. The former regime ensures significant stabilization of a nonreciprocal frequency shift between the modes propagating in opposite directions, this shift being determined by the Faraday phase rotator. 相似文献
878.
Two studies examine complementarity (vs. mimicry) of dominant and submissive nonverbal behaviors. In the first study, participants interacted with a confederate who displayed either dominance (through postural expansion) or submission (through postural constriction). On average, participants exposed to a dominant confederate decreased their postural stance, whereas participants exposed to a submissive confederate increased their stance. Further, participants with complementing responses (dominance in response to submission and submission in response to dominance) liked their partner more and were more comfortable than those who mimicked. In the second study, complementarity and mimicry were manipulated, and complementarity resulted in more liking and comfort than mimicry. The findings speak to the likelihood of hierarchical differentiation (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
879.
K. Lefmann B. Lake G. Aeppli S.-W. Cheong N. B. Christensen K. N. Clausen S. Hayden T. E. Mason D.F. McMorrow H. A. Mook H. M. Rønnow H. Takagi 《Journal of Low Temperature Physics》2004,135(5-6):621-664
One important area of modern condensed matter research is the investigation of the nature of the superconducting cuprates. Much progress in this field has been obtained with the technique of neutron scattering. We here present a review of neutron scattering studies of the high-temperature superconductor La2?xSrxCuO4, performed at Risø National Laboratory. We review the work on the mapping of the incommensurate spin fluctuations, the investigation of the gap in the fluctuation spectrum, the magnetic properties of the vortices appearing in an applied field, and the quantum critical behaviour of the system. We discuss our findings in the light of results of neutron scattering from other groups, on other cuprate systems, and results from other experimental methods, e.g. NMR, μSR, STM, X-ray diffraction, and ARPES. We end with a discussion on the implications of the experimental results for the progress in the general understanding of high-temperature superconductivity. PACS numbers: 61.12.Ex, 74.20.Mn, 74.72.Dn, 75.25.+z, 78.70.Nx. 相似文献
880.
Today, with the increasing popularity of multicore processors, one approach to optimizing the processor's performance is to reduce the execution times of individual applications running on each core by designing and implementing more powerful cores. Another approach, which is the polar opposite of the first, optimizes the processor's performance by running a larger number of applications on a correspondingly larger number of cores, albeit simpler ones. The difference between these two approaches is that the former focuses on reducing the latency of individual applications or threads (it optimizes the processor's single-threaded performance), whereas the latter focuses on reducing the latency of the applications' threads taken as a group (it optimizes the processor's multithreaded performance). The panel, from the 2007 Workshop on Computer Architecture Research Directions, discusses the relevant issues. 相似文献