首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   288篇
  免费   10篇
  国内免费   3篇
电工技术   4篇
化学工业   55篇
机械仪表   1篇
建筑科学   8篇
矿业工程   1篇
能源动力   6篇
轻工业   13篇
水利工程   3篇
石油天然气   2篇
无线电   36篇
一般工业技术   39篇
冶金工业   44篇
自动化技术   89篇
  2023年   2篇
  2022年   12篇
  2021年   7篇
  2020年   4篇
  2019年   4篇
  2018年   6篇
  2017年   5篇
  2016年   11篇
  2015年   10篇
  2014年   9篇
  2013年   18篇
  2012年   10篇
  2011年   11篇
  2010年   10篇
  2009年   22篇
  2008年   19篇
  2007年   14篇
  2006年   13篇
  2005年   12篇
  2004年   10篇
  2003年   8篇
  2002年   10篇
  2001年   8篇
  2000年   4篇
  1999年   5篇
  1998年   9篇
  1997年   12篇
  1996年   5篇
  1995年   6篇
  1994年   4篇
  1993年   5篇
  1992年   2篇
  1991年   4篇
  1989年   1篇
  1988年   1篇
  1987年   1篇
  1982年   1篇
  1979年   2篇
  1978年   2篇
  1975年   1篇
  1971年   1篇
排序方式: 共有301条查询结果,搜索用时 0 毫秒
291.

Purpose

Aggressive driving is a growing problem worldwide. Previous research has provided us with some insights into the characteristics of drivers prone to aggressiveness on the road and into the external conditions triggering such behavior. Little is known, however, about the personality traits of aggressive drivers. The present study proposes planned behavior and materialism as predictors of aggressive driving behavior.

Design/methodology

Data was gathered using a questionnaire-based survey of 220 individuals from twelve large industrial organizations in Israel. Our hypotheses were tested using structural equation modeling.

Findings

Our results indicate that while planned behavior is a good predictor of the intention to behave aggressively, it has no impact on the tendency to behave aggressively. Materialism, however, was found to be a significant indicator of aggressive driving behavior.

Research limitations

Our study is based on a self-reported survey, therefore might suffer from several issues concerning the willingness to answer truthfully. Furthermore, the sampling group might be seen as somewhat biased due to the relatively high income/education levels of the respondents.

Originality/value

While both issues, aggressive driving and the theory of planned behavior, have been studied previously, the linkage between the two as well as the ability of materialism to predict aggressive behavior received little attention previously. The present study encompasses these constructs providing new insights into the linkage between them.  相似文献   
292.
The CHaracteristic-function-Enabled Source Separation (CHESS) method for independent component analysis (ICA) is based on approximate joint diagonalization (AJD) of Hessians of the observations' empirical log-characteristic-function, taken at selected off-origin “processing points”. As previously observed in other contexts, the AJD performance can be significantly improved by optimal weighting, using the inverse of the covariance matrix of all of the off-diagonal terms of the target-matrices. Fortunately, this apparently cumbersome weighting scheme takes a convenient form under the assumption that the mixture is already “nearly separated”, e.g., following some initial separation. We derive covariance expressions for the Sample-Hessian matrices, and show that under the near-separation assumption, the weight matrix takes a nearly block-diagonal form, conveniently exploited by the recently proposed WEighted Diagonalization using Gauss itErations (WEDGE) algorithm for weighted AJD. Using our expressions, the weight matrix can be estimated directly from the data—leading to our WeIghTed CHESS (WITCHESS) algorithm. Simulation results demonstrate how WITCHESS can lead to significant performance improvement, not only over unweighted CHESS, but also over other ICA methods.  相似文献   
293.
Oreochromis fishes exhibit variability of sex-determination (SD) genes whose characterization contributes to understanding of the sex differentiation network, and to effective tilapia farming, which requires all-male culture. However, O. niloticus (On) amh is the only master-key regulator (MKR) of SD that has been mapped (XY/XX SD-system on LG23). In O. aureus (Oa), LG3 controls a WZ/ZZ SD-system that has recently been delimited to 9.2 Mbp, with an embedded interval rich with female-specific variation, harboring two paics genes and banf2. Developing genetic markers within this interval and using a hybrid Oa stock that demonstrates no recombination repression in LG3, we mapped the critical SD region to 235 Kbp on the orthologous On physical map (p < 1.5 × 10−26). DNA-seq assembly and peak-proportion analysis of variation based on Sanger chromatograms allowed the characterization of copy-number variation (CNV) of banf2. Oa males had three exons capable of encoding 90-amino-acid polypeptides, yet in Oa females, we found an extra copy with an 89-amino-acid polypeptide and three non-conservative amino acid substitutions, designated as banf2w. CNV analysis suggested the existence of two to five copies of banf2 in diploidic Cichlidae. Disrupting the Hardy–Weinberg equilibrium (p < 4.2 × 10−3), banf2w was concordant with female determination in Oa and in three cichlids with LG3 WZ/ZZ SD-systems (O. tanganicae, O. hornorum and Pelmatolapia mariae). Furthermore, exclusive RNA-seq expression in Oa females strengthened the candidacy of banf2w as the long-sought LG3 SD MKR. As banf genes mediate nuclear assembly, chromatin organization, gene expression and gonad development, banf2w may play a fundamental role inducing female nucleus formation that is essential for WZ/ZZ SD.  相似文献   
294.
Abstract

This study explores the relationship between art and urban boundaries using the case study of a fringe theatre festival in the Israeli mixed-city of Acre. While mixed cities today are understood as agglomerations of enclaves, maintained and reinforced by boundaries, urban designers and artists have used art as a culture-led regeneration strategy through which these boundaries may be breached. This study undermines the shared assumption of both fields: that art has the power to breach boundaries, by juxtaposing a city’s artistic activity with its segregation patterns and boundaries. Using super-positioning, the findings of two research methods have been integrated: urban research and ethnographic field work. The article shows that although the artistic activity in question is rooted in an avant-garde radical desire to subvert socioeconomic structures, it actually produces new versions and interpretations of the same segregations and boundaries in both space and society.  相似文献   
295.
We introduce a time-domain source-model technique for analysis of two-dimensional, transverse-magnetic, plane-wave scattering by a photonic crystal slab composed of a finite number of identical layers, each comprising a linear periodic array of dielectric cylinders. The proposed technique takes advantage of the periodicity of the slab by solving the problem within a unit cell of the periodic structure. A spectral analysis of the temporal behavior of the fields scattered by the slab shows a clear agreement between frequency bands where the spectral density of the transmitted energy is low and the bandgaps of the corresponding two-dimensionally infinite periodic structure. The effect of the bandwidth of the incident pulse and its center frequency on the manner it is transmitted through and reflected by the slab is studied via numerical examples.  相似文献   
296.
Scanning tunneling spectroscopy in the shell-filling regime was carried out at room temperature to investigate the size dependence of the band gap and single-electron charging energy of single Si quantum dots (QDs). The results are compared with model calculation. A 12-fold multiple staircase structure was observed for a QD of about 4.3 nm diameter, reflecting the degeneracy of the first energy level, as expected from theoretical calculations. The systematic broadening of the tunneling spectroscopy peaks with decreasing dot diameter is attributed to the reduced barrier height for smaller dot sizes and to the splitting of the first energy level.  相似文献   
297.
The purpose of this article is to provide supervisors with postdisaster strategies for promoting supervisee self-care. These recommendations are based on relevant disaster mental health and supervision research along with the authors' experiences of supervising and teaching in a university setting following Hurricane Katrina in South Mississippi. Supervisory examples from the authors' hurricane experiences are also provided to highlight each recommendation. A supervisee self-care tool is offered to aid supervisors in their efforts to help supervisees develop positive coping responses in the event of a disaster. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
298.
This paper summarises innovative research into the assessment of long-term groundwater recharge from flood events in dryland environments of the Kuiseb (Namibia) and the Buffels (South Africa) rivers. The integrated water resource management (IWRM) policies and institutions affecting the exploitation of groundwater resources in each of these developing countries are compared. The relatively large alluvial aquifer of the Kuiseb River (~240 Mm3) is recharged from irregular floods originating in the upper catchment. Reported abstraction of 4.6 Mm3 per year is primarily consumed in the town of Walvis Bay, although the groundwater decay (pumping and natural losses along the period 1983–2005) was estimated in 14.8 Mm3 per year. Recharge is variable, occurring in 11 out of 13 years in the middle Kuiseb River, but only in 11 out of 28 years in the middle-lower reaches. In contrast, the Buffels River has relatively minor alluvial aquifers (~11 Mm3) and recharge sources derive from both lateral subsurface flow and floodwater infiltration, the latter limited to a recharge maximum of 1.3 Mm3 during floods occurring once every four years. Current abstractions to supply the adjacent rural population and a few small-scale, irrigated commercial farms are 0.15 Mm3 yr???1, well within the long-term sustainable yield estimated to be 0.7 Mm3 yr???1. Since independence in 1990, Namibia’s water resource management approach has focussed on ephemeral river basin management of which the Kuiseb Basin Management Committee (KBMC) is a model. Here, some water points are managed independently by rural communities through committees while the national bulk water supplier provides for Walvis Bay Municipality from the lower aquifers. This provides a sense of local ownership through local participation between government, NGOs and CBOs (community-based organisations) in the planning and implementation of IWRM. Despite the potential for water resource development in the lower Buffels River, the scope for implementing IWRM is limited not only by the small aquifer size, but also because basin management in South Africa is considered only in the context of perennial rivers. Since 2001, water service delivery in the Buffels River catchment has become the responsibility of two newly created local municipalities. As municipal government gains experience, skills and capacity, its ability to respond to local needs related to water service delivery will be accomplished through local participation in the design and implementation of annual ‘integrated development plans’. These two case studies demonstrate that a variety of IWRM strategies in the drylands of developing countries are appropriate depending on scales of governance, evolving policy frameworks, scales of need and limitations inherent in the hydrological processes of groundwater resources.  相似文献   
299.
Precursor nanoparticles that form spontaneously on hydrolysis of tetraethylorthosilicate in aqueous solutions of tetrapropylammonium (TPA) hydroxide evolve to TPA-silicalite-1, a molecular-sieve crystal that serves as a model for the self-assembly of porous inorganic materials in the presence of organic structure-directing agents. The structure and role of these nanoparticles are of practical significance for the fabrication of hierarchically ordered porous materials and molecular-sieve films, but still remain elusive. Here we show experimental findings of nanoparticle and crystal evolution during room-temperature ageing of the aqueous suspensions that suggest growth by aggregation of nanoparticles. A kinetic mechanism suggests that the precursor nanoparticle population is distributed, and that the 5-nm building units contributing most to aggregation only exist as an intermediate small fraction. The proposed oriented-aggregation mechanism should lead to strategies for isolating or enhancing the concentration of crystal-like nanoparticles.  相似文献   
300.
It is often the case that after a scheduling problem has been solved some small changes occur that make the solution of the original problem not valid. Solving the new problem from scratch can result in a schedule that is very different from the original schedule. In applications such as a university course timetable or flight scheduling, one would be interested in a solution that requires minimal changes for the users. The present paper considers the minimal perturbation problem. It is motivated by scenarios in which a Constraint Satisfaction Problem (CSP) is subject to changes. In particular, the case where some of the constraints are changed after a solution was obtained. The goal is to find a solution to the changed problem that is as similar as possible (e.g. includes minimal perturbations) to the previous solution. Previous studies proposed a formal model for this problem (Barták et al. 2004), a best first search algorithm (Ross et al. 2000), complexity bounds (Hebrard et al. 2005), and branch and bound based algorithms (Barták et al. 2004; Hebrard et al. 2005). The present paper proposes a new approach for solving the minimal perturbation problem. The proposed method interleaves constraint optimization and constraint satisfaction techniques. Our experimental results demonstrate the advantage of the proposed algorithm over former algorithms. Experiments were performed both on random CSPs and on random instances of the Meeting Scheduling Problem.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号