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   1700篇
  免费   49篇
  国内免费   1篇
电工技术   10篇
化学工业   254篇
金属工艺   22篇
机械仪表   38篇
建筑科学   107篇
矿业工程   10篇
能源动力   27篇
轻工业   266篇
水利工程   8篇
石油天然气   3篇
无线电   87篇
一般工业技术   192篇
冶金工业   501篇
原子能技术   2篇
自动化技术   223篇
  2022年   31篇
  2021年   36篇
  2020年   17篇
  2019年   23篇
  2018年   30篇
  2017年   30篇
  2016年   36篇
  2015年   30篇
  2014年   45篇
  2013年   112篇
  2012年   65篇
  2011年   91篇
  2010年   85篇
  2009年   69篇
  2008年   85篇
  2007年   79篇
  2006年   88篇
  2005年   75篇
  2004年   49篇
  2003年   44篇
  2002年   43篇
  2001年   30篇
  2000年   25篇
  1999年   31篇
  1998年   35篇
  1997年   28篇
  1996年   33篇
  1995年   31篇
  1994年   34篇
  1993年   20篇
  1992年   16篇
  1991年   12篇
  1990年   14篇
  1989年   18篇
  1988年   20篇
  1987年   22篇
  1986年   18篇
  1985年   29篇
  1984年   20篇
  1983年   19篇
  1982年   10篇
  1981年   17篇
  1980年   9篇
  1979年   12篇
  1978年   7篇
  1977年   6篇
  1976年   6篇
  1975年   7篇
  1974年   8篇
  1971年   5篇
排序方式: 共有1750条查询结果,搜索用时 0 毫秒
1.
Events leading up to the introduction of the pollinating weevil (Elaeidobius kamerunicus) into Malaysian plantations are described, and the effect of this on the industry is discussed. The main benefits so far are increased kernels and savings in estate pollination costs. It is as yet too early to assess other benefits. The changes in bunch composition have given rise to some processing problems, i.e., sterilization and nut processing, which are currently being corrected. There have been no major changes in processing procedures, but process developments, such as the use of decanters, computerization, steam utilization and quality improvements, are being made. A review of effluent treatment from palm oil mills shows that most mills conform to government standards using mostly biological digestion processes and land application. Research and development projects are discussed. These include tissue culture and utilization of byproducts.  相似文献   
2.
Tested the ability of 4 adult male Sprague-Dawley rats to use odors in discrimination among littermates living as a group. Ss were trained in a Y-maze to discriminate the presence of a littermate from its absence. Results from transfer of training in 3 subsequent testing periods indicated that the animals were capable of distinguishing among individuals when relatedness and familiarity were held constant, that this ability was not due to training, and that performance was based solely on odor cues. Results suggest that laboratory rats exhibit odor sensitivities conmensurate with very complex social processes. (17 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
3.
In this paper we consider two performance modelling techniques from the perspectives of model construction, generation of an underlying continuous time Markov process, and the potential for reduction in the Markov process. Such careful comparison of modelling techniques allows us to appreciate the strengths and weaknesses of different approaches, and facilitates cross-fertilization between them. In the present case we take a characteristic of one formalism, functional rates in Stochastic Automata Networks, and introduce it to the other formalism, Performance Evaluation Process Algebra. We investigate the benefits of this cross-fertilization, particularly from the perspectives of Markov process generation and reduction.  相似文献   
4.
We give a parametrized family of rational interval maps of degree two, each ergodic, exact and preserving a measure equivalent to a Lebesgue measure. The family includes the unique quadratic Chebyshev polynomial as its only polynomial map. We extend the family to other settings on the circle and real line. We also give numerical approximations to the entropy of the equivalent invariant measure and the Hausdorff dimension of the singular measure of maximal entropy.  相似文献   
5.
This field study examined applicant reactions (N = 802) toward face-to-face as compared with technology-mediated interviews (through videoconferencing or by telephone) for 346 organizations. Face-to-face interviews were perceived as more fair and led to higher job acceptance intentions than were videoconferencing and telephone interviews. Perceived interview outcomes were higher with face-to-face and telephone interviews over videoconferencing. Self-monitoring moderated the relationship between interview medium and perceptions of fairness. Specifically, this relationship was (a) positive for face-to-face, (b) negative for telephone, and (c) nonsignificant for videoconferencing interviews. Moreover, the number of offers an applicant received moderated the relationship between interview medium over, and perceived fairness. The relationship between number of offers and perceived fairness was positive for face-to-face and negative for technology-mediated interviews. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
6.
Exp I, with 12 male hooded rats, demonstrated that Ss with caudate-putamen lesions exhibited an impairment in the acquisition and reversal of a spatial maze task when compared with unoperated control Ss. Exp II, with 24 Ss, investigated leverpress responding supported by a VI schedule in 3 groups of Ss: a group with caudate-putamen lesions, a group with lesions of the posterior cortex, and an unoperated control group. The presentation of a 0.5-sec, response-contingent light correlated with reinforcement generated an elevated response rate in the 2 operated groups but tended to suppress responding in the control group, perhaps by overshadowing the response–reinforcer relation. Only the group with cortical lesions maintained the elevated rate when the light was uncorrelated with food delivery. Exp III confirmed for these same Ss that caudate-putamen lesions produced a spatial learning deficit. No deficit was observed in the posterior cortex group. It is suggested that caudate-putamen lesions disrupt the mechanism underlying the response–reinforcer association on which spatial maze learning and free operant responding in part depend. (48 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
7.
8.
We have identified three yeast genes, KES1, HES1 and OSH1, whose products show homology to the human oxysterol binding protein (OSBP). Mutations in these genes resulted in pleiotropic sterol-related phenotypes. These include tryptophan-transport defects and nystatin resistance, shown by double and triple mutants. In addition, mutant combinations showed small but apparently cumulative reductions in membrane ergosterol levels. The three yeast genes are also functionally related as overexpression of HES1 or KES1 alleviated the tryptophan-transport defect in kes1Δ or osh1Δ mutants, respectively. Our study implicates this new yeast gene family in ergosterol synthesis and provides comparative evidence of a role for human OSBP in cholesterol synthesis.  相似文献   
9.
R. V. McDonald and S. Siegel (see record 2004-10475-001) present new evidence for the idea that opioid drug-opposite responses can become conditioned to cues of initial drug onset and that they could, therefore, play a role in the development of tolerance of some drug effects and a role in the elicitation of withdrawal-like symptoms in cases in which addicted individuals are exposed to small doses of the drug they normally consume. In this comment, some puzzling features of the data are discussed, and alternative explanations are suggested. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
10.
Utilitarian and economic theories of deterrence hold that the relation of the penalty to the misdeed should be irrelevant. In 5 experiments using hypothetical cases, judgments of penalties depended on whether this relation was in kind (IK) or out of kind (OK). When victims were identifiable, IK penalties were higher than OK and preferred to OK. Subjects seemed to confuse penalties and compensation. When there were no identifiable victims (e.g., environmental damage), IK penalties were preferred, but OK penalties were higher. Here, OK judgments were more uncertain, and subjects preferred to err on the side of overpunishing. The results can be explained in terms of overgeneralization of usually useful heuristics. Alternative hypotheses concerning aggression and scale compatibility are rejected. The findings have implications for the setting of penalties in legal cases (e.g., the Exxon Valdez) and for lay theories of punishment in nonlegal settings. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  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