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   2258篇
  免费   16篇
电工技术   19篇
综合类   2篇
化学工业   181篇
金属工艺   11篇
机械仪表   17篇
建筑科学   61篇
矿业工程   1篇
能源动力   26篇
轻工业   203篇
水利工程   5篇
石油天然气   3篇
无线电   96篇
一般工业技术   182篇
冶金工业   1254篇
原子能技术   10篇
自动化技术   203篇
  2022年   7篇
  2021年   10篇
  2020年   12篇
  2019年   26篇
  2018年   21篇
  2017年   25篇
  2016年   13篇
  2015年   14篇
  2014年   12篇
  2013年   82篇
  2012年   43篇
  2011年   59篇
  2010年   45篇
  2009年   41篇
  2008年   54篇
  2007年   55篇
  2006年   53篇
  2005年   46篇
  2004年   51篇
  2003年   42篇
  2002年   34篇
  2001年   32篇
  2000年   28篇
  1999年   62篇
  1998年   368篇
  1997年   233篇
  1996年   138篇
  1995年   88篇
  1994年   76篇
  1993年   80篇
  1992年   25篇
  1991年   19篇
  1990年   20篇
  1989年   22篇
  1988年   19篇
  1987年   29篇
  1986年   22篇
  1985年   23篇
  1984年   12篇
  1983年   11篇
  1982年   14篇
  1981年   20篇
  1980年   13篇
  1979年   20篇
  1978年   8篇
  1977年   33篇
  1976年   64篇
  1975年   13篇
  1974年   9篇
  1971年   7篇
排序方式: 共有2274条查询结果,搜索用时 0 毫秒
41.
In this study, a macro-ergonomic risk assessment tool was developed based on criteria of scope, simplicity, practicality, usefulness, reliability and job-specificity. A relative stress index 'RSI' was formulated to take into account multiple parameters, such as frequency, duration, repetition, weight, force, travel distance and horizontal distance. This tool was tested in nuclear remediation industry. The results are presented and discussed.  相似文献   
42.
Smoke animations are hard to art‐direct because simple changes in parameters such as simulation resolution often lead to unpredictable changes in the final result. Previous work has addressed this problem with a guiding approach which couples low‐resolution simulations – that exhibit the desired flow and behaviour – to the final, high‐resolution simulation. This is done in such a way that the desired low frequency features are to some extent preserved in the high‐resolution simulation. However, the steady (i.e. constant) guiding used often leads to a lack of sufficiently high detail, and employing time‐dependent guiding is expensive because the matrix of the resulting set of equations needs to be recomputed at every iteration. We propose an improved mathematical model for Eulerian‐based simulations which is better suited for dynamic, time‐dependent guiding of smoke animations through a novel variational coupling of the low‐ and high‐resolution simulations. Our model results in a matrix that does not require re‐computation when the guiding changes over time, and hence we can employ time‐dependent guiding more efficiently both in terms of storage and computational requirements. We demonstrate that time‐dependent guiding allows for more high frequency detail to develop without losing correspondence to the low resolution simulation. Furthermore, we explore various artistic effects made possible by time‐dependent guiding.  相似文献   
43.
Critical, or national, information infrastructure protection, referred to as either CIIP or NIIP, has been highlighted as a critical factor in overall national security by the United States, the United Kingdom, India and the European Community. As nations move inexorably towards so-called ‘digital economies’, critical infrastructure depends on information systems to process, transfer, store and exchange information through the Internet. Electronic attacks such as denial of service attacks on critical information infrastructures challenge the law and raise concerns. A myriad of issues potentially plague the protection of critical information infrastructures owing to the lack of legal regulation aimed at ensuring the protection of critical information infrastructures. This paper will highlight the legal concerns that relate to the denial of service attacks on critical information infrastructures and provide an introductory overview of the law as it relates to CIIP in Australia.  相似文献   
44.
In this paper we present FeynRules, a new Mathematica package that facilitates the implementation of new particle physics models. After the user implements the basic model information (e.g., particle content, parameters and Lagrangian), FeynRules derives the Feynman rules and stores them in a generic form suitable for translation to any Feynman diagram calculation program. The model can then be translated to the format specific to a particular Feynman diagram calculator via FeynRules translation interfaces. Such interfaces have been written for CalcHEP/CompHEP, FeynArts/FormCalc, MadGraph/MadEvent and Sherpa, making it possible to write a new model once and have it work in all of these programs. In this paper, we describe how to implement a new model, generate the Feynman rules, use a generic translation interface, and write a new translation interface. We also discuss the details of the FeynRules code.

Program summary

Program title: FeynRulesCatalogue identifier: AEDI_v1_0Program summary URL::http://cpc.cs.qub.ac.uk/summaries/AEDI_v1_0.htmlProgram obtainable from: CPC Program Library, Queen's University, Belfast, N. IrelandLicensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.htmlNo. of lines in distributed program, including test data, etc.: 15 980No. of bytes in distributed program, including test data, etc.: 137 383Distribution format: tar.gzProgramming language: MathematicaComputer: Platforms on which Mathematica is availableOperating system: Operating systems on which Mathematica is availableClassification: 11.1, 11.2, 11.6Nature of problem: Automatic derivation of Feynman rules from a Lagrangian. Implementation of new models into Monte Carlo event generators and FeynArts.Solution method: FeynRules works in two steps:
1. derivation of the Feynman rules directly form the Lagrangian using canonical commutation relations among fields and creation operators.
2. implementation of the new physics model into FeynArts as well as various Monte Carlo programs via interfaces.
Full-size table
  相似文献   
45.
IntroductionSeveral statistical methods of assessing seasonal variation are available. Brookhart and Rothman [3] proposed a second-order moment-based estimator based on the geometrical model derived by Edwards [1], and reported that this estimator is superior in estimating the peak-to-trough ratio of seasonal variation compared with Edwards’ estimator with respect to bias and mean squared error. Alternatively, seasonal variation may be modelled using a Poisson regression model, which provides flexibility in modelling the pattern of seasonal variation and adjustments for covariates.MethodBased on a Monte Carlo simulation study three estimators, one based on the geometrical model, and two based on log-linear Poisson regression models, were evaluated in regards to bias and standard deviation (SD). We evaluated the estimators on data simulated according to schemes varying in seasonal variation and presence of a secular trend. All methods and analyses in this paper are available in the R package Peak2Trough [13].ResultsApplying a Poisson regression model resulted in lower absolute bias and SD for data simulated according to the corresponding model assumptions. Poisson regression models had lower bias and SD for data simulated to deviate from the corresponding model assumptions than the geometrical model.ConclusionThis simulation study encourages the use of Poisson regression models in estimating the peak-to-trough ratio of seasonal variation as opposed to the geometrical model.  相似文献   
46.
Modular Analysis of Petri Nets   总被引:9,自引:0,他引:9  
  相似文献   
47.
48.
Relaxation oscillations occur when a capacitor is inserted in series with a field emission tube, a DC high-voltage power supply, and a ballast resistor. The waveform of these oscillations is highly reproducible with a dominant frequency of 200 MHz and a decay time of 20 ns. The peak current as high as 320 mA has been observed although the tungsten emitter is only rated for 10 microA. We have shown that these oscillations are due to a displacement current, charging of the anode-tip capacitance, and are not of a field emission origin. We conclude that the effects of displacement current should be considered in measurements of field emission with microsecond pulses, where high-current densities can be observed.  相似文献   
49.
We studied the effect of short-term triiodothyronine administration on thyroid gland responsivity to exogenous thyrotropin in four euthyroid human subjects. Thyroidal iodine release and serum thyroxine during daily im injections of bovine TSH were not significantly inhibited, despite a four-fold elevation in serum T3 concentrations. This negative finding contrasts with earlier positive reports of a regulatory "short-loop" effect of elevated circulating T3 on the thyroid gland. This difference may be due either to the use in previous murine or in vitro studies of non-physiologic, high doses of exogenous T3, or failure to control the withdrawal of the trophic effect of endogenous TSH in man on the subsequent glandular response.  相似文献   
50.
The revelation of an affair is often an emotionally explosive event for a couple, yet little is known about specific individual and relationship factors that accompany infidelity. The present study examined the qualities of individuals and couples that differentiate couples with (n = 19) and without (n = 115) infidelity using couples from a randomized clinical trial of marital therapy. Findings indicated that couples with infidelity showed greater marital instability, dishonesty, arguments about trust, narcissism, and time spent apart. Gender also proved to be a significant moderator of several effects. Men who had participated in affairs showed increased substance use, were older, and were more sexually dissatisfied. Results offer initial clues to concomitants of affairs for couple therapists. (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