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   678篇
  免费   55篇
电工技术   7篇
化学工业   99篇
金属工艺   8篇
机械仪表   9篇
建筑科学   16篇
能源动力   47篇
轻工业   44篇
水利工程   10篇
石油天然气   3篇
无线电   73篇
一般工业技术   130篇
冶金工业   179篇
原子能技术   2篇
自动化技术   106篇
  2023年   5篇
  2022年   5篇
  2021年   22篇
  2020年   18篇
  2019年   12篇
  2018年   31篇
  2017年   17篇
  2016年   24篇
  2015年   12篇
  2014年   18篇
  2013年   35篇
  2012年   38篇
  2011年   43篇
  2010年   21篇
  2009年   34篇
  2008年   39篇
  2007年   39篇
  2006年   24篇
  2005年   22篇
  2004年   29篇
  2003年   19篇
  2002年   15篇
  2001年   13篇
  2000年   12篇
  1999年   7篇
  1998年   28篇
  1997年   14篇
  1996年   11篇
  1995年   15篇
  1994年   11篇
  1993年   16篇
  1992年   8篇
  1990年   2篇
  1989年   7篇
  1988年   2篇
  1987年   6篇
  1986年   2篇
  1985年   6篇
  1984年   3篇
  1983年   3篇
  1982年   7篇
  1981年   8篇
  1980年   5篇
  1979年   3篇
  1978年   2篇
  1977年   3篇
  1976年   5篇
  1973年   5篇
  1971年   2篇
  1955年   1篇
排序方式: 共有733条查询结果,搜索用时 437 毫秒
81.
82.
It is widely recognized that many cost-efficient opportunities to employ end-use energy efficiency measures exist in countries in transition (CITs) and that municipal authorities have an essential role to play in capturing these opportunities. The aim of this paper is to review the factors that determine the degree of involvement of local authorities in the market for energy services and energy efficient (EE) equipment in three CITs: Bulgaria, Hungary and the Former Yugoslav Republic of Macedonia (hereafter: Macedonia). We achieve this aim by examining the current status of local governments as the most powerful determinant of municipal market involvement. Two broad groups of factors are discussed: statutory obligations and powers of local governments, especially energy-related tasks, and finance. We explain how specific features within these two areas may influence the motivation of local authorities to improve energy efficiency and their capacity to do so. We argue that greater decentralization is the first step in augmenting the role of local authorities in the market for energy services and EE equipment. Based on the analysis we give recommendations on how to encourage municipal authorities to use market mechanisms more extensively to deliver energy efficiency.  相似文献   
83.
84.
Little is known about the effects of depression on adherence to medical treatment regimens in older patients with chronic medical illnesses. Poor adherence may explain the increased risk of medical morbidity and mortality found in depressed medical patients. Ten of 55 patients over the age of 64 with coronary artery disease met the criteria for major depression from the Diagnostic and Statistical Manual of Mental Disorders (3rd ed., rev., American Psychiatric Association, 1987). All patients were prescribed a twice-per-day regimen of low dose aspirin to reduce their risk for myocardial infarction. Medication adherence was assessed for 3 weeks by an unobtrusive electronic monitoring device. Depressed patients adhered to the regimen on 45% of days, but nondepressed patients, on 69% (p?  相似文献   
85.
86.
This paper investigates the viability of increasing solar gains through the roof of an air-conditioned room using the thermal trap effect. In solving the heat conduction equations through the thermal trap and the concrete slab, the finite difference method has been employed and the initial conditions are derived from the assumption that, initially, the ceiling of the room and the top of the trap material are in equilibrium with constant room air temperature and the ambient air temperature, respectively. The effect of the thickness of the thermal trap and that of the concrete slab on the thermal flux transferred through the roof have been studied.  相似文献   
87.
In a companion paper in this issue (Pankow et al., 2010 [1]), experimental results for the deformation response of 3D glass fiber textile composites subjected to shock wave pulse pressure loading were presented. In this paper, finite element models are developed to simulate the deformation response and damage development observed in the experiments. Two levels of models are presented, with the first focused on a layered, homogenous orthotropic model that examined the bulk macroscopic deformation response. In the second model, each layer is represented to capture the interactions between fiber tows and matrix, taking into account the discrete non-homogeneous material distribution in each layer. Both models incorporated a user defined subroutine within the commercial software ABAQUS to capture matrix micro-cracking, which is responsible for damage development and growth. Results from the computational models correlated well with experimental results and observed locations of matrix micro-cracking.  相似文献   
88.
89.
The use of a "size-tunable" polyurethane resistive pulse sensor for quantitative sizing of nano- and microparticles is presented. A linear relationship, as first suggested by Maxwell, between particle volume and change in electric resistance across the pore was observed. Particle sizes were quantified for a given size-tunable membrane, by first creating a linear calibration curve to a series of monodisperse carboxylated polystyrene particles of various diameters and then applying this curve to calculate the size of "unknown" nanoparticles. The diameters of a selection of synthetic and biological particles, being PMMA and nonfunctionalized polystyrene particles, along with biological nanoparticles (adenovirus) were calculated using this methodology. Calculated particle diameters and coefficients of variation were shown to be in good agreement with both transmission electron microscopy and dynamic light scattering results.  相似文献   
90.
An Integrated program PEELFIT is reported for the Apple IIe microcomputer, which performs pharmacokinetic analysis for intravenous and first order absorption (oral or intramuscular) data. PEELFIT, written in basic language, uses plasma concentration and time for input. Upon the user's choice, it carries out non-linear regression on the data for curve fitting, according to a one or two compartment model. the curve fitting can be done with three weighting schemes. Parameters of the plasma concentration equations are obtained from the regression analysis and further, these are employed to calculate the relevant pharmacokinetic parameters. Finally, the percentage of dose absorbed (absorbable fraction) is calculated as a function of time. various known data were analysed with PEELFIT and the results obtained confirmed its accuracy.  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