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   5274篇
  免费   249篇
  国内免费   3篇
电工技术   43篇
综合类   4篇
化学工业   1060篇
金属工艺   79篇
机械仪表   98篇
建筑科学   186篇
矿业工程   30篇
能源动力   129篇
轻工业   414篇
水利工程   69篇
石油天然气   13篇
武器工业   1篇
无线电   420篇
一般工业技术   875篇
冶金工业   1236篇
原子能技术   34篇
自动化技术   835篇
  2023年   30篇
  2022年   46篇
  2021年   90篇
  2020年   71篇
  2019年   77篇
  2018年   83篇
  2017年   84篇
  2016年   115篇
  2015年   109篇
  2014年   168篇
  2013年   294篇
  2012年   261篇
  2011年   378篇
  2010年   268篇
  2009年   291篇
  2008年   314篇
  2007年   312篇
  2006年   253篇
  2005年   198篇
  2004年   186篇
  2003年   178篇
  2002年   158篇
  2001年   117篇
  2000年   113篇
  1999年   99篇
  1998年   98篇
  1997年   93篇
  1996年   86篇
  1995年   74篇
  1994年   76篇
  1993年   80篇
  1992年   50篇
  1991年   43篇
  1990年   53篇
  1989年   62篇
  1988年   51篇
  1987年   42篇
  1986年   38篇
  1985年   48篇
  1984年   48篇
  1983年   32篇
  1982年   30篇
  1981年   43篇
  1980年   22篇
  1979年   20篇
  1978年   36篇
  1977年   20篇
  1976年   23篇
  1975年   16篇
  1974年   15篇
排序方式: 共有5526条查询结果,搜索用时 9 毫秒
1.
2.
3.
This study, which is based on responses from over 300 individuals in England and Wales, explores how a willingness to use a water-recycling system of specific configuration varies against a number of factors which are linked to system design, system scale, system context, and water-conservation behaviour. Findings show that there is broad willingness to accept in-house water recycling provided that public health is not compromised.  相似文献   
4.
5.
Interest in medical savings accounts (MSAs) as a potential tool to reduce healthcare costs has been widespread. A small number of countries have either implemented or run pilot programs of MSAs, and vigorous policy debates have taken place in several other countries about the potential merits of introducing MSAs as a method of paying for health care. In this paper we develop a model to assess the cost saving potential of MSAs in a publicly funded healthcare system. We assume that the public healthcare payer may choose between reimbursing healthcare expenditures through an MSA or through a form of third‐party payer insurance. We use the model to identify the conditions under which MSAs may reduce costs. We illustrate using data on healthcare expenditures from Canada.  相似文献   
6.
A deterministic approach for downscaling ~ 40 km resolution Soil Moisture and Ocean Salinity (SMOS) observations is developed from 1 km resolution MODerate resolution Imaging Spectroradiometer (MODIS) data. To account for the lower soil moisture sensitivity of MODIS surface temperature compared to that of L-band brightness temperature, the disaggregation scale is fixed to 10 times the spatial resolution of MODIS thermal data (10 km). Four different analytic downscaling relationships are derived from MODIS and physically-based model predictions of soil evaporative efficiency. The four downscaling algorithms differ with regards to i) the assumed relationship (linear or nonlinear) between soil evaporative efficiency and near-surface soil moisture, and ii) the scale at which soil parameters are available (40 km or 10 km). The 1 km resolution airborne L-band brightness temperature from the National Airborne Field Experiment 2006 (NAFE'06) are used to generate a time series of eleven clear sky 40 km by 60 km near-surface soil moisture observations to represent SMOS pixels across the three-week experiment. The overall root mean square difference between downscaled and observed soil moisture varies between 1.4% v/v and 1.8% v/v depending on the downscaling algorithm used, with soil moisture values ranging from 0 to 15% v/v. The accuracy and robustness of the downscaling algorithms are discussed in terms of their assumptions and applicability to SMOS.  相似文献   
7.
The role of implicit theories in behavioral judgments continues to be a source of debate. In a study exploring the factorial validity of student ratings of instruction, Cadwell and Jenkins (1985) suggested that students' implicit theories of instructor behavior may account for the robust factor structure underlying student ratings. They argued that students rely on the semantic similarity of the rating items, inflating the observed relations among the items. Marsh and Groves cite methodological and conceptual difficulties with the Cadwell and Jenkins study, but most of these difficulties may arise from Marsh and Groves's misconceptions about the role of implicit theories and semantic similarities and, more generally, the cognitive processes underlying judgment tasks. I review these issues and address various points of Marsh and Groves's critique. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
8.
This study evaluated relations among optimism, perceived stress management skills (PSMS), and positive mood in 46 men who had surgical treatment for localized prostate cancer. The authors found that optimism, PSMS, and positive mood scores were positively correlated. Positive mood was unrelated to demographic and disease-related control variables. In a hierarchical regression model controlling for PSMS, the relationship between optimism and positive mood became nonsignificant, whereas PSMS remained a correlate of positive mood. Results suggest that the relationship between optimism and positive mood may be mediated by belief in being able to use stress management techniques effectively. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
9.
In developing an intelligent mobile construction robot, a navigation system that can provide an effective and efficient path-planning algorithm is a very important element. The purpose of a path-planning method for a mobile construction robot is to find a continuous collision-free path from the initial position of the construction robot to its target position. This paper presents an improved Bug-based algorithm, called SensBug, which can produce an effective path in an unknown environment with both stationary and movable obstacles. The contributions, which make it possible to generate an effective and short path, are an improved method to select local directions, a reverse mode, and a simple leaving condition. Some emerging technologies that can be used for implementing an intelligent construction robot are introduced in this paper.  相似文献   
10.
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