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   29480篇
  免费   566篇
财政金融   5320篇
工业经济   2153篇
计划管理   4992篇
经济学   6652篇
综合类   310篇
运输经济   193篇
旅游经济   494篇
贸易经济   4550篇
农业经济   1410篇
经济概况   3901篇
邮电经济   71篇
  2021年   170篇
  2020年   285篇
  2019年   380篇
  2018年   552篇
  2017年   542篇
  2016年   509篇
  2015年   381篇
  2014年   581篇
  2013年   2830篇
  2012年   788篇
  2011年   853篇
  2010年   684篇
  2009年   810篇
  2008年   855篇
  2007年   775篇
  2006年   711篇
  2005年   666篇
  2004年   665篇
  2003年   648篇
  2002年   601篇
  2001年   607篇
  2000年   602篇
  1999年   521篇
  1998年   529篇
  1997年   506篇
  1996年   506篇
  1995年   458篇
  1994年   509篇
  1993年   513篇
  1992年   476篇
  1991年   500篇
  1990年   456篇
  1989年   380篇
  1988年   391篇
  1987年   384篇
  1986年   402篇
  1985年   575篇
  1984年   532篇
  1983年   535篇
  1982年   520篇
  1981年   447篇
  1980年   441篇
  1979年   453篇
  1978年   381篇
  1977年   344篇
  1976年   276篇
  1975年   268篇
  1974年   250篇
  1973年   239篇
  1972年   198篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
The REF, C, and score are a means to give quantitative values for product performance. Other product variables defined as humidity control factor, shear control factor, differential temperature control factor, product life factor, and cost factor were not addressed as part of this study. Additional variables include delivery, maintenance, and warranties. These components can be added to the score in some weighted manner as they become clinically founded. Interface pressures and shears were not measured for beds that are gatched. Each product tested will have characteristics pertinent to its own design that must be addressed to minimize sacral and coccyx skin breakdown when subjects are in this posture because some pneumatic pads bottom out to give excessive sacral and coccyx pressure while others wrinkle when used in this position. This is of major concern when one considers that the coccyx is more susceptible to pressure than any other bony prominence. There may be some aversion to labeling support product performance because it will allow the purchaser to know what is being bought. This initial study indicates the feasibility of quantitating what all patients require: a valid interface support surface for each specific need. The user can be adequately informed before the purchase as to a product's merits without being influenced by the results of inadequate testing, referrals, or sales media influences. Although cushions, shoes, or other prosthetic/orthotic devices were not part of this study, it is appropriate to rate all these devices in a similar manner by simply comparing pressure relief attained to that desired, expressing the result as a percentage of the worst case, and then labeling the product accordingly. Those subjects with sensation can rate comfort as part of the overall score. For cushions, ischial tuberosity pressure relief can be expressed as a percentage of the maximum attainable relief. Metatarsal head relief during gait as well as during static testing can be measured, and claims can be made for shoes and sneakers. Where impact loads and shear forces are paramount, the score must comprise appropriate parameters. Similarly, amputee distal stump relief as a percentage of worst case could be specified by the fitter. Iliac crest relief as a percentage of worst case can also be specified by the fitter. In all instances the score is not a subjective rating but one that can be measured correctly. All body support products can be given an REF, C value, and score as well as other qualifying values where appropriate instrumentation and sufficient subject sampling is used.  相似文献   
102.
103.
As older Americans take a close look at their assets, promote their interest in unlocking the wealth accumulation in their U.S. Saving Bond holdings. Use careful planning and advice when promoting this gift strategy.  相似文献   
104.
105.
106.
AIDS wars     
Kosterlitz J 《National journal》1992,24(30):1727-1732
At the Centers for Disease Control, director William L. Roper battles the deadly AIDS epidemic and other rising health hazards. But critics say political interference sets back the effort to stem AIDS.  相似文献   
107.
108.
109.
Issues such as global warming, ozone depletion, insufficient landfill capacity, and excess packaging are foremost on the minds of consumers. Companies face a myriad of environmental challenges, but they also recognize the opportunities to be gained by implementing responsible marketing action plans.  相似文献   
110.
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