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   8502篇
  免费   1篇
  国内免费   1篇
电工技术   1篇
综合类   5篇
化学工业   38篇
金属工艺   5篇
建筑科学   3篇
能源动力   4篇
轻工业   13篇
水利工程   1篇
石油天然气   3篇
武器工业   1篇
无线电   20篇
一般工业技术   13篇
冶金工业   8367篇
原子能技术   1篇
自动化技术   29篇
  2020年   3篇
  2019年   1篇
  2017年   1篇
  2016年   2篇
  2014年   4篇
  2013年   3篇
  2012年   3篇
  2011年   4篇
  2010年   5篇
  2009年   8篇
  2008年   6篇
  2007年   9篇
  2006年   9篇
  2005年   11篇
  2004年   14篇
  2003年   14篇
  2002年   2篇
  2001年   4篇
  2000年   6篇
  1999年   279篇
  1998年   2680篇
  1997年   1484篇
  1996年   951篇
  1995年   549篇
  1994年   420篇
  1993年   526篇
  1992年   64篇
  1991年   103篇
  1990年   100篇
  1989年   87篇
  1988年   93篇
  1987年   91篇
  1986年   95篇
  1985年   65篇
  1984年   2篇
  1983年   9篇
  1982年   35篇
  1981年   38篇
  1980年   77篇
  1979年   2篇
  1978年   12篇
  1977年   182篇
  1976年   432篇
  1975年   9篇
  1963年   2篇
  1955年   7篇
  1954年   1篇
排序方式: 共有8504条查询结果,搜索用时 0 毫秒
91.
The treatment of alcoholism has changed during the past 2 decades. Notable developments have occurred in pharmacotherapy, psychotherapy, and health-care delivery. A better understanding of the biologic basis for addiction has led to clinical trials of medications that target neuroreceptors. One such medication is the opiate antagonist naltrexone, which decreases the craving for alcohol. Psychosocial interventions continue to be the mainstay of alcohol treatment programs. The efficacy of three different therapies was demonstrated in a study called Project MATCH (Matching Alcoholism Treatments to Client Heterogeneity). This study, however, did not prove the patient-treatment "matching" hypothesis. In addition to therapies provided by addiction specialists, interest is growing in the use of brief motivational techniques in primary-care settings. As the field of addiction responds to an unfolding health-care delivery system, a broader range of treatment options in conjunction with a greater opportunity to individualize patient care is evolving.  相似文献   
92.
93.
94.
短消息平台的原理与设计   总被引:15,自引:0,他引:15  
结合作者的实际工作经验,介绍了移动短消息的收发原理和短消息平台的体系结构、设计方法,并以本文作者负责组建的青岛短消息平台为例,介绍了其中的系统分析、系统设计、体系结构和功能构成等关键技术问题.  相似文献   
95.
Abstract. A new hybrid classifier is proposed which utilizes the advantages of the maximum likelihood classifier and the parallelepiped classifier. The new hybrid classifier reduces the processing time more substantially than the conventional one by introducing a lower boundary for each class. The rate of misclassification is comparable to that of maximum likelihood classifier. Performance of the conventional and the new method are compared by an example.  相似文献   
96.
Sprague-Dawley rats were exposed to 0.8 ppm ozone (O3), to 14.4 ppm nitrogen dioxide (NO2), or to both gases simultaneously for 6 h per day for up to 90 d. The extent of histopathologic changes within the central acinus of the lungs was compared after 7 or 78 to 90 d of exposure using morphometric analysis by placement of concentric arcs radiating outward from a single reference point at the level of the bronchiole- alveolar duct junction. Lesions in the lungs of rats exposed to the mixture of gases extended approximately twice as far into the acinus as in those exposed to each individual gas. The extent of tissue involvement was the same at 78 to 90 d as noted at 7 d in all exposure groups. At the end of exposure, in situ hybridization for procollagen types I and III demonstrated high levels of messenger RNA within central acini in the lungs of animals exposed to the combination of O3 and NO2. In contrast, animals exposed to each individual gas had a similar pattern of message expression compared with that seen in control animals, although centriacinar histologic changes were still significantly different from control animals. We conclude that the progressive pulmonary fibrosis that occurs in rats exposed to the combination of O3 and NO2 is due to sustained, elevated expression of the genes for procollagen types I and III. This effect at the gene level is correlated with the more severe histologic lesions seen in animals exposed to both O3 and NO2 compared with those exposed to each individual gas. In contrast, the sustained expression of the procollagen genes is not associated with a shift in the distribution of the lesions because the area of change in each group after 7 d of exposure was the same as after 78 to 90 d of exposure.  相似文献   
97.
98.
99.
100.
The tetrapeptide Ala-lle-Gly-Met bound to a Wang resin via the methionine residue was studied by NMR under MAS conditions and compared to the same peptide in solution. The bound peptide exhibits average linewidths superior to those observed for the peptide in solution. The origin of the residual NMR linewidth observed for the bound form was investigated. The dynamics of the peptide is shown to be only marginally responsible for the increased linewidth; the major cause of the line broadening appears to be nonaveraged magnetic susceptibility differences.  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