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   403778篇
  免费   4683篇
  国内免费   1364篇
电工技术   7569篇
综合类   316篇
化学工业   59827篇
金属工艺   16424篇
机械仪表   13490篇
建筑科学   8363篇
矿业工程   2154篇
能源动力   11531篇
轻工业   28465篇
水利工程   4266篇
石油天然气   7913篇
武器工业   17篇
无线电   49242篇
一般工业技术   82984篇
冶金工业   74979篇
原子能技术   9181篇
自动化技术   33104篇
  2022年   2551篇
  2021年   3885篇
  2020年   2943篇
  2019年   3804篇
  2018年   6482篇
  2017年   6478篇
  2016年   6924篇
  2015年   4319篇
  2014年   7134篇
  2013年   20025篇
  2012年   11410篇
  2011年   15265篇
  2010年   12143篇
  2009年   13713篇
  2008年   14049篇
  2007年   13813篇
  2006年   12422篇
  2005年   11115篇
  2004年   10505篇
  2003年   10419篇
  2002年   9828篇
  2001年   9736篇
  2000年   9135篇
  1999年   9520篇
  1998年   24335篇
  1997年   16714篇
  1996年   12799篇
  1995年   9519篇
  1994年   8363篇
  1993年   8380篇
  1992年   6054篇
  1991年   5694篇
  1990年   5680篇
  1989年   5318篇
  1988年   5045篇
  1987年   4421篇
  1986年   4300篇
  1985年   4813篇
  1984年   4422篇
  1983年   3995篇
  1982年   3654篇
  1981年   3730篇
  1980年   3430篇
  1979年   3326篇
  1978年   3336篇
  1977年   3750篇
  1976年   4849篇
  1975年   2850篇
  1974年   2663篇
  1973年   2730篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
961.
The degradation behaviour of Kodar [poly(1,4-cyclohexylene dimethyl-eneterephthalate)] was investigated in air using thermogravimetry, differential thermal analysis and wide angle X-ray diffraction studies. The rates of crystallization and degradation were influenced by thermal exposure and polychromatic irradiation (Λ > 290 nm) for different time intervals. The crystallinity changes (Xc%) and activation energies (ΔE) for the systems have been determined.  相似文献   
962.
963.
Postoperative feeding with a special-purpose foodstuff Ovolact proved superior to tube feeding in patients on after treatment following surgical correction of congenital jaw defects. This was evident from assessment of anthropometric and protein metabolism parameters. Nitrogen metabolism underwent positive changes reflecting the product value for maintenance of protein status of the above patients. Therefore, Ovolact can make more effective postoperative rehabilitation in jaw reconstruction.  相似文献   
964.
965.
The free energies of mixing of two networks in the interpenetrating polymer network based on crosslinked polyurethane and poly(ester acrylate) have been determined by the vapour sorption method. It was established that the constituent networks in the IPN are not miscible. The introduction of fillers of different chemical nature increases the compatibility. The thermodynamic affinity of the fillers to the individual networks and IPN was estimated. It was established that when the free energy of interaction of one or both components of the IPN with the filler is negative, reinforcement leads to the formation of a compatible and equilibrium system. For fillers having no affinity to the polymers, compatibilization is observed, which is connected with slowing down of phase separation in the system in the presence of filler.  相似文献   
966.
Knee ligamentous injuries occur during sport, and when there is extensive injury, they can be associated with subluxation or dislocation. We present the case of a female basketball player who sustained a knee dislocation during noncontact play. An immediate angiogram confirmed vascular integrity, and surgical treatment with ligamentous reconstruction was performed. Peroneal nerve injury was present but resolved in 42 weeks. A review of the literature discussing knee dislocation is presented.  相似文献   
967.
Translated from Khimicheskoe i Neftyanoe Mashinostroenie, No. 2, pp. 39–40, February, 1995.  相似文献   
968.
969.
Measurement of the flow stress of high density polyethylene (HDPE) and nylon 66 at strain rates of 103 s?1 using a split Hopkinson pressure bar technique is discussed. The flow stress at a strain of 10% has been determined for both polymers at 20°C. The intrinsic errors involved in this technique are briefly reviewed. The results indicate that the flow stress of HDPE and nylon 66 were 50MPa and 150MPa, respectively, at strain rates of about 103s?1.  相似文献   
970.
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