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   349776篇
  免费   39706篇
  国内免费   374篇
  2018年   3133篇
  2017年   2960篇
  2016年   4252篇
  2015年   5789篇
  2014年   6780篇
  2013年   9398篇
  2012年   10706篇
  2011年   10790篇
  2010年   7280篇
  2009年   6606篇
  2008年   9456篇
  2007年   9858篇
  2006年   9141篇
  2005年   8774篇
  2004年   8461篇
  2003年   8195篇
  2002年   8202篇
  2001年   20032篇
  2000年   20082篇
  1999年   15321篇
  1998年   4608篇
  1997年   4899篇
  1996年   4632篇
  1995年   4330篇
  1994年   4174篇
  1993年   3982篇
  1992年   12113篇
  1991年   11639篇
  1990年   11117篇
  1989年   10584篇
  1988年   9765篇
  1987年   9068篇
  1986年   8255篇
  1985年   8096篇
  1984年   6482篇
  1983年   5629篇
  1982年   4155篇
  1981年   3644篇
  1980年   3396篇
  1979年   6155篇
  1978年   4603篇
  1977年   4159篇
  1976年   3794篇
  1975年   4356篇
  1974年   4528篇
  1973年   4432篇
  1972年   4122篇
  1971年   3516篇
  1970年   3196篇
  1969年   2995篇
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
991.
992.
This study was presented in part at the annual meeting of the Wilderness Medical Society at Aspen, Colorado, in August 1986 and at “Mountain Medicine 1987,” Leavenworth, Washington, in November 1987.We questioned 220 injured rock climbers or their partners seen consecutively at the Yosemite (California) Medical Clinic over 3 ½ years regarding details of their accidents. Injury type and location were extracted from medical records and severity quantified. The National Park Service rescued 27% of the climbers. Injured climbers were characteristically male (88%) and experienced (mean 5.9 years) and typically fell while leading climbs (66%). Among 451 injuries, 50% were to the skin or subcutaneous tissues, while 28% involved the lower extremity and were predominantly fractures. In terms of each climber''s most severe injury (n = 220), 45% involved the lower extremities (30% from the ankle alone). Head injury or hypothermia caused 12 of 13 fatalities, showing the lowest case-fatality rate reported to date among injured climbers (6%). Rescue personnel successfully managed airways in victims of head injuries, anticipated and treated complications of hypothermia, and stabilized fractures. Victims requiring immediate extensive surgical intervention or blood transfusion usually died before rescue could be effected.  相似文献   
993.
Eriocaulon raipurense (Eriocaulaceae) is described and illustrated as a new species from Madhya Pradesh, India. The species is closely allied to E. hamiltonianum but differs in the size and apex of involucral bancts, white-pilose nature of floral bracts and colour of female petals.  相似文献   
994.
The effects of certain physicochemical parameters on the formation and stability of a complex between Streptomyces proteinaceous metalloprotease inhibitor (SMPI) and thermolysin were investigated. SMPI had its lowest Ki value at a pH of around 6.5 (similar to the pH dependence of the kcat/K(m) of thermolysin catalysis), reflecting the splitting mechanism of the SMPI inhibition of thermolysin. This Ki increased with an increase in pressure, and in (Ki-1) was almost linear with respect to pressure. The volume of the reaction (delta Vcomp), which is the volume change accompanying enzyme-inhibitor complex formation, was calculated as +8.1 +/- 0.3 mL.mol-1, which has a sign opposite to delta Vcomp for neutral peptide inhibitors and acyl-peptide substrates. The temperature dependence of Ki-1 gave the reaction enthalpy (delta Hcomp) and reaction entropy (delta Scomp) of the complex formation as 34.6 +/- 1.4 kJ.mol-1 and 298 +/- 5 J.mol-1.K-1, respectively. These positive reaction volumes and reaction entropies were related to the electrostatic interactions and ionic strength dependence of Ki which corresponded to the key ionic interaction during complex formation. Complex formation with SMPI stabilized thermolysin against pressure perturbation as observed by the changes in the Trp fluorescence of thermolysin with increasing pressure. Thermal stability, however, was affected very little by complex formation with SMPI. Phosphoramidon, Cbz-Phe-Gly-NH2 and Cbz-Phe also positively affected the pressure-tolerance of thermolysin, in the following order: Cbz-Gly-Phe-NH2 < Cbz-Phe < phosphoramidon. The third compound exhibited stabilizing effects comparable with those of SMPI, which suggests that the interaction between SMPI and thermolysin was localized to the reactive site.  相似文献   
995.
996.
997.
998.
999.
1000.
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