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   3920篇
  免费   2篇
电工技术   6篇
化学工业   16篇
机械仪表   3篇
轻工业   26篇
水利工程   1篇
无线电   6篇
一般工业技术   9篇
冶金工业   3839篇
自动化技术   16篇
  2019年   1篇
  2018年   1篇
  2017年   2篇
  2016年   1篇
  2015年   1篇
  2013年   2篇
  2012年   7篇
  2011年   3篇
  2010年   1篇
  2009年   2篇
  2008年   4篇
  2006年   5篇
  2005年   1篇
  2004年   5篇
  2003年   16篇
  2000年   2篇
  1999年   141篇
  1998年   1263篇
  1997年   781篇
  1996年   481篇
  1995年   233篇
  1994年   220篇
  1993年   221篇
  1992年   20篇
  1991年   32篇
  1990年   35篇
  1989年   47篇
  1988年   31篇
  1987年   28篇
  1986年   22篇
  1985年   24篇
  1984年   4篇
  1983年   6篇
  1982年   15篇
  1981年   23篇
  1980年   29篇
  1979年   4篇
  1978年   5篇
  1977年   59篇
  1976年   136篇
  1975年   2篇
  1973年   1篇
  1970年   2篇
  1963年   1篇
  1929年   1篇
  1928年   1篇
排序方式: 共有3922条查询结果,搜索用时 0 毫秒
41.
For the purpose of assigning priorities for research, each of the following parasitic disease is examined in regard to its affect on the nutritional status of the host: schistosomiasis, malaria, amebiasis, giardiasis, ascariasis, and hookworm. The epidemiology, diagnosis, immune response to, and available therapies for these diseases are discussed. It is suggested that highest priority be given to three diseases: hookworm, ascariasis, and schistosomiasis, because they can be treated successfully, diagnosed easily, and have a high prevalence.  相似文献   
42.
43.
44.
The macroscopic courses of the posterior primary rami in the lumbar spine are described and illustrated from fresh cadaver dissections.  相似文献   
45.
46.
47.
Reported are the environmental and demographic risk factors associated with the domestic infestation and density of Triatoma infestans in three heavily infested rural villages in Santiago del Estero Province, Argentina. In a one-factor unadjusted analysis, the number of T. infestans captured per person-hour was associated significantly and negatively with the use of domestic insecticides by householders, type of thatch used in the roofs and the age of the house; and positively with the following: degree of cracking of the indoor walls and presence of hens nesting indoors. In one model, using multiple linear regression and a backward stepwise elimination procedure, most of the variation in the overall abundance of T. infestans was explained by insecticide use and the presence of hens nesting indoors; in another model using the same procedure it was explained by insecticide use, bug density in 1988 and previous spraying with deltamethrin in 1985. Variations in bug density per capture stratum (household goods, beds, walls and roof) were explained by the bug density in other strata and by one or two of the following risk factors: hens nesting indoors, type of roof, presence of cracks in the walls and number of people living in the house. Bug density might be locally controlled by the availability of refuges in the roofs and walls, by the presence of hens nesting indoors and by the use of domestic insecticides. Certain local materials, such as a grass known as simbol, could be successfully used in rural housing improvement programmes aimed at reducing the availability of refuges for insects in the roof.  相似文献   
48.
49.
50.
The ability of the juvenile female reproductive axis to respond to hormonal stimulation was investigated in a Perciform fish, the striped bass (Morone saxatilis) using various combinations of testosterone (T), GnRH agonist (GnRHa), and pimozide. A long-term treatment with T alone, or T in combination with GnRHa, increased pituitary gonadotropin II (GtH II) levels 2- and 3-fold, respectively, suggesting that T and GnRHa each stimulate GtH II accumulation. Release of the accumulated GtH II could be induced only by high doses of GnRHa in combination with T, indicating that GtH II synthesis and release require different levels of GnRH stimulation. The addition of the dopamine antagonist pimozide did not affect pituitary and plasma GtH II levels but, in response to an additional acute GnRHa challenge, inhibited the release of GtH II. Although ovarian development was slightly stimulated by a combined T and GnRHa treatment, vitellogenesis was generally not initiated. The present study demonstrated that the juvenile striped bass pituitary is responsive to hormonal stimulation, resulting in elevated levels of GtH II in the pituitary and plasma. However, increased plasma levels of GtH II did not result in precocious puberty, suggesting that additional factors are required for the initiation of ovarian development in this teleost.  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