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   1056篇
  免费   4篇
电工技术   1篇
化学工业   30篇
金属工艺   2篇
机械仪表   1篇
建筑科学   11篇
能源动力   1篇
轻工业   9篇
石油天然气   1篇
无线电   13篇
一般工业技术   22篇
冶金工业   907篇
自动化技术   62篇
  2020年   2篇
  2019年   5篇
  2018年   2篇
  2017年   2篇
  2016年   2篇
  2015年   2篇
  2014年   24篇
  2013年   4篇
  2012年   10篇
  2011年   14篇
  2010年   12篇
  2009年   3篇
  2008年   2篇
  2007年   3篇
  2006年   7篇
  2005年   5篇
  2004年   2篇
  2003年   4篇
  2002年   4篇
  2000年   3篇
  1999年   33篇
  1998年   277篇
  1997年   150篇
  1996年   84篇
  1995年   53篇
  1994年   38篇
  1993年   48篇
  1992年   6篇
  1991年   17篇
  1990年   10篇
  1989年   12篇
  1988年   7篇
  1987年   6篇
  1986年   12篇
  1985年   8篇
  1983年   4篇
  1982年   8篇
  1981年   11篇
  1980年   11篇
  1979年   4篇
  1978年   3篇
  1977年   34篇
  1976年   90篇
  1975年   2篇
  1972年   2篇
  1971年   3篇
  1960年   1篇
  1959年   2篇
  1955年   2篇
  1954年   1篇
排序方式: 共有1060条查询结果,搜索用时 31 毫秒
101.
Since its emergence 25 years ago, group B streptococcus has become recognized as a cause of serious illness in newborns, pregnant women, and adults with chronic medical conditions. Heavy colonization of the genital tract with group B streptococcus also increases the risk that a woman will deliver a preterm low-birthweight infant. Early-onset infections (occurring at < 7 days of age) are associated with much lower fatality than when they were first described, and their incidence is finally decreasing as the use of preventive antibiotics during childbirth increases among women at risk. New serotypes of group B streptococcus have emerged as important pathogens in adults and newborns. Clinical and laboratory practices--in obstetrics, pediatrics, and clinical microbiology--have an impact on disease and/or its prevention, and protocols established at the institutional level appear to be critical tools for the reduction of perinatal disease due to group B streptococcus. Since intrapartum antibiotics will prevent at best only a portion of the full burden of group B streptococcal disease, critical developments in vaccine evaluation, including study of polysaccharide-protein conjugate vaccines, offer the potential for enhanced prevention in the relatively near future.  相似文献   
102.
103.
104.
105.
Fifteen Aberdeen Angus steers, 295-364 kg, were dosed with either 4.4 or 11 mg of oxytetracycline hydrochloride/kg im. The antimicrobial activity of the serum was determined periodically, and the resulting data were treated statistically to determine the sources of variation. Variance in serum levels of oxytetracycline activity was attributed to dose, time of bleeding, order of dosing, animal, and assay. The total variance component was proportionately greater for the 11-mg/kg dose than for the 4.4-mg/kg dose. Animal variance increased with the higher dose level of oxytetracycline. The influence of dose on serum level was tested by applying a t test to the mean serum levels and their standard deviations at each bleeding time. The 4.4- and 11-mg/kg serum levels were significantly different (p less than 0.01) at all bleeding times. The 4.4-mg/kg serum levels mutliplied by 2.5 were not significantly different (p less than 0.05) from the 11-mg/kg serum levels at all bleeding times.  相似文献   
106.
Sarcomas of the stomach   总被引:1,自引:0,他引:1  
Sarcomas of the gastric wall, other than lymphomas, are a heterogeneous group of stromal malignant neoplasms composed of round and spindle cells. Many are malignant forms of epithelioid leiomyoma. Small cell size, high cellular density, a high rate of mitotic activity, and cellular pleomorphism are helpful clues in distinguishing malignant from benign gastric stromal tumors. Sarcomas of the stomach are aggressive, rapidly growing neoplasms. Among 44 examples metastasis occurred in three-fourths of the patients, usually within the first year after diagnosis.  相似文献   
107.
METAL CUTTING or MACHINING plays a crucialrole in most manufacturing industries.New alloys andengineered materials that have to be machined are hard,tough,and abrasive and can also cause chemical wearof cutting tool materials.Depositing hard coatings on cutting tools is animportant development,which has enhanced cuttingtool performance as a result of providing higher wearresistance,lower friction,lower cutting forces,bettersurface finish of the workpieces,and longer tool life,which ena…  相似文献   
108.
A review was undertaken of (a) the levels and prevalence of Salmonella spp., Campylobacter spp., Listeria monocytogenes, Escherichia coli 0157. Cryptosporidium parvum and Giardia intestinalis in livestock manure, and (b) factors which affect their survival during storage and following land application. Pathogens are commonly present in livestock manures and can survive in soil for several months or years after spreading or excretion onto land. Temperature was identified as being the most important factor influencing pathogen survival, although pH, UV light and drying were also important. Various practical measures to minimise the risk of pathogen transfer into the food chain were identified, including treatment, extended storage and no/harvest periods following land spreading. Guidelines are being developed on managing farm manures to minimise the risks of microbiological contamination of ready-to-eat crops.  相似文献   
109.
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