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   894篇
  免费   2篇
电工技术   2篇
化学工业   5篇
机械仪表   2篇
矿业工程   1篇
轻工业   5篇
石油天然气   1篇
无线电   2篇
一般工业技术   9篇
冶金工业   861篇
自动化技术   8篇
  2023年   1篇
  2022年   1篇
  2021年   2篇
  2017年   1篇
  2016年   2篇
  2015年   1篇
  2014年   2篇
  2013年   5篇
  2012年   2篇
  2011年   1篇
  2010年   1篇
  2009年   2篇
  2008年   1篇
  2007年   1篇
  2005年   1篇
  2004年   1篇
  1999年   11篇
  1998年   176篇
  1997年   118篇
  1996年   94篇
  1995年   54篇
  1994年   58篇
  1993年   49篇
  1992年   13篇
  1991年   4篇
  1990年   8篇
  1989年   1篇
  1988年   2篇
  1987年   3篇
  1986年   1篇
  1985年   1篇
  1984年   1篇
  1983年   3篇
  1982年   6篇
  1981年   16篇
  1980年   19篇
  1978年   4篇
  1977年   97篇
  1976年   127篇
  1975年   3篇
  1954年   1篇
  1899年   1篇
排序方式: 共有896条查询结果,搜索用时 15 毫秒
91.
92.
The age dynamics of haptoglobin (Hp) type and allele distribution was studied in 985 workers aged 35-79 years who worked in the atomic industry. These workers were exposed to chronic radiation in a wide range of doses 17-40 years ago. Along with the chi 2 test, the relative and attributive risks of elimination of Hp types and alleles were determined to obtain the qualitative characteristics of age alterations. The substantial changes in distribution of Hp types and alleles were revealed in individuals older than 60 years. These changes depended on doses of external and internal irradiation. For instance, in individuals of this age group, who received the total dose of gamma-radiation (less than 100 cGy) and or that of plutonium-239 incorporation (less than 1.48 kBq), a decrease in Hp 2-2 and Hp2 and an increase in Hp 1-1 and Hp1 was observed. However, among the individuals of similar age (older than 62 years), who received a higher total dose of external and/or internal radiation, the different Hp type distribution showed a decrease in Hp 2-1 and an increase in Hp 1-1. In the latter case, the changes with age were dose-dependent. In individuals over 60 years of age with essential hypertension or diabetes mellitus and those who had a myocardial infarction, a decrease in Hp 2-2 and Hp2 and an increase in Hp 1-1 and Hp1 were found. This explains the changes with age in individuals irradiated at lower doses. The peculiar changes with age in individuals irradiated at higher doses are possibly due to the difference in morbidity and mortality from malignancy in various Hp type carriers.  相似文献   
93.
94.
95.
The dynamics of the transition of Y.pseudotuberculosis to the latent (noncultivable) state in sterile soil extraction and in soil extraction, containing Scenedesmus algae or their exometabolites, was evaluated by the bacteriological method and with the use of polymerase chain reaction. The formation of Y.pseudotuberculosis latent forms achieved its highest rate under the action of algal exometabolites (on day 11), while in the presence of algal cells such formation was delayed to 3-5 months. The partial reversion of Y.pseudotuberculosis nonculativable forms to vegetative, bacteriologically detectable forms occurred under the action of fetal serum, as well as live or killed infusoria. Transmission electron microscopy demonstrated that noncultivable Y.pseudotuberculosis had a round form, diminished cell size, denser cytoplasm and enlarged cytoplasmic space. The reversible transition of bacteria to the latent state is regarded as their adaptation to unfavorable factors during their existence in soils and water reservoirs.  相似文献   
96.
97.
Destructive changes in cardiomyocyte mitochondria of patients with diagnosis of alcoholic heart lesion were observed by the ultrastructural analysis of the endocardial biopsies serial sections. The appearance of mitochondria with the third additional compartment and mitochondria having two zones of different electron density not separated into the special compartments are described for the first time. The development of megamitochondria having different morphology is demonstrated. Mitochondrial origin of lipophuscin granules is suggested on the basis of the ultrastructural changes. Unusual structure of atypical mitochondria may provide new properties of these organelles this being considered by the authors as an adaptive cell and mitochondria response to the new metabolic conditions.  相似文献   
98.
99.
Blepharoptosis is a recognized complication of cataract extraction and other ocular procedures. A 6-month waiting period is recommended before repairing postcataract ptosis because most cases resolve during this time. We report the course of a patient who developed spontaneous recovery of eyelid function 11 months after cataract surgery. She had previously undergone successful ptosis repair 8 months after cataract extraction, but developed overcorrection 3 months later as her levator function returned to normal. We recommend at least a 1-year waiting period before repair of postcataract ptosis. If corrective surgery is undertaken earlier than 1 year due to visual obstruction or for aesthetic reasons, we suggest two guidelines. The levator should be plicated rather than resected and patients should be forewarned of the possibility for a revisionary procedure if spontaneous return of levator function occurs.  相似文献   
100.
Populations of Arabidopsis thaliana (L.) Heynh., and Pinus sylvestris L., growing within 30 km of Chernobyl and Bryansk region have been analyzed for the frequency of embryonic lethal mutations on Arabidopsis and frequency of chlorophyll mutations and chromosome aberrations by pine. On pine also have been analyzed rate of mutations at enzyme loci in endosperms of seeds. Dose dependence of the value genetic damage on level of radioactive pollution was observed.  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