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   6800篇
  免费   1篇
  国内免费   1篇
化学工业   25篇
金属工艺   1篇
机械仪表   1篇
建筑科学   2篇
能源动力   1篇
轻工业   6篇
石油天然气   2篇
无线电   5篇
一般工业技术   31篇
冶金工业   6719篇
原子能技术   1篇
自动化技术   8篇
  2017年   1篇
  2014年   1篇
  2010年   1篇
  2009年   1篇
  2008年   2篇
  2007年   4篇
  2006年   3篇
  2005年   5篇
  2004年   10篇
  2003年   16篇
  2002年   2篇
  2001年   1篇
  2000年   6篇
  1999年   215篇
  1998年   2307篇
  1997年   1285篇
  1996年   809篇
  1995年   421篇
  1994年   336篇
  1993年   415篇
  1992年   37篇
  1991年   47篇
  1990年   53篇
  1989年   47篇
  1988年   54篇
  1987年   56篇
  1986年   53篇
  1985年   36篇
  1984年   1篇
  1983年   18篇
  1982年   24篇
  1981年   30篇
  1980年   61篇
  1979年   3篇
  1978年   13篇
  1977年   136篇
  1976年   277篇
  1975年   11篇
  1973年   1篇
  1955年   3篇
排序方式: 共有6802条查询结果,搜索用时 0 毫秒
71.
Stored human blood of varying age was passed through polyurethane foam (Bentley) micropore blood transfusion filters. Passage through these filters resulted in decreased screen filtration pressure (SFP) of the blood and increased filter weights. Numerous microaggregates were removed and SFP returned to normal after filtration. Occlusion of the filter occurred after passage of only 2 units of whole blood. On the basis of this research, we conclude that polyurethane foam (Bentley) micropore blood transfusion filters are effective in removal of microaggregates from stored human blood. Because the filtering capacity is not great, it is recommended that when these filters are used during transfusion a new filter be used for each unit of blood administered.  相似文献   
72.
We determined the relationship between mouth occlusion pressure and diaphragmatic electromyography during CO2 rebreathing with and without inspiratory flow resistance. Diaphragmatic electromyography was measured as a moving time average; occlusion pressures were measured 150 msec after onset of an inspiratory effort against a closed airway (P.15). P.15 versus diaphragmatic electromyographic plots during CO2 rebreathing with and without inspiratory flow resistance were linear. In 3 subjects the slope of P.15 versus diaphragmatic electromyography was unchanged with inspiratory flow resistance whereas in 3 others the slope increased, indicating greater inspiratory force for a given degree of diaphragmatic activity. We concluded that under unloaded conditions P.15 is a reliable index of respiratory neural output but may no longer reflect only inspiratory motoneuron drive during mechanical loading.  相似文献   
73.
74.
delta9-Tetrahydrocannabinol (THC) was compared with diphenylhydantoin (DPH), phenobarbital (PB) and chlordiazepoxide (CDP) using two electroshock procedures to determine anticonvulsant activity in mice, i.e., electroshock seizure threshold (EST) and the reduced EST caused by hyponatremia (injection of isotonic glucose). Using doses of each drug which were ineffective against MES, only CDP (10.0 mg/kg) was able to raise the EST by 20%. The lowered EST due to hyponatremia was reveresed by al four drugs. In these tests latency to convulsions and lethality associated with electroshock were more sensitive to THC.  相似文献   
75.
76.
77.
The adult cuticular wing of Drosophila is covered by an array of distally pointing hairs that reveals the planar polarity of the wing. We report here that mutations in dachsous disrupt this regular pattern, and do so by affecting frizzled signaling. dachsous encodes a large membrane protein that contains many cadherin domains and dachsous mutations cause deformed body parts. We found that mutations in dachsous also result in a tissue polarity phenotype that at the cellular level is similar to frizzled, dishevelled and prickle, as many cells form a single hair of abnormal polarity. Although their cellular phenotype is similar to frizzled, dishevelled and prickle, dachsous mutant wings display a unique and distinctive abnormal hair polarity pattern including regions of reversed polarity. The development of this pattern requires the function of frizzled pathway genes suggesting that in a dachsous mutant the frizzled pathway is functioning - but in an abnormal way. Genetic experiments indicated that dachsous was not required for the intracellular transduction of the frizzled signal. However, we found that dachsous clones disrupted the polarity of neighboring wild-type cells suggesting the possibility that dachsous affected the intercellular signaling function of frizzled. Consistent with this hypothesis we found that frizzled clones in a dachsous mutant background displayed enhanced domineering non-autonomy, and that the anatomical direction of this domineering non-autonomy was altered in regions of dachsous wings that have abnormal hair polarity. The direction of this domineering nonautonomy was coincident with the direction of the abnormal hair polarity. We conclude that dachsous causes a tissue polarity phenotype because it alters the direction of frizzled signaling.  相似文献   
78.
OBJECTIVE: To investigate the production of proinflammatory cytokines and expression of cell adhesion molecules in the rheumatoid nodule. METHODS: Cytokine content (tumor necrosis factor alpha [TNFalpha], interleukin-1beta [IL-1beta], and IL-1 receptor antagonist [IL-1Ra]), at the messenger RNA (mRNA) and protein levels, and cell adhesion molecule expression were studied in 16 rheumatoid nodules and 6 synovial membranes. RESULTS: Macrophages in the rheumatoid nodules contained TNFalpha, IL-1beta, and IL-1Ra mRNA and protein, particularly in perivascular cells of the stroma and in the palisading layer. All cell adhesion molecules studied were expressed in both the rheumatoid nodules and synovial membranes, with increased expression of E-selectin in the rheumatoid nodule compared with the synovial membrane, and with the absence of vascular cell adhesion molecule 1 expression on cells of the palisading layer in the rheumatoid nodule. CONCLUSION: The presence of similar proinflammatory cytokines and cell adhesion molecules in the rheumatoid nodule and synovial membrane suggests that similar pathogenic processes result in the chronic inflammation and tissue destruction in these lesions.  相似文献   
79.
80.
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