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   1411篇
  免费   0篇
  国内免费   1篇
电工技术   2篇
化学工业   5篇
金属工艺   1篇
石油天然气   2篇
无线电   1篇
一般工业技术   2篇
冶金工业   1399篇
  2018年   1篇
  2010年   1篇
  2007年   1篇
  2005年   1篇
  2004年   3篇
  2003年   1篇
  2000年   1篇
  1999年   54篇
  1998年   433篇
  1997年   245篇
  1996年   175篇
  1995年   76篇
  1994年   80篇
  1993年   72篇
  1992年   8篇
  1991年   15篇
  1990年   19篇
  1989年   24篇
  1988年   17篇
  1987年   12篇
  1986年   18篇
  1985年   12篇
  1983年   1篇
  1982年   4篇
  1981年   8篇
  1980年   14篇
  1978年   3篇
  1977年   35篇
  1976年   74篇
  1975年   4篇
排序方式: 共有1412条查询结果,搜索用时 11 毫秒
991.
992.
Studies aimed at the detection of cytomegalovirus infection (CMVI) in women of reproductive age with obstetric complications in their medical history were carried out. 230 women aged 17-44 years were examined with the use of virological and serological tests. As the result of complex examination, CMVI markers were detected in 159 (69%) of women. Three forms of CMVI were detected in the examined women: latent (30%), reactivated (14%) and persistent (25%). This investigation revealed that the most complete detection of CMVI and the evaluation of its activity in women with obstetric complications in their medical history requires the combined use of virological and serological tests.  相似文献   
993.
Bioactivity-guided fractionation of the petroleum ether extract of Azorella madreporica Clos has led to the isolation of the novel, antitubercular mulinane diterpenoid 1. The structure has been elucidated on the basis of its 1D and 2D NMR spectra and by comparison with mulinolic acid 2 and a dehydration product 3 obtained from 1. The MIC of 1 for growth inhibition of the H37Rv strain of Mycobacterium tuberculosis was determined as 20 microg/mL. LC-MS and NMR have suggested the presence of this new compound in four other species of Azorella.  相似文献   
994.
995.
Myogenic satellite cell clones were established from the pectoralis major muscle of chickens with the low score normal (LSN) muscle weakness and controls. The percentage of cells which attached to substrata and began to proliferate was higher for the control line than the LSN line (55% vs 30%). Furthermore, of those clones which initiated growth, 63% of the control cells and only 32% of the LSN cells proliferated to confluence in 25 cm2 tissue culture flasks. Proliferation rates were significantly lower with LSN satellite cells than with controls (p < 0.05). LSN satellite cells were less responsive to the mitogenic effects of chicken serum (p < 0.05) and differentiation rates were lower compared with controls (p < 0.05). There was a greater (p < 0.05) number of insulin-like growth factor receptors on LSN satellite cells compared with controls. The IGF receptor binding affinities (Kds) between the two cell lines were similar (p > 0.05). The results suggest that a defect in satellite cell physiology may contribute to the skeletal muscle weakness seen in the LSN line.  相似文献   
996.
997.
998.
999.
An experimental study was undertaken in dogs with carbon tetrachloride (CCl4) intoxication to describe and follow the changes in the ultrasound appearance of the liver. Characteristic ultrasound features (enlarged liver, increased echogenicity with fine, tightly-packed echoes, and loss of echogenicity of the portal vein walls) were seen from day 2 of the experiment, culminating between days 2 and 7. Subsequently the liver gradually and almost completely regained its normal ultrasound appearance. Ultrasonographic findings corresponded to the severity of the clinicopathological parameters, and changed parallel with the results of liver biopsies. Histology of the biopsy samples revealed acute centrolobular lipid accumulation with necrobiosis and necrosis in the hepatocytes in the first stage of the disease. In the second stage, a secondary reparatory-inflammatory process and reparation in the interstitial tissue were seen. In some dogs, ill-defined hyperechoic foci were observed within the liver during the regenerative phase. Hepatic ultrasonography seems to be a reliable and relatively sensitive method for monitoring liver dystrophy with necrobiosis and lipid accumulation and to follow the course of steatosis in clinical cases. Ultrasound-guided biopsy can further improve the diagnostic accuracy of ultrasonography in liver dystrophy.  相似文献   
1000.
The accuracy of computed tomography (CT) and [99mTc]HMPAO granulocyte scintigraphy (GS) for detection of bowel localization, inflammatory activity, and complications in acute inflammatory bowel disease (IBD) was prospectively studied in 32 patients. Of each bowel segment, findings on CT and GS were scored by one blinded observer. Findings on operation or endoscopy served as the gold standard. In Crohn's disease (CD, 17 patients), CT detected bowel pathology (sensitivity 71%, specificity 98%), abscesses (sensitivity and specificity 100%), and fistulas (sensitivity 80%, specificity 100%). In CD, GS had a sensitive of 79% and a specificity of 98% for detection of inflammatory activity. The detection of complications with GS was poor. Segmental inflammatory activity correlated with endoscopy-operative findings for CT (r = 0/86, P < 0.0001) and GS (r = 0.86, P < 0.0001). In ulcerative colitis (UC, 15 patients), GS predicted proximal extension of bowel involvement better than CT. In CD, CT is Superior to GS for localization of both active and fibrostenotic bowel disease, and in detection of the abscesses and fistulas. In UC, GS showed proximal extension more accurately than CT.  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