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   6495篇
  免费   2篇
电工技术   2篇
化学工业   13篇
建筑科学   3篇
轻工业   4篇
水利工程   1篇
石油天然气   1篇
无线电   7篇
一般工业技术   3篇
冶金工业   6454篇
自动化技术   9篇
  2024年   3篇
  2023年   1篇
  2021年   1篇
  2019年   2篇
  2015年   1篇
  2014年   1篇
  2007年   2篇
  2006年   1篇
  2005年   2篇
  2003年   9篇
  2001年   3篇
  2000年   3篇
  1999年   158篇
  1998年   1920篇
  1997年   1132篇
  1996年   755篇
  1995年   386篇
  1994年   344篇
  1993年   386篇
  1992年   49篇
  1991年   101篇
  1990年   104篇
  1989年   89篇
  1988年   101篇
  1987年   87篇
  1986年   76篇
  1985年   59篇
  1983年   12篇
  1982年   32篇
  1981年   47篇
  1980年   57篇
  1978年   26篇
  1977年   180篇
  1976年   350篇
  1975年   10篇
  1955年   4篇
  1954年   3篇
排序方式: 共有6497条查询结果,搜索用时 0 毫秒
41.
Of 96 cancers which have been detected as a result of the first annual screening of 10,470 volunteers, 46 have been clinically occult. Forty-one of these have been Stage 1 or less carcinoma, and 26 of these 41 have been minimal cancer. For the radiographic parameters used, the benefit of detecting these cancers vs. the risk of induced cancer is estimated as 103:1 and 65:1, respectively.  相似文献   
42.
Three convenience products--frozen, precooked chicken apple fritters, chicken breast fillets, and chicken patties--provided by one processor were subjectively evaluated by two taste panels of older adults, ranging in age from the sixties to middle eighties. The panelists represented a middle-income group maintaining private homes and a low-income group living in public housing. Both panels rated each product above "good" (score=4) or "fair" (score=3) on four acceptability factors and the overall score. Although mean scores of the low-income taste panel on all factors were generally higher for all products, the only significant difference (P less than .01) pertained to the appearance factor. Both panels indicated willingness to buy all three products.  相似文献   
43.
Conscious sheep with permanent indwelling cannulae in the lateral ventricles and the cisterna magna were Na depleted and then perfused for 9 h with an artificial CSF solution. There were 3 experimental groups: Group I (n=5) received perfusion with aritifical CSF containing NA 170 MEq./1, Group II (n=7) received perfusion with artificial CSF containing Na 145 mEq./1, Group III (n=7) received no perfusion. In Group I the blood aldosterone level fell from 26.4 +/- 7.4 to 8.6 +/- 2.3 ng/100 ml by 9 h after perfusion. There was no significant change in plasma [Na] or [K], blood angiotensin II or plasma renin concentration. Blood cortisol and corticosterone levels rose. There was also a fall in post-perfusion. Group III showed no significant change in blood aldosterone concentration. Multivariate statistical analysis showed that the fall in aldosterone levels during 170 mEq./l Na perfusion could not be accounted for by changes, either alone or together, of ACTH as evidenced by alteration in blood cortisol or corticosterone, or by change of plasma [Na], [K] or renin concentrations. This data supports the hypothesis of an additional factor which may be of CNS origin being involved in the control of aldosterone secretion.  相似文献   
44.
HLA antigens were examined by microdroplet lymphocyte cytotoxicity in 31 patients with Sj?grens syndrome. Fifty percent of 22 Causcasian patients (7 of 17 females and 4 of 5 males) had HLA-B8, as compared to 21% of 1205 controls (P=0.002). The presence of HLA-B8 was not correlated with parotid salivary flow, keratoconjunctivitis sicca, or focus score. Because of its association with a number of autoimmune diseases, including Sj?gren's syndrome, it is suggested that HLA-B8 is genetically liked to an immune response gene(s) that predisposes the individual to autoimmune phenomena. The expression of autoimmunity may be determined by infectious or environmental factors.  相似文献   
45.
46.
The anaphylactic shock of the rabbit is characterized by an acute right ventricular overload, accompanied by severe alterations of cardiac electrogenesis. During shock, the mean QRS vector, as measured from the algebraic sum of the Q, R, and S deflections on the three leads, shifts to the right, inferiorly and anteriorly. An injury current quickly appears. The TQ vector points away from the right ventricle. A progressive depolarization on the right ventricular wall is displayed by suction electrodes and the suppression of right ventricular hypertension by a cross circulation produces an almost immediate disappearance of the injury current. The geneses of these electrical alterations are briefly discussed. The possibility of an anaphylactic reaction at the level of the coronary arterial wall, previously mentioned in the literature, seems unlikely. The role of the haemodynamic changes and of the increased right ventricular blood pool is thought to be predominant.  相似文献   
47.
48.
Of 160 patients who underwent Nissen fundoplication for treatment of symptomatic peptic reflux esophagitis, five patients (3.1%) developed gastric ulcers. Four of these five patients experienced the "gas-bloat" syndrome. All ulcers were located on the lesser curvature of the stomach. Analyses of our experience with use of various types of hiatal hernia repair suggests that creation of the valvuloplastic mechanism unique to the Nissen procedure may be of etiologic significance in the development of gastric ulcers following this procedure.  相似文献   
49.
50.
The uni-arterial vascularisation of the lateral bilary duct makes it impossible to systematise the arteries which supply the common bile duct. Only the cystic artery is seen at coelio-mesenteric catheterization. The techniques essential for visualisation of the cystic artery are discussed, on the basis of one hundred coelio-mesenteric arteriograms: frequency of demonstration, origin, course, termination, calibre and length. The frequent finding of opacification of the wall of the gall bladder under normal conditions is stressed.  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