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   1088篇
  免费   5篇
  国内免费   1篇
电工技术   11篇
化学工业   65篇
金属工艺   32篇
机械仪表   2篇
矿业工程   4篇
能源动力   1篇
轻工业   4篇
水利工程   4篇
石油天然气   27篇
无线电   17篇
一般工业技术   42篇
冶金工业   857篇
原子能技术   20篇
自动化技术   8篇
  2021年   11篇
  2020年   5篇
  2019年   5篇
  2018年   14篇
  2017年   8篇
  2016年   9篇
  2015年   4篇
  2014年   14篇
  2013年   11篇
  2012年   7篇
  2011年   10篇
  2010年   14篇
  2008年   2篇
  2007年   2篇
  2006年   2篇
  2004年   3篇
  2001年   6篇
  1999年   35篇
  1998年   246篇
  1997年   156篇
  1996年   94篇
  1995年   72篇
  1994年   51篇
  1993年   45篇
  1992年   8篇
  1991年   7篇
  1990年   9篇
  1989年   11篇
  1988年   14篇
  1987年   18篇
  1986年   22篇
  1985年   12篇
  1984年   4篇
  1983年   4篇
  1982年   8篇
  1981年   14篇
  1980年   14篇
  1979年   4篇
  1978年   6篇
  1977年   21篇
  1976年   57篇
  1975年   4篇
  1973年   2篇
  1972年   6篇
  1971年   3篇
  1970年   4篇
  1968年   2篇
  1966年   3篇
  1964年   2篇
  1959年   1篇
排序方式: 共有1094条查询结果,搜索用时 218 毫秒
11.
12.
Hepatocyte growth factor (HGF) is a potent mitogen for the maturation of hepatocytes in vitro which plays a role in liver regeneration in vivo. In addition, transforming growth factor-beta 1 (TGF-beta 1) is also a potent regulator of liver regeneration. In attempting to clarify the mechanisms related to liver regeneration after partial hepatectomy, we investigated the expression of HGF and TGF-beta 1 in rats with liver cirrhosis (LC). A rat model of LC was prepared using carbon tetrachloride (CCl4). The expression of HGF mRNA in both the LC and control groups showed a similar time-course with the highest expression seen at 18h after a 70% hepatectomy. The expression of TGF-beta 1 mRNA peaked at 18h after partial hepatectomy in the LC group and at 48h in the control group. The 5-bromo-2'-deoxyuridine (BrdU) labeling index for the LC group at 24, 48, and 72 h after partial hepatectomy was 9.2%, 5.9%, and 1.8%, while for the control group it was 7.0%, 11.7%, and 6.8%, respectively. The BrdU labeling index in the LC group was thus suppressed earlier than that in the control group. We therefore postulate that regeneration of the remnant liver in the presence of LC accelerates immediately after partial hepatectomy, but the extent of regeneration is insufficient because of an early cessation due to an early expression of TGF-beta 1.  相似文献   
13.
14.
15.
Clinical characteristics associated with bacillary angiomatosis and bacillary peliosis (BAP) in patients with human immunodeficiency virus (HIV) infection were evaluated in a case-control study; 42 case-patients and 84 controls were matched by clinical care institution. Case-patients presented with fever (temperature, > 37.8 degrees C; 93%), a median CD4 lymphocyte count of 21/mm3, cutaneous or subcutaneous vascular lesions (55%), lymphadenopathy (21%), and/or abdominal symptoms (24%). Many case-patients experienced long delays between medical evaluation and diagnosis of BAP (median, 4 weeks; range, 1 day to 24 months). Case-patients were more likely than controls to have fever, lymphadenopathy, hepatomegaly, splenomegaly, a low CD4 lymphocyte count, anemia, or an elevated serum level of alkaline phosphatase (AP) (P < .001). In multivariate analysis, a CD4 lymphocyte count of < 200/mm3 (matched odds ratio [OR], 9.9; P < .09), anemia reflected by a hematocrit value of < 0.36 (OR, 19.7; P < .04), and an elevated AP level of > or = 2.6 mukat/L (OR, 23.9; P < .05) remained associated with disease after therapy with zidovudine was controlled for. BAP should be considered an AIDS-defining opportunistic infection and should be included in the differential diagnosis for febrile, HIV-infected patients with cutaneous or osteolytic lesions, lymphadenopathy, abdominal symptoms, anemia, or an elevated serum level of AP.  相似文献   
16.
17.
18.
There is now strong evidence that the chorioretinal degeneration associated with ornithine-delta-aminotransferase (OAT) deficiency is a consequence of hyperornithinemia. Therefore development of a metabolic system for clearing ornithine from the circulation is being pursued as a potential treatment. The skin is considered an attractive location for such a metabolic system because autologous cells can be safely and easily utilized. This study was undertaken to determine the ornithine metabolizing capacity of epidermal keratinocytes expressing normal and superphysiologic amounts of OAT. The data show that overexpression of OAT in keratinocytes cultured from a gyrate atrophy patient restores ornithine metabolism and results in a rate of ornithine disappearance from the medium that is significantly higher than the rate of disappearance from the medium bathing normal keratinocytes. In addition, OAT activity determined in soluble protein prepared from sonicates suggests that the capacity to maintain plasma ornithine within the normal range is contained within an accomplishable graft of keratinocytes overexpressing OAT. However, the actual rate of ornithine disappearance from the media was significantly less than predicted from enzyme activity assays. Following ornithine metabolite production by intact cells suggests that ornithine metabolism is limited primarily by clearance of downstream metabolites, as opposed to substrate delivery.  相似文献   
19.
This study evaluated 36 cancer patients who were enrolled in a randomized, double-blind, placebo-controlled trial conducted over a 4-week period to evaluate the efficacy of alprazolam in the treatment of anxiety associated with cancer. Hamilton Anxiety Scale scores declined significantly between baseline and the end of the first week of the study in both treatment groups. There was no significant difference in response between the patients receiving alprazolam and placebo. Similar results were obtained from other instruments. These results suggest that nondrug factors or spontaneous improvement may play a more important role than pharmacotherapy in the treatment of anxiety associated with cancer.  相似文献   
20.
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