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   1497篇
  免费   1篇
综合类   2篇
化学工业   4篇
金属工艺   2篇
机械仪表   4篇
建筑科学   11篇
能源动力   2篇
轻工业   1篇
无线电   3篇
一般工业技术   13篇
冶金工业   1449篇
自动化技术   7篇
  2020年   1篇
  2018年   3篇
  2017年   1篇
  2014年   1篇
  2013年   6篇
  2012年   2篇
  2011年   1篇
  2008年   3篇
  2006年   1篇
  2005年   1篇
  2004年   1篇
  2003年   4篇
  2001年   1篇
  1999年   49篇
  1998年   465篇
  1997年   255篇
  1996年   146篇
  1995年   95篇
  1994年   88篇
  1993年   87篇
  1992年   21篇
  1991年   16篇
  1990年   19篇
  1989年   12篇
  1988年   14篇
  1987年   14篇
  1986年   10篇
  1985年   15篇
  1983年   4篇
  1982年   4篇
  1981年   8篇
  1980年   17篇
  1978年   6篇
  1977年   37篇
  1976年   81篇
  1975年   3篇
  1974年   1篇
  1971年   1篇
  1970年   1篇
  1967年   2篇
  1955年   1篇
排序方式: 共有1498条查询结果,搜索用时 11 毫秒
91.
Individual total body water volumes for 458 adult males and 265 adult females obtained from dilution studies, together with their height, weight, and age have been selected from the literature. These values were used to derive total body water prediction equations for adults of any age. The equations that gave the best fit were for males: formula (see text) and for females: formula (see text). Numerous other linear regression equations to predict total body water from anthropometric measurements have been reported in the literature. Most apply only to restricted age groups. These, and the equations from the present study were tested on completely independent data. In all cases the equations from the present study gave the best overall results, though for women one equation designed for a specific age group, gave for that age group a marginally better fit.  相似文献   
92.
93.
94.
BACKGROUND: Transmyocardial laser revascularization is a new therapy for patients with refractory angina. Although clinical studies suggest that transmyocardial laser revascularization decreases angina and may improve regional blood flow, the underlying mechanisms are not elucidated. We hypothesized that one mechanism may relate to stimulation of vascular growth in laser-treated regions. METHODS: Transmyocardial laser revascularization channels were made with holmium:yttrium-aluminum garnet or carbon dioxide lasers in eight normal canine hearts; animals were sacrificed 2 to 3 weeks later and examined for vascular density and for evidence of smooth muscle proliferation. RESULTS: The original channels were infiltrated by granulation tissue with associated vascularity. Vascular growth was stimulated immediately surrounding the channel remnant as evidenced by an increase in the number of vessels (approximately twice that of the control region) and an increase in the number of vascular cells staining positive for markers of cellular proliferation. CONCLUSIONS: Transmyocardial laser revascularization leads to local vascular growth as early as 2 weeks after treatment. It remains to be determined whether this mechanism contributes to increased regional blood flow or to clinical benefits associated with this novel form of therapy.  相似文献   
95.
The HIV-1 transactivator protein Tat is essential for viral gene expression and replication. Tat is taken up by cells and transactivates the HIV-LTR promoter in the cell nucleus. The present studies show that cells adhere to both synthetic and recombinant Tat, and, using synthetic peptides, we localize the binding site to a region spanning amino acid residues 49-57 (peptide Tat49-57). Tat49-57 also inhibited cell attachment to solid phase full-length Tat peptide and to recombinant Tat protein. Using Tat peptide affinity chromatography, we identified a 90-kDa cell surface protein that binds to Tat. The 90-kDa protein could be eluted from the Tat column using the Tat49-57 peptide. A 90-kDa cell surface Tat binding protein was also identified by coprecipitation with Tat after incubation with radiolabeled cell membrane preparations. Co-precipitation of the 90-kDa protein was inhibited by competition with a Tat49-65 peptide, but not with Tat55-86. Our findings suggest that cellular attachment to Tat is mediated through a 90-kDa cell surface protein that binds to a Tat domain between amino acids 49 and 57.  相似文献   
96.
97.
The aglycone, 3-hydroxybenzo[a]pyrene, was metabolized to 3-benzo[a]pyrenyl-beta-D-glucopyranosiduronic acid in the presence of uridine 5'-diphosphoglucuronic acid and rabbit liver microsomes. The course of the biosynthetic reaction was followed by fluorimetry and reverse-phase, paired-ion high pressure liquid chromatography (HPLC). Also, the HPLC system was used to analyze for glucuronide and 3-hydroxybenzo[a]pyrene during the isolation procedure. The existence of a glucuronide of 3-hydroxybenzo[a]pyrene was determined by radiotracer and enzymic techniques, utilizing the HPLC system. Field desorption and direct inlet mass spectral techniques were used to characterize the 3-hydroxybenzo[a]pyrene glucuronide.  相似文献   
98.
99.
L’ AMBRIŠKO  L PEŠEK 《Sadhana》2014,39(2):525-530
The paper deals with an experimental determination of the stretch zone dimensions in the notch tip in thin steel sheets. The stretch zone dimensions depend on steel grade, on the rolling direction as well as on the loading rate. Stretch zones were observed and measured on three steel grades. Fracture area and stretch zones were analysed by SEM. Stable crack growth was monitored by videoextensometry techniques on CT (Compact Tension) specimens. Specimens were loaded under two loading rates by eccentric tension, whereby the deformation in the notch surrounding area was recorded using a non-contact measurement–videoextensometry technique. Linear relation between the stretch zone dimensions was determined.  相似文献   
100.
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