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   389篇
  免费   1篇
化学工业   1篇
机械仪表   1篇
轻工业   1篇
水利工程   1篇
冶金工业   386篇
  2016年   1篇
  2012年   1篇
  2005年   1篇
  1999年   7篇
  1998年   121篇
  1997年   63篇
  1996年   53篇
  1995年   25篇
  1994年   24篇
  1993年   24篇
  1992年   4篇
  1991年   3篇
  1990年   1篇
  1989年   2篇
  1988年   5篇
  1987年   1篇
  1986年   1篇
  1985年   1篇
  1983年   1篇
  1981年   5篇
  1980年   4篇
  1978年   1篇
  1977年   13篇
  1976年   27篇
  1975年   1篇
排序方式: 共有390条查询结果,搜索用时 0 毫秒
381.
At room temperature (23 degrees C-25 degrees C), the induction of long-term potentiation (LTP) in area CA1 of slices from young male Sprague-Dawley rats was depressed by preincubation with the nitric oxide synthase inhibitors NG-nitro-L-arginine (L-NA, 100 microM) and NG-nitro-L-arginine methyl ester (L-NAME, 100 microM). The D isomers were ineffective under the same conditions. Hemoglobin (20 microM) reduced but did not completely block LTP. Neither L-NA (at concentrations up to 1 mM) nor hemoglobin (20 microM) had any significant effect on LTP in slices from adult rats at room temperature, or in young rats at 29 degrees C-30 degrees C. These results suggest that nitric oxide is unlikely to play a role in the induction of LTP under physiological conditions.  相似文献   
382.
383.
384.
385.
386.
387.
388.
We investigated the effects of fish meal (FM) in beef cattle diets on growth performance, carcass characteristics, and fatty acid (FA) composition of longissimus muscle in 63 yearling steers (335 +/- 23 kg). High-moisture corn and alfalfa silage diets were supplemented with either a corn gluten/blood meal mixture or FM at 10% of the diet. Fish meal contained (as-is basis) 5.87 g/kg eicosapentaenoic acid (EPA) and 9.84 g/kg docosahexaenoic acid (DHA). Seven strategies were developed to feed either a control diet (no FM) or diets containing 5 or 10% FM with FM fed for either 56, 112, or 168 d before slaughter. Average daily gain and feed efficiency were not affected (P > .10) by FM feeding but DMI decreased. Within FM diets, cattle fed 5% FM consumed more (P < .01) DM and gained more (P < .02) than cattle fed 10% FM. Carcass traits were not affected (P > .05) by feeding strategy except for fatter (P < .05) and lower (P < .06) yielding carcasses in cattle fed 5 vs 10% FM diets. Fish meal feeding increased (P < .01) concentrations of (n-3) FA, including EPA and DHA, and decreased (P < .05) concentrations of arachidonic acid. Increasing the amount of dietary FM further increased (P < .01) concentrations of EPA and DHA and decreased (P < .05) concentrations of (n-6) FA. We estimate that a 114-g steak from cattle fed 10% FM would supply 35 to 90% of the current average daily intake of EPA and DHA in North America. The results indicate that FM may have a role in niche marketing of beef provided that eating quality is not compromised.  相似文献   
389.
The enzyme 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase (HMG-R) is the major rate-limiting enzyme of the mevalonate pathway in many organisms, including yeasts. In the yeast Saccharomyces cerevisiae, there are two isoenzymes of HMG-R (Hmg1p and Hmg2p). Both consist of an anchoring transmembrane domain and a catalytic domain. We have removed the known controlling features of HMG-R by overproducing the catalytic domain of Hmg1p. This overproduction leads to an enhancement of squalene production, implying that HMG-R has been deregulated. The enhancement is apparent under semianaerobic and aerobic conditions. Despite the increase in squalene production, the amount of ergosterol produced by the HMG-R-overproducing yeast was not increased. This result suggests the presence of another regulatory step between squalene and ergosterol formation. Squalene levels generated by cells overproducing the catalytic domain of HMG-R were estimated to be up to 10 times those produced by wild-type cells. The enhancement in squalene production coincided with a reduction in growth rate. This reduction may be a direct consequence of the buildup of high concentrations of squalene and presqualene intermediates of the pathway.  相似文献   
390.
The finding of a solitary pulmonary nodule is a frequent clinical problem. This article outlines the current recommendation for diagnostic management. Video-assisted thoracic surgery (VATS) has emerged as an excellent diagnostic tool that can reduce the incidence of thoracotomy for benign nodules while allowing expeditious treatment of early malignancies. The surgical techniques of VATS are discussed.  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