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   942篇
  免费   0篇
电工技术   2篇
化学工业   35篇
金属工艺   8篇
机械仪表   2篇
建筑科学   10篇
矿业工程   1篇
轻工业   11篇
水利工程   3篇
石油天然气   6篇
无线电   8篇
一般工业技术   21篇
冶金工业   835篇
  2022年   2篇
  2021年   8篇
  2020年   4篇
  2019年   4篇
  2018年   3篇
  2017年   3篇
  2016年   4篇
  2015年   2篇
  2014年   2篇
  2013年   5篇
  2012年   3篇
  2011年   6篇
  2009年   5篇
  2008年   2篇
  2007年   3篇
  2006年   4篇
  2005年   3篇
  2004年   3篇
  2003年   9篇
  2002年   2篇
  2001年   3篇
  2000年   2篇
  1999年   23篇
  1998年   262篇
  1997年   139篇
  1996年   86篇
  1995年   40篇
  1994年   37篇
  1993年   58篇
  1992年   9篇
  1991年   16篇
  1990年   10篇
  1989年   13篇
  1988年   11篇
  1987年   20篇
  1986年   13篇
  1985年   14篇
  1982年   2篇
  1981年   11篇
  1980年   4篇
  1978年   4篇
  1977年   26篇
  1976年   40篇
  1975年   5篇
  1974年   2篇
  1968年   2篇
  1960年   2篇
  1959年   2篇
  1958年   1篇
  1954年   1篇
排序方式: 共有942条查询结果,搜索用时 15 毫秒
21.
22.
The concern with nursing research in the future work of nurse graduates. Expectations from the viewpoint of the nurse researcher. Keeping in mind the concerns which occupy nurse researchers now and in the future, expectations are raised of the graduates of degree programmes in nursing science which are now also being established in the Federal Republic of Germany. This takes into account the structurally determined areas of self determined action in new fields of professional practice. Nurse graduates will be seen as "change agents" in their future areas of work and will have three essential aspects of involvement with nursing research: 1. they themselves will conduct research 2. they will receive, put into practice and transmit results of nursing research 3. they will initiate and commission nursing research projects. According to the broad topics of nursing research, requirements for nurses to act as professionals in their new working fields are formulated referring to the given structural conditions in Germany.  相似文献   
23.
Two experiments were conducted to study the effects of methionine supplementation on ruminal fermentation and digesta kinetics. In Exp. 1, nine ruminally cannulated beef heifers (average initial BW = 527 kg) in a crossover design were fed low-quality grass hay and cottonseed meal with or without 11.4 g of supplemental methionine (polysaccharide-coated). Particulate and fluid kinetics, rate of DM and NDF disappearance, ruminal VFA and NH3 N concentrations, and pH were not altered (P > .10) by supplemental methionine; however, ruminal purine concentration was greater (P < .05) in methionine-supplemented heifers than in unsupplemented heifers. In Exp. 2, 12 ruminally cannulated Holstein steers (average initial BW = 622 kg) grazing a fescue pasture were allotted to one of three groups: no supplemental methionine (CON) or 11.4 g of supplemental methionine fed at 0700 (AM) or at 1200 (PM). Forage intake, particulate kinetics, ruminal fluid kinetics, pH, VFA, and NH3 N concentrations were not altered (P > .10) by supplemental methionine or supplementation time. In situ rate of DM and NDF disappearance was greater (P < .05) in supplemented steers than in CON steers; AM steers exhibited faster (P < .05) rates than PM steers. Overall, methionine supplementation of low-quality forage increased ruminal purine concentration but did not alter in situ fermentation or digesta passage, whereas supplementation at 0700, but not at 1200, of steers grazing fescue forage increased rate of NDF fermentation.  相似文献   
24.
The processes of separation and high purification of carbon tetrafluoride and some other freons by distillating and membrane gas separating were considered. The selectivities of impurity and basic components separation in fluorocarbons mixture during of rectification and membrane separation were compared. The published data on the selectivity of different membranes were determined experimentally and compiled. The possibility of obtaining the carbon tetrafluoride with purity level 99.99–99.999 vol % by membrane separating was established.  相似文献   
25.
26.
Russian Journal of Non-Ferrous Metals - Laser cladding, which is characterized by the minimal thermal impact on the substrate, is an advanced technique to restore the working dimensions of parts...  相似文献   
27.
28.
Semiconductors - The spatial and temporal dynamics of the optical loss and carrier density in the heterostructure of a semiconductor laser with a segmented contact are studied using an optical...  相似文献   
29.
Immunocytochemical localization of metabotropic glutamate receptors (mGluRs) and ionotropic glutamate receptors (NMDA-type: NMDAR1 and NMDAR2A-C; AMPA-type: GluR1-4) was performed on sections of rat dorsal horn. Immunoreactivity for mGluR1 alpha was detected in laminae I-III of the dorsal horn, whilst mGluR2/3 immunoreactivity was detected primarily in lamina III. Immunoreactivity for NMDAR1, GluR1, GluR2, GluR2/3, GluR4 and GluR5/6/7 was strongly localized in neuronal elements of laminae I-III. Immunoreactivity for NMDAR2B was localized in laminae I-III. No mGluR5, NMDAR2A and NMDAR2C immunoreactivity was detected. In addition, immunoreactivity for receptors was found to co-localize with immunoreactivity for glutamate in the dorsal horn. The present results indicate that glutamate receptors are differentially localized in neuronal elements of dorsal horn where receptor-neurotransmitter interaction takes place.  相似文献   
30.
In order to investigate radiation risks associated with low dose and low dose-rates, pregnant Swiss albino mice were exposed to gamma rays, 0.80 Gy from a cobalt-60 source at two different dose-rates (0.0795 and 0.0012 Gy/min) on 18 day post conception. In females exposed to lower dose-rate (0.0012 Gy/min), litter size was found to be decreased, while those exposed to higher dose-rate (0.0795 Gy/min), it remained unaltered. In both groups, appearance of fur and development of complete fur were delayed, whereas gait was delayed only in higher dose-rate group. Male offspring exhibited a biphasic mode of weight loss, while female offspring after an initial weight loss at 1 week, displayed a continuous recovery, but could not attain the normal weight till 12 weeks of age. It appears that higher dose-rate is more effective in delaying the appearance of physiological markers and weight loss, while in terms of litter size lower dose-rate (0.0012 Gy/min) is more effective.  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