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   4872篇
  免费   19篇
  国内免费   1篇
电工技术   14篇
化学工业   47篇
金属工艺   10篇
机械仪表   10篇
建筑科学   15篇
矿业工程   4篇
能源动力   4篇
轻工业   39篇
水利工程   3篇
石油天然气   2篇
无线电   22篇
一般工业技术   69篇
冶金工业   4599篇
原子能技术   11篇
自动化技术   43篇
  2019年   3篇
  2018年   6篇
  2017年   3篇
  2016年   9篇
  2015年   7篇
  2014年   8篇
  2013年   22篇
  2012年   10篇
  2011年   19篇
  2010年   6篇
  2009年   13篇
  2008年   8篇
  2007年   13篇
  2006年   10篇
  2005年   12篇
  2004年   8篇
  2003年   9篇
  2002年   15篇
  2001年   7篇
  2000年   8篇
  1999年   160篇
  1998年   1391篇
  1997年   757篇
  1996年   515篇
  1995年   271篇
  1994年   242篇
  1993年   260篇
  1992年   37篇
  1991年   78篇
  1990年   66篇
  1989年   94篇
  1988年   79篇
  1987年   68篇
  1986年   71篇
  1985年   58篇
  1984年   5篇
  1983年   7篇
  1982年   18篇
  1981年   34篇
  1980年   52篇
  1979年   3篇
  1978年   14篇
  1977年   122篇
  1976年   273篇
  1975年   9篇
  1971年   2篇
  1968年   2篇
  1955年   3篇
  1944年   1篇
  1925年   1篇
排序方式: 共有4892条查询结果,搜索用时 15 毫秒
51.
52.
53.
54.
55.
56.
We describe three case reports of hematomas in the abdominal wall muscles and discuss etiology, diagnostic findings and treatment. Abdominal wall hematomas are uncommon, and the condition is often misdiagnosed. One of our patients was laparotomised owing to suspected appendicitis, and one patient presented a tuberculous abscess that may have been an infected hematoma. Ultrasonographic examination or CT gives the correct diagnose. Conservative management is the treatment of choice unless bleeding is severe or the course is complicated by infection.  相似文献   
57.
58.
Retinoids have important roles in pattern formation during embryonic development and might act as endogenous morphogens. They are necessary for normal odontogenesis and excess retinol alters the pattern of odontogenesis producing supernumerary buds of the dental lamina in the diastema region of the mouse mandible. Because the metabolism of retinoids in the developing mandible is unknown, the effects of retinal (an intermediate metabolite in the local conversion of retinol to retinoic acid) on the patterning of odontogenesis were examined. Retinal produces supernumerary buds and enhanced epithelial proliferation in day-9 mandibles in vitro. The endogenous levels of retinal in the mandible at the time of initiation of odontogenesis were also measured by high-performance liquid chromatography. Retinal was detected only at day 10 and not at later stages of development. Local metabolism of this intermediate retinoid may be a rate-determining step in the production of active retinoid metabolites that may control the pattern of the dentition, which is established at the time of the appearance of the dental lamina at embryonic day 12.  相似文献   
59.
Isolated rat liver mitochondria were incubated under various metabolic conditions to determine their membrane potential (MMP) as measured continuously by a tetraphenylphosphonium (TPP+)-selective electrode. By flow cytometry, a parallel analysis of fluorescence emissions observing single mitochondria stained with the lipophilic cation 5,5',6,6'-tetrachloro-1,1'3,3'-tetraethylbenzimidazolcarbocyanine iodide (JC-1) revealed linear correlation between the median orange fluorescence (FL2) due to J-aggregate formations and MMP values measured by TPP+. No correlation was detected with the green fluorescence (FL1) emission. A significantly higher correlation appeared between the FL2/FL1 ratio and MMP values. Within the same mitochondrial population, cytofluorimetric analysis revealed the presence of various classes of organelles with different MMP, whose distribution was dependent on metabolic condition. The highest functional heterogeneity was found in deenergized mitochondria, while the highest homogeneity was observed during the first phase of the phosphorylative process. Thus, these data suggest that the cytofluorimetric use of JC-1 provides direct experimental evidence for the hypothesis of functional mitochondrial heterogeneity, at least with respect to their membrane potential.  相似文献   
60.
We studied 17 pedigrees with 108 affected males with X-linked juvenile retinoschisis (RS; McKusick No. 31270) and have analyzed all of the known polymorphic markers in the RS region of Xp22.1-p22.2 between DXS987 and DXS41. By haplotype analyses we found 7 individuals who showed crossovers in this interval surrounding RS. We previously reported AFM291wf5 as the centromeric boundary, and this remains unchanged in the present study. A new recombination was identified on the telomeric side at (DXS1195, DXS418). Our data support the locus order Xpter--(DXS987, DXS207, DXS1053, DXS43)--(DXS1195, DXS418)--(RS, DXS257, DXS999)--(AFM291wf5, DXS443)--DXS1052--(DXS1226, DXS274, DXS41)--Xcen; loci grouped in parentheses could not be mutually ordered by our genetic data. Physical mapping has indicated a distance of at most 900-1,000 kb between (DXS1195, DXS418) and AFM291wf5. No recombination was observed between RS and DXS257 which lies in our new interval of interest, but one critical individual was not informative with this marker. Our data now define the smallest RS inclusion interval. This interval is contained on a single YAC from which we have identified expressed sequences as candidate genes for RS.  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