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   505篇
  免费   7篇
  国内免费   6篇
化学   382篇
晶体学   4篇
力学   10篇
数学   84篇
物理学   38篇
  2023年   4篇
  2022年   7篇
  2021年   10篇
  2020年   9篇
  2019年   6篇
  2018年   4篇
  2017年   3篇
  2016年   13篇
  2015年   9篇
  2014年   9篇
  2013年   32篇
  2012年   28篇
  2011年   33篇
  2010年   22篇
  2009年   9篇
  2008年   27篇
  2007年   36篇
  2006年   22篇
  2005年   45篇
  2004年   36篇
  2003年   22篇
  2002年   12篇
  2001年   6篇
  2000年   8篇
  1999年   11篇
  1998年   4篇
  1997年   6篇
  1996年   8篇
  1995年   4篇
  1994年   5篇
  1993年   4篇
  1992年   2篇
  1990年   2篇
  1989年   3篇
  1988年   4篇
  1987年   3篇
  1986年   4篇
  1985年   5篇
  1984年   4篇
  1982年   5篇
  1980年   11篇
  1979年   1篇
  1978年   3篇
  1977年   2篇
  1976年   3篇
  1974年   2篇
  1973年   2篇
  1972年   1篇
  1968年   3篇
  1967年   1篇
排序方式: 共有518条查询结果,搜索用时 0 毫秒
71.
In this paper we explore two teachers' views on the role(s) of parents, the local community and children's home lives in the learning of mathematics in primary school. We use Moll and Greenberg's concept of ‘funds of knowledge’ and apply it to the case studies of two teachers working in the UK context. Issues of teachers' professional experience, ethnicity, class and gender emerge as significant in examining similarities and differences in the teachers' beliefs, understandings and practices in the area of linking home and school. We end with a discussion of some implications for teacher education and professional development.  相似文献   
72.
A Blaschke product B with zero-sequence (an) is called almostinterpolating if the inequality lim infn(1 – |an|2)|B'(an)|  相似文献   
73.
74.
Preliminary results of a Mn-promoted sequential process directed toward the stereoselective synthesis of different (Z)-alpha-halo-alpha,beta-unsaturated compounds are described.  相似文献   
75.
The use of a boronic ester as a captor of aqueous [(18)F]-fluoride has been previously suggested as a means of labeling biomolecules in one step for positron emission tomography (PET) imaging. For this approach to be seriously considered, the [(18)F]-labeled trifluoroborate should be humorally stable such that it neither leaches free [(18)F]-fluoride to the bone nor accumulates therein. Herein, we have synthesized a biotinylated boronic ester that is converted to the corresponding trifluoroborate salt in the presence of aqueous [(18)F]-fluoride. In keeping with its in vitro aqueous kinetic stability at pH 7.5, the trifluoroborate appears to clear in vivo quite rapidly to the bladder as the stable trifluoroborate salt with no detectable leaching of free [(18)F]-fluoride to the bone. When this labeled biotin is preincubated with avidin, the pharmacokinetic clearance of the resulting complex is visibly altered. This work validates initial claims that boronic esters are potentially useful as readily labeled precursors to [(18)F]-PET reagents.  相似文献   
76.
77.
78.
Zinc is an essential mineral which plays a key role in several important biological processes in the human body. The determination of its level in food matrices can contribute to the food quality characterization and to the adequacy of the diet. Animal food products generally have a higher zinc content compared to vegetables. Among them, dairy products consumption can provide a great contribution to the zinc reference intakes. In this study, different Italian cheeses (38 Protected Denomination of Origin and 9 Traditional) were evaluated for their zinc content. Cow cheeses generally showed the highest zinc content (1.83–7.75 mg/100 g cheese), followed by sheep cheeses (1.34–3.69 mg/100 g), and cheeses from mixed milk (0.39–4.54 mg/100 g). The only cheese from buffalo milk (Mozzarella di Bufala Campana PDO) showed a zinc content of 2.14 mg/100 g. The great variability in the zinc content observed among the samples is the result of the influence of several factors, such as the feeding system, the species (cow, sheep, goat, and buffalo), and the cheese-making. Most of the samples resulted in a great contribution (>10%) to the zinc Daily Reference Intake set by EU (10 mg/day), with only two samples contributing to less than 4%.  相似文献   
79.
80.
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