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   213篇
  免费   22篇
  国内免费   33篇
化学   133篇
力学   39篇
综合类   4篇
数学   35篇
物理学   57篇
  2023年   7篇
  2022年   12篇
  2021年   7篇
  2020年   9篇
  2019年   14篇
  2018年   8篇
  2017年   2篇
  2016年   6篇
  2015年   4篇
  2014年   10篇
  2013年   12篇
  2012年   25篇
  2011年   14篇
  2010年   13篇
  2009年   9篇
  2008年   11篇
  2007年   13篇
  2006年   6篇
  2005年   4篇
  2004年   4篇
  2003年   7篇
  2002年   2篇
  2001年   3篇
  2000年   5篇
  1999年   1篇
  1998年   9篇
  1997年   7篇
  1996年   5篇
  1995年   9篇
  1994年   9篇
  1993年   7篇
  1992年   4篇
  1991年   2篇
  1990年   2篇
  1989年   1篇
  1988年   1篇
  1986年   3篇
  1984年   1篇
排序方式: 共有268条查询结果,搜索用时 515 毫秒
51.
A cancer activated protein-inorganic nanoparticle was used as breast cancer cell turn-on fluorescence sensor and NIR activated attenuator.  相似文献   
52.
Huang  Yuwen  Li  Chengju  Wang  Qi  Du  Zongrun 《Designs, Codes and Cryptography》2022,90(1):87-106
Designs, Codes and Cryptography - The (Euclidean) hull of a linear code is defined to be the intersection of the code and its Euclidean dual. It is clear that the hulls are self-orthogonal codes,...  相似文献   
53.
反相流动注射化学发光法测定葡萄糖   总被引:3,自引:0,他引:3  
提出使用葡萄糖增强Luminol-K7Cu(IO6)2-KOH化学发光体系,结合高灵敏度的反相流动注射技术进行葡萄糖的测定。本法不仅节省试剂,而且操作简单,重复性好。葡萄糖在4×10-7~8×10-5mg/L浓度范围内与化学发光分析信号呈线性关系;检出限为1.8X10-7mg/L;RSD=2.04%。  相似文献   
54.
用小角X-射线散射法(SAXS),广角X-射线衍射法(WXAD)和差示扫描量热法(DSC)对由N-催化剂催化聚合的聚丙烯结晶行为进行探讨。发现这种聚丙烯结晶中有β晶型存在,且其含量随结晶时间增加而增加随结晶温度升高而降低;β晶含量增加,聚合物的长周期也会增加,β晶对长周期的影响比α晶更大。乙烯共聚改性后的聚丙烯因分子链规整性下降而阻止了β晶的形成。在熔融状态下结晶时,β晶的形成要求聚丙烯的分子链具有更高的规整性。这些实验结果均从分子链段结晶机理得到了解释。  相似文献   
55.
高锰酸钾与乙酰丙酮快速反应动力学   总被引:2,自引:0,他引:2  
乙酰丙酮CH_2(COCH_3)_2(简写为Hacac)是重要的有机合成中间体,也是柠檬酸在人体内代谢的中间物.为了进一步掌握柠檬酸氧化的后续变化,我组观测了前人未曾报导过的乙酰丙酮与高锰酸钾在酸性介质中的快速反应.该反应从现象上可明显分为两个阶段:第一个阶段是MnO_4~-的紫色迅速消褪,反应体系转变为浅绿色溶液;第二阶段是浅绿溶液缓慢转变为无色.其中第一阶段的反应速率相当快.我组曾研制成功CFF-751G 型连续流动法快速反应装置,本工作采用该装置对上述第一阶段的快速反应进行了动力学研究.  相似文献   
56.
57.
We investigate the metric generalized inverses of linear operators in Banach spaces and their homogeneous selections, which was the research suggestion given by Nashed and Votruba (Bull. Am. Math. Soc. 80:831–835, 1974). We construct a kind of the bounded homoneneous selections for the set-valued metric generalized inverse. Criteria for the metric generalized inverses of linear operators and their homogeneous selections are given in terms of Moore–Penrose conditions. The research was supported in part by the National Science Foundation Grant (10671049) and the Science Foundation Grant of Heilongjiang Province.  相似文献   
58.
Gao  Yu  Huang  Jun  Liu  Yuwen  Yan  Jawei  Mao  Bingwei  Chen  Shengli 《中国科学:化学(英文版)》2019,62(4):515-520
We present a conceptual framework for understanding and formulating ion transport in concentrated solutions, which pictures the ion transport as an ion-vacancy coupled charge transfer reaction. A key element in this picture is that the transport of an ion from an occupied to unoccupied site involves a transition state which exerts double volume exclusion. An ab initio random walk model is proposed to describe this process. Subsequent coarse-graining results in a continuum formula as a function of chemical potentials of the constituents, which are further derived from a lattice-gas model. The subtlety here is that what has been taken to be the chemical potential of the ion in the past is actually that of the ion-vacancy couple. By aid of this new concept, the driving force of ion transport is essentially the chemical affinity of the ion-vacancy coupled charge transfer reaction, which is a useful concept to unify transport and reaction, two fundamental processes in electrochemistry. This phenomenological model is parameterized for a specific material by the aid of first-principles calculations. Moreover, its extension to multiple-component systems is discussed.  相似文献   
59.
In the work reported herein, the electrocatalytic properties of Co3O4 in hydrogen and oxygen evolution reactions have been significantly enhanced by coating a shell layer of a copper-based metal–organic framework on Co3O4 porous nanowire arrays and using the products as high-performance bifunctional electrocatalysts for overall water splitting. The coating of the copper-based metal–organic framework resulted in the hybridization of the copper-embedded protective carbon shell layer with Co3O4 to create a strong Cu−O−Co bonding interaction for efficient hydrogen adsorption. The hybridization also led to electronically induced oxygen defects and nitrogen doping to effectively enhance the electrical conductivity of Co3O4. The optimal as-prepared core–shell hybrid material displayed excellent overall-water-splitting catalytic activity that required overall voltages of 1.45 and 1.57 V to reach onset and a current density of 10 mA cm−2, respectively. This is the first report to highlight the relevance of hybridizing MOF-based co-catalysts to boost the electrocatalytic performance of nonprecious transition-metal oxides.  相似文献   
60.
An Ambrosetti-Prodi type exact multiplicity result is proved for a diffusive logistic equation with harvesting. We show that a modified diffusive logistic mapping has exactly either zero, or one, or two pre-images depending on the harvesting rate. It implies that the original diffusive logistic equation with harvesting has at most two positive steady state solutions.  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