全文获取类型
收费全文 | 112篇 |
免费 | 5篇 |
国内免费 | 12篇 |
专业分类
化学 | 85篇 |
晶体学 | 1篇 |
力学 | 5篇 |
综合类 | 9篇 |
数学 | 3篇 |
物理学 | 26篇 |
出版年
2023年 | 3篇 |
2022年 | 6篇 |
2021年 | 12篇 |
2020年 | 11篇 |
2019年 | 2篇 |
2018年 | 2篇 |
2017年 | 1篇 |
2016年 | 3篇 |
2015年 | 1篇 |
2014年 | 5篇 |
2013年 | 4篇 |
2012年 | 3篇 |
2011年 | 4篇 |
2010年 | 8篇 |
2009年 | 1篇 |
2008年 | 8篇 |
2007年 | 3篇 |
2006年 | 2篇 |
2005年 | 9篇 |
2004年 | 5篇 |
2003年 | 5篇 |
2002年 | 4篇 |
2001年 | 2篇 |
2000年 | 2篇 |
1999年 | 5篇 |
1998年 | 2篇 |
1997年 | 2篇 |
1996年 | 2篇 |
1995年 | 2篇 |
1994年 | 4篇 |
1993年 | 3篇 |
1992年 | 1篇 |
1987年 | 1篇 |
1982年 | 1篇 |
排序方式: 共有129条查询结果,搜索用时 15 毫秒
1.
基于cDNA宏阵列的系统聚类分析猪发育阶段的基因表达谱 总被引:3,自引:0,他引:3
取杜洛克猪胚胎第33,45,55,65.75天的背最长肌样本.用cDNA Macroarray分析方法和聚类分析技术分析了327个EST在骨骼肌内不同发育阶段的基因表达谱.结果表明有98条EST在不同发育时期显著差异表达.第33天和第45天两阶段基因表达状态相似.第55天和第65天基因表达状态相似.而第75天的基因表达与第55天和第65天两个阶段的基因表达具有相近的聚类关系.表达状态相近,基因功能相似的基因大都被聚类在一起. 相似文献
2.
Conversion reactions of n-butenes over zeolites and amorphous catalysts have been investigated to deduce the factor that determines the selectivity
for the skeletal isomerization producing isobutene. The effects of pore structure and acid site concentration on the selectivity
for the skeletal isomerization are discussed on various catalysts. The pore structures of FER and CLI zeolites induce the
distant locations of butene molecules, accelerating monomolecular skeletal isomerization. On the other hand, acid site concentration
determines the preferred reaction path of n-butenes on amorphous catalysts. Oligomerization followed by cracking that produces various hydrocarbons is suppressed on
the catalyst with low acid site concentration, resulting in high selectivity for isobutene. The feasibility of monomolecular
skeletal isomerization on zeolites and amorphous catalysts is confirmed by its reversibility with high selectivity. 相似文献
3.
4.
SAPO—11分子筛用i—Pr2NH导向合成及其酸性研究 总被引:3,自引:0,他引:3
以AlPO4、H3PO4、SiO2等为原料采用单一模板剂iPr2NH合成了SAPO11分子筛,利用Avrami方程等对合成过程进行了定量描述。还利用红外(IR)、程序升温脱附(TPD)、线性丁烯骨架异构反应催化活性测试等手段表征了SAPO11的酸性。结果表明,合成过程随温度有明显变化,晶化阶段的活化能远高于核化阶段的值。可用Avrami方程的参数来表征合成过程的难易程度。分子筛中存在B酸和L酸位,主要在中等强度范围,从而对线性丁烯骨架异构反应有较好的催化活性。提高分子筛中硅含量可明显增大酸位浓度,酸强度也有轻度增强。 相似文献
5.
6.
J. Orbán Sz. Halasi G. Papp Szilvia Barkó Beáta Bugyi 《Journal of Thermal Analysis and Calorimetry》2005,82(1):287-290
Summary The thermodynamic properties of the cardiac and skeletal a-actin isoforms were studied to characterize the molecular bases
of the functional differences between them with the method of differential scanning calorimetry (DSC). The thermal properties
of the actin filaments were described in the presence of calcium and magnesium ions as well. Based on the calculated free
energy changes the α-cardiac actin filaments appeared to be more stable in its physiologically more relevant, magnesium saturated
form. The magnesium saturated form of the α-cardiac actin filaments seemed to be more stable compared to the calcium saturated
form of it. The enthalpy and entropy changes could differentiate between the α-cardiac and α-skeletal actin isoforms and between
the calcium and magnesium saturated cardiac actin isoforms as well. Our results can demonstrate that the few differences between
the amino acid sequences of the α-actin isoforms have an influence on the thermal properties and maybe on the function of
these proteins as well. 相似文献
7.
Automatic computer programs are developed to calculate one- two-, and three-dimensional Debye functions. Prior tables of these functions are critically reviewed. Also, strategies are derived to calculate Debye temperatures from heat capacities. Both, simple three-dimensional Debye analyses and Tarasov analyses were carried out on 35 linear macromolecules. The experimental heat capacities for these analyses were collected in the ATHAS data bank. It is shown that the skeletal heat capacity of linear macromolecules is often best represented by only two vibrations per chain atom. For most of the all-carbon chain macromolecules the intramolecular skeletal heat capacity can be given by Cvs=D1[520 (28/MW)1/2] whereMW is the molecular mass andD
1 represents the one-dimensional Debye function. Polyoxides show a higher intramolecular theta temperature, but a lower intermolecular theta temperature. Double bonds and phenylene groups in the chain increase the intramolecular theta temperature.Dedicated to Prof. Dr. F. H. Müller.On leave from the Lumumba Peoples' Friendship University, Moscow, USSR. 相似文献
8.
Vera P. Shmachkova Nina S. Kotsarenko Vladislav V. Kanazhevskiy Galina N. Kryukova Dimitri I. Kochubey Jacques Vedrine 《Reaction Kinetics and Catalysis Letters》2007,91(1):177-185
Methods of the preparation of catalysts for alkane skeletal isomerization based on uniform nanoparticles of sulfated zirconia
anchored to different supports were investigated. These catalysts were characterized by using the ICP, HRTEM and BET techniques.
The activities of the catalysts in the reaction of n-butane isomerization were measured and compared with those of bulk catalysts. 相似文献
9.
10.
A. F. Leung 《光谱学快报》2013,46(3):591-600
Laser-induced fluorescence from frog skeletal muscle fibers treated with lanthanides, Eu3+ and Tb3+, was recorded. The fluorescence was weak and overlapped with the Raman scattering by the Ringer solution when the muscle fibers were illuminated with an argon-ion laser. The fluorescence decay rate of the lanthanide in Ringer's solution was 2–3 times larger than that of the lanthanide bound to the muscle fiber. The number of water molecules coordinated to the lanthanide bound to the muscle fiber was determined to be about three. This suggests that lanthanide ions bind superficially to the outer membrane of the muscle fiber. 相似文献