全文获取类型
收费全文 | 153篇 |
免费 | 29篇 |
国内免费 | 37篇 |
专业分类
化学 | 128篇 |
晶体学 | 2篇 |
力学 | 4篇 |
综合类 | 12篇 |
数学 | 13篇 |
物理学 | 60篇 |
出版年
2022年 | 2篇 |
2021年 | 2篇 |
2020年 | 3篇 |
2019年 | 2篇 |
2018年 | 5篇 |
2017年 | 10篇 |
2016年 | 2篇 |
2015年 | 5篇 |
2014年 | 9篇 |
2013年 | 9篇 |
2012年 | 7篇 |
2011年 | 4篇 |
2010年 | 8篇 |
2009年 | 11篇 |
2008年 | 10篇 |
2007年 | 9篇 |
2006年 | 10篇 |
2005年 | 9篇 |
2004年 | 9篇 |
2003年 | 3篇 |
2002年 | 3篇 |
2001年 | 6篇 |
2000年 | 15篇 |
1999年 | 7篇 |
1997年 | 1篇 |
1996年 | 2篇 |
1995年 | 2篇 |
1994年 | 2篇 |
1993年 | 3篇 |
1992年 | 2篇 |
1991年 | 4篇 |
1990年 | 3篇 |
1987年 | 1篇 |
1984年 | 2篇 |
1982年 | 1篇 |
1980年 | 3篇 |
1969年 | 3篇 |
1939年 | 2篇 |
1937年 | 1篇 |
1935年 | 1篇 |
1934年 | 6篇 |
1933年 | 5篇 |
1932年 | 3篇 |
1931年 | 4篇 |
1930年 | 2篇 |
1929年 | 2篇 |
1913年 | 1篇 |
1910年 | 3篇 |
排序方式: 共有219条查询结果,搜索用时 398 毫秒
1.
基于MATLAB的异步电动机线性化控制系统的仿真 总被引:1,自引:0,他引:1
从异步电动机在同步旋转坐标系下的状态方程出发,在一定的条件下,对其系数矩阵简化.推出异步电动机的线性化控制模型.并基于该模型得出异步电动机的线性化控制系统.以给定电机为例,对该模型的有效性、响应用MATLAB进行仿真分析.验证的结果说明上述模型具有实用价值. 相似文献
2.
CHEN Zhi-hong XU Li BA Xue-qing ZENG Xian-lu 《高等学校化学研究》2006,22(3):302-307
Introduction Migrationandrecruitmentofleukocytesfromblood toinflammatorylesionsitesaresequentiallyregulated byadhesionmoleculesandtheirreceptors[1].These lectinfamilyplaysamajorroleininitiatingattachement ofneutrophilstotheactivatedendothelium.P selectin,… 相似文献
3.
4.
5.
Optical sensor systems for bioprocess monitoring 总被引:3,自引:0,他引:3
Bioreactors are closed systems in which microorganisms can be cultivated under defined, controllable conditions that can be optimized with regard to viability, reproducibility, and product-oriented productivity. To drive the biochemical reaction network of the biological system through the desired reaction optimally, the complex interactions of the overall system must be understood and controlled. Optical sensors which encompass all analytical methods based on interactions of light with matter are efficient tools to obtain this information. Optical sensors generally offer the advantages of noninvasive, nondestructive, continuous, and simultaneous multianalyte monitoring. However, at this time, no general optical detection system has been developed. Since modern bioprocesses are extremely complex and differ from process to process (e.g., fungal antibiotic production versus mammalian cell cultivation), appropriate analytical systems must be set up from different basic modules, designed to meet the special demands of each particular process. In this minireview, some new applications in bioprocess monitoring of the following optical sensing principles will be discussed: UV spectroscopy, IR spectroscopy, Raman spectroscopy, fluorescence spectroscopy, pulsed terahertz spectroscopy (PTS), optical biosensors, in situ microscope, surface plasmon resonance (SPR), and reflectometric interference spectroscopy (RIF). 相似文献
6.
Helga Wittmann P. Beutel E. Ziegler 《Monatshefte für Chemie / Chemical Monthly》1969,100(5):1619-1623
Zusammenfassung Es wird gezeigt, daß Thetin, Pyridin-und Nicotinsäurebetain Phenole am O methylieren. Bei dieser Reaktion bildet sich primär aus dem Betain durch Verlust von CO2 das entsprechende Ylid, welches mit dem jeweiligen Phenol zu einem Phenolatkomplex zusammentritt, der dann thermisch in den Phenoläther und die tert. Base Zerfällt.
Auszugsweise vorgetragen anläßlich der Chemikertagung in Wien, September 1968. 相似文献
Reactions with betaine, IV: On thetine, (1-pyridinio)acetate, and the betaine of nicotinic acid
Thetine, (1-pyridinio)acetate, and nicotinic acid betaine react with phenolic compounds to give their methyl ethers. The reaction proceeds via the corresponding ylides, formed by betaine decarboxylation. The ylides combine with the phenols yielding a phenolate complex, which is decomposed upon heating to give the phenol ether and the tert. base.
Auszugsweise vorgetragen anläßlich der Chemikertagung in Wien, September 1968. 相似文献
7.
应用原子吸收光谱法测定了内蒙古地产的笃斯茎、叶中的Cu,Fe,Zn,Mn,Ca,Mg等六种人体必需微量元素及宏量元素的含量。从而为评价笃斯的品质及其药理、药效提供了具有一定价值的数据。 相似文献
8.
采用普通溶液法合成了配合物[Zn(eiqnthz)_2]·DMF(1)和[Zn3(piqnthz)_2Cl_2]·2H_2O(2)(Heiqnthz=N,N′-乙酰异喹啉甲酰肼,H2piqnthz=N,N′-丙酰异喹啉甲酰肼)。通过X射线单晶衍射分析、X射线粉末衍射分析、红外光谱分析、热重分析以及荧光光谱分析等分析方法对2个配合物进行结构测定和性质表征。结构分析表明配合物1是单核结构,单斜晶系,空间群为C2/c,锌离子周围有4个氮原子和2个氧原子与之配位,形成一个畸变的N4O2八面体构型。配合物2属于单斜晶系,C2/c空间群,三核结构。中心原子Zn(1)、Zn(2)、Zn(3)均为5配位,Zn(1)、Zn(3)位于分子两端并且是变形四角锥配位构型,Zn(2)位于中间形成三角双锥配位构型,整体呈V字型。荧光分析表明Heiqnthz、H2piqnthz与锌(Ⅱ)离子配位后其荧光都发生较大的红移。 相似文献
9.
Enzymatic Conversion of Flavonoids using Bacterial Chalcone Isomerase and Enoate Reductase 下载免费PDF全文
Dipl.‐Biol. Mechthild Gall Dipl.‐Biochem. Maren Thomsen Dipl.‐Biochem. Christin Peters Dr. Ioannis V. Pavlidis M. Sc. Patrick Jonczyk M. Sc. Philipp P. Grünert Dr. Sascha Beutel Prof. Dr. Thomas Scheper Egon Gross Dr. Michael Backes Dr. Torsten Geißler Dr. Jakob P. Ley Dr. Jens‐Michael Hilmer Dr. Gerhard Krammer Dr. Gottfried J. Palm Prof. Dr. Winfried Hinrichs Prof. Dr. Uwe T. Bornscheuer 《Angewandte Chemie (International ed. in English)》2014,53(5):1439-1442
Flavonoids are a large group of plant secondary metabolites with a variety of biological properties and are therefore of interest to many scientists, as they can lead to industrially interesting intermediates. The anaerobic gut bacterium Eubacterium ramulus can catabolize flavonoids, but until now, the pathway has not been experimentally confirmed. In the present work, a chalcone isomerase (CHI) and an enoate reductase (ERED) could be identified through whole genome sequencing and gene motif search. These two enzymes were successfully cloned and expressed in Escherichia coli in their active form, even under aerobic conditions. The catabolic pathway of E. ramulus was confirmed by biotransformations of flavanones into dihydrochalcones. The engineered E. coli strain that expresses both enzymes was used for the conversion of several flavanones, underlining the applicability of this biocatalytic cascade reaction. 相似文献
10.
Dr. Ivan Fernandez-Corbaton Dominik Beutel Prof. Dr. Carsten Rockstuhl Ansgar Pausch Prof. Dr. Wim Klopper 《Chemphyschem》2020,21(9):878-887
We outline a methodology for efficiently computing the electromagnetic response of molecular ensembles. The methodology is based on the link that we establish between quantum-chemical simulations and the transfer matrix (T-matrix) approach, a common tool in physics and engineering. We exemplify and analyze the accuracy of the methodology by using the time-dependent Hartree-Fock theory simulation data of a single chiral molecule to compute the T-matrix of a cross-like arrangement of four copies of the molecule, and then computing the circular dichroism of the cross. The results are in very good agreement with full quantum-mechanical calculations on the cross. Importantly, the choice of computing circular dichroism is arbitrary: Any kind of electromagnetic response of an object can be computed from its T-matrix. We also show, by means of another example, how the methodology can be used to predict experimental measurements on a molecular material of macroscopic dimensions. This is possible because, once the T-matrices of the individual components of an ensemble are known, the electromagnetic response of the ensemble can be efficiently computed. This holds for arbitrary arrangements of a large number of molecules, as well as for periodic or aperiodic molecular arrays. We identify areas of research for further improving the accuracy of the method, as well as new fundamental and technological research avenues based on the use of the T-matrices of molecules and molecular ensembles for quantifying their degrees of symmetry breaking. We provide T-matrix-based formulas for computing traditional chiro-optical properties like (oriented) circular dichroism, and also for quantifying electromagnetic duality and electromagnetic chirality. The formulas are valid for light-matter interactions of arbitrarily-high multipolar orders. 相似文献