全文获取类型
收费全文 | 266篇 |
免费 | 16篇 |
国内免费 | 2篇 |
专业分类
化学 | 176篇 |
力学 | 2篇 |
数学 | 59篇 |
物理学 | 47篇 |
出版年
2023年 | 4篇 |
2022年 | 7篇 |
2021年 | 6篇 |
2020年 | 4篇 |
2019年 | 2篇 |
2018年 | 4篇 |
2017年 | 4篇 |
2016年 | 9篇 |
2015年 | 13篇 |
2014年 | 11篇 |
2013年 | 20篇 |
2012年 | 16篇 |
2011年 | 21篇 |
2010年 | 10篇 |
2009年 | 21篇 |
2008年 | 24篇 |
2007年 | 16篇 |
2006年 | 16篇 |
2005年 | 13篇 |
2004年 | 15篇 |
2003年 | 10篇 |
2002年 | 13篇 |
2001年 | 1篇 |
2000年 | 1篇 |
1999年 | 3篇 |
1998年 | 2篇 |
1997年 | 2篇 |
1996年 | 3篇 |
1994年 | 3篇 |
1993年 | 2篇 |
1983年 | 3篇 |
1973年 | 1篇 |
1969年 | 1篇 |
1961年 | 1篇 |
1960年 | 1篇 |
1956年 | 1篇 |
排序方式: 共有284条查询结果,搜索用时 15 毫秒
1.
Interactions of Pt‐ttpy with G‐Quadruplexes Originating from Promoter Region of the c‐myc Gene Deciphered by NMR and Gel Electrophoresis Analysis 下载免费PDF全文
2.
In this paper we discuss some instances where dense matrix techniques can be utilized within a sparse simplex linear programming solver. The main emphasis is on the use of the Schur complement matrix as a part of the basis matrix representation. This approach enables to represent the basis matrix as an easily invertible sparse matrix and one or more dense Schur complement matrices. We describe our variant of this method which uses updating of the QR factorization of the Schur complement matrix. We also discuss some implementation issues of the LP software package which is based on this approach. 相似文献
3.
The performance of new FTIR-based monitoring technology to representatively determine reaction kinetics has been demonstrated on an example of homogeneously catalyzed liquid-phase sucrose hydrolysis to fructose and glucose. The reaction kinetics were investigated by using the ReactIR 1000 reaction analysis system, which enables determination of the component concentration from its characteristic FTIR spectrum. During the sucrose inversion, the ReactIR 1000 instrument connected to a computer controlled standard glass batch reactor provided the required operating conditions and information about the component concentration in real-time. We have studied the influence of hydrogen ion concentration, temperature and initial concentration of sucrose on the sucrose disappearance rate. It was found out that the inversion of sucrose is an irreversible reaction, which is not affected by the formation of fructose and glucose in the liquid-phase. Then, the parameters of the kinetic model (i.e., reaction rate constant and activation energy) were calculated. A comparison of the model output and the measured data showed that the kinetics of the sucrose inversion could be well described by means of the pseudo first-order kinetic model. Finally, the method of determining the kinetic model by FTIR spectroscopy was verified by comparing the results obtained in the batch reactor with the results obtained in the continuously stirred tank reactor. 相似文献
4.
Single crystals of α-Ca3UO6 were grown from a UO3CaCl2CaO melt by the slow cooling method from 950°C. The crystal structure was determined by means of X-ray diffraction with R = 0.032 and Rw = 0.019. The structure of α-Ca3UO6 is of Mg3TeO6 type. α-Ca3UO6 is rhombohedral with a = 6.729 (1)Å, α = 90.30 (1)°, Z = 2, Dc = 4.955 g/cm3, Dm = 4.79 g/cm3, space group . Uranium and calcium atoms are six-coordinated. At 1200°C rhombohedral α-Ca3UO6 irreversibly transforms to monoclinic β-Ca3UO6. 相似文献
5.
Stopar D Strancar J Spruijt RB Hemminga MA 《Journal of chemical information and modeling》2005,45(6):1621-1627
Molecular modeling based on a hybrid evolutionary optimization and an information condensation algorithm, called GHOST, of spin label ESR spectra was applied to study the structure and dynamics of membrane proteins. The new method is capable of providing detailed molecular information about the conformational space of the spin-labeled segment of the protein in a membrane system. The method is applied to spin-labeled bacteriophage M13 major coat protein, which is used as a model membrane protein. Single cysteine mutants of the coat protein were labeled with nitroxide spin labels and incorporated in 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) bilayers. The new computational method allows us to monitor distributions of local spatial constraints and molecular mobility, in addition to information about the location of the protein in a membrane. Furthermore, the results suggest that different local conformations may coexist in the membrane protein. The knowledge of different local conformations may help us to better understand the function-structure relationship of membrane proteins. 相似文献
6.
Rappolt M Amenitsch H Strancar J Teixeira CV Kriechbaum M Pabst G Majerowicz M Laggner P 《Advances in colloid and interface science》2004,111(1-2):63-77
In this work, we report on recent investigations, both on the global and on the local molecular architecture of supported phospholipid model membranes. A brief theoretical introduction explains how global structural information on supramolecular lipid ensembles can be retrieved from surface X-ray diffraction measurements as well as how spin-label electron paramagnetic resonance spectroscopy (EPR) provides complementary information on the local environment of probe molecules. The combination of especially designed X-ray cells with the technique of small- and wide-angle X-ray surface scattering makes it possible to explore various fields of lipid research and its applications. Examples for different physico-chemical conditions are presented: (i) in situ chemistry under excess of water conditions demonstrating how solid-supported lipid films sense salinity, (ii) the 3D electron density reconstruction of a vesicle-fusion intermediate under controlled humidity, and (iii) complementary temperature and pressure effects on oriented phospholipid samples. Further, special attention has been given to the influence of different film preparation techniques with respect to quality and the defect structure manifestation. To resolve the proportions and local properties of defects in a hydrated lipid-deposited surface, spin-label EPR was applied. The results from 9.6 GHz EPR as well as from 1.2 GHz EPR suggest the alignment to be in the range between 30% and 80%. In addition, slow time-dependent EPR measurements point to nano-structural rearrangements due to water flow and reduction of alignment quality. 相似文献
7.
Antonín Klsek Jirí Polis Vladimír Mrkvi
ka Janez Komrlj 《Journal of heterocyclic chemistry》2002,39(6):1315-1320
4‐Hydroxy‐1H‐quinolin‐2‐ones ( 1 ) react with thiocyanogen in acetic acid to the corresponding 3‐thiocyanato‐1H,3H‐quinoline‐2,4‐diones ( 2 ) in good yields. In some cases, 3‐bromo‐1H,3H‐quinoline‐2,4‐diones ( 4 ) were isolated as minor reaction products. Compounds 2 are very reactive towards nucleophiles and easily hydrolyze to the corresponding 4‐hydroxy‐1H‐quinoline‐2‐ones ( 1 ). 相似文献
8.
Ozonation of norcarane (1) yielded endo and exo norcarane hydrotrioxides (2a, 2b), as characterized by (1)H and (13)C NMR spectroscopy. Further ozonation of the primary decomposition products of these hydrotrioxides, i.e., 2-norcaranols (3), produced the corresponding isomeric 2-norcaranol hydrotrioxides (4a, 4b), and hydrogen trioxide (HOOOH). 相似文献
9.
10.
David Pahovnik Milijana Grujić Mateja Cegnar Janez Kerč Ema Žagar 《Journal of polymer science. Part A, Polymer chemistry》2014,52(20):2976-2985
The negatively charged, water‐soluble, hydrophobically modified poly(sodium glutamate)s containing different amounts of alkyl grafts were synthesized. First, poly(γ‐benzyl‐L‐glutamate) was prepared by ring‐opening polymerization of the corresponding N‐carboxyanhydride, which was in the next step aminolysed with octylamine. After removal of the remaining benzyl protective groups, the alkyl‐modified poly(sodium glutamate)s [P(Glu‐oa)] were obtained and, together with the oppositely charged N,N,N‐trimethyl chitosan (TMC), used for the preparation of nanoparticles (NPs) of a recombinant granulocyte colony‐stimulating factor (GCSF) protein by polyelectrolyte complexation method. It is observed that, beside electrostatic interaction, the hydrophobic grafts on poly(sodium glutamate)s significantly contribute to association efficiency (AE) with GCSF protein. The addition of TMC solution to the dispersion of GCSF/P(Glu‐oa) complexes results in formation of much more defined NPs with high AE and final protein loading. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 2976–2985 相似文献