全文获取类型
收费全文 | 432篇 |
免费 | 11篇 |
专业分类
化学 | 294篇 |
晶体学 | 2篇 |
力学 | 8篇 |
数学 | 28篇 |
物理学 | 111篇 |
出版年
2021年 | 3篇 |
2019年 | 4篇 |
2017年 | 3篇 |
2016年 | 6篇 |
2015年 | 9篇 |
2014年 | 11篇 |
2013年 | 27篇 |
2012年 | 26篇 |
2011年 | 41篇 |
2010年 | 10篇 |
2009年 | 18篇 |
2008年 | 20篇 |
2007年 | 42篇 |
2006年 | 35篇 |
2005年 | 23篇 |
2004年 | 20篇 |
2003年 | 19篇 |
2002年 | 8篇 |
2001年 | 2篇 |
2000年 | 2篇 |
1999年 | 2篇 |
1998年 | 3篇 |
1997年 | 3篇 |
1996年 | 4篇 |
1995年 | 12篇 |
1994年 | 5篇 |
1993年 | 8篇 |
1992年 | 3篇 |
1991年 | 6篇 |
1990年 | 6篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 4篇 |
1985年 | 6篇 |
1984年 | 5篇 |
1983年 | 7篇 |
1982年 | 5篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1977年 | 5篇 |
1972年 | 1篇 |
1971年 | 2篇 |
1970年 | 1篇 |
1967年 | 1篇 |
1959年 | 1篇 |
1955年 | 1篇 |
1937年 | 1篇 |
排序方式: 共有443条查询结果,搜索用时 31 毫秒
1.
The paper presents an analytical study of blood flow through a stenosed artery using a suitable mathematical model. The artery is modelled as an anisotropic viscoelastic cylindrical tube containing a non-Newtonian viscous incompressible fluid representing blood. The blood flow is assumed to be characterized by the Herschel–Bulkley model. The effect of the surrounding connective tissues on the motion of the arterial wall has been incorporated. Initially, the relevant solutions of the boundary value problem are obtained in the Laplace transform space, through the use of a suitable finite difference technique. Laplace inversion is carried out by employing suitable numerical techniques. Finally, the variations of the vascular wall displacements, the velocity distribution of the blood flow, the flux, the resistance to flow and the wall shear stress in the stenotic region are quantified through numerical computations and presented graphically. 相似文献
2.
Dipak Ghosh Madhumita Lahiri Argha Deb Susobhan Das Krishnadas Purkait Biswanath Biswas Jayanta Roy Choudhury Rini Chatterjee Abdul Kayum Jafry 《Zeitschrift fur Physik C Particles and Fields》1996,71(1):243-249
The scaled factorial moments and the multifractal moments have been investigated in differentη-intervals to study the dynamical fluctuation of pions produced in 200 AGeV32S-Ag/Br interaction. In order to investigate the detail characteristics of intermittency behaviour, theF-moments are extracted up to the eighth order of moments in differentM-intervals. The analysis indicates a non-thermal phase transition and different regime of particle production during the hadronisation process. 相似文献
3.
4.
5.
6.
7.
8.
Dhar S Senapati D Das PK Chattopadhyay P Nethaji M Chakravarty AR 《Journal of the American Chemical Society》2003,125(40):12118-12124
A new class of ternary copper(II) complexes of formulation [Cu(L(n)B](ClO(4)) (1-4), where HL(n) is a NSO-donor Schiff base (HL(1), HL(2)) and B is a NN-donor heterocyclic base viz. 1,10-phenanthroline (phen) and 2,9-dimethyl-1,10-phenanthroline (dmp), are prepared, structurally characterized, and their DNA binding and photocleavage activities studied in the presence of red light. Ternary complex [Cu(L(3))(phen)](ClO(4)) (5) containing an ONO-donor Schiff base and a binary complex [Cu(L(2))(2)] (6) are also prepared and structurally characterized for mechanistic investigations of the DNA cleavage reactions. While 1-4 have a square pyramidal (4 + 1) CuN(3)OS coordination geometry with the Schiff base bonded at the equatorial sites, 5 has a square pyramidal (4 + 1) geometry with CuN(3)O(2) coordination with the alcoholic oxygen at the axial site, and 6 has a square planar trans-CuN(2)O(2) geometry. Binding of the complexes 1-4 to calf thymus DNA shows the relative order: phen > dmp. Mechanistic investigations using distamycin reveal minor groove binding for the complexes. The phen complexes containing the Schiff base with a thiomethyl or thiophenyl moiety show red light induced photocleavage. The dmp complexes are essentially photonuclease inactive. Complexes 5 and 6 are cleavage inactive under similar photolytic conditions. A 10 microM solution of 1 displays a 72% cleavage of SC DNA (0.5 microg) on an exposure of 30 min using a 603 nm Nd:YAG pulsed laser (60 mJ/P) in Tris-HCl buffer (pH 7.2). Significant cleavage of 1 is also observed at 694 nm using a Ruby laser. Complex 1 is cleavage inactive under argon or nitrogen atmosphere. It shows a more enhanced cleavage in pure oxygen than in air. Enhancement of cleavage in D(2)O and inhibition with sodium azide addition indicate the possibility of the formation of singlet oxygen as a reactive intermediate leading to DNA cleavage. The d-d band excitation with red light shows significant enhancement of cleavage yield. The results indicate that the phen ligand is necessary for DNA binding of the complex. Both the sulfur-to-copper charge transfer band and copper d-d band excitations helped the DNA cleavage. While the absorption of a red photon induces a metal d-d transition, excitation at shorter visible wavelengths leads to the sulfur-to-copper charge transfer band excitation at the initial step of photocleavage. The excitation energy is subsequently transferred to ground state oxygen molecules to produce singlet oxygen that cleaves the DNA. 相似文献
9.
Koushik Dhara Santanu Karan Jagnyeswar Ratha Partha Roy Goutam Chandra Mario Manassero Dr. Biswanath Mallik Dr. Pradyot Banerjee Dr. 《化学:亚洲杂志》2007,2(9):1091-1100
A 2D coordination compound {[Cu2(HL)(N3)]?ClO4}∞ ( 1 ; H3L=2,6‐bis(hydroxyethyliminoethyl)‐4‐methyl phenol) was synthesized and characterized by single‐crystal X‐ray diffraction to be a polymer in the crystalline state. Each [Cu2(HL)(N3)]+ species is connected to its adjacent unit by a bridging alkoxide oxygen atom of the ligand to form a helical propagation along the crystallographic a axis. The adjacent helical frameworks are connected by a ligand alcoholic oxygen atom along the crystallographic b axis to produce pleated 2D sheets. In solution, 1 dissociates into [Cu2(HL)2(H3L)]?2H2O ( 2 ); the monomer displays high selectivity for Zn2+ and can be used in HEPES buffer (pH 7.4) as a zinc ion selective luminescent probe for biological application. The system shows a nearly 19‐fold Zn2+‐selective chelation‐enhanced fluorescence response in the working buffer. Application of 2 to cultured living cells (B16F10 mouse melanoma and A375 human melanoma) and rat hippocampal slices was also studied by fluorescence microscopy. 相似文献
10.
Mukherjee A Dhar S Nethaji M Chakravarty AR 《Dalton transactions (Cambridge, England : 2003)》2005,(2):349-353
The ternary iron(II) complex [Fe(L')(L")](PF6)3(1) as a synthetic model for the bleomycins, where L' and L" are formed from metal-mediated cyclizations of N,N'-(2-hydroxypropane-1,3-diyl)bis(pyridine-2-aldimine)(L), is synthesized and structurally characterized by X-ray crystallography. In the six-coordinate iron(ii) complex, ligands L' and L" show tetradentate and bidentate chelating modes of bonding. Ligand L' is formed from an intramolecular attack of the alcoholic OH group of L to one imine moiety leading to the formation of a stereochemically constrained five-membered ring. Ligand L" which is formed from an intermolecular reaction involving one imine moiety of L and pyridine-2-carbaldehyde has an emissive cationic imidazopyridine pendant arm. The complex binds to double-stranded DNA in the minor groove giving a Kapp value of 4.1 x 10(5) M(-1) and displays oxidative cleavage of supercoiled DNA in the presence of H2O2 following a hydroxyl radical pathway. The complex also shows photo-induced DNA cleavage activity on UV light exposure involving formation of singlet oxygen as the reactive species. 相似文献