全文获取类型
收费全文 | 441篇 |
免费 | 32篇 |
专业分类
化学 | 352篇 |
力学 | 5篇 |
数学 | 25篇 |
物理学 | 91篇 |
出版年
2023年 | 8篇 |
2022年 | 16篇 |
2021年 | 13篇 |
2020年 | 10篇 |
2019年 | 32篇 |
2018年 | 16篇 |
2017年 | 16篇 |
2016年 | 20篇 |
2015年 | 19篇 |
2014年 | 22篇 |
2013年 | 40篇 |
2012年 | 37篇 |
2011年 | 50篇 |
2010年 | 10篇 |
2009年 | 12篇 |
2008年 | 34篇 |
2007年 | 22篇 |
2006年 | 15篇 |
2005年 | 18篇 |
2004年 | 5篇 |
2003年 | 5篇 |
2002年 | 7篇 |
2001年 | 2篇 |
2000年 | 3篇 |
1999年 | 3篇 |
1998年 | 3篇 |
1996年 | 1篇 |
1995年 | 2篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 4篇 |
1991年 | 2篇 |
1990年 | 3篇 |
1989年 | 3篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1968年 | 1篇 |
排序方式: 共有473条查询结果,搜索用时 15 毫秒
81.
We have modified the holographic model of Saremi and Son [12] by using a charged black brane, instead of a neutral one, such that when the bulk pseudo scalar (θ ) potential is made of θ2 and θ4 terms, parity can still be broken spontaneously in the boundary theory. In our model, the 3+1 dimensional bulk has a pseudo scalar coupled to the gravitational Chern–Simons term in the anti de Sitter charged black brane back ground. Parity could be broken spontaneously in the bulk by the pseudo scalar hairy solution and give rise to non-zero Hall viscosity at the boundary theory. 相似文献
82.
Keyur D. Bhatt Hrishikesh S. Gupte Bharat A. Makwana Disha J. Vyas Debdeep Maity Vinod K. Jain 《Journal of fluorescence》2012,22(6):1493-1500
Novel Supramolecular fluorescence receptor derived from calix-system i.e. calix[4]resorcinarene bearing dansylchloride as fluorophore was designed and synthesized. The compound was purified by column chromatography and characterized by elemental analysis, NMR and Mass spectroscopy. Tetradansylated calix[4] resorcinarene (TDCR) shows a boat conformation with C2v symmetry. The complexation behaviour of metal cations [Ag(I), Cd(II), Co(II), Fe(III), Hg(II), Cu(II), Pb(II), Zn(II), U(VI) (1?×?10-4?M)] with tetra dansylated calix[4]resorcinarene (1?×?10-6?M) was studied by spectophotometry and spectrofluorometry. Red shift in the absorption spectra led us to conclude that there is strong complexation Fe(III), Co(II) and Cu(II) with TDCR. These metal cations also produce quenching with red shifts in the emission spectra. The maximum quenching in emission intensity was observed in the case of Fe(III) and its binding constant was also found to be significantly higher than that of Co(II) and Cu(II). Quantum yield of metal complexes of Fe(III) was found to be lower in comparison with Co(II) and Cu(II) complexes. Stern Volmer analysis indicates that the mechanism of fluorescence quenching is either purely dynamic, or purely static. 相似文献
83.
84.
Maity P Wakabayashi T Ichikuni N Tsunoyama H Xie S Yamauchi M Tsukuda T 《Chemical communications (Cambridge, England)》2012,48(49):6085-6087
Organogold clusters Au(54)(C(2)Ph)(26) were selectively synthesized by reacting polymer-stabilized Au clusters (1.2 ± 0.2 nm) with excess phenylacetylene in chloroform. 相似文献
85.
A novel quinoline-coumarin (QC) fluoroionophore conjugated by means of a triazolyl-pyrrolidinyl linker exhibits differential dual selectivity for Zn(2+) and Al(3+) in mixed media. QC acts as a turn on fluorescence sensor for Zn(2+) while exhibiting overall ratiometric selectivity for Al(3+) in aqueous media. Moreover, QC exhibited preferential second mode of selectivity for Al(3+) as it ratiometrically displaces Zn(2+) from the [QC + Zn(2+)] complex. 相似文献
86.
The single crystal X-ray diffraction study of capped γ-peptide reveal that the peptide adopts helical conformation which self-assemble to form a supramolecular parallel double helical structure using intermolecular hydrogen bonding as well as π-π stacking interactions in the solid state. 相似文献
87.
Arsenic(III) sorption on nanostructured cerium incorporated manganese oxide (NCMO): a physical insight into the mechanistic pathway 总被引:1,自引:0,他引:1
Gupta K Bhattacharya S Nandi D Dhar A Maity A Mukhopadhyay A Chattopadhyay DJ Ray NR Sen P Ghosh UC 《Journal of colloid and interface science》2012,377(1):269-276
Arsenic(III) sorption was investigated with nanostructured cerium incorporated manganese oxide (NCMO). The pH between 6.0 and 8.0 was optimized for the arsenic(III) sorption. Kinetics and equilibrium data (pH=7.0±0.2, T=303±1.6 K, and I=0.01 M) of arsenic(III) sorption by NCMO described, respectively, the pseudo-second order and the Freundlich isotherm equations well. The sorption process was somewhat complicated in nature and divided into two different segments, initially very fast sorption followed by slow intraparticle diffusion process. Sorption reaction of arsenic(III) on NCMO was endothermic (ΔH°=+13.46 kJ mol(-1)) and spontaneous (ΔG°=-24.75 to -30.15 kJ mol(-1) at T=283-323 K), which took place with increasing entropy (ΔS°=+0.14 kJ mol(-1)K(-1)) at solid-liquid interface. Energy of arsenic(III) sorption estimated by analyzing the equilibrium data using the D-R isotherm model was 15.4 kJ mol(-1), indicating the ion-exchange type mechanism. Raman, FT-IR, pH effect, desorption, etc. studies indicated that arsenic(III) was oxidized to arsenic(V) during the sorption process. 相似文献
88.
Maity S Choquette KA Flowers RA Prasad E 《The journal of physical chemistry. A》2012,116(9):2154-2160
Electron transfer from the ground and excited states of Sm[15-crown-5](2)I(2) complex to a series of electron acceptors (benzaldehyde, acetophenone, benzophenone, nitrobenzene, benzyl bromide, benzyl chloride, 1-iodohexane, and 1,4-dinitrobenzene) was investigated in acetonitrile. Electron transfer from the ground state of the Sm(II)-crown system to aldehydes and ketones has a significant inner sphere component indicating that the oxophilic nature of Sm(II) prevails in the system even in the presence of bulky ligands such as 15-crown-5 ether. Activation parameters for the ground state electron transfer were determined, and the values were consistent with the proposed mechanistic models. Since crown ethers stabilize the photoexcited states of Sm(II), the photochemistry of Sm[15-crown-5](2)I(2) system in solution state has been investigated in detail. The results suggest that photoinduced electron transfer from Sm(II)-crown systems to a wide variety of substrates is feasible with rate constant values as high as 10(7) M(-1) s(-1). The results described herein imply that the present difficulty of manipulating the extremely reactive excited state of Sm(II) in solution phase can be overcome through stabilizing the excited state of the divalent metal ion by careful design of the ligand systems. 相似文献
89.
Axisymmetric flow of thin pure liquid film on a spinning horizontal annular disk is studied under the action of air shear at the liquid–air interface and evaporation. The non-linear evolution equation that is obtained by singular perturbation method is solved analytically, for small Reynolds number, by using the method of characteristic and numerically by the use of Newton–Kantorovich method for any Reynolds number. Font breakdown time and its location from the center of the disk is predicted both by analytically and numerically. The result shows that the thinning of the initial film increases as air stress increase, same result is also escalated in presence of evaporation. 相似文献
90.
Dr. Suman Kumar Maity Paul Stahl Dr. Astrid Hensel Prof. Dr. Shirley Knauer Dr. Christoph Hirschhäuser Prof. Dr. Carsten Schmuck 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(14):3010-3015
Tumor-targeted drug delivery is highly important for improving chemotherapy, as it reduces the dose of cytotoxic agents and minimizes the death of healthy tissues. Towards this goal, a conjugate was synthesized of gossypol and a MCF-7 cancer cell specific CPP (cell penetrating peptide), thus providing a selective drug delivery system. Utilizing the aldehyde moiety of gossypol, the tumor homing CPP RLYMRYYSPTTRRYG was attached through a semi-labile imine linker, which was cleaved in a traceless fashion under aqueous conditions and had a half-life of approximately 10 hours. The conjugate killed MCF-7 cells to a significantly greater extent than HeLa cells or healthy fibroblasts. 相似文献