全文获取类型
收费全文 | 362篇 |
免费 | 17篇 |
专业分类
化学 | 235篇 |
晶体学 | 3篇 |
力学 | 10篇 |
数学 | 57篇 |
物理学 | 74篇 |
出版年
2023年 | 5篇 |
2022年 | 5篇 |
2021年 | 11篇 |
2020年 | 9篇 |
2019年 | 6篇 |
2018年 | 12篇 |
2017年 | 5篇 |
2016年 | 12篇 |
2015年 | 8篇 |
2014年 | 7篇 |
2013年 | 21篇 |
2012年 | 23篇 |
2011年 | 22篇 |
2010年 | 9篇 |
2009年 | 11篇 |
2008年 | 16篇 |
2007年 | 23篇 |
2006年 | 14篇 |
2005年 | 20篇 |
2004年 | 11篇 |
2003年 | 20篇 |
2002年 | 11篇 |
2001年 | 4篇 |
2000年 | 3篇 |
1999年 | 4篇 |
1998年 | 3篇 |
1997年 | 3篇 |
1996年 | 3篇 |
1995年 | 3篇 |
1990年 | 2篇 |
1989年 | 3篇 |
1988年 | 3篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1985年 | 4篇 |
1984年 | 7篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1981年 | 2篇 |
1979年 | 3篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1976年 | 5篇 |
1974年 | 3篇 |
1973年 | 3篇 |
1972年 | 3篇 |
1971年 | 5篇 |
1970年 | 3篇 |
1969年 | 5篇 |
1967年 | 2篇 |
排序方式: 共有379条查询结果,搜索用时 15 毫秒
51.
In a previous communication we discussed the integrability of a long-wave, short-wave interaction equation for very restricted values of the parameters in the framework of the theory laid down by Weisset al. Here we proceed with the analysis in the sense of Weisset al., considering values of parameters other than those we used previously. We observe that for the combination of parameters for which a Lax pair was obtained by another approach (Newell), the equations considered pass the Painlevé test for integrability in the sense of Weisset al. We discuss several other combinations of parameters that do not pass the test. For these cases no Lax Pair was reported by Newell. 相似文献
52.
Sridhar L. Chennuri B. C. Haldar 《Journal of Radioanalytical and Nuclear Chemistry》1984,84(1):197-200
A method has been developed for the extraction of Zn(II) with ethylthioacetoacetate (HETAcAc) into ethyl acetate from an alkaline medium. Various parameters affecting the extraction of Zn(II) have been investigated. The stoichiometry of the extracted species has been determined by the slope-ratio method. 相似文献
53.
Sourav Haldar Mamata Kombrabail G. Krishnamoorthy Amitabha Chattopadhyay 《Journal of fluorescence》2010,20(1):407-413
Due to the inherent difficulty in crystallizing membrane proteins, approaches based on fluorescence spectroscopy have proved
useful in elucidating their conformational characteristics. The ion channel peptide gramicidin serves as an excellent prototype
for monitoring membrane protein conformation and dynamics due to a number of reasons. We have analyzed conformational heterogeneity
in membrane-bound gramicidin using fluorescence lifetime distribution analysis of tryptophan residues by the maximum entropy
method (MEM). MEM represents a model-free and robust approach for analyzing fluorescence lifetime distribution. In this paper,
we show for the first time, that fluorescence lifetime distribution analysis using MEM could be a convenient approach to monitor
conformational heterogeneity in membrane-bound gramicidin in particular and membrane proteins in general. Lifetime distribution
analysis by MEM therefore provides a novel window to monitor conformational transitions in membrane proteins. 相似文献
54.
Edward C. Eckels Deep Chaudhuri Soham Chakraborty Daniel J. Echelman Shubhasis Haldar 《Chemical science》2021,12(33):11109
DsbA is a ubiquitous bacterial oxidoreductase that associates with substrates during and after translocation, yet its involvement in protein folding and translocation remains an open question. Here we demonstrate a redox-controlled chaperone activity of DsbA, on both cysteine-containing and cysteine-free substrates, using magnetic tweezers-based single molecule force spectroscopy that enables independent measurements of oxidoreductase activity and chaperone behavior. Interestingly we found that this chaperone activity is tuned by the oxidation state of DsbA; oxidized DsbA is a strong promoter of folding, but the effect is weakened by the reduction of the catalytic CXXC motif. We further localize the chaperone binding site of DsbA using a seven-residue peptide which effectively blocks the chaperone activity. We found that the DsbA assisted folding of proteins in the periplasm generates enough mechanical work to decrease the ATP consumption needed for periplasmic translocation by up to 33%.Protein translocation is facilitated by DsbA chaperone in a redox-dependent manner. 相似文献
55.
Anindita Sikdar Swapnadip Roy Kakali Haldar Soma Sarkar Sujit S. Panja 《Journal of fluorescence》2013,23(3):495-501
A rhodamine B-based fluorescence probe (1) for the sensitive and selective detection of Cu2+ ion has been designed and synthesized using pyridine moiety. The optical properties of this compound have been investigated in acetonitrile-water binary solution (7:3 v/v). Compound 1 is found to be an excellent sensor for a biologically/physiologically very important transition metal ion (Cu2+) using only the two very different modes of measurements (absorption and emission); one case displayed intensity enhancement whereas in other case showed intensity depletion (quenching). A mechanistic investigation has been performed to explore the static nature of quenching process. The sensor has been found to be very effective in sensing Cu2+ ion inside living cells also. 相似文献
56.
Bijeta Mitra Suvodip Mukherjee Gyan Chandra Pariyar Pranab Ghosh 《Tetrahedron letters》2018,59(14):1385-1389
A versatile, robust and efficient strategy for the synthesis of vast range of highly functionalized 5-substituted 1H-tetrazole derivatives by using one pot three-component synthesis from various aldehydes, hydroxylamine hydrochloride and sodium azide in presence of a catalytic amount of ceric ammonium sulphate, a non toxic, easily available, inexpensive, unexplored and reusable catalyst is reported. This one-pot synthesis has several advantages such as mild reaction conditions, shorter reaction time, low catalyst loading, good to moderate yields and functional group tolerance making this methodology practically feasible. The synthesized compounds were characterized by 1H NMR, 13C NMR and HRMS. 相似文献
57.
Transamidation involves direct interconversion of an amide with amine, and represents an alternative to the common method of amide formation from the reaction of carboxylic acid with an amine. While the carboxamides have huge potential in biological systems and polymer industries, their formation from carboxylic acids requires activation by a suitable catalyst. A metal-free transamidation of aliphatic amide with aromatic amine catalyzed by graphene oxide (GO) has been developed and established as a general, synthetically useful and selective procedure. Graphene oxide bearing several carboxylic acids on the edges and having large surface area acts as an efficient and recyclable catalyst for transamidation. 相似文献
58.
Pranab Kumar Tarafder Susanta Kumar Pradhan Shaswati Roychowdhury 《Journal of Radioanalytical and Nuclear Chemistry》2018,316(2):527-534
An extractive pellet fluorimetry determination of trace uranium in thorium rich samples has been developed. This is based upon a solvent extraction system which completely separates both the elements uranium and thorium from each other. Thorium as a neutral complex with 2,3-dihydroxynaphthalene at pH 4–6 is extracted into ethylacetate and then uranium-2,3-dihydroxynaphthalene anionic complex is extracted into another batch of ethylacetate at pH 11–12 under the influence of a counter cation, cetyltrimethylammonium ion. This method has been applied for the determination of trace uranium in synthetic nuclear grade thorium oxide and thorium rich mineralized rock with high degree of accuracy and precision. 相似文献
59.
Asim K. Bera Bishnu P. Mukhopadhyay Asok K. Pal U. Haldar S. Bhattacharya Asok Banerjee 《Journal of chemical crystallography》1998,28(7):509-516
The crystal structure of an octadecahydrated complex between two inosine 5-monophosphate (IMP) has been determined at atomic resolution, which reveals the hydrogen bonding and the coordination cooperativity of water molecules to nucleotide recognition. The crystal belongs to monoclinic space group P21 with cell dimensions a = 8.65(1), b = 21.90(1), c = 12.37(1)Å, and = 110.38(9)°. The ribose hydroxyls, purine N7, keto(O6) bonded water molecules W1, W2, W5, W6, W8 and the phosphate bridge forming water oxygens of W4, W7, W11 appear to play an invariant role in their hydrogen bonding interactions with the IMPs. The synergistic role of the water molecules W5, W6, W8 in the purine staking domain N27W5=2.583,O16W8=2.759,O2627W6=2.723 Åhave been clearly observed for the first time. The complexation of the water molecules through variable hydrogen bonding coordination indicate their functional involvement through extensive cooperative donor-acceptor network mechanism. The occurrence of hydrogen-bonded water spines, water bridges and their interplay in the structural association of IMPs could indicate the possible viability of those aquatic centers in the biological situation. 相似文献
60.
Haldar S Raghuraman H Chattopadhyay A 《The journal of physical chemistry. B》2008,112(44):14075-14082
Melittin is a cationic hemolytic peptide isolated from the European honey bee, Apis mellifera. In spite of a number of studies, there is no consensus regarding the orientation of melittin in membranes. In this study, we used a melittin analogue that is covalently labeled at its amino terminal (Gly-1) with the environment-sensitive 1-dimethylamino-5-sulfonylnaphthalene (dansyl) group to obtain information regarding the orientation and dynamics of the amino terminal region of membrane-bound melittin. Our results show that the dansyl group in Dns-melittin exhibits red edge excitation shift in vesicles of 1,2-dioleoyl-sn-glycero-3-phosphocholine, implying its localization in a motionally restricted region of the membrane. This is further supported by wavelength-dependent anisotropy and lifetime changes and time-resolved emission spectra characterized by dynamic Stokes shift, which indicates relatively slow solvent relaxation in the excited state. Membrane penetration depth analysis using the parallax method shows that the dansyl group is localized at a depth of approximately 18 A from the center of the bilayer in membrane-bound Dns-melittin. Further analysis of dansyl and tryptophan depths in Dns-melittin shows that the tilt angle between the helix axis of membrane-bound melittin and the bilayer normal is approximately 70 degrees. Our results therefore suggest that melittin adopts a pseudoparallel orientation in DOPC membranes at low concentration. 相似文献