全文获取类型
收费全文 | 1739篇 |
免费 | 55篇 |
国内免费 | 5篇 |
专业分类
化学 | 1193篇 |
晶体学 | 15篇 |
力学 | 40篇 |
数学 | 122篇 |
物理学 | 429篇 |
出版年
2023年 | 21篇 |
2022年 | 27篇 |
2021年 | 33篇 |
2020年 | 32篇 |
2019年 | 47篇 |
2018年 | 32篇 |
2017年 | 30篇 |
2016年 | 37篇 |
2015年 | 21篇 |
2014年 | 46篇 |
2013年 | 99篇 |
2012年 | 132篇 |
2011年 | 125篇 |
2010年 | 77篇 |
2009年 | 54篇 |
2008年 | 108篇 |
2007年 | 85篇 |
2006年 | 74篇 |
2005年 | 105篇 |
2004年 | 62篇 |
2003年 | 48篇 |
2002年 | 30篇 |
2001年 | 42篇 |
2000年 | 28篇 |
1999年 | 25篇 |
1998年 | 14篇 |
1997年 | 21篇 |
1996年 | 17篇 |
1995年 | 20篇 |
1994年 | 14篇 |
1993年 | 16篇 |
1992年 | 12篇 |
1991年 | 13篇 |
1990年 | 7篇 |
1989年 | 10篇 |
1988年 | 14篇 |
1986年 | 10篇 |
1985年 | 20篇 |
1984年 | 20篇 |
1983年 | 10篇 |
1982年 | 15篇 |
1981年 | 9篇 |
1980年 | 10篇 |
1979年 | 8篇 |
1978年 | 12篇 |
1976年 | 8篇 |
1975年 | 11篇 |
1974年 | 8篇 |
1971年 | 8篇 |
1970年 | 9篇 |
排序方式: 共有1799条查询结果,搜索用时 31 毫秒
91.
A new exactly solvable ()-dimensional complex nonlinear wave equation exhibiting rich analytic properties has been introduced. A rogue wave (RW), localized in space–time like Peregrine RW solution, though richer due to the presence of free parameters is discovered. This freedom allows to regulate amplitude and width of the RW as needed. The proposed equation allows also an intriguing topology changing accelerated dark soliton solution in spite of constant coefficients in the equation. 相似文献
92.
Rana Chatterjee Satyajit Samanta Anindita Mukherjee Sougata Santra Grigory V. Zyryanov Adinath Majee 《Tetrahedron letters》2019,60(3):276-283
We have observed that the allylic zinc halide under identical reaction conditions acts in different modes for different electrophiles. For Ts-aziridines the halide part of the allylic halide has been introduced as a nucleophile and for the carbonyl compounds the simple allylation reaction occurs. To the best of our knowledge this is the first report where the allylic zinc halide is the source of halide acting as nucleophile. The main advantages of the present procedure are easy to handle, no need of inert atmosphere, mild reaction conditions, and applicability to a wide variety of substrates for aziridines and carbonyl compounds. 相似文献
93.
94.
Arun Kumar Bar Dr. Srinivasarao Raghothama Dr. Dohyun Moon Prof. Partha Sarathi Mukherjee 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(11):3199-3209
Template‐assisted formation of multicomponent Pd6 coordination prisms and formation of their self‐templated triply interlocked Pd12 analogues in the absence of an external template have been established in a single step through Pd? N/Pd? O coordination. Treatment of cis‐[Pd(en)(NO3)2] with K3tma and linear pillar 4,4′‐bpy (en=ethylenediamine, H3tma=benzene‐1,3,5‐tricarboxylic acid, 4,4′‐bpy=4,4′‐bipyridine) gave intercalated coordination cage [{Pd(en)}6(bpy)3(tma)2]2[NO3]12 ( 1 ) exclusively, whereas the same reaction in the presence of H3tma as an aromatic guest gave a H3tma‐encapsulating non‐interlocked discrete Pd6 molecular prism [{Pd(en)}6(bpy)3(tma)2(H3tma)2][NO3]6 ( 2 ). Though the same reaction using cis‐[Pd(NO3)2(pn)] (pn=propane‐1,2‐diamine) instead of cis‐[Pd(en)(NO3)2] gave triply interlocked coordination cage [{Pd(pn)}6(bpy)3(tma)2]2[NO3]12 ( 3 ) along with non‐interlocked Pd6 analogue [{Pd(pn)}6(bpy)3(tma)2](NO3)6 ( 3′ ), and the presence of H3tma as a guest gave H3tma‐encapsulating molecular prism [{Pd(pn)}6(bpy)3(tma)2(H3tma)2][NO3]6 ( 4 ) exclusively. In solution, the amount of 3′ decreases as the temperature is decreased, and in the solid state 3 is the sole product. Notably, an analogous reaction using the relatively short pillar pz (pz=pyrazine) instead of 4,4′‐bpy gave triply interlocked coordination cage [{Pd(pn)}6(pz)3(tma)2]2[NO3]12 ( 5 ) as the single product. Interestingly, the same reaction using slightly more bulky cis‐[Pd(NO3)2(tmen)] (tmen=N,N,N′,N′‐tetramethylethylene diamine) instead of cis‐[Pd(NO3)2(pn)] gave non‐interlocked [{Pd(tmen)}6(pz)3(tma)2][NO3]6 ( 6 ) exclusively. Complexes 1 , 3 , and 5 represent the first examples of template‐free triply interlocked molecular prisms obtained through multicomponent self‐assembly. Formation of the complexes was supported by IR and multinuclear NMR (1H and 13C) spectroscopy. Formation of guest‐encapsulating complexes ( 2 and 4 ) was confirmed by 2D DOSY and ROESY NMR spectroscopic analyses, whereas for complexes 1 , 3 , 5 , and 6 single‐crystal X‐ray diffraction techniques unambiguously confirmed their formation. The gross geometries of H3tma‐encapsulating complexes 2 and 4 were obtained by universal force field (UFF) simulations. 相似文献
95.
Sreemoyee Mukherjee M. Manninen P. Singha Deo 《Physica E: Low-dimensional Systems and Nanostructures》2011,44(1):62-66
We start from microscopic approach to many body physics and show the analytical steps and approximations required to arrive at the concept of quantum capacitance. These approximations are valid only in the semi-classical limit and the quantum capacitance in that case is determined by Lindhard function. The effective capacitance is the geometrical capacitance and the quantum capacitance in series, and this too is established starting from a microscopic theory. 相似文献
96.
The tricyclic enones 15–20, intermediates to several sesqui-and diterpenes, have been synthesised in high yields involving selective hydrogenation of the disubstituted double bonds of the dienones 9-14 respectively in the presence of tris (triphenylphosphine)rhodium(I) chloride catalyst. 相似文献
97.
Bijay K. Mishra Partha Mukherjee Sukalyan Dash Sabita Patel Hari N. Pati 《合成通讯》2013,43(14):2529-2539
Some monomeric and dimeric surfactants with functional head groups have been synthesized from di- and triethanolamine synthons. The treatment of alkyl bromide with triethanolamine resulted in simultaneous N-alkylation and O-alkylation products. However, with diethanolamine, N-alkylated products were obtained, which were further used to synthesize various double-tailed surfactants and gemini surfactants. 相似文献
98.
99.
Indrajyoti Mukherjee Dipankar Haldar Soumen Ghosh 《Journal of Dispersion Science and Technology》2013,34(10):1430-1441
APSA-80, an useful pesticide spray adjuvant is a mixture of 2-[2-(4-nonylphenoxy) ethoxy] ethanol, 1-butanol and tall oil fatty acids. It is strongly surface active and can decrease the surface tension of water to ~20 mNm?1 at its critical micelle concentration (CMC) of 0.006 g%. APSA-80 itself and its binary mixtures, (APSA-80 + water) and (APSA-80 + isopropylmyristate [IPM]) and ternary mixtures (APSA-80 + water +IPM) can undergo a number of physical changes with rise in temperature; the main changes are in color, turbidity and phases. The ternary mixtures of APSA-80/water/IPM with changing compositions can form mono-, bi-, and triphasic solutions as well as gels and viscous solutions. The gel and viscous phases show characteristic rheological properties of both shear thinning and thickening types. They also show permeation of hydrophilic and oleophilic dyes through them. SEM and optical microscopic measurements have shown interesting surface morphologies of the gels and their vertical projections in three-dimensional pictorial mode. Salts like LiCl, NaCl, KCl, CsCl, MgSO4, and Al2(SO4)3 can have both minor and major effects on the gel consistencies. The alkanols like ethanol, propanol, and isopropanol are also mild to fairly large gel influencing co solvents. The antibacterial properties of APSA-80 have been studied with two Gram positive bacteria and a yeast; the activities found were moderate. 相似文献
100.
The temperature‐ and electric field‐dependent dielectric relaxation and polarisation of a new chiral swallow tailed antiferroelectric liquid crystal, i.e. 1‐ethylpropyl (S)‐2‐{6‐[4‐(4′‐decyloxyphenyl)benzoyloxy]‐2‐naphthyl}propionate (abbreviated as EP10PBNP), were investigated. The electric field‐induced dielectric loss spectra of EP10PBNP revealed electroclinic and anomalous dielectric behaviour in the chiral smectic A (SmA*)–chiral antiferroelectric smectic C (SmCA*) pre‐transitional regime. From an analysis of thermal hysteresis of the dielectric constant, electric field‐induced polarisation and dielectric loss spectra, the appearance of a ferrielectric‐like mesophase is observed followed by an unstable SmCA* phase in the SmA*–SmCA* pre‐transitional regime. 相似文献