全文获取类型
收费全文 | 1227篇 |
免费 | 49篇 |
国内免费 | 1篇 |
专业分类
化学 | 772篇 |
晶体学 | 8篇 |
力学 | 44篇 |
数学 | 82篇 |
物理学 | 371篇 |
出版年
2023年 | 12篇 |
2022年 | 10篇 |
2021年 | 22篇 |
2020年 | 18篇 |
2019年 | 34篇 |
2018年 | 20篇 |
2017年 | 25篇 |
2016年 | 46篇 |
2015年 | 36篇 |
2014年 | 32篇 |
2013年 | 81篇 |
2012年 | 71篇 |
2011年 | 90篇 |
2010年 | 48篇 |
2009年 | 42篇 |
2008年 | 63篇 |
2007年 | 47篇 |
2006年 | 54篇 |
2005年 | 46篇 |
2004年 | 32篇 |
2003年 | 30篇 |
2002年 | 27篇 |
2001年 | 26篇 |
2000年 | 11篇 |
1999年 | 18篇 |
1998年 | 11篇 |
1997年 | 8篇 |
1996年 | 12篇 |
1995年 | 13篇 |
1994年 | 14篇 |
1993年 | 18篇 |
1992年 | 14篇 |
1991年 | 16篇 |
1990年 | 12篇 |
1989年 | 9篇 |
1986年 | 7篇 |
1985年 | 8篇 |
1984年 | 15篇 |
1983年 | 16篇 |
1982年 | 15篇 |
1981年 | 13篇 |
1980年 | 13篇 |
1979年 | 11篇 |
1978年 | 10篇 |
1977年 | 15篇 |
1976年 | 10篇 |
1975年 | 10篇 |
1973年 | 6篇 |
1971年 | 5篇 |
1966年 | 5篇 |
排序方式: 共有1277条查询结果,搜索用时 31 毫秒
71.
Linear {NiII–LnIII–NiII} Complexes Containing Twisted Planar Ni(μ‐phenolate)2Ln Fragments: Synthesis,Structure, and Magnetothermal Properties 下载免费PDF全文
Sourav Das Atanu Dey Subrata Kundu Sourav Biswas Prof. Dr. A. J. Mota Prof. Dr. Enrique Colacio Prof. Dr. Vadapalli Chandrasekhar 《化学:亚洲杂志》2014,9(7):1876-1887
Sequential reaction of a multisite LH4 ligand {2‐[2‐hydroxy‐3‐(hydroxymethyl)‐5‐methylbenzylideneamino]‐2‐methylpropane‐1,3‐diol} with appropriate lanthanide salts followed by the addition of Ni(NO3)2 ? 6 H2O in a 4:1:2 stoichiometric ratio in the presence of triethylamine afforded four heterobimetallic trinuclear complexes [Ni2Gd(LH3)4] ? 3 NO3 ? 3 MeOH ? H2O ? CH3CN ( 1 ), [Ni2Tb(LH3)4] ? 3 NO3 ? 3 MeOH ? CH3CN ( 2 ), [Ni2Dy(LH3)4] ? 3 NO3 ? 3 MeOH ? H2O ? CH3CN ( 3 ), and [Ni2Ho(LH3)4] ? 3 NO3 ? 3 MeOH ? H2O ? CH3CN ( 4 ). Complexes 1 – 4 possess linear trimetallic cores with a central lanthanide ion. Magnetic studies revealed a predominant ferromagnetic interaction between the Ni and Ln centers. Alternating current susceptibility measurements of complex 3 showed a small frequency dependence of the out‐of‐phase signal, χ′′M , under zero direct current field, but without achieving a net maximum above 2 K. Magnetic studies on 1 revealed that it has a significant magnetocaloric effect. 相似文献
72.
Bhaskar Bishayee Biswajit Ruj Santanu Nandi Rishya Prava Chatterjee Aparajita Mallick Prasenjit Chakraborty Jayato Nayak Sankha Chakrabortty 《印度化学会志》2022,99(1):100302
The current investigation involves a continuous adsorption experiment in a packed bed column for the sorptive elucidation of fluoride from contaminated groundwater using an activated soil-clay mixture. Through the combination of naturally accessible laterite soil with silica enriched clay (3:1 ratio), a low-cost Al–Si heterogeneous material has been developed. Following detailed characterization, the developed materials were employed in a long-time column process to achieve a high degree of fluoride separation from real-world groundwater. In a packed bed column investigation, the effect of bed height, initial fluoride concentration, and flow rate on the breakthrough properties of the adsorption system were investigated. By using a non-linear regression equation, three model kinetics, such as the Thomas Model, Adams-Bohart Model, and Yoon-Nelson Model, were fitted to validate the column-based experimental data, by analysing the breakthrough curves profiles, and distinct kinetic parameters. The Bed Depth Service Time Analysis (BDST) model was tested to express the effect of bed height on breakthrough curves, as well as to predict the time for breakthrough, and material depletion under optimal conditions. The Thomas and Yoon-Nelson models were identified to be the most appropriate ones for describing the entire breakthrough curve, whereas the Adams-Bohart model was only utilised to predict the first half of the dynamic process. With correlation coefficients (R2) 0.96, the experimental results were well suited to Thomas, Yoon-Nelson, and Adams-Bohart models. Finally, regeneration assessment was carried out where even after four cycles of operation, regenerated adsorbent showed a rejection efficacy of 78% to fluoride that proves the viability of the material and methodology. 相似文献
73.
Anindita Chatterjee 《印度化学会志》2022,99(9):100653
Synthesis of pure Zinc oxide (ZnO), Copper oxide (CuO) nanoparticles (NPs) and their (ZnO/CuO) nanocomposites (NCs) in 1:1 M ratio were successfully prepared by co-precipitation method. The structural properties of the as synthesized nanoparticles and nanocomposite materials were investigated using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD) techniques. Optical band-gap studies were done using UV–Visible absorption spectroscopy. Photovoltaic properties of pure ZnO NPs, CuO NPs and ZnO/CuO NCs coated over a single-crystalline silicon solar cell were carried out to compare improvement of light-conversion efficiency in coated solar cell. The maximum light conversion efficiencies were found to be of 8.02% for CuO (3 mg/ml concentration) and 7.28% for ZnO NPs (3 mg/ml concentration), whereas that of mixed metal nanocomposite CuO/ZnO NCs was found to be 7.62%. at very low concentration of 1 mg/ml. This indicates with low concentration of mixed metal NCs an improvement in light efficiency can be obtained. The enhancement in efficiency could be due to formation of p - n heterojunction by CuO/ZnO NCs composites which enhances the number of electrons and holes participating in conduction on the surface. 相似文献
74.
Kanigel A Chatterjee U Randeria M Norman MR Souma S Shi M Li ZZ Raffy H Campuzano JC 《Physical review letters》2007,99(15):157001
Angle resolved photoemission on underdoped Bi2Sr2CaCu2O8 reveals that the magnitude and d-wave anisotropy of the superconducting state energy gap are independent of temperature all the way up to T{c}. This lack of T variation of the entire k-dependent gap is in marked contrast to mean field theory. At T{c} the point nodes of the d-wave gap abruptly expand into finite length "Fermi arcs." This change occurs within the width of the resistive transition, and thus the Fermi arcs are not simply thermally broadened nodes but rather a unique signature of the pseudogap phase. 相似文献
75.
Stereospecific Formal [3+2] Dipolar Cycloaddition of Cyclopropanes with Nitrosoarenes: An Approach to Isoxazolidines 下载免费PDF全文
Shyamal Chakrabarty Dr. Indranil Chatterjee Birgit Wibbeling Dr. Constantin Gabriel Daniliuc Prof. Dr. Armido Studer 《Angewandte Chemie (International ed. in English)》2014,53(23):5964-5968
The MgBr2‐catalyzed formal [3+2] cycloaddition of donor–acceptor activated cyclopropanes with nitrosoarenes offers a novel approach to various structurally diverse isoxazolidines. The reactions, which are experimentally easy to conduct, occur with complete stereospecificity and perfect control of regioselectivity. Product isoxazolidines can be readily transformed into α‐amino lactones by reductive or decarboxylative N? O cleavage and subsequent lactonisation, and the N‐aryl bond cleavage is also possible under oxidative conditions. 相似文献
76.
Debabrata Chatterjee Swapan Kumar Moulik Lingamallu Giribabu Ravi Kumar Kanaparthi 《Transition Metal Chemistry》2014,39(6):641-646
The Fe(III) complex, [FeIII(HQS)3] (HQS = 8-hydroxyquinoline-5-sulfonic acid), is found to effect sensitization of the large band gap semiconductor, TiO2. The role of interfacial electron transfer in sensitization of TiO2 nanoparticles by surface adsorbed [FeIII(HQS)3] was studied using femtosecond time scale transient absorption spectroscopy. Electron injection has been confirmed by direct detection of the electron in the conduction band. A TiO2-based dye-sensitized solar cell (DSSC) was fabricated using [FeIII(HQS)3] as a sensitizer, and the resulting DSSC exhibited an open-circuit voltage value of 425 mV. The value of the short-circuit photocurrent was found to be 2.5 mA/cm2. The solar to electric power conversion efficiency of the [FeIII(HQS)3] sensitized TiO2-based DSSC device was 0.75 %. The results are discussed in the context of sensitization of TiO2 by other Fe(II)-dye complexes. 相似文献
77.
78.
79.
Venkata Reddy Regalla RamaKrishnam Raju Addada Venkat Swami Puli Abhishek S. Saxena Anindita Chatterjee 《Tetrahedron letters》2017,58(24):2344-2346
A short and efficient method for the stereoselective synthesis of Dendrodolide L has been developed from inexpensive and commercially available starting material. This convergent synthesis utilizes Jacobsen kinetic resolution, regioselective ring-opening of epoxide and Yamaguchi macrolactonization as key steps. 相似文献
80.
Oxidation of Ru(III)‐Bound Thiocyanate with Peroxomonosulfate: Kinetic and Mechanistic Studies 下载免费PDF全文
The reaction of [RuIII(edta)(SCN)]2? (edta4? = ethylenediaminetetraacetate; SCN? = thiocyanate ion) with the peroxomonosulfate ion (HSO5?) has been studied by using stopped‐flow and rapid scan spectrophotometry as a function of [RuIII(edta)], [HSO5?], and temperature (15–30ºC) at constant pH 6.2 (phosphate buffer). Spectral analyses and kinetic data are suggestive of a pathway in which HSO5? effects the oxidation of the coordinated SCN? by its direct attack at the S‐atom (of SCN?) coordinated to the RuIII(edta). The high negative value of entropy of activation (ΔS≠ = ?90 ± 6 J mol?1 deg?1) is consistent with the values reported for the oxygen atom transfer process involving heterolytic cleavage of the O‐O bond in HSO5?. Formation of SO42?, SO32?, and OCN? was identified as oxidation products in ESI‐MS experiments. A detailed mechanism in agreement with the spectral and kinetic data is presented. 相似文献