全文获取类型
收费全文 | 4848篇 |
免费 | 266篇 |
国内免费 | 33篇 |
专业分类
化学 | 3302篇 |
晶体学 | 20篇 |
力学 | 101篇 |
数学 | 646篇 |
物理学 | 1078篇 |
出版年
2023年 | 48篇 |
2022年 | 65篇 |
2021年 | 97篇 |
2020年 | 140篇 |
2019年 | 133篇 |
2018年 | 90篇 |
2017年 | 74篇 |
2016年 | 219篇 |
2015年 | 159篇 |
2014年 | 189篇 |
2013年 | 261篇 |
2012年 | 392篇 |
2011年 | 514篇 |
2010年 | 241篇 |
2009年 | 154篇 |
2008年 | 314篇 |
2007年 | 327篇 |
2006年 | 294篇 |
2005年 | 289篇 |
2004年 | 235篇 |
2003年 | 153篇 |
2002年 | 125篇 |
2001年 | 57篇 |
2000年 | 31篇 |
1999年 | 35篇 |
1998年 | 28篇 |
1997年 | 25篇 |
1996年 | 40篇 |
1995年 | 42篇 |
1994年 | 34篇 |
1993年 | 40篇 |
1992年 | 41篇 |
1991年 | 14篇 |
1990年 | 11篇 |
1989年 | 14篇 |
1988年 | 9篇 |
1987年 | 8篇 |
1986年 | 11篇 |
1985年 | 13篇 |
1983年 | 11篇 |
1982年 | 17篇 |
1981年 | 7篇 |
1980年 | 7篇 |
1979年 | 15篇 |
1978年 | 10篇 |
1977年 | 12篇 |
1976年 | 11篇 |
1975年 | 7篇 |
1974年 | 8篇 |
1973年 | 33篇 |
排序方式: 共有5147条查询结果,搜索用时 78 毫秒
141.
Chen Hui Sharma Sunil K. Sharma Priyanka R. Chi Kai Fung Eric Aubrecht Katherine Keroletswe Ngonye Chigome Samuel Hsiao Benjamin S. 《Cellulose (London, England)》2021,28(13):8611-8628
Cellulose - Mercury contamination in drinking water is a worldwide problem due to its severely harming effects on the human body. A nanostructured natural bioadsorbent, carboxycellulose nanofiber... 相似文献
142.
Benjamin M. Long 《Supramolecular chemistry》2013,25(1-2):136-140
The use of modified Job plot methodology provides a quick and easy means for evaluating host–guest stoichiometry and requires less material than the original method. In this short paper, the results of a recent anion recognition study using thiourea-functionalised norbornanes and [n]polynorbornanes are presented. A significant difference between the plots constructed using the original and modified method was observed and, as such, caution is advised when the modified Job's method is solely used for the determination of host–guest stoichiometry. 相似文献
143.
144.
145.
Structural Chemistry - The conformation-selective IR spectroscopy of the alanine dipeptide analogue Ac-Ala-NH2, a molecule deprived of a UV chromophore, has been obtained by laser double-resonance... 相似文献
146.
Meredith C. K. Sellers Benjamin M. Castle Charles P. Marsh 《Journal of Solid State Electrochemistry》2013,17(1):175-182
Three-dimensional manganese dioxide (MnO2)-functionalized multiwalled carbon nanotube (MWCNT) electrodes have been produced by a simple and scalable thermal decomposition process. The electrodes are prepared by treating planar MWCNT sheets with manganese(II) nitrate (Mn(NO3)2) solution and annealing at low temperature (200–300 °C) and ambient pressure. The morphology, chemical composition, and structure of the resulting matrices have been investigated with scanning electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, and X-ray diffraction. Supercapacitors assembled with three-dimensional electrodes exhibit a 14-fold increase in specific capacitance (C sp) in comparison to those containing pristine, two-dimensional MWCNT electrodes. C sp varies linearly with Mn(NO3)2 thermal decomposition temperature (from 100 to 61 F/g at 0.2 A/g), a trend that is discussed in the context of nitrate reaction chemistry and MWCNT structure. This efficient and promising approach allows for simultaneous enhancement of electrode–electrolyte contact area and incorporation of redox-based charge storage within electrochemical capacitors. 相似文献
147.
Georgy M. Pavlov Anke Teichler Stephanie Höppener Christine Weber Jürgen Nowotny Lars Blankenburg Jürgen Popp Martin D. Hager Benjamin Dietzek Ulrich S. Schubert 《Journal of polymer science. Part A, Polymer chemistry》2012,50(15):3192-3205
In order to form suitable systems designed for resonance energy transfer, a series of monodisperse methacrylate‐based monomers containing rigid π‐conjugated oligo(phenylene ethynylenes) with different sizes of the conjugated systems ( M1 – M3 ), and therefore different optoelectronic properties, were synthesized and subsequently polymerized using the reversible addition–fragmentation chain transfer polymerization technique ( P1 – P3 ). In addition, these oligomers were also copolymerized with methyl methacrylate. The obtained polymers were characterized by 1H NMR spectroscopy, size exclusion chromatography, and analytical ultracentrifugation. The photophysical properties of the polymers were studied by UV–vis absorption and emission spectroscopy in diluted solutions as well as in thin films and compared to the photophysics of the corresponding monomers. Thereby, changes going from monomeric to polymeric systems could be detected in fluorescence quantum yields and lifetimes pointing to energy trapping, e.g., energy transfer. Donor–acceptor copolymers containing different numbers of monomeric units within the side chain exhibit differences in the emission spectra, indicating that energy trapping in polymers is very sensitive to structural properties such as the chain length. UV–vis absorption spectroscopy as well as time‐resolved lifetime studies indicate intrapolymer and interpolymer energy transfer. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 相似文献
148.
Riccardo Gatto Benjamin Baumgartner 《Methodology and Computing in Applied Probability》2014,16(3):561-582
We analyze the insurer risk under the compound Poisson risk process perturbed by a Wiener process with infinite time horizon. In the first part of this article, we consider the capital required to have fixed probability of ruin as a measure of risk and then a coherent extension of it, analogous to the tail value at risk. We show how both measures of risk can be efficiently computed by the saddlepoint approximation. We also show how to compute the stabilities of these measures of risk with respect to variations of probability of ruin. In the second part of this article, we are interested in the computation of the probability of ruin due to claim and the probability of ruin due to oscillation. We suggest a computational method based on upper and lower bounds of the probability of ruin and we compare it to the saddlepoint and to the Fast Fourier transform methods. This alternative method can be used to evaluate the proposed measures of risk and their stabilities with heavy-tailed individual losses, where the saddlepoint approximation cannot be used. The numerical accuracy of all proposed methods is very high and therefore these measures of risk can be reliably used in actuarial risk analysis. 相似文献
149.
Bharat Kumar Ruth L. Viboh Margel C. Bonifacio William B. Thompson Jonathan C. Buttrick Babe C. Westlake Min‐Soo Kim Robert W. Zoellner Sergey A. Varganov Philipp Mrschel Jaroslav Teteruk Martin U. Schmidt Benjamin T. King 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2012,124(51):13071-13071
150.
Maria N. Tamaño‐Machiavello Benjamin Bracke Carlos M. Costa Senentxu Lanceros‐Mendez Roser Sabater i Serra José Luis Gómez Ribelles 《Journal of Polymer Science.Polymer Physics》2016,54(6):672-679
Polymer blend membranes have been obtained consisting of a hydrophilic and a hydrophobic polymers distributed in co‐continuous phases. In order to obtain stable membranes in aqueous environments, the hydrophilic phase is formed by a poly(hydrohyethyl acrylate), PHEA, network while the hydrophobic phase is formed by poly(vinylidene fluoride‐co‐trifluoroethylene) P(VDF‐TrFE). To obtain the composites, in a first stage, P(VDF‐TrFE) is blended with poly(ethylene oxyde) (PEO), the latter used as sacrificial porogen. P(VDF‐TrFE)/PEO blend membranes were prepared by solvent casting at 70°C followed by cooling to room temperature. Then PEO is removed from the membrane by immersion in water obtaining a P(VDF‐TrFE) porous membrane. After removing of the PEO polymer, a P(VDF‐TrFE) membrane results in which pores are collapsed. Nevertheless the pores reopen when a mixture of hydroxethyl acrylate (HEA) monomer, ethyleneglycol dimethacrylate (as crosslinker) and ethanol (as diluent) is absorbed in the membrane and subsequent polymerization yields hybrid hydrophilic/hydrophobic membranes with controlled porosity. The membranes are thus suitable for lithium‐ion battery separator membranes and/or biostable supports for cell culture in biomedical applications. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 672–679 相似文献