全文获取类型
收费全文 | 2217篇 |
免费 | 75篇 |
国内免费 | 16篇 |
专业分类
化学 | 1436篇 |
晶体学 | 6篇 |
力学 | 74篇 |
数学 | 237篇 |
物理学 | 555篇 |
出版年
2023年 | 8篇 |
2022年 | 44篇 |
2021年 | 29篇 |
2020年 | 31篇 |
2019年 | 39篇 |
2018年 | 24篇 |
2017年 | 34篇 |
2016年 | 86篇 |
2015年 | 41篇 |
2014年 | 70篇 |
2013年 | 130篇 |
2012年 | 119篇 |
2011年 | 113篇 |
2010年 | 74篇 |
2009年 | 68篇 |
2008年 | 128篇 |
2007年 | 103篇 |
2006年 | 86篇 |
2005年 | 85篇 |
2004年 | 93篇 |
2003年 | 87篇 |
2002年 | 80篇 |
2001年 | 55篇 |
2000年 | 63篇 |
1999年 | 45篇 |
1998年 | 18篇 |
1997年 | 23篇 |
1996年 | 42篇 |
1995年 | 57篇 |
1994年 | 46篇 |
1993年 | 49篇 |
1992年 | 49篇 |
1991年 | 23篇 |
1990年 | 30篇 |
1989年 | 19篇 |
1988年 | 17篇 |
1987年 | 21篇 |
1986年 | 22篇 |
1985年 | 23篇 |
1984年 | 25篇 |
1983年 | 10篇 |
1982年 | 19篇 |
1981年 | 16篇 |
1980年 | 8篇 |
1979年 | 11篇 |
1978年 | 8篇 |
1977年 | 5篇 |
1975年 | 6篇 |
1974年 | 5篇 |
1973年 | 7篇 |
排序方式: 共有2308条查询结果,搜索用时 11 毫秒
1.
2.
3.
Michael De Castro 《Tetrahedron letters》2004,45(34):6501-6504
2-Deoxy-2-iodo-glycosylamides have been prepared from a variety of protected d-glucals by their reaction with N-iodosuccinimide and amides. Benzyl protected 2-iodoamides, when treated with sodium hydride and 15-crown-5, gave stable C1 N-linked 2-glycooxazolines as the major products. Silyl protected 2-iodoamides afforded the C1 O-linked 2-glycooxazolines; presumably by the rearrangement of unstable N-acylaziridine intermediates. 相似文献
4.
Thorsten Brand Kyle Ratinac Jeffrey V. Castro Robert G. Gilbert 《Journal of polymer science. Part A, Polymer chemistry》2004,42(22):5706-5713
A method was developed for free‐radical polymerization in the confines of a hollow latex particle. Hollow particles were prepared via the dynamic swelling method from polystyrene seed and divinylbenzene and had hollows of 500–1000 nm. So that these hollow poly(divinylbenzene) particles could function as submicrometer reactors, the particles were filled with a monomer (N‐isopropylacrylamide) via the dispersion of the dried particles in the molten monomer. The monomer that was not contained in the hollows was removed by washing and gentle abrasion. Free‐radical polymerization was then initiated by γ radiolysis in the solid state. Transmission electron microscopy showed that poly(N‐isopropylacrylamide) formed in the hollow interior of the particles, which functioned as submicrometer reactors. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5706–5713, 2004 相似文献
5.
Detection of hepatocarcinoma in rats by integration of the fluorescence spectrum: Experimental model
J. C. Marcassa J. Ferreira S. Zucoloto O. de Castro e Silva Jr. L. G. Marcassa V. S. Bagnato 《Laser Physics》2006,16(5):827-832
The incorporation of spectroscopic techniques into diagnostic procedures may greatly improve the chances for precise diagnostics. One promising technique is fluorescence spectroscopy, which has recently been used to detect many different types of diseases. In this work, we use laser-induced tissue fluorescence to detect hepatocarcinoma in rats using excitation light at wavelengths of 443 and 532 nm. Hepatocarcinoma was induced chemically in Wistar rats. The collected fluorescence spectrum ranges from the excitation wavelength up to 850 nm. A mathematical procedure carried out on the spectrum determines a figure of merit value, which allows the detection of hepatocarcinoma. The figure of merit involves a procedure which evaluates the ratio between the backscattered excitation wavelength and the broad emission fluorescence band. We demonstrate that a normalization allowed by integration of the fluorescence spectra is a simple operation that may allow the detection of hepatocarcinoma. 相似文献
6.
Beginning with the most general fractal strings/sprays construction recently expounded in the book by Lapidus and Frankenhuysen, it is shown how the complexified extension of El Naschie's cantorian-fractal spacetime model belongs to a very special class of families of fractal strings/sprays whose scaling ratios are given by suitable pinary (pinary, p prime) powers of the Golden Mean. We then proceed to show why the logarithmic periodicity laws in Nature are direct physical consequences of the complex dimensions associated with these fractal strings/sprays. We proceed with a discussion on quasi-crystals with p-adic internal symmetries, von Neumann's Continuous Geometry, the role of wild topology in fractal strings/sprays, the Banach-Tarski paradox, tesselations of the hyperbolic plane, quark confinement and the Mersenne-prime hierarchy of bit-string physics in determining the fundamental physical constants in Nature. 相似文献
7.
8.
A systematic study of the efficiency of protons, Ni, Pd and Th as chemical modifiers for the determination of cadmium by electrothermal atomic absorption spectrometry (ETAAS) using fast temperature programs was made for platform atomization. A comparison was made in terms of the salt type, absorbance-time profiles and elimination of the sodium chloride interference. The results were adapted to develop a method for the ETAAS determination of cadmium in biological and environmental samples. The highest sensitivity to determine cadmium in biological and environmental samples was obtained using nickel (together with protons) as a chemical modifier. The accuracy of the method was tested by the determination of cadmium in different certified reference materials. The best detection limit and the characteristic mass of Cd were found to be 0.03 ng mL(-1) and 0.35 pg, respectively. 相似文献
9.
In this paper we approximate the solution of a linear initial-value problem, making use of a Schauder basis for certain Banach space associated with such a differential problem. In addition, we apply that results in order to calculate numerically the response from a structure modelled by a three degree-of-freedom mass–damper–spring system. 相似文献
10.
We report a rigorous theory to show the origin of the unexpected periodic behavior seen in the consecutive differences between prime numbers. We also check numerically our findings to ensure that they hold for finite sequences of primes, that would eventually appear in applications. Finally, our theory allows us to link with three different but important topics: the Hardy–Littlewood conjecture, the statistical mechanics of spin systems, and the celebrated Sierpinski fractal. 相似文献