全文获取类型
收费全文 | 207篇 |
免费 | 3篇 |
国内免费 | 2篇 |
专业分类
化学 | 101篇 |
晶体学 | 1篇 |
力学 | 5篇 |
综合类 | 1篇 |
数学 | 68篇 |
物理学 | 36篇 |
出版年
2022年 | 1篇 |
2021年 | 2篇 |
2020年 | 2篇 |
2019年 | 9篇 |
2018年 | 7篇 |
2017年 | 9篇 |
2016年 | 6篇 |
2015年 | 3篇 |
2014年 | 5篇 |
2013年 | 26篇 |
2012年 | 15篇 |
2011年 | 14篇 |
2010年 | 7篇 |
2009年 | 18篇 |
2008年 | 11篇 |
2007年 | 8篇 |
2006年 | 11篇 |
2005年 | 9篇 |
2004年 | 7篇 |
2003年 | 6篇 |
2002年 | 3篇 |
2001年 | 5篇 |
2000年 | 1篇 |
1999年 | 3篇 |
1998年 | 1篇 |
1997年 | 4篇 |
1996年 | 3篇 |
1995年 | 3篇 |
1994年 | 3篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1989年 | 1篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1979年 | 2篇 |
排序方式: 共有212条查询结果,搜索用时 15 毫秒
111.
Efficient calculation of electrostatic interactions in colloidal systems is becoming more important with the advent of such probing techniques as atomic force microscopy. Such practice requires solving the nonlinear Poisson–Boltzmann equation (PBE). Unfortunately, explicit analytical solutions are available only for the weakly charged surfaces. Analysis of arbitrarily charged surfaces is possible only through cumbersome numerical computations. A compact analytical solution of the one-dimensional PBE is presented for two plates interacting in symmetrical electrolytes. The plates can have arbitrary surface potentials at infinite separation as long they have the same sign. Such a condition covers a majority of the colloidal systems encountered. The solution leads to a simple relationship which permits determination of surface potentials, surface charge densities, and electrostatic pressures as a function of plate separation H for different charging scenarios. An analytical expression is also presented for the potential profile between the plates for a given separation. Comparison of these potential profiles with those obtained by numerical analysis shows the validity of the proposed solution. 相似文献
112.
Abdullah Menzek Latif Kelebekli Aliye Altundaş Ertan Şahin Fatoş Polat 《Helvetica chimica acta》2008,91(12):2367-2378
The reaction of 1,4‐dihydro‐1,4‐epoxynaphthalene with cyclooctatetraene at 130±5° for 14 days gave the four products 2a,3,3a,4,9,9a,10,10a‐octahydro‐4,9‐epoxy‐3,10‐ethenocyclobuta[b]anthracene ( 13 ), 25‐oxanonacyclo[10.10.2.25,9.114,21.02,11.03,10.04,6.013,22.015,20]heptacosa‐7,15,17,19,23,26‐hexaene ( 14 ), 5,5a,6,6a,6b,6c,12a,12b,12c,13,13a,14‐dodecahydro‐5,14‐epoxy‐6,13‐ethenocycloocta[3′,4′]cyclobuta[1′,2′:3,4]cyclobuta[1,2‐b]anthracene ( 15 ) and bis‐adduct 16 . The structures of the products were determined by spectroscopic methods. It was observed that adduct 14 undergoes a Cope rearrangement. The Cope rearrangement of this adduct was investigated in the temperature range of ?85° to 100° by NMR spectroscopy. 相似文献
113.
In this study, homopolymers of polythiophene (PT), polyindole (PIN) and their composites and copolymers were synthesized by chemical polymerization and were characterized by FTIR and UV-spectroscopy, and conductivity measurements. The conductivities of polymers, composites and copolymers were measured by a conventional four probe method at room temperature and different temperatures. Among the products, PT-PIN copolymer which was synthesized at polythiophene conditions revealed the highest conductivity with a value of 0.28 S cm?1. The thermal properties of the samples were investigated by using thermogravimetric analyses, and it was found that they have quite good thermal stability. X-ray diffraction spectra showed that the amorphous nature of the polymers. Morphological properties of the polymers, composites and copolymers have been investigated by scanning electron microscopy. 相似文献
114.
Nazan akmak Polat Gzde Yaylal Bekir Tanay 《Mathematical Methods in the Applied Sciences》2019,42(16):5607-5614
All over the globe, soft set theory is a topic of interest for many authors working in diverse areas because of its rich potential for applications in several directions since the day it was defined by Molodtsov in 1999. Moreover, soft set theory is free from the difficulties where as other existing methods viz. probability theory, fuzzy set theory. Considering to these benefits, soft set theory has became very popular research area for many researchers. To contribute this research area, in this paper, we examine some properties on soft topological spaces such as neighborhood structure of a soft element and soft interior, soft closure, and soft cluster element and so on that are based on soft element definition that gives us a different perspective for development of soft set theory. Moreover, we give some examples to clarify our definitions. 相似文献
115.
Let G be an infinite locally finite connected graph. We study the reconstructibility of G in relation to the structure of its end set
. We prove that an infinite locally finite connected graph G is reconstructible if there exists a finite family (Ωi)0i (n2) of pairwise finitely separable subsets of
such that, for all x,y,x′,y′V(G) and every isomorphism f of G−{x,y} onto G−{x′,y′} there is a permutation π of {0,…,n−1} such that
for 0i<n. From this theorem we deduce, as particular consequences, that G is reconstructible if it satisfies one of the following properties: (i) G contains no end-respecting subdivision of the dyadic tree and has at least two ends of maximal order; (ii) the set of thick ends or the one of thin ends of G is finite and of cardinality greater than one. We also prove that if almost all vertices of G are cutvertices, then G is reconstructible if it contains a free end or if it has at least a vertex which is not a cutvertex. 相似文献
116.
It is shown that a quasi-median graph G without isometric infinite paths contains a Hamming graph (i.e., a cartesian product of complete graphs) which is invariant under any automorphism of G, and moreover if G has no infinite path, then any contraction of G into itself stabilizes a finite Hamming graph. 相似文献
117.
118.
p-CuIn0.7Ga0.3(Se(1?x)Tex)2 type thin films were synthesized by thermal evaporation method on Mo coated glass substrates. To obtain Al/CuIn0.7Ga0.3(Se(1?x)Tex)2/Mo Schottky diode structure for two compositions of x = 0.0 and 0.6, Al metal was evaporated on upper surface of CuIn0.7Ga0.3(Se(1?x)Tex)2 as a front contact. Al/p-CuIn0.7Ga0.3(Se(1?x)Tex)2/Mo structures were annealed temperature range from 150 °C to 300 °C for 10 min under vacuum. The electrical and dielectrical properties of Al/p-CuIn0.7Ga0.3(Se(1?x)Tex)2 (CIGSeTe) Schottky barrier diodes (SBD) have been investigated. Capacitance–Voltage (C–V) characteristics, Conductance–Voltage (G/w–V) characteristics and interface state density were studied in order to obtain electrical and dielectrical parameters. The effects of interface state density (Nss), series resistance (Rs), the dielectric constant (?′), dielectric loss (?″), dielectric loss tangent (tan δ), ac electrical conductivity (σac) and carrier doping densities were calculated from the C–V and G/w–V measurements and plotted as a function of annealing temperature. It was observed that the values of carrier doping density NA for annealing temperature at 150 °C decreased from 2.83 × 10+15 cm?3 to 2.87 × 10+14 cm?3 with increasing Te content from x = 0.0 to 0.6. The series resistance for x = 0.0 found to be between 10 and 75 Ω and between 50 and 230 Ω for x = 0.6 in the range of annealing temperature at 150–300 °C. 相似文献
119.
Semra Tepe Çam Canan Aydaş Birol Engin Ülkü Rabia Yüce Talat Aydın Mustafa Polat 《辐射效应与固体损伤》2013,168(6):410-420
Laurel leaf (Laurus nobilis L.) samples that originated from Turkey were analyzed by electron spin resonance (ESR) and thermoluminescence (TL) techniques before and after γ-irradiation. Unirradiated (control) laurel leaf samples exhibit a weak ESR singlet centered at g=2.0020. Besides this central signal were two weak satellite signals situated about 3 mT left and right to it in radiation-induced spectra. The dose–response curve of the radiation-induced ESR signal at g=2.0187 (the left satellite signal) was found to be described well by a power function. Variation of the left satellite ESR signal intensity of irradiated samples at room temperature with time in a long term showed that cellulosic free radicals responsible for the ESR spectrum of laurel leaves were not stable but detectable even after 100 days. Annealing studies at four different temperatures were used to determine the kinetic behavior and activation energy of the radiation-induced cellulosic free radicals responsible from the left satellite signal (g=2.0187) in laurel leaves. TL measurements of the polymineral dust isolated from the laurel leaf samples allowed distinguishing between irradiated and unirradiated samples. 相似文献
120.
Data collected for providing recommendations can be partitioned among different parties. Offering distributed data-based predictions is popular due to mutual advantages. It is almost impossible to present trustworthy referrals with decent accuracy from split data only. Meaningful outcomes can be drawn from adequate data. Those companies with distributed data might want to collaborate to produce accurate and dependable recommendations to their customers. However, they hesitate to work together or refuse to collaborate because of privacy, financial concerns, and legal issues. If privacy-preserving measures are provided, such data holders might decide to collaborate for better predictions. In this study, we investigate how to provide predictions based on vertically distributed data (VDD) among multiple parties without deeply jeopardizing their confidentiality. Users are first grouped into various clusters off-line using self-organizing map clustering while protecting the online vendors’ privacy. With privacy concerns, recommendations are produced based on partitioned data using a nearest neighbour prediction algorithm. We analyse our privacy-preserving scheme in terms of confidentiality and supplementary costs. Our analysis shows that our method offers recommendations without greatly exposing data holders’ privacy and causes negligible superfluous costs because of privacy concerns. To evaluate the scheme in terms of accuracy, we perform real-data-based experiments. Our experiment results demonstrate that the scheme is still able to provide truthful predictions. 相似文献