全文获取类型
收费全文 | 400篇 |
免费 | 15篇 |
国内免费 | 2篇 |
专业分类
化学 | 241篇 |
力学 | 12篇 |
数学 | 64篇 |
物理学 | 40篇 |
无线电 | 60篇 |
出版年
2023年 | 5篇 |
2022年 | 6篇 |
2021年 | 9篇 |
2020年 | 10篇 |
2019年 | 13篇 |
2018年 | 15篇 |
2017年 | 9篇 |
2016年 | 18篇 |
2015年 | 7篇 |
2014年 | 9篇 |
2013年 | 38篇 |
2012年 | 17篇 |
2011年 | 20篇 |
2010年 | 13篇 |
2009年 | 7篇 |
2008年 | 19篇 |
2007年 | 11篇 |
2006年 | 23篇 |
2005年 | 17篇 |
2004年 | 10篇 |
2003年 | 9篇 |
2002年 | 9篇 |
2001年 | 7篇 |
2000年 | 6篇 |
1999年 | 5篇 |
1998年 | 2篇 |
1997年 | 4篇 |
1995年 | 9篇 |
1994年 | 5篇 |
1993年 | 5篇 |
1992年 | 10篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1989年 | 8篇 |
1988年 | 6篇 |
1987年 | 5篇 |
1986年 | 2篇 |
1983年 | 2篇 |
1982年 | 4篇 |
1981年 | 5篇 |
1980年 | 6篇 |
1979年 | 4篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1976年 | 4篇 |
1970年 | 2篇 |
1963年 | 1篇 |
1959年 | 2篇 |
1937年 | 1篇 |
1935年 | 1篇 |
排序方式: 共有417条查询结果,搜索用时 156 毫秒
111.
The current work focuses on presenting specific Hall cells with high performance, and their corresponding parameters. The design, integration, measurements and model development for their performance assessment are necessary stages considered in the generation of the Hall cells. Experimental results regarding the Hall cells absolute sensitivity, offset and offset temperature drift are provided for two particular structures exhibiting the best behavior in terms of maximum sensitivity and lowest offset. Three-dimensional physical simulations were performed for the structures and the Hall mobility was extracted. Representation of the inverse of the geometrical correction factor for the Greek-cross Hall cell is also provided. 相似文献
112.
Mohammed A. Al-Nuri Mohammed A. Hannoun Nidal A. Zatar Maher A. Abu-Eid Waheed J. Al-Jondi Ahmad I. Hussein 《光谱学快报》2013,46(4):409-416
A new method for isolation and spectrophotometric determination of plumbagin is presented. Plumbagin was isolated by thin layer chromatography (TLC) and column chromatography (CC) techniques, as an orange tinged yellow long crystalline substances. Plumbagin exhibits two absrop-tion maxima at 410 and 510 nm. Stability of the color, pKa value, and the effect of pH were studied. Beer's law is obeyed over the range 0.9-45 ppm. The method is applied to the determination of plumbagin in roots, stems, and leaves of Plumbago europaea L. plant. 相似文献
113.
P Rodrigues Hoyne L M Benson T D Veenstra L J Maher S Naylor 《Rapid communications in mass spectrometry : RCM》2001,15(17):1539-1547
Electrospray ionization mass spectrometry is playing an increasing role in the study of noncovalent interactions involving biomolecules. RNA-RNA complexes are important in many areas of biology, including RNA catalysis, RNA splicing, ribosome function, and gene regulation. Here, microelectrospray mass spectrometry (microESI-MS) is used to study noncovalent base-pairing interactions between RNA oligonucleotides, an area not previously explored by this technique. Using a set of complementary RNA oligonucleotides, we demonstrate the formation of the expected double-helical RNA complexes composed of three distinct oligonucleotides. The ability to study specific RNA noncovalent interactions by microESI-MS has the potential to provide a unique method by which to analyze and assign precise molecular masses to RNA-RNA complexes. 相似文献
114.
Sheila Mawaziny Salah Arafa Magdy F. Iskandar Maher Z. El-Subee 《Journal of polymer science. Part A, Polymer chemistry》1976,14(3):671-675
Electron spin resonance (ESR) spectra were observed at ?160°C and at room temperature for γ-irradiated poly-α-methylstyrene. The spectrum observed at room temperature has been attributed to the radical species while that at ?160°C results from the same radical and superposition of the spectrum due to the radical ?H2-C(CH3)(C6H5)-. The radicals which are stable at room temperature could be used to graft vinyl acetate. 相似文献
115.
Azilah Abdul-Rahman Angelo A. Amoroso Timothy N. Branston Amitava Das John P. Maher Jon A. McCleverty Michael D. Ward Andrzej Wlodarczyk 《Polyhedron》1997,16(24):1182-4362
The new diphenolato complexes [{Mo(NO){HB(dmpz)3}Cl}2Q] where dmpz = 3,5-dimethylpyrazolyl and Q = OC6H4(C6H4O (n = 1 or 2), OC6H4CR=CRC6H4O (R = H or Et), and OC6H4CH=CHC6H4CH=CHC6H4O have been prepared and their electrochemical properties (cyclic and differential pulse voltammetry) compared with previously reported analogues where Q = OC6H4O, OC6H4EC6H4O (E = SO2, CO and S), OC6H4 (CO)C6H4 C6H4(CO)C6H4O and 1,5- and 2,7-O2C10H6. The electrochemical interaction between the redox centres in the new complexes is very weak, in contrast to that in the 1,4-benzenediolato and naphthalendiolato species. The EPR spectra of the reduced mixed-valence species [{Mo(NO){HB(dmpz)3}Cl}2Q]− where Q = 1,3- and 1,4-OC6H4O and OC6H4SC6H4O shows that they are valence-trapped at room temperature, whereas those of the dianions [{Mo(NO){HB(dmpz)3}Cl}2Q]2− where Q = 1,4-OC6H4O, OC6H4EC6H4O (E = CO or S) and OC6H4CH=CHC6H4CH=CHC6H4O shows that the unpaired spins on each molybdenum centre are strongly correlated (J, the spin exchange integral AMo, the metal-hyperfine coupling constant). The electrochemical properties and the comproportionation constants for the reaction [{Mo(NO){HB(dmpz)3} Cl}2Q] + [{Mo(NO){HB(dmpz)3}Cl}O]2]2−2[{Mo(NO) {HB(dmpz)3}Cl}2Q]− where Q = diphenolato bridge, are compared with related compounds containing benzenediamido and dianilido bridges. 相似文献
116.
We propose a novel method that allows continuous repetition rate tuning of a self-seeded gain-switched Fabry-Perot laser without the need for change in cavity length. This is achieved by employing a linearly chirped fiber Bragg grating with a large dispersion parameter. The dispersed pulses overlap to produce a continuous-wave-like feedback into the gain-switched laser cavity. By using the proposed experimental setup, we demonstrate pulses portraying sidemode suppression ratios of at least 30 dB and widths of about 30 ps over the entire repetition rate tuning range of 2.5-10 GHz. 相似文献
117.
118.
In this paper we give a necessary and sufficient condition in terms of the Jacobi–Dunkl transform in order that a Jacobi–Dunkl
convolution of distributions is hypoelliptic. 相似文献
119.
We report the development of a new class of readily prepared chiral 4-(pyrrolidino)-pyridine catalysts capable of exploiting both van der Waals (pi) and H-bonding interactions, thus allowing remote chiral information to stereochemically control the kinetic resolution of sec-alcohols. 相似文献
120.
Maher Mili 《Journal of Theoretical Probability》2000,13(3):717-731
Let K be respectively the parabolic biangle and the triangle in
and
be a sequence in [0, +[ such that limp (p)=+. According to Koornwinder and Schwartz,(7) for each
there exist a convolution structure (*(p)) such that (K, *(p)) is a commutative hypergroup. Consider now a random walk
on (K, *(p)), assume that this random walk is stopped after j(p) steps. Then under certain conditions given below we prove that the random variables
on K admit a selective limit theorems. The proofs depend on limit relations between the characters of these hypergroups and Laguerre polynomials that we give in this work. 相似文献