全文获取类型
收费全文 | 3263篇 |
免费 | 104篇 |
国内免费 | 9篇 |
专业分类
化学 | 2144篇 |
晶体学 | 75篇 |
力学 | 90篇 |
数学 | 279篇 |
物理学 | 788篇 |
出版年
2024年 | 12篇 |
2023年 | 46篇 |
2022年 | 77篇 |
2021年 | 71篇 |
2020年 | 90篇 |
2019年 | 91篇 |
2018年 | 67篇 |
2017年 | 61篇 |
2016年 | 111篇 |
2015年 | 92篇 |
2014年 | 129篇 |
2013年 | 239篇 |
2012年 | 222篇 |
2011年 | 253篇 |
2010年 | 133篇 |
2009年 | 117篇 |
2008年 | 181篇 |
2007年 | 196篇 |
2006年 | 118篇 |
2005年 | 115篇 |
2004年 | 98篇 |
2003年 | 65篇 |
2002年 | 62篇 |
2001年 | 45篇 |
2000年 | 30篇 |
1999年 | 19篇 |
1998年 | 22篇 |
1997年 | 20篇 |
1996年 | 32篇 |
1995年 | 27篇 |
1994年 | 30篇 |
1993年 | 35篇 |
1992年 | 28篇 |
1990年 | 14篇 |
1989年 | 17篇 |
1988年 | 26篇 |
1987年 | 19篇 |
1986年 | 23篇 |
1985年 | 24篇 |
1984年 | 26篇 |
1983年 | 27篇 |
1982年 | 22篇 |
1981年 | 23篇 |
1980年 | 20篇 |
1979年 | 24篇 |
1978年 | 29篇 |
1977年 | 14篇 |
1976年 | 23篇 |
1974年 | 17篇 |
1973年 | 14篇 |
排序方式: 共有3376条查询结果,搜索用时 15 毫秒
31.
Laxman Singh Ravikant Sharma Narayan Singh Atendra Kumar Dev K Mahato Youngil Lee Mikhael Bechelany KD Mandal 《Progress in Crystal Growth and Characterization of Materials》2021,67(4):100542
This review paper covers the low temperature wet growth of nano-engineered particles of ZnO-based mixed metal oxides, their growth mechanism, and characterization using X-ray diffraction, SEM, TEM and IR, UV–visible, and XPS spectral techniques. Main focus of this article is centered on low temperature semi-wet methods of synthesis that are suitable for large scale production of zinc oxide-based systems mixed with iron oxide, copper oxide, nickel oxide and cobalt oxide. These mixed metal oxides have broad industrial applications as catalyst, semiconductors, adsorbents, superconductors, electro-ceramics, and antifungal agents in addition to extensive applications in medicines. This paper discusses the low-cost and environment friendly synthesis of these mixed metal oxides, measurement of properties and applicability of these materials systems. 相似文献
32.
The broadening as well as shift in the photoluminescence spectra of K2[Pt(CN)4] · 3 H2O, Ba[Pt(CN)4] · 4 H2O, CdS:Te and Ru(C15H11N3)2I2 · H2O crystals take place with their grinding. The original vibronic peaks at 632 and 628 nm of CdS:Te and Ru(C15H11N3)2I2 · H2O crystals, respectively, disappear with the grinding. A new vibronic peak at 650 nm appears with grinding of Ru(C15H11N3)2I2 · H2O crystals. It is concluded that the change in the photoluminescence spectra is attributed to the creation of dislocations during the process of grinding. 相似文献
33.
A new Ni4 distorted cubane complex [Ni4(μ3-OMe)4Q4(MeOH)4] (1) (where Q− is the anion of 8-quinolinol) is obtained from the reaction of NaQ with Ni(OAc)2 · 4H2O in refluxing MeOH via solvent derived μ3-OMe assisted self-assembly of four nickel(II) centres. The periphery of [Ni4(OMe)4] cubane is covered by four Q− and four MeOH molecules. This methanol specific reaction is not supported in solvent glycinol (Hgl; NH2(CH2)2OH), an amine substituted ethanol, producing monomeric [NiQ2(Hgl)2] · 2H2O (2 · 2H2O) instead and is able to cleave 1 to yield 2 · 2H2O. The cryomagnetic susceptibility data of powdered 1 can be modeled by a two J equation yielding J1 = −1.8(1) cm−1, J2 = 3.9(1) cm−1 and g = 2.24. 相似文献
34.
The present paper reports for the first time an exact analytic expression that can be used for obtaining fracture stress σF, when fracture occurs in the elastic limit and also when fracture occurs after general yield (σF > σY) in a brittle solid. The present paper may provide a new basis to fracture-safe design of brittle materials. 相似文献
35.
36.
Thin film capacitors of CeO2 were fabricated by thermal evaporation. The dielectric properties of these films were studied in the frequency range 0.05–16 KHz at various temperatures, starting from liquid nitrogen temperature to 390 K. The effect of annealing on capacitance and tan δ were studied for different frequencies. The behaviour was explained on the basis of relief in strain energy. The plot between current density and temperature was drawn, and from the slope of the plot the activation energy was calculated and found to be 0.52 ev. The results were discussed. 相似文献
37.
Cerium Oxide films were prepared by vacuum thermal evaporation from tantalum boat in a conventional vacuum coating unit. Current-voltage characteristics were studied for different film thicknesses. The breakdown voltage (VB) and dielectric field strength (EB) were calculated. It is found that the breakdown voltage increases and dielectric field strength decreases as the thickness of the film increases. The applicability of Forlani-Minnaja relation is discussed. Current-voltage characteristics were also drawn at different temperatures and breakdown voltages were calculated. The breakdown voltage decreases as the temperature of the structure increases but the variation is nonlinear. The variation of current density with temperature was studied and the activation energy for the migration of charge carriers was calculated and it is about 0.52 ev. The results were discussed. 相似文献
38.
Optical logic redux 总被引:1,自引:0,他引:1
Twenty years ago IBM physicist Robert Keyes published a paper entitled “Optical Logic—in the light of computer technology.” It caused an instant furor in the fledgling optical logic community. Now, 20 years after that devastating critique, the field of optical logic has grown enormously. There are literally thousands of papers. Many of them are collected in a bibliography given here. Was Keyes’ critique wrong? Have opticists simply ignored what Keyes pointed out? Have new developments made some of his remarks not quite so relevant? We argue here that
- •
- Keyes was and still is mostly correct, but that may change in a few years
- •
- Many researchers have indeed simply ignored what he said
- •
- New developments in both optical logic and its applications open niches for optical logic that Keyes did not (and probably could not) anticipate
- •
- New and anticipated developments in electronics may increase the role for optics
39.
In this article, we refine certain earlier existing bounds for Berezin number of operator matrices. We also prove some new Berezin number inequalities for general n × n operator matrices.Further, we establish several upper bounds for Berezin number and generalized Euclidean Berezin number for off-diagonal operator matrices. Finally, some interesting examples are discussed. 相似文献
40.
Slow light is demonstrated in liquid phase in an aqueous bacteriorhodopsin (bR) solution at room temperature. Group velocity as low as 3 m/s (all the way to c) is achieved by exploiting the photoisomerization property of bR for coherent population oscillations. Slow light in the liquid phase offers several advantages over solids or vapors for a variety of applications: (i) shorter lifetimes of the M state facilitate slow light at higher modulation frequencies, (ii) convection makes it possible to obtain large signal delays even at high input powers, and (iii) solution concentration is another convenient parameter to vary the signal delay over a wide range. 相似文献