全文获取类型
收费全文 | 438篇 |
免费 | 24篇 |
国内免费 | 1篇 |
专业分类
化学 | 355篇 |
晶体学 | 11篇 |
力学 | 4篇 |
数学 | 29篇 |
物理学 | 64篇 |
出版年
2024年 | 1篇 |
2022年 | 6篇 |
2021年 | 3篇 |
2020年 | 8篇 |
2019年 | 13篇 |
2018年 | 4篇 |
2017年 | 8篇 |
2016年 | 11篇 |
2015年 | 12篇 |
2014年 | 14篇 |
2013年 | 22篇 |
2012年 | 33篇 |
2011年 | 35篇 |
2010年 | 26篇 |
2009年 | 19篇 |
2008年 | 24篇 |
2007年 | 28篇 |
2006年 | 32篇 |
2005年 | 26篇 |
2004年 | 27篇 |
2003年 | 11篇 |
2002年 | 17篇 |
2001年 | 13篇 |
2000年 | 6篇 |
1999年 | 2篇 |
1998年 | 9篇 |
1997年 | 6篇 |
1996年 | 3篇 |
1995年 | 2篇 |
1994年 | 2篇 |
1993年 | 6篇 |
1992年 | 3篇 |
1991年 | 3篇 |
1990年 | 1篇 |
1989年 | 3篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1985年 | 1篇 |
1984年 | 3篇 |
1982年 | 4篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 2篇 |
1976年 | 1篇 |
1974年 | 2篇 |
1973年 | 1篇 |
1917年 | 1篇 |
1915年 | 1篇 |
排序方式: 共有463条查询结果,搜索用时 31 毫秒
131.
The addition reaction of the sodium α-sulfinyl carbanion of a racemic aryl dichloromethyl sulfoxide to (?)-menthone in the presence of boron trifluoride diethyl etherate gave an adduct as a mixture of two easily separable diastereomers. After separation of the diastereomers, they were each treated with sodium hydride to afford enantiomerically pure aryl dichloromethyl sulfoxides and (?)-menthone both in high yields. This procedure provides a simple and efficient method for the resolution of racemic aryl dichloromethyl sulfoxides. 相似文献
132.
133.
134.
Counterion binding in Na poly(acrylate) gel immersed in water/organic solvent [ethanol (EtOH), acetonitrile (AcN), or tetrahydrofuran (THF)] mixtures was investigated by 23Na‐NMR spectroscopy. With an increase in the content of an organic solvent (~40–50 vol %), the 23Na chemical shift significantly moved downfield on a gel collapse. This downfield shift strongly suggests that the gel collapse was induced by contact ion‐pair formation between the counterion and the carboxyl anion on the polymer. With a further increase in the solvent content (~90 vol %), the chemical shift for an EtOH system showed a slight upfield shift, while THF and AcN systems maintained downfield shifts. The contrasting behaviors for EtOH and the latter two solvent systems were interpreted as being caused by desolvation and resolvation of bound Na+ counterions because of deswelling and reswelling of the respective gels in the pertinent solvent concentration regions. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 4412–4420, 2004 相似文献
135.
Takeda Masuo Wang Junhu Nishimura Tatsuru Suzuki Katsuya Kitazawa Takafumi Takahashi Masashi 《Hyperfine Interactions》2004,156(1-4):359-364
Hyperfine Interactions - We have examined the 155Gd Mössbauer spectra at 12 K for 25 complexes having different coordination numbers and different ratios of coordinating oxygen to nitrogen... 相似文献
136.
In this paper, we report the development of a novel unipolar charger for nanoparticles, a system that achieves low particle
loss and high charging efficiency without the use of sheath air. The efficient unipolar charging of the system is realized
mainly by the surface-discharge microplasma unit, a device previously applied with good success to the neutralization or charging
of submicron particles [Kwon et al., 2005, Aerosol Sci. Technol., 39, 987–1001; 2006, J. Aerosol Sci., 37, 483–499]. The unipolar
charger generates unipolar ions using the surface discharge of a single electrode with a DC pulse supply. This marks an advance
from our previous method of generating bipolar ions with the use of dual electrodes in earlier studies. We evaluated the efficiency
of the penetration (or loss) and charging of nanoparticles in the size range of 3–15 nm, then compared the charging efficiencies
measured with those predicted by diffusion charging theory. More than 90% of inlet nanoparticles penetrated the charger (less
than 10% of the particle were lost) without the use of sheath air. Other chargers have only realized this high penetration
efficiency by relying on sheath air flow. Moreover, the measured charging efficiencies agreed well with those predicted by
diffusion charging theory and were somewhat higher and more size-dependent than the charging efficiencies of other nanoparticle
chargers. 相似文献
137.
We have built a single-frequency Nd:YAG laser capable of producing an output power of 101 W by injection locking a slave laser that can emit an output power of 121 W in the free-running state to a 2-W master laser. We confirmed that the output mode was diffraction limited and linearly polarized. 相似文献
138.
Kojima Y Fujita T Ona EP Matsuda H Koda S Tanahashi N Asakura Y 《Ultrasonics sonochemistry》2005,12(5):359-365
Sonochemical degradation of MCPA ((4-chloro-2-methylphenoxy) acetic acid) in dilute aqueous solutions was studied using ultrasound with a frequency of 500 kHz. The effect of gas atmosphere on MCPA degradation was investigated in nitrogen (N(2)), air (O(2)/N(2)), oxygen (O(2)), argon (Ar) and Ar/O(2) (60/40% v/v) atmospheres. For sonochemical degradation of MCPA in N(2), air (O(2)/N(2)), O(2) and Ar atmospheres, the rate enhancement of MCPA decomposition by sonolysis was found to be more effective in an O(2)-enriched atmosphere compared to Ar atmosphere. It was considered that a higher amount of oxidants was formed in a higher O(2) partial pressure, which accelerated MCPA decomposition in a radical reaction system. On the other hand, both dechlorination and total organic carbon (TOC) removal rates were higher in Ar atmosphere, compared to those in O(2)/N(2) atmosphere. It was found that, MCPA was most effectively decomposed by sonication in Ar/O(2) (60/40% v/v) atmosphere, with higher rates of decomposition, dechlorination and TOC removal. 相似文献
139.
Takiue T Murakami D Tamura T Sakamoto H Matsubara H Aratono M 《The journal of physical chemistry. B》2005,109(29):14154-14159
The interfacial tensions (gamma) of the hexane solutions of 1H,1H-perfluorononanol (FDFC9OH) and its omega-hydrogenated analogue 1H,1H,9H-perfluorononanol (HDFC9OH) against water were measured as a function of temperature and concentration under atmospheric pressure in order to know the effect of omega-dipoles on the adsorption behavior of fluorononanols. The interfacial pressure (pi) versus mean area per adsorbed molecule (A) curves consist of two discontinuous changes among three different states: the gaseous, expanded, and condensed states. The A values at given pi in the gaseous and expanded states are larger for HDFC9OH than for FDFC9OH. The changes in partial molar entropy (s1(H) - s1(O)) and energy (u1(H) - u1(O)) of adsorption were evaluated. Their values are negative, and therefore, the alcohols have a smaller entropy and energy at the interface than in the bulk solution. Furthermore, the u1(H) - u1(O) value is more negative for HDFC9OH than for FDFC9OH in the expanded state and also in the condensed film just above the expanded-condensed phase transition point. This seems to be due to the following: (1) HDFC9OH may tilt from interface normal for omega-dipoles to interact effectively with water molecules in the interfacial region and to reduce their own repulsive interaction between neighbors arranging parallel in the adsorbed film. This leads to a lower value for HDFC9OH than for FDFC9OH. (2) The contact of omega-dipoles with hexane molecules in the bulk solution is energetically unfavorable, and thus, the u1(O) value of HDFC9OH is expected to be larger than that of FDFC9OH. 相似文献
140.