全文获取类型
收费全文 | 7472篇 |
免费 | 237篇 |
国内免费 | 36篇 |
专业分类
化学 | 5695篇 |
晶体学 | 80篇 |
力学 | 94篇 |
数学 | 390篇 |
物理学 | 1486篇 |
出版年
2022年 | 31篇 |
2021年 | 70篇 |
2020年 | 88篇 |
2019年 | 115篇 |
2018年 | 74篇 |
2017年 | 57篇 |
2016年 | 145篇 |
2015年 | 125篇 |
2014年 | 171篇 |
2013年 | 358篇 |
2012年 | 381篇 |
2011年 | 454篇 |
2010年 | 253篇 |
2009年 | 288篇 |
2008年 | 493篇 |
2007年 | 464篇 |
2006年 | 523篇 |
2005年 | 470篇 |
2004年 | 459篇 |
2003年 | 359篇 |
2002年 | 337篇 |
2001年 | 133篇 |
2000年 | 101篇 |
1999年 | 101篇 |
1998年 | 88篇 |
1997年 | 88篇 |
1996年 | 97篇 |
1995年 | 93篇 |
1994年 | 63篇 |
1993年 | 62篇 |
1992年 | 80篇 |
1991年 | 70篇 |
1990年 | 41篇 |
1989年 | 49篇 |
1988年 | 45篇 |
1987年 | 58篇 |
1986年 | 66篇 |
1985年 | 85篇 |
1984年 | 66篇 |
1983年 | 36篇 |
1982年 | 72篇 |
1981年 | 70篇 |
1980年 | 71篇 |
1979年 | 56篇 |
1978年 | 46篇 |
1977年 | 43篇 |
1976年 | 36篇 |
1975年 | 35篇 |
1974年 | 33篇 |
1973年 | 43篇 |
排序方式: 共有7745条查询结果,搜索用时 296 毫秒
11.
The electrode reaction of decamethylferrocene (DMFc) dissolved in a thin layer of a room-temperature molten salt (RTMS), 1-octyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (C8mimC1C1N) or 1-octyl-3-methylimidazolium bis(pentafluoroethylsulfonyl)imide (C8mimC2C2N), on a self-assembled monolayer-modified gold electrode is coupled with the ion transfer across the interface between the RTMS and the outer aqueous solution (W) to give a voltammogram whose shape resembles a voltammogram of a simple one-electron transfer process. The electroneutrality of the RTMS layer during the oxidation of DMFc to decamethylferricenium ion is maintained by the concomitant dissolution of C8mim+ ion from the RTMS phase to the W phase, and the reduction of decamethylferricenium ion to DMFc is accompanied by the transfer of either C1C1N- or C2C2N- from RTMS to W. The midpoint potential of the voltammogram varies with the concentration of the salt in the aqueous phase, C8mimCl or LiCnCnN (n = 1 or 2), in a Nernstian manner, showing that the phase-boundary potential between the RTMS and the W is controlled by the partition of these ions. Although the phase-boundary potential across the RTMS / W interface is Nernstian with respect to the ions common to both phases at the equilibrium, the polarization at the RTMS / W interface under current flow distorts the shape of the voltammograms, resulting in a wider peak separation in the voltammogram. 相似文献
12.
Takashi Yoshitake Ryuji Iizuka Kaoru Fujino Osamu Inoue Kenji Yamagata Hitoshi Nohta Masatoshi Yamaguchi 《Analytical sciences》2004,20(12):1687-1690
An improved high-performance liquid-chromatographic (HPLC) assay for the simultaneous determination of serotonin (5-HT) and 5-hydroxyindole-3-acetic acid (5-HIAA) in human urine is reported. Following the automated precolumn derivatization of urinary 5-HT and 5-HIAA with benzylamine, the derivatives are separated by isocratic elution on a reversed-phase C18 semi-microbore column, and are fluorometrically detected at an excitation wavelength of 345 nm and an emission wavelength of 480 nm. The detection limits of 5-HT and 5-HIAA are 7 and 5 nmol/l in urine (0.7 and 0.5 fmol/20-microl injection). The proposed automatic method permits a highly selective and sensitive determination of 5-HT and 5-HIAA in human urine without any sample purification. 相似文献
13.
14.
Linear and nonlinear optical properties of racemic (±)2-(α-methylbenzylamino)-5-nitropyridine ((±)MBANP) single crystals have been comprehensively investigated and compared with those of the enantiomorph (–)2-(α-methylbenzylamino)-5-nitropyridine ((–)MBANP) crystals. (±)MBANP crystal exhibits very high chemical and physical stability, but relatively small nonlinear optical coefficients (d31 = 6.8 pm/V, d32 = 4.7 pm/V, d33 = 0.84 pm/V). A comparison between the nonlinear optical coefficients of (±)MBANP and (–)MBANP demonstrates the validity of the oriented-gas model in molecular crystals that neglects all the contributions from intermolecular interaction. 相似文献
15.
16.
Hirohisa Yokota Kenji Kamoto Jun-ichi Igarashi Norihiko Mouri Yutaka Sasaki 《Optical Review》2002,9(1):9-12
A new configuration for an ASE reduction filter in EDFA repeaters for WDM optical transmission systems using optical fiber grating couplers (FGCs) was proposed and first demonstrated. The filtering characteristics of the proposed filter for amplified single wavelength signal and 2-channel WDM signals using EDFA were identified. It was found that the filter was effective to improve SNR in optical domain by reducing ASE noise. The required FGC characteristics for the filter were theoretically predicted under the condition that the total filter loss did not exceed 3 dB. More than 70% of drop efficiency was required in each FGC for the application of the proposed filter to an 8-channel WDM system using EDFA repeaters. 相似文献
17.
Optical trapping forces of polystyrene microspheres are analyzed both theoretically and experimentally, and comparisons are
made between the two. Discrepancies are mainly caused by straight-ray approximation for axial trapping, and by trapping-position
vertical displacement due to gravity for transverse trapping. 相似文献
18.
We study the inverse scattering problem for the nonlinear Schrödinger equation and for the nonlinear Klein–Gordon equation with the generalized Hartree type nonlinearity. We reconstruct the nonlinearity from knowledge of the scattering operator, which improves the known results. 相似文献
19.
20.
Two experiments were conducted to evaluate the equivalence of noise annoyance scales and questions recommended by Team 6 (Community Response to Noise) of ICBEN for English and Japanese, two strikingly different languages. The first experiment was conducted with bilingual subjects in order to test a key assumption of the method established by ICBEN Team 6 for the development of equivalent noise annoyance scales: subjects who speak different languages interpret the concept of “highest degree” of annoyance similarly. The results indicate that English- and Japanese-speaking subjects do interpret the “highest degree” similarly. The second experiment tested for effects of wording differences. English- and Japanese-speaking subjects were presented with noise annoyance questions of one of three format types. The first type was similar to the question format recommended by ICBEN Team 6. It focused on the degree to which a given noise would “bother, disturb, or annoy” the subject. The second asked subjects to evaluate the “bothersome, annoying, or disturbing” quality of the noise. The third asked how much the noise would “worry, irritate, or concern” the subject. No significant difference was found in responses to the three formats when subjects evaluated noise in laboratory conditions. 相似文献