全文获取类型
收费全文 | 3005篇 |
免费 | 69篇 |
国内免费 | 10篇 |
专业分类
化学 | 1809篇 |
晶体学 | 65篇 |
力学 | 104篇 |
数学 | 309篇 |
物理学 | 797篇 |
出版年
2022年 | 23篇 |
2021年 | 20篇 |
2020年 | 25篇 |
2019年 | 42篇 |
2018年 | 31篇 |
2017年 | 32篇 |
2016年 | 70篇 |
2015年 | 50篇 |
2014年 | 75篇 |
2013年 | 174篇 |
2012年 | 143篇 |
2011年 | 231篇 |
2010年 | 149篇 |
2009年 | 139篇 |
2008年 | 161篇 |
2007年 | 209篇 |
2006年 | 157篇 |
2005年 | 129篇 |
2004年 | 106篇 |
2003年 | 107篇 |
2002年 | 71篇 |
2001年 | 33篇 |
2000年 | 41篇 |
1999年 | 45篇 |
1998年 | 32篇 |
1997年 | 31篇 |
1996年 | 33篇 |
1995年 | 28篇 |
1994年 | 26篇 |
1993年 | 26篇 |
1992年 | 29篇 |
1991年 | 23篇 |
1990年 | 32篇 |
1989年 | 21篇 |
1988年 | 17篇 |
1987年 | 29篇 |
1986年 | 29篇 |
1985年 | 31篇 |
1984年 | 25篇 |
1983年 | 21篇 |
1982年 | 32篇 |
1981年 | 38篇 |
1980年 | 23篇 |
1979年 | 33篇 |
1978年 | 28篇 |
1976年 | 22篇 |
1975年 | 22篇 |
1974年 | 19篇 |
1973年 | 20篇 |
1972年 | 18篇 |
排序方式: 共有3084条查询结果,搜索用时 421 毫秒
51.
Armstrong TA Bettoni D Bharadwaj V Biino C Borreani G Broemmelsiek D Buzzo A Calabrese R Ceccucci A Cester R Church M Dalpiaz P Dalpiaz PF Dimitroyannis D Fabbri M Fast J Gianoli A Ginsburg CM Gollwitzer K Govi G Hahn A Hasan M Hsueh S Lewis R Luppi E Macrí M Majewska AM Mandelkern M Marchetto F Marinelli M Marques J Marsh W Martini M Masuzawa M Menichetti E Migliori A Mussa R Palestini S Pallavicini M Passaggio S Pastrone N Patrignani C Peoples J Petrucci F Pia MG Pordes S Rapidis P Ray R 《Physical review D: Particles and fields》1996,54(11):7067-7070
52.
53.
54.
The diffusion-limited reaction A+AA+B is studied in general dimension. The asymptotic decay of the system is found to depend nontrivially upon the initial concentration of A particles for certain ranges of the diffusion constant, backward reaction rate, and total concentration of particles. This nonequilibrium behavior is due to the formation of clusters centered about the initial A particles. A perturbative analysis ind=1 shows that the transition to the nonequilibrium dynamics is sharp and is quite similar to another previously studied reaction A+AA. Ford>1, a scaling argument is presented which describes the dependence of the asymptotic decay on the initial concentration of A particles and the equilibrium concentration for large backward reaction rates. Monte Carlo data are shown which confirm the analytic work ind=1, 2, and 3. 相似文献
55.
56.
Ray K Badugu R Lakowicz JR 《The journal of physical chemistry. C, Nanomaterials and interfaces》2007,111(19):7091-7097
Metal-Enhanced Fluorescence (MEF) has become an important method in biomedical sensing. In this paper, we present the distance-dependent MEF of sulforhodamine B (SRB) monolayer on silver island films (SIFs). SRB is electrostatically incorporated into the Langmuir-Blodgett (LB) layers of octadecylamine (ODA) deposited on glass and SIFs substrates. The distances between SRB and SIFs or glass surfaces are controlled by depositing a varied number of inert stearic acid (SA) spacer layers. SRB is incorporated into positively charged LB layers of ODA by immersing the ODA deposited substrates into aqueous solution of SRB. Dye incorporated ODA layers with 10 nm separation distance from the SIFs surface show maximum metal-enhanced fluorescence intensity; ~7-fold increase in intensity as compared to that from the glass surface. The corresponding enhancement factor is reduced with increasing or decreasing the probe distance from the SIFs surface. Additionally, SRB on SIF surfaces show reduced lifetimes. We observed the shortest lifetime from the SRB with 5 nm distance from the SIF surfaces and the lifetime increased consistently with increasing the distances between the fluorophore and the SIFs surface. These observed spectral changes, increase in fluorescence intensity and decreased fluorescence lifetimes, are in accordance with the expected effects due to near-field interactions between the silver nanoparticles and fluorophores. We have also analyzed the complex fluorescence heterogeneous decays on metallic nanostructured surfaces using continuous distributions of decay times. The decay-time distributions appear to be sensitive to the distance between the metal and fluorophore and represent the underlying heterogeneity of the samples. The present systematic study provides significant information on the effect of fluorophore distance on the metal-enhanced fluorescence phenomenon. 相似文献
57.
Radiationless transitions in lanthanide ions embedded in glassy and crystalline hosts have been briefly reviewed. The correlations
of multiphonon relaxation rates with energy gaps, vibrational frequencies, temperatures and electronic symmetries have been
discussed. The essence of various theories, such as Nth order methods, non-adiabatic Hamiltonian method, dynamic coupling
model has also been presented. 相似文献
58.
Prasain JK Moore R Hurst JS Barnes S van Kuijk FJ 《Journal of mass spectrometry : JMS》2005,40(7):916-923
Carotenoids have been implicated in protection of the eye from light-mediated photo-toxicity caused by free radicals. Under conditions of normal oxidative stress the carotenoids serve as protective antioxidants; however, when the oxidative stress exceeds the antioxidant capacity, carotenoids can be oxidized into numerous cleavage products. The determination and identification of oxidized carotenoids in biological samples remains a major challenge due to the small sample size and low stability of these compounds. We investigated the reaction of various zeaxanthin cleavage products with O-ethyl hydroxylamine to evaluate their levels in a biological sample. For this, a sensitive and specific electrospray tandem mass spectrometry (ESI-MS/MS) was developed, avoiding the classical lower sensitive and specific HPLC-UV and fluorescence absorption methods. Protonated molecules [M + H](+) of carotenoids upon collision-induced dissociation produced a number of structurally characteristic product ions. A series of complicated clusters of product ions differing in 14 (CH(2))and 26 (C(2)H(2))Da was characteristic of the polyene chain of intact carotenoids. All carotenoid ethyl oximes of zeaxanthin cleavage products were characterized by the losses of 60 and 61 Da in their MS/MS spectra. Through the application of the LC/MS/MS method, we identified two oxime derivatives of 3-hydroxy-beta-ionone and 3-hydroxy-14'-apocarotenal with protonated molecules at m/z 252 and m/z 370 respectively, in a human eye sample. 相似文献
59.
60.
Frost RL Erickson KL Carmody O Weier ML 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2005,61(4):749-754
A suite of torbernites and metatorbernites have been analysed by near-infrared spectroscopy. The spectra of torbernites and metatorbernites in the first HOH fundamental overtone are different and the spectra of torbernites of different origins in the 6000-7500 cm(-1) region vary. NIR spectroscopy provides a method of studying the hydration of cations in the interlayer of torbernite. NIR spectroscopy shows that the spectra of torbernites from different origins in the water HOH first fundamental overtone and combination regions are different. This difference implies the hydration of cations is different for torbernite minerals. The structural arrangement of the water molecules in the interlayer is sample dependent. The NIR spectra of metatorbernites are different from that of torbernites and a similarity of the spectra of metatorbernites suggests that the water structure in metatorbernites is similar. 相似文献