全文获取类型
收费全文 | 411篇 |
免费 | 17篇 |
国内免费 | 2篇 |
专业分类
化学 | 236篇 |
晶体学 | 2篇 |
力学 | 27篇 |
数学 | 64篇 |
物理学 | 101篇 |
出版年
2023年 | 5篇 |
2021年 | 4篇 |
2020年 | 4篇 |
2018年 | 13篇 |
2016年 | 9篇 |
2015年 | 9篇 |
2014年 | 6篇 |
2013年 | 21篇 |
2012年 | 11篇 |
2011年 | 26篇 |
2010年 | 10篇 |
2009年 | 7篇 |
2008年 | 28篇 |
2007年 | 13篇 |
2006年 | 21篇 |
2005年 | 11篇 |
2004年 | 19篇 |
2003年 | 12篇 |
2002年 | 16篇 |
2001年 | 8篇 |
2000年 | 7篇 |
1999年 | 7篇 |
1998年 | 6篇 |
1997年 | 6篇 |
1996年 | 5篇 |
1995年 | 9篇 |
1994年 | 6篇 |
1993年 | 13篇 |
1991年 | 3篇 |
1990年 | 5篇 |
1989年 | 5篇 |
1988年 | 4篇 |
1987年 | 5篇 |
1986年 | 5篇 |
1985年 | 8篇 |
1984年 | 3篇 |
1983年 | 4篇 |
1982年 | 7篇 |
1980年 | 6篇 |
1979年 | 6篇 |
1978年 | 3篇 |
1977年 | 6篇 |
1976年 | 4篇 |
1975年 | 6篇 |
1974年 | 3篇 |
1973年 | 4篇 |
1972年 | 4篇 |
1967年 | 5篇 |
1965年 | 2篇 |
1942年 | 2篇 |
排序方式: 共有430条查询结果,搜索用时 15 毫秒
11.
Graeme B Bolger Angela McCahill Stephen J Yarwood Michael R Steele Jim Warwicker Miles D Houslay 《BMC biochemistry》2002,3(1):24-11
Background
The cyclic AMP specific phosphodiesterase, PDE4D5 interacts with the β-propeller protein RACK1 to form a signaling scaffold complex in cells. Two-hybrid analysis of truncation and mutant constructs of the unique N-terminal region of the cAMP-specific phosphodiesterase, PDE4D5 were used to define a domain conferring interaction with the signaling scaffold protein, RACK1. 相似文献12.
Zhu TC Dimofte A Finlay JC Stripp D Busch T Miles J Whittington R Malkowicz SB Tochner Z Glatstein E Hahn SM 《Photochemistry and photobiology》2005,81(1):96-105
Characterization of the tissue light penetration in prostate photodynamic therapy (PDT) is important to plan the arrangement and weighting of light sources so that sufficient light fluence is delivered to the treatment volume. The optical properties (absorption [mu(a)], transport scattering [mu(s)'] and effective attenuation [mu(eff)] coefficients) of 13 patients with locally recurrent prostate cancer were measured in situ using interstitial isotropic detectors. Measurements were made at 732 nm before and after motexafin lutetium (MLu)-mediated PDT in four quadrants. Optical properties were derived by applying the diffusion theory to the fluence rates measured at several distances (0.5-5 cm) from a point source. mu(a) and mu(s)' varied between 0.07 and 1.62 cm(-1) (mean 0.37 +/- 0.24 cm(-1)) and 1.1 and 44 cm(-1) (mean 14 +/- 11 cm(-1)), respectively. mu(a) was proportional to the concentration of MLu measured by an ex vivo fluorescence assay. We have observed, on average, a reduction of the MLu concentration after PDT, presumably due to the PDT consumption of MLu. mu(eff) varied between 0.91 and 6.7 cm(-1) (mean 2.9 +/- 0.7 cm(-1)), corresponding to an optical penetration depth (delta = 1/micro(eff)) of 0.1-1.1 cm (mean 0.4 +/- 0.1 cm). The mean penetration depth at 732 nm in human prostate is at least two times smaller than that found in normal canine prostates, which can be explained by a four times increase of the mean value of mu(s)' in human prostates. The mean light fluence rate per unit source strength at 0.5 cm from a point source was 1.5 +/- 1.1 cm(-2), excluding situations when bleeding occurs. The total number of measurements was N = 121 for all mean quantities listed above. This study showed significant inter- and intraprostatic differences in the optical properties, suggesting that a real-time dosimetry measurement and feedback system for monitoring light fluences during treatment should be considered for future PDT studies. 相似文献
13.
Davies SG Díez D El Hammouni MM Garner AC Garrido NM Long MJ Morrison RM Smith AD Sweet MJ Withey JM 《Chemical communications (Cambridge, England)》2003,(19):2410-2411
Comparison of the kinetic and parallel kinetic resolutions of methyl (RS)-5-tert-butyl-cyclopentene-1-carboxylate allows for the efficient synthesis of both (1R,2S,5S)- and (1S,2R,5R)-enantiomers of methyl 2-amino-5-tert-butyl-cyclopentane-1-carboxylate. 相似文献
14.
M.R. Trantham C.C. Kuranz G. Malamud M.J. Grosskopf E.S. Myra R.P. Drake A.R. Miles H.-S. Park B.A. Remington 《High Energy Density Physics》2013,9(2):303-308
Future experiments at the National Ignition Facility will be able to generate diagnosable Rayleigh–Taylor instability growth in the presence of locally generated, high radiation fluxes. This interplay of radiative energy transfer and hydrodynamic instability is relevant to many astrophysical systems, such as core-collapse red supergiant supernovae. Previous simulations of high-energy-density Rayleigh–Taylor instabilities in the presence of a hot environment near a radiative shock demonstrate behavior that differs from that found in non-radiative cases. However, these simulations considered only 1D or single wavelength cases. Here we report simulations of an entire experimental system using the CRASH code. These simulations lead to modified predictions, attributed to the effects of radial energy losses. 相似文献
15.
As a result of a continuing study utilizing nitrogenous bases2–6, we now wish to report that the base 3-quinuclidinol (13) is useful for the cleavage of β-keto and vinylogous β-keto esters. 相似文献
16.
Willem Jespers Dr. Grégory Verdon Dr. Jhonny Azuaje Dr. Maria Majellaro Dr. Henrik Keränen Prof. Xerardo García-Mera Dr. Miles Congreve Dr. Francesca Deflorian Dr. Chris de Graaf Dr. Andrei Zhukov Dr. Andrew S. Doré Dr. Jonathan S. Mason Prof. Johan Åqvist Dr. Robert M. Cooke Prof. Eddy Sotelo Dr. Hugo Gutiérrez-de-Terán 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(38):16679-16686
We present a robust protocol based on iterations of free energy perturbation (FEP) calculations, chemical synthesis, biophysical mapping and X-ray crystallography to reveal the binding mode of an antagonist series to the A2A adenosine receptor (AR). Eight A2AAR binding site mutations from biophysical mapping experiments were initially analyzed with sidechain FEP simulations, performed on alternate binding modes. The results distinctively supported one binding mode, which was subsequently used to design new chromone derivatives. Their affinities for the A2AAR were experimentally determined and investigated through a cycle of ligand-FEP calculations, validating the binding orientation of the different chemical substituents proposed. Subsequent X-ray crystallography of the A2AAR with a low and a high affinity chromone derivative confirmed the predicted binding orientation. The new molecules and structures here reported were driven by free energy calculations, and provide new insights on antagonist binding to the A2AAR, an emerging target in immuno-oncology. 相似文献
17.
The attachment of particles to bubbles in solution is of fundamental importance to several industrial processes, most notably in the process of froth flotation. During this process hydrophobic particles attach to air bubbles in solution, which allows them to be separated as froth at the surface. The addition of chemicals can help to modulate these interactions to increase the yield of the minerals of interest. Over the past decade the atomic force microscope (AFM) has been adapted for use in studying the forces involved in the attachment of single particles to bubbles in the laboratory. This allows the measurement of actual DLVO (Derjaguin, Landau, Vervey and Overbeek) forces and adhesive contacts to be measured under different conditions. In addition contact angles may be calculated from features of force versus distance curves. It is the purpose of this article to illustrate how the colloid probe technique can be used to make single particle-bubble interactions and to summarise the current literature describing such experiments. 相似文献
18.
The phase transformation from the tetragonal to the hexagonal crystal modification in highly oriented lamellae of poly-butene-1 has been followed by transmission electron microscopy (TEM). It is found that the reaction-controlling step is the nucleation process. No lattice orientation relationship (besides the [001]-direction, which is parallel in both crystal modifications) exists between non-transformed and transformed crystals. The nucleation is strongly enhanced by thermal or external stresses. Crystal growth, nucleated by external stresses, was observed at temperatures as low as — 150°C. The molecular mechanisms of the transformation are discussed. 相似文献
19.
Akimov DA Fedotov AB Koroteev NI Naumov AN Sidorov-Biryukov DA Zheltikov AM Miles RB 《Optics letters》1999,24(7):478-480
An experimental technique based on coherent one-dimensional hyper-Raman-resonant four-wave mixing in broad cylindrically focused light beams has been developed for line-by-line imaging of spatial distribution of excited atoms in a low-temperature plasma of optical breakdown. The technique was applied to map excited lead atoms in a low-temperature laser-produced plasma. 相似文献
20.
Ultraviolet filtered Rayleigh scattering temperature measurements with a mercury filter 总被引:1,自引:0,他引:1
We report the development of ultraviolet filtered Rayleigh scattering as a diagnostic tool for measurements of gas properties. A frequency-tripled narrow-linewidth Ti:sapphire laser illuminates a sample, and Rayleigh scattered light is imaged through a mercury-vapor absorption filter. Working in the ultraviolet improves the signal-to-noise ratio compared with that previously obtained in the visible as the result of an enhanced scattering cross section as well as the nearly ideal properties of the mercury filter. Tuning the laser through the absorption notch of the filter is a means of probing the scattering line shape, which contains temperature information. Temperature measurements of air are shown to have uncertainties of less than 3%. 相似文献