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排序方式: 共有197条查询结果,搜索用时 15 毫秒
141.
A novel tetra-iron thiolate carbonyl assembly is described in which two dithiolate tetracarbonyl di-iron centres with a 'butterfly' configuration of the {2Fe3S}-cores are fused by two bridging thiolates which form a central planar 2Fe2S unit and comprise the first example of a chain of four metal-metal bonded iron atoms supported by a bridging sulfur framework; the assembly electrocatalyses hydrogen evolution. 相似文献
142.
Rodrigo A. Mancilla Cedric Little Alejandro Amoroso 《Applied biochemistry and biotechnology》2018,185(2):494-506
Low solubility of sterols in aqueous media limits efficient steroid production mediated by biocatalytic microorganisms such as Mycobacterium. Sterol emulsion technologies have been developed with low success rates, largely due to the complexity of generating stable and bioavailable particles. In this study, several aqueous dispersions of sterols in-water of different particle sizes were bioconverted to 4-androstene-3,17-dione (AD) in a solvent-free environment, using a classic microorganism Mycobacterium sp. B3805 as a model system. According to our results, the high concentration (20 g/L) phytosterol dispersions with the smallest particle size tested (370 nm) achieved up to 54% (7.4 g/L) AD production yield in 11 days. Moreover, the use of 0.1 biomass/sterols ratio in a complex bioconversion media containing yeast extract, and a 1:1 glucose/microdispersion ratio in the presence of the surfactant DK-Ester P-160 (HLB16), allowed homogenization and increased microdispersion stability, thus achieving the best results using emulsion technologies to date. 相似文献
143.
Vitamin D sufficiency is required for optimal health, and solar ultraviolet B (UVB) irradiance is an important source of vitamin D. UVB and/or vitamin D have been found in observational studies to be associated with reduced risk for over a dozen forms of cancer, multiple sclerosis, osteoporotic fractures, and several other diseases. On the other hand, excess UV irradiance is associated with adverse health outcomes such as cataracts, melanoma, and nonmelanoma skin cancer. Ecologic analyses are used to estimate the fraction of cancer mortality, multiple sclerosis prevalence, and cataract formation that can be prevented or delayed. Estimates from the literature are used for other diseases attributed to excess UV irradiation, additional cancer estimates, and osteoporotic fractures. These results are used to estimate the economic burdens of insufficient UVB irradiation and vitamin D insufficiency as well as excess UV irradiation in the United States for these diseases and conditions. We estimate that 50,000-63,000 individuals in the United States and 19,000-25,000 in the UK die prematurely from cancer annually due to insufficient vitamin D. The U.S. economic burden due to vitamin D insufficiency from inadequate exposure to solar UVB irradiance, diet, and supplements was estimated at $40-56 billion in 2004, whereas the economic burden for excess UV irradiance was estimated at $6-7 billion. These results suggest that increased vitamin D through UVB irradiance, fortification of food, and supplementation could reduce the health care burden in the United States, UK, and elsewhere. Further research is required to confirm these estimates. 相似文献
144.
Herpin TF Morton GC Dunn AK Fillon C Menard PR Tang SY Salvino JM Labaudinière RF 《Molecular diversity》1998,4(4):221-232
A Lead Discovery Library ofpiperazine-2-carboxamide derivatives was produced forgeneral screening. This paper discloses two novelsolid phase synthetic routes used to produce 15 000single compounds via the Irori directed sortingtechnique. Computational methods such as reagentclustering and library profiling were used to maximizereagent diversity and optimize pharmacokineticparameters. The results of a four center pharmacophoreanalysis revealed the added diversity gained by usingtwo independent synthetic routes. 相似文献
145.
Rinnert E Carteret C Humbert B Fragneto-Cusani G Ramsay JD Delville A Robert JL Bihannic I Pelletier M Michot LJ 《The journal of physical chemistry. B》2005,109(49):23745-23759
The interaction of water with a synthetic saponite clay sample, with a layer charge of 1 per unit cell (0.165 C m(-2)), was investigated by following along water adsorption and desorption in the relative pressure range from 10(-6) to 0.99 (i) the adsorbed amount by gravimetric and near-infrared techniques, (ii) the basal distance and arrangement of water molecules in the interlayer by X-ray and neutron diffraction under controlled water pressure, and (iii) the molecular structure and interaction of adsorbed water molecules by near-infrared (NIR) and Raman spectroscopy under controlled water pressure. The results thus obtained were confronted with Grand Canonical Monte Carlo (GC/MC) simulations. Using such an approach, various well-distinct hydration ranges can be distinguished. In the two first ranges, at low water relative pressure, adsorption occurs on external surfaces only, with no swelling associated. The next range corresponds to the adsorption of water molecules around the interlayer cation without removing it from its position on top of the ditrigonal cavity of the tetrahedral layer and is associated with limited swelling. In the following range, the cation is displaced toward the mid-interlayer region. The interlamellar spacing thus reached, around 12.3 A, corresponds to what is classically referred to as a "one-layer hydrate," whereas no water layer is present in the interlayer region. The next hydration range corresponds to the filling of the interlayer at nearly constant spacing. This leads to the formation of a well-organized network of interlayer water molecules with significant interactions with the clay layer. The structure thus formed leads to a complete extinction of the d001 line in D2O neutron diffraction patterns that are correctly simulated by directly using the molecular configurations derived by GC/MC. The next range (0.50 < P/P0 < 0.80) corresponds to the final swelling of the structure to reach d spacing values of 15.2 A (usually referred to the "two-layer hydrate"). It is associated with the development of a network of liquidlike water molecules more structured than in bulk water. The final hydration range at high relative pressure mainly corresponds to the filling of pores between clay particles. 相似文献
146.
Bright ZR Luyeye CR Morton AS Sedenko M Landolt RG Bronzi MJ Bohovic KM Gonser MW Lapainis TE Hendrickson WH 《The Journal of organic chemistry》2005,70(2):684-687
With aqueous hypochlorite and a phase transfer catalyst, secondary alcohols undergo hitherto unreported free radical reactions that compete with and effectively limit traditional ketone syntheses. Product mixture profiles are determined by reactant ratios, organic cosolvent, and availability of oxygen to the system. Under argon, over half of substrate alcohols, PhCH(OH)R, are converted to benzaldehyde and free radical products through beta-scission of intermediate alkyl hypochlorites. Secondary alcohols with R containing three or more carbons also may undergo delta chlorination. 相似文献
147.
Benjamin Guieu Cedric Lecoutey Rmi Legay Audrey Davis Jana Sopkova de Oliveira Santos Cosimo Damiano Altomare Marco Catto Christophe Rochais Patrick Dallemagne 《Molecules (Basel, Switzerland)》2021,26(1)
Alzheimer’s disease (AD) is a multifactorial neurodegenerative disease towards which pleiotropic approach using Multi-Target Directed Ligands is nowadays recognized as probably convenient. Among the numerous targets which are today validated against AD, acetylcholinesterase (ACh) and Monoamine Oxidase-B (MAO-B) appear as particularly convincing, especially if displayed by a sole agent such as ladostigil, currently in clinical trial in AD. Considering these results, we wanted to take benefit of the structural analogy lying in donepezil (DPZ) and rasagiline, two indane derivatives marketed as AChE and MAO-B inhibitors, respectively, and to propose the synthesis and the preliminary in vitro biological characterization of a structural compromise between these two compounds, we called propargylaminodonepezil (PADPZ). The synthesis of racemic trans PADPZ was achieved and its biological evaluation established its inhibitory activities towards both (h)AChE (IC50 = 0.4 µM) and (h)MAO-B (IC50 = 6.4 µM). 相似文献
148.
Using an image rectification application arising in the field of forest management, we demonstrate in this paper the practical
feasibility of applying thin plate spline (TPS) techniques to real image warping problems. The use of TPS‐based warping in
large problems can be limited by two factors: numerical instability in the calculation of TPS coefficients, and the intensive
computation involved in evaluating TPS functions. Both drawbacks can be overcome by taking advantage of some recent advances
in the numerical analysis of radial basis functions. Here we relate our experience in applying some of this work to realize
successful TPS warping of large forestry images, and some graphical examples are given. Methods for automated control point
selection and editing are also presented, and a cross‐correlation technique for evaluating the effectiveness of the warps
is described. This experience has guided our development of an effective and efficient software package for control point
selection and TPS warping of digital images.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
149.
Cedric Dielemann Dominique Matt Peter G. Jones Holger Thnnessen 《Acta Crystallographica. Section C, Structural Chemistry》2003,59(5):o247-o249
The title compound, 25,26:27,28‐bis(methylenedioxy)pentacyclo[19.3.1.13,7.19,13.115,19]octacosa‐1(25)3,5,7(28),9,11,13(27),15,17,19(26),21,23‐dodecaene dichloromethane solvate, C30H24O4·CH2Cl2, possesses crystallographic twofold symmetry in both components. The calixarene shows a pinched cone conformation with an elliptical cavity, in which the guest dichloromethane solvent molecule is accommodated. The contact distance between guest and host (H⋯ring centroid = 2.44 Å) is extremely short. 相似文献