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71.
Optically Active Lycopene Epoxides and Lycopene Glycols: Synthesis and Chiroptical Properties We present extensive spectral and chiroptical data on the pure and crystalline lycopene diepoxides 1–3 and glycols 4–9 . A first synthetic approach to 1–9 with (+)-malic acid as starting material afforded 30 as a complex mixture of isomers (Scheme 1). Pure stereoisomers 1–9 were obtained using the enantiomerically pure epoxygeraniol 31 as starting material (Scheme 2). Differentiation of the (5Z)-from the (all-E)-isomers by 1H-NMR and UV/VIS alone is very difficult. 相似文献
72.
Oligosaccharide and glycoprotein microarrays as tools in HIV glycobiology; glycan-dependent gp120/protein interactions. 总被引:11,自引:0,他引:11
Eddie W Adams Daniel M Ratner Heidi R Bokesch James B McMahon Barry R O'Keefe Peter H Seeberger 《Chemistry & biology》2004,11(6):875-881
Defining HIV envelope glycoprotein interactions with host factors or binding partners advances our understanding of the infectious process and provides a basis for the design of vaccines and agents that interfere with HIV entry. Here we employ carbohydrate and glycoprotein microarrays to analyze glycan-dependent gp120-protein interactions. In concert with new linking chemistries and synthetic methods, the carbohydrate arrays combine the advantages of microarray technology with the flexibility and precision afforded by organic synthesis. With these microarrays, we individually and competitively determined the binding profiles of five gp120 binding proteins, established the carbohydrate structural requirements for these interactions, and identified a potential strategy for HIV vaccine development. 相似文献
73.
Exploring the physical,chemical and thermal characteristics of a new potentially insensitive high explosive RX-55-AE-5 总被引:1,自引:0,他引:1
R. K. Weese A. K. Burnham Heidi C. Turner T. D. Tran 《Journal of Thermal Analysis and Calorimetry》2007,89(2):465-473
Current work at Lawrence Livermore National Laboratory (LLNL) includes both understanding properties of old explosives and
measuring properties of new ones. The necessity to know and understand the properties of energetic materials is driven by
the need to improve performance and enhance stability to various stimuli, such as thermal, friction and impact insult.
This paper will concentrate on the physical properties of RX-55-AE-5, which is formulated from heterocyclic explosive, 2,6-diamino-3,5-dinitropyrazine-1-oxide,
LLM-105, and 2.5% Viton A. Differential scanning calorimetry (DSC) was used to measure a specific heat capacity, C
p, of≈0.950 J g−1 °C−1, and a thermal conductivity, κ, of≈0.475 W m−1 °C−1. The LLNL kinetics modeling code Kinetics05 and the Advanced Kinetics and Technology Solutions (AKTS) code thermokinetics
were both used to calculate Arrhenius kinetics for decomposition of LLM-105. Both obtained an activation energy barrier E≈180 kJ mol−1 for mass loss in an open pan. Thermal mechanical analysis, TMA, was used to measure the coefficient of thermal expansion
(CTE). The CTE for this formulation was calculated to be ≈61 μm m−1 °C−1. Impact, spark, friction are also reported. 相似文献
74.
Chakraborty S Wadas TJ Hester H Flaschenreim C Schmehl R Eisenberg R 《Inorganic chemistry》2005,44(18):6284-6293
A new terpyridyl-containing Pt triad [Pt(pytpy)(p-CC-C6H4-NH-CO-C6H2(OMe)3)](PF6)2 (4), where pytpy = 4'-(4-pyridin-1-ylmethylphenyl)-[2,2';6',2' ']terpyridine and p-CC-C6H4-NH-CO-C6H2(OMe)3 = N-(4-ethynylphenyl)-3,4,5-trimethoxybenzamide, has been synthesized and structurally characterized. The related donor-chromophore dyad [Pt(ttpy)(p-CC-C6H4-NH-CO-C6H2(OMe)3)]PF6 2, where ttpy = 4'-p-tolyl-[2,2';6',2' ']terpyridine, and the chromophore-acceptor dyad [Pt(pytpy)(CCC6H5)](PF6)2 (3), where CCC6H5 = ethynylbenzene, have also been studied. The multistep syntheses culminate with a CuI-catalyzed coupling reaction of the respective acetylene with either [Pt(ttpy)Cl]PF6 or [Pt(pytpy)Cl](PF6)2. X-ray and spectroscopic studies support assignment of a distorted square planar environment around the Pt(II) ion with three of its coordination sites occupied by the terpyridyl N-donors and the fourth coordination site occupied by the acetylenic carbon. Although the parent compound [Pt(ttpy)(CCC6H5)]PF6 (1) is brightly luminescent in fluid solution at 298 K, dyad 2 as well as triad 4 exhibit complete quenching of the emission. The chromophore-acceptor (C-A) dyad 3 displays weak solution luminescence at room temperature with a phi(rel)(em) of 0.011 (using Ru(bpy)3(2+) as a standard with phi(rel)(em) = 0.062). Electrochemically, the donor-chromophore (D-C) dyad and the donor-chromophore-acceptor (D-C-A) triad exhibit both metal-based and donor ligand-based oxidations, whereas the triad and the C-A dyad show the expected pyridinium- and terpyridine-based reductions. Transient absorption studies of the dyad and triad systems indicate that although the trimethoxybenzene group acts as a reductive donor, in the present system, the pyridinium group fails to act as an acceptor. 相似文献
75.
[reaction: see text] A convergent Group 4 metal-mediated coupling process is described for the synthesis of polypropionate-derived (E,E)-1,3-dienes. Both the stereochemistry of the internal alkyne and the presence/absence of a tethered alkoxide on this pi-component were found to play critical roles in dictating the regiochemical course of these reactions. 相似文献
76.
Using a relative rate method, rate constants have been measured at 296 ± 2 K for the gas‐phase reactions of OH radicals with 1,2‐butanediol, 2,3‐butanediol, 1,3‐butanediol, and 2‐methyl‐2,4‐pentanediol, with rate constants (in units of 10?12 cm3 molecule?1 s?1) of 27.0 ± 5.6, 23.6 ± 6.3, 33.2 ± 6.8, and 27.7 ± 6.1, respectively, where the error limits include the estimated overall uncertainty of ±20% in the rate constant for the reference compound. Gas chromatographic analyses showed the formation of 1‐hydroxy‐2‐butanone from 1,2‐butanediol, 3‐hydroxy‐2‐butanone from 2,3‐butanediol, 1‐hydroxy‐3‐butanone from 1,3‐butanediol, and 4‐hydroxy‐4‐methyl‐2‐pentanone from 2‐methyl‐2,4‐pentanediol, with formation yields of 0.66 ± 0.11, 0.89 ± 0.09, 0.50 ± 0.09, and 0.47 ± 0.09, respectively, where the indicated errors are the estimated overall uncertainties. Pathways for the formation of these products are presented, together with a comparison of the measured and estimated rate constants and product yields. © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 33: 310–316, 2001 相似文献
77.
Rayón-López Nelly Martínez-Casillas Diana C. Miranda-Hernández Margarita Villafán-Vidales Heidi I. Rodríguez-López J. Luis Menchaca-Campos E. Carmina Cuentas-Gallegos A. Karina 《Journal of Solid State Electrochemistry》2019,23(3):707-716
Journal of Solid State Electrochemistry - High-crystalline tungsten trioxides (WO3) have been synthesized by an environmentally friendly method using concentrated solar energy. The obtained... 相似文献
78.
Dr. Daniela Hermann Dr. Heidi A. Schwartz Melanie Werker Prof. Dr. Dominik Schaniel Prof. Dr. Uwe Ruschewitz 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(14):3606-3616
Fifteen new photochromic hybrid materials were synthesized by gas phase loading of fluorinated azobenzenes, namely ortho-tetrafluoroazobenzene (tF-AZB), 4H,4H′-octafluoroazobenzene (oF-AZB), and perfluoroazobenzene (pF-AZB), into the pores of the well-known metal-organic frameworks MOF-5, MIL-53(Al), MIL-53(Ga), MIL-68(Ga), and MIL-68(In). Their composition was analysed by elemental (CHNS) and DSC/TGA. For pF-AZB0.34@MIL-53(Al), a structural model based on high-resolution synchrotron powder diffraction data was developed and the host-guest and guest-guest interactions were elucidated from this model. These interactions of O−H⋅⋅⋅F and π⋅⋅⋅π type were confirmed by significant shifts of the O−H frequencies in loaded and unloaded MOFs of the MIL-53 and MIL-68 series. Most remarkably, all of the synthesized F-AZB@MOF systems can be switched with visible light, and some of them show almost quantitative (>95 %) photo-isomerization between its E and Z forms with no significant fatigue after repeated switching cycles. 相似文献
79.
Rasmussen Jakob G. Christensen Heidi S. 《Methodology and Computing in Applied Probability》2021,23(2):647-667
Methodology and Computing in Applied Probability - In this paper we consider point processes specified on directed linear networks, i.e. linear networks with associated directions. We adapt the... 相似文献
80.