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101.
Vinuth Mirle Madhukara Naik M. Karthik K. Bhojya Naik H. S. Hemakumar K. H. 《Research on Chemical Intermediates》2019,45(4):2357-2368
Research on Chemical Intermediates - Contamination of groundwater and soil by high levels of hexavalent chromium directly affects the environment and human health as a serious pollutant.... 相似文献
102.
Prabu Mani Sharat Devadas Tamilselvi Gurusamy Pitchiah Esakki Karthik Balu P. Ratheesh Kothandaraman Ramanujam Sukhendu Mandal 《化学:亚洲杂志》2019,14(24):4814-4818
Inspired by copper‐based oxygen reduction biocatalysts, we have studied the electrocatalytic behavior of a Cu‐based MOF (Cu‐BTT) for oxygen reduction reaction (ORR) in alkaline medium. This catalyst reduces the oxygen at the onset (Eonset) and half‐wave potential (E1/2) of 0. 940 V and 0.778 V, respectively. The high halfway potential supports the good activity of Cu‐BTT MOF. The high ORR catalytic activity can be interpreted by the presence of nitrogen‐rich ligand (tetrazole) and the generation of nascent copper(I) during the reaction. In addition to the excellent activity, Cu‐BTT MOF showed exceptional stability too, which was confirmed through chronoamperometry study, where current was unchanged up to 12 h. Further, the 4‐electrons transfer of ORR kinetics was confirmed by hydrodynamic voltammetry. The oxygen active center namely copper(I) generation during ORR has been understood by the reduction peak in cyclic voltammetry as well in the XPS analysis. 相似文献
103.
Karthik H. Shankar 《General Relativity and Gravitation》2017,49(2):33
Gravitational collapse singularities are undesirable, yet inevitable to a large extent in General Relativity. When matter satisfying null energy condition (NEC) collapses to the extent a closed trapped surface is formed, a singularity is inevitable according to Penrose’s singularity theorem. Since positive mass vacuum solutions are generally black holes with trapped surfaces inside the event horizon, matter cannot collapse to an arbitrarily small size without generating a singularity. However, in modified theories of gravity where positive mass vacuum solutions are naked singularities with no trapped surfaces, it is reasonable to expect that matter can collapse to an arbitrarily small size without generating a singularity. Here we examine this possibility in the context of a modified theory of gravity with torsion in an extra dimension. We study singularity-free static shell solutions to evaluate the validity of NEC on the shell. We find that with sufficiently high pressure, matter can be collapsed to arbitrarily small size without violating NEC and without producing a singularity. 相似文献
104.
Jiyue Chen Prof. Roberto J. Brea Dr. Alessandro Fracassi Christy J. Cho Adrian M. Wong Dr. Marta Salvador-Castell Prof. Sunil K. Sinha Prof. Itay Budin Prof. Neal K. Devaraj 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2024,136(1):e202311635
There has been increasing interest in methods to generate synthetic lipid membranes as key constituents of artificial cells or to develop new tools for remodeling membranes in living cells. However, the biosynthesis of phospholipids involves elaborate enzymatic pathways that are challenging to reconstitute in vitro. An alternative approach is to use chemical reactions to non-enzymatically generate natural or non-canonical phospholipids de novo. Previous reports have shown that synthetic lipid membranes can be formed in situ using various ligation chemistries, but these methods lack biocompatibility and/or suffer from slow kinetics at physiological pH. Thus, it would be valuable to develop chemoselective strategies for synthesizing phospholipids from water-soluble precursors that are compatible with synthetic or living cells Here, we demonstrate that amide-forming ligations between lipid precursors bearing hydroxylamines and α-ketoacids (KAs) or potassium acyltrifluoroborates (KATs) can be used to prepare non-canonical phospholipids at physiological pH conditions. The generated amide-linked phospholipids spontaneously self-assemble into cell-like micron-sized vesicles similar to natural phospholipid membranes. We show that lipid synthesis using KAT ligation proceeds extremely rapidly, and the high selectivity and biocompatibility of the approach facilitates the in situ synthesis of phospholipids and associated membranes in living cells. 相似文献
105.
Rigid porphyrin hosts that mimic the spatial arrangement of mandelate recognition motifs lead to stereoselective receptors and illustrate how subtle structural differences in host design have significant impact on guest recognition. The porphyrin hosts are obtained with minimal synthetic effort from readily available chiral amine precursors and are modular in design. The chiral recognition properties of the porphyrin-based hosts with chiral carboxylate-containing guests and chiral amines are described. UV/vis and 1H NMR spectroscopic results indicate some of these porphyrin hosts undergo an induced fit conformational change upon guest binding. 相似文献
106.
107.
We report the synthesis and characterization of polyphenylated fluorene derivatives and a ring cyclized product containing cyclopenta[def]triphenylene core. Polybromination on fluorene was achieved either by solid state reaction with bromine or utilizing Br2/KBrO3 in AcOH/H2SO4 mixture. The bromofluorenes were converted to the corresponding polyphenylated fluorenes by Suzuki coupling protocol. A hexabromofluorene underwent a multifold Suzuki coupling followed by C–H activation to produce a cyclopenta[def]triphenylene derivative. Fluorene ring showed a severe distortion from planarity beyond tetra-substitution which manifested in the optical properties. 相似文献
108.
Abstract–An extremely weak native light emission from rat liver nuclei was detected and studied using a highly sensitive single photon counting system. This emission is oxygen dependent and we attribute it to (per) oxidative processes. The effects of deuterium oxide and l,4-diazabicyclo-[2.2.2] octane on the light emission suggests the possible involvement of singlet oxygen. The kinetic features of the underlying reactions including biphasic response to both oxygen and temperature changes, could be clearly discerned. Further study of this light emission can serve as a useful adjunct to biochemical investigations of oxidative processes which play an important role in mutation, carcinogenesis and aging. 相似文献
109.
Intrinsic low level chemiluminescence of dark adapted intact leaves exhibits a transient enhancement of light emission when ambient air is replaced with an anaerobic atmosphere. Re establishing aerobic conditions gives rise to a complex kinetic behavior of the light emission in the post-anoxic phase. Metabolic changes within the leaf are suggested to be responsible for this phenom enon, where intactness of the leaf is found to be of crucial importance. Leaf homogenate showed nearly oxygen independent chemiluminescence. In contrast, low level chemiluminescence of UV-light damaged leaves and of chloroplast preparations was inhibited by oxygen depletion. Spectral analyses of the ultraweak light emission from the intact leaf indicates that in both aerobic and anaerobic cases, the source of the ultraweak light is the same. The similarity to the spectrum of delayed fluorescence also obtained from the leaf suggests that chlorophyll is the light emitting species. 相似文献
110.
Adéla?Zemanová Olga?Semenova Ale??Kroupa Jan?V?e?t’álEmail author Karthik?Chandrasekaran Klaus W.?Richter Herbert?Ipser 《Monatshefte für Chemie / Chemical Monthly》2005,136(11):1931-1937
Summary. Phase equilibria in the Ag–In–Pd system were determined at 700°C based on experimental results for 21 alloys. A ternary compound
T1 (with the approximate composition AgInPd2) was identified by XRD analysis. These data were compared with the results of a CALPHAD-type prediction, based on binary
thermodynamic data only and a symmetrical Redlich–Kister–Muggianu model. The experimental results will serve as a basis for refined thermodynamic modeling of the different phases in this
ternary system. 相似文献