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941.
Finazzo C Calle C Stoll S Van Doorslaer S Schweiger A 《Physical chemistry chemical physics : PCCP》2006,8(16):1942-1953
The effect of the electron withdrawing or donating character of groups located at the periphery of the phthalocyanine ligand, as well as the influence of polar and nonpolar solvents are of importance for the redox chemistry of metal phthalocyanines. Continuous wave and pulse electron paramagnetic resonance and pulse electron nuclear double resonance spectroscopy at X- and Q-band are applied to investigate the electronic structure of the complexes Cu(II)phthalocyanine (CuPc), copper(II) 2,9,16,23-tetra-tert-butyl-29H,31H-phthalocyanine (CuPc(t)), and copper(II) 1,2,3,4,8,9,10,11,15,16,17,18,22,23,24,25-hexadecafluoro-29H,31H-phthalocyanine (CuPc(F)) in various matrices. Isotope substitutions are used to determine the g values, the copper hyperfine couplings and the hyperfine interactions with the 14N, 1H and 19F nuclei of the macrocycle and the surrounding matrix molecules. Simulations and interpretations of the spectra are shown and discussed, and a qualitative analysis of the data using previous theoretical models is given. Density functional computations facilitate the interpretation of the EPR parameters. The experimental g, copper and nitrogen hyperfine and nuclear quadrupole values are found to be sensitive to changes of the solvent and the structure of the macrocycle. To elucidate the electronic, structural and bonding properties the changes in the g principal values are related to data from UV/Vis spectroscopy and to density functional theory (DFT) computations. The analysis of the EPR data indicates that the in-plane metal-ligand sigma bonding is more covalent for CuPc(t) in toluene than in sulfuric acid. Furthermore, the out-of-plane pi bonding is found to be less covalent in the case of a polar sulfuric acid environment than with nonpolar toluene or H2Pc environment, whereby the covalency of this bonding is increased upon addition of tert-butyl groups. No contribution from in-plane pi bonding is found. 相似文献
942.
Juri Litterscheidt Jeffrey S. Bandar Max Ebert Robert Forschner Korinna Bader Tristan H. Lambert Wolfgang Frey Andrea Bühlmeyer Marcus Brndle Finn Schulz Sabine Laschat 《Angewandte Chemie (International ed. in English)》2020,59(26):10557-10565
Aminocyclopropenium ions have raised much attention as organocatalysts and redox active polymers. However, the self‐assembly of amphiphilic aminocyclopropenium ions remains challenging. The first deltic ionic liquid crystals based on aminocyclopropenium ions have been developed. Differential scanning calorimetry, polarizing optical microscopy and X‐ray diffraction provided insight into the unique self‐assembly and nanosegregation of these liquid crystals. While the combination of small headgroups with linear p‐alkoxyphenyl units led to bilayer‐type smectic mesophases, wedge‐shaped units resulted in columnar mesophases. Upon increasing the size and polyphilicity of the aminocyclopropenium headgroup, a lamellar phase was formed. 相似文献
943.
Roman Purkhart Anne Hillmann Rolf Graupner Gunther Becher 《International Journal for Ion Mobility Spectrometry》2012,15(2):63-68
Detection of special disease markers in exhaled breath is a method becoming more and more relevant in medical diagnostic.
The test environment plays a big role in the analysis of exhaled air when using ion mobility spectrometry (IMS). Environmental
contaminants appear also in exhaled air of test persons, potentially even in other forms then in the ambient air. Different
ways to deal with these environmental factors will be discussed and our method of choice will be presented. It was possible
to identify specific fingerprints for dedicated features of probands as well as for specific environmental pollution. By using
statistical evaluation it was also possible to identify characteristic features of probands notwithstanding the environmental
burden for correct assignment into specific groups, reaching correct classification rates above 0.85. 相似文献
944.
945.
Dr. Carlos Fernández‐de‐Alba Dr. Hiroki Takahashi Alexandre Richard Yves Chenavier Dr. Lionel Dubois Vincent Maurel Dr. Daniel Lee Dr. Sabine Hediger Dr. Gaël De Paëpe 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(12):4512-4517
Magic‐angle spinning dynamic nuclear polarization (MAS‐DNP) has been proven to be a powerful technique to enhance the sensitivity of solid‐state NMR (SSNMR) in a wide range of systems. Here, we show that DNP can be used to polarize lipids using a lipid‐anchored polarizing agent. More specifically, we introduce a C16‐functionalized biradical, which allows localization of the polarizing agents in the lipid bilayer and DNP experiments to be performed in the absence of excess cryo‐protectant molecules (glycerol, dimethyl sulfoxide, etc.). This constitutes another original example of the matrix‐free DNP approach that we recently introduced. 相似文献
946.
947.
Maximilian F. Koch Sabrina Harteis Iris D. Blank Galina Pestel Lutz F. Tietze Christian Ochsenfeld Sabine Schneider Stephan A. Sieber 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2015,127(46):13754-13758
Analogues of the natural product duocarmycin bearing an indole moiety were shown to bind aldehyde dehydrogenase 1A1 (ALDH1A1) in addition to DNA, while derivatives without the indole solely addressed the ALDH1A1 protein. The molecular mechanism of selective ALDH1A1 inhibition by duocarmycin analogues was unraveled through cocrystallization, mutational studies, and molecular dynamics simulations. The structure of the complex shows the compound embedded in a hydrophobic pocket, where it is stabilized by several crucial π‐stacking and van der Waals interactions. This binding mode positions the cyclopropyl electrophile for nucleophilic attack by the noncatalytic residue Cys302, thereby resulting in covalent attachment, steric occlusion of the active site, and inhibition of catalysis. The selectivity of duocarmycin analogues for ALDH1A1 is unique, since only minor alterations in the sequence of closely related protein isoforms restrict compound accessibility. 相似文献
948.
A series of in situ‐generated ruthenium hydride complexes Ru(PPh3)2(CO)H(Ln) (n = a – h ) incorporating a Schiff base ligand was investigated for the isomerization of olefins. 1H‐NMR was used to characterize the new hydride species in combination with 31P‐NMR. Allylbenzene and 1‐octene were used as model substrates. Temperature, solvents and catalyst/substrate mole ratio were taken into account as parameters to optimize the isomerization reaction. All catalysts showed the best performance in 2‐butanol, suggesting that the catalytic activity depends not only strongly on the steric and electronic environment of the ruthenium but also on the chosen solvent. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
949.
Yannick Pannier Henry Proudhon Cristian Mocuta Dominique Thiaudière Sabine Cantournet 《Journal of synchrotron radiation》2011,18(6):907-911
An in situ tensile–shear loading device has been designed to study elastomer crystallization using synchrotron X‐ray scattering at the Synchrotron Soleil on the DiffAbs beamline. Elastomer tape specimens of thickness 2 mm can be elongated by up to 500% in the longitudinal direction and sheared by up to 200% in the transverse direction. The device is fully automated and plugged into the TANGO control system of the beamline allowing synchronization between acquisition and loading sequences. Experimental results revealing the evolution of crystallization peaks under load are presented for several tension/shear loading sequences. 相似文献
950.