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991.
Dr. Markus Horn Dr. Ludwig H. Schappele Dr. Gabriele Lang‐Wittkowski Prof. Dr. Herbert Mayr Dr. Armin R. Ofial 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(1):249-263
Rates of hydride transfer from several hydride donors to benzhydrylium ions have been measured at 20 °C and used for the determination of empirical nucleophilicity parameters N and sN according to the linear free energy relationship log k20 °C=sN(N+E). Comparison of the rate constants of hydride abstraction by tritylium ions with those calculated from the reactivity parameters sN, N, and E showed fair agreement. Therefore, it was possible to convert the large number of literature data on hydride abstraction by tritylium ions into N and sN parameters for the corresponding hydride donors, and construct a reactivity scale for hydride donors covering more than 20 orders of magnitude. 相似文献
992.
Graziano Baccolini Carla Boga Gabriele Micheletti 《Phosphorus, sulfur, and silicon and the related elements》2013,188(11):2303-2315
In this article, we present a study about the non-enzymatic hydrolysis of phosphoenolpyruvate (PEP) by following the reaction course through 31P NMR spectroscopy. We have demonstrated that PEP in water exists mainly as a very stable cyclic pentacoordinate phosphorus compound in equilibrium with other cyclic forms. This explains the PEP stability in water. In contrast, after addition of an alcohol to a PEP aqueous solution, other very unstable cyclic pentacoordinated intermediates are formed, which immediately collapse, giving a feasible phosphorylation of the alcohol. It is known that cyclic pentacoordinated phosphorus intermediates are favored over the corresponding acyclic intermediates by a factor of 106–108, and this preference, found also in this study, might be the “driver mechanism” able to overcome the clutter of abiotic chemistry, thus permitting formation of pre-RNA molecules probably with a “self-organized process.” 相似文献
993.
Dr. Alice Santoro Jenifer S. Calvo Manuel David Peris-Díaz Prof. Artur Krężel Prof. Gabriele Meloni Prof. Peter Faller 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(20):7904-7909
Copper complexes are of medicinal and biological interest, including as anticancer drugs designed to cleave intracellular biomolecules by O2 activation. To exhibit such activity, the copper complex must be redox active and resistant to dissociation. Metallothioneins (MTs) and glutathione (GSH) are abundant in the cytosol and nucleus. Because they are thiol-rich reducing molecules with high CuI affinity, they are potential competitors for a copper ion bound in a copper drug. Herein, we report the investigation of a panel of CuI/CuII complexes often used as drugs, with diverse coordination chemistries and redox potentials. We evaluated their catalytic activity in ascorbate oxidation based on redox cycling between CuI and CuII, as well as their resistance to dissociation or inactivation under cytosolically relevant concentrations of GSH and MT. O2-activating CuI/CuII complexes for cytosolic/nuclear targets are generally not stable against the GSH/MT system, which creates a challenge for their future design. 相似文献
994.
Jakob Wallner Manfred Kühleitner Norbert Brunner Gabriele Lhota Karola Vorauer-Uhl 《Journal of mathematical chemistry》2014,52(2):575-587
For more than 50 years, optical biosensors have been used to measure bio-molecular interactions. The most frequently applied binding model to fit biosensor data is the simple 1:1 binding model which requires the stabilization of the association phase to the equilibrium Req and the stabilization of the dissociation phase to the equilibrium zero. However, due to technical limitations many published biosensor measurements are finished before these requirements are fulfilled. In the present study, a long term binding interaction analysis with a monoclonal antibody, namely IgG 2F5 and UG37 a specific antigen with a promising biosensor platform, the Bio-Layer Interferometry, was performed. Data fitting with the simple 1:1 binding model to the association phase was inappropriate and the fitted parameters varied with the concentration and time, which contradicts the theory of the simple 1:1 binding model. Furthermore, extrapolation of the fits with individual times spans compared to 100 % of the obtained data systematically underestimated the actual observed binding curve. Interestingly, an alternative model based on the cumulative distribution function of the log-normal probability distribution remedied the aforementioned problems allowing $\hbox {K}_\mathrm{L}$ (which is the analog to the affinity constant $\hbox {K}_\mathrm{D}$ ) to be estimated. We further demonstrate that this model fits the biosensor data far better and is essentially less affected by the stabilization of the association phase to the equilibrium (Req) and the stabilization of the dissociation phase to the equilibrium zero. Finally, extrapolation with the log-normal model predicts the actually observed binding curve in a proper manner. 相似文献
995.
Saeid Sadeh Dr. Gabriele Schatte Prof. Dr. Jens Müller 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(40):13408-13417
The enantiomerically pure dibromoferrocene 3 [(Sp,Sp)‐1,1′‐dibromo‐2,2′‐di(isopropyl)ferrocene], equipped with two iPr groups in α positions, was prepared using known “Ugi amine” chemistry. Species 3 was targeted in order to gain access to new [1]ferrocenophanes ([1]FCPs) to be used as monomers for ring‐opening polymerization. The iPr groups on the sandwich unit were introduced to stabilize bridging moieties, as well as to increase solubilities of targeted metallopolymers. The planar chiral dibromide 3 can quantitatively be lithiated at 0 °C [2 equiv nBuLi, hexanes/thf (9:1), 30 min]. Salt‐metathesis reactions with respective element dichloride species gave chiral [1]FCPs with a variety of bridging moieties [ERx=Ga[2‐(Me2NCH2)C6H4] ( 4 a ), SiMe2 ( 4 b ), SntBu2 ( 4 c ), BNiPr2 ( 4 d )]. The new [1]FCPs were fully characterized including single‐crystal X‐ray analysis. The stabilizing iPr groups on the Cp rings increase the thermal stabilities of 4 b – d compared to known [1]FCPs, equipped with the same bridging moieties. All three compounds 4 b – d are volatile and could be isolated by vacuum sublimation. Our new approach to [1]FCPs has the potential to overcome many of the existing difficulties in ferrocenophane chemistry, such as limited stability of starting monomers and low solubilities of resulting polyferrocenes. 相似文献
996.
The aim of this note is to establish the existence of three solutions for a perturbed two-point boundary value problem depending of two real parameters. The approach is based on variational methods. 相似文献
997.
Gabriele Bonanno Giuseppina D’Aguì 《Nonlinear Analysis: Theory, Methods & Applications》2010,72(3-4):1977-1982
In this paper, the existence of non-zero solutions to a Neumann boundary value problem is established. Multiplicity results are also pointed out. The approach is based on a novel critical point theorem. 相似文献
998.
Stephan Dahlke Sören Häuser Gabriele Steidl Gerd Teschke 《Monatshefte für Mathematik》2013,169(1):15-32
This papers examines structural properties of the recently developed shearlet coorbit spaces in higher dimensions. We prove embedding theorems for subspaces of shearlet coorbit spaces resembling shearlets on the cone in three dimensions into Besov spaces. The results are based on general atomic decompositions of Besov spaces. Furthermore, we establish trace results for these subspaces with respect to the coordinate planes. It turns out that in many cases these traces are contained in lower dimensional shearlet coorbit spaces. 相似文献
999.
Del Boccio P Raimondo F Pieragostino D Morosi L Cozzi G Sacchetta P Magni F Pitto M Urbani A 《Electrophoresis》2012,33(4):689-696
Urinary exosomes are released from every renal epithelial cell type facing the urinary space and therefore, they may carry molecular markers of renal dysfunction and structural injury. Here, we present a hyphenated microLC-Q-TOF-MS platform for lipidomics studies applied to investigate the urinary exosome lipid repertoire. Lipids were separated by reversed-phase chromatography using a linear gradient of formic acid 0.2% and tetrahydrofuran, in 40 min of analysis. Features (m/z with associated own retention time) were extracted by MarkerLynx(TM) (Waters) and processed, demonstrating good analytical performance in terms of repeatability and mass accuracy of the microLC Q-TOF MS platform. In particular, a stable retention time (RSD less than 4%) and relative intensity (RSD from 2.9% to 11%) were observed. Moreover, the method takes advantages by the use of a lock spray interface (Waters) that allows readjusting the m/z data after acquisition, obtaining inaccuracy below 6 ppm in measuring the m/z value of the reference compound during chromatographic run. The method was employed in a preliminary application to perform comparative analysis from healthy control subjects and renal cell carcinoma (RCC) patients, in order to possibly highlight differences in lipid composition to be exploited as potential tumor biomarker. Differential lipid composition in RCC urinary exosomes was achieved and tentatively identified by accurate mass, providing a preliminary indication of a relationship between lipid composition of urinary exosomes and RCC disease. Among the total features significantly different in RCC exosomes, the ion at m/z 502.3 was taken as an example for molecular confirmation by MS/MS fragmentation analysis. 相似文献
1000.