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81.
Schuhmann K Almeida R Baumert M Herzog R Bornstein SR Shevchenko A 《Journal of mass spectrometry : JMS》2012,47(1):96-104
Top-down shotgun lipidomics relies on direct infusion of total lipid extracts into a high-resolution tandem mass spectrometer and implies that individual lipids are recognized by their accurately determined m/z. Lipid ionization efficiency and detection specificity strongly depend on the acquisition polarity, and therefore it is beneficial to analyze lipid mixtures in both positive and negative modes. Hybrid LTQ Orbitrap mass spectrometers are widely applied in top-down lipidomics; however, rapid polarity switching was previously unfeasible because of the severe and immediate degradation of mass accuracy. Here, we report on a method to rapidly acquire high-resolution spectra in both polarity modes with sub-ppm mass accuracy and demonstrate that it not only simplifies and accelerates shotgun lipidomics analyses but also improves the lipidome coverage because more lipid classes and more individual species within each class are recognized. In this way, shotgun analysis of total lipid extracts of human blood plasma enabled to quantify 222 species from 15 major lipid classes within 7?min acquisition cycle. 相似文献
82.
Andrej Staško Maroš Bella Ján Rimarčík Zuzana Barbieriková Viktor Milata Vladimír Lukeš Vlasta Brezová 《Journal of Physical Organic Chemistry》2012,25(8):643-648
Photoinduced reactions of 9‐oxo‐6,9‐dihydro[1,2,5]selenadiazolo[3,4‐f]quinoline‐8‐carboxylic acid (SeQCA) were investigated in alkaline media (aqueous NaOH solutions) by electron paramagnetic resonance (EPR) spectroscopy, following the in situ formation of paramagnetic species. According to UV–Vis and nuclear magnetic resonance investigations, protonation (pH ≈ 11) and deprotonation (pH ≈ 13) of the imino hydrogen of the 4‐pyridone moiety has to be considered, reflected also in the different EPR spectra observed upon irradiation. Photoinduced generation of radicals was found only for carboxylate substituted SeQCA; other studied selenadiazoloquinolone derivatives, together with those substituted at the C(8) position (R = H, COOCH2CH3, COOCH3, COCH3 or CN), did not generate paramagnetic species during exposure. Consequently, photodecarboxylation was suggested as the decisive step, accompanied by the decomposition of the selenadiazole ring, resulting in the formation of ortho‐hydroxylate anions. EPR parameters elucidated from experimental EPR spectra obtained at pH ≈ 11 and pH ≈ 13 indicate the formation of oxygen‐centered radicals at the decarboxylated 4‐pyridone ring. EPR spin trapping experiments with nitromethane confirmed a very effective photoinduced electron transfer from all the selenadiazoloquinolones investigated. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
83.
Andrej Zlatoš 《Journal de Mathématiques Pures et Appliquées》2012,98(1):89-102
We use a new method in the study of Fisher–KPP reaction–diffusion equations to prove existence of transition fronts for inhomogeneous KPP-type non-linearities in one spatial dimension. We also obtain new estimates on entire solutions of some KPP reaction–diffusion equations in several spatial dimensions. Our method is based on the construction of sub- and super-solutions to the non-linear PDE from solutions of its linearization at zero. 相似文献
84.
Gregory Seregin Luis Silvestre Vladimír Šverák Andrej Zlatoš 《Journal of Differential Equations》2012,252(1):505-540
We investigate the validity and failure of Liouville theorems and Harnack inequalities for parabolic and elliptic operators with low regularity coefficients. We are particularly interested in operators of the form resp. with a divergence-free drift b. We prove the Liouville theorem and Harnack inequality when resp. and provide a counterexample demonstrating sharpness of our conditions on the drift. Our results generalize to divergence-form operators with an elliptic symmetric part and a BMO skew-symmetric part. We also prove the existence of a modulus of continuity for solutions to the elliptic problem in two dimensions, depending on the non-scale-invariant norm . In three dimensions, on the other hand, bounded solutions with drifts may be discontinuous. 相似文献
85.
Michiel E. Hochstenbach Andrej Muhič Bor Plestenjak 《Linear algebra and its applications》2012,436(8):2725-2743
We present several transformations that can be used to solve the quadratic two-parameter eigenvalue problem (QMEP), by formulating an associated linear multiparameter eigenvalue problem. Two of these transformations are generalizations of the well-known linearization of the quadratic eigenvalue problem and linearize the QMEP as a singular two-parameter eigenvalue problem. The third replaces all nonlinear terms by new variables and adds new equations for their relations. The QMEP is thus transformed into a nonsingular five-parameter eigenvalue problem. The advantage of these transformations is that they enable one to solve the QMEP using existing numerical methods for multiparameter eigenvalue problems. We also consider several special cases of the QMEP, where some matrix coefficients are zero 相似文献
86.
Kai Schuhmann Reinaldo Almeida Mark Baumert Ronny Herzog Stefan R. Bornstein Andrej Shevchenko 《Journal of mass spectrometry : JMS》2012,47(1):96-104
Top–down shotgun lipidomics relies on direct infusion of total lipid extracts into a high‐resolution tandem mass spectrometer and implies that individual lipids are recognized by their accurately determined m/z. Lipid ionization efficiency and detection specificity strongly depend on the acquisition polarity, and therefore it is beneficial to analyze lipid mixtures in both positive and negative modes. Hybrid LTQ Orbitrap mass spectrometers are widely applied in top–down lipidomics; however, rapid polarity switching was previously unfeasible because of the severe and immediate degradation of mass accuracy. Here, we report on a method to rapidly acquire high‐resolution spectra in both polarity modes with sub‐ppm mass accuracy and demonstrate that it not only simplifies and accelerates shotgun lipidomics analyses but also improves the lipidome coverage because more lipid classes and more individual species within each class are recognized. In this way, shotgun analysis of total lipid extracts of human blood plasma enabled to quantify 222 species from 15 major lipid classes within 7 min acquisition cycle. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
87.
Gregory Kennedy Cornelia Chilian Radojko Jaćimović Gašper Žerovnik Luka Snoj Andrej Trkov 《Journal of Radioanalytical and Nuclear Chemistry》2012,291(2):555-559
In order to predict the self-shielding effect in neutron activation of non-spherical samples in reactor neutron spectra, it
is important to know whether the neutron field is sufficiently anisotropic to cause significant variations between horizontal
and vertical sample orientation or with orientation relative to the direction towards the reactor core. Metal wires with significant
neutron self-shielding were irradiated in several channels of the SLOWPOKE reactor at Ecole Polytechnique Montreal and the
TRIGA reactor at the Jožef Stefan Institute. In all cases, the amount of thermal or epithermal self-shielding was found to
be identical, within the experimental uncertainty, regardless of the orientation of the wire, indicating that the neutron
field is essentially isotropic. Models used to predict neutron self-shielding need to be adjusted accordingly. In our Monte
Carlo model, the tube-shaped neutron source was moved back into the moderator and reflecting materials near the sample location
were included, which produced an isotropic neutron field at the sample location. 相似文献
88.
Evgenij V. Zarudnitskii Aleksandr A. Yurchenko Anatolij S. Merkulov Marina G. Semenova Aleksandr M. Pinchuk Andrej A. Tolmachev 《Heteroatom Chemistry》2005,16(7):648-655
The reaction of phosphorus(III) halides with 6‐substituted imidazo[2,1‐b]thiazoles in the presence of bases proceeds regioselectively and affords 5‐phosphinoimidazo[2,1‐b]thiazoles, useful synthons for the preparation of various P(III) and P(V) derivatives. 5‐Phosphinoimidazo[2,1‐b]thiazoles are selectively alkylated at the phosphorus or heterocyclic nitrogen atom, depending on the alkylating agent. © 2005 Wiley Periodicals, Inc. Heteroatom Chem 16:648–655, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20166 相似文献
89.
Alja Prah Tanja Gavrani Andrej Perdih Marija Sollner Dolenc Janez Mavri 《Molecules (Basel, Switzerland)》2022,27(19)
Monoamine oxidases (MAOs) are an important group of enzymes involved in the degradation of neurotransmitters and their imbalanced mode of action may lead to the development of various neuropsychiatric or neurodegenerative disorders. In this work, we report the results of an in-depth computational study in which we performed a static and a dynamic analysis of a series of substituted β-carboline natural products, found mainly in roasted coffee and tobacco smoke, that bind to the active site of the MAO-A isoform. By applying molecular docking in conjunction with structure-based pharmacophores and molecular dynamics simulations coupled with dynamic pharmacophores, we extensively investigated the geometric aspects of MAO-A binding. To gain insight into the energetics of binding, we used the linear interaction energy (LIE) method and determined the key anchors that allow productive β-carboline binding to MAO-A. The results presented herein could be applied in the rational structure-based design and optimization of β-carbolines towards preclinical candidates that would target the MAO-A enzyme and would be applicable especially in the treatment of mental disorders such as depression. 相似文献
90.