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491.
V. I. Lukanin D. S. Chunaev A. Ya. Karasik 《Journal of Experimental and Theoretical Physics》2011,113(3):412-421
The nonlinear process of two-photon interband absorption is studied in tungstate and molybdate oxide crystals excited by a
sequence of high-power picosecond pulses with a wavelength of 523.5 nm. The transmission of the crystals is measured for the
excitation pulse intensity up to 100 GW/cm2. The pulse intensity in the crystals initially transparent at a wavelength of 523.5 nm is strongly limited due to two-photon
absorption (TPA), and the reciprocal transmission in PbWO4 and ZnWO4 crystals reaches 50–60. In all crystals, TPA induces long-lived one-photon absorption, which affects the nonlinear process
dynamics and leads to a hysteresis in the dependence of the transmission on the laser excitation intensity. Absorption dichroism
manifests itself in a significant difference in the transmission intensities when the principal orthogonal optical axes of
the crystals are excited. The TPA coefficients are determined during the excitation of two optical axes of the crystals. TPA
coefficients β for the crystals vary over a wide range, namely, from β = 2.4 cm/GW for PbMoO4 to β = 0.14 cm/GW for CaMoO4, and the values of β can differ almost threefold when different optical axes of a crystal are excited. Good agreement is
achieved between the measured intensities limited by TPA and the estimates calculated from the measured nonlinear coefficients.
Stimulated Raman scattering (SRS) upon excitation at a wavelength of 523.5 nm is only detected in two of the four crystals
under study. The experimental results make it possible to explain the suppression of SRS by its competition with TPA, and
the measured nonlinear coefficients are used to estimate this suppression. 相似文献
492.
Jeanette Melin Stefan Cano Agnes Flel Laura Gschel Leslie Pendrill 《Entropy (Basel, Switzerland)》2022,24(7)
Metrological methods for word learning list tests can be developed with an information theoretical approach extending earlier simple syntax studies. A classic Brillouin entropy expression is applied to the analysis of the Rey’s Auditory Verbal Learning Test RAVLT (immediate recall), where more ordered tasks—with less entropy—are easier to perform. The findings from three case studies are described, including 225 assessments of the NeuroMET2 cohort of persons spanning a cognitive spectrum from healthy older adults to patients with dementia. In the first study, ordinality in the raw scores is compensated for, and item and person attributes are separated with the Rasch model. In the second, the RAVLT IR task difficulty, including serial position effects (SPE), particularly Primacy and Recency, is adequately explained (Pearson’s correlation ) with construct specification equations (CSE). The third study suggests multidimensionality is introduced by SPE, as revealed through goodness-of-fit statistics of the Rasch analyses. Loading factors common to two kinds of principal component analyses (PCA) for CSE formulation and goodness-of-fit logistic regressions are identified. More consistent ways of defining and analysing memory task difficulties, including SPE, can maintain the unique metrological properties of the Rasch model and improve the estimates and understanding of a person’s memory abilities on the path towards better-targeted and more fit-for-purpose diagnostics. 相似文献
493.
Marta-Lisette Pikma Dr. Märt Lõkov Dr. Sofja Tshepelevitsh Jaan Saame Tõiv Haljasorg Dr. Lauri Toom Dr. Sigrid Selberg Prof. Ivo Leito Assoc. Prof. Agnes Kütt 《European journal of organic chemistry》2023,26(28):e202300453
A new group of bases with benzophenoneiminyl (bpi) moiety has been synthesized and characterized in this work. The title compound tris(benzophenoneimino)phosphane (P(bpi)3) 1 was prepared with a convenient one-pot approach: benzophenone imine was deprotonated using MeMgCl and reacted with PBr3 in diglyme. The method could be considered as a method of choice for preparing other (amino)phosphanes in case lithio-intermediates and/or protonated phosphane is out of consideration. Phosphane 1 is further used to prepare a range of related phosphonium cations and phosphazenes. Phosphonium cations were deprotonated to assess the stability of the resulting phosphonium ylides. In some cases, the bulky substances were capable of forming P−N heterocycles. Experimental (MeCN) and computational (MeCN, THF, gas-phase) basicities of benzophenone imine, phosphane 1 , phosphonium ylides, and phosphazenes, as well as some representative XRD structures, are presented and discussed. 相似文献
494.
M. Sc. Gerlis von Haugwitz B. Sc. Kian Donnelly M. Sc. Mara Di Filippo Dr. Daniel Breite Max Phippard Dr. Agnes Schulze Dr. Ren Wei Dr. Marcus Baumann Prof. Dr. Uwe T. Bornscheuer 《Angewandte Chemie (International ed. in English)》2023,62(18):e202216962
Poly(vinyl alcohol) (PVA) is a water-soluble synthetic vinyl polymer with remarkable physical properties including thermostability and viscosity. Its biodegradability, however, is low even though a large amount of PVA is released into the environment. Established physical-chemical degradation methods for PVA have several disadvantages such as high price, low efficiency, and secondary pollution. Biodegradation of PVA by microorganisms is slow and frequently involves pyrroloquinoline quinone (PQQ)-dependent enzymes, making it expensive due to the costly cofactor and hence unattractive for industrial applications. In this study, we present a modified PVA film with improved properties as well as a PQQ-independent novel enzymatic cascade for the degradation of modified and unmodified PVA. The cascade consists of four steps catalyzed by three enzymes with in situ cofactor recycling technology making this cascade suitable for industrial applications. 相似文献
495.
Reaction of dialkyl alkylphosphonates with SOCl2 in the presence of DMF, reported by Maier, can serve as a convenient route to simple monoalkyl alkylphosphonochloridates. However, when a substrate contains a (2-dialkylamino)ethyl group as one of the ester functions, the course of the reaction is determined by the nature of the N-alkyl groups. With the NMe2 group present, reaction with SOCl2 occurs at nitrogen, and no exchange of groups at phosphorus takes place. The NEt2 group, on the other hand, directs the reaction to phosphorus, and the Maier reaction of the exchange of one ester group OR for Cl proceeds in high yields. © 1996 John Wiley & Sons, Inc. 相似文献