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791.
The transmission factor of a corner in a dielectric-rod or optical-fiber waveguide is calculated applying the field matching method. The calculation is carried out with the exact field components of the HE11-mode in order to include also the cases of a glass fiber with a large index difference or a microwave dielectric-rod transmission line. The general expressions are subsequently simplified for weakly guided waves in the microwave or optical region. Very simple approximate formulas are derived for corners of small angle. The insertion loss of corners has been measured in the microwave region and has been found to agree with theory for angles not exceeding 40°. The electromagnetic field near corners has been recorded to give an insight in the transmission and radiation properties of corners. 相似文献
792.
793.
A. Palmero E. D. van Hattum H. Rudolph F. H.P.M. Habraken 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,41(2):303-309
In plasma-assisted magnetron sputtering, the ion cathode fall region is the part of the plasma where the DC electric field
and ion current evolve from zero to their maximum values at the cathode. These quantities are straightforwardly related to
the deposition rate of the sputtered material.
In this work we derive simple relations for the measurable axially averaged values of the ion density and the ion current
at the ion cathode fall region and relate them with the deposition rate. These relations have been tested experimentally in
the case of an argon plasma in a magnetron sputtering system devoted to depositing amorphous silicon. Using a movable Langmuir
probe, the profiles of the plasma potential and ion density were measured along an axis perpendicularly to the cathode and
in front of the so-called race-track. The deposition rate of silicon, under different conditions of pressure and input power,
has been found to compare well with those determined with the relations derived. 相似文献
794.
Xianhai Tian Lina Song Kaveh Farshadfar Matthias Rudolph Frank Rominger Thomas Oeser Alireza Ariafard A. Stephen K. Hashmi 《Angewandte Chemie (International ed. in English)》2020,59(1):471-478
We report a switchable synthesis of acylindoles and quinoline derivatives via gold‐catalyzed annulations of anthranils and ynamides. α‐Imino gold carbenes, generated in situ from anthranils and an N,O‐coordinated gold(III) catalyst, undergo electrophilic attack to the aryl π‐bond, followed by unexpected and highly selective 1,4‐ or 1,3‐acyl migrations to form 6‐acylindoles or 5‐acylindoles. With the (2‐biphenyl)di‐tert‐butylphosphine (JohnPhos) ligand, gold(I) carbenes experienced carbene/carbonyl additions to deliver quinoline oxides. Some of these epoxides are valuable substrates for the preparation of 3‐hydroxylquinolines, quinolin‐3(4H)‐ones, and polycyclic compounds via facile in situ rearrangements. The reaction can be efficiently conducted on a gram scale and the obtained products are valuable substrates for preparing other potentially useful compounds. A computational study explained the unexpected selectivities and the dependency of the reaction pathway on the oxidation state and ligands of gold. With gold(III) the barrier for the formation of the strained oxirane ring is too high; whereas with gold(I) this transition state becomes accessible. Furthermore, energetic barriers to migration of the substituents on the intermediate sigma‐complexes support the observed substitution pattern in the final product. 相似文献
795.
Xianhai Tian Lina Song Dr. Kaveh Farshadfar Dr. Matthias Rudolph Dr. Frank Rominger Dr. Thomas Oeser Prof. Dr. Alireza Ariafard Prof. Dr. A. Stephen K. Hashmi 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(1):479-486
We report a switchable synthesis of acylindoles and quinoline derivatives via gold-catalyzed annulations of anthranils and ynamides. α-Imino gold carbenes, generated in situ from anthranils and an N,O-coordinated gold(III) catalyst, undergo electrophilic attack to the aryl π-bond, followed by unexpected and highly selective 1,4- or 1,3-acyl migrations to form 6-acylindoles or 5-acylindoles. With the (2-biphenyl)di-tert-butylphosphine (JohnPhos) ligand, gold(I) carbenes experienced carbene/carbonyl additions to deliver quinoline oxides. Some of these epoxides are valuable substrates for the preparation of 3-hydroxylquinolines, quinolin-3(4H)-ones, and polycyclic compounds via facile in situ rearrangements. The reaction can be efficiently conducted on a gram scale and the obtained products are valuable substrates for preparing other potentially useful compounds. A computational study explained the unexpected selectivities and the dependency of the reaction pathway on the oxidation state and ligands of gold. With gold(III) the barrier for the formation of the strained oxirane ring is too high; whereas with gold(I) this transition state becomes accessible. Furthermore, energetic barriers to migration of the substituents on the intermediate sigma-complexes support the observed substitution pattern in the final product. 相似文献
796.
Journal of Solution Chemistry - The totally symmetric stretching mode $$\nu_{1}$$ Ln–(OH2) of the first hydration shells of all the rare earth (RE) ions across the series from lanthanum to... 相似文献
797.
Dr. Kalathil K. Kartha Felix Wendler Dr. Tobias Rudolph Philip Biehl Prof. Dr. Gustavo Fernández Prof. Dr. F. H. Schacher 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(3):606-610
pH-Tunable nanoscale morphology and self-assembly mechanism of a series of oligo(p-phenyleneethynylene) (OPE)-based bolaamphiphiles featuring poly(ethylene imine) (PEI) side chains of different length and degree of hydrolysis are described. Protonation and deprotonation of the PEI chains by changing the pH alters the hydrophilic/hydrophobic balance of the systems and, in turn, the strength of intermolecular interactions between the hydrophobic OPE moieties. Low pH values (3) lead to weak interaction between the OPEs and result in spherical nanoparticles, in which aggregation follows an isodesmic mechanism. In contrast, higher pH values (11) induce deprotonation of the polymer chains and lead to a stronger, cooperative aggregation into anisotropic nanostructures. Our results demonstrate that pH-responsive chains can be exploited as a tool to tune self-assembly mechanisms, which opens exciting possibilities to develop new stimuli-responsive materials. 相似文献
798.
799.
A norbornene-mediated palladium-catalyzed sequence is described in which two alkyl-aryl bonds and one alkenyl-aryl bond are formed in one pot with use of microwave irradiation. A variety of symmetrical and unsymmetrical oxygen-, nitrogen-, silicon-, and sulfur-containing tricyclic heterocycles were synthesized from a Heck acceptor and an aryl iodide containing two tethered alkyl halides. This approach was further applied to the synthesis of a tricyclic mescaline analogue. 相似文献
800.
Nara Singh BS Liu Z Wadsworth R Grawe H Brock TS Boutachkov P Braun N Blazhev A Górska M Pietri S Rudolph D Domingo-Pardo C Steer SJ Ataç A Bettermann L Cáceres L Eppinger K Engert T Faestermann T Farinon F Finke F Geibel K Gerl J Gernhäuser R Goel N Gottardo A Grębosz J Hinke C Hoischen R Ilie G Iwasaki H Jolie J Kaşkaş A Kojouharov I Krücken R Kurz N Merchán E Nociforo C Nyberg J Pfützner M Prochazka A Podolyák Z Regan PH Reiter P Rinta-Antila S Scholl C Schaffner H Söderström PA Warr N 《Physical review letters》2011,107(17):172502
A β-decaying high-spin isomer in (96)Cd, with a half-life T(1/2)=0.29(-0.10)(+0.11) s, has been established in a stopped beam rare isotope spectroscopic investigations at GSI (RISING) experiment. The nuclei were produced using the fragmentation of a primary beam of (124)Xe on a (9)Be target. From the half-life and the observed γ decays in the daughter nucleus, (96)Ag, we conclude that the β-decaying state is the long predicted 16(+) "spin-gap" isomer. Shell-model calculations, using the Gross-Frenkel interaction and the πν(p(1/2),g(9/2)) model space, show that the isoscalar component of the neutron-proton interaction is essential to explain the origin of the isomer. Core excitations across the N=Z=50 gaps and the Gamow-Teller strength, B(GT) distributions have been studied via large-scale shell-model calculations using the πν(g,d,s) model space to compare with the experimental B(GT) value obtained from the half-life of the isomer. 相似文献