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991.
Miquel Grau 《Numerical Algorithms》2003,34(1):1-12
In this paper, we suggest an improvement to the iterative methods based on the inverse interpolation polynomial, also referred to as the generalized Hermite interpolation, which increases the local order of convergence. A symbolic computation allows us to find the best coefficients with regard to the order of convergence. The adaptation of the strategy presented here gives a new iteration function with a new evaluation of the function. It also shows a smaller cost if we use adaptive multi-precision arithmetic. The numerical results computed using this system, with a floating point system representing 200 and 1000 decimal digits support this theory. 相似文献
992.
Magnon contribution to the magnetoresistance of iron nanowires deposited using pulsed electrodeposition 下载免费PDF全文
Philip Sergelius Josep M. Montero Moreno Martin Waleczek Tim Böhnert Detlef Görlitz Kornelius Nielsch 《固体物理学:研究快报》2015,9(4):255-258
Iron nanowires with a square cross section are grown by pulsed electrodeposition within a newly developed nanochannel template that allows for easy characterization. Measurements of the magnetoresistance as a function of magnetic field and temperature are performed within a large parameter window allowing for the investigation of the magnonic contribution to the magnetoresistance of electrodeposited iron nanowires. Values for the temperature dependent magnon stiffness D (T) are extracted: D (T) = D0(1 – d1T2) = 365(1 – 4.4 × 10–6 · T2 · K–2) meV Å2.
993.
A Spectroscopic Study of Colchicine in the Solid State and in Solution by Multinuclear Magnetic Resonance and Vibrational Circular Dichroism 下载免费PDF全文
Albert Virgili Ma Mar Quesada‐Moreno Juan Ramón Avilés‐Moreno Juan Jesús López‐González M. Ángeles García Rosa M. Claramunt M. Rosario Torres M. Luisa Jimeno Felipe Reviriego Ibon Alkorta José Elguero 《Helvetica chimica acta》2014,97(4):471-490
Although almost 200‐years‐old, several unknown aspects remain to be explored of colchicine, the unique available drug for acute flares of gout. In this article, we report density‐functional theory (DFT) studies of geometry, energy, and NMR; 1H‐, 13C‐, and 15N‐NMR chemical shifts and some spin‐spin coupling constants, including the complete analysis of the saturated part (ring B); the assignment of both enantiomers by NMR using a chiral solvating agent; solid‐state NMR experiments of the different forms of natural and racemic colchicine, and IR and vibrational circular dichroism (VCD) studies of these same forms. 相似文献
994.
Roberto Flores‐Moreno Edwin Posada Félix Moncada Jonathan Romero Jorge Charry Manuel Díaz‐Tinoco Sergio A. González Néstor F. Aguirre Andrés Reyes 《International journal of quantum chemistry》2014,114(1):50-56
LOWDIN is a computational program that implements the Any Particle Molecular Orbital (APMO) method. The current version of the code encompasses Hartree–Fock, second‐order Møller–Plesset, configuration interaction, density functional, and generalized propagator theories. LOWDIN input file offers a unique flexibility, allowing users to exploit all the programs' capabilities to study systems containing any type and number of quantum species. This review provides a basic introduction to LOWDIN's key computational details and capabilities. © 2013 Wiley Periodicals, Inc. 相似文献
995.
María‐Antonia Serrano Juan Carlos Moreno Gonzalo Gurrea Members of the Valencia Solar Radiation Research Group 《Photochemistry and photobiology》2014,90(4):911-918
Excessive exposure to ultraviolet radiation (UVR) is considered the most important environmental risk factor in the development of melanoma and skin cancer. Outdoor workers are among those with the highest risk from exposure to solar UVR, as their daily activities constantly expose them to this radiation source. A study was carried out in Valencia, Spain, in summer 2012 and involved a group of 11 workers for a period of six 2‐day recordings. Sensitive spore‐film filter‐type personal dosimeters (VioSpor) were used to measure erythemal UVR received by environmental agents in the course of their daily work. Median 2‐day UV exposure was 6.2 standard erythema dose (SED), with 1 SED defined as effective 100 J m?2 when weighted with the Commission Internationale de L′Eclairage's (CIE) erythemal response function. These workers were found to receive a median of 8.3% total daily ambient ultraviolet erythemal radiation. Comparison with the occupational UV exposure limit showed that the subjects had received an erythemal UV dose in excess of occupational guidelines, indicating that protective measures against this risk are highly advisable. 相似文献
996.
Carmen A. Mak Sara Ranjbar Paola Riente Carles Rodríguez-Escrich Miquel A. Pericàs 《Tetrahedron》2014
Two hybrid magnetic materials have been prepared from κ-carrageenan and Fe3O4 nanoparticles and tested as catalysts for the Michael addition of aldehydes to nitroalkenes. Remarkably, the material prepared from unmodified κ-carrageenan showed catalytic activity in the reaction of choice, while the individual components were inactive. This points out to a synergistic effect between the MNPs and κ-carrageenan. The second catalyst, bearing a diphenylprolinol silyl ether moiety, was also shown to promote the reaction, giving rise to the corresponding adducts in excellent ees. After the reaction is complete, the catalysts can be conveniently retrieved by simple magnetic decantation. 相似文献
997.
Reaction of Alkynes and Azides: Not Triazoles Through Copper–Acetylides but Oxazoles Through Copper–Nitrene Intermediates 下载免费PDF全文
Dr. Estela Haldón Dr. Maria Besora Dr. Israel Cano Dr. Xacobe C. Cambeiro Prof. Miquel A. Pericàs Prof. Feliu Maseras Prof. M. Carmen Nicasio Prof. Pedro J. Pérez 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(12):3463-3474
Well‐defined copper(I) complexes of composition [Tpm*,BrCu(NCMe)]BF4 (Tpm*,Br=tris(3,5‐dimethyl‐4‐bromo‐pyrazolyl)methane) or [Tpa*Cu]PF6 (Tpa*=tris(3,5‐dimethyl‐pyrazolylmethyl)amine) catalyze the formation of 2,5‐disubstituted oxazoles from carbonyl azides and terminal alkynes in a direct manner. This process represents a novel procedure for the synthesis of this valuable heterocycle from readily available starting materials, leading exclusively to the 2,5‐isomer, attesting to a completely regioselective transformation. Experimental evidence and computational studies have allowed the proposal of a reaction mechanism based on the initial formation of a copper–acyl nitrene species, in contrast to the well‐known mechanism for the copper‐catalyzed alkyne and azide cycloaddition reactions (CuAAC) that is triggered by the formation of a copper–acetylide complex. 相似文献
998.
Enantioselective Continuous‐Flow Production of 3‐Indolylmethanamines Mediated by an Immobilized Phosphoric Acid Catalyst 下载免费PDF全文
Laura Osorio‐Planes Dr. Carles Rodríguez‐Escrich Prof. Dr. Miquel A. Pericàs 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(8):2367-2372
A polystyrene‐supported 1,1’‐bi‐2‐naphthol derived phosphoric acid has been synthesized and applied in the enantioselective Friedel–Crafts reaction of indoles and sulfonylimines. The immobilized catalyst was highly active and selective, and gave rise to a broad range of 3‐indolylmethanamines (19 examples) in high yields and excellent enantioselectivities (up to 98 % enantiomeric excess) after short reaction times under very convenient reaction conditions (RT in dichloromethane). Moreover, repeated recycling (14 cycles) was possible with no substantial loss in catalytic performance and the system could be adapted to a continuous‐flow operation (6 h). Finally, the applicability of the system was further confirmed by rapid access to a library of compounds with three points of diversity in a single continuous‐flow experiment that involved sequential pumping of different substrate combinations. 相似文献
999.
The Synthesis of Functionalised Diaryltetraynes and Their Transport Properties in Single‐Molecule Junctions 下载免费PDF全文
Dr. Murat Gulcur Dr. Pavel Moreno‐García Xiaotao Zhao Masoud Baghernejad Dr. Andrei S. Batsanov Dr. Wenjing Hong Prof. Martin R. Bryce Prof. Thomas Wandlowski 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(16):4653-4660
The synthesis and characterisation is described of six diaryltetrayne derivatives [Ar‐(C?C)4‐Ar] with Ar=4‐NO2‐C6H4‐ ( NO24 ), 4‐NH(Me)C6H4‐ ( NHMe4 ), 4‐NMe2C6H4‐ ( NMe24 ), 4‐NH2‐(2,6‐dimethyl)C6H4‐ ( DMeNH24 ), 5‐indolyl ( IN4 ) and 5‐benzothienyl ( BTh4 ). X‐ray molecular structures are reported for NO24 , NHMe4 , DMeNH24 , IN4 and BTh4 . The stability of the tetraynes has been assessed under ambient laboratory conditions (20 °C, daylight and in air): NO24 and BTh4 are stable for at least six months without observable decomposition, whereas NHMe4 , NMe24 , DMeNH24 and IN4 decompose within a few hours or days. The derivative DMeNH24 , with ortho‐methyl groups partially shielding the tetrayne backbone, is considerably more stable than the parent compound with Ar=4‐NH2C6H4 ( NH24 ). The ability of the stable tetraynes to anchor in Au|molecule|Au junctions is reported. Scanning‐tunnelling‐microscopy break junction (STM‐BJ) and mechanically controllable break junction (MCBJ) techniques are employed to investigate single‐molecule conductance characteristics. 相似文献
1000.
Dr. Paola Riente Alba Matas Adams Dr. Josep Albero Prof. Emilio Palomares Prof. Miquel A. Pericàs 《Angewandte Chemie (International ed. in English)》2014,53(36):9613-9616
The development of enantioselective catalytic processes that make use of sunlight as the energy source and nontoxic, affordable materials as catalysts represents one of the new and rapidly evolving areas in chemical research. The direct asymmetric α‐alkylation of aldehydes with α‐bromocarbonyl compounds can be successfully achieved by combining bismuth‐based materials as low‐band‐gap photocatalysts with the second‐generation MacMillan imidazolidinone as the chiral catalyst and simulated sunlight as a low‐cost and clean energy source. This reaction also proceeded with high efficiency when the reaction vial was exposed to the morning sunlight on a clear September day in Tarragona, Spain. 相似文献