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961.
Sasaki K Nakagawa H Zhang X Sakurai S Kano K Kuroda Y 《Chemical communications (Cambridge, England)》2004,(4):408-409
A new host porphyrin bearing four permethyl-beta-cyclodextrin moieties for multi-porphyrin assembly forms a unique 2 : 2 assembly with the tetra-anion of tetrakis(p-sulfonylphenyl)porphyrin (TPPS) in aqueous solution. 相似文献
962.
Hydrogen dynamics in one-dimensional hydrogen bonded organic antiferroelectric, co-crystal of 5,5’-dimethyl-2,2’-bipyridine (55DMBP) and chloranilic acid (H2ca), was investigated by use of 2H high resolution solid-state NMR. The two types of hydrogen bonds O-H …N and N+-H …O? in the antiferroelectric phase were clearly observed as the splitting of the side band of the 2H MAS NMR spectra of the acid-proton deuterated compound 55DMBP-D 2ca. The temperature dependence of the spin-lattice relaxation time was measured of the N+-H and O-H deuterons, respectively. It was suggested that the motion of the O-H deuteron is already in the antiferroelectric phase in the fast-motion regime in the NMR time scale, while that of the N+-H deuteron is a slow motion. In the high-temperature paraelectric phase, the both deuterons become equivalent and the fast motion of the deuterons in the NMR time scale is taking place with the activation energy of 7.9 kJ mol?1. 相似文献
963.
RhI‐Catalyzed Intramolecular Carbonylative C−H/C−I Coupling of 2‐Iodobiphenyls Using Furfural as a Carbonyl Source
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Takuma Furusawa Prof. Dr. Tsumoru Morimoto Dr. Yasuhiro Nishiyama Dr. Hiroki Tanimoto Prof. Dr. Kiyomi Kakiuchi 《化学:亚洲杂志》2016,11(16):2312-2315
Synthesis of fluoren‐9‐ones by a Rh‐catalyzed intramolecular C?H/C?I carbonylative coupling of 2‐iodobiphenyls using furfural as a carbonyl source is presented. The findings indicate that the rate‐determining step is not a C?H bond cleavage but, rather, the oxidative addition of the C?I bond to a RhI center. 相似文献
964.
Organocatalytic Enantioselective Nucleophilic Alkynylation of Allyl Fluorides Affording Chiral Skipped Ene‐ynes
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Satoshi Okusu Hiroki Okazaki Etsuko Tokunaga Prof. Vadim A. Soloshonok Prof. Norio Shibata 《Angewandte Chemie (International ed. in English)》2016,55(23):6744-6748
Asymmetric methods for preparation of chiral alkynyl‐containing compounds are in extremely high demand in many sectors of chemical research. In this work, we report the discovery of a general organocatalytic enantioselective alkynylation based on the idea of Si/F activation of the allylic C?F bond. This approach features reasonably broad substrate scope, functional group tolerance, and relatively neutral, mild, and operationally convenient reaction conditions; all of which bode well for the synthetic value of the discovered method. In particular, this method provides unique chiral skipped 1,4‐ene‐ynes having two kinds of versatile functional groups. 相似文献
965.
Urbano França Hiroki Sayama Colin Mcswiggen Roozbeh Daneshvar Yaneer Bar‐Yam 《Complexity》2016,21(6):280-287
Describing the dynamics of a city is a crucial step to both understanding the human activity in urban environments and to planning and designing cities accordingly. Here, we describe the collective dynamics of New York City (NYC) and surrounding areas as seen through the lens of Twitter usage. In particular, we observe and quantify the patterns that emerge naturally from the hourly activities in different areas of NYC, and discuss how they can be used to understand the urban areas. Using a dataset that includes more than 6 million geolocated Twitter messages we construct a movie of the geographic density of tweets. We observe the diurnal “heartbeat” of the NYC area. The largest scale dynamics are the waking and sleeping cycle and commuting from residential communities to office areas in Manhattan. Hourly dynamics reflect the interplay of commuting, work and leisure, including whether people are preoccupied with other activities or actively using Twitter. Differences between weekday and weekend dynamics point to changes in when people wake and sleep, and engage in social activities. We show that by measuring the average distances to a central location one can quantify the weekly differences and the shift in behavior during weekends. We also identify locations and times of high Twitter activity that occur because of specific activities. These include early morning high levels of traffic as people arrive and wait at air transportation hubs, and on Sunday at the Meadowlands Sports Complex and Statue of Liberty. We analyze the role of particular individuals where they have large impacts on overall Twitter activity. Our analysis points to the opportunity to develop insight into both geographic social dynamics and attention through social media analysis. © 2015 Wiley Periodicals, Inc. Complexity 21: 280–287, 2016 相似文献
966.
Ishigami N Ago H Imamoto K Tsuji M Iakoubovskii K Minami N 《Journal of the American Chemical Society》2008,130(30):9918-9924
On single-crystal substrates, such as sapphire (alpha-Al 2O 3) and quartz (SiO 2), single-walled carbon nanotubes (SWNTs) align along specific crystallographic axes of the crystal, indicating that the SWNT growth is influenced by the crystal surface. Here, we show that not only the orientation, but also the diameter and chirality of SWNTs are affected by the crystal plane of the sapphire substrate. The aligned SWNTs grown on the A- and R-planes of sapphire have narrower diameter distributions than randomly oriented tubes produced on the C-plane sapphire and amorphous SiO 2. Photoluminescence measurements reveal a striking difference between the aligned SWNTs: near-zigzag tubes are observed on the A-plane and near-armchair tubes on the R-plane. This study shows the route for the diameter and chirality control of SWNTs by surface atomic arrangements of a single-crystal substrate. 相似文献
967.
Dr. Hideaki Takano Hitomi Katsuyama Dr. Hiroki Hayashi Miyu Harukawa Makoto Tsurui Dr. Sunao Shoji Prof. Yasuchika Hasegawa Prof. Satoshi Maeda Prof. Tsuyoshi Mita 《Angewandte Chemie (International ed. in English)》2023,62(23):e202303435
[1.1.1]Propellane, which is structurally simple and compact, exhibits promising potential for the synthesis of disubstituted straight-shaped bicyclo[1.1.1]pentane (BCP) compounds by manipulation of its highly reactive internal C−C bond. BCPs are considered to be isosteres of 1,4-disubstituted benzenes, which have found broad applications in the areas of functional molecules and drug discovery. The internal C−C single bond of [1.1.1]propellane is regarded as a charge-shift bond, which can be readily cleaved by radical means to construct BCPs. We herein report a novel synthetic method for (un)symmetric diphosphines based on the BCP motif, which can be interpreted as isosteres of 1,4-bis(diphenylphosphino)benzenes. The obtained BCP-diphosphine derivatives were used to generate a straight-shaped Au complex and an Eu-based coordination polymer. 相似文献
968.
969.
Kon H Tsuge K Imamura T Sasaki Y Ishizaka S Kitamura N Kato M 《Dalton transactions (Cambridge, England : 2003)》2008,(12):1541-1543
The direction of excitation energy migration is reversed in a system composed of {Ru(bpy)(2)}-{pyridylporphyrin}(2) by the addition of a Zn(2+) ion. The Zn(2+) system shows an excitation-wavelength dependent emission. 相似文献
970.
Intermolecular radical thiophosphination of terminal alkynes with alkylthio- and arylthiophosphines affords 1-thio-2-phosphino-1-alkenes in good yields. The addition reaction proceeds predominantly in an anti fashion to yield E isomers. 相似文献