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961.
Dr. Karl P. J. Gustafson Dr. Tamás Görbe Dr. Gonzalo de Gonzalo-Calvo Ning Yuan Cynthia L. Schreiber Dr. Andrey Shchukarev Dr. Cheuk-Wai Tai Prof. Dr. Ingmar Persson Prof. Dr. Xiaodong Zou Prof. Dr. Jan-E. Bäckvall 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(39):9174-9179
Herein, we report on the use a biohybrid catalyst consisting of palladium nanoparticles immobilized on cross-linked enzyme aggregates of lipase B of Candida antarctica (CalB CLEA) for the dynamic kinetic resolution (DKR) of benzylic amines. A set of amines were demonstrated to undergo an efficient DKR and the recyclability of the catalysts was studied. Extensive efforts to further elucidate the structure of the catalyst are presented. 相似文献
962.
Prof. Dr. Andrey Yu. Rogachev Melisa Alkan Dr. Jingbai Li Shuyang Liu Dr. Sarah N. Spisak Dr. Alexander S. Filatov Prof. Dr. Marina A. Petrukhina 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(62):14140-14147
One-electron reduction of corannulene, C20H10, with Li metal in diglyme resulted in crystallization of [{Li+(diglyme)2}4(C20H10.−)2(C20H10-C20H10)2−] ( 1 ), as revealed by single-crystal X-ray diffraction. This hybrid product contains two corannulene monoanion-radicals along with a dianionic dimer, crystallized with four Li+ ions wrapped by diglyme molecules. The dimeric (C20H10-C20H10)2− anion provides the first crystallographically confirmed example of spontaneous radical dimerization for C20H10.−. The C−C bond length between the two C20H10.− bowls of 1.588(5) Å is consistent with the single σ-bond character of the linker. The trans-disposition of two bowls in the centrosymmetric (C20H10-C20H10)2− dimer is observed with the torsion angle around the central C−C bond of 180°. Comprehensive theoretical analysis of formation/decomposition processes of the dimeric dianion has been carried out in order to evaluate the nature of bonding and energetics of the C20H10.− coupling. It is found that such σ-bonded dimers are thermodynamically unstable due to large preparation energy and repulsive Pauli component of the bonding, but kinetically persistent due to a high energy barrier provided by the existing spin-crossing point. 相似文献
963.
Shelby E. Stavretis Duncan H. Moseley Fan Fei Hui-Hui Cui Dr. Yongqiang Cheng Dr. Andrey A. Podlesnyak Dr. Xiaoping Wang Dr. Luke L. Daemen Dr. Christina M. Hoffmann Dr. Mykhaylo Ozerov Zhengguang Lu Prof. Komalavalli Thirunavukkuarasu Dr. Dmitry Smirnov Tieyan Chang Dr. Yu-Sheng Chen Dr. Anibal J. Ramirez-Cuesta Prof. Xue-Tai Chen Prof. Zi-Ling Xue 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(69):15846-15857
Large separations between ground and excited magnetic states in single-molecule magnets (SMMs) are desirable to reduce the likelihood of spin reversal in the molecules. Spin-phonon coupling is a process leading to magnetic relaxation. Both the reversal and coupling, making SMMs lose magnetic moments, are undesirable. However, direct determination of large magnetic states separations (>45 cm−1) is challenging, and few detailed investigations of the spin-phonon coupling have been conducted. The magnetic separation in [Co(12-crown-4)2](I3)2(12-crown-4) ( 1 ) is determined and its spin-phonon coupling is probed by inelastic neutron scattering (INS) and far-IR spectroscopy. INS, using oriented single crystals, shows a magnetic transition at 49.4(1.0) cm−1. Far-IR reveals that the magnetic transition and nearby phonons are coupled, a rarely observed phenomenon, with spin-phonon coupling constants of 1.7–2.5 cm−1. The current work spectroscopically determines the ground–excited magnetic states separation in an SMM and quantifies its spin-phonon coupling, shedding light on the process causing magnetic relaxation. 相似文献
964.
Alexandra Svyatova Dr. Ivan V. Skovpin Dr. Nikita V. Chukanov Dr. Kirill V. Kovtunov Prof. Eduard Y. Chekmenev Dr. Andrey N. Pravdivtsev Prof. Jan-Bernd Hövener Prof. Igor V. Koptyug 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(36):8465-8470
Magnetic Resonance Imaging (MRI) is a powerful non-invasive diagnostic method extensively used in biomedical studies. A significant limitation of MRI is its relatively low signal-to-noise ratio, which can be increased by hyperpolarizing nuclear spins. One promising method is Signal Amplification By Reversible Exchange (SABRE), which employs parahydrogen as a source of hyperpolarization. Recent studies demonstrated the feasibility to improve MRI sensitivity with this hyperpolarization technique. Hyperpolarized 15N nuclei in biomolecules can potentially retain their spin alignment for tens of minutes, providing an extended time window for the utilization of the hyperpolarized compounds. In this work, we demonstrate for the first time that radio-frequency-based SABRE hyperpolarization techniques can be used to obtain 15N MRI of biomolecule 1-15N-nicotinamide. Two image acquisition strategies were utilized and compared: Single Point Imaging (SPI) and Fast Low Angle SHot (FLASH). These methods demonstrated opportunities of high-field SABRE for biomedical applications. 相似文献
965.
966.
Oleg V. Bityukov Vera A. Vil George K. Sazonov Andrey S. Kirillov Nikita V. Lukashin Gennady I. Nikishin Alexander O. Terentev 《Tetrahedron letters》2019,60(13):920-924
It was discovered that the Kharasch peroxidation of barbituric acids proceeds both with a Cu-catalyst and without a metal catalyst. Despite the presence of possible thermal-initiated side oxidation pathways, α-tert-butylperoxybarbiturates were selectively prepared from substituted barbituric acids and tert-butyl hydroperoxide. 相似文献
967.
Lyubov N. Sobenina Elena F. Sagitova Marina V. Markova Igor A. Ushakov Andrey V. Ivanov Boris A. Trofimov 《Tetrahedron letters》2018,59(45):4047-4049
Acylethynylpyrroles, available via the transition metal-free coupling of pyrroles with acylhaloacetylenes are readily annelated with propargylamine in a one-pot step-wise procedure: catalyst-free heating (60–65?°C, 6–16?h) in DMSO and then keeping for 2.5?h with CuI at the same temperature. The products are pyrrolyl-pyridines isolated in good to excellent yields (56–94%). It is experimentally shown that dehydrogenation of intermediate dihydropyridine moiety is not resulted from the oxidation with DMSO (Me2S was not detected) or air (argon blanket) and is likely associated with the CuI catalysis. 相似文献
968.
Andrey S. Yasinskiy Petr V. Polyakov Yan V. Voyshel Tatiana R. Gilmanshina Sai Krishna Padamata 《Journal of Dispersion Science and Technology》2018,39(10):1492-1501
The paper describes the sedimentation behavior of concentrated high-temperature oxide-fluoride slurries with alumina particles volume fraction range 0.24?≤?φ?≤?0.32 at ~700 °C. The behavior is of interest due to perspectives of the non-Newtonian fluids usage in the future aluminium reduction technology. To characterize sedimentation behavior several techniques were used: density analysis, X-Ray diffraction, microphotography and electron scanning microscopy. Sample with ?63?µm dispersed phase as well as smelter-grade alumina which contains particles in a range of 10–150?µm has been examined. It has been found that particle settling occurs with the initial velocity 0.97·10?5 m·s?1 at φ?=?0.24 and gradually reduces reaching zero at φ close to 0.32 which was considered as a maximum packing fraction. MS?1 sedimentation mode has been identified, the type of sedimentation was found to be changed from type 1 to type 3 in the sample with φ?=?0.24. The alumina partial density distribution in suspension as a function of time was determined. Alumina average motion velocity during sedimentation was calculated to be 154·10?3?kg·m?2·s?1 at φ?=?0.24 in the top layer of the sample within the first 150?s of sedimentation. It had been reducing drastically before it reached zero after 300?s. An alumina flow was higher in the top layers. Some of the rheological properties (such as relaxation time, which increased from 7.2·10?3 to 17.7·10?3?s after the increase of φ from 0.24 to 0.28) has been determined. 相似文献
969.
Ilyas S. Nizamov Andrey A. Yakovlev Ilnar D. Nizamov Dmitriy A. Terenzhev Kamil A. Ivshin Olga N. Kataeva Marina P. Shulaeva Oscar K. Pozdeev Elvira S. Batyeva Rafael A. Cherkasov 《应用有机金属化学》2018,32(5)
Chiral S‐tributylstannyl dithiophosphates and dithiophosphonates were obtained by the reactions of optically active dithiophosphoric and dithiophosphonic acids containing (S)‐(–)‐menthyl and (R)‐(+)‐menthyl substituents with gaseous ammonia and tributyl chlorostannane. The reactions of chiral ammonium dithiophosphate containing (1R)‐endo‐(+)‐fenchyl substituent with tributyl chlorostannane or tetrachlorostannane result in corresponding S‐tributylstannyl dithiophosphate or tetrakis(dithiophosphato)stannane. Molecular structure of ammonium O,O‐di‐(–)‐menthyldithiophosphate was studied by X‐ray single crystal diffraction. Bactericidal activity of S‐tributylstannyl dithiophosphates was tested. 相似文献
970.