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991.
Norimichi Kojima Kazuhiro Ikeda Yasuhiro Kobayashi Tatsuya Tsukuda Yuichi Negishi Genta Harada Tadashi Sugawara Makoto Seto 《Hyperfine Interactions》2012,207(1-3):127-131
We have investigated the structures and electronic states of a series of glutathionate-protected Au clusters, Au n (SG) m with n = 10 ? ~55, using 197Au Mössbauer spectroscopy, which allows us to probe the local environment of the constituent Au atoms via isomer shift (IS) and quadrupole splitting (QS). The spectral profile abruptly changes on going from Au22(SG)17 to Au25(SG)18, then it smoothly changes to that of Au~55(SG)m. However, the spectral profile dramatically changes on going from Au~55(SG)m to the dodecanethiolate-protected Au cluster with average diameter of 2 nm. The 197Au Mössbauer spectra of glutathionate-protected Au clusters and dodecanethiolate-protected Au clusters were successfully analyzed on the basis of the structure and electronic state of Au25(SG)18. 相似文献
992.
Mamoru Yasuike Ryo Usui Yasuhiro Yamada Yoshio Kobayashi 《Hyperfine Interactions》2012,205(1-3):23-26
Iron films were produced by pulsed laser deposition (PLD) of iron in Ar gas and M?ssbauer spectra of these films were obtained at room temperature. The orientation of the hyperfine magnetic field was found to vary depending on the pressure of the Ar gas. Iron films produced at low Ar pressures exhibited magnetic fields parallel to the substrate surface. The magnetic field became increasingly perpendicular to the substrate with increasing Ar pressure. Collisions with Ar gas molecules reduced the translational energies of laser-evaporated iron atoms and thus the orientation of crystals formed on the substrate varied depending on the Ar pressure. 相似文献
993.
2,4,6-Triphenylpyrylium cation encapsulated within zeolite Y promotes highly selective transformation of olefins to ketones with molecular oxygen, under visible light (lambda > 400 nm) irradiation at room temperature. 相似文献
994.
This review covers several recent topics of novel catalyst design with supported metal complexes on oxide surfaces for selective catalysis such as chiral self-dimerization to create asymmetric oxidative coupling catalysis, surface functionalization with achiral reagents to promote asymmetric catalysis, and molecular imprinting to design shape-selective catalysis. The new concepts and designs find wide applications to a variety of selective catalysts. 相似文献
995.
996.
997.
A triethylenetetramine bearing anthracene and benzophenone as a fluorescent molecular logic gate with either-or switchable dual logic functions 总被引:1,自引:0,他引:1
Nishimura G Ishizumi K Shiraishi Y Hirai T 《The journal of physical chemistry. B》2006,110(43):21596-21602
Fluorescence behaviors of a triethylenetetramine bearing anthracene (AN) and benzophenone (BP) fragments at the respective ends, L1, have been studied in water, where effects of pH (H+) and metal cations on the emission properties have been studied in detail. L1 behaves as a fluorescent molecular logic gate driven by H+ (Input1) and metal cations (Input2) as input chemicals. The most notable feature of L1 is that this molecule expresses the "either-or" switchable dual logic functions. Operation of L1 with Cu2+ as Input2 expresses the INHIBIT logic function, where a strong AN fluorescence appears only at pH 4 (with H+) without Cu2+ [Input1(1)-Input2(0)]. In contrast, operations of L1 with all other metal cations as Input2 express the TRANSFER logic function, where the presence of H+ allows strong AN fluorescence regardless of whether the metal cation exists or not [Input1(1)-Input2(0); Input1(1)-Input2(1)]. These emission switching behaviors of L1 are driven by the difference in the coordination stability between L1 and metal cations and the photoinduced intramolecular electron and energy transfer processes: (i) a pH-induced electron transfer from unprotonated nitrogen atoms of the polyamine chain to the photoexcited AN [ELT(N-->AN*)]; (ii) a pH- and metal coordination-induced electron transfer from the photoexcited AN to the ground-state BP [ELT(AN*-->BP)]; and (iii) a Cu2+ coordination-induced energy transfer from the photoexcited AN to Cu2+ [ENT(AN*-->Cu2+)]. 相似文献
998.
Hasegawa S Yoshida F Matsuoka L Koike F Fritzsche S Obara S Azuma Y Nagata T 《Physical review letters》2006,97(2):023001
We have observed K-shell and L-shell hollow beryllium atoms (2s(2)2p3s and 1s3s(2)3p) created by photoexcitation using synchrotron radiation. Resonance shapes were fitted to the Fano profile and the parameters were deduced. A Dirac-Fock calculation was performed to identify the configuration of the peaks and to predict other hollow atomic peaks. The results of the calculation were in good agreement with the experimental data. The comparison of the transition strength has revealed that the three-electron photoexcitation to the 1s3s(2)3p configuration is stronger than the two-electron photoexcitation to the 2s(2)2p3s configuration. This is attributed to the large overlap between the 2s orbital of the ground state (1s(2)2s(2)) with the orbital of the L-shell hollow state (1s3s(2)3p). 相似文献
999.
We present a general framework for finding the time-optimal evolution and the optimal Hamiltonian for a quantum system with a given set of initial and final states. Our formulation is based on the variational principle and is analogous to that for the brachistochrone in classical mechanics. We reduce the problem to a formal equation for the Hamiltonian which depends on certain constraint functions specifying the range of available Hamiltonians. For some simple examples of the constraints, we explicitly find the optimal solutions. 相似文献
1000.
Kikuchi K Tanaka Y Saihara Y Maeda M Kawamura M Ogumi Z 《Journal of colloid and interface science》2006,298(2):914-919
The hydrogen concentration of solutions supersaturated with hydrogen comprising dissolved hydrogen and hydrogen bubbles obtained through water electrolysis was studied. The rate of decrease in concentration of hydrogen nanobubble diameter below 600 nm and dissolved hydrogen with elapsed time after electrolysis was seemed to be independent of ionic strength and ion type and storage temperature. The concentration of hydrogen nanobubbles (mol dm(-3)) in electrolyzed water decreases with ionic strength, while the total hydrogen concentration remains roughly constant. The hydrogen nanobubble concentration increases in accordance with the nature of ions existing in solution in the following order I- < Br- < Cl- and K+ < Li+ < Na+. It is shown that the ratio of hydrogen nanobubble concentration to total hydrogen concentration of hydrogen in a catholyte strongly depends on the ratio in the supersaturated hydrogen solution near the electrode surface. 相似文献