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71.
Transition probabilities were evaluated for the X (1)Sigma(+)-A (1)Pi system of AlNC and AlCN isomers to analyze photoabsorption and fluorescence spectra. The global potential energy surfaces (PESs) of the X (1)Sigma(+) and A (1)Pi (1 (1)A("),2 (1)A(')) electronic states were determined by the multireference configuration interaction calculations with the Davidson correction. Einstein's B coefficients were computed by quantum vibrational calculations using the three-dimensional PESs of these states and the electronic transition moments for the X-1 (1)A(") and X-2 (1)A(') systems. Einstein's B coefficients obtained for AlNC or AlCN exhibit that the Al-N or Al-C stretching mode is strongly enhanced in the transition. The absorption and fluorescence spectra calculated for the X-1 (1)A(") and X-2 (1)A(') systems are discussed comparing with the observed photoexcitation and fluorescence spectra. The lifetimes for the several vibrational levels of the A (1)Pi state were calculated to be ca. 7 ns for AlNC and 21-24 ns for AlCN from the fluorescence decay rates of the 1 (1)A(")-X and 2 (1)A(')-X emissions. 相似文献
72.
Masaki Oba Yoichiro Maruyama Katsuaki Akaoka Masabumi Miyabe Ikuo Wakaida 《Applied Physics A: Materials Science & Processing》2010,101(3):545-549
Emission characteristics of gadolinium (Gd) oxide are studied, using ns and fs laser pulses for ablation in double-pulse laser
induced breakdown spectroscopy (LIBS). In the current conditions of pulse energy and signal detection timing, emission intensity
enhancement in the reheating mode is 25-fold, but little effect can be observed in a pre-pulse mode. It is shown that the
optimum focus position of the ablation pulse is about 5 mm apart from the sample surface in the reheating mode. Although little
emission can be observed in the single-pulse configuration with fs ablation pulses, the intense emission can be observed in
the reheating mode in the double-pulse configuration. 相似文献
73.
We introduce a new condition for {Yτn} to have the same asymptotic distribution that {Yn} has, where {Yn} is a sequence of random elements of a metric space (S, d) and {τn} is a sequence of random indices. The condition on {Yn} is that maxiDnd(Yi, Yan)→p0 as n → ∞, where Dn = {i: |ki−kan| ≤ δankan} and {δn} is a nonincreasing sequence of positive numbers. The condition on {τn} is that P(|(kτn/kan)−1| > δan) → 0 as n → ∞. Under these conditions, we will show that d(Yτn, Yan) → P0 and apply this result to the CLT for a general class of sequences of dependent random variables. 相似文献
74.
Ikuo Ueta Ayako Mizuguchi Koji Fujimura Susumu Kawakubo Yoshihiro Saito 《Analytica chimica acta》2012
A novel needle-type sample preparation device was developed for the effective preconcentration of volatile organic compounds (VOCs) in indoor air before gas chromatography–mass spectrometry (GC–MS) analysis. To develop a device for extracting a wide range of VOCs typically found in indoor air, several types of particulate sorbents were tested as the extraction medium in the needle-type extraction device. To determine the content of these VOCs, air samples were collected for 30 min with the packed sorbent(s) in the extraction needle, and the extracted VOCs were thermally desorbed in a GC injection port by the direct insertion of the needle. A double-bed sorbent consisting of a needle packed with divinylbenzene and activated carbon particles exhibited excellent extraction and desorption performance and adequate extraction capacity for all the investigated VOCs. The results also clearly demonstrated that the proposed sample preparation method is a more rapid, simpler extraction/desorption technique than traditional sample preparation methods. 相似文献
75.
Transition probabilities were evaluated for the X (1)A(1)-A (1)B(1) and A (1)B(1)-B (1)A(1) systems of GeH(2) and GeD(2) to analyze the X-->A-->B photoexcitation. Franck-Condon factors (FCFs) and Einstein's B coefficients were computed by quantum vibrational calculations using the three-dimensional potential energy surfaces (PESs) of the X (1)A(1), A (1)B(1), and B (1)A(1) electronic states and the transition dipole moments for the X-A and A-B systems. The global PESs were determined by the multireference configuration interaction calculations with the Davidson correction and the interpolant moving least squares method combined with the Shepard [Proceedings of the 1968 23rd ACM National Conference (ACM, New York, 1968)] interpolation. The barriers to linearity correcting the spin-orbit interaction are evaluated to be 22,000 cm(-1) for the X state, 6300 cm(-1) for the A state, and 560 cm(-1) for the B state. The obtained FCFs for the X-A and A-B systems indicate that the bending mode is strongly enhanced in the excitation since the equilibrium bond angle greatly varies within the three states. The photoexcitation and fluorescence spectra calculated for the X-A system agree well with the observed spectra. The theoretical lifetimes for lower vibrational levels of the A and B states were calculated from the fluorescence decay rates for the A-X, B-A, and B-X emissions, and the lifetimes for the A state are in good agreement with the observed values except those affected by predissociation. 相似文献
76.
The structures of propene and 3,3,3-trifluoropropene have been studied by electron diffraction intensities measured in the present study and rotational constants reported in the literature. The following average structures have been determined: For propene, rg(CC) = 1.342 ± 0.002 Å, rg(C-C) = 1.506 ± 0.003 Å, rg(C-H)vinyl = 1.104 ± 0.010 Å, rg(C-H)methyl = 1.117 ± 0.008 Å, ∠(C-CC) = 124.3 ± 0.4°, ∠(CC-H) = 121.3 ± 1.4°, and ∠(C-C-H) = 110.7 ± 0.9°; for trifluoropropene, rg(CC) = 1.318 ± 0.008 Å, rg(C-C) = 1.495 ± 0.006 Å, rg(C-H)= 1.100 ± 0.018 Å, rg(C-F) = 1.347 ± 0.003 Å, ∠(C-CC) = 125.8 + 1.1°, ∠(C-C-F) = 112.0 ± 0.2°, where the valence angles refer to the rav structure, and the uncertainties represent estimated limits of experimental error. A simple set of quadratic force constants for each molecule has been estimated. Regular trends have been observed in the CC and C-C bond distances and the C-CC angles in these and related molecules. Significant differences between the CC, C-C and C-F distances and the C-C-F angle in trifluoropropene and in hexafluoroisobutene reported by Hilderbrandt et al. have been indicated. 相似文献
77.
Yoshio Hamashima Sadao Yamamoto Tadatoshi Kubota Katsuya Tokura Koji Ishikura Kyogi Minami Fumihiko Matsubara Masaaki Yamaguchi Ikuo Kikkawa Wataru Nagata 《Tetrahedron letters》1979,20(51):4947-4950
Synthesis of optically active 3′-nor-type 1-oxacephems from 6-APA was described. -Nitrobenzyl 7β-amino-3-chloro-7α-methoxy-1-oxa-3-cephem-4-carboxylate was also prepared. 相似文献
78.
An enolate-imine condensation using the lithium dianion of 3-hydroxy-butanoate and N-acylaldimines gave the key intermediate for the preparation of (+)-thienamycin with improved stereoselection in the presence of lithium chloride. 相似文献
79.
Yamashita M Ohta N Shimizu T Matsumoto K Matsuura Y Kawasaki I Tanaka T Maezaki N Ohta S 《The Journal of organic chemistry》2003,68(4):1216-1224
The first total synthesis of (+/-)-Linderol A, a hexahydrodibenzofuran constituent of Lindera umbellata bark, with potent inhibitory activity on the melanin biosynthesis of cultured B-16 melanoma cells, was achieved through 19 steps of reaction in 6.6% overall yield, in which the critical step was a tandem reaction of a 3-ethoxycarbonylcoumarin derivative with dimethylsulfoxonium methylide to yield the 2-ethoxycarbonylcyclopenta[b]benzofuran-3-ol derivative. 相似文献
80.
Phospholipase D (EC 3.1.4.4.) and choline oxidase (EC 1.1.99.1.) are immobilized together on a hydrophobic agarose gel and used to convert the phospholipid to betaine and hydrogen peroxide, which is measured amperometrically at + 0.60 V vs. SCE. The response time of the sensor is 2 min, and the calibration curve for 0–3 g l-1 of phosphatidyl choline is linear. Different methods of insolubilizing the enzymes are compared. 相似文献