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41.
Ronald C. Crouch Jeffrey G. Raab Marius Pelmuş Evgeny Tischenko Michael Frey Alexei V. Buevich Mikhail Reibarkh R. Thomas Williamson Gary E. Martin 《Magnetic resonance in chemistry : MRC》2022,60(2):210-220
Modification of the recently reported 19F-detected 1,1-ADEQUATE experiment that incorporates dual-optimization to selectively invert a wide range of 1JCC correlations in a 1,n-ADEQUATE experiment is reported. Parameters for the dual-optimization segment of the pulse sequence were modified to accommodate the increased size of 1JCC homonuclear coupling constants of poly- and perfluorinated molecules relative to protonated molecules to allow broadband inversion of the 1JCC correlations. The observation and utility of isotope shifts are reported for the first time for 1,1- and 1,n-ADEQUATE correlations. 相似文献
42.
A.B. Sow 《Stochastics An International Journal of Probability and Stochastic Processes》2013,85(5):429-477
Using a forward–backward stochastic differential equations (FBSDE) associated to a transmutation process driven by a finite sequence of Poisson processes, we obtain a probabilistic interpretation for a non-degenerate system of quasilinear parabolic partial differential equations (PDEs). The novetly is that the linear second order differential operator is different on each line of the system. 相似文献
43.
44.
Chengye Yuan Shusen Li Zhiyi Cheng 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-2):95-102
Abstract The mass spectra of 2-alkyl-2-oxo-1,3,2-dioxa-phosphorinane and-phosphepane showed that the ring opening was in competition with the cleavage of the P[sbnd]C bond. According to the fragmentation pathway, which was dependent on the structure of exocyclic substituents on phosphorus, the 2-alkyl-2-oxo-1,3,2-di-oxa-phosphorinanes can be classified in two categories. The main process in category A was the ring opening and/or C[sbnd]C bond cleavage. While in category B the cleavage of P[sbnd]C bond was predominant. However, for 2-alkyl-2-oxo-1,3,2-dioxa-phosphepane. no matter how the structure of 2-alkyl group was, the ring opening was a dominant process. 相似文献
45.
Na'il Saleh Mohammed A. Meetani Leena Al-Kaabi Indrajit Ghosh 《Supramolecular chemistry》2013,25(9):650-656
The supramolecular interactions of the ocular drug tropicamide (TR) with cucurbit[7]uril (CB7) and cucurbit[8]uril (CB8) were investigated in aqueous solutions by using 1H NMR, ESI-MS and UV–vis spectroscopic techniques. The results indicate a 1:1 binding stoichiometry of TR with CB7 and CB8. The binding constants of TR in its protonated form were higher (e.g. K = 4 × 106 M? 1 with CB8) than in its neutral form (e.g. K = 1.4 × 104 M? 1 with CB8), which led to a complexation-induced increase in its pK a value of ca. 0.5 and 2 units with CB7 and CB8, respectively. In the presence of about 1% (w/v) CB8, the ionisation degree of 0.1% (w/v) TR was increased from 2% to 62% at neutral pH. The increase in the pK a value and thus stabilisation of the protonated TR species at neutral pH is discussed in the context of supramolecular drug delivery of ophthalmologic drugs. 相似文献
46.
Andrea Frank Andreas Berkefeld Matthias Drexler Heiko M. Mller Thomas E. Exner 《International journal of quantum chemistry》2013,113(13):1787-1793
Neutral Ni(II) complexes have been shown to be highly valuable as robust and versatile catalysts in olefin polymerization. But they show reduced reactivity when the polar monomers methyl acrylate and vinyl acetate are incorporated. To get further insight into this behavior, NMR chemical shift calculations were performed on the system [(N,O) Ni (H) (PMe3)] 1 (N,O = ‐N,O‐{2,6‐(3,5‐(F3C)2C6H3)2C6H3) NC(H)‐3,5‐I2‐2‐O‐C6H2}). The chemical shifts show reasonable agreement with experiment but are also extremely influenced by geometrical features of the complex as well as the inserted substrate. The first prominent feature, the low‐field shift of the Ccarbonyl in the incorporated monomer, can only be reproduced when it is in close proximity to the Ni and in this way hinders the attack of a new monomer. Second, the almost 100 ppm difference in the chemical shift of the carbon of the two substrates directly bound to Ni can be reasoned by the different directionality of polarization as disclosed by natural bond orbital (NBO) analysis. © 2013 Wiley Periodicals, Inc. 相似文献
47.
Dr. Fu Chen Dr. Guibin Ma Dr. Guy M. Bernard Prof. Roderick E. Wasylishen Prof. Ronald G. Cavell Dr. Robert McDonald Dr. Michael J. Ferguson 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(8):2826-2838
Several 1:1 adducts of gallium trihalides with triarylphosphines, X3Ga(PR3) (X=Cl, Br, and I; PR3=triarylphosphine ligand), were investigated by using solid‐state 69/71Ga and 31P NMR spectroscopy at different magnetic‐field strengths. The 69/71Ga nuclear quadrupolar coupling parameters, as well as the gallium and phosphorus magnetic shielding tensors, were determined. The magnitude of the 71Ga quadrupolar coupling constants (CQ(71Ga)) range from approximately 0.9 to 11.0 MHz . The spans of the gallium magnetic shielding tensors for these complexes, δ11?δ33, range from approximately 30 to 380 ppm; those determined for phosphorus range from 10 to 40 ppm. For any given phosphine ligand, the gallium nuclei are most shielded for X=I and least shielded for X=Cl, a trend previously observed for InIII–phosphine complexes. This experimental trend, attributed to spin‐orbit effects of the halogen ligands, is reproduced by DFT calculations. The signs of CQ(69/71Ga) for some of the adducts were determined from the analysis of the 31P NMR spectra acquired with magic angle spinning (MAS). The 1J(69/71Ga,31P) and ΔJ(69/71Ga, 31P) values, as well as their signs, were also determined; values of 1J(71Ga,31P) range from approximately 380 to 1590 Hz. Values of 1J(69/71Ga,31P) and ΔJ(69/71Ga,31P) calculated by using DFT have comparable magnitudes and generally reproduce experimental trends. Both the Fermi‐contact and spin‐dipolar Fermi‐contact mechanisms make important contributions to the 1J(69/71Ga,31P) tensors. The 31P NMR spectra of several adducts in solution, obtained as a function of temperature, are contrasted with those obtained in the solid state. Finally, to complement the analysis of NMR spectra for these adducts, single‐crystal X‐ray diffraction data for Br3Ga[P(p‐Anis)3] and I3Ga[P(p‐Anis)3] were obtained. 相似文献
48.
49.
Henry A. Nkabyo D. Hannekom Jean McKenzie 《Journal of Coordination Chemistry》2014,67(23-24):4039-4060
Irradiation cis-[M(Ln-S,O)2] complexes (M = PtII, PdII) derived from N,N-dialkyl-N′-benzoylthioureas (HLn) with various sources of intense visible polychromatic or monochromatic light with λ < 500 nm leads to light-induced cis?→?trans isomerization in organic solvents. In all cases, white light derived from several sources or monochromatic blue-violet laser 405 nm light, efficiently results in substantial amounts of the trans isomer appearing in solution, as shown by 1H NMR and/or reversed-phase HPLC separation in dilute solutions at room temperature. The extent and relative rates of cis/trans isomerization induced by in situ laser light (λ = 405 nm) of cis-[Pd(L2-S,O)2] was directly monitored by 1H NMR and 195Pt NMR spectroscopy of selected cis-[Pt(L-S,O)2] compounds in chloroform-d; both with and without light irradiation allows the δ(195Pt) chemical shifts cis/trans isomer pairs to be recorded. The cis/trans isomers appear to be in a photo-thermal equilibrium between the thermodynamically favored cis isomer and its trans counterpart. In the dark, the trans isomer reverts back to the cis complex in what is probably a thermal process. The light-induced cis/trans process is the key to preparing and isolating the rare trans complexes which cannot be prepared by conventional synthesis as confirmed by the first example of trans-[Pd(L-S,O)2] characterized by single-crystal X-ray diffraction, deliberately prepared after photo-induced isomerization in acetonitrile solution. 相似文献
50.
Li-Xia Wang Ben-Quan Hu Jun-Feng Xiang Jie Cui Xiang Hao Tong-Ling Liang Ya-Lin Tang 《Tetrahedron》2014
Hydrogen bonding interaction as one type of non-covalent force has proven itself to be highly efficient for constructing structurally unique artificial secondary structures. Here, the structure of Naryl-substituted anthranilamide in solution is demonstrated by various NMR technique, the intramolecular hydrogen bonds between amide attached to arylamine of the same ring is proposed, which is supported by its crystal structure in the solid phase. The substituent on the nitrogen atom of arylamine plays an important role in forming the presence of intramolecular hydrogen bonds. The chemical shift of the Naryl-H downfield changes obviously, due to the formation of intramolecular hydrogen bonds and the deshielding effect of oxygen, and the neighboring C–H is activated and shows downfield protonic signal too. The presence of intramolecular hydrogen bonds probably provides the explanation for the transformation from Naryl-substituted anthranilamide to imine, which could be converted into 2-aryl quinazolinone finally. 相似文献