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991.
Summary A cerebroside fraction was obtained from the fruit bodies offomitopsis pinicola using column chromatography and then separated into six compounds by reversed-phase HPLC. The sugar component of all cerebrosides wasD-glucose. The major fatty acids were 2-hydroxyfatty acids (C14–C18), the long chain base was identified as 9-methyl-C18-4,8-sphingadienine which is widely distributed in fungi and reported to be essential for the fruit-inducing activity of fungi. Based on degradation studies, fast atom bombardment mass spectrometry, and different1H and13C NMR investigations, the structure of the main cerebroside (1) was determined to be (4E,8E,2S,3R,2R)-N-2-hydroxypalmityl-1-O--D-glucopyranosyl-9-methyl-4,8-sphingadienine.
Cerebroside ausFomitopsis pinicola (Sw. Ex Fr.) Karst.
Zusammenfassung Aus den Fruchtkörpern vonfomitopsis pinicola wurde ein Cerebrosidgemisch erhalten und durch Säulenchromatographie und HPLC in sechs Verbindungen aufgetrennt. Der Zuckerbaustein aller Cerebroside warD-Glucose. Die Fettsäurekomponenten waren 2-Hydroxyfettsäuren mit einer Kettenlänge zwische C14 und C18. Der Basenteil konnte als 9-Methyl-C18-4,8-sphingadienin identifiziert werden. Diese Verbindung ist in Pilzen weit verbreitet und für die Fruchtbildung verantwortlich. Aus Abbaustudien, FAB-MS und verschiedenen1H- und13C-NMR-Messungen wurde die Struktur des Hauptcerebrosids (1) als (4E,8E,2S,3R,2R)-N-2-hydroxypalmityl-1-O--D-glucopyranosyl-9-methyl-4,8-sphingadienin ermittelt.相似文献
992.
Xiao‐Yan Chen Peng Cheng Shi‐Ping Yan Dai‐Zheng Liao Zong‐Hui Jiang 《无机化学与普通化学杂志》2005,631(15):3104-3107
A novel two‐dimensional cobalt complex, [Co(btrm)2(dca)]ClO4 ( 1 , btrm = 1,2‐bis(1,2,4‐triazole‐1‐yl)methane, dca = dicyanamide), was synthesized and characterized. X‐ray diffraction analyses reveal that the title complex crystallizes in the monoclinic space group C2/m with a = 29.507(13)Å, b = 17.804(8) Å, c = 14.709(7) Å, β = 119.916(7)°, Z = 12, and R1 = 0.0784, wR2 = 0.2041. The cobalt atom involves a six‐coordinated CoN6 environment, with a distorted octahedral coordination. Two btrm ligands connect the CoII atoms with the exodentate nitrogen atoms on the 4‐position of triazole rings to form a sixteen‐membered rhombic grid. The unprecedented double btrm bridges and μ1,5‐dca bridge connect the cobalt atoms to form a two‐dimensional grid‐like layered structure. The spectroscopic and magnetic properties have also been investigated. 相似文献
993.
Two methods are proposed, one for the location of saddle points and one for the calculation of steepest-descent paths on multidimensional surfaces. Both methods are based on a constrained simplex optimization technique that avoids the evaluation of gradients or second derivative matrices. Three chemical reactions of increasing structural complexity are studied within the PRDDO SCF approximation. Predicted properties of reaction hypersurfaces are in good overall agreement with those determined by gradient minimization and gradient following algorithms in connection with various ab initio SCF methods. Computational efforts required by the new procedures are discussed. 相似文献
994.
Zheng-Ping Yi Jun Hu Hui-Lan Chen 《Journal of inclusion phenomena and macrocyclic chemistry》2003,45(1-2):1-8
Conformational analysis of inclusion complexes of sodium 3-hydroxy-2-naphthalenecarboxylate with -cyclodextrin and heptakis-(2,3,6-tri-o-methyl)--cyclodextrin in D2O was investigated by 1D and 2D 1HNMR measurements. The results show that part of the naphthyl group of sodium 3-hydroxy-2-naphthalenecarboxylate is situated in the 2,3-OH side of the -cyclodextrin cavity asymmetrically while the whole naphthyl group is included in the heptakis-(2,3,6-tri-o-methyl)--cyclodextrin cavity with the caboxylate and hydroxy group close to the 6-OCH3 group. 相似文献
995.
Density functional theory calculations were carried out for the title reactions. Ethylene oxide and methylamine were adopted as reactants. Amine clusters (dimer, trimer, tetramer, and pentamer) were considered, because the combination of one oxide and one amine molecule gave a large activation energy. An amine tetramer was found to react favorably with the oxide via various zwitterionic intermediates. A back-side S(N)2 nucleophilic attack of one amine and the subsequent proton relay up to the front side provide a stabilized reaction field. The amine-alcohol mixed reactant may react readily with the oxide, because the alcoholic O-H group is in contact with the oxide oxygen with the strong hydrogen-bond stabilization. 相似文献
996.
T. V. Magdesieva I. I. Kukhareva D. P. Krut'ko G. A. Artamkina K. P. Butin I. P. Beletskaya 《Russian Chemical Bulletin》1994,43(5):881-883
Interaction of the 5-cyclopentadienyldicarbonyliron(II) anion with pentafluorobenzoyl chloride affords C6F5COFe(CO)2Cp, CpFe(CO)2C6F4COFe(CO)2Cp, and CpFe(CO)2C6F4C6F4Fe(CO)2Cp. The reaction products are characterized by1H,13C and19F NMR spectra.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 935–937, May, 1994. 相似文献
997.
The complete gene coding for human neutrophilactivating protein-1/interleukin-8 was synthesized using a semi-chemical semi-enzymatic method. The synthetic gene was then overexpressed in Escherichia coli under the temperature-regulated control of the P_RP_L tandem promoters. As determined by SDS-PAGE and densitometry, the overexpressed protein comprised up to 18.5% and 10.9% of the total soluble protein in E. coli cells grown in shake flasks and in batch fermentation, respectively. The recombinant NAP-1/IL-8 was then purified to>95% homogeneity by gel filtration and cation exchange chromatography. The purified protein appeared as a single band on the SDS-PAGE gel and possessed potent chemotactic activity in the concentration of <10 ng/ml, as assayed by the agarose plate method. An early skin reactivity was also observed when the pure NAP-1/IL-8 was injected subcutaneously into the rabbits. The N-terminal 36 amino acid sequence of the recombinant NAP1/IL-8 was determined using the Edman method and was sho 相似文献
998.
The banded texture in films prepared from nematic poly (1,4-benzamide) (PBA)/H_2SO_4 solution by shearing and without shearing has been studied by using microscopy techniques. The kinetic parameters of banded texture formation γ_c and τ_b were measured for nematic solution of PBA by using parallel-plate shearing apparatus. The banded texture was also observed in randomly packed domains for nematic solution of PBA on standing without shearing. The properties of banded texture show no difference between the two samples with or without shearing. 相似文献
999.
Y. Akishige H. Shigematsu T. Tojo H. Kawaji T. Atake 《Journal of Thermal Analysis and Calorimetry》2005,81(3):537-540
Summary Specific heats on the single crystals of Sr2Nb2O7, Sr2Ta2O7 and (Sr1-xBax)2Nb2O7 were measured in a wide temperature range of 2-600 K. Heat anomalies of a λ-type were observed at the incommensurate phase transition of TINC (=495 K) on Sr2Nb2O7 and at the super-lattice phase transition of TSL (=443 K) on Sr2Ta2O7; the transition enthalpies and the transition entropies were estimated. Furthermore, a small heat anomaly was observed at the low temperature ferroelectric phase transition of TLOW (=95 K) on Sr2Nb2O7. The transition temperature TLOW decreases with increasing Ba content x and it vanishes for samples of x>2%. 相似文献
1000.
Enduracidin and ramoplanin belong to the large family of cyclodepsipeptide antibiotics, highly effective against Gram-positive bacteria. The primary and 3D solution structure of ramoplanin is already well known, and the primary structure of enduracidin has been determined by a combination of chemical and NMR spectroscopic methods. Both antibiotics share a similar peptide core of 17 amino acids and differ mainly in the length of the acyl chain and the presence of two D-mannose moieties in ramoplanin. Based on the high sequence homology with ramoplanin, the structure in solution of enduracidin is modeled as a cyclic peptide. The tertiary structure thus obtained was refined through molecular dynamics (MD) simulation, in which the interatomic NOE-derived distance restraints were imposed. MD simulations yielded a family of representative 3D structures (RMSD = 0.89), which highlighted a backbone geometry similar to that of ramoplanin in its beta-hairpin arrangement. In contrast, enduracidin displays a different arrangement of the side-chain and of the residues forming the hydrophobic core. 相似文献