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941.
942.
La0.15Sr0.85Ga0.3Fe0.7O3-δ(LSGFO) and La0.15Sr0.85Co0.3Fe0.7O3-δ(LSCFO) mixed oxygen-ion and electron conducting oxides were synthesized by using a combined EDTA and citrate complexing method, and the corresponding dense membranes were fabricated. The properties of the oxide powders and membranes were characterized with combined SEM, XRD, H2-TPR, O2-TPD techniques, mechanical strength and oxygen permeation measurement. The results showed that LSGFO had much higher thermochemical stability than LSCFO due to the higher valence stability of Ga3+. After the temperature-programmed reduction by 5% H2 in Ar from 20℃to 1020℃, the basic perovskite structure of LSGFO was successfully preserved. LSGFO also favors the oxygen vacancy formation better than LSCFO. Oxygen permeation measurement demonstrated that LSGFO had higher oxygen permeation flux than LSCFO, but they had similar activation energy for oxygen transportation, with a value of 110 and 117 kJ ?mol~(-1), respectively. The difference in oxygen permeation f 相似文献
943.
Summary Tagging techniques with reagents used for fluorescent detection for short and long-chain fatty acids using high-performance
liquid chromatography are evaluated in terms of the tagging reactions, handing, flexibility, stability of the reagents. Emphasis
is given to the applications of the tagging techniques to relatively high molecular mass fatty acids. The fatty acids or carboxylic
compounds were derivatized to their corresponding esters with 9-(2-hydroxy ethyl)-carbazole (HEC) in acetonitrile at 60°C
with N, N′-carbonyldiimidazole (CDI) as a coupling agent in the presence of 4-dimethylaminopyridine (DMAP). A mixture of esters
of C1−C20 fatty acids was completely separated with 45 min using gradient elution on a reversed-phase C18 column. The maximum fluorescence emission for the derivatized fatty acids is at 365 nm (λex 293 nm). Studies on derivatization conditions indicated that fatty acids react rapidly and smoothly with HEC in the presence
of CDI and DMAP in acetonitrile to give the corresponding sensitively fluorescent derivatives. The application of this method
to the analysis of long chain fatty acids in plasma is also investigated. The LC separation shows good selectivity and reproducibility
for fatty acids derivatives. The relative standard deviations (n=6) for each fatty acid derivative are <5.0%. The detection
limits are at 38–57 fmol levels for C14−C20 fatty acids and lower levels for <C14 fatty acids. 相似文献
944.
D-π-A染料体系容易沿着π-共轭链发生分子内电子转移,使\其具有优良的二介非线性光学性质和光电转换性质;同时对它进行恰当的分子修饰能使其具有导电性和离子选择性,本文对D-π-A染料体系LB膜的发展现状及其应用领域进行了综述。重点介绍了在二阶非线性光学和光电转换等领域的应用研究。 相似文献
945.
常压下电化学催化羰化直接合成异氰酸酯 总被引:2,自引:0,他引:2
近 2 0多年来 ,异氰酸酯的非光气合成方法一直受到人们的关注 [1] .采用 CO与硝基化合物羰化直接合成相应的异氰酸酯在理论上完全可行 [2 ] ,但由于异氰酸酯本身在所采用的高温、高压反应条件下很不稳定 ,实际产率很低 ,CO在醇存在下与硝基化合物催化还原羰化 [3 ,4 ] ,或与有机胺在氧气存在下催化氧化羰化 [5,6] 生成相应的化学性质较稳定的氨基甲酸酯 ,再将氨基甲酸酯通过高温热裂解生成异氰酸酯[7,8] .该反应在高温、高压下进行 ,条件较苛刻 ,因此探索在较温和的条件下实现直接合成异氰酸酯的途径是目前该领域中很具有挑战性的研究课题… 相似文献
946.
Cyclopentadienyl cobalt complexes (η5‐C5H4R) CoLI2 [L = CO,R=‐COOCH2CH=CH2 (3); L=PPh3, R=‐COOCH2‐CH=CH2 (6); L=P(p‐C6H4O3)3, R = ‐COOC(CH3) = CH2 (7), ‐COOCH2C6H5 (8), ‐COOCH2CH = CH2 (9)] were prepared and characterized by elemental analyses, 1H NMR, ER and UV‐vis spectra. The reaction of complexes (η5‐C5H4R)CoLI2 [L= CO, R= ‐COOC(CH3) = CH2 (1), ‐COOCH2C6H5(2); L=PPh3, R=‐COOC (CH3) = CH2 (4), ‐COOCH2C6H5 (5)] with Na‐Hg resulted in the formation of their corresponding substituted cobaltocene (η5‐C5H4R)2 Co[R=‐COOC(CH3) = CH2 (10), ‐COOCH2C6H5 (11)]. The electrochemical properties of these complexes 1–11 were studied by cyclic voltammetry. It was found that as the ligand (L) of the cobalt (III) complexes changing from CO to PPh3 and P(p‐tolyl)3, their oxidation potentials increased gradually. The cyclic voltammetry of α,α′‐substituted cobaltocene showed reversible oxidation of one electron process. 相似文献
947.
Crystal and molecular structure of (2,6-dipropylphenylamide) dimethyl (tetra-methyl cyclopentadienyl) silane titanium dichloride (I) was fully characterized by X-ray diffraction. The crystal is obtained from a mixture of ether/hexane as orthorhombic, with a = 12.658 (3) (A), b = 16.62 (3)(A), c = 11.760 (2)(A), V = 2474.2 (9)(A) 3, Z = 4, space group Pnma, R = 0.0399. Componud I compose of the π-bounded ring with its dimethylsilyl-dipropyl phenyl amido group and the two terminal chloride atoms coordinated to central metal to form a so-called constrained geometry catalyst (CGC) structure. The result of molecular mechanics (MM) calculations on compound I shows that bond lengths and bond angles from the MM calculation are comparable to the data obtained from the X-ray diffraction study. The relation of the structure of CGCs and their catalytic activity by MM calculations is also discussed. 相似文献
948.
Chiral NAD(P)H models are important reduction reagents in asymmetric synthesis. (S,)l-Benzyl-3-(p-tolylsulfinyl)-1,4 1 is one of these models, which canreduce carbonyl and unsaturated compound under mild conditions with highenantioselectivity'. An impressive example is that methyl benzoylformate is reduced byl in the presence of Mg= or Zn' to methyl (R)-mandelate with up to 97% e.e. at roomtemperature'. Our investigation' has shown that the reduction of allylic bromide by Iwithout Mg:* o… 相似文献
949.
950.
SrxBi1-xFeO3-δ (SBF) series mixed conductors were synthesized using standard ceramic method. The properties of such materials were characterized
by XRD, O2-TPD techniques. Abnormal crystal phenomena were found and explained and correlated with the oxygen permeation results. By
analysis of the critical radius (rc), the degree of openness of the lattice (Fv) and the average metal-oxygen bonding energy of the perovskite lattice (ABE), it was proposed that the oxygen permeation
flux is determined mainly by the oxygen diffusion rate in bulk when 1-x⩽0.5, and by the concentration of oxygen vacancy when 1-x ⩾ 0.5. The stability of Sr0.5Bi0.5FeO3-δ was also investigated, and the high stability of it was attributed to the stable BO6 octahedra. 相似文献