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101.
The calculations of the P-V isotherms, Hugoniots, dissociation and ionization degrees of fluid (liquid) hydrogen isotopes have been performed by using the self-consistent fluid variational theory under isothermal and shock compression. The isotope effect of fluid hydrogen was discussed. The present results are compared with the available experiments and calculations. 相似文献
102.
P. M. Carreira D. Nunes P. Valério M. F. Araújo 《Journal of Radioanalytical and Nuclear Chemistry》2009,281(1):153-156
The Nuclear and Technological Institute (Instituto Tecnológico e Nuclear—ITN) in cooperation with the International Atomic
Energy Agency (IAEA) has been conducting a nationwide survey of hydrogen (2H/1H) and oxygen (18O/16O) isotopic composition of monthly precipitation since 1988. This paper focuses on basic features of spatial and temporal
distribution of δ18O and δ2H in the precipitation over Continental Portugal derived from ITN database. Phenomenological relationships between stable
isotopes composition of precipitation and various climate-related parameters (local air temperature, distance to the Atlantic
coast, altitude, amount of precipitation) are established and discussed. 相似文献
103.
Helmar Wiltsche Karl Prattes Michael Zischka Günter Knapp 《Spectrochimica Acta Part B: Atomic Spectroscopy》2009
In the production of 10B enriched steels, the production–recycling process needs to be closely monitored for inadvertent mix-up of materials with different B isotope levels. A quick and simple method for the estimation of boron isotope ratios in high alloyed steels using high resolution continuum source flame AAS (HR-CS-FAAS) was developed. On the 208.9 nm B line the wavelength of the peak absorption of 10B and 11B differs by 2.5 pm. The wavelength of the peak absorption of boron was determined by fitting a Gauss function through spectra simultaneously recorded by HR-CS-FAAS. It was shown that a linear correlation between the wavelength of the peak absorption and the isotope ratio exists and that this correlation is independent of the total boron concentration. Internal spectroscopic standards were used to compensate for monochromator drift and monochromator resolution changes. Accuracy and precision of the analyzed samples were thereby increased by a factor of up to 1.3. Three steel reference materials and one boric acid CRM, each certified for the boron isotope ratio were used to validate the procedure. 相似文献
104.
The enthalpies of dilution of
-alanine and
-serine in various aqueous urea solutions have been determined by flow microcalorimetry at 298.15 K. The homogeneous enthalpic interaction coefficients over the whole range of aqueous urea solutions have been calculated according to the excess enthalpy concept. The results were interpreted from the point of view of solute–solute interactions moderated by solvent effects. 相似文献
105.
106.
L Hai-Jiang YE Yun-Xiu YAN Xin-Hu CHENG He-Ping JIAO Zheng HE Ju LIU Ren-Chen 《中国物理C(英文版)》2008,32(8)
In the GDH sum rule measurement in JLab Hall-A,to obtain the cross section of electron scattering on polarized 3He and its asymmetry in different helicity states,the dilution effect from unpolarized nitrogen mixed in the polarized 3He target were calculated at different kinematic settings. 相似文献
107.
掺氢天然气在稀释气体作用下的熄灭特性研究对实际燃烧设备的设计和优化具有重要的指导意义。本文利用对冲火焰法测量了掺氢天然气层流火焰在N2和CO2作用下的熄灭拉伸率,并采用数值模拟耦合详细化学反应机理对N2,CO2和He的稀释剂效应展开研究。结果表明,Li、GRI Mech 3.0和FFCM-1机理均能定性反映燃料熄灭拉伸率随当量比的变化规律,且FFCM-1机理综合预测精度最高。实验和模拟发现,不同稀释剂气体对掺氢天然气熄灭拉伸率降低幅度满足:He22。进一步研究发现,CO2由于热容大,在反应体系中会降低火焰温度,同时增强了链终止反应强度,通过热效应和化学效应两方面对火焰熄灭特性起作用。He则能显著改变燃料混合物的平均摩尔质量,从而改变体系中重要反应物和自由基的扩散特性,从扩散效应方面影响火焰的熄灭特性。 相似文献
108.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(14):4091-4094
S ‐Adenosylmethionine‐dependent methyltransferases (MTs) play a decisive role in the biosynthesis of natural products and in epigenetic processes. MTs catalyze the methylation of heteroatoms and even of carbon atoms, which, in many cases, is a challenging reaction in conventional synthesis. However, C‐MTs are often highly substrate‐specific. Herein, we show that SgvM from Streptomyces griseoviridis features an extended substrate scope with respect to the nucleophile as well as the electrophile. Aside from its physiological substrate 4‐methyl‐2‐oxovalerate, SgvM catalyzes the (di)methylation of pyruvate, 2‐oxobutyrate, 2‐oxovalerate, and phenylpyruvate at the β‐carbon atom. Chiral‐phase HPLC analysis revealed that the methylation of 2‐oxovalerate occurs with R selectivity while the ethylation of 2‐oxobutyrate with S ‐adenosylethionine results in the S enantiomer of 3‐methyl‐2‐oxovalerate. Thus SgvM could be a valuable tool for asymmetric biocatalytic C‐alkylation reactions. 相似文献
109.
110.