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791.
Barbara Marciniec M. Stawny Magdalena Hofman M. Naskrent 《Journal of Thermal Analysis and Calorimetry》2008,93(3):733-737
The study has been undertaken to check the effect of ionising radiation on the physical and chemical properties of florfenicol,
an antibiotic of a wide range of antibacterial activity. The solid-state samples were subjected to an electron beam generated
by accelerator corresponding to the doses of 25, 100 and 400 kGy, and the effect of the exposure was analysed by the methods
not requiring changes in the state (with no preliminary treatment), such as SEM, DSC, FTIR, XRD, EPR and HPLC.
Florfenicol irradiated with a dose of 25 kGy has not changed the form or colour, however, a small increase in intensity of
some absorption bands in the FTIR spectrum and of some peaks in the XRD pattern, a decrease in the melting point by 0.6°C,
the appearance of free radicals and a loss in the FF content within the error of the method (0.91%) have been observed. After
irradiation with greater doses (100 and 400 kGy) the changes have intensified, yellow discolouration appeared and the loss
of FF content has increased to 6.39%. As follows from the results, the compound studied in solid-state undergoes radiolysis
after e-beam irradiation in the doses ≥25 kGy, but lower doses (15–20 kGy) can be applied for its decontamination or sterilization
with no adverse effect on its physico-chemical properties. 相似文献
792.
Ignat'eva DV Goryunkov AA Tamm NB Ioffe IN Avdoshenko SM Sidorov LN Dimitrov A Kemnitz E Troyanov SI 《Chemical communications (Cambridge, England)》2006,(16):1778-1780
Two isomers of C70(CF3)12 have been isolated from a mixture obtained by trifluoromethylation of C70 with CF3I; their molecular structures determined by X-ray crystallography are in good agreement with the results of theoretical DFT calculations for the most stable C70(CF3)12 isomers. 相似文献
793.
794.
Background
Rosiglitazone (ROZ) and glimepiride (GLM) are antidiabetic agents used in the treatment of type 2 diabetes mellitus. A survey of the literature reveals that only one spectrophotometric method has been reported for the simultaneous determination of ROS and GLM in pharmaceutical preparations. However the reported method suffers from the low sensitivity, for this reason, our target was to develop a simple sensitive HPLC method for the simultaneous determination of ROZ and GLM in their combined dosage forms and plasma. 相似文献795.
Ya-Ting Hsieh Nai-Tzu Kuo Eamor M. Woo 《Journal of Thermal Analysis and Calorimetry》2012,107(2):745-756
Abstract
Thermal behavior, miscibility, and crystalline morphology in blends of low-molecular-weight poly(l-lactic acid) (LMw-PLLA) or high-molecular-weight PLLA (HMw-PLLA) with various polyesters such as poly(butylene adipate) (PBA), poly(ethylene adipate) (PEA), poly(trimethylene adipate) (PTA), or poly(ethylene succinate) (PESu), respectively, were explored using differential scanning calorimeter (DSC), and polarized-light optical microscopy (POM). Phase behavior in blends of PLLA with other polyesters has been intriguing and not straight forward. Using a low- and high molecular weight PLLA, this study aimed at mainly using thermal analyses for probing the phase behavior, phase diagrams, and temperature dependence of blends systems composed of PLLA of two different molecular weights (low and high) with a series of aliphatic polyesters of different structures varying in the (CH2/CO) ratio in main chains. The blends of LMw-PLLA/PEA and LMw-PLLA/PTA show miscibility in melt and amorphous glassy states. Meanwhile, the LMw-PLLA/PESu blend is immiscible with an asymmetry-shaped upper critical solution temperature (UCST) at 220–240 °C depending on the blend composition. In contrast to miscibility in LMw-PLLA/PTA and LMw-PLLA/PEA blends, HMw-PLLA with polyesters are mostly immiscible; and HMw-PLLA/PTA blend is the only one showing an asymmetry-shaped UCST phase diagram with clarity points at 195–235 °C (depending on composition). Reversibility of UCST behavior, with no chemical transreactions, in these blends was proven by solvent recasting, gel permeation chromatography, and Fourier transform infrared spectroscopy (FT-IR). Crystalline morphology behavior of the LMw-PLLA/PEA and LMw-PLLA/PTA blends furnishes addition evidence for miscibility in the amorphous phase between LMw-PLLA and PTA or PEA. 相似文献796.
Igor E. Paukov Yulia A. Kovalevskaya Alexei E. Arzamastcev Natalia A. Pankrushina Elena V. Boldyreva 《Journal of Thermal Analysis and Calorimetry》2012,108(1):243-247
Heat capacity of methacetin (N-(4-methoxyphenyl)-acetamide) has been measured in the temperature range 5.8–300 K. No anomalies in the C
p(T) dependence were observed. Thermodynamic functions were calculated. At 298.15 K, the values of entropy and enthalpy are equal
to 243.1 J K−1 mol−1 and 36360 J mol−1, respectively. The heat capacity of methacetin in the temperature range 6–10 K is well fitted by Debye equation C
p = AT
3. The thermodynamic data obtained for methacetin are compared with those for the monoclinic and orthorhombic polymorphs of
paracetamol. 相似文献
797.
Mahesh Datt Bhatt Akihisa Baba Takeaki Sakurai Katsuhiro Akimoto 《Journal of Solid State Electrochemistry》2012,16(3):1141-1149
We have performed ultraviolet photoelectron spectroscopy measurements and density functional theory calculations to study
the electronic structure at the interface between organic semiconductor (3-(4-biphenylyl)-4-phenyl-5-(4-tert-butyl phenyl)-1,2,4-triazole
(TAZ)) and metals (Ca, Mg, Ag, and Au). The basic mechanism of interface states at organic–metal interfaces can be understood
by controlling the injection of charge carriers at these interfaces. The position of highest occupied molecular orbital relative
to the Fermi level and the magnitude of the interface dipole are measured for each organic–metal interface. For TAZ on Ca,
Mg, and Ag, interface states are observed near the Fermi level. However, no interface state is observed for TAZ on Au. It
is analyzed qualitatively that the interface state is formed due to interaction of TAZ lowest unoccupied molecular orbital
composed of C2p and metal s levels. It is suggested that the interface state plays an important role in charge transport at
the interface. The mechanism of formation of interface states and electrical properties are discussed. 相似文献
798.
SmAlO3 nanopowder synthesized by a citrate precursor method using citric acid as a chelating agent and ethylene glycol as an esterifying
agent was reported in this paper. The phase purity of the as-prepared powder was examined using thermogravimetry (TG) analysis
and differential scanning calorimetry (DSC) analysis, Fourier transform infrared spectroscopy (FTIR). The X-ray diffraction
(XRD) studies showed that pure SmAlO3 phase with orthorhombic perovskite structure could be synthesized at 800 °C for 2 h without any detectable intermediate phase.
The average particle size calculated from transmission electron microscopy (TEM) investigation for the powder synthesized
at 900 °C was as low as 45 nm. The nanopowder was sintered to a density of 97% of the theoretical density at 1,550 °C for
2 h and the bulk ceramics exhibited excellent microwave dielectric properties as follows: a dielectric constant of 20.54,
a quality factor of 75,380 GHz and a temperature coefficient of resonate frequency of −69.2 ppm/K. 相似文献
799.
Ethanol production in a bioreactor with integrated membrane distillation (MD) module has been investigated. A hydrophobic
capillary polypropylene membrane (Accurel PP V8/2 HF), with an external/internal diameter ratio, d
out/d
in = 8.6 mm/5.5 mm and pore size 0.2 μm, was used in these studies. The products (mainly ethanol and acetic acid) formed during
the fermentation of sugar with Saccharomyces cerevisiae inhibited the process. These products were selectively removed from the fermentation broth by the MD process, which increased
the efficiency of the conversion of sugar to alcohol from 0.45 g to 0.5 g EtOH per g of fermented sucrose. The bioreactor
efficiency also increased by almost 30 %. Separation of alcohol by the MD generates a higher yield of ethanol in the permeate
than in the broth. The enrichment coefficient amounted to 4-8, and depended on the ethanol concentration in the broth. The
separated solutions did not wet the membrane in use for 2500 h of the MD experiments and the retention of inorganic solutes
was close to 100 %. 相似文献
800.
Paul G. Mezey 《Journal of mathematical chemistry》2012,50(4):926-933
For a specific functional group, considered as a molecular fragment, the rest of the molecule produces a range of interactions
which influence various properties of the functional group. Considering a family of molecules with the “same” functional group,
the range of variations in properties determines the range of chemical reactivity of the functional group, and a similar conclusion
is valid for more general molecular fragments. By the application of conventional as well as more advanced indices of fragment
properties, including local electron density shape characterization, various shape variation indices can be introduced for
fragments, and their relations to the holographic properties of electron densities can be examined. 相似文献