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221.
Cristelle Portet Dmitry Kazachkin Sebastian Osswald Yury Gogotsi Eric Borguet 《Thermochimica Acta》2010,497(1-2):137-142
Carbide-derived carbons produced by chlorination of titanium carbide at 600, 800, or 1100 °C were subjected to a post-treatment at 600 °C in Ar, H2, or NH3 atmosphere. Experimental results suggest that the chlorination temperature influences the ordering of carbon in a manner that impacts specific surface area and porosity. Higher chlorination temperatures lead to higher total pore volume and increased ordering, but lower microporosity. The effect of post-treatments on surface chemistry is pronounced only for samples chlorinated at 600 °C; post-treatments in Ar are shown to be less effective for chlorine removal than those performed in H2 or NH3. Post-treatments in Ar result in a lower total pore volume compared to the ones in H2 or NH3 for the same chlorination temperature. Samples chlorinated at higher temperatures contained less oxygen functionalities than samples chlorinated at 600 °C, and showed correspondingly less desorption of H2O, possibly due to diminished uptake of ambient water. 相似文献
222.
C. Peter Sebastian 《Journal of solid state chemistry》2010,183(4):878-882
The compound CeAu0.28Ge1.72 crystallizes in the ThSi2 structure type in the tetragonal space group I41/amd with lattice parameters a=b=4.2415(6) Å c=14.640(3) Å. CeAu0.28Ge1.72 is a polar intermetallic compound having a three-dimensional Ge/Au polyanion sub-network filled with Ce atoms. The magnetic susceptibility data show Curie-Weiss law behavior above 50 K. The compound orders ferromagnetically at ∼8 K with estimated magnetic moment of 2.48 μB/Ce. The ferromagnetic ordering is confirmed by the heat capacity data which show a rise at ∼8 K. The electronic specific heat coefficient (γ) value obtained from the paramagnetic temperature range 15-25 K is∼124(5) mJ/ mol K2. The entropy change due to the ferromagnetic transition is ∼4.2 J/mol K which is appreciably reduced compared to the value of R ln(2) expected for a crystal-field-split doublet ground state and/or Kondo exchange interactions. 相似文献
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226.
Sebastian Schneckener Linus Görlitz Heidrun Ellinger-Ziegelbauer Hans-Jürgen Ahr Andreas Schuppert 《Computational Biology and Chemistry》2010,34(3):193-202
Exposing eukaryotic cells to a toxic compound and subsequent gene expression profiling may allow the prediction of selected toxic effects based on changes in gene expression. This objective is complicated by the observation that compounds with different modes of toxicity cause similar changes in gene expression and that a global stress response affects many genes. We developed an elastic network model of global stress response with nodes representing genes which are connected by edges of graded coexpression. The expression of only few genes have to be known to model the global stress response of all but a few atypical responder genes. Those required genes and the atypical response genes are shown to be good biomarker for tox predictions. In total, 138 experiments and 13 different compounds were used to train models for different toxicity classes. The deduced biomarkers were shown to be biologically plausible. A neural network was trained to predict the toxic effects of compounds from profiling experiments. On a validation data set of 189 experiments with 16 different compounds the accuracy of the predictions was assessed: 14 out of 16 compounds have been classified correctly. Derivation of model based biomarkers through the elastic network approach can naturally be extended to other areas beyond toxicology since subtle signals against a broad response background are common in biological studies. 相似文献
227.
Ariane Wohlfarth Wolfgang Weinmann Sebastian Dresen 《Analytical and bioanalytical chemistry》2010,396(7):2403-2414
Since the late 1990s and early 2000s, derivatives of well-known designer drugs as well as new psychoactive compounds have
been sold on the illicit drug market and have led to intoxications and fatalities. The LC-MS/MS screening method presented
covers 31 new designer drugs as well as cathinone, methcathinone, phencyclidine, and ketamine which were included to complete
the screening spectrum. All but the last two are modified molecular structures of amphetamine, tryptamine, or piperazine.
Among the amphetamine derivatives are cathinone, methcathinone, 3,4-DMA, 2,5-DMA, DOB, DOET, DOM, ethylamphetamine, MDDMA,
4-MTA, PMA, PMMA, 3,4,5-TMA, TMA-6 and members of the 2C group: 2C-B, 2C-D, 2C-H, 2C-I, 2C-P, 2C-T-2, 2C-T-4, and 2C-T-7.
AMT, DPT, DiPT, MiPT, DMT, and 5MeO-DMT are contained in the tryptamine group, BZP, MDBP, TFMPP, mCPP, and MeOPP in the piperazine
group. Using an Applied Biosystems LC-MS/MS API 365 TurboIonSpray it is possible to identify all 35 substances. After addition
of internal standards and mixed-mode solid-phase extraction the analytes are separated using a Synergi Polar RP column and
gradient elution with 1 mM ammonium formate and methanol/0.1% formic acid as mobile phases A and B. Data acquisition is performed
in MRM mode with positive electro spray ionization. The assay is selective for all tested substances. Limits of detection
were determined by analyzing S/N-ratios and are between 1.0 and 5.0 ng/mL. Matrix effects lie between 65% and 118%, extraction efficiencies range from 72%
to 90%. 相似文献
228.
Rosemarie Philipp Olaf Hanebeck Sebastian Hein Wolfram Bremser Tin Win Irene Nehls 《Accreditation and quality assurance》2010,15(3):141-146
The Federal Institute for Materials Research and Testing (BAM), Germany, has issued a series of large volume ethanol in water
certified reference materials (CRMs), primarily developed for the calibration of evidential breath alcohol analyzers in Germany.
The certified parameter is the ethanol mass concentration at 20 °C. When used in a wet bath simulator, the solutions deliver
gas samples that meet the requirements set by the Organization of Legal Metrology for calibration of breathalyzers. The materials
were prepared gravimetrically by spiking of ethanol into water in single 5 L units. A complete uncertainty budget for the
preparation process has been established. The purity of the commercial ethanol stock solution was identified to be the main
source of uncertainty. For stability and homogeneity measurements and for the verification of the gravimetric mass concentration
of the CRMs, a robust high-precision gas chromatography, with flame-ionization detection method for ethanol determination
in aqueous samples was developed and validated. The good performance of this method has been demonstrated in several international
comparisons organized by the Consultative Committee for Amount of Substance—Metrology in Chemistry at the International Bureau
of Weights and Measures. 相似文献
229.
Shengyang Guan David C. Mayer Christian Jandl Sebastian J. Weishupl Angela Casini Alexander Pthig 《Molecules (Basel, Switzerland)》2021,26(15)
A new solvatomorph of [Au3(1-Methylimidazolate)3] (Au3(MeIm)3)—the simplest congener of imidazolate-based Au(I) cyclic trinuclear complexes (CTCs)—has been identified and structurally characterized. Single-crystal X-ray diffraction revealed a dichloromethane solvate exhibiting remarkably short intermolecular Au⋯Au distances (3.2190(7) Å). This goes along with a dimer formation in the solid state, which is not observed in a previously reported solvent-free crystal structure. Hirshfeld analysis, in combination with density functional theory (DFT) calculations, indicates that the dimerization is generally driven by attractive aurophilic interactions, which are commonly associated with the luminescence properties of CTCs. Since Au3(MeIm)3 has previously been reported to be emissive in the solid-state, we conducted a thorough photophysical study combined with phase analysis by means of powder X-ray diffraction (PXRD), to correctly attribute the photophysically active phase of the bulk material. Interestingly, all investigated powder samples accessed via different preparation methods can be assigned to the pristine solvent-free crystal structure, showing no aurophilic interactions. Finally, the observed strong thermochromism of the solid-state material was investigated by means of variable-temperature PXRD, ruling out a significant phase transition being responsible for the drastic change of the emission properties (hypsochromic shift from 710 nm to 510 nm) when lowering the temperature down to 77 K. 相似文献
230.
Let G be a connected reductive algebraic group defined over an algebraically closed field of positive characteristic. We study a generalization of the notion of G-complete reducibility in the context of Steinberg endomorphisms of G. Our main theorem extends a special case of a rationality result in this setting. 相似文献