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121.
The crystal structure of Sr4Mn2NiO9 has been refined on single crystal. This phase belongs to the series A1+x(A′xB1–x)O3 (x=1/3) related to the 2H-hexagonal perovskite. The structure contains transition metals in chains of oxide polyhedra (trigonal prisms and octahedra); neighboring chains are separated from each other by the Sr atoms. The sequence of the face sharing polyhedra along the chains is two octahedra + one trigonal prism. Mn occupies the octahedra and Ni is disordered in the trigonal prism with ≈80% in the pseudo square faces of the prism and ≈20% at the centre. This result has been confirmed by XANES experiments at Mn K and Ni K edges, respectively. Sr4Mn2NiO9 is antiferromagnetic with a Néel temperature at T=3 K. The Curie constant measured at high temperature is in good agreement with ≈80% of the Ni2+ ions in the spin state configuration S=0. 相似文献
122.
Samples of synthetic hydroxyapatite, Ca(10)(PO(4))(6)(OH)(2), obtained by wet method and calcined at 1173 K in air were used in an adsorption study of some essential amino acids, mainly histidine, methionine, and tryptophan. Adsorption isotherms were obtained using aqueous solutions of concentration range 2.7x10(-2)-1.3x10(-3) M at 303, 318, and 343 K, under near neutral conditions. The mode of adsorption was studied using IR spectroscopy. The results are discussed in terms of the dependence of the adsorption process both on the functional groups on the hydroxyapatite and on the solution chemistry of the aqueous amino acids solutions. Copyright 2001 Academic Press. 相似文献
123.
The reaction of 3‐benzoylcyanomethylidine‐1(H)‐indole‐2‐one ( 1 ) with a variety of active methylene compounds, thioglycolic acid, glycine, hydrazine hydrate and phenyl hydrazine led to the formation of compounds 4a‐d‐10 . 3‐Thiosemicarbazide‐1(H)‐indole‐2‐one 2 on reaction with α‐halocarbonyl compounds gave compounds 11a‐c, 12a‐c . The latter compounds on heating with phosphoryl chloride, cyclization takes place via losing water to give the angular tetracyclic compounds 13a,b and 14a‐c . Cyanoacetic hydrazone derivative 3 readily cyclized upon heating in triethyl orthoformate to give the tricyclic system, oxopyridazino indole 15 . On the other hand, the reaction of 3 with benzylidine malononitrile and benzylidene ethylcyanoactate gave the pyranyl hydrazone derivatives 16a,b . 相似文献
124.
Polymer‐solvent compounds can be formed from homogeneous solutions obtained at high temperature but also by solvent diffusion at the solid interface of a bulk polymer at room temperature. This phenomenon we call “physical” corrosion as it modifies the surface structure without chemical change. Here we report preliminary experiments indicating that the thermodynamics seems to be little dependent upon the path used while the morphology is. 相似文献
125.
Monosaccharide osazones are utilized in the spectrophotometric determination of their parent compounds though charge-transfer complexation with two-electron acceptor reagents. The molar combining ratio and the optimum complexation conditions have been studied. The method has been used to analyse for glucose and fructose and in determining blood glucose. 相似文献
126.
Summary A new index of performance of the chromatographic separation between two adjacent peaks, the discrimination factor, d0, is defined. It is normalized between 0 and 1 and is directly and easily determined from the chromatogram. It does not depend
on any assumption regarding peak shape, except that the peak profiles of individual sample components have a single mode.
Its value depends on the relative heights of the two peaks as well as on their separation.
The separation power of a chromatographic system is classically measured by its peak capacity, defined on the basis of constant
resolution between adjacent peaks. A previously developed statistical theory of the composition of mixtures makes it possible
to extend the concept of peak capacity by taking into account the peak height distribution in typical average chromatograms.
A new parameter, the effective peak capacity, is defined for this purpose on the basis of a constant discrimination factor
between adjacent peaks. It allows to take into account the distribution of peak heights in statistical theories of the evaluation
of complex chromatograms and in the measurement of the limit of determination in quantitative analysis.
The characteristics of the two new parameters, the discrimination factor and effective peak capacity, are discussed and compared
with those of their classical homologs, resolution and peak capacity, in the case of gaussian component peaks of equal widths. 相似文献
127.
128.
J. A. Stratis M. Lalia-Kantouri El. Charalambous A. Charalambous N. Kantiranis 《Journal of Thermal Analysis and Calorimetry》2011,104(2):431-437
This study is focused on simultaneous thermoanalytical investigations by TG/DTG-DTA technique applied for characterization
of samples collected from archaeological site of Nicosia, Cyprus, dating to seventeenth century and gave new information on
the firing technology. The ceramic samples derived from Ottomanic tobacco pipes were characterized by the related techniques
such as X-ray powder diffraction for the mineralogical composition, and inductively coupled plasma-atomic emission spectrometry
and micro-X-ray fluorescence spectroscopic analysis for the chemical content. It was found that they consisted mainly of quartz,
calcite, feldspars, and micas. For the majority of the investigated ceramic samples, the thermal behavior investigation collaborates
with their mineralogical findings, and resulted to the firing temperature at ~700 °C, due to the existence of calcite. Only
in two samples with very high content in quartz, absence of calcite, low amounts of adsorbed water and of total mass loss,
and absence of micas, the firing process resulted up to 1000 °C. 相似文献
129.
Two ordinary green light-emitting diodes used as light emitter and detector coupled with simple voltmeter form a complete,
cost-effective prototype of a photometric hemoglobinometer. The device has been optimized for cuvette assays of total hemoglobin
(Hb) in diluted blood using three different chemical methods recommended for the needs of clinical analysis (namely Drabkin,
lauryl sulfate, and dithionite methods). The utility of developed device for real analytics has been validated by the assays
of total Hb content in human blood. The results of analysis are fully compatible with those obtained using clinically recommended
method and clinical analyzer. 相似文献
130.
Thakurta S Chakraborty J Rosair G Tercero J El Fallah MS Garribba E Mitra S 《Inorganic chemistry》2008,47(14):6227-6235
Two new Cu(II) linear trinuclear Schiff base complexes, [Cu3(L)2(CH3COO)2] (1) and [Cu3(L)2(CF3COO)2] (2), have been prepared using a symmetrical Schiff base ligand H2L [where H2L = N,N'-bis(2-hydroxyacetophenone)propylenediimine]. Both of the complexes have been characterized by elemental analyses, Fourier transform IR, UV/vis, and electron paramagnetic resonance spectroscopy. Single-crystal X-ray structures show that the adjacent Cu(II) ions are linked by double phenoxo bridges and a mu(2)-eta(1):eta(1) carboxylato bridge. In each complex, the central copper atom is located in an inversion center with distorted octahedral coordination geometry, while the terminal copper atoms have square-pyramidal geometry. Cryomagnetic susceptibility measurements over a wide range of temperature exhibit a distinct antiferromagnetic interaction of J = -36.5 and -72.3 cm(-1) for 1 and 2, respectively. Density functional theory calculations (B3LYP functional) and continuous-shape measurement (CShM) studies have been performed on the trinuclear unit to provide a qualitative theoretical interpretation of the antiferromagnetic behavior shown by the complexes. 相似文献