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31.
T.E. Vittal Prasad N. Malleswara Reddy 《The Journal of chemical thermodynamics》2006,38(12):1696-1700
Bubble point temperatures at 95.5 kPa, over the entire composition range, are measured for the binary mixtures formed by m-cresol with: methanol, ethanol, 1-propanol, 2-propanol, and n-, iso-, sec-, and tert-butanols - using a Swietoslawski-type ebulliometer. The liquid phase composition - bubble point temperature measurements are well represented by the Wilson model. (Vapor + liquid) equilibria predicted from the model are presented. 相似文献
32.
33.
The use of capillary column gas chromatography and gas chromatography/mass spectrometry for the analysis of a series of standard solutions (0.1 to 10 μg/ml) of 2,4,6-trinitrotoluene (TNT) and eight other nitroaromatic components was evaluated. The techniques included gas chromatography with electron capture detection (GC/ECD), full scan and selected ion monitoring gas chromatography/mass spectrometry with electron impact ionization (EI/FS and EI/SIM), full scan and selected ion monitoring gas chromatography/mass spectrometry with positive ion chemical ionization using methane reagent gas (PICI/FS and PICI/SIM), and full scan and selected ion monitoring gas chromatography/mass spectrometry with negative ion chemical ionization using methane reagent gas (NICI/FS and NICI/SIM). The performance of the techniques was comapared by determining the linear response range, precision, and detection limits of the analyses. 相似文献
34.
Maria Cyfert Barbara Latko Maria Wronska 《Monatshefte für Chemie / Chemical Monthly》1980,111(3):619-626
The influence of NaClO4, NaCl and Na2SO4 on the oxidation of Fe(phen)
3
2+
by Ce(IV) was investigated by means of the stopped-flow method. At the concentrations range of NaClO4 and NaCl 0.1–1.0M the rate constant values decrease from 1.03·105 to 0.56·105M–1s–1 and from 1.08·105 to 0.81·105M–1s–1 respectively.In varying concentrations of Na2SO4 solutions (0.05–0.35M) the rate constant values decrease from 1.05·105M–1s–1 to 0.45·105M–1s–1.Taking into account the negative salt effect the mechanism of the reaction progress is proposed. 相似文献
35.
Static pressure usually increases the transition temperatures of polymers by decreasing their free volume. If the pressurizing medium is soluble in the polymer matrix, the opposing effect of increasing the free volume is possible. Those shifts of transition temperatures were monitored with a medium-pressure Differential Scanning Calorimetry (DSC) device. The influences of sorbed and surrounding gas molecules are demonstrated by changes occurring in the transition temperature regions. The results show the severe plasticizing effect of CO2 on poly(p-phenylene sulphide) (PPS). The glass transition temperature TG and the temperature of crystallization TC are influenced by sorbed gas molecules. They decrease due to sorbed CO2 molecules. Glass transition is lowered, but is difficult to interpret, as relaxation phenomena which diminish with increasing pressure occur during DSC runs. In crystallites no gas solution is usually possible, so that the melting point of PPS is mainly affected by influences other than plasticization. 相似文献
36.
Summary Dipole polarizability estimates at have been calculated for the 2p and 3p open-shell negative ions in their ground and valence excited states. To complete the sequence such estimates for F– and Cl– in their ground1
S state have also been made. Single configuration based linear response theory has been adopted presently with a view to study the effect of RPA-type correlations on the polarizabilities of such systems. For the 3p open-shell systems the innermost 1s core has been kept frozen. Most of the results are reported for the first time. Agreement with existing data, wherever available, is reasonable. The convergence of the polarizability estimates towards basis sets has been studied. 相似文献
37.
Hesham Ibrahim Saleh 《中国化学会会志》2002,49(3):341-348
The reactions between strontium and iron nitrates have been studied in an open atmosphere system using three different molar ratios, 1:1 (I), 1:2 (II) and 2:1 (III) at different temperatures as pointed out from the DTA data. The reaction mechanism was discussed based on the chemical composition characterized by means of thermal analysis, X‐ray diffraction patterns, infrared spectra and magnetic susceptibility. It was found that the reaction products depend on both temperature of reaction and the ratio between reactants. The reaction products were found to be composed of a variety of iron compounds that possess different valences: SrFeO2.86, SrFeO2.97, SrFe2O4, SrFe12O19, Sr2Fe2O5 and Sr7Fe10O22 in addition to some accessory reaction products namely α‐Fe2O3 and FeO(OH). 相似文献
38.
Dissociative and nondissociative electron attachment in the electron impact energy range 0–14 eV are reported for SOF2 SOF4, SO2F2, SF4, SO2, and SiF4 compounds which can be formed by electrical discharges in SF6. The electron energy dependences of the mass-identified negative ions were determined in a time-of-flight mass spectrometer. The ions studied include F– and SOF
2
–*
from SOF2; SOF
3
–
and F– from SOF4; SO2F
2
–*
, SO2F–, F
2
–
, and F– from SO2F2; SF
4
–*
and F– from SF4; O–, SO–, and S– from SO2; and SiF
3
–
and F– from SiF4. Thermochemical data have been determined from the threshold energies of some of the fragment negative ions. Lifetimes of the anions SOF
2
–*
, SO2F
2
–*
, and SF
4
–*
are also reported. 相似文献
39.
Positive and negative ions of Ar/SF6 and Ar/SF6/O2 plasmas (etching plasmas) and of Ar/O2 plasmas (cleaning plasmas) in Pyrex tubes have been investigated using a mass spectrometer-wall probe diagnostic technique. The measurement of negative ions proved to be a very sensitive method for the detection of wall material. In etching plasmas with small admixtures of SF6, oxygen was found as the only representative of wall material. At larger amounts of SF6, silicon could be detected. In cleaning plasmas with small admixtures of O2 applied to a previously etched Pyrex surface, fluorine was found, indicating the reversal of fluoridation by oxygenation. 相似文献
40.
The response of a single TE102 and double TE104 rectangular cavity to the insertion of samples contained in tubes with variable wall thickness and a quartz Dewar into the cavity has been analyzed. A direct, indirect, and concurrent (positive or negative) “lens effect” inside the double TE104 rectangular cavity is discussed. The experimental dependence of the EPR signal intensity on the wall thickness of the sample tube, δ, for the line-like samples with identical length of the sample material column, L=30 mm, recorded in the microwave cavity showed a directly proportional increase of the relative “lens effect” with the increase of the wall thickness of the tube in the interval, δ∈<0.1 mm, >0.5 mm. The insertion of the variable-temperature double-wall quartz Dewar (home-built, resonant frequency shift, ca. −300 MHz) into the single TE102 rectangular cavity showed the same relative “lens effect”, with ca. 1.5-time increase of the EPR signal intensity, for a point-like sample and the line-like samples with material columns of diameter of 1 and 1.3 mm, and wall thickness of the sample tubes, δ∈<0.1 mm, >0.5 mm. The increased effect of the Dewar arises because the active volume of the quartz Dewar tube walls is always much more larger than the active volume of the sample tube wall. In the case of the double TE104 rectangular cavity, the insertion of the quartz Dewar: (i) into the same cavity, in which the sample is present, caused a direct “lens effect”, with ca. 1.8-fold increase of the EPR signal intensity; however, (ii) into the complementary cavity, in which the sample is absent, caused an indirect “lens effect”, with ca. 0.6-fold decrease of the EPR signal intensity. With the Dewar and sample in one cavity and a large empty sample tube in the complementary cavity, a concurrent (positive or negative) “lens effect” can be observed. Thus, the possible increase/decrease of the EPR signal intensity depends on the volume ratio of the quartz Dewar tube walls and large sample tube wall inserted into the double TE104 rectangular cavity. Each of the above phenomena may be a significant source error in quantitative EPR spectrometry unless the samples to be compared in the quantitative EPR analysis are contained in sample tubes having the same wall thickness and each EPR spectra should be recorded inside an identical quartz Dewar. 相似文献