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Christopher H. Conaway Burt Thomas Nabil Saad James J. Thordsen Yousif K. Kharaka 《Isotopes in environmental and health studies》2013,49(2):344-358
This work examines the performance and limitations of a wet chemical oxidation carbon analyser interfaced with a cavity ring-down spectrometer (WCO-CRDS) in a continuous flow (CF) configuration for measuring δ13C of dissolved organic carbon (δ13C-DOC) in natural water samples. Low-chloride matrix (<5?g Cl/L) DOC solutions were analysed with as little as 2.5?mg C/L in a 9?mL aliquot with a precision of 0.5?‰. In high-chloride matrix (10–100?g Cl/L) DOC solutions, bias towards lighter δ13C-DOC was observed because of incomplete oxidation despite using high-concentration oxidant, extended reaction time, or post-wet chemical oxidation gas-phase combustion. However, through a combination of dilution, chloride removal, and increasing the oxidant:sample ratio, high-salinity samples with sufficient DOC (>22.5?µg C/aliquot) may be analysed. The WCO-CRDS approach requires more total carbon (µg C/aliquot) than conventional CF-isotope ratio mass spectrometer, but is nonetheless applicable to a wide range of DOC concentration and water types, including brackish water, produced water, and basinal brines. 相似文献
134.
Olivia J. Maselli Diedrich Fritzsche Lawrence Layman Joseph R. McConnell Hanno Meyer 《Isotopes in environmental and health studies》2013,49(3):387-398
We present a detailed comparison between subsequent versions of commercially available wavelength-scanned cavity ring-down water isotope analysers (L2120-i and L2130-i, Picarro Inc.). The analysers are used in parallel in a continuous mode by adaption of a low-volume flash evaporation module. Application of the analysers to ice-core analysis is assessed by comparison between continuous water isotope measurements of a glacial ice-core from Severnaya Zemlya with discrete isotope-ratio mass spectrometry measurements performed on parallel samples from the same ice-core. The great advances between instrument versions, particularly in the measurement of δ2H, allow the continuous technique to achieve the same high level of accuracy and precision obtained using traditional isotope spectrometry techniques in a fraction of the experiment time. However, when applied to continuous ice-core measurements, increased integration times result in a compromise of the achievable depth resolution of the ice-core records. 相似文献
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Vasileios Gkinis Trevor J. Popp Sigfus J. Johnsen Thomas Blunier 《Isotopes in environmental and health studies》2013,49(4):463-475
A new technique for high-resolution simultaneous isotopic analysis of δ18O and δD in liquid water is presented. A continuous stream flash evaporator has been designed that is able to vapourise a stream of liquid water in a continuous mode and deliver a stable and finely controlled water vapour sample to a commercially available infrared cavity ring-down spectrometer. Injection of sub-microlitre amounts of the liquid water is achieved by pumping liquid water sample through a fused silica capillary and instantaneously vapourising it with 100% efficiency in a home-made oven at a temperature of 170?°C. The system's simplicity, low power consumption and low dead volume together with the possibility for automated unattended operation provides a solution for the calibration of laser instruments performing isotopic analysis of water vapour. Our work is mainly driven by the possibility to perform high-resolution online water isotopic analysis on continuous-flow analysis (CFA) systems typically used to analyse the chemical composition of ice cores drilled in polar regions. In the following, we describe the system's precision and stability and sensitivity to varying levels of sample size and we assess the observed memory effects. A test run with standard waters of different isotopic compositions is presented, demonstrating the ability to calibrate the spectrometer's measurements on a VSMOW scale with a relatively simple and fast procedure. 相似文献
137.
H. Melcher 《Isotopes in environmental and health studies》2013,49(7):299-300
In der Kernstrahlungs-Meßtechnik erweist es sich in vielen Fällen als zweckmäßig und vorteilhaft, den Bereich der besehränkten Proportionalität eines Fenster-Auslösezählrohres auszunutzen. Nimmt man die Charakteristik eines Fenster-Auslösezählrohres für einen reinen α-Strahler auf, so ergeben sich die Kurven α der Abbildung. Verwendet man einen reinen β-Strahler, so ergeben sich die Kurven β. 相似文献
138.
D. Schmidt 《Isotopes in environmental and health studies》2013,49(10):416-418
Es werden einfach herzustellende Geräte beschrieben, mit deren Hilfe mehrfach wiederholte Flüssig-Flüssig-Extraktionen schnell, unter geringem Arbeitsaufwand und mit verminderten Substanzverlusten durchgeführt werden können. Die Arbeitsweise erwies sich als besonders geeignet für mittelschnelle radiochemische Trennungsgänge in der Aktivierungsanalyse, z. B. bei der Bestimmung von Zinn über das 40-min-Isotp 123Sn. 相似文献
139.
Songjun Guo Sheng Wen Guoying Sheng Jiamo Fu 《Isotopes in environmental and health studies》2013,49(4):473-482
δ13C values of gaseous acetaldehyde were measured by gas chromatograph–combustion–isotope ratio mass spectrometer (GC–C–IRMS) via sodium bisulfite (NaHSO3) adsorption and cysteamine derivatisation. Gaseous acetaldehyde was collected via NaHSO3-coated Sep-Pak® silica gel cartridge, then derivatised with cysteamine, and then the δ13C value of the acetaldehyde–cysteamine derivative was measured by GC–C–IRMS. Using two acetaldehydes with different δ13C values, derivatisation experiments were carried out to cover concentrations between 0.009×10?3 and 1.96×10?3 mg·l?1) of atmospheric acetaldehyde, and then δ13C fractionation was evaluated in the derivatisation of acetaldehyde based on stoichiometric mass balance after measuring the δ13C values of acetaldehyde, cysteamine and the acetaldehyde–cysteamine derivative. δ13C measurements in the derivertisation process showed good reproducibility (<0.5 ‰) for gaseous acetaldehyde. The differences between predicted and measured δ13C values were 0.04–0.31 ‰ for acetaldehyde–cysteamine derivative, indicating that the derivatisation introduces no isotope fractionation for gaseous acetaldehyde, and obtained δ13C values of acetaldehyde in ambient air at the two sites were distinct (?34.00 ‰ at an urban site versus?31.00 ‰ at a forest site), implying potential application of the method to study atmospheric acetaldehyde. 相似文献
140.