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991.
A. A. Benedetti-Pichler und Frank Schneider 《Fresenius' Journal of Analytical Chemistry》1931,86(1-4):69-80
Zusammenfassung Es wird ein einfaches Verfahren beschrieben, um kleine Mengen flüchtiger Stoffe aus grossen Mengen eines höher siedenden Lösungsmittels zu isolieren. Experimentell wurden nur einzelne Beispiele (wässrige Lösungen) untersucht, die im Hinblick auf die toxikologische Analyse Interesse bieten. Alkohol aus 60 ccm 0,01%iger Lösung, Methanol aus 30ccm 0,1%iger Lösung, Aceton aus 30 ccm 0,01%iger Lösung konnten in einer Operation in hochkonzentriertem Zustande erhalten werden. Chloroform und Äther konnten aus 30, bezw. 60 ccm 0,01%iger Lösungen rein isoliert werden. Der zur Anwendung kommende Rektifizierkolben ist eine Kochflasche mit langem engen Hals, der im Oberteil doppelt knieförmig gebogen ist, um das Sammeln des aufsteigenden ersten Kondensatringes zu ermöglichen, der wesentlich aus dem niedriger siedenden Bestandteil besteht. 相似文献
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993.
Harold B. Hopfenberg Nathaniel S. Schneider F. Votta 《Journal of Macromolecular Science: Physics》2013,52(4):751-766
Steady-state permeation rates and equilibrium sorption measurements were made as a function of temperature for a series of alcohols in a polybutylene adipate polyurethan. The alcohol series included methanol; ethanol; n-propanol; n-, iso-, sec-, and t-butanol; n-pentanol, n-hexanol, and n-heptanol (all at unit activity). Calculated integral diffusivities of the various penetrants correlated well with effective penetrant size. The solubility coefficients for the various alcohols increased as the difference between the solubility parameters of the polymer and penetrant decreased for the normal alcohol series. The solubility coefficients for the branched alcohol isomers were characterized by values lower than those predicted by the correlation for the normal alcohols; possibly steric hindrance limits sorption on specific polymer sites. A detailed analysis of the system ethanol/poly(butylene adipate-polyurethan) revealed a sigmoidal increase of the diffusion coefficient with increasing penetrant concentration, suggesting a competition between penetrant clustering and polymer plasticization. The diffusion process appears to be time dependent as well as concentration dependent. Anomalies in the diffusion behavior that can reasonably be related to polymer segmental relaxation are present to a much larger degree as temperature is increased. Ethanol sorption was further complicated by positive deviation from Henry's law at activities in excess of 0.2. 相似文献
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The effects of some instrumental factors on infrared spectroscopy analysis were investigated in the case of diffuse reflectance infrared Fourier transform (DRIFT) mode. It is usually said that quantitative analysis is possible only if both particle size distribution and sample density are perfectly controlled. However, even if these conditions are checked, instrumental factors are of great interest for the goodness of a curve fitting procedure, which is often necessary in solid sample studies. A factorial design achieved on anthron made it possible to obtain major trends concerning the required values for one instrumental parameter (resolution) and two mathematical treatments (zero filling and Savitsky-Golay (S-G) smoothing). Resolution was found to have the greatest effect on measured responses. A value of 2 cm(-1) according to the corresponding aperture is sufficient to approach the real width of bands for powdered samples. The use of a zero filling factor (ZFF) improves the apparent resolution by data interpolation. The best values found for instrumental parameters were applied to an anthron-anthracen mixture. The optimization of spectral features made it possible to obtain semi-quantitative results quite easily, in good agreement with the data corresponding to each pure compound. 相似文献
998.
Schneider BB Baranov VI Javaheri H Covey TR 《Journal of the American Society for Mass Spectrometry》2003,14(11):1236-1246
An atmosphere to vacuum interface was designed to exploit the different mobility and momentum characteristics of ions, and charged and neutral particles in electrospray ionization-mass spectrometry. The purpose of this device is to transmit with high efficiency the ions created at atmospheric pressure into the mass analyzer and to deflect the large charged and neutral particles prior to entrance into the vacuum system, thereby maintaining system cleanliness and stability. This interface is particularly suitable for low flow rate electrospray ionization-mass spectrometry where the close proximity of the electrospray emitters to the vacuum entrance, and near total consumption of the entire spray, leads to the production of large quantities of non-desolvated droplets and large charged and neutral particles. The improvement involves the application of potential gradients to a particle discriminator space located between the gas restricting ion entrance orifice of the mass spectrometer and the exit of a heated laminar flow chamber to divert large particles from the gas conductance limiting orifice. A counter-current flow of drying gas is used to deflect neutral particles and solvent vapor. Two stages of desolvation are achieved with the combined effects of the curtain gas and heated laminar flow chamber. This enhances the efficiency of desolvation and ion production, and stabilizes the resulting ion current under a wide variety of solvent compositions. In addition, this system eliminates the problems associated with the boiling of solution in nanospray tips when operated in close proximity to a heated mass spectrometer inlet. The particle discriminator interface gives approximately a 2-fold improvement in ion count rates, and a 3-fold improvement in stability (as measured by the signal relative standard deviation). 相似文献
999.
Hall MP Ashrafi S Obegi I Petesch R Peterson JN Schneider LV 《Journal of mass spectrometry : JMS》2003,38(8):809-816
We present a new class of "mass defect" tags with utility in biomolecular mass spectrometry. These tags, incorporating element(s) with atomic numbers between 17 (Cl) and 77 (Ir), have a substantially different nuclear binding energy (mass defect) from the elements common to biomolecules. This mass defect yields a readily resolvable mass difference between tagged and untagged species in high-resolution mass spectrometers. We present the use of a subset of these tags in a new protein sequencing application. This sequencing technique has advantages over existing mass spectral protein identification methodologies: intact proteins are quickly sequenced and unambiguously identified using only an inexpensive, robust mass spectrometer. We discuss the potential broader utility of these tags for the sequencing of other biomolecules, differential display applications and combinatorial methods. 相似文献
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