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951.
Formation and stability of paraffin oil-in-water nano-emulsions prepared by the emulsion inversion point method 总被引:1,自引:0,他引:1
Paraffin oil-in-water nano-emulsions stabilized by Tween 80/Span 80 were prepared using the emulsion inversion point method at different emulsification temperatures. Nano-emulsions with droplet size below 200 nm were formed above a critical surfactant-to-oil ratio of 0.20 at 50 degrees C. The main destabilization mechanism of the systems was found to be Ostwald ripening. An interesting phenomenon was that the Ostwald ripening rate declined as the surfactant concentration rose. Furthermore, flocculation was also found to contribute to the instability of the nano-emulsions, especially for those with low surfactant concentrations. Study on the electrophoretic properties of emulsion droplets revealed a negative value of the zeta potential, which was strongly dependent on the pH of the systems. 相似文献
952.
A case study was conducted to determine the relative response factors (RRFs) of paclitaxel-related impurities by high performance liquid chromatography (HPLC) equipped with an ultraviolet (UV) detector and charged aerosol detector (CAD) in tandem. The peak response using CAD was independent of analyte structure in an isocratic analysis for this application. After a sample containing known and unknown impurities was analyzed with HPLC-UV-CAD, an empirical approach was developed to calculate the RRFs for all impurities. The RRFs of known impurities were also determined by linear calibration curves. For known impurities, the RRFs values determined with two approaches are comparable. The new approach is effective yet simpler to determine the RRFs for unknown impurities or degradation products since the need for obtaining authentic pure materials was eliminated. 相似文献
953.
A novel, simple, and economic method, hollow-fiber ultrafiltration followed by centrifugation, has been developed for separation of viscid substances with similar properties except for different molecular weight. The experimental assembly needed only a U-shaped hollow fiber containing the sample solution with both ends of the fiber connected to two syringe needles. Ultrafiltration was performed by the action of centrifugal force. Concentration polarization was overcome and no phase transition occurred. Satisfactory recovery was achieved. 相似文献
954.
A differential method for analyzing first-order kinetic data is presented. While the essence of this approach has been known for almost a century, the use of computers to collect, store, and manipulate data has reenergized this innovative idea. Based on the equation ln |dA1/dt| = ln |k(Ao - A(infinity))| − kt, plots of ln |dAt/dt| vs. t were found to be lienar for both simulated kinetic data and data collected for the reaction of [(en)2Co(SCH2CH2NH2)]2+ with acrylamide. The rate constants for the reaction obtained by this method are identical to those obtained by the infinite-time method of analysis but do not require infinite-time measurements in their evaluation. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 333–338, 1997 相似文献
955.
We previously reported the preparation of the salbutamol sulfate pulsatile-release capsules with the pH-sensitive ion exchange resin as the carriers. In the present study, we investigated the pharmacokinetics of the salbutamol sulfate pulsatile-release capsules in beagle dogs. The analysis method was established for the drugs in vivo by HPLC method. The pharmacokinetics parameters of pulsatile-release salbutamol sulfate and reference tablet were AUC(0-24) (ng.h/ml) 1031.8+/-123.1, 1112.6+/-118.24, Cmax (ng/ml) 172.4+/-21.4, 179.3+/-26.1, Tmax (h) 3.8+/-0.6, 1.5+/-0.5, Tlag (h) 2.7+/-0.5, 0.3+/-0.2. The results showed that the test dosage forms was bioequivalent with reference dosage form, and had an obviously pulsatile-release effect. 相似文献
956.
The adiabatic molecular wavefunctions in the H + H2 system are obtained in one dimension by solving the double-well potential problem. In three dimensions, the corresponding linear adiabatic molecular wavefunctions are obtained. A comparison between these wavefunctions clearly suggests that the probability of reaction is smaller in three dimensions. 相似文献
957.
A method is proposed to prepare β-cyclodextrin (β-CD)/polyaniline (PANI) inclusion complex. In this route, benzoyl peroxide (BPO, the oxidant) is first encapsulated into the cavity of β-CD. Aniline is then carried into the cavity of β-CD by supercritical (SC) CO2, which polymerizes in situ to form inclusion complex. The product is characterized by FT-IR, UV-Vis, 1H NMR and XRD techniques. The results suggest that the columnar inclusion complexes may be formed. 相似文献
958.
Liu H Zhang S Nie S Zhao X Sun X Yang X Pan W 《Chemical & pharmaceutical bulletin》2005,53(6):631-633
Methylacrylic acid/styrene cross-linked with divinylbenzene is a novel pH-sensitive ion exchange resin. Microspheres of this resin were characterized by Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC). The microspheres showed a pulsatile swelling behavior when the pH of the media changed. The pH-sensitive microspheres were loaded with salbutamol sulfate and the drug-release characteristics were studied under both simulated gastric and intestinal pH conditions. The results obtained showed that the drug release also depended on the pH of the release media. 相似文献
959.
The geometric and electronic structures of poly(9,9-dioctylfluorene) (PFO) oligomer interacting with Ca atoms were studied using M?ller-Plesset perturbation theory. A weak interaction with little charge transfer and with a relatively long Ca-C distance (about 4.0 Angstrom) was found when only one Ca atom was attached to a PFO unit. However, when two Ca atoms were adsorbed at a PFO unit, a strong interaction with a shorter Ca-C distance (about 2.67 Angstrom) took place with considerable charge transfer from the Ca atom to the PFO, resulting in significant deformation in the backbone of the PFO oligomer. In the latter case, the frontier orbitals of the PFO were modified. However, the deformed PFO and its modified frontier orbitals could be recovered when oxygen was added, which is in good agreement with experimental observation. 相似文献
960.
Zhaofei Li Junliang Sun Chun-K. Loong Fuhui Liao 《Journal of solid state chemistry》2005,178(11):3315-3322
A powder sample of Sr3FeMoO7 was synthesized by solid-state reaction in reduced atmosphere (5% H2/Ar). At room temperature, Sr3FeMoO7 crystallizes in a typical Ruddlesden-Popper (n=2) structure in the space group I4/mmm, and . The structure refinement indicates that the Fe and Mo ions are randomly distributed in a single B-site with small fraction of B-site and oxygen vacancies. At low temperature, long-range magnetic interaction was observed. The antiferromagnetic magnetic interaction can be described with a large unit cell, and cm=cn, in the magnetic space group An′. 相似文献