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951.
偏最小二乘-速差动力学分光光度法同时测定杀虫剂残杀威和异丙威两组分 总被引:11,自引:0,他引:11
采用速差动力学分光光度法对氨基甲酸脂类杀虫剂残杀威和异丙威进行同时测定,这两种化 的能在碱性条件下水解生成酚盐,进而与对氨基苯酚及高碘酸钾的反应产物醌亚胺发生偶联反应,生成蓝色化合物。反应的速率适中,可用于动力学分析。实验采集了多个时间点下538-700nm间的动力学-吸光度数据,构成量测矩阵,并采用偏最小二乘(PLS)法对量测数据进行解析。本文还对合成样品和环境水样中的残杀威和异丙威含量进行测定,获较好的结果。 相似文献
952.
Super/subcritical fluid chromatography chiral separations with macrocyclic glycopeptide stationary phases 总被引:2,自引:0,他引:2
Liu Y Berthod A Mitchell CR Xiao TL Zhang B Armstrong DW 《Journal of chromatography. A》2002,978(1-2):185-204
The chiral recognition capabilities of three macrocyclic glycopeptide chiral selectors, namely teicoplanin (Chirobiotic T), its aglycone (Chirobiotic TAG) and ristocetin (Chirobiotic R), were evaluated with supercritical and subcritical fluid mobile phases. A set of 111 chiral compounds including heterocycles, analgesics (nonsteroidal antiinflamatory compounds), beta-blockers, sulfoxides, N-protected amino acids and native amino acids was separated on the three chiral stationary phases (CSPs). All separations were done with an outlet pressure regulated at 100 bar, 31 degrees C and at 4 ml/min. Various amounts of methanol ranging from 7 to 67% (v/v) were added to the carbon dioxide along with small amounts (0.1 to 0.5%, v/v) of triethylamine and/or trifluoroacetic acid. The Chirobiotic TAG CSP was the most effective closely followed by the Chirobiotic T column. Both columns were able to separate, partially or fully, 92% of the enantiomers of the compound set. The ristocetin chiral selector could partially or baseline resolve only 60% of the enantiomers tested. All separations were done in less than 15 min and 70% were done in less than 4 min. The speed of the separations is the main advantage of the use of SFC compared to normal-phase HPLC. In addition, SFC is advantageous for preparative separations with easy solute recovery and solvent disposal. 相似文献
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956.
M. Q. Ling A. Yili H. A. Aisa Z. Bo O. N. Veshkurova Sh. I. Salikhov 《Chemistry of Natural Compounds》2011,46(6):932-934
A new peptide that had anti-oxidant activity and molecular weight 5,000.5 Da according to PAAG data and mass spectrometry
was isolated from celery seed using chromatographic methods. 相似文献
957.
The formation and co-existence of crystallographically modulated and non-modulated regions in (Ba,Sr)2TiSi2O8 fresnoites is reviewed, particularly the dependence on local composition. It is shown that perturbations of the average fresnoite structure, determined from appreciable single crystals, are in some cases better described as nanometric domain intergrowths where departures from ideal stoichiometry are characteristics of incommensuration, while modulation is absent from volumes that are less perturbed chemically. Evidence for this differentiation is obtained from selected area electron diffraction (SAED) patterns and high-resolution transmission electron microscopy (HRTEM) images. The domains are readily distinguished by their unique contrast in bright field electron micrographs. Fourier reconstructions of HRTEM images collected from areas with darker contrast show that modulation can change within relatively small volumes. Nearby areas with lighter contrast were found by SAED to be free of structural disorder and incommensurate reflections. 相似文献
958.
Ziyuan Li Ling Ma Changhua Tang Jinyi XuXiaoming Wu Hequan Yao 《Tetrahedron letters》2011,52(43):5643-5647
Oxidative Heck coupling of thiazole-4-carboxylates via palladium(II)-catalyzed C-H bond activation has been achieved in moderate to good yields. No ligand, and no acidic additive were used in the reaction. The results showed that this protocol tolerated a series of substitutions on the thiazole ring. A preliminary attempt of direct arylation with p-xylene via Pd(II)-catalyzed C-H bond activation has also been done. 相似文献
959.
The global responses characteristics of a rotor/stator rubbing system with dry friction effects 总被引:2,自引:0,他引:2
Rotor/stator rubbing systems may undertake a number of quite different responses. Recent experiments on rotor/stator rubbing have revealed that two or three different responses may coexist. In this paper the global response characteristics of a general rotor/stator rubbing system, which takes into account the dominant factors in the process of rotor/stator rubbing, especially, the dry friction effect that is mostly neglected in the previous works and is the main factor for the self-excited dry friction backward whirl, are studied. The different solutions of the piecewise nonlinear system are derived and their stability are analyzed to get the existence boundaries of the different responses. An overall picture of the global response characteristics of this model is then obtained by drawing the existence boundaries in a same parameter space. The present results provide good understanding on the coexistence of different rubbing responses observed in tests. Moreover, deeper insight into the types of coexistence of different rubbing responses and their relationship with the system parameters is gained. 相似文献
960.
A direct‐forcing immersed boundary‐lattice Boltzmann method (IB–LBM) is developed to simulate fluid–particle interaction problems. This method uses the pressure‐based LBM to solve the incompressible flow field and the immersed boundary method to handle the fluid–particle interactions. The pressure‐based LBM uses the pressure distribution functions instead of the density distribution functions as the independent dynamic variables. The main idea is to explicitly eliminate the compressible effect due to the density fluctuation. In the IB method, a direct‐forcing method is introduced to capture the particle motion. It directly computes an IB force density at each lattice grid from the differences between the pressure distribution functions obtained by the LBM and the equilibrium pressure distribution functions computed from the particle velocity. By applying this direct‐forcing method, the IB–LBM becomes a purely LBM version. Also, by applying the Gauss theorem, the formulas for computing the force and the torque acting on the particle from the flows are derived from the volume integrals over the particle volume instead of from the surface integrals over the particle surface. The order of accuracy of the IB–LBM is demonstrated on the errors of velocity field, wall stress, and gradients of velocity and pressure. As a demonstration of the efficiency and capabilities of the new method, sedimentation of a large number of spherical particles in an enclosure is simulated. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献