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991.
A novel solvent-relief-self-seeding (SRSS) process was applied to grow bulk polygonal tubular single crystals of Sb(2)E(3) (E = S, Se), using SbCl(3) and chalcogen elements E (E = S, Se) as the raw materials at 180 degrees C for 7 days in ethanol solution. The products were characterized by various techniques, including X-ray powder diffraction (XRD), scanning electronic microscope (SEM), transmission electronic microscope (TEM), electronic diffraction (ED), and X-ray photoelectron spectra (XPS). The calculated electrical resistivities of the tubular single crystals in the range 20-320 K were of the order of 10(5)-10(6) Omega cm for Sb(2)S(3) and 10(3)-10(4) Omega cm for Sb(2)Se(3), respectively. The studies of the optical properties revealed that the materials formed had a band gap of 1.72 eV for Sb(2)S(3) and 1.82 eV for Sb(2)Se(3), respectively. The optimal reaction conditions for the growth of bulk tubular single crystals were that the temperature was not lower than 180 degrees C and the reaction time was not shorter than 7 days. The possible growth mechanism of tubular crystals was also discussed. 相似文献
992.
SYNTHESIS OF ASILICA-SUPPORTED CARBOXYMETHYL CELLULOSE PLATINUM COMPLEX AND ITS CATALYTIC BEHAVIORS FOR HYDROGENATION OF ETHY... 相似文献
993.
The infrared (3200-40 cm(-1)) spectra of gaseous and solid 1,1-dicyclopropylethene, (c-C3H5)2C=CH2, along with the Raman (3200-40 cm(-1)) spectra of liquid and solid phases, have been recorded. The major trans-gauche (C=C bond trans to one ring with the other ring rotated about 60 degrees from the C=C bond, trivial C(1) symmetry) and gauche-gauche (the two three-membered rings rotated oppositely about 60 degrees from the C=C bond, C2 symmetry) rotamers have been confidently identified in the fluid phases, but no definitive spectroscopic evidence was found for the gauche-gauche' form (the two three-membered rings rotated to the same side about 60 degrees from the C=C bond, Cs symmetry), which is calculated to be present in no more than 6% at ambient temperature. Variable-temperature (-55 to -100 degrees C) studies of the infrared spectra of the sample dissolved in liquid xenon have been carried out. Utilizing six different combinations of pairs of bands from the C1 and C2 conformers, the average enthalpy difference between these two has been determined to be 146 +/- 30 cm(-1) (1.75 +/- 0.36 kJ x mol(-1)), with the C1 form more stable. Given statistical weights of 2:1:1 respectively for the C1, C2, and Cs forms, it is estimated that there are 75 +/- 2% C(1) and 19 +/- 1% C2 conformers present at ambient temperature. By utilizing predicted frequencies, infrared intensities, Raman activities, and band envelopes from scaled MP2(full)/6-31G(d) ab initio calculations, a complete vibrational assignment is made for the C1 form and a number of fundamentals of the C2 conformer have been identified. The structural parameters, dipole moments, and conformational stabilities have been obtained from ab initio calculations at the level of Hartree-Fock (RHF), the perturbation method to second order with full electron correlation (MP2(full)), and hybrid density functional theory (DFT) by the B3LYP method with a variety of basis sets. The predicted conformational stabilities from the MP2 calculations with relatively large basis sets are consistent with the experimental results. Structural parameters are estimated from the MP2(full)/6-311+G(d,p) predictions which are compared to the previously reported electron diffraction parameters. These experimental and theoretical results are compared to the corresponding quantities of some similar molecules. 相似文献
994.
A dicyano-containing [Fe(bpb)(CN)2]- building block has been employed for the synthesis of cyano-bridged heterometallic Ni(II)-Fe(III) complexes. The presence of steric bpb(2-) ligand around the iron ion results in the formation of low-dimensional species: five are neutral NiFe2 trimers and three are one-dimensional (1D). The structure of the 1D complexes consists of alternating [NiL]2+ and [Fe(bpb)(CN)2]- generating a cyano-bridged cationic polymeric chain and the perchlorate as the counteranion. In all complexes, the coordination geometry of the nickel ions is approximately octahedral with the cyano nitrogen atoms at the trans positions. Magnetic studies of seven complexes show the presence of ferromagnetic interaction between the metal ions through the cyano bridges. Variable temperature magnetic susceptibility investigations of the trimeric complexes yield the following J(NiFe) values (based on the spin exchange Hamiltonian H = -2J(NiFe) S(Ni) (S(Fe(1)) + S(Fe(2))): J(NiFe) = 6.40(5), 7.8(1), 8.9(2), and 6.03(4) cm(-1), respectively. The study of the magneto-structural correlation reveals that the cyanide-bridging bond angle is related to the strength of magnetic exchange coupling: the larger the Ni-N[triple bond]C bond angle, the stronger the Ni- - -Fe magnetic interaction. One 1D complex exhibits long-range antiferromagnetic ordering with T(N) = 3.5 K. Below T(N) (1.82 K), a metamagnetic behavior was observed with the critical field of approximately 6 kOe. The present research shows that the [Fe(bpb)(CN)2]- building block is a good candidate for the construction of low-dimensional magnetic materials. 相似文献
995.
Sun Z Zheng X Hoshi T Kashiwagi Y Anzai J Li G 《Analytical and bioanalytical chemistry》2004,380(3):545-550
Ligustrazine is one of the active ingredients contained in Ligusticum chuanxiong Hort. (Umbelliferae), which is widely used in traditional Chinese medicine for the treatment of cardiovascular problems. In this work, the electrochemistry of Ligustrazine hydrochloride (LZC) and its determination are investigated. The detection limit is estimated to be 8.0×10–8 M, with three linear ranges from 1.0×10–6 to 1.0×10–4 M, 1.0×10–4 to 5.0×10–4 M, and 6.5×10–4 to 1.6×10–3 M. The method has been proved to be highly sensitive, selective, and stable, and has been successfully applied to determining LZC in LZC injections. 相似文献
996.
997.
Huang WL Cui SH Liang KM Gu SR Yuan ZF 《Journal of colloid and interface science》2002,246(1):129-134
Silica xerogels were prepared by thermal drying wet gels in an electric oven (70 degrees C) after certain duration of ambient drying, and the relevant effect is investigated on the mesopore structures and surface fractal dimensions of the resultant xerogels. The silica gels were derived from a hydrochloric acid-catalyzed TEOS (tetraethylorthaosilicate) system, and both magnetic stirring and ultrasonic vibration were adopted during sol preparation. The percentage mesoporosity and surface fractal dimensions are evaluated using image analysis methods, based on FE-SEM (field emission gun-scanning electron microscopy) images. The results show that the mesoporosity of the resultant xerogels decreases with the duration of ambient drying for samples prepared using magnetic stirring and low-intensity ultrasonic vibration, while samples subjected to high-intensity ultrasound show a somewhat reverse trend. Samples prepared with magnetic stirring have almost constant surface fractal dimensions (nearly 3), irrespective of the ambient drying before thermal drying. The surface fractal dimensions of samples prepared using ultrasound increase with the duration of ambient drying. 相似文献
998.
By combining the layer-by-layer (LBL) self-assembly technique with the electrochemical polymerization method, multilayer Ni(II)-polyluminol
films were modified on the surface of a vaseline-impregnated graphite electrode. It was found that, compared with an electrode
modified by direct electrochemical polymerization, this modified electrode offered a suitable ECL reaction micro-environment
created by the special multilayer films, which was beneficial to the ephedrine hydrochloride enhancing effect for luminol
ECL intensity. The ECL enhancing effect of ephedrine hydrochloride on the electro-oxidation luminol was improved on this modified
electrode. Based on this finding, a new sensitive ECL method was developed for ephedrine hydrochloride determination under
the optimal conditions. At the same time, a new idea is proposed for improving the analytical performance of the luminol ECL
system by modifying the ECL reaction micro-environment with the layer-by-layer self- assembly method. Under the optimum experimental
conditions, the ephedrine hydrochloride concentration in the range of 2.0 × 10−8–7.0 × 10−6 mol L−1 was proportional to the enhanced ECL signal, and it offered an 8.0 × 10−9 mol L−1 detection limit for ephedrine hydrochloride. 相似文献
999.
Zheng‐Yu Yue Shu‐Hui Li Po Gao Jin‐Hui Zhang Peng‐Fei Yan 《Acta Crystallographica. Section C, Structural Chemistry》2006,62(5):o281-o282
The title compound, C30H46O9, prepared from a mixture of α‐ and β‐dihydroartemisinin, has α‐ and β‐arteether moieties linked via an –O– bridge, so that the molecule is asymmetric about the bridge. The endoperoxide bridges of the parent compounds have been retained in each half of the ether‐bridged dimer. The rings exhibit chair and twist–boat conformations. 相似文献
1000.
采用SCC-DV-Xα方法对α-Keggin结构硅钼二电子还原态杂多蓝阴离子[SiMo2(V)Mo10(VI)O40]6-和它的混合型钒取代物[SiV2(V)Mo10(VI)O40]6-进行了量子化学计算,获得了轨道能级、费米能级、各原子价电子布居、自由价态密度分析和分子轨道成分等信息.理论分析表明该杂多阴离子中所有原子Si、Mo、V、Oa、Ob、Oc和Od都参与反应,Oc和Od的成键能力较强,化学活性较大,有力地支持了实验结果.中心硅氧四面体结构发生畸变很小,但构成三金属簇的八面体结构都发生了较明显的畸变,其整体仍然保持α-Keggin结构.钒的取代增强了Mo2VO13三金属族中Od的活性.预测这两种杂多阴离子都有被继续还原和取代的趋势,[SiMo2(V)Mo10(VI)O40]6-的趋势更强. 相似文献