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951.
标准物质基体对马拉硫磷气相色谱响应的影响 总被引:1,自引:0,他引:1
对马拉硫磷在甲醇、丙酮、乙酸乙酯、二氯甲烷4种溶剂中的气相色谱峰单位浓度面积响应进行了研究,用t检验法判定响应差异性.研究结果证明,浓度相同但溶剂不同的马拉硫磷溶液,在其它实验条件均相同的情况下,气相色谱峰单位浓度面积响应有显著性差异;用前处理后待测样浓缩液的基体稀释对照样,可以减小或消除马拉硫磷标准物质基体与方法中要求的标准储备液基体的差异性所带来的对待测样检测结果的影响. 相似文献
952.
953.
Jia Jia Ke Wang Dr. Wen Shi Suming Chen Xiaohua Li Dr. Huimin Ma Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(22):6638-6643
A new water‐soluble reagent, rhodamine B piperazinoacetohydrazine (RBPH), with improved spectroscopic and reaction properties, has been developed and characterized for pyruvic acid labeling. The reagent RBPH is designed and synthesized by using rhodamine B as a spectroscopic unit, and hydrazine as a carbonyl‐specific labeling unit; the two units are connected by a well‐chosen linker of piperazine, which prohibits the formation of the nonfluorescent spirocyclic structure of rhodamine B, thereby keeping the spectroscopic response of the reagent in a stable state. Such a design enables RBPH not only to maintain its excellent spectroscopic properties over a wide pH range, but also to exist as a stable cation with high water solubility. Moreover, the hydrazino group of RBPH is expected to react selectively with carbonyl compounds under mild conditions through the rapid formation of hydrazones. These important features make RBPH of great potential use in the labeling of aldehydes or ketones in various biosystems, and such an application of RBPH as a precolumn derivatizing reagent has been successfully demonstrated on the analysis of pyruvic acid in human serum by high‐performance liquid chromatography with common UV/Vis detection. 相似文献
954.
Zhen Wang Donghui Chen Zhigang Yang Sha Bai Xiaohua Liu Dr. Lili Lin Dr. Xiaoming Feng Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(33):10130-10136
Highly enantioselective Michael addition of 1,3‐dicarbonyl compounds and nitromethane to 4‐oxo‐4‐arylbutenoates catalyzed by N,N′‐dioxide–Sc(OTf)3 complexes has been developed. Using 0.5–2 mol % catalyst loading, various α‐stereogenic esters were obtained regioselectively with excellent yields (up to 97 %) and enantioselectivities (up to >99 % ee). Moreover, the reaction performed well under nearly solvent‐free conditions. The products with functional groups are ready for further transformation, which showed the potential value of the catalytic approach. According to the experimental results and previous reports, a plausible working model has been proposed to explain the origin of the activation and the asymmetric induction. 相似文献
955.
Xiaohong Chen Yin Zhu Zhen Qiao Mingsheng Xie Lili Lin Dr. Xiaohua Liu Dr. Xiaoming Feng Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(33):10124-10129
An easily available and efficient chiral N,N′‐dioxide–nickel(II) complex catalyst has been developed for the direct catalytic asymmetric aldol reaction of α‐isothiocyanato imide with aldehydes which produces the products in morderate to high yields (up to 98 %) with excellent diastereo‐ (up to >99:1 d.r.) and enantioselectivities (up to >99 % ee). A variety of aromatic, heteroaromatic, α,β‐unsaturated, and aliphatic aldehydes were found to be suitable substrates in the presence of 2.5 mol % L ‐proline‐derived N,N′‐dioxide L5 –nickel(II) complex. This process was air‐tolerant and easily manipulated with available reagents. Based on experimental investigations, a possible transition state has been proposed to explain the origin of reactivity and asymmetric inductivity. 相似文献
956.
以氟甲砜霉素作内标,乙腈作为提取溶剂,采用高效液相色谱内标法检测鸡血浆中甲砜霉素的浓度。色谱柱为Shim-pack CLC-ODS(150 mm×6 mm,5μm),流动相为乙腈-水(体积比25∶75),流速为1.0 mL/min,检测波长为225 nm,柱温为40℃。在此色谱条件下,在0.25~32.00 mg/L浓度范围内,甲砜霉素浓度与甲砜霉素和氟甲砜霉素峰面积比呈线性关系,相关系数r为0.9999,最低检测浓度为0.1 mg/L;在高、中、低3个浓度水平下日内、日间精密度均大于6.1%(n=5),提取回收率大于98.68%,方法回收率为99.20%~100.25%。建立的方法符合生物样品的分析要求,可用于临床药代动力学研究。 相似文献
957.
Haili Pang Changting Huang Jinhua Chen Bo Liu Yafei Kuang Xiaohua Zhang 《Journal of Solid State Electrochemistry》2010,14(2):169-174
Polyaniline–tin dioxide (PANI-SnO2) composites were prepared by chemical polymerization method, and characterized by scanning electron microscopy, transmission
electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction. Due to the good stability in diluted
acidic solution, PANI-SnO2 composites were selected as the catalyst support and second catalyst for methanol electro-oxidation. The electrocatalytic
properties of the PANI-SnO2 supported Pt catalyst (Pt/PANI-SnO2) for methanol oxidation have been investigated by cyclic voltammetry, chronoamperometry, and chronopotentiometry. Under the
same loading mass of Pt, the Pt/PANI-SnO2 catalyst shows higher electrocatalytic activity towards methanol electro-oxidation than Pt/SnO2 catalyst. 相似文献
958.
Haiyong Li Xiaohua Zhang Haili Pang Changting Huang Jinhua Chen 《Journal of Solid State Electrochemistry》2010,14(12):2267-2274
Graphene nanosheets, synthesized by a modified Hummers method, have been functionalized by PMo12, and used as the supports of the PtRu nanoparticles. The electrocatalytic properties of the resultant nanocatalysts (PtRu/PMo12-Graphene) for methanol electro-oxidation have been evaluated by cyclic voltammetry and chronoamperometry. The micrograph
and the elemental composition have also been investigated by transmission electron microscopy and energy dispersive X-ray
spectroscopy. The results suggest that the addition of PMo12 benefits the high dispersion of graphene nanosheets in the water and the uniform dispersion of the PtRu nanoparticles on
the graphene nanosheets, and the PtRu/PMo12-Graphene catalysts have higher electrocatalytic activity and better electrochemical stability for methanol oxidation compared
to the PtRu/Graphene catalysts. 相似文献
959.
960.