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951.
Application of chromatography technology in the separation of active alkaloids from Hypecoum leptocarpum and their inhibitory effect on fatty acid synthase 下载免费PDF全文
Qiulong Zhang Guangxiang Luan Tao Ma Na Hu Yourui Suo Xiaoyan Wang Xiaofeng Ma Chenxu Ding 《Journal of separation science》2015,38(23):4063-4070
A method that involved the combination of pH‐zone‐refining counter‐current chromatography and semipreparative reversed‐phase liquid chromatography has been established for the preparative separation of alkaloids from Hypecoum leptocarpum. From 1.2 g of crude sample, 31 mg N‐feruloyltyramine, 27 mg oxohydrastinine, 47 mg hydroprotopine, 25 mg leptopidine, and 18 mg hypecocarpine have been obtained. The structure of the new compound, hypecocarpine, is confirmed based on the analysis of spectroscopic data, including NMR, UV, and IR spectroscopy and positive electrospray ionization mass spectrometry. The known chemical structures were characterized on the basis of 1H and 13C NMR spectroscopy. The purities of the five alkaloids are all over 92.7% as determined by high‐performance liquid chromatography. The alkaloids’ cytotoxicity in breast cancer cells is assessed by using a Cell Counting Kit assay and their inhibitory effect on fatty acid synthase expression is assessed by a Western blot assay. These results suggest that leptopidine could suppress growth and induce cytotoxicity in breast cancer cells and that the cytotoxicity of leptopidine may be related to its inhibitory effect on fatty acid synthase expression. 相似文献
952.
Ryan J. Weiss Philip L. S. M. Gordts Dzung Le Ding Xu Jeffrey D. Esko Yitzhak Tor 《Chemical science》2015,6(10):5984-5993
Surfen, bis-2-methyl-4-amino-quinolyl-6-carbamide, was previously reported as a small molecule antagonist of heparan sulfate (HS), a key cell-surface glycosaminoglycan found on all mammalian cells. To generate structure–activity relationships, a series of rationally designed surfen analogs was synthesized, where its dimeric structure, exocyclic amines, and urea linker region were modified to probe the role of each moiety in recognizing HS. An in vitro assay monitoring inhibition of fibroblast growth factor 2 binding to wild-type CHO cells was utilized to quantify interactions with cell surface HS. The dimeric molecular structure of surfen and its aminoquinoline ring systems was essential for its interaction with HS, and certain dimeric analogs displayed higher inhibitory potency than surfen and were also shown to block downstream FGF signaling in mouse embryonic fibroblast cells. These molecules were also able to antagonize other HS–protein interactions including the binding of soluble RAGE to HS. Importantly, selected molecules were shown to neutralize heparin and other heparinoids, including the synthetic pentasaccharide fondaparinux, in a factor Xa chromogenic assay and in vivo in mice. These results suggest that small molecule antagonists of heparan sulfate and heparin can be of therapeutic potential for the treatment of disorders involving glycosaminoglycan–protein interactions. 相似文献
953.
Jiangwei Tian Jinfeng Zhou Zhen Shen Lin Ding Jun-Sheng Yu Huangxian Ju 《Chemical science》2015,6(10):5969-5977
This work reports a newly designed pH-activatable and aniline-substituted aza-boron-dipyrromethene as a trifunctional photosensitizer to achieve highly selective tumor imaging, efficient photodynamic therapy (PDT) and therapeutic self-monitoring through encapsulation in a cRGD-functionalized nanomicelle. The diethylaminophenyl is introduced in to the structure for pH-activatable near-infrared fluorescence and singlet oxygen (1O2) generation, and bromophenyl is imported to increase the 1O2 generation efficiency upon pH activation by virtue of its heavy atom effect. After encapsulation, the nanoprobe can target αvβ3 integrin-rich tumor cells via cRGD and is activated by physiologically acidic pH for cancer discrimination and PDT. The fascinating advantage of the nanoprobe is near-infrared implementation beyond 800 nm, which significantly improves the imaging sensitivity and increases the penetration depth of the PDT. By monitoring the fluorescence decrease in the tumor region after PDT, the therapeutic efficacy is demonstrated in situ and in real time, which provides a valuable and convenient self-feedback function for PDT efficacy tracking. Therefore, this rationally designed and carefully engineered nanoprobe offers a new paradigm for precise tumor theranostics and may provide novel opportunities for future clinical cancer treatment. 相似文献
954.
Yuantong Liang Chenguang Lu Defang Ding Man Zhao Dawei Wang Chao Hu Jieshan Qiu Gang Xie Zhiyong Tang 《Chemical science》2015,6(7):4103-4108
Graphene quantum dots (GQDs) are shown to serve as phase transfer agents to transfer various types of nanoparticles (NPs) from non-polar to polar solvents. Thorough characterization of the NPs proves complete native ligand exchange. Pellets of this GQD–NP composite show that the GQDs limit the crystal size during spark plasma sintering, yielding enhanced thermoelectric performance compared with NPs exchanged with inorganic ions. A photoluminescence study of the GQD–NP composite also suggests energy transfer from GQDs to NPs. 相似文献
955.
956.
Pengzuo Chen Kun Xu Zhiwei Fang Yun Tong Junchi Wu Xiuli Lu Xu Peng Hui Ding Changzheng Wu Yi Xie 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2015,127(49):14923-14927
Designing highly efficient electrocatalysts for oxygen evolution reaction (OER) plays a key role in the development of various renewable energy storage and conversion devices. In this work, we developed metallic Co4N porous nanowire arrays directly grown on flexible substrates as highly active OER electrocatalysts for the first time. Benefiting from the collaborative advantages of metallic character, 1D porous nanowire arrays, and unique 3D electrode configuration, surface oxidation activated Co4N porous nanowire arrays/carbon cloth achieved an extremely small overpotential of 257 mV at a current density of 10 mA cm−2, and a low Tafel slope of 44 mV dec−1 in an alkaline medium, which is the best OER performance among reported Co‐based electrocatalysts to date. Moreover, in‐depth mechanistic investigations demonstrate the active phases are the metallic Co4N core inside with a thin cobalt oxides/hydroxides shell during the OER process. Our finding introduces a new concept to explore the design of high‐efficiency OER electrocatalysts. 相似文献
957.
Monte Carlo simulation of full energy spectrum of electrons emitted from silicon in Auger electron spectroscopy 下载免费PDF全文
N. Cao B. Da Y. Ming S. F. Mao K. Goto Z. J. Ding 《Surface and interface analysis : SIA》2015,47(1):113-119
A Monte Carlo simulation including surface excitation, Auger electron‐ and secondary electron production has been performed to calculate the energy spectrum of electrons emitted from silicon in Auger electron spectroscopy (AES), covering the full energy range from the elastic peak down to the true‐secondary‐electron peak. The work aims to provide a more comprehensive understanding of the experimental AES spectrum by integrating the up‐to‐date knowledge of electron scattering and electronic excitation near the solid surface region. The Monte Carlo simulation model of beam–sample interaction includes the atomic ionization and relaxation for Auger electron production with Casnati's ionization cross section, surface plasmon excitation and bulk plasmon excitation as well as other bulk electronic excitation for inelastic scattering of electrons (including primary electrons, Auger electrons and secondary electrons) through a dielectric functional approach, cascade secondary electron production in electron inelastic scattering events, and electron elastic scattering with use of Mott's cross section. The simulated energy spectrum for Si sample describes very well the experimental AES EN(E) spectrum measured with a cylindrical mirror analyzer for primary energies ranging from 500 eV to 3000 eV. Surface excitation is found to affect strongly the loss peak shape and the intensities of the elastic peak and Auger peak, and weakly the low energy backscattering background, but it has less effect to high energy backscattering background and the Auger electron peak shape. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
958.
959.
In this paper, we presented a novel, rapid and highly sensitive sensor for glutathione (GSH), cysteine (Cys) and histidine (His) based on the recovered fluorescence of the carbon quantum dots (CQDs)–Hg(II) system. The CQDs were synthesized by microwave-assisted approach in one pot according to our previous report. The fluorescence of CQDs could be quenched in the presence of Hg(II) due to the coordination occurring between Hg(II) and functional groups on the surface of CQDs. Subsequently, the fluorescence of the CQDs–Hg(II) system was recovered gradually with the addition of GSH, Cys or His due to their stronger affinity with Hg(II). A good linear relationship was obtained from 0.10 to 20 μmol L−1 for GSH, from 0.20 to 45 μmol L−1 for Cys and from 0.50 to 60 μmol L−1 for His, respectively. This method has been successfully applied to the trace detection of GSH, Cys or His in human serum samples with satisfactory results. The proposed method was simple in design and fast in operation, which demonstrated great potential in bio-sensing fields. 相似文献
960.
Yanhua Huang Yuzhi WangQi Pan Ying WangXueqin Ding Kaijia XuNa Li Qian Wen 《Analytica chimica acta》2015
Four kinds of green deep eutectic solvents (DESs) based on choline chloride (ChCl) have been synthesized and coated on the surface of magnetic graphene oxide (Fe3O4@GO) to form Fe3O4@GO-DES for the magnetic solid-phase extraction of protein. X-ray diffraction (XRD), vibrating sample magnetometer (VSM), Fourier transform infrared spectrometry (FTIR), field emission scanning electron microscopy (FESEM) and thermal gravimetric analysis (TGA) were employed to characterize Fe3O4@GO-DES, and the results indicated the successful preparation of Fe3O4@GO-DES. The UV–vis spectrophotometer was used to measure the concentration of protein after extraction. Single factor experiments proved that the extraction amount was influenced by the types of DESs, solution temperature, solution ionic strength, extraction time, protein concentration and the amount of Fe3O4@GO-DES. Comparison of Fe3O4@GO and Fe3O4@GO-DES was carried out by extracting bovine serum albumin, ovalbumin, bovine hemoglobin and lysozyme. The experimental results showed that the proposed Fe3O4@GO-DES performs better than Fe3O4@GO in the extraction of acidic protein. Desorption of protein was carried out by eluting the solid extractant with 0.005 mol L−1 Na2HPO4 contained 1 mol L−1 NaCl. The obtained elution efficiency was about 90.9%. Attributed to the convenient magnetic separation, the solid extractant could be easily recycled. 相似文献