全文获取类型
收费全文 | 9390篇 |
免费 | 1184篇 |
国内免费 | 2834篇 |
专业分类
化学 | 10049篇 |
晶体学 | 222篇 |
力学 | 115篇 |
综合类 | 46篇 |
数学 | 15篇 |
物理学 | 2961篇 |
出版年
2024年 | 7篇 |
2023年 | 151篇 |
2022年 | 245篇 |
2021年 | 363篇 |
2020年 | 570篇 |
2019年 | 390篇 |
2018年 | 334篇 |
2017年 | 474篇 |
2016年 | 541篇 |
2015年 | 495篇 |
2014年 | 590篇 |
2013年 | 914篇 |
2012年 | 597篇 |
2011年 | 771篇 |
2010年 | 553篇 |
2009年 | 650篇 |
2008年 | 584篇 |
2007年 | 688篇 |
2006年 | 591篇 |
2005年 | 542篇 |
2004年 | 457篇 |
2003年 | 430篇 |
2002年 | 307篇 |
2001年 | 260篇 |
2000年 | 247篇 |
1999年 | 229篇 |
1998年 | 195篇 |
1997年 | 177篇 |
1996年 | 166篇 |
1995年 | 159篇 |
1994年 | 145篇 |
1993年 | 142篇 |
1992年 | 125篇 |
1991年 | 71篇 |
1990年 | 54篇 |
1989年 | 43篇 |
1988年 | 43篇 |
1987年 | 24篇 |
1986年 | 22篇 |
1985年 | 16篇 |
1984年 | 7篇 |
1983年 | 5篇 |
1982年 | 8篇 |
1981年 | 6篇 |
1980年 | 6篇 |
1978年 | 2篇 |
1977年 | 3篇 |
1973年 | 2篇 |
1972年 | 2篇 |
1968年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 140 毫秒
91.
In Situ Synthesis and Characterization of Poly(aryleneethynylene)‐Grafted Reduced Graphene Oxide 下载免费PDF全文
Sai Sun Dr. Xiaodong Zhuang Prof. Dr. Bo Liu Luxing Wang Linfeng Gu Prof. Dr. Sannian Song Prof. Dr. Bin Zhang Prof. Dr. Yu Chen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(7):2247-2252
Using highly soluble bromo‐functionalized reduced graphene oxide (RGBr) as a key graphene template for surface‐directing Sonogashira–Hagihara polymerization, a novel soluble poly(arylene‐ethynylene)‐grafted reduced graphene oxide, hereafter abbreviated as PAE‐g‐RGO, was prepared in situ. The entirely different electron distribution of LUMO and HOMO of PAE‐g‐RGO suggested the existence of a charge‐transfer (CT) state (PAE.?–RGO.+). The negative ΔGCS value (?2.57 eV) indicates that the occurrence of the charge separation via 1RGO* in o‐DCB is exothermic and favorable. Upon irradiation with 365 nm light, the light‐induced electron paramagnetic resonance (LEPR) spectrum of PAE‐g‐RGO showed a decrease in the spin‐state density owing to photoinduced intramolecular electron transfer events in this system. A sandwich‐type Al/PAE‐g‐RGO/ITO device showed representative bistable electrical switching behavior. The nonvolatile memory performance was attributed to the CT‐induced conductance changes, which was supported by molecular computation results and conductive atomic force microscopy (C‐AFM) images. 相似文献
92.
93.
Aleksandar Kremenovi Predrag Vuli 《Acta Crystallographica. Section C, Structural Chemistry》2014,70(3):256-259
The X‐ray powder diffraction pattern that corresponds to the disordered state of kalsilite (potassium aluminium orthosilicate), KAlSiO4, is investigated. The directionality of (Al,Si)O4 tetrahedra within single six‐membered tetrahedral ring building units (S6R) could not be defined. With equal probability for the directionality of each tetrahedra within one S6R [free apex pointing up (U) or down (D)], an undefined sequence of U and D directionalities is needed to describe the S6R building units. The extinction conditions of disordered kalsilite are also different compared to ordered kalsilite within the space group P63. In disordered kalsilite, h0l and hhl reflections with l = 2n + 1 are systematically absent. 相似文献
94.
ZnO‐Coated Carbon Nanotubes: Inter‐Diffusion of Carboxyl Groups and Enhanced Photocurrent Generation 下载免费PDF全文
Chia‐I Hung Dr. Hua‐Chiang Wen Yao‐Cheng Lai Dr. Shih‐Hsin Chang Prof. Dr. Wu‐Ching Chou Prof. Dr. Wen‐Kuang Hsu 《Chemphyschem》2015,16(4):812-816
ZnO is a defect‐governed oxide and emits light at both visible and UV regimes. This work employs atomic layer deposition to produce oxide particles on oxygenated carbon nanotubes, and the composites only show emission profiles at short wavelengths. The quenching of defect‐related emissions at long wavelengths is verified, owing to carboxyl diffusion into oxygen vacancies, and doping is supported by ZnCO3 formation in oxide lattice. Fully coated tubes display an increased photocurrent and the quantum efficiency increases by 22 % relative to the bare nanotubes. 相似文献
95.
Photocatalytically Renewable Micro‐electrochemical Sensor for Real‐Time Monitoring of Cells 下载免费PDF全文
Jia‐Quan Xu Yan‐Ling Liu Qian Wang Huan‐Huan Duo Xin‐Wei Zhang Dr. Yu‐Tao Li Prof. Wei‐Hua Huang 《Angewandte Chemie (International ed. in English)》2015,54(48):14402-14406
Electrode fouling and passivation is a substantial and inevitable limitation in electrochemical biosensing, and it is a great challenge to efficiently remove the contaminant without changing the surface structure and electrochemical performance. Herein, we propose a versatile and efficient strategy based on photocatalytic cleaning to construct renewable electrochemical sensors for cell analysis. This kind of sensor was fabricated by controllable assembly of reduced graphene oxide (RGO) and TiO2 to form a sandwiching RGO@TiO2 structure, followed by deposition of Au nanoparticles (NPs) onto the RGO shell. The Au NPs‐RGO composite shell provides high electrochemical performance. Meanwhile, the encapsulated TiO2 ensures an excellent photocatalytic cleaning property. Application of this renewable microsensor for detection of nitric oxide (NO) release from cells demonstrates the great potential of this strategy in electrode regeneration and biosensing. 相似文献
96.
Fe K‐Edge X‐ray Absorption Fine Structure Determination of γ‐Al2O3‐Supported Iron‐Oxide Species 下载免费PDF全文
Dr. Atsuko Tomita Dr. Takeshi Miki Takeru Tango Tatsuro Murakami Hideyuki Nakagawa Dr. Yutaka Tai 《Chemphyschem》2015,16(9):2015-2020
The structure of FeOx species supported on γ‐Al2O3 was investigated by using Fe K‐edge X‐ray absorption fine structure (XAFS) and X‐ray diffraction (XRD) measurements. The samples were prepared through the impregnation of iron nitrate on Al2O3 and co‐gelation of aluminum and iron sulfates. The dependence of the XRD patterns on Fe loading revealed the formation of α‐Fe2O3 particles at an Fe loading of above 10 wt %, whereas the formation of iron‐oxide crystals was not observed at Fe loadings of less than 9.0 wt %. The Fe K‐edge XAFS was characterized by a clear pre‐edge peak, which indicated that the Fe?O coordination structure deviates from central symmetry and that the degree of Fe?O?Fe bond formation is significantly lower than that in bulk samples at low Fe loading (<9.0 wt %). Fe K‐edge extended XAFS oscillations of the samples with low Fe loadings were explained by assuming an isolated iron‐oxide monomer on the γ‐Al2O3 surface. 相似文献
97.
Anchoring Mechanism of ZnO Nanoparticles on Graphitic Carbon Nanofiber Surfaces through a Modified Co‐Precipitation Method to Improve Interfacial Contact and Photocatalytic Performance 下载免费PDF全文
Dr. Gowra Raghupathy Dillip Dr. Arghya Narayan Banerjee Dr. Veettikunnu Chandran Anitha Dr. Sang Woo Joo Dr. Bong Ki Min Dr. Sandesh Y. Sawant Dr. Moo Hwan Cho 《Chemphyschem》2015,16(15):3214-3232
A facile three‐step co‐precipitation method is developed to synthesize graphitic carbon nanofibers (CNFs) decorated with ZnO nanoparticles (NPs). By interchanging intermediate steps of the reaction processes, two kinds of nanohybrids are fabricated with stark morphological and physicochemical differences. The morphologies differ because of the different chemical environments of the NP/nanocluster formation. The hybrid with larger and non‐uniform ZnO nanocluster size is formed in liquid phase and resulted in considerable interfacial defects that deteriorate the charge‐transfer properties. The hybrid with smaller and uniform ZnO NPs was formed in a dry solid phase and produced near‐defect‐free interfaces, leading to efficient charge transfer for superior photocatalytic performance. The results broaden the understanding of the anchoring/bonding mechanism in ZnO/CNF hybrid formation and may facilitate further development of more effective exfoliation strategies for the preparation of high‐performance composites/hybrids. 相似文献
98.
This study investigated the protective effects of the ethanolic extract of Mukia maderaspatana against indomethacin-induced gastric ulcer in rats. Gastric ulceration was induced by single intraperitoneal injection of indomethacin (30 mg/kg b.wt.). M. maderaspatana extract produced significant reduction in gastric mucosal lesions, malondialdehyde and serum tumour necrosis factor-α associated with a significant increase in gastric juice mucin content and gastric mucosal catalase, nitric oxide and prostaglandin E2 levels. The volume and acidity of the gastric juice decreased in pretreated rats. The plant extract was evaluated in the gastric juice of rats, untreated has showed near normal levels in pretreated rats. The M. maderaspatana was able to decrease acidity and increase the mucosal defence in the gastric area, therefore justifying its use as an antiulcerogenic agent. Ranitidine significantly increased pH value and decreased pepsin activity and gastric juice free and total acidity. The anti-ulcer effect was further confirmed histologically. 相似文献
99.
Application of magnetic graphitic carbon nitride nanocomposites for the solid‐phase extraction of phthalate esters in water samples 下载免费PDF全文
Magnetic graphitic carbon nitride nanocomposites were successfully prepared in situ and used to develop a highly sensitive magnetic solid‐phase extraction method for the preconcentration of phthalate esters such as di‐n‐butyl phthalate, butyl phthalate, dihexyl phthalate, and di‐(2‐ethyl hexyl) phthalate from water. The adsorption and desorption of the phthalate esters on magnetic graphitic carbon nitride nanocomposites were investigated and the parameters affecting the partition of the phthalate esters, such as adsorption, desorption, recovery, were assessed. Under the optimized conditions, the proposed method showed excellent sensitivity with limits of detection (S/N = 3) in the range of 0.05–0.1 μg/L and precision in the range of 1.1–2.6% (n = 5). This method was successfully applied to the analysis of real water samples, and good spiked recoveries over the range of 79.4–99.4% were obtained. This research provides a possibility to apply this nanocomposite for adsorption, preconcentration, or even removal of various carbon‐based ring or hydrophobic pollutants. 相似文献
100.
Preparation of a monolith functionalized with zinc oxide nanoparticles and its application in the enrichment of fluoroquinolone antibiotics 下载免费PDF全文
Dan Liu Jiutong Ma Yan Jin Xiqian Li Xiao Zhou Qiong Jia Weihong Zhou 《Journal of separation science》2015,38(1):134-140
This study describes the enrichment ability of ZnO‐modified methacrylic acid‐co‐ethylene dimethacrylate polymer monoliths as stationary phases for the simultaneous determination of antibiotics (ofloxacin, ciprofloxacin, enoxacin, and pefloxacin) combined with high‐performance liquid chromatography. The prepared monolith was characterized by scanning electron microscopy, X‐ray photoelectron spectroscopy, Fourier‐transformed infrared spectroscopy, and thermogravimetric analysis. The polymer monolith microextraction method has been applied to the enrichment of fluoroquinolone antibiotics and satisfactory results were obtained in the analysis of water samples. Compared with the conventional methacrylic acid based monolith, the developed monolith exhibited a higher enrichment capacity because of the introduction of zinc oxide into the preparation process. 相似文献