全文获取类型
收费全文 | 88914篇 |
免费 | 2446篇 |
国内免费 | 1775篇 |
专业分类
化学 | 31746篇 |
晶体学 | 939篇 |
力学 | 7478篇 |
综合类 | 105篇 |
数学 | 33065篇 |
物理学 | 19802篇 |
出版年
2023年 | 279篇 |
2022年 | 467篇 |
2021年 | 541篇 |
2020年 | 500篇 |
2019年 | 508篇 |
2018年 | 10752篇 |
2017年 | 10560篇 |
2016年 | 6620篇 |
2015年 | 1420篇 |
2014年 | 985篇 |
2013年 | 1140篇 |
2012年 | 4804篇 |
2011年 | 11442篇 |
2010年 | 6375篇 |
2009年 | 6716篇 |
2008年 | 7257篇 |
2007年 | 9320篇 |
2006年 | 844篇 |
2005年 | 1840篇 |
2004年 | 1871篇 |
2003年 | 2256篇 |
2002年 | 1306篇 |
2001年 | 472篇 |
2000年 | 495篇 |
1999年 | 359篇 |
1998年 | 365篇 |
1997年 | 347篇 |
1996年 | 375篇 |
1995年 | 277篇 |
1994年 | 213篇 |
1993年 | 189篇 |
1992年 | 140篇 |
1991年 | 141篇 |
1990年 | 128篇 |
1989年 | 127篇 |
1988年 | 111篇 |
1987年 | 86篇 |
1986年 | 101篇 |
1985年 | 78篇 |
1984年 | 60篇 |
1983年 | 51篇 |
1982年 | 56篇 |
1981年 | 45篇 |
1980年 | 55篇 |
1979年 | 46篇 |
1914年 | 45篇 |
1913年 | 40篇 |
1912年 | 40篇 |
1909年 | 41篇 |
1908年 | 40篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Imaging of Colorectal Cancers Using Activatable Nanoprobes with Second Near‐Infrared Window Emission 下载免费PDF全文
Ge Xu Qinglong Yan Xiaoguang Lv Prof. Ying Zhu Kai Xin Ben Shi Rongchen Wang Jian Chen Wei Gao Prof. Ping Shi Prof. Chunhai Fan Prof. Chunchang Zhao Prof. He Tian 《Angewandte Chemie (International ed. in English)》2018,57(14):3626-3630
Fluorescent probes in the second near‐infrared window (NIR‐II) allow high‐resolution bioimaging with deep‐tissue penetration. However, existing NIR‐II materials often have poor signal‐to‐background ratios because of the lack of target specificity. Herein, an activatable NIR‐II nanoprobe for visualizing colorectal cancers was devised. This designed probe displays H2S‐activated ratiometric fluorescence and light‐up NIR‐II emission at 900–1300 nm. By using this activatable and target specific probe for deep‐tissue imaging of H2S‐rich colon cancer cells, accurate identification of colorectal tumors in animal models were performed. It is anticipated that the development of activatable NIR‐II probes will find widespread applications in biological and clinical systems. 相似文献
992.
High‐Flux Membranes Based on the Covalent Organic Framework COF‐LZU1 for Selective Dye Separation by Nanofiltration 下载免费PDF全文
Dr. Hongwei Fan Jiahui Gu Prof. Hong Meng Alexander Knebel Prof. Dr. Jürgen Caro 《Angewandte Chemie (International ed. in English)》2018,57(15):4083-4087
Covalent organic frameworks (COFs) are attractive candidates for advanced water‐treatment membranes owing to their high porosity and well‐organized channel structures. Herein, the continuous two‐dimensional imine‐linked COF‐LZU1 membrane with a thickness of only 400 nm was prepared on alumina tubes by in situ solvothermal synthesis. The membrane shows excellent water permeance (ca. 760 L m?2 h?1 MPa?1) and favorable rejection rates exceeding 90 % for water‐soluble dyes larger than 1.2 nm. The water permeance through the COF‐LZU1 membrane is much higher than that of most membranes with similar rejection rates. Long‐time operation demonstrates the outstanding stability of the COF‐LZU1 membrane. As the membrane has no selectivity for hydrated salt ions (selectivity <12 %), it is also suitable for the purification of dye products from saline solutions. The excellent performance and the outstanding water stability render the COF‐LZU1 membrane an interesting system for water purification. 相似文献
993.
Dr. Qi Liu Dr. Zhilei Ge Dr. Xiuhai Mao Dr. Guobao Zhou Prof. Xiaolei Zuo Dr. Juwen Shen Dr. Jiye Shi Prof. Jiang Li Prof. Lihua Wang Prof. Xiaoqing Chen Prof. Chunhai Fan 《Angewandte Chemie (International ed. in English)》2018,57(24):7131-7135
Weak ligand–receptor recognition events are often amplified by recruiting multiple regulatory biomolecules to the action site in biological systems. However, signal amplification in in vitro biomimetic systems generally lack the spatiotemporal regulation in vivo. Herein we report a framework nucleic acid (FNA)‐programmed strategy to develop valence‐controlled signal amplifiers with high modularity for ultrasensitive biosensing. We demonstrated that the FNA‐programmed signal amplifiers could recruit nucleic acids, proteins, and inorganic nanoparticles in a stoichiometric manner. The valence‐controlled signal amplifier enhanced the quantification ability of electrochemical biosensors, and enabled ultrasensitive detection of tumor‐relevant circulating free DNA (cfDNA) with sensitivity enhancement of 3–5 orders of magnitude and improved dynamic range. 相似文献
994.
Eosin Y as a Direct Hydrogen‐Atom Transfer Photocatalyst for the Functionalization of C−H Bonds 下载免费PDF全文
Xuan‐Zi Fan Dr. Jia‐Wei Rong Hao‐Lin Wu Quan Zhou Dr. Hong‐Ping Deng Jin Da Tan Cheng‐Wen Xue Dr. Li‐Zhu Wu Dr. Hai‐Rong Tao Dr. Jie Wu 《Angewandte Chemie (International ed. in English)》2018,57(28):8514-8518
Eosin Y, a well‐known economical alternative to metal catalysts in visible‐light‐driven single‐electron transfer‐based organic transformations, can behave as an effective direct hydrogen‐atom transfer catalyst for C?H activation. Using the alkylation of C?H bonds with electron‐deficient alkenes as a model study revealed an extremely broad substrate scope, enabling easy access to a variety of important synthons. This eosin Y‐based photocatalytic hydrogen‐atom transfer strategy is promising for diverse functionalization of a wide range of native C?H bonds in a green and sustainable manner. 相似文献
995.
Rational Fabrication of Anti‐Freezing,Non‐Drying Tough Organohydrogels by One‐Pot Solvent Displacement 下载免费PDF全文
Fan Chen Dan Zhou Jiahui Wang Tianzhen Li Prof. Dr. Xiaohu Zhou Dr. Tiansheng Gan Dr. Stephan Handschuh‐Wang Prof. Dr. Xuechang Zhou 《Angewandte Chemie (International ed. in English)》2018,57(22):6568-6571
Tough hydrogels, polymeric network structures with excellent mechanical properties (such as high stretchability and toughness), are emerging soft materials. Despite their remarkably mechanical features, tough hydrogels exhibit two flaws (freezing around the icing temperatures of water and drying under arid conditions). Inspired by cryoprotectants (CPAs) used in the inhibition of the icing of water in biological samples, a versatile and straightforward method is reported to fabricate extreme anti‐freezing, non‐drying CPA‐based organohydrogels with long‐term stability by partially displacing water molecules within the pre‐fabricated hydrogels. CPA‐based Ca‐alginate/polyacrylamide (PAAm) tough hydrogels were successfully fabricated with glycerol, glycol, and sorbitol. The CPA‐based organohydrogels remain unfrozen and mechanically flexible even up to ?70 °C and are stable under ambient conditions or even vacuum. 相似文献
996.
A novel honeycomb-shaped PtSnNa/γ-Al2O3/cordierite monolithic catalyst was developed. It was found that, the unique structure of the material led to the improved catalyst performances versus the conventional granule catalyst. 相似文献
997.
Lithium garnet based free-standing solid polymer composite membrane for rechargeable lithium battery
Electrolytes with high lithium-ion conductivity, better mechanical strength and large electrochemical window are essential for the realization of high-energy density lithium batteries. Polymer electrolytes are gaining interest due to their inherent flexibility and nonflammability over conventional liquid electrolytes. In this work, lithium garnet composite polymer electrolyte membrane (GCPEM) consisting of large molecular weight (Wavg ~?5?×?106) polyethylene oxide (PEO) complexed with lithium perchlorate (LiClO4) and lithium garnet oxide Li6.28Al0.24La3Zr2O12 (Al-LLZO) is prepared by solution-casting method. Significant improvement in Li+ conductivity for Al-LLZO containing GCPEM is observed compared with the Al-LLZO free polymer membrane. Maximized room temperature (30 °C) Li+ conductivity of 4.40?×?10?4 S cm?1 and wide electrochemical window (4.5 V) is observed for PEO8/LiClO4?+?20 wt% Al-LLZO (GCPEM-20) membrane. The fabricated cell with LiCoO2 as cathode, metallic lithium as anode and GCPEM-20 as electrolyte membrane delivers an initial charge/discharge capacity of 146 mAh g?1/142 mAh g?1 at 25 °C with 0.06 C-rate. 相似文献
998.
Susmitha Uppugalla Rajender Boddula Palaniappan Srinivasan 《Journal of Solid State Electrochemistry》2018,22(2):407-415
In this work, organic-inorganic composite materials of polyaniline and manganese oxide were synthesized and investigated their electrochemical performance. This composite material was prepared by oxidizing aniline with methyl triphenylphosphonium permanganate as a novel organic oxidant via aqueous, emulsion, and interfacial polymerization pathways. This process led to the formation of polyaniline-sulfate salt (PANI-SA-Mn5O8). Formation of polyaniline-sulfate salt was confirmed from FT-IR, EDAX, and XRD results. Formation of Mn5O8 was supported by XRD spectrum. PANI-SA-Mn5O8 prepared via emulsion polymerization pathway was obtained in porous nanorod morphology with high conductivity (9.4 S cm?1) compared to that of the other sample prepared via interfacial pathway (1.7 S cm?1). Whereas, aqueous polymerization pathway resulted in sheet-like morphology with a conductivity of 0.8 S cm?1. These composites were used as pseudocapacitive electrode materials. Electrochemical characterization (cyclic voltammetry, charge-discharge, and electrochemical impedance measurement) showed that composite prepared via emulsion polymerization pathway gave better electrochemical performance, and showed good cycling behavior. 相似文献
999.
Cristiane Antoniazzi Camila Alves de Lima Rafael Marangoni Almir Spinelli Eryza Guimarães de Castro 《Journal of Solid State Electrochemistry》2018,22(5):1373-1383
This paper reports the voltammetric determination of 17β-estradiol in urine and buttermilk samples using a simple detector based on a carbon paste electrode (CPE) modified with copper(II) oxide (CuO). The CuO was obtained by the Pechini method and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive (EDS), Fourier transform infrared (FTIR), and Raman spectroscopies. Cyclic voltammetry (CV) and square-wave voltammetry (SWV) demonstrated that the CuO-modified carbon paste electrode (CuO/CPE detector) displayed much higher electrocatalytic activity in the 17β-estradiol oxidation reaction than the CPE without modification, exhibiting a low detection limit of 21.0 nmol L?1 with a wide linear range from 60.0 to 800.0 nmol L?1 (R = 0.998). Satisfactory results were obtained for the determination of 17β-estradiol in human urine and buttermilk samples. The proposed electrochemical detector offers high repeatability, stability, fast response, low cost, and potential for practical application in the quantification of this hormone. 相似文献
1000.
Fernanda Moreira Tatiane de Andrade Maranhão Almir Spinelli 《Journal of Solid State Electrochemistry》2018,22(5):1303-1313
A carbon paste electrode (CPE) modified with Fe3O4 nanoparticles (Fe3O4 NP) and the ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate (IL BMI.PF6) was employed for the electroanalytical determination of estrone (E1) by square-wave voltammetry (SWV). At the modified electrode, cyclic voltammograms of E1 in B–R buffer (pH 12.0) showed an adsorption-controlled irreversible oxidation peak at around +0.365 V. The anodic current increased by a factor of five times and the peak potential shifted 65 mV to less positive values compared with the unmodified CPE. Under optimized conditions, the calibration curve obtained showed two linear ranges: from 4.0 to 9.0 μmol L?1 and from 9.0 to 100.0 μmol L?1. The limits of detection (LOD) and quantification (LOQ) attained were 0.47 and 4.0 μmol L?1, respectively. The proposed modified electrode was applied to the determination of E1 in pork meat samples. Data provided by the proposed modified electrode were compared with data obtained by UV–vis spectroscopy. The outstanding performance of the electrochemical device indicates that Fe3O4 NP and the IL BMI.PF6 are promising materials for the preparation of chemically modified electrodes for the determination of E1. 相似文献