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891.
Dr. José I. Urgel Dr. Marco Di Giovannantonio Kristjan Eimre Thorsten G. Lohr Dr. Junzhi Liu Shantanu Mishra Dr. Qiang Sun Amogh Kinikar Dr. Roland Widmer Samuel Stolz Max Bommert Dr. Reinhard Berger Dr. Pascal Ruffieux Dr. Carlo A. Pignedoli Prof. Dr. Klaus Müllen Prof. Dr. Xinliang Feng Prof. Dr. Roman Fasel 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(32):13383-13389
Cumulene compounds are notoriously difficult to prepare and study because their reactivity increases dramatically with the increasing number of consecutive double bonds. In this respect, the emerging field of on-surface synthesis provides exceptional opportunities because it relies on reactions on clean metal substrates under well-controlled ultrahigh-vacuum conditions. Here we report the on-surface synthesis of a polymer linked by cumulene-like bonds on a Au(111) surface via sequential thermally activated dehalogenative C−C coupling of a tribenzoazulene precursor equipped with two dibromomethylene groups. The structure and electronic properties of the resulting polymer with cumulene-like pentagon–pentagon and heptagon–heptagon connections have been investigated by means of scanning probe microscopy and spectroscopy methods and X-ray photoelectron spectroscopy, complemented by density functional theory calculations. Our results provide perspectives for the on-surface synthesis of cumulene-containing compounds, as well as protocols relevant to the stepwise fabrication of carbon–carbon bonds on surfaces. 相似文献
892.
Dr. Chao Wang Min Hu Dr. Yueying Chu Xue Zhou Dr. Qiang Wang Dr. Guodong Qi Dr. Shenhui Li Prof. Dr. Jun Xu Prof. Dr. Feng Deng 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(18):7265-7269
The understanding of catalyst deactivation represents one of the major challenges for the methanol-to-hydrocarbon (MTH) reaction over acidic zeolites. Here we report the critical role of intermolecular π-interactions in catalyst deactivation in the MTH reaction on zeolites H-SSZ-13 and H-ZSM-5. π-interaction-induced spatial proximities between cyclopentenyl cations and aromatics in the confined channels and/or cages of zeolites are revealed by two-dimensional solid-state NMR spectroscopy. The formation of naphtalene as a precursor to coke species is favored due to the reaction of aromatics with the nearby cyclopentenyl cations and correlates with both acid density and zeolite topology. 相似文献
893.
Meng Zhao Dr. Hong-Jie Peng Bo-Quan Li Dr. Xiao Chen Jin Xie Dr. Xinyan Liu Prof. Qiang Zhang Prof. Jia-Qi Huang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(23):9096-9102
In situ evolution of electrocatalysts is of paramount importance in defining catalytic reactions. Catalysts for aprotic electrochemistry such as lithium–sulfur (Li-S) batteries are the cornerstone to enhance intrinsically sluggish reaction kinetics but the true active phases are often controversial. Herein, we reveal the electrochemical phase evolution of metal-based pre-catalysts (Co4N) in working Li-S batteries that renders highly active electrocatalysts (CoSx). Electrochemical cycling induces the transformation from single-crystalline Co4N to polycrystalline CoSx that are rich in active sites. This transformation propels all-phase polysulfide-involving reactions. Consequently, Co4N enables stable operation of high-rate (10 C, 16.7 mA cm−2) and electrolyte-starved (4.7 μL mgS−1) Li-S batteries. The general concept of electrochemically induced sulfurization is verified by thermodynamic energetics for most of low-valence metal compounds. 相似文献
894.
Prof. Dr. Su-Yun Zhang Dr. Han Miao Dr. He-min Zhang Jun-Hao Zhou Prof. Dr. Qiang Zhuang Prof. Dr. Yu-Jia Zeng Prof. Dr. Zhiming Gao Prof. Dr. Jiayin Yuan Prof. Dr. Jian-Ke Sun 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(49):22293-22300
The capability to significantly shorten the synthetic period of a broad spectrum of open organic materials presents an enticing prospect for materials processing and applications. Herein we discovered 1,2,4-triazolium poly(ionic liquid)s (PILs) could serve as a universal additive to accelerate by at least one order of magnitude the growth rate of representative imine-linked crystalline open organics, including organic cages, covalent organic frameworks (COFs), and macrocycles. This phenomenon results from the active C5-protons in poly(1,2,4-triazolium)s that catalyze the formation of imine bonds, and the simultaneous salting-out effect (induced precipitation by decreasing solubility) that PILs exert on these crystallizing species. 相似文献
895.
Meiling Chen Chenxi Peng Yaoquan Su Xue Chen Prof. Yuezhou Zhang Prof. Yu Wang Prof. Juanjuan Peng Dr. Qiang Sun Prof. Xiaowang Liu Prof. Wei Huang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(47):21174-21181
The ability to incorporate functional metal ions (Mn+) into metal–organic coordination complexes adds remarkable flexibility in the synthesis of multifunctional organic–inorganic hybrid materials with tailorable electronic, optical, and magnetic properties. We report the cation-exchanged synthesis of a diverse range of hollow Mn+-phytate (PA) micropolyhedra via the use of hollow Co2+-PA polyhedral networks as templates at room temperature. The attributes of the incoming Mn+, namely Lewis acidity and ionic radius, control the exchange of the parent Co2+ ions and the degree of morphological deformation of the resulting hollow micropolyhedra. New functions can be obtained for both completely and partially exchanged products, as supported by the observation of Ln3+ (Ln3+=Tb3+, Eu3+, and Sm3+) luminescence from as-prepared hollow Ln3+-PA micropolyhedra after surface modification with dipicolinic acid as an antenna. Moreover, Fe3+- and Mn2+-PA polyhedral complexes were employed as magnetic contrast agents. 相似文献
896.
采用来源于可再生资源的聚醚酰胺弹性体(PEBA)增韧聚乳酸(PLA)制备超韧聚乳酸(PLA/PEBA-GMA)复合材料.为了提高PEBA与PLA之间的相容性,选择极性单体甲基丙烯酸缩水甘油酯(GMA)、共接枝单体乙烯基吡咯烷酮(NVP)及引发剂过氧化二异丙苯(DCP)对PEBA进行接枝改性制备PEBA-GMA.研究了接枝单体组分的用量(m/g)对PLA/PEBA-GMA复合材料性能的影响.研究发现,随着接枝单体组分用量的提高,复合材料的缺口冲击强度逐渐增大,当接枝单体组分GMA,NVP和DCP的用量分别为2.5,2.5和0.25 g时,复合材料的冲击强度高达88.6 kJ/m2,断裂伸长率为164.1%.研究表明,在熔融共混过程中,聚乳酸的端基(—OH和—COOH)与PEBA-GMA上环氧基团发生反应,有效改善两相间的界面相容性,随着接枝单体组分比例的提高,分散相PEBA-GMA的粒子尺寸逐渐减小且分布均匀. 相似文献
897.
898.
采用失重法、电化学法、X射线光电子能谱(XPS)和扫描电子显微镜(SEM)研究了0.5 mol/L NaCl溶液中,山梨酸钾(PS)与Zn2+对Q235钢的缓蚀协同效应。 失重实验结果表明,在0.5 mol/L NaCl溶液中,PS对Q235钢具有一定的缓蚀效果,缓蚀效率随PS质量浓度的增加而增大,当添加PS的质量浓度为25.0 g/L时,最大缓蚀效率仅为38.37%,而PS与Zn2+复配后存在显著的缓蚀协同作用,缓蚀效率高达91.03%。 动电势极化结果表明,PS与Zn2+混合物可同时抑制Q235钢的阴、阳极反应,属于阳极型缓蚀剂。 阻抗谱表明,该混合物可在电极表面形成致密的保护膜。 XPS分析证明保护膜是由PS、铁的氧化物/氢氧化物和Zn(OH)2沉淀组成。 相似文献
899.
壬基环己醇聚氧乙烯醚(NCEOn)是非环境友好型壬基酚聚氧乙烯醚(NPEOn)潜在的升级换代产品。 本文采用正相高效液相色谱法(NP HPLC)测定产品中残存壬基环己醇(NC),用Weilbull法测定其中聚乙二醇(PEG)含量,用电喷雾电离质谱法评价聚氧乙烯(PEO)多分散指数(PDI),以此鉴定NCEOn的品质。 为了建立快速分析NCEOn产品中NC含量的方法,以满足跟踪检测的需求,本文筛选了反相HPLC和NP HPLC两类5种方法,并进行比较和初步条件优化,确定了用Inertsil NH2色谱柱和示差折光检测器以及乙酸乙酯为洗脱液的NP HPLC法定量分析NC,方法的回收率为91.77%~107.6%,相对标准偏差为4.46%,最低检测限为9.8 μg/mL。 经测定,NCEO7和NCEO9产品中NC的残留量分别为0.158%和0.139%,PEG质量分数为7.1%和7.3%,PDI为85.0%和88.6%,证实NCEOn产品具有NC残留量少、PEG含量低和产品PEO窄分布特征,具有在化妆品或个人洗护用品等民用产品中替代NPEOn的潜能。 相似文献
900.
Yanyan Qin Pengfei She Song Guo Xiaomeng Huang Shujuan Liu Qiang Zhao Wei Huang 《物理化学学报》2020,36(1):1907078-0
力致发光是一种力刺激诱导的发光现象。由于其独特的发光方式,使得力致发光材料在结构损伤检测、压力传感、显示和安全标记等方面展现出了巨大的应用价值。目前已报道的力致发光材料大多基于无机材料体系,而有机力致发光材料体系相对较少,并且人们对其发光机理的认识仍不清晰。在本文中,我们发现锰(Ⅱ)配合物[BPP]2[Mn Br4]具有力致发光特性,并在此基础上设计合成了一系列具有力致发光性质的四卤化锰(Ⅱ)配合物。改变有机阳离子配体或者卤素阴离子可对其光物理性质进行有效调控。固态下,这些锰(Ⅱ)配合物均显示出了较强的光致发光现象,同时表现出了明显的力致发光特性。晶体结构分析表明,分子内/分子间强的C―H…X (X=Br或Cl)相互作用对锰(Ⅱ)配合物的力致发光起到了至关重要的作用,它可在较大程度上降低由分子振动和旋转造成的能量损失。本工作将为力刺激响应型材料体系的拓展提供一定的参考价值。 相似文献