全文获取类型
收费全文 | 23688篇 |
免费 | 1104篇 |
国内免费 | 837篇 |
专业分类
化学 | 13601篇 |
晶体学 | 163篇 |
力学 | 1780篇 |
综合类 | 41篇 |
数学 | 3301篇 |
物理学 | 6743篇 |
出版年
2021年 | 358篇 |
2020年 | 450篇 |
2019年 | 500篇 |
2018年 | 553篇 |
2017年 | 496篇 |
2016年 | 758篇 |
2015年 | 464篇 |
2014年 | 665篇 |
2013年 | 944篇 |
2012年 | 1032篇 |
2011年 | 1033篇 |
2010年 | 883篇 |
2009年 | 851篇 |
2008年 | 869篇 |
2007年 | 833篇 |
2006年 | 703篇 |
2005年 | 614篇 |
2004年 | 576篇 |
2003年 | 590篇 |
2002年 | 624篇 |
2001年 | 563篇 |
2000年 | 427篇 |
1999年 | 361篇 |
1998年 | 310篇 |
1997年 | 300篇 |
1996年 | 285篇 |
1995年 | 270篇 |
1993年 | 277篇 |
1992年 | 263篇 |
1991年 | 282篇 |
1990年 | 298篇 |
1989年 | 284篇 |
1985年 | 288篇 |
1984年 | 287篇 |
1983年 | 267篇 |
1982年 | 280篇 |
1980年 | 255篇 |
1979年 | 299篇 |
1978年 | 329篇 |
1977年 | 320篇 |
1976年 | 403篇 |
1975年 | 358篇 |
1974年 | 390篇 |
1973年 | 396篇 |
1972年 | 368篇 |
1971年 | 332篇 |
1970年 | 315篇 |
1969年 | 299篇 |
1968年 | 254篇 |
1967年 | 251篇 |
排序方式: 共有10000条查询结果,搜索用时 382 毫秒
981.
Tunable and Specific Formation of C@NiCoP Peapods with Enhanced HER Activity and Lithium Storage Performance 下载免费PDF全文
Yuanjuan Bai Dr. Huijuan Zhang Li Liu Haitao Xu Prof. Dr. Yu Wang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(3):1021-1029
The superior properties of nanomaterials with a special structure can provide prospects for highly efficient water splitting and lithium storage. Herein, we fabricated a series of peapodlike C@Ni2?xCoxP (x≤1) nanocomposites by an anion‐exchange pathway. The experimental results indicated that the HER activity of C@Ni2?xCoxP catalyst is strongly related to the Co/Ni ratio, and the C@NiCoP got the highest HER activity with low onset potential of ~45 mV, small Tafel slope of ~43 mV dec?1, large exchange current density of 0.21 mA cm?2, and high long‐term durability (60 h) in 0.5 m H2SO4 solutions. Equally importantly, as an anode electrode for lithium batteries, this peapodlike C@NiCoP nanocomposite gives excellent charge–discharge properties (e.g., specific capacity of 670 mAh g?1 at 0.2 A g?1 after 350 cycles, and a reversible capacity of 405 mAh g?1 at a high current rate of 10 A g?1). The outstanding performance of C@NiCoP in HER and LIBs could be attributed to the synergistic effect of the rational design of peapodlike nanostructures and the introduction of Co element. 相似文献
982.
983.
984.
985.
Asymmetric Michael Addition of Aldimino Esters with Chalcones Catalyzed by Silver/Xing‐Phos: Mechanism‐Oriented Divergent Synthesis of Chiral Pyrrolines 下载免费PDF全文
Xing‐Feng Bai Dr. Li Li Dr. Zheng Xu Dr. Zhan‐Jiang Zheng Prof. Dr. Chun‐Gu Xia Dr. Yu‐Ming Cui Prof. Dr. Li‐Wen Xu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(30):10399-10404
The mechanism‐oriented reaction design for the divergent synthesis of chiral molecules from simple starting materials is highly desirable. In this work, aromatic amide‐derived nonbiarylatropisomer/silver (silver/Xing‐Phos) complex was used to catalyze the Michael addition of glycine aldimino esters to chalcones and successfully applied to the subsequent cyclocondensation to afford substituted cis‐Δ(1)‐pyrroline derivatives with up to 98 % ee. Besides the inherent performance of the chiral Ag/Xing‐Phos catalyst system, it was found that the workup of such reactions played an important role for the stereoselective construction of stereodivergent Δ(1)‐pyrrolines, in which an epimerization of the cis‐Δ(1)‐pyrrolines to the trans‐isomers during was revealed. 相似文献
986.
A Phosphorescent Platinum(II) Bipyridyl Supramolecular Polymer Based on Quadruple Hydrogen Bonds 下载免费PDF全文
Fang‐Wei Liu Dr. Li‐Ya Niu Prof. Yong Chen Prof. Vaidhyanathan Ramamurthy Prof. Li‐Zhu Wu Prof. Chen‐Ho Tung Prof. Yu‐Zhe Chen Prof. Qing‐Zheng Yang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(50):18132-18139
A platinum(II) bipyridyl complex bearing bis‐ureidopyrimidinone (Pt‐bisUPy) has been designed and its self‐assembling behavior has been thoroughly investigated by 1H NMR, DOSY NMR, Ubbelohde viscometry analysis, UV/Vis, and emission spectroscopies. Pt‐bisUPy underwent concentration‐dependent ring‐chain polymerization in apolar solvents. Hydrogen‐bonding interactions play an important role during the formation of the supramolecular polymers. Hydrogen‐bonded supramolecular polymers were transformed to nanoparticles in water through the miniemulsion method. These nanoparticles showed strong π–π excimeric emission. Metal‐metal‐to‐ligand charge transfer (MMLCT) from Pt–Pt interactions was not significant in the emission spectrum. The phosphorescence of the nanoparticle persisted even under aerobic conditions. The triplet state of these phosphorescent nanomaterials were long‐lived and possessed moderate emission quantum yields. Furthermore, the low toxicity of these materials promises a place for them in in vitro and in vivo bioimaging. 相似文献
987.
988.
989.
A series of imidazolium chlorides for the formation of tridentate CNO‐donor palladium(II) complexes featuring N‐heterocyclic carbene moieties have been developed from cheap and readily available starting materials with high yields. Their palladium complexes were prepared by reactions between the ligand precursors and PdCl2 using K2CO3 as base in pyridine with reasonable yields. These air‐stable metal complexes were characterized using 1H NMR and 13C{1H} NMR spectroscopy and elemental analyses. Heteronuclear multiple bond correlation experiments were performed to identify key NMR signals of these compounds. The structures of two of the complexes were also established by single‐crystal X‐ray diffraction analysis. One of these complexes was successfully applied in the direct C―H functionalization reactions between heterocyclic compounds and aryl bromides, producing excellent yields of coupled products. The coupling reactions were scalable, allowing grams of coupled products to be obtained with a mere 2 mol% of Pd loading. The catalyst system developed allowed the large‐scale preparation of several push–pull chromophores straightforwardly. Photophysical properties based on UV–visible and fluorescence spectroscopy for these chromophores were investigated. Deep blue photoluminescence with moderate quantum efficiency and twisted intramolecular charge transfer excited state were observed for these chromophores. Density functional theory (DFT) and time‐dependent DFT calculations were performed to support the experimental results. 相似文献
990.
In this paper, we are concerned with the behavior of shock waves in a 2 × 2 balance law with discontinuous source terms. We obtain the existence of a local shock wave solution of this problem and deduce that the discontinuous source terms create a weak discontinuity in this solution. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献