全文获取类型
收费全文 | 6288篇 |
免费 | 1182篇 |
国内免费 | 699篇 |
专业分类
化学 | 4219篇 |
晶体学 | 91篇 |
力学 | 409篇 |
综合类 | 83篇 |
数学 | 742篇 |
物理学 | 2625篇 |
出版年
2024年 | 27篇 |
2023年 | 146篇 |
2022年 | 271篇 |
2021年 | 290篇 |
2020年 | 327篇 |
2019年 | 280篇 |
2018年 | 276篇 |
2017年 | 231篇 |
2016年 | 353篇 |
2015年 | 351篇 |
2014年 | 426篇 |
2013年 | 538篇 |
2012年 | 582篇 |
2011年 | 532篇 |
2010年 | 422篇 |
2009年 | 322篇 |
2008年 | 394篇 |
2007年 | 384篇 |
2006年 | 292篇 |
2005年 | 242篇 |
2004年 | 161篇 |
2003年 | 152篇 |
2002年 | 149篇 |
2001年 | 140篇 |
2000年 | 126篇 |
1999年 | 151篇 |
1998年 | 94篇 |
1997年 | 95篇 |
1996年 | 76篇 |
1995年 | 69篇 |
1994年 | 54篇 |
1993年 | 53篇 |
1992年 | 38篇 |
1991年 | 33篇 |
1990年 | 26篇 |
1989年 | 14篇 |
1988年 | 9篇 |
1987年 | 6篇 |
1986年 | 14篇 |
1985年 | 7篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1981年 | 4篇 |
1979年 | 1篇 |
1957年 | 3篇 |
排序方式: 共有8169条查询结果,搜索用时 0 毫秒
101.
Qi Xiong Dr. Gang Huang Prof. Xin-Bo Zhang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(43):19473-19481
Li-O2 batteries with ultrahigh theoretical energy densities usually suffer from low practical discharge capacities and inferior cycling stability owing to the cathode passivation caused by insulating discharge products and by-products. Here, a trifunctional ether-based redox mediator, 2,5-di-tert-butyl-1,4-dimethoxybenzene (DBDMB), is introduced into the electrolyte to capture reactive O2− and alleviate the rigorous oxidative environment of Li-O2 batteries. Thanks to the strong solvation effect of DBDMB towards Li+ and O2−, it not only reduces the formation of by-products (a high Li2O2 yield of 96.6 %), but also promotes the solution growth of large-sized Li2O2 particles, avoiding the passivation of cathode as well as enabling a large discharge capacity. Moreover, DBDMB makes the oxidization of Li2O2 and the decomposition of main by-products (Li2CO3 and LiOH) proceed in a highly effective manner, prolonging the stability of Li-O2 batteries (243 cycles at 1000 mAh g−1 and 1000 mA g−1). 相似文献
102.
A clean and safe synthesis method of 5-(4’-methylbiphenyl-2-yl)-1H-tetrazole was found:under hydrothermal conditions,1.2 equiv.of 4’-methylbiphenyl-2-carbonitrile react with 1 equiv.of sodium azide in a mixed solvent of propane-1,2-diol/H2O,with 1.5 equiv.of ammonium chloride and 0.2 equiv.of ammonium fluoride as catalyst.After simple post-processing,the yield can be improved to 95%,and the purity of the product is 99%without further recrystallization. 相似文献
103.
A facile one-pot method to high-quality Ag-graphene composite nanosheets for efficient surface-enhanced Raman scattering 总被引:2,自引:0,他引:2
Zhang Z Xu F Yang W Guo M Wang X Zhang B Tang J 《Chemical communications (Cambridge, England)》2011,47(22):6440-6442
Ag-graphene composite nanosheets (AGCN) with adjustable size and well-controlled densities of Ag nanoparticles (Ag NPs) using Poly(N-vinyl-2-pyrrolidone) (PVP) as a reductant and stabilizer are reported. The obtained AGCN substrate is extremely suitable for surface-enhanced Raman spectroscopy (SERS). 相似文献
104.
Methanol (MeOH) oxidation reaction (MOR) at Pt electrodes under potentiostatic conditions has been investigated by electrochemical in situ FTIR spectroscopy (FTIRS) in attenuated-total-reflection configuration under controlled flow conditions in 0.1 M HClO(4) with 2 M MeOH, where the mass transport effects are largely eliminated using a flow cell. Our results reveal that (i) at constant potentials, the methanol dehydrogenation rate decreases while the CO(ad) oxidation rate increases with the accumulation of CO(ad) until the maximum CO(ad) coverage (ca. 0.5 ML i.e., the steady state) is reached; (ii) at fixed CO(ad) coverage, the rates for MeOH decomposition to CO(ad) and CO(ad) oxidation increases with potential from 0.3 to 0.7 V (vs. RHE), with Tafel slopes for MeOH dehydrogenation of ca. 440 ± 30 mV/dec, which is independent of CO(ad) coverage; (iii) the current efficiency of the CO pathway in MOR at 0.6 and 0.7 V is below 20% and it decreases toward higher potentials. The mechanisms as well as the potential induced change in the kinetics of different pathways involved in MOR are briefly discussed. 相似文献
105.
106.
A family of modified two-derivative Runge–Kutta (MTDRK) methods for the integration of the Schrödinger equation are obtained. Two new three-stage and fifth order TDRK methods are derived. The numerical results in the integration of the radial Schrödinger equation with the Woods–Saxon potential are reported to show the high efficiency of our new methods. The results of the error analysis are illustrated by the resonance problem. 相似文献
107.
Terminal alkynes 1 react with Cp2Zr(H)Cl (Cp = η5-C5H5) and CO to give acylzirconocene chloride derivatives 2, which are trapped with arylsulfenyl chlorides to afford (E)-α,β-unsaturated thioesters. 相似文献
108.
Experimental Evidence for a Triboluminescent Antiperovskite Ferroelectric: Tris(trimethylammonium) catena‐Tri‐μ‐chloro‐manganate(II) Tetrachloromanganate(II) 下载免费PDF全文
Dr. Peng‐Fei Li Dr. Yuan‐Yuan Tang Dr. Wei‐Qiang Liao Dr. Ping‐Ping Shi Dr. Xiu‐Ni Hua Dr. Yi Zhang Dr. Zhenhong Wei Dr. Hu Cai Prof. Ren‐Gen Xiong 《Angewandte Chemie (International ed. in English)》2018,57(37):11939-11942
The perovskite structure is rich in ferroelectricity. In contrast, ferroelectric antiperovskites have been scarcely confirmed experimentally since the discovery of M3AB‐type antiperovskites in the 1930s. Ferroelectricity is now revealed in an organic–inorganic hybrid X3AB antiperovskite structure, which exhibits a clear ferroelectric phase transition 6/mmmF6mm with a high Curie point of 480 K. The physical properties across the phase transition are obviously changed along with the symmetry requirements, providing solid experimental evidence for the ferroelectric phase transition. More interestingly, the discovered antiperovskite shows intense photoluminescence and triboluminescence properties. The confirmation of the triboluminescent ferroelectric antiperovskite will open new avenues to explore excellent optoelectronic properties in the antiperovskite family. 相似文献
109.
Muyi He You Jiang Dan Guo Xingchuang Xiong Xiang Fang Wei Xu 《Journal of the American Society for Mass Spectrometry》2017,28(7):1262-1270
A dual-polarity linear ion trap (LIT) mass spectrometer was developed in this study, and the method for simultaneously controlling and detecting cations and anions was proposed and realized in the LIT. With the application of an additional dipolar DC field on the ejection electrodes of an LIT, dual-polarity mass spectra could be obtained, which include both the mass-to-charge (m/z) ratio and charge polarity information of an ion. Compared with conventional method, the ion ejection and detection efficiency could also be improved by about one-fold. Furthermore, ion–ion reactions within the LIT could be dynamically controlled and monitored by manipulating the distributions of ions with opposite charge polarities. This method was then used to control and study the reaction kinetics of ion–ion reactions, including electron transfer dissociation (ETD) and charge inversion reactions. A dual-polarity collision-induced dissociation (CID) experiment was proposed and performed to enhance the sequence coverage of a peptide ion. Ion trajectory simulations were also carried out for concept validation and system optimization. 相似文献
110.
An amperometric sensor for the determination of indole-3-acetic acid (IAA) based on the CeCl3-DHP film modified gold electrode was developed. CeCl3 was dissolved into water in the presence of dihexadecyl hydrogen phosphate (DHP). The IAA sensor was prepared via evaporating
solvent of the CeCl3-DHP dispersion on the gold electrode surface. The amperometric response of IAA on the CeCl3-DHP film modified gold electrode was investigated. The experimental results indicate that the passivation of the electrode
due to the adsorption of the oxidation product of IAA decreases significantly at the CeCl3-DHP film modified gold electrode, in contrast to that at the bare and the DHP modified gold electrode. The experimental parameters
were optimized and an electrochemical method for the determination of IAA was established. The oxidation peak current is linearly
with the concentration of IAA from 1 × 10−7 to 2 × 10−5 mol l−1 and the detection limit is 3 × 10−8 mol l−1. The relative standard deviation of eight measurements is 3.2% for 5 × 10−7 mol l−1 IAA. The IAA in plant leaves were extracted and determined by the IAA sensor. 相似文献