全文获取类型
收费全文 | 1209篇 |
免费 | 168篇 |
国内免费 | 128篇 |
专业分类
化学 | 833篇 |
晶体学 | 13篇 |
力学 | 82篇 |
综合类 | 10篇 |
数学 | 162篇 |
物理学 | 405篇 |
出版年
2024年 | 3篇 |
2023年 | 33篇 |
2022年 | 33篇 |
2021年 | 53篇 |
2020年 | 74篇 |
2019年 | 56篇 |
2018年 | 49篇 |
2017年 | 56篇 |
2016年 | 54篇 |
2015年 | 47篇 |
2014年 | 76篇 |
2013年 | 97篇 |
2012年 | 112篇 |
2011年 | 107篇 |
2010年 | 69篇 |
2009年 | 58篇 |
2008年 | 65篇 |
2007年 | 70篇 |
2006年 | 64篇 |
2005年 | 55篇 |
2004年 | 24篇 |
2003年 | 30篇 |
2002年 | 20篇 |
2001年 | 27篇 |
2000年 | 25篇 |
1999年 | 21篇 |
1998年 | 11篇 |
1997年 | 11篇 |
1996年 | 21篇 |
1995年 | 8篇 |
1994年 | 16篇 |
1993年 | 7篇 |
1992年 | 16篇 |
1991年 | 9篇 |
1990年 | 3篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1987年 | 6篇 |
1986年 | 7篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1970年 | 1篇 |
1965年 | 1篇 |
1958年 | 1篇 |
排序方式: 共有1505条查询结果,搜索用时 15 毫秒
1.
Huo Guang-Hua Cui Chao-Yu He Tian Yan Jun-Qing Peng Wen-Wen 《Chemistry of Natural Compounds》2022,58(3):468-470
Chemistry of Natural Compounds - A new carotane sesquiterpenoid, methyl gymnabloate (1), was isolated from the fermentation broth of the wild macrofungus Gymnopus sp. 0612-9. Its structure was... 相似文献
2.
Mahdi Faghih Zheng Chen Jialong Huo Zhuyin Ren Chung K. Law 《Proceedings of the Combustion Institute》2019,37(2):1505-1512
The outwardly propagating spherical flame (OPF) method is popularly used to measure the laminar flame speed (LFS). Recently, great efforts have been devoted to improving the accuracy of the LFS measurement from OPF. In the OPF method, several assumptions are made. For examples, the burned gas is assumed to be static and in chemical equilibrium. However, these assumptions may not be satisfied under certain conditions. Here we consider low-pressure and super-adiabatic propagating spherical flames, for which chemical non-equilibrium exists and the burned gas may not be static. The objective is to assess the chemical non-equilibrium effects on the accuracy of LFS measurement from the OPF method. Numerical simulations considering detailed chemistry and transport are conducted. Stoichiometric methane/air flames at sub-atmospheric pressures and methane/oxygen flames at different equivalence ratios are considered. At low pressures, broad heat release zone is observed and the burned gas cannot quickly reach the adiabatic flame temperature, indicating the existence of chemical non-equilibrium of burned gas. Positive flow in the burned gas is identified and it is shown to become stronger at lower initial pressure. Consequently, the LFS measurement from OPF at low pressures is not accurate if the burned gas is assumed to be static and at chemical equilibrium. For super-adiabatic spherical flames, the burned gas speed is found to be negative due to the local temperature overshoot at the flame front. Such negative speed of burned gas can also reduce the accuracy of LFS measurement. It is recommended that the direct method measuring both flame propagation speed and flow speed of unburned gas should be used to determine the LFS at low pressures or for mixtures with super-adiabatic flame temperature. 相似文献
3.
4.
Dr. Peng Wang Dr. Chang-xin Huo Shuyao Lang Dr. Kyle Caution Dr. Setare Tahmasebi Nick Prof. Purnima Dubey Prof. Rajendar Deora Prof. Xuefei Huang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(16):6513-6520
With the infection rate of Bordetella pertussis at a 60-year high, there is an urgent need for new anti-pertussis vaccines. The lipopolysaccharide (LPS) of B. pertussis is an attractive antigen for vaccine development. With the presence of multiple rare sugars and unusual glycosyl linkages, the B. pertussis LPS is a highly challenging synthetic target. In this work, aided by molecular dynamics simulation and modeling, a pertussis-LPS-like pentasaccharide was chemically synthesized for the first time. The pentasaccharide was conjugated with a powerful carrier, bacteriophage Qβ, as a vaccine candidate. Immunization of mice with the conjugate induced robust anti-glycan IgG responses with IgG titers reaching several million enzyme-linked immunosorbent assay (ELISA) units. The antibodies generated were long lasting and boostable and could recognize multiple clinical strains of B. pertussis, highlighting the potential of Qβ-glycan as a new anti-pertussis vaccine. 相似文献
5.
We are interested in the classical solutions to the Cauchy problem of relativistic Burgers equations evolving in Friedmann-Lemat?tre-Robertson-Walker(FLRW)space-times,which are spatially homogeneous,isotropic expanding or contracting universes.In such kind of space-times,we first derive the relativistic Burgers equations from the relativistic Euler equations by letting the pressure be zero.Then we can show the global existence of the classical solution to the derived equation in the accelerated expanding space-times with small initial data by the method of characteristics when the spacial dimension n=1 and the energy estimate when n 2,respectively.Furthermore,we can also show the lifespan of the classical solution by similar methods when the expansion rate of the space-times is not so fast. 相似文献
6.
Alkynes cycloaddition reactions are powerful tools for constructing cyclic molecules with optimal atom efficiency, but these reactions cannot proceed at ambient temperature without transition-metal catalysts. In this work, a heterobimetallic complex featuring an Nb–Fe triple bond, Nb(iPrNPMe2)3Fe–PMe3, has been evaluated as the potential catalyst for acetylene cycloaddition, using density functional theory. The calculated results show that the singlet-state (i.e. ground-state) Nb(iPrNPMe2)3Fe–PMe3 can be applied to benzene synthesis, but is not suitable for cyclobutadiene. Benzene can be obtained easily at room temperature and is the unique product on the singlet potential surface. The irradiation of infrared-red light can drive the excitation of singlet Nb(iPrNPMe2)3Fe–PMe3 to its triplet state. Both benzene and cyclobutadiene can be formed on the triplet reaction potential surface due to their low energy barriers. Therefore, Nb(iPrNPMe2)3Fe–PMe3 is a potential high reactivity heterobimetallic catalyst for the cyclotrimerization of alkynes. In the reaction process, the catalytic active site of Nb(iPrNPMe2)3Fe–PMe3 moves from niobium to iron. 相似文献
7.
绝缘子表面粗糙处理是提升其沿面闪络性能的重要途径,表面粗糙化处理方式不当,极易带来表面结构不均匀,难以获得稳定耐压性能的绝缘材料。为提升绝缘子表面粗糙处理的均匀性,本文利用表面喷砂技术对圆柱形有机玻璃(PMMA)绝缘子进行了粗糙化处理研究,以球形二氧化硅(SiO2)颗粒为工作介质,研究了不同喷砂粒径、氢氟酸后处理等因素对绝缘材料表面形貌和组分的影响,并利用短脉冲高压测试平台对喷砂处理前后有机玻璃绝缘子样品进行了真空沿面闪络性能测试。研究结果表明,喷砂处理在有机玻璃表面形成了较为均匀的凹坑,HF酸能够有效去除表面残留的SiO2颗粒,具有表面喷砂粗糙结构的绝缘子沿面闪络电压得到了稳定提升,相较于未处理的绝缘子闪络电压提升了约80%。 相似文献
8.
Lithium-sulfur batteries (LSBs) with high energy density and low cost have been recognized as one of the most promising next-generation energy storage systems. Although it has taken decades of development, the practical application of LSBs has been hindered by several inherent obstacles, particularly the severe shuttle effect and sluggish reaction kinetics in the sulfur cathode. Various strategies have been proposed to address these problems via rational design of electrode materials and configurations. Freestanding sulfur cathode could be a promising strategy to improve the sulfur mass loading at the cathode level and energy density of LSBs. This minireview will briefly summary the recent advances in freestanding cathodes for LSBs. The advantages and disadvantages of various freestanding cathodes are discussed and the prospects for the development of flexible cathodes are envisioned. 相似文献
9.
Dr. Subrat Kumar Barik Shou-Chih Huo Chun-Yen Wu Tzu-Hao Chiu Jian-Hong Liao Dr. Xiaoping Wang Dr. Samia Kahlal Prof. Jean-Yves Saillard Prof. C. W. Liu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(46):10471-10479
Although atomically precise polyhydrido copper nanoclusters are of prime interest for a variety of applications, they have so far remained scarce. Herein, this work describes the synthesis of a dithiophosphate-protected copper(I) hydride-rich nanocluster (NC), [Cu30H18{S2P(OnPr)2}12] ( 1H ), fully characterized by various spectroscopic methods and single-crystal X-ray diffraction. The X-ray structure of 1H reveals an unprecedented central Cu12 hollow icosahedron. Six faces of this icosahedron are capped by Cu3 triangles, the whole Cu30 core being wrapped by twelve dithiophosphate ligands and the whole cluster has ideal S6 symmetry. The locations of the 18 hydrides in 1H were ascertained by a single-crystal neutron diffraction study. They are composed of three types: capping μ3-H, interstitial μ4-H (seesaw) and μ5-H ligands (square pyramidal), in good agreement with the DFT simulations. The numbers of hydrides and ligand resonances in the 1H NMR spectrum of 1H are in line with their coordination environment in the solid state, retaining the S6 symmetry in solution. Furthermore, two new Se-protected polyhydrido copper nanoclusters, [Cu30H18{Se2P(OR)2}12] ( 2H : R=iPr 3H : R=iBu) were synthesized from their sulfur relative 1H via ligand displacement reaction and their X-ray structures feature the exceptional case where both the NC shape and size are fully conserved during the course of ligand exchange. DFT and TD-DFT calculations allow understanding the bonding and optical properties of clusters 1H – 3H . In addition, the reaction of 1H with [Pd(PPh3)2Cl2] in the presence of terminal alkynes led to the formation of new bimetallic Cu−Pd alloy clusters [PdCu14H2{S2P(OnPr)2}6(C≡CR)6] ( 4 : R=Ph; 5 : R = C6H4F). 相似文献
10.
Dr. Zafar Mahmood Noreen Rehmat Prof. Shaomin Ji Prof. Jianzhang Zhao Shanshan Sun Dr. Mariangela Di Donato Prof. Mingde Li Maria Teddei Prof. Yanping Huo 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(65):14912-14918
Zinc(II) bis(dipyrrin) complexes, which feature intense visible absorption and efficient symmetry breaking charge transfer (SBCT) are outstanding candidates for photovoltaics but their short lived triplet states limit applications in several areas. Herein we demonstrate that triplet excited state dynamics of bis(dipyrrin) complexes can be efficiently tuned by attaching electron donating aryl moieties at the 5,5′-position of the complexes. For the first time, a long lived triplet excited state (τT=296 μs) along with efficient ISC ability (ΦΔ=71 %) was observed for zinc(II) bis(dipyrrin) complexes, formed via SBCT. The results revealed that molecular geometry and energy gap between the charge transfer (CT) state and triplet energy levels strongly control the triplet excited state properties of the complexes. An efficient triplet–triplet annihilation upconversion system was devised for the first time using a SBCT architecture as triplet photosensitizer, reaching a high upconversion quantum yield of 6.2 %. Our findings provide a blueprint for the development of triplet photosensitizers based on earth abundant metal complexes with long lived triplet state for revolutionary photochemical applications. 相似文献