全文获取类型
收费全文 | 916篇 |
免费 | 28篇 |
国内免费 | 240篇 |
专业分类
化学 | 970篇 |
力学 | 29篇 |
综合类 | 1篇 |
数学 | 27篇 |
物理学 | 157篇 |
出版年
2023年 | 74篇 |
2022年 | 23篇 |
2021年 | 29篇 |
2020年 | 33篇 |
2019年 | 30篇 |
2018年 | 21篇 |
2017年 | 26篇 |
2016年 | 20篇 |
2015年 | 26篇 |
2014年 | 29篇 |
2013年 | 70篇 |
2012年 | 45篇 |
2011年 | 56篇 |
2010年 | 38篇 |
2009年 | 50篇 |
2008年 | 60篇 |
2007年 | 70篇 |
2006年 | 58篇 |
2005年 | 62篇 |
2004年 | 48篇 |
2003年 | 33篇 |
2002年 | 32篇 |
2001年 | 25篇 |
2000年 | 38篇 |
1999年 | 22篇 |
1998年 | 11篇 |
1997年 | 15篇 |
1996年 | 18篇 |
1995年 | 17篇 |
1994年 | 14篇 |
1993年 | 12篇 |
1992年 | 10篇 |
1991年 | 20篇 |
1990年 | 8篇 |
1989年 | 9篇 |
1988年 | 14篇 |
1987年 | 4篇 |
1986年 | 3篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1980年 | 4篇 |
1979年 | 1篇 |
排序方式: 共有1184条查询结果,搜索用时 31 毫秒
1.
Mengjie Liu Te‐Chun Chu Agnes Jocher Mica C. Smith Istvan Lengyel William H. Green 《国际化学动力学杂志》2021,53(1):27-42
Using Reaction Mechanism Generator (RMG), we have automatically constructed a detailed mechanism for acetylene pyrolysis, which predicts formation of polycyclic aromatic hydrocarbons (PAHs) up to pyrene. To improve the data available for formation pathways from naphthalene to pyrene, new high‐pressure limit reaction rate coefficients and species thermochemistry were calculated using a combination of electronic structure data from the literature and new quantum calculations. Pressure‐dependent kinetics for the CH potential energy surface calculated by Zádor et al. were incorporated to ensure accurate pathways for acetylene initiation reactions. After adding these new data into the RMG database, a pressure‐dependent mechanism was generated in a single RMG simulation which captures chemistry from C to C. In general, the RMG‐generated model accurately predicts major species profiles in comparison to plug‐flow reactor data from the literature. The primary shortcoming of the model is that formation of anthracene, phenanthrene, and pyrene are underpredicted, and PAHs beyond pyrene are not captured. Reaction path analysis was performed for the RMG model to identify key pathways. Notable conclusions include the importance of accounting for the acetone impurity in acetylene in accurately predicting formation of odd‐carbon species, the remarkably low contribution of acetylene dimerization to vinylacetylene or diacetylene, and the dominance of the hydrogen abstraction CH addition (HACA) mechanism in the formation pathways to all PAH species in the model. This work demonstrates the improved ability of RMG to model PAH formation, while highlighting the need for more kinetics data for elementary reaction pathways to larger PAHs. 相似文献
2.
《Comptes Rendus Chimie》2015,18(3):345-350
The combination of kinetic and thermodynamic analyses can provide an in-depth knowledge of the crucial steps of catalyzed reactions. Earlier examples are recalled to stress how a reaction mechanism can be supported or rejected based on trivial reactant and product concentration analyses. The method is then applied to the important reaction of alcohol condensation, the so-called Guerbet reaction, which enables converting ethanol, a renewable feedstock, into higher alcohols. Important conclusions regarding the design of ethanol condensation processes can be drawn, as the main reaction mechanism occurring at high temperatures (ca. 350–420 °C) appears to be different from that proposed at low temperatures (< 250 °C). In the former case, the pathway involving acetaldehyde is negligible, and therefore a multi-step process based on ethanol dehydrogenation followed by acetaldehyde self-aldolization would be irrelevant. 相似文献
3.
Solar energy-driven semiconductor photocatalysis has gathered increasing interest in the field of energy and environmental applications. However, a vital problem that limits its application is that photocatalysis requires a continuous light source to perform redox reaction. The ability of keeping catalytic activity in the dark has been the ultimate goal for the wide application of photocatalysis. More and more efforts have been paid to develop photocatalysts to perform photocatalytic reactions under both light and dark conditions, which is so called “round-the-clock photocatalytic system” (RTCPS). RTCPS with an ability of energy storage can work well under both daytime and nighttime, which widely used in the removal of heavy metal ion, the degradation of organic pollutant, disinfection and hydrogen generation. The important potential of RTCPS necessitate timely reviews of the recent advances to streamline efforts. Thus, this review aimed to summarize the recent advances in RTCPS, including the mechanism, characterization techniques and applications. Moreover, future challenge and research direction on the mechanistic study, material design and potential applications are also discussed. 相似文献
4.
Wen Chen Yuan Zhang Prof. Hai-Bo Yi Prof. Fenglin Wang Prof. Xia Chu Prof. Jian-Hui Jiang 《Angewandte Chemie (International ed. in English)》2023,62(17):e202300162
Type I photodynamic therapy (PDT) represents a promising treatment modality for tumors with intrinsic hypoxia. However, type I photosensitizers (PSs), especially ones with near infrared (NIR) absorption, are limited and their efficacy needs improvement via new targeting tactics. We develop a NIR type I PS by engineering acridinium derived donor-π-acceptor systems. The PS exhibits an exclusive type I PDT mechanism due to effective intersystem crossing and disfavored energy transfer to O2, and shows selective binding to G-quadruplexes (G4s) via hydrogen bonds identified by a molecular docking study. Moreover, it enables fluorogenic detection of G4s and efficient O2⋅− production in hypoxic conditions, leading to immunogenic cell death and substantial variations of gene expression in RNA sequencing. Our strategy demonstrates augmented antitumor immunity for effective ablation of immunogenic cold tumor, highlighting its potential of RNA-targeted type I PDT in precision cancer therapy. 相似文献
5.
Dr. Hyun June Choi Elliott L. Bruce Kevin S. Kencana Jingeon Hong Prof. Paul A. Wright Prof. Suk Bong Hong 《Angewandte Chemie (International ed. in English)》2023,62(36):e202305816
An understanding of the CO2 adsorption mechanisms on small-pore zeolites is of practical importance in the development of more efficient adsorbents for the separation of CO2 from N2 or CH4. Here we report that the CO2 isotherms at 25–75 °C on cesium-exchanged phillipsite zeolite with a Si/Al ratio of 2.5 (Cs-PHI-2.5) are characterized by a rectilinear step shape: limited uptake at low CO2 pressure (PCO2) is followed by highly cooperative uptake at a critical pressure, above which adsorption rapidly approaches capacity (2.0 mmol g−1). Structural analysis reveals that this isotherm behavior is attributed to the high concentration and large size of Cs+ ions in dehydrated Cs-PHI-2.5. This results in Cs+ cation crowding and subsequent dispersal at a critical loading of CO2, which allows the PHI framework to relax to its wide pore form and enables its pores to fill with CO2 over a very narrow range of PCO2. Such a highly cooperative phenomenon has not been observed for other zeolites. 相似文献
6.
Michael R. Smith Clare B. Martin Sonia Arumuganainar Ari Gilman Bruce E. Koel Michele L. Sarazen 《Angewandte Chemie (International ed. in English)》2023,62(8):e202218208
Immobilization of porphyrin complexes into crystalline metal–organic frameworks (MOFs) enables high exposure of porphyrin active sites for CO2 electroreduction. Herein, well-dispersed iron-porphyrin-based MOF (PCN-222(Fe)) on carbon-based electrodes revealed optimal turnover frequencies for CO2 electroreduction to CO at 1 wt.% catalyst loading, beyond which the intrinsic catalyst activity declined due to CO2 mass transport limitations. In situ Raman suggested that PCN-222(Fe) maintained its structure under electrochemical bias, permitting mechanistic investigations. These revealed a stepwise electron transfer-proton transfer mechanism for CO2 electroreduction on PCN-222(Fe) electrodes, which followed a shift from a rate-limiting electron transfer to CO2 mass transfer as the potential increased from −0.6 V to −1.0 V vs. RHE. Our results demonstrate how intrinsic catalytic investigations and in situ spectroscopy are needed to elucidate CO2 electroreduction mechanisms on PCN-222(Fe) MOFs. 相似文献
7.
Jindou Tian Prof. Dr. Qihui Chen Prof. Dr. Feilong Jiang Prof. Dr. Daqiang Yuan Prof. Dr. Maochun Hong 《Angewandte Chemie (International ed. in English)》2023,62(7):e202215253
Developing practical storage technologies for acetylene (C2H2) is important but challenging because C2H2 is useful but explosive. Here, a novel metal–organic framework (MOF) ( FJI-H36 ) with adaptive channels was prepared. It can effectively capture C2H2 (159.9 cm3 cm−3) at 1 atm and 298 K, possessing a record-high storage density (561 g L−1) but a very low adsorption enthalpy (28 kJ mol−1) among all the reported MOFs. Structural analyses show that such excellent adsorption performance comes from the synergism of active sites, flexible framework, and matched pores; where the adsorbed-C2H2 can drive FJI-H36 to undergo induced-fit transformations step by step, including deformation/reconstruction of channels, contraction of pores, and transformation of active sites, finally leading to dense packing of C2H2. Moreover, FJI-H36 has excellent chemical stability and recyclability, and can be prepared on a large scale, enabling it as a practical adsorbent for C2H2. This will provide a useful strategy for developing practical and efficient adsorbents for C2H2 storage. 相似文献
8.
Ying Wang Linxiang Cai Hui Li Hanhua Chen Tao Yang Yehong Tan Zijian Guo Xiaoyong Wang 《Angewandte Chemie (International ed. in English)》2023,62(42):e202309043
Drug resistance is a serious challenge for platinum anticancer drugs. Platinum complexes may get over the drug resistance via a distinct mechanism of action. Cholesterol is a key factor contributing to the drug resistance. Inhibiting cellular cholesterol synthesis and uptake provides an alternative strategy for cancer treatment. Platinum(IV) complexes FP and DFP with fenofibric acid as axial ligand(s) were designed to combat the drug resistance through regulating cholesterol metabolism besides damaging DNA. In addition to producing reactive oxygen species and active platinum(II) species to damage DNA, FP and DFP inhibited cellular cholesterol accumulation, promoted cholesterol efflux, upregulated peroxisome proliferator-activated receptor alpha (PPARα), induced caspase-1 activation and gasdermin D (GSDMD) cleavage, thus leading to both apoptosis and pyroptosis in cancer cells. The reduction of cholesterol significantly relieved the drug resistance of cancer cells. The double-acting mechanism gave the complexes strong anticancer activity in vitro and in vivo, particularly against cisplatin-resistant cancer cells. 相似文献
9.
Overview on multicomponent ceramic composite materials used for efficient photocatalysis – An update
《印度化学会志》2023,100(3):100908
Water is an important item for the survival of humans, animals and plants in the planet earth. In the industrialized world, water pollution is raising every day, mainly in the textile, paper, medicine, and plastic production industries. Pollution from coloured compounds is primarily identified as being the major threat to wastewater. In the absence of any pre-treatment, substituted phenols, dyes and agricultural wastes seriously contaminate groundwater systems. For the removal of dyes from the industrial waste water, the following three traditional methods are used: chemical, physical and biological but, the cost of the methods little high. For alternation of these methods, now a days photocatalytic degradation method was used. Metal and metal oxide nanoparticles are excellent catalysts for reducing and degrading aqueous phase nitro compounds and aromatic dyes. Nanoparticles are commonly assembled into two types, i.e., organic (carbon nanoparticles) and inorganic (metal, semiconductor and magnetic nanoparticles) nanoparticles. In this review article we are mainly focused on the behaviour of different types of pure metal oxides and metal oxide@metal/metal oxide/carbon/polymer nanocomposites for the removal of various organic pollutants from water and their efficiency has been reported. As a result of their review the cerium-based metal oxides such as CdS/CeO2, CeO2/Y2O3, GQDs/CeO2 and Ag/cellulose@CeO2/QDs shows more degradation efficiency (above~95%) towards the organic pollutants when compared to other metal oxides. 相似文献
10.
Shengpeng Mo Xinya Zhao Shuangde Li Lili Huang Xin Zhao Quanming Ren Mingyuan Zhang Ruosi Peng Yanan Zhang Xiaobin Zhou Yinming Fan Prof. Qinglin Xie Prof. Yanbing Guo Prof. Daiqi Ye Prof. Yunfa Chen 《Angewandte Chemie (International ed. in English)》2023,62(50):e202313868
Solar-to-chemical energy conversion under weak solar irradiation is generally difficult to meet the heat demand of CO2 reduction. Herein, a new concentrated solar-driven photothermal system coupling a dual-metal single-atom catalyst (DSAC) with adjacent Ni−N4 and Fe−N4 pair sites is designed for boosting gas-solid CO2 reduction with H2O under simulated solar irradiation, even under ambient sunlight. As expected, the (Ni, Fe)−N−C DSAC exhibits a superior photothermal catalytic performance for CO2 reduction to CO (86.16 μmol g−1 h−1), CH4 (135.35 μmol g−1 h−1) and CH3OH (59.81 μmol g−1 h−1), which are equivalent to 1.70-fold, 1.27-fold and 1.23-fold higher than those of the Fe−N−C catalyst, respectively. Based on theoretical simulations, the Fermi level and d-band center of Fe atom is efficiently regulated in non-interacting Ni and Fe dual-atom pair sites with electronic interaction through electron orbital hybridization on (Ni, Fe)−N−C DSAC. Crucially, the distance between adjacent Ni and Fe atoms of the Ni−N−N−Fe configuration means that the additional Ni atom as a new active site contributes to the main *COOH and *HCO3 dissociation to optimize the corresponding energy barriers in the reaction process, leading to specific dual reaction pathways (COOH and HCO3 pathways) for solar-driven photothermal CO2 reduction to initial CO production. 相似文献