全文获取类型
收费全文 | 1315篇 |
免费 | 225篇 |
国内免费 | 101篇 |
专业分类
化学 | 419篇 |
晶体学 | 1篇 |
力学 | 65篇 |
综合类 | 40篇 |
数学 | 907篇 |
物理学 | 209篇 |
出版年
2024年 | 1篇 |
2023年 | 38篇 |
2022年 | 94篇 |
2021年 | 80篇 |
2020年 | 91篇 |
2019年 | 72篇 |
2018年 | 68篇 |
2017年 | 67篇 |
2016年 | 86篇 |
2015年 | 57篇 |
2014年 | 102篇 |
2013年 | 115篇 |
2012年 | 72篇 |
2011年 | 88篇 |
2010年 | 59篇 |
2009年 | 79篇 |
2008年 | 54篇 |
2007年 | 62篇 |
2006年 | 46篇 |
2005年 | 52篇 |
2004年 | 37篇 |
2003年 | 38篇 |
2002年 | 29篇 |
2001年 | 16篇 |
2000年 | 19篇 |
1999年 | 9篇 |
1998年 | 24篇 |
1997年 | 14篇 |
1996年 | 12篇 |
1995年 | 3篇 |
1994年 | 5篇 |
1993年 | 6篇 |
1992年 | 5篇 |
1991年 | 4篇 |
1990年 | 5篇 |
1988年 | 3篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 5篇 |
1984年 | 6篇 |
1983年 | 2篇 |
1982年 | 5篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 4篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1936年 | 1篇 |
排序方式: 共有1641条查询结果,搜索用时 46 毫秒
991.
Congcong Chen Dr. He Zhu Prof. Dr. Bo-Geng Li Prof. Dr. Shiping Zhu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(15):3358-3363
Controlled synthesis of metal–organic framework (MOF)-based materials with multiple levels of porous structures across different length scales is of great interest in various applications but it still remains challenging. Most of the current strategies are time consuming and labor intensive, and not readily scaled-up. In this work, we introduce a straightforward one-pot fabrication strategy to prepare a robust and flexible hierarchically macro-meso-micro porous HKUST-1/polyvinylidene fluoride (PVDF) composite through solvent evaporation, in which MOF crystallization and polymer precipitation are combined together. The effect of the MOF precursor and the polymer initial amount on the morphology of the final composite was thoroughly studied. The interaction between the MOF and the polymer during the evaporation process is the key factor, which would limit the mobility of the polymer chains and cause instability in the MOF growth, thus endowing the composite with a hierarchically macro-meso-micro porous structure. This “all-in-one” porous structure could enhance the mass transport property of molecules within the composite. The obtained HKUST-1/PVDF composite showed an enhanced CO2 adsorption rate constant of 0.821 min−1 (298 K, 1 bar), which was 3.5 times higher than that of the pristine MOF. In addition, the composite showed an equivalent gas adsorption capacity under all tested pressures and greatly improved water stability. 相似文献
992.
You-Jun Yu Dr. Yun Hu Sheng-Yi Yang Wei Luo Dr. Yi Yuan Chen-Chen Peng Jin-Feng Liu Aziz Khan Prof. Zuo-Quan Jiang Prof. Liang-Sheng Liao 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(48):21762-21768
Derivatives based on anthryleno[1,2-b]pyrazine-2,3-dicarbonitrile (DCPA) are used as luminescent materials, to realize near-infrared (NIR) electroluminescence. By functionalizing DCPA with aromatic amine donors, two emitters named DCPA-TPA and DCPA-BBPA are designed and synthesized. Both molecules have large dipole moments owing to the strong intramolecular charge transfer interactions between the amine donors and the DCPA acceptor. Thus, compared with doped films, the emission of neat films of DCPA-TPA and DCPA-BBPA can fully fall into the NIR region (>700 nm) with increasing surrounding polarity by increasing doping ratio. Moreover, the non-doped devices based on DCPA-TPA and DCPA-BBPA provide NIR emission with peaks at 838 and 916 nm, respectively. A maximum radiance of 20707 mW Sr−1 m−2 was realized for the further optimized device based on DCPA-TPA. This work provides a simple and efficient strategy of molecular design for developing NIR emitting materials. 相似文献
993.
理性思维是中国学生发展核心素养的要点之一,是化学课程落实核心素养的重要内容。理性思维的精神实质在于追求本原,是一种与直觉经验相对应的高阶认知技能,是理科教学的目标和手段。化学教学实践中理性思维的缺失集中表现在教学活动缺乏理性思维的引导,具体在教学问题、教学方式、教学方法上表现突出。为此,课堂教学活动设计中可以从认知顺序、思维方式、思维方法的运用上落实理性思维的培养。 相似文献
994.
In this paper, we propose and study a first risk model in which the insurer may invest into a prevention plan which decreases claim intensity. We determine the optimal prevention investment for different risk indicators. In particular, we show that the prevention amount minimizing the ruin probability maximizes the adjustment coefficient in the classical ruin model with prevention, as well as the expected dividends until ruin in the model with dividends. We also show that the optimal prevention strategy is different if one aims at maximizing the average surplus at a fixed time horizon. A sensitivity analysis is carried out. We also prove that our results can be extended to the case where prevention starts to work only after a minimum prevention level threshold. 相似文献
995.
Jiuyang Li Guangming Wang Xuefeng Chen Xun Li Minjian Wu Shou Yuan Dr. Yunlong Zou Dr. Xuepu Wang Prof. Kaka Zhang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(35):e202200852
The past several years have witnessed the tremendous development of novel chemical structures, new design strategies and intriguing applications in the field of room-temperature phosphorescence (RTP) and organic afterglow materials. This Review article focuses on recent advancements of high-performance organic afterglow materials obtained by two-component design strategies such as a dopant-matrix, donor–acceptor, sensitization, and energy-transfer strategies. Based on some cutting-edge studies, organic afterglow efficiency has been largely improved, exceeding 90 % in several cases. Organic afterglow durations reach tens of seconds in phosphorescence systems and hours in donor–acceptor systems. Organic afterglow brightness outcompetes some inorganic afterglow materials in the first several seconds after ceasing excitation source. Organic afterglow colors cover the whole visible regions and extend to near-infrared regions with respectful afterglow efficiency. On the basis of these achievements, researchers demonstrate promising applications of organic afterglow materials in diverse fields, which has also been reviewed. 相似文献
996.
Tao Jiang Wenjing Nan Lianhuan Han Hang Wei Miao Wang Juan Peng Yong Chen Xu Hou Prof. Dongping Zhan 《Electroanalysis》2022,34(4):655-658
Mechanical fatigue and mechanical-chemical effect can harm the stability and durability of flexible electrochemical sensors and electronic devices. To solve the problem, we propose a rigidity/flexibility compatible strategy by implanting Prussian blue into the carbon nanotube array supported by polydimethylsiloxane (PDMS). The PDMS membrane is soft and flexible, and counteracts the external force; meanwhile, Prussian Blue@Carbon Nanotube Hybrid is hard and rigid for the reliable detection of hydrogen peroxide. Consequently, the cyclic voltammetric behavior of Prussian blue keep almost constant during the continuous bending experiments. The results indicate that the rigidity/flexibility compatible strategy is instructive to improve the performance of flexible electrochemical sensors and electronic devices. 相似文献
997.
近年来,滴滴和优步等网约车平台的出现给城市居民出行带来了新的选择,然而随着新政的实施以及垄断巨头的酝酿诞生,网约车平台是否会降补贴提车价成为消费者最为关心的问题。文章构建网约车平台和乘客之间的Stackelberg博弈模型,分析了网约车平台的补贴和抽成策略对乘客是否选择网约车出行的决策行为以及网约车市场均衡的影响。理论研究和仿真结果表明:网约车平台合理的补贴力度和抽成力度可以有效规避行政监管成本增加和乘客资源流失的风险,提高双方的收益,实现社会的帕累托最优。 相似文献
998.
999.
Dr. Anusha Sebastian Dr. Vunnam Srinivasulu Prof. Dr. Imad A. Abu-Yousef Prof. Dr. Orive Gorka Prof. Dr. Taleb H. Al-Tel 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(69):15710-15735
Diversity-oriented synthesis (DOS) has become a powerful synthetic tool that facilitates the construction of nature-inspired and privileged chemical space, particularly for sp3-rich non-flat scaffolds, which are needed for phenotypic screening campaigns. These diverse compound collections led to the discovery of novel chemotypes that can modulate the protein function in underrepresented biological space. In this context, starting material-driven DOS is one of the most important tools used to build diverse compound libraries with rich stereochemical and scaffold diversity. To this end, ene/yne tethered salicylaldehyde derivatives have emerged as a pluripotent chemical platform, the products of which led to the construction of a privileged chemical space with significant biological activities. In this review, various domino transformations employing o-alkene/alkyne tethered aryl aldehyde/ketone platforms are described and discussed, with emphasis on the period from 2011 to date. 相似文献
1000.
Denise Medeiros Selegato Rafael Teixeira Freire Alan César Pilon Carolina Rabal Biasetto Haroldo Cesar de Oliveira Lucas Magalhães de Abreu Angela Regina Araujo Vanderlan da Silva Bolzani Ian Castro-Gamboa 《Magnetic resonance in chemistry : MRC》2019,57(8):458-471
Traditionally, the screening of metabolites in microbial matrices is performed by monocultures. Nonetheless, the absence of biotic and abiotic interactions generally observed in nature still limit the chemical diversity and leads to “poorer” chemical profiles. Nowadays, several methods have been developed to determine the conditions under which cryptic genes are activated, in an attempt to induce these silenced biosynthetic pathways. Among those, the one strain, many compounds (OSMAC) strategy has been applied to enhance metabolic production by a systematic variation of growth parameters. The complexity of the chemical profiles from OSMAC experiments has required increasingly robust and accurate techniques. In this sense, deconvolution-based 1HNMR quantification have emerged as a promising methodology to decrease complexity and provide a comprehensive perspective for metabolomics studies. Our present work shows an integrated strategy for the increased production and rapid quantification of compounds from microbial sources. Specifically, an OSMAC design of experiments (DoE) was used to optimize the microbial production of bioactive fusaric acid, cytochalasin D and 3-nitropropionic acid, and Global Spectral Deconvolution (GSD)-based 1HNMR quantification was carried out for their measurement. The results showed that OSMAC increased the production of the metabolites by up to 33% and that GSD was able to extract accurate NMR integrals even in heavily coalescence spectral regions. Moreover, GSD-1HNMR quantification was reproducible for all species and exhibited validated results that were more selective and accurate than comparative methods. Overall, this strategy up-regulated important metabolites using a reduced number of experiments and provided fast analyte monitor directly in raw extracts. 相似文献