全文获取类型
收费全文 | 22064篇 |
免费 | 3418篇 |
国内免费 | 2420篇 |
专业分类
化学 | 15643篇 |
晶体学 | 264篇 |
力学 | 1322篇 |
综合类 | 187篇 |
数学 | 2287篇 |
物理学 | 8199篇 |
出版年
2024年 | 15篇 |
2023年 | 408篇 |
2022年 | 449篇 |
2021年 | 680篇 |
2020年 | 837篇 |
2019年 | 818篇 |
2018年 | 697篇 |
2017年 | 713篇 |
2016年 | 998篇 |
2015年 | 1001篇 |
2014年 | 1134篇 |
2013年 | 1576篇 |
2012年 | 1856篇 |
2011年 | 1992篇 |
2010年 | 1298篇 |
2009年 | 1267篇 |
2008年 | 1465篇 |
2007年 | 1351篇 |
2006年 | 1219篇 |
2005年 | 971篇 |
2004年 | 774篇 |
2003年 | 657篇 |
2002年 | 635篇 |
2001年 | 449篇 |
2000年 | 437篇 |
1999年 | 472篇 |
1998年 | 406篇 |
1997年 | 414篇 |
1996年 | 453篇 |
1995年 | 362篇 |
1994年 | 376篇 |
1993年 | 270篇 |
1992年 | 252篇 |
1991年 | 232篇 |
1990年 | 165篇 |
1989年 | 129篇 |
1988年 | 116篇 |
1987年 | 97篇 |
1986年 | 95篇 |
1985年 | 85篇 |
1984年 | 58篇 |
1983年 | 49篇 |
1982年 | 38篇 |
1981年 | 28篇 |
1980年 | 31篇 |
1979年 | 17篇 |
1978年 | 10篇 |
1977年 | 8篇 |
1975年 | 7篇 |
1973年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Meiling Xue Kanghui Lv Shengqiang Gao Xiangzhou Lu Yingjie Liu Shouke Yan 《Journal of polymer science. Part A, Polymer chemistry》2020,58(7):997-1010
To reduce the crystallization rate of polyoxymethylene (POM) to meet the requirement of thick-walled and large-sized articles production, and maintain high crystallinity as well as obtain refined crystalline grains to ensure the strength and stiffness simultaneously, thermoplastic phenolic resin (PF) and multiwalled carbon nanotubes (MWCNTs) were used as crystal growth inhibitor and nucleating agent, respectively, and their effects on the crystallization of POM were studied in details. The results showed that PF is an effective inhibitor and MWCNTs exhibits excellent nucleation effect on POM. Based on the obtained results, their synergistic influences on the crystallization process of POM were investigated. It is found that the objective of decreasing the crystallization rate while maintaining high crystallinity and forming fine crystalline grains can be realized. The 97/3/1 wt% POM/PF/MWCNTs, compared with those of neat POM, The T c shifts by 3.3°C to a lower temperature, the crystallization enthalpy increases by 16.1 J/g and the full width at half-maximum widens by 48.5%. The modulation effect of PF and MWCNTs on the crystallization is closely related to the PF content and dispersion, the distribution and dispersion of MWCNTs in the PF and POM phases. 相似文献
92.
Zhentao Hao Chuchu Chen Ting Shen Jiaxing Lu Hao-Cheng Yang Weihua Li 《Journal of polymer science. Part A, Polymer chemistry》2020,58(21):3031-3041
Slippery liquid-infused porous surface (SLIPS) is a rising star in corrosion protection owing to its outstanding corrosive medium resistance and self-healing property. The large-area and facile fabrication of SLIPS remains a challenge lying on the way of its practical application. Herein, we develop a novel SLIPS based on a porous polyvinylidene fluoride (PVDF) substrate fabricated by thermally induced phase separation. A sphere-packing structure can be easily obtained by blade-coating followed by cooling. The SLIPS exhibits an extremely low sliding angle of 5.8° so that it can resist the fouling of even the Chinese ink, ascribing to its slippery dynamic surface with low surface energy. We also evaluated the anti-corrosion performance of the SLIPS and superhydrophobic PVDF coating by electrochemical impedance spectroscopy (EIS) and scanning Kelvin probe technique (SKP), both of which exhibited enhanced corrosion resistance in 3.5 wt% NaCl solution due to the physical oil and air barriers against the corrosive medium penetration. Nevertheless, the SLIPS coatings performed outstanding self-healing properties because of the high fluidity of infused oil to recover the surface damages, and the self-healing process was recorded by the SKP. 相似文献
93.
Forrest Nichols Dr. Jia En Lu Rene Mercado Ryan Dudschus Prof. Frank Bridges Prof. Shaowei Chen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(18):4136-4142
Electrochemical hydrogen generation is a rising prospect for future renewable energy storage and conversion. Platinum remains a leading choice of catalyst, but because of its high cost and low natural abundance, it is critical to optimize its use. In the present study, platinum oxide nanoparticles of approximately 2 nm in diameter are deposited on carbon nitride (C3N4) nanosheets by thermal refluxing of C3N4 and PtCl2 or PtCl4 in water. These nanoparticles exhibit apparent electrocatalytic activity toward the hydrogen evolution reaction (HER) in acid. Interestingly, the HER activity increases with increasing Pt4+ concentration in the nanoparticles, and the optimized catalyst even outperforms commercial Pt/C, exhibiting an overpotential of only −7.7 mV to reach the current density of 10 mA cm−2 and a Tafel slope of −26.3 mV dec−1. The results from this study suggest that the future design of platinum oxide catalysts should strive to maximize the Pt4+ sites and minimize the formation of the less active Pt2+ species. 相似文献
94.
Qin Zhu Lu Lin Rulin Qiu Prof. Dr. Jun Zhu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(24):5381-5387
Aromaticity is one of the most basic concepts in organic chemistry. The planar Möbius aromatic metallapentalynes and metallapentalenes have attracted considerable attention in the past few years. However, the aromaticity of metallapentalenes containing heteroatoms (such as B, N, and O), termed as hetero-metallapentalenes, is rarely studied. Herein, the stability and aromaticity of a series of hetero-metallapentalenes are theoretically investigated. The results reveal lower aromaticity in metallaborapentalene, comparable aromaticity in metallazapentalene, and nonaromaticity in metalloxapentalene relative to that of metallapentalene. Moreover, the effect of Lewis bases on the aromaticity and stability of metallaborapentalene is discussed. These results provide useful information for experimental chemists to realize more hetero-metallapentalenes. 相似文献
95.
Wenxiang Liu Lele Lu Qiang Li Boyuan Wu Ruizhe Zhang Wei Shi Peng Cheng 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(53):12206-12211
Photocatalytic hydrogen evolution by water splitting is highly important for the application of hydrogen energy and the replacement of fossil fuel by solar energy, which needs the development of efficient catalysts with long-term catalytic stability under light irradiation in aqueous solution. Herein, Zn0.5Cd0.5S solid solution was synthesized by a metal–organic framework-templated strategy and then loaded with MoS2 by a hydrothermal method to fabricate a MoS2/Zn0.5Cd0.5S heterojunction for photocatalytic hydrogen evolution. The composition of MoS2/Zn0.5Cd0.5S was fine-tuned to obtain the optimized 5 wt % MoS2/Zn0.5Cd0.5S heterojunction, which showed a superior hydrogen evolution rate of 23.80 mmol h−1 g−1 and steady photocatalytic stability over 25 h. The photocatalytic performance is due to the appropriate composition and the formation of an intimate interface between MoS2 and Zn0.5Cd0.5S, which endows the photocatalyst with high light-harvesting ability and effective separation of photogenerated carriers. 相似文献
96.
Guiqiang Cao Zhikang Wang Da Bi Prof. Jing Zheng Prof. Qingxue Lai Prof. Yanyu Liang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(45):10314-10320
Lithium-sulfur batteries have been considered as potential electrochemical energy-storage devices owing to their satisfactory theoretical energy density. Nonetheless, the inferior conversion efficiency of polysulfides in essence leads to fast capacity decay during the discharge/charge cycle. In this work, it is successfully demonstrated that the conversion efficiency of lithium polysulfides is remarkably enhanced by employing a well-distributed atomic-scale Fe-based catalyst immobilized on nitrogen-doped graphene (Fe@NG) as a coating of separator in lithium-sulfur batteries. The quantitative electrocatalytic efficiency of the conversion of lithium polysulfides is determined through cyclic voltammetry. It is also proven that the Fe-NX configuration with highly catalytic activity is quite beneficial for the conversion of lithium polysulfides. In addition, the adsorption and permeation experiments distinctly indicate that the strong anchoring effect, originated from the charge redistribution of N doping into the graphene matrix, inhibits the movement of lithium polysulfides. Thanks to these advantages, if the as-prepared Fe@NG catalyst is combined with polypropylene and applied as a separator (Fe@NG/PP) in Li-S batteries, a high initial capacity (1616 mA h g−1 at 0.1 C), excellent capacity retention (93 % at 0.2 C, 70 % at 2 C), and superb rate performance (820 mA h g−1 at 2 C) are achieved. 相似文献
97.
Honghua Zhang Huihong Wang Yi Jiang Fei Cao Weiwei Gao Longqing Zhu Yuhang Yang Xiaodong Wang Yongqiang Wang Jinhong Chen Yiyue Feng Xuemei Deng Yingmei Lu Xiaoling Hu Xiangxiang Li Juan Zhang Tao Shi Prof. Zhen Wang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(72):17289-17317
Sulfur-containing scaffold, as a ubiquitous structural motif, has been frequently used in natural products, bioactive chemicals and pharmaceuticals, particularly C−S/N−S bonds are indispensable in many biological important compounds and pharmaceuticals. Development of mild and general methods for C−S/N−S bonds formation has great significance in modern research. Iodine and its derivatives have been recognized as inexpensive, environmentally benign and easy-handled catalysts or reagents to promote the construction of C−S/N−S bonds under mild reaction conditions, with good regioselectivities and broad substrate scope. Especially based on this, several new strategies, such as oxidation relay strategy, have been greatly developed and accelerated the advancement of this field. This review focuses on recent advances in iodine and its derivatives promoted hybridized C−S/N−S bonds formation. The features and mechanisms of corresponding reactions are summarized and the results of some cases are compared with those of previous reports. In addition, the future of this domain is discussed. 相似文献
98.
99.
100.