全文获取类型
收费全文 | 109926篇 |
免费 | 14936篇 |
国内免费 | 12873篇 |
专业分类
化学 | 54178篇 |
晶体学 | 1083篇 |
力学 | 5583篇 |
综合类 | 1174篇 |
数学 | 10103篇 |
物理学 | 30446篇 |
无线电 | 35168篇 |
出版年
2024年 | 457篇 |
2023年 | 2379篇 |
2022年 | 3275篇 |
2021年 | 3938篇 |
2020年 | 3673篇 |
2019年 | 3505篇 |
2018年 | 3083篇 |
2017年 | 3157篇 |
2016年 | 4089篇 |
2015年 | 4700篇 |
2014年 | 5600篇 |
2013年 | 7310篇 |
2012年 | 8439篇 |
2011年 | 8672篇 |
2010年 | 6772篇 |
2009年 | 6825篇 |
2008年 | 7216篇 |
2007年 | 6693篇 |
2006年 | 6399篇 |
2005年 | 5621篇 |
2004年 | 4265篇 |
2003年 | 3492篇 |
2002年 | 3172篇 |
2001年 | 2806篇 |
2000年 | 2712篇 |
1999年 | 2526篇 |
1998年 | 2090篇 |
1997年 | 1772篇 |
1996年 | 1787篇 |
1995年 | 1606篇 |
1994年 | 1445篇 |
1993年 | 1290篇 |
1992年 | 1155篇 |
1991年 | 950篇 |
1990年 | 787篇 |
1989年 | 660篇 |
1988年 | 536篇 |
1987年 | 454篇 |
1986年 | 388篇 |
1985年 | 370篇 |
1984年 | 265篇 |
1983年 | 232篇 |
1982年 | 196篇 |
1981年 | 151篇 |
1980年 | 107篇 |
1979年 | 73篇 |
1978年 | 72篇 |
1977年 | 67篇 |
1976年 | 63篇 |
1973年 | 70篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
992.
993.
Zi-jin Zhang Zhi-jie Tang Zhen-yu Zhu Zhao-ming Cao Hong-juan Chen Wei-juan Zheng Xin Hu Hong-zhen Lian Li Mao 《Journal of nanoparticle research》2018,20(10):263
Zinc oxide nanoparticle is one of the nanomaterials people engaged most in their life and its health effect has been taken into concern. In this work, A549 cell line was used as cell model, and the cytotoxicity of zinc oxide nanoparticles was revealed to be concentration-dependent. Through the measurement of cellular proteome, much more differentially expressed proteins were observed after the cells being treated for 9 h than 24 h. Also, most of these proteins expressed in the pattern which showed a significant decrease after exposure to zinc oxide nanoparticles and then an increase at 24 h. Intracellular reactive oxygen species and glutathione determination indicated that high level of oxidative stress was presented in cell after treatment with zinc oxide nanoparticles for 9 h. It can be observed from western blot analysis that the expression of NF-κB p65, PNPase, and HSP90 rose significantly after 9 h of exposure. Thus, a deduction was reached that toxicity of nanoparticles consists both of particle toxicity and ion toxicity, and a long-time treatment may conceal the toxicity induced by particles. The conclusion we made highlighted the importance of exposure time in the study of nanoparticle toxicity and would provide a new perspective for studying toxicity mechanism of nanoparticles. 相似文献
994.
Chen Yang Ying Chen Dan Liu Jinfeng Wang Cheng Chen Jiemin Wang Ye Fan Shaoming Huang Weiwei Lei 《Frontiers of Physics》2018,13(4):138101
Vertically aligned γ-AlOOH nanosheets (NSs) have been successfully fabricated on flexible Al foils via a solvothermal route without morphology-directing agents. Three different reaction temperature (25, 80, and 120 ?C) and time (30 min, 45 min, and 24 h) are discussed for the growth period, which efficiently tune the density and size of the γ-AlOOH NSs. Meanwhile, the growth speed of the nanosheets confirms that dominant growth stage is seen in the initial 45 min. Furthermore, the interlayer of the γ-AlOOH NSs displays an average height of 140 nm and superhydrophilicity. By dynamic adsorption, the assynthesized γ-AlOOH NSs exhibit an outstanding NH3 adsorption capacity of up to 146 mg/g and stably excellent regeneration for 5 cycles. The mechanism of NH3 adsorption on the in-plane of the γ-AlOOH NSs is explained by the Lewis acid/base theory. The H-bond interactions among the NH3 molecules and the edge groups (-OH) further improve the capture ability of the nanosheets. 相似文献
995.
Dan-Li Hong Dr. Yang-Hui Luo Xiao-Tong He Zi-Yue Zheng Shan Su Jia-Ying Wang Cong Wang Chen Chen Prof. Bai-Wang Sun 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(37):8805-8812
Precise revealing the mechanisms of excited-state intermolecular proton transfer (ESPT) and the corresponding geometrical relaxation upon photoexcitation and photoionization remains a formidable challenge. In this work, the compound (E)-4-(((4H-1,2,4-triazol-4-yl)imino)methyl)-2,6-dimethoxyphenol (TIMDP) adopting a D-π-A molecular architecture featuring a significant intramolecular charge transfer (ICT) effect has been designed. With the presence of perchloric acid (35 %), TIMDP can be dissolved through the formation of a HClO4–H2O–OH(TIMDP)–N(TIMDP) hydrogen-bonding bridge. At the ground state, the ICT effect is dominant, giving birth to crystals of TIMDP. Upon external stimuli (e.g., UV light irradiation, electro field), the excited state is achieved, which weakens the ICT effect, and significantly promotes the ESPT effect along the hydrogen-bonding bridge, resulting in crystals of [HTIMDP]+ ⋅ [H2O] ⋅ [ClO4]−. As a consequence, the mechanisms of the ESPT can be investigated, which distorted the D-π-A molecular architecture, tuned the emission color with the largest Stokes shift of 242 nm, and finally, high photoluminescence quantum yields (12 %) and long fluorescence lifetimes (8.6 μs) have achieved. These results not only provide new insight into ESPT mechanisms, but also open a new avenue for the design of efficient ESPT emitters. 相似文献
996.
Liwei Chen Prof. Dr. Jinkee Hong Prof. Dr. Hans-Jürgen Butt Prof. Dr. Sanghyuk Wooh 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(18):4535-4542
Metal oxide photocatalysts (MOPCs) decompose organic molecules under illumination. However, the application of MOPCs in industry and research is currently limited by their intrinsic hydrophilicity because MOPCs can be wetted by most liquids. To achieve liquid repellency, the surface needs to possess a low surface energy, but most organic molecules with low surface energy are degraded by photocatalytic activity. Herein, current methods to achieve liquid repellency on MOPCs, while preventing degradation of hydrophobic coatings, are reviewed. Classically, composite materials containing MOPCs and hydrophobic organic compounds possess good liquid repellency. However, composites normally form irregular coatings and are hard to prepare on surfaces such as those that are mesoporous or nanostructured. In addition, the adhesion of composites to substrates is often weak, resulting in delamination. Recent studies have shown that the direct grafting reaction of polydimethylsiloxane (PDMS) from silicone oil (methyl-terminated PDMS) under illumination results in a stable polymer brush. This easy and simple grafting method allows us to create stable liquid-repellent surfaces on MOPCs of various types, structures, and sizes. In particular, super-liquid-repellent drops with an underlying air layer can be created on PDMS-grafted nano-/microstructured MOPCs. Potential applications of surfaces combining liquid repellency and photocatalytic activity are also discussed; thus offering new ways of using MOPCs in a wider range of applications. 相似文献
997.
Lianghao Song Tiantian Xu Daowei Gao Prof. Xun Hu Prof. Cuncheng Li Prof. Shun Li Prof. Guozhu Chen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(26):6621-6627
CeO2-based catalysts are widely studied in catalysis fields. Developing one novel synthetic approach to increase the intimate contact between CeO2 and secondary species is of particular importance for enhancing catalytic activities. Herein, an interfacial reaction between metal–organic framework (MOF)-derived carbon and KMnO4 to synthesize CeO2−MnO2, in which carbon is derived from the pyrolysis of Ce-MOFs under an inert atmosphere, is described. The MOF-derived carbon is found to restrain the growth of CeO2 crystallites under a high calcination temperature and, more importantly, intimate contact within CeO2/C is conveyed to CeO2/MnO2 after the interfacial reaction; this is responsible for the high catalytic activity of CeO2−MnO2 towards CO oxidation. 相似文献
998.
Fangwei Ding Prof. Debin Xia Weipeng Sun Wei Chen Prof. Yulin Yang Prof. Kaifeng Lin Prof. Feibao Zhang Prof. Xugang Guo 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(66):15106-15111
A series of novel sulfur-containing bent N-heteroacenes were constructed and characterized by NMR and UV/Vis spectroscopy, cyclic voltammetry, and single-crystal X-ray diffraction. By introducing sulfur-containing groups (thio, sulfinyl, and sulfonyl) into bent azaacenes, their electronic delocalization was improved and frontier energy levels were modulated. The target products displayed tunable optical and electronic properties through altering the valence of sulfur and fused length of the azaacenes. For the first time, typical products were utilized as organic field effect transistor materials, affording promising results. 相似文献
999.
Ben-Xian Xiao Xin-Yue Gao Dr. Wei Du Prof. Dr. Ying-Chun Chen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(7):1607-1613
Numerous protocols have been developed for the functionalization of aromatic substances. Among them, the strategy by which aromatic substrates are activated in situ to generate dearomatized intermediates is highly efficient but challenging, especially in the field of asymmetric catalysis. In this Concept article, the application of some well-established chiral Lewis base catalysis, including primary/secondary amines and N-heterocyclic carbenes, that can covalently form catalyst-tethered dearomatized ortho/para-quinodimethane species with diverse heteroaryl and aryl carbonyl substrates is summarized in a number of asymmetric cycloaddition and addition reactions with diverse reagents generally having electrophilic properties. As a result, a variety of enantioenriched aromatic products with higher molecular complexity are constructed effectively through a rearomatization process. 相似文献
1000.