全文获取类型
收费全文 | 16887篇 |
免费 | 3079篇 |
国内免费 | 2692篇 |
专业分类
化学 | 13445篇 |
晶体学 | 269篇 |
力学 | 866篇 |
综合类 | 199篇 |
数学 | 2037篇 |
物理学 | 5842篇 |
出版年
2024年 | 23篇 |
2023年 | 297篇 |
2022年 | 623篇 |
2021年 | 549篇 |
2020年 | 682篇 |
2019年 | 773篇 |
2018年 | 604篇 |
2017年 | 614篇 |
2016年 | 820篇 |
2015年 | 915篇 |
2014年 | 1035篇 |
2013年 | 1353篇 |
2012年 | 1588篇 |
2011年 | 1586篇 |
2010年 | 1174篇 |
2009年 | 1151篇 |
2008年 | 1226篇 |
2007年 | 1070篇 |
2006年 | 922篇 |
2005年 | 885篇 |
2004年 | 761篇 |
2003年 | 586篇 |
2002年 | 614篇 |
2001年 | 513篇 |
2000年 | 380篇 |
1999年 | 316篇 |
1998年 | 261篇 |
1997年 | 214篇 |
1996年 | 188篇 |
1995年 | 149篇 |
1994年 | 146篇 |
1993年 | 99篇 |
1992年 | 85篇 |
1991年 | 91篇 |
1990年 | 90篇 |
1989年 | 54篇 |
1988年 | 55篇 |
1987年 | 34篇 |
1986年 | 31篇 |
1985年 | 27篇 |
1984年 | 8篇 |
1983年 | 10篇 |
1982年 | 10篇 |
1981年 | 10篇 |
1980年 | 6篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1959年 | 2篇 |
1957年 | 2篇 |
1936年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
911.
Weizhao Hu Bibo Wang Xin Wang Hua Ge Lei Song Jian Wang Yuan Hu 《Journal of Thermal Analysis and Calorimetry》2014,117(1):27-38
Ethyl cellulose, a widely used bio-degradable shell material, microencapsulated ammonium polyphosphate (MAPP) was added to the bio-degradable poly(butylene succinate) (PBS) to improve its flame retardancy, compatibility, and thermal stability. The MAPP was well characterized by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy (SEM), water contact angle, and thermogravimetric (TG) analysis. The SEM results indicate the improved dispersion of MAPP into PBS matrix and the formation of the strong interfacial adhesion between MAPP and PBS than APP. With the incorporation of MAPP and char-forming agent into PBS, the limiting oxygen index of the composite was increased to 35.5 %, and the sample can pass the UL-94 V-0 rating, while the un-microencapsulated counterpart cannot reach the rating. The cone calorimeter test showed that the peak heat release rate was decreased by 46.7 % and the burning time was also prolonged compared to the pure PBS. The increased melt flow index and rheology test indicated the increase of viscosity and the improvement of anti-dripping properties. Moreover, the mechanical properties and thermal stability of MAPP composite were also obviously enhanced after the microencapsulation by mechanical, dynamical mechanical thermal analysis, and TG analysis. 相似文献
912.
Metal Oxide‐Coated Three‐Dimensional Graphene Prepared by the Use of Metal–Organic Frameworks as Precursors
下载免费PDF全文
![点击此处可从《Angewandte Chemie (International ed. in English)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Xianhong Rui Wenhui Shi Prof. Qingyu Yan Prof. Hua Zhang 《Angewandte Chemie (International ed. in English)》2014,53(5):1404-1409
A simple method for the preparation of metal‐oxide‐coated three‐dimensional (3D) graphene composites was developed. The metal–organic frameworks (MOFs) that served as the precursors of the metal oxides were first synthesized on the 3D graphene networks (3DGNs). The desired metal oxide/3DGN composites were then obtained by a two‐step annealing process. As a proof‐of‐concept application, the obtained ZnO/3DGN and Fe2O3/3DGN materials were used in a photocatalytic reaction and a lithium‐ion battery, respectively. We believe this method could be extended to the synthesis of other metal oxide/3DGN composites with 3D structures simply through the appropriate choice of specific MOFs as precursors. 相似文献
913.
The hydration of NaCl has been widely studied and believed to be important for understanding the mechanisms of salt dissolution in water and the formation of ice nucleus, cloud, and atmospheric aerosols. However, understanding on the poly-NaCl ion pair interacting with water is very limited. Here, we investigated the adsorption of water molecules on (NaCl)3, using both theoretical calculations and anion photoelectron spectroscopy measurements. The calculated vertical detachment energies and the experimental ones agree well with each other. Furthermore, we found that, for neutral (NaCl)3(H2O) n (n = 2–7) clusters, the water-doped cuboid and structures formed by adding water molecules on the Na–Cl edges of the cuboid are energetically favored; water molecules preferentially bind to the Na–Cl edge if the NaCl ion pair has larger partial charges than others. We also found the anionic structures are more various compared with neutral ones, and the Na+ and Cl? ions are hydrated more easily in the anionic clusters than in the corresponding neutrals. 相似文献
914.
Electrochemical Synthesis of Tetrahexahedral Rhodium Nanocrystals with Extraordinarily High Surface Energy and High Electrocatalytic Activity
下载免费PDF全文
![点击此处可从《Angewandte Chemie (International ed. in English)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Neng‐Fei Yu Dr. Na Tian Dr. Zhi‐You Zhou Long Huang Jing Xiao Yu‐Hua Wen Prof. Shi‐Gang Sun 《Angewandte Chemie (International ed. in English)》2014,53(20):5097-5101
Noble metal nanocrystals (NCs) enclosed with high‐index facets hold a high catalytic activity thanks to the high density of low‐coordinated step atoms that they exposed on their surface. Shape‐control synthesis of the metal NCs with high‐index facets presents a big challenge owing to the high surface energy of the NCs, and the shape control for metal Rh is even more difficult because of its extraordinarily high surface energy in comparison with Pt, Pd, and Au. The successful synthesis is presented of tetrahexahedral Rh NCs (THH Rh NCs) enclosed by {830} high‐index facets through the dynamic oxygen adsorption/desorption mediated by square‐wave potential. The results demonstrate that the THH Rh NCs exhibit greatly enhanced catalytic activity over commercial Rh black catalyst for the electrooxidation of ethanol and CO. 相似文献
915.
Mechanistic Insights into the Interface‐Directed Transformation of Thiols into Disulfides and Molecular Hydrogen by Visible‐Light Irradiation of Quantum Dots
下载免费PDF全文
![点击此处可从《Angewandte Chemie (International ed. in English)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Xu‐Bing Li Zhi‐Jun Li Yu‐Ji Gao Qing‐Yuan Meng Shan Yu Prof. Dr. Richard G. Weiss Prof. Dr. Chen‐Ho Tung Prof. Dr. Li‐Zhu Wu 《Angewandte Chemie (International ed. in English)》2014,53(8):2085-2089
Quantum dots (QDs) offer new and versatile ways to harvest light energy. However, there are few examples involving the utilization of QDs in organic synthesis. Visible‐light irradiation of CdSe QDs was found to result in virtually quantitative coupling of a variety of thiols to give disulfides and H2 without the need for sacrificial reagents or external oxidants. The addition of small amounts of nickel(II) salts dramatically improved the efficiency and conversion through facilitating the formation of hydrogen atoms, thereby leading to faster regeneration of the ground‐state QDs. Mechanistic studies reveal that the coupling reaction occurs on the QD surfaces rather than in solution and offer a blueprint for how these QDs may be used in other photocatalytic applications. Because no sacrificial agent or oxidant is necessary and the catalyst is reusable, this method may be useful for the formation of disulfide bonds in proteins as well as in other systems sensitive to the presence of oxidants. 相似文献
916.
Dr. Chunxiu Hua Dr. Xiangpeng Fang Prof. Zhaoxiang Wang Prof. Liquan Chen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(18):5487-5491
It is well accepted that metallic tin as a discharge (reduction) product of SnOx cannot be electrochemically oxidized below 3.00 V versus Li+/Li0 due to the high stability of Li2O, though a similar oxidation can usually occur for a transition metal formed from the corresponding oxide. In this work, nanosized Ni2SnO4 and NiO/SnO2 nanocomposite were synthesized by coprecipitation reactions and subsequent heat treatment. Owing to the catalytic effect of nanosized metallic nickel, metallic tin can be electrochemically oxidized to SnO2 below 3.00 V. As a result, the reversible lithium‐storage capacities of the nanocomposite reach 970 mAh g?1 or above, much higher than the theoretical capacity (ca. 750 mAh g?1) of SnO2, NiO, or their composites. These findings extend the well‐known electrochemical conversion reaction to non‐transition‐metal compounds and may have important applications, for example, in constructing high‐capacity electrode materials and efficient catalysts. 相似文献
917.
Phenylene‐Coated Magnetic Nanoparticles that Boost Aqueous Asymmetric Transfer Hydrogenation Reactions
下载免费PDF全文
![点击此处可从《Chemistry (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Dr. Xiaoshuang Gao Rui Liu Dacheng Zhang Meng Wu Tanyu Cheng Prof. Guohua Liu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(6):1515-1519
Phenylene‐coated organorhodium‐functionalized magnetic nanoparticles are developed through co‐condensation of chiral 4‐(trimethoxysilyl)ethyl)phenylsulfonyl‐1,2‐diphenylethylene‐diamine and 1,4‐bis(triethyoxysilyl)benzene onto Fe3O4 followed complexation with [{Cp*RhCl2}2]. This magnetic catalyst exhibits excellent catalytic activity and high enantioselectivity in asymmetric transfer hydrogenation in aqueous medium. Such activity is attributed to the high hydrophobicity and the confined nature of the chiral organorhodium catalyst. The magnetic catalyst can be easily recovered by using a small external magnet and it can be reused for at least 10 times without loss of its catalytic activity. This characteristic makes it an attractive catalyst for environmentally friendly organic syntheses. 相似文献
918.
Qiang Li Dr. Lei Liu Shuai Zhang Meng Xu Xueqin Wang Prof. Chen Wang Prof. Flemming Besenbacher Prof. Mingdong Dong 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(24):7236-7240
Graphene oxide (GO) is utilized as the modulator to tune the formation and development of amyloid fibrils (Aβ33–42). Atomic force microscopy temporal evolution measurements reveal that the initial binding between the peptide monomer and the large available surface of the GO sheets can redirect the assembly pathway of amyloid beta. The results support the possibility to develop graphene‐based materials to inhibit amyloidosis. 相似文献
919.
Bin Zhou Yedi Xing Prof. Shu Miao Prof. Mingrun Li Prof. Wen‐Hua Zhang Prof. Can Li 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(39):12426-12431
A facile colloidal approach to synthesize Ag8(Ge1?x,Snx)(S6?y,Sey) nanocrystals (NCs) in a highly controlled way across the entire compositional ranges (0≤x≤1, 0≤y≤6) has been developed. The NCs exhibit a uniform size distribution, highly crystalline structure, over 1 g scalable synthesis, and tunable band gaps in the range of 0.88–1.45 eV by varying their chemical compositions. The Ag8GeS6 NCs with a band gap of approximately 1.45 eV were employed as a model light harvester to assess their applicability in solar cells by a full solution‐processing device, yielding an efficiency of 0.28 % under AM1.5 illumination, demonstrating their application potential in solar energy utilization. 相似文献
920.
Chemical and Toxicological Investigations of a Previously Unknown Poisonous European Mushroom Tricholoma terreum
下载免费PDF全文
![点击此处可从《Chemistry (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Xia Yin Dr. Tao Feng Prof. Jian‐Hua Shang Yun‐Li Zhao Fang Wang Zheng‐Hui Li Ze‐Jun Dong Prof. Dr. Xiao‐Dong Luo Prof. Dr. Ji‐Kai Liu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(23):7001-7009
The established tradition of consuming and marketing wild mushrooms has focused attention on mycotoxicity, which has become a global issue. In the present study, we describe the toxins found in a previously unknown poisonous European mushroom Tricholoma terreum. Fifteen new triterpenoids terreolides A–F ( 1 – 6 ) and saponaceolides H–P ( 8 – 16 ) were isolated from the fruiting bodies of the toxic mushroom T. terreum. Terreolides A–C ( 1 – 3 ) possessed a unique 5/6/7 trioxaspiroketal system, whereas terreolides D–F ( 4 – 6 ) possessed an unprecedented carbon skeleton. Two abundant compounds in the mushroom, saponaceolide B ( 7 ) and saponaceolide M ( 13 ), displayed acute toxicity, with LD50 values of 88.3 and 63.7 mg kg?1 when administered orally in mice. Both compounds were found to increase serum creatine kinase levels in mice, indicating that T. terreum may be the cause of mushroom poisoning ultimately leading to rhabdomyolysis. 相似文献