全文获取类型
收费全文 | 16696篇 |
免费 | 2874篇 |
国内免费 | 2152篇 |
专业分类
化学 | 12679篇 |
晶体学 | 216篇 |
力学 | 917篇 |
综合类 | 115篇 |
数学 | 1631篇 |
物理学 | 6164篇 |
出版年
2024年 | 32篇 |
2023年 | 306篇 |
2022年 | 508篇 |
2021年 | 588篇 |
2020年 | 714篇 |
2019年 | 728篇 |
2018年 | 608篇 |
2017年 | 513篇 |
2016年 | 836篇 |
2015年 | 816篇 |
2014年 | 935篇 |
2013年 | 1314篇 |
2012年 | 1480篇 |
2011年 | 1464篇 |
2010年 | 1037篇 |
2009年 | 1041篇 |
2008年 | 1164篇 |
2007年 | 1058篇 |
2006年 | 937篇 |
2005年 | 836篇 |
2004年 | 684篇 |
2003年 | 579篇 |
2002年 | 612篇 |
2001年 | 442篇 |
2000年 | 337篇 |
1999年 | 331篇 |
1998年 | 269篇 |
1997年 | 238篇 |
1996年 | 216篇 |
1995年 | 178篇 |
1994年 | 148篇 |
1993年 | 121篇 |
1992年 | 107篇 |
1991年 | 112篇 |
1990年 | 80篇 |
1989年 | 69篇 |
1988年 | 44篇 |
1987年 | 33篇 |
1986年 | 39篇 |
1985年 | 40篇 |
1984年 | 21篇 |
1983年 | 18篇 |
1982年 | 15篇 |
1981年 | 19篇 |
1980年 | 9篇 |
1975年 | 7篇 |
1974年 | 6篇 |
1973年 | 5篇 |
1971年 | 5篇 |
1936年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 109 毫秒
961.
通过静电吸引策略将具有高度分散性的原子精确纳米团簇[Pd3Cl(PPh2)2(PPh3)3]+(Pd3Cl)负载在介孔SBA-15棒上。结构明确的Pd3Cl/SBA-15催化剂在以水作为溶剂以及温和的反应条件下对催化Sonogashira碳-碳偶联反应展现了较好的催化性能以及循环性。在此基础上,我们研究了Pd3Cl团簇结构与性能之间的关系,并证实内核的Pdδ+(0<δ<2)与配体之间的协同效应是催化反应的关键。 相似文献
962.
Volume expansion and polysulfide shuttle effect are the main barriers for the commercialization of lithium-sulfur(Li-S) battery.In this work,we in-situ polymerized a cross-linked binder in sulfur cathode to solve the aforementioned problems using a facile method under mild conditions.Polycarbonate diol(PCDL),triethanolamine(TEA) and hexamethylene diisocyanate(HDI) were chosen as precursors to prepare the cross-linked binder.The in-situ polymerized binder(PTH) builds a strong network in sulfur cathode,which could restrain the volume expansion of sulfu r.Moreover,by adopting functional groups of oxygen atoms and nitrogen atoms,the binder could effectively facilitate transportation of Li-ion and adsorb polysulfide chemically.The Li-S battery with bare sulfur and carbon/sulfur composite cathodes and cross-linked PTH binder displays much better electrochemical performance than that of the battery with PVDF.The PTH-bare S cathode with a mass loading of 5.97 mg/cm^2 could deliver a capacity of 733.3 mAh/g at 0.2 C,and remained 585.5 mAh/g after 100 cycles.This in-situ polymerized binder is proved to be quite effective on restraining the volume expansion and suppressing polysulfide shuttle effect,then improving the electrochemical performance of Li-S battery. 相似文献
963.
Energy storage will witness a leap of understanding of new battery chemistries.Considering the safety that cannot be compromised,new aqueous batteries may surface as the solutions to meet the immense market needs,where the growth of renewables is no longer limited by the lack of storage.Aqueous Zn-metal batteries are intriguing candidates to deliver the desirable properties and exhibit competitive levelized energy cost.However,the fact that most commercial Zn batteries are primary batteries states the difficulty of reversibility for the reactions of electrodes in such batteries.This article will highlight the practical needs that guide the development of storage batteries.The causes of irreversibility for both cathode and zinc metal anode are discussed,and the potential solutions for these challenges are summarized.Zn metal batteries may one day address the storage needs,and there exists a vast potential to further improve the properties of reactions in this battery. 相似文献
964.
ZHAO Weifeng HAO Ning ZHANG Gai MA Aijie CHEN Weixing ZHOU Hongwei YANG Dong XU Ben Bin KONG Jie 《高等学校化学研究》2020,36(6):1265-1271
An in situ strategy was introduced for synthesizing carbon modified graphitic carbon nitride(g-C3N4) by using urea/4-aminobenzoic acid(PABA) co-crystal(PABA@Urea) as precursor materials. Via co-calcination of the PABA co-former and the urea in PABA@Urea co-crystals, C guest species were generated and compounded into g-C3N4 matrix in situ by replacing the lattice N of the carbon nitride and forming carbon dots onto its layer surface. The carbon modification dramatically enhanced visible-light harvesting and charge carrier separation. Therefore, visible light photo-catalytic oxidation of methylene blue(MB) pollution in water over the carbon modified g-C3N4(C/g-C3N4) was notably improved. Up to 99% of methylene blue(MB) was eliminated within 60 min by the optimal sample prepared from the PABA@Urea co-crystal with a PABA content of 0.1%(mass ratio), faster than the degradation rate over bare g-C3N4. The present study demonstrates a new way to boost up the photocatalysis performance of g-C3N4, which holds great potential concerning the degradation of organic dyes from water. 相似文献
965.
Qi Wan Yan Deng Yaoqing Huang Zhihui Yu Chunli Wang Ke Wang Assoc. Prof. Jibin Dong Prof. Ying Chen 《ChemistryOpen》2020,9(2):176-182
Fifteen novel furoxan-based nitric oxide (NO) releasing hybrids of estradiol derivatives were synthesized and evaluated in vitro anti-proliferative activity in MDA-MB-231, A2780, Hela and HUVEC cell lines. Most of them displayed potent anti-proliferative effects. Among the compounds, 4-bromo-3-((phenylsulfonyl)-1,2,5-oxadiazole 2-oxide)-oxy-propoxy-estradiol ( 11 b ) exhibited the best activity with IC50 values of 3.58–0.0008 μM. Preliminary pharmacological studies showed that 11 b induced apoptosis and hardly affected the cell cycle of MDA-MB-231 cell line. NO-releasing capacity and inhibition of ERK/MAPK pathway signaling might explain the potent antineoplastic activity of these compounds. The preliminary structure-activity relationship (SAR) showed that steroidal scaffolds with a linker in 3-position were favorable moieties to evidently increase the bioactivities of these hybrids. Overall, these results implied that 11 b merited to be further investigated as a promising anti-cancer candidate. 相似文献
966.
The ATP-binding cassette (ABC) transporter P-glycoprotein (P-gp) is a physiologically essential membrane protein that protects many tissues against xenobiotic molecules, but limits the access of chemotherapeutics into tumor cells, thus contributing to multidrug resistance. The atomic-level mechanism of how substrates and inhibitors differentially affect the ATP hydrolysis by P-gp remains to be elucidated. In this work, atomistic molecular dynamics simulations in an explicit membrane/water environment were performed to explore the effects of substrate and inhibitor binding on the conformational dynamics of P-gp. Distinct differences in conformational changes that mainly occurred in the nucleotide-binding domains (NBDs) were observed from the substrate- and inhibitor-bound simulations. The binding of rhodamine-123 can increase the probability of the formation of an intermediate conformation, in which the NBDs were closer and better aligned, suggesting that substrate binding may prime the transporter for ATP hydrolysis. By contrast, the inhibitor QZ-Leu stabilized NBDs in a much more separated and misaligned conformation, which may result in the deficiency of ATP hydrolysis. The significant differences in conformational modulation of P-gp by substrate and inhibitor binding provided a molecular explanation of how these small molecules exert opposite effects on the ATPase activity. A further structural analysis suggested that the allosteric communication between transmembrane domains (TMDs) and NBDs was primarily mediated by two intracellular coupling helices. Our computational simulations provide not only valuable insights into the transport mechanism of P-gp substrates, but also for the molecular design of P-gp inhibitors. 相似文献
967.
Ruixue Chen Hai‐Yan Su Deyu Liu Rui Huang Xianguang Meng Xiaoju Cui Zhong‐Qun Tian Dong H. Zhang Dehui Deng 《Angewandte Chemie (International ed. in English)》2020,59(1):154-160
Conversion of carbon monoxide to high value‐added ethylene with high selectivity by traditional syngas conversion process is challenging because of the limitation of Anderson‐Schulz–Flory distribution. Herein we report a direct electrocatalytic process for highly selective ethylene production from CO reduction with water over Cu catalysts at room temperature and ambient pressure. An unprecedented 52.7 % Faradaic efficiency of ethylene formation is achieved through optimization of cathode structure to facilitate CO diffusion at the surface of the electrode and Cu catalysts to enhance the C?C bond coupling. The highly selective ethylene production is almost without other carbon‐based byproducts (e.g. C1–C4 hydrocarbons and CO2) and avoids the drawbacks of the traditional Fischer–Tropsch process that always delivers undesired products. This study provides a new and promising strategy for highly selective production of ethylene from the abundant industrial CO. 相似文献
968.
Yunyu Sun Mingcheng Yang Yutong Guo Mengjiao Cheng Bin Dong Feng Shi 《Angewandte Chemie (International ed. in English)》2020,59(3):1098-1102
Light‐driven micropumps, which are based on electro‐osmosis with the electric field generated by photocatalytic reactions, are among most attractive research topics in chemical micromotors. Until now, research in this field has mainly been focused on the directional motion or collective behavior of microparticles, which lack practical applications. In this study, we have developed a photowelding strategy for repeated photoinduced conductivity recovery of cracked flexible circuits. We immersed the circuit in a suspension of conductive healing particles and applied photoillumination to the crack; photocatalysis of a predeposited pentacene (PEN) layer triggered electro‐osmotic effects to gather conductive particles at the crack, thus leading to conductivity recovery of the circuit. This photowelding strategy is a novel application of light‐driven micropumps and photocatalysis for conductivity restoration. 相似文献
969.
Lingmei Liu Ning Wang Chongzhi Zhu Xiaona Liu Yihan Zhu Peng Guo Lujain Alfilfil Xinglong Dong Daliang Zhang Yu Han 《Angewandte Chemie (International ed. in English)》2020,59(2):819-825
Integrated differential phase‐contrast scanning transmission electron microscopy (iDPC‐STEM) is capable of directly probing guest molecules in zeolites, owing to its sufficient and interpretable image contrast for both heavy and light elements under low‐dose conditions. This unique ability is demonstrated by imaging volatile organic compounds adsorbed in zeolite Silicalite‐1; iDPC‐STEM was then used to investigate molybdenum supported on various zeolites including Silicalite‐1, ZSM‐5, and mordenite. Isolated single‐Mo clusters were observed in the micropores of ZSM‐5, demonstrating the crucial role of framework Al in driving Mo atomically dispersed into the micropores. Importantly, the specific one‐to‐one Mo‐Al interaction makes it possible to locate Al atoms, that is, catalytic active sites, in the ZSM‐5 framework from the images, according to the positions of Mo atoms in the micropores. 相似文献
970.
Ajmal Khan Heng Zhao Meina Zhang Shahid Khan Depeng Zhao 《Angewandte Chemie (International ed. in English)》2020,59(3):1340-1345
Chiral sulfones are of great importance in medicinal chemistry and chemical synthesis. Efficient methods for preparing enantiomerically enriched sulfone‐containing molecules can therefore be of significant value; such methods, however, are uncommon. Herein, we report the first general palladium‐catalyzed sulfonylation of vinyl cyclic carbonates with sodium sulfinates. A series of enantiomerically enriched tertiary allylic sulfones were synthesized in good yields with excellent enantiomeric ratios. Both aliphatic‐ and aryl‐substituted vinyl cyclic carbonates are suitable reactants with excellent results. This reaction features broad substrates scope, readily available starting materials, excellent regio‐ and enantioselectivity, and synthesis of sulfone‐bearing quaternary carbon stereocenters. Through the sulfonylation of geranyl derived cyclic carbonate 1 h , we achieve the formal total synthesis of (+)‐agelasidine A. 相似文献