全文获取类型
收费全文 | 2849篇 |
免费 | 265篇 |
国内免费 | 196篇 |
专业分类
化学 | 2013篇 |
晶体学 | 35篇 |
力学 | 123篇 |
综合类 | 12篇 |
数学 | 378篇 |
物理学 | 749篇 |
出版年
2023年 | 47篇 |
2022年 | 88篇 |
2021年 | 88篇 |
2020年 | 106篇 |
2019年 | 114篇 |
2018年 | 106篇 |
2017年 | 72篇 |
2016年 | 121篇 |
2015年 | 114篇 |
2014年 | 136篇 |
2013年 | 195篇 |
2012年 | 231篇 |
2011年 | 231篇 |
2010年 | 154篇 |
2009年 | 125篇 |
2008年 | 162篇 |
2007年 | 147篇 |
2006年 | 140篇 |
2005年 | 133篇 |
2004年 | 81篇 |
2003年 | 64篇 |
2002年 | 83篇 |
2001年 | 52篇 |
2000年 | 42篇 |
1999年 | 35篇 |
1998年 | 34篇 |
1997年 | 32篇 |
1996年 | 34篇 |
1995年 | 34篇 |
1994年 | 25篇 |
1993年 | 23篇 |
1992年 | 35篇 |
1991年 | 18篇 |
1990年 | 28篇 |
1989年 | 17篇 |
1988年 | 21篇 |
1987年 | 17篇 |
1986年 | 9篇 |
1985年 | 18篇 |
1984年 | 17篇 |
1983年 | 12篇 |
1982年 | 13篇 |
1981年 | 9篇 |
1980年 | 5篇 |
1979年 | 6篇 |
1978年 | 7篇 |
1975年 | 6篇 |
1974年 | 3篇 |
1972年 | 3篇 |
1971年 | 3篇 |
排序方式: 共有3310条查询结果,搜索用时 15 毫秒
81.
Min Tu Helge Reinsch Sabina Rodríguez‐Hermida Rhea Verbeke Timothe Stassin Werner Egger Marcel Dickmann Bjorn Dieu Johan Hofkens Ivo F. J. Vankelecom Norbert Stock Rob Ameloot 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(8):2445-2449
Metal–organic frameworks (MOFs) enable the design of host–guest systems with specific properties. In this work, we show how the confinement of anthracene in a well‐chosen MOF host leads to reversible yellow‐to‐purple photoswitching of the fluorescence emission. This behavior has not been observed before for anthracene, either in pure form or adsorbed in other porous hosts. The photoresponse of the host–guest system is caused by the photodimerization of anthracene, which is greatly facilitated by the pore geometry, connectivity, and volume as well as the structural flexibility of the MOF host. The photoswitching behavior was used to fabricate photopatternable and erasable surfaces that, in combination with data encryption and decryption, hold promise in product authentication and secure communication applications. 相似文献
82.
Guangwu Li Taisuke Matsuno Yi Han Hoa Phan Shaofei Wu Qing Jiang Ya Zou Hiroyuki Isobe Jishan Wu 《Angewandte Chemie (International ed. in English)》2020,59(24):9727-9735
Synthesis of fully conjugated cyclophanes containing large‐size polycyclic aromatics is challenging. Now, three benzidine‐linked, hexa‐peri‐hexabenzocoronene (superbenzene)‐based ortho‐, para‐, and meta‐cyclophanes are synthesized through intermolecular Yamamoto coupling reaction of structurally pre‐organized precursors. Subsequent oxidative dehydrogenation gave the corresponding quinoidal benzidine‐linked cyclophanes. Their geometries were confirmed by X‐ray crystallographic analysis and their electronic properties were investigated by electronic absorption, cyclic voltammetry, and DFT calculations. The quinoidal benzidine‐linked cyclophanes show thermally populated paramagnetic activity with a relatively large singlet‐triplet energy gap. Two enantiomers for the ortho‐cyclophanes ( 1‐NH and 1‐N ) were isolated and their chiral figure‐of‐eight macrocyclic structures were identified. The cage‐like cyclophanes 2‐NH and 3‐NH with concave surface can selectively encapsulate fullerene C70. 相似文献
83.
Wang Q Zhu L Li G Tu C Pang Y Jin C Zhu B Zhu X Liu Y 《Macromolecular bioscience》2011,11(11):1553-1562
A novel type of drug carrier capable of controlled drug release is proposed. It consists of an acid-sensitive doubly hydrophilic multiarm hyperbranched copolymer with a hyperbranched polyamidoamine core and many linear poly(ethylene glycol) arms. Using pH-sensitive acylhydrazone linkages, the polymer forms unimolecular micelles that can encapsulate hydrophobic drugs. Due to their amphiphilicity, the drug-loaded unimolecular micelles can self-assemble into multimolecular micelles that show acid-triggered intracellular delivery of the hydrophobic drugs. 相似文献
84.
A facile one-pot synthesis of 5-(trifluoromethyl)-4,7-dihydrotetrazolo[1,5-a]pyrimidine derivatives is described via a three-component reaction of aldehydes with 5-aminotetrazole and ethyl 4,4,4-trifluoro-3-oxobutanoate or 4,4,4-trifluoro-1-phenylbutane-1,3-dione in ionic liquid. This method has the advantages of short synthetic route, operational simplicities, good yields, ecofriendliness, and recyclability of the solvent. 相似文献
85.
86.
纳米TiO2修饰的La0.6Sr0.4Co0.2Fe0.8O3-δ(LSCF)阴极被直接应用于YSZ电解质电池上. TiO2可阻止LSCF和YSZ间的化学反应,抑制SrZrO3的形成. LSCF-0.25 wt% TiO2阴极电池在0.7 V和600°C下的电流密度是LSCF阴极电池的1.6倍.电化学阻抗谱结果表明, TiO2修饰显著加快了氧离子注入电解质的过程,这可能与TiO2抑制了阴极/电解质界面处高电阻SrZrO3层的形成有关.本文为在ZrO2基电解质上使用高性能的(La,Sr)(Co,Fe)O3阴极材料提供了一种简单有效的方法. 相似文献
87.
Multifunctional Nano‐Bioprobes Based on Rattle‐Structured Upconverting Luminescent Nanoparticles 下载免费PDF全文
Dr. Shan Lu Dr. Datao Tu Ping Hu Jin Xu Renfu Li Dr. Meng Wang Dr. Zhuo Chen Prof. Mingdong Huang Prof. Dr. Xueyuan Chen 《Angewandte Chemie (International ed. in English)》2015,54(27):7915-7919
Lanthanide‐doped upconversion nanoparticles (UCNPs) have shown great promise in versatile bioapplications. For the first time, organosilica‐shelled β‐NaLuF4:Gd/Yb/Er nanoprobes with a rattle structure have been designed for dual‐modal imaging and photodynamic therapy (PDT). Benefiting from the unique rattle structure and aromatic framework, these nanoprobes are endowed with a high loading capacity and the disaggregation effect of photosensitizers. After loading of β‐carboxyphthalocyanine zinc or rose Bengal into the nanoprobes, we achieved higher energy transfer efficiency from UCNPs to photosensitizers as compared to those with conventional core–shell structure or with pure‐silica shell, which facilitates a large production of singlet oxygen and thus an enhanced PDT efficacy. We demonstrated the use of these nanoprobes in proof‐of‐concept X‐ray computed tomography (CT) and UC imaging, thus revealing the great potential of this multifunctional material as an excellent nanoplatform for cancer theranostics. 相似文献
88.
Serganov A Yuan YR Pikovskaya O Polonskaia A Malinina L Phan AT Hobartner C Micura R Breaker RR Patel DJ 《Chemistry & biology》2004,11(12):1729-1741
Metabolite-sensing mRNAs, or "riboswitches," specifically interact with small ligands and direct expression of the genes involved in their metabolism. Riboswitches contain sensing "aptamer" modules, capable of ligand-induced structural changes, and downstream regions, harboring expression-controlling elements. We report the crystal structures of the add A-riboswitch and xpt G-riboswitch aptamer modules that distinguish between bound adenine and guanine with exquisite specificity and modulate expression of two different sets of genes. The riboswitches form tuning fork-like architectures, in which the prongs are held in parallel through hairpin loop interactions, and the internal bubble zippers up to form the purine binding pocket. The bound purines are held by hydrogen bonding interactions involving conserved nucleotides along their entire periphery. Recognition specificity is associated with Watson-Crick pairing of the encapsulated adenine and guanine ligands with uridine and cytosine, respectively. 相似文献
89.
The oil industry has been facing the challenges of separation of xylene isomers, o-xylene, m-xylene and p-xylene or removing them from the environment. In our present work, we investigated the adsorption of the three isomers on
two mesoporous materials, FDU-15-350 polymer and FDU-15-900 carbon materials. The isomer adsorption capacities are well correlated
with their physical pore properties. It is found that the micropores are very crucial for the adsorption of these three isomers.
The more micropore volume the adsorbent has, the better the adsorption capacity is. Henry’s constants were also calculated
for the three isomers on the two adsorbents. Both on FDU-15-350 polymer and FDU-15-900, the Henry’s constants for the three
isomers show the same trend o>m>p xylene which is coincidently in accordance with their polarity trend, indicating more polar adsorbate is preferred for adsorption
on the two adsorbents. The isosteric heats of adsorption are correlated with the microporosity and the size of the adsorbate
molecule. More microporosity and smaller molecules give higher heats of adsorption. Extracted information on pore properties
of adsorbents by using the three isomers has very similar results as that resolved from nitrogen adsorption, indicating the
feasibility of using the three isomers as adsorbates to extract pore information.
This work is devoted to commemorating the 60th birthday of Professor Mieczyslaw (Mietek) Jaroniec. 相似文献
90.
Catalytic Asymmetric Construction of α‐Quaternary Cyclopentanones and Its Application to the Syntheses of (−)‐1,14‐Herbertenediol and (−)‐Aphanorphine 下载免费PDF全文
Dao‐Yong Zhu Ming‐Hui Xu Prof. Dr. Yong‐Qiang Tu Prof. Dr. Fu‐Min Zhang Prof. Dr. Shao‐Hua Wang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(44):15502-15505
A novel and efficient strategy to build α‐benzylic quaternary cyclopentanones with excellent enantioselectivities (up to 96 % ee) and high yields (up to 99 % yield) has been developed, and its application demonstrated by the first catalytic asymmetric total synthesis of (?)‐1,14‐herbertenediol and the formal synthesis of (?)‐aphanorphine. 相似文献