全文获取类型
收费全文 | 5018篇 |
免费 | 283篇 |
国内免费 | 108篇 |
专业分类
化学 | 2770篇 |
晶体学 | 62篇 |
力学 | 206篇 |
综合类 | 6篇 |
数学 | 837篇 |
物理学 | 762篇 |
无线电 | 766篇 |
出版年
2024年 | 13篇 |
2023年 | 94篇 |
2022年 | 149篇 |
2021年 | 188篇 |
2020年 | 195篇 |
2019年 | 168篇 |
2018年 | 198篇 |
2017年 | 135篇 |
2016年 | 228篇 |
2015年 | 163篇 |
2014年 | 216篇 |
2013年 | 412篇 |
2012年 | 334篇 |
2011年 | 373篇 |
2010年 | 235篇 |
2009年 | 228篇 |
2008年 | 305篇 |
2007年 | 261篇 |
2006年 | 237篇 |
2005年 | 216篇 |
2004年 | 180篇 |
2003年 | 155篇 |
2002年 | 145篇 |
2001年 | 91篇 |
2000年 | 53篇 |
1999年 | 55篇 |
1998年 | 43篇 |
1997年 | 42篇 |
1996年 | 27篇 |
1995年 | 30篇 |
1994年 | 27篇 |
1993年 | 22篇 |
1992年 | 12篇 |
1991年 | 11篇 |
1990年 | 10篇 |
1989年 | 8篇 |
1988年 | 8篇 |
1987年 | 11篇 |
1986年 | 14篇 |
1985年 | 13篇 |
1984年 | 17篇 |
1983年 | 17篇 |
1982年 | 11篇 |
1981年 | 14篇 |
1980年 | 6篇 |
1979年 | 7篇 |
1977年 | 4篇 |
1976年 | 3篇 |
1975年 | 5篇 |
1973年 | 5篇 |
排序方式: 共有5409条查询结果,搜索用时 15 毫秒
71.
YANG Liming GUO Lixin YU Hao WANG Guan SUN Jiangman ZHANG Pengfei GU Xinggui TANG Ben Zhong 《高等学校化学研究》2021,37(1):129-136
The development of fluorescent nanocrystals based on organic small molecules is of great importance in bioimaging due to the merits of easy modification,high brightness and excellent photostability,however suffering from the emission-detrimental aggregation-caused quenching(ACQ)effect.Herein,we successfully designed and synthesized an AIE-active di(N,N-dimethylaniline)-dibenzofulvene(named as NFTPE),which exhibits the crystallization-induced emission enhancement(CIEE)effect.Interestingly,two types of yellow-and orange-emissive crystals for NFTPE were obtained,exhibiting aggregation microenvironment-dependent emission tuning in the solid state.Single-crystal analysis and density functional theory(DFT)calculations reveal that different aggregation microenvironments result in the distinct molecular conformation for various emission.Excitingly,the crystallization of NFTPE in an aqueous solution under the assistance of amphiphilic PEG polymer matrices could be monitored in situ by the fluorescence changes,facilitating the preparation of NFTPE nanocrystals(NFTPE-NCs)by adjusting the aggregation microenvironment.The obtained NFTPE-NCs exhibit the superior performance in cell imaging in respect to high brightness,photostability,and biocompatibility,thus demonstrating the potential in bioimaging applications. 相似文献
72.
PAN Quan MA Feiyan PU Xinqing ZHAO Manyi WU Qiling ZHAO Na YANG Jun TANG Ben Zhong 《高等学校化学研究》2021,37(1):166-170
In this work,a fluorescent probe(TPEBe-I)was developed for adenosine triphosphate(ATP)detection based on the synergetic effect of aggregation-induced emission and counterion displacement.TPEBe-I gave weak emission in aqueous solution due to the heavy-atom effect of counter iodide ion.However,upon the addition of ATP,the new aggregate complex(TPEBe-ATP)was formed between the cationic unit of TPEBe-I and ATP through electrostatic interactions,which not only restricted the intramolecular motion of luminogen but also eliminated the quenching effect of iodide ion.As a result,the fluorescent light-up detection for ATP was successfully achieved.Moreover,TPEBe-I exhibited high selectivity towards ATP and showed a wide linear detection region towards the logarithm of ATP concentration(5—600μmol/L)with a detection limit of 1.0μmol/L,enabling TPEBe-I as a promising probe for ATP quantitative analysis. 相似文献
73.
Wenxuan Jiang Wei Wei Tinglian Yuan Shasha Liu Ben Niu Hui Wang Wei Wang 《Chemical science》2021,12(24):8556
The inevitable microstructural defects, including cracks, grain boundaries and cavities, make a portion of the material inaccessible to electrons and ions, becoming the incentives for electrochemically inactive zones in single entity. Herein, we introduced dark field microscopy to study the variation of scattering spectrum and optical mass centroid (OMC) of single Prussian blue nanoparticles during electrochemical reaction. The “dark zone” embedded in a single electroactive nanoparticle resulted in the incomplete reaction, and consequently led to the misalignment of OMC for different electrochemical intermediate states. We further revealed the dark zones such as lattice defects in the same entity, which were externally manifested as the fixed pathway for OMC for the migration of potassium ions. This method opens up enormous potentiality to optically access the heterogeneous intraparticle dark zones, with implications for evaluating the crystallinity and electrochemical recyclability of single electroactive nano-objects.The schematic of single cubic-shaped Prussian blue (PB) mesocrystals formed by the oriented aggregation of small nanocrystals. The dark-field images of single PB nanoparticle at PB and Prussian white (PW) states, respectively. 相似文献
74.
Khaled D. Khalil Sayed M. Riyadh Mariusz Jaremko Thoraya A. Farghaly Mohamed Hagar 《Molecules (Basel, Switzerland)》2021,26(12)
Recently, the development of nanocatalysts based on naturally occurring polysaccharides has received a lot of attention. Chitosan (CS), as a biodegradable and biocompatible polysaccharide, is considered to be an excellent template for the design of a hybrid biopolymer-based metal oxide nanocomposite. In this case, lanthanum oxide nanoparticles doped with chitosan at different weight percentages (5, 10, 15, and 20 wt% CS/La2O3) were prepared via a simple solution casting method. The prepared CS/La2O3 nanocomposite solutions were cast in a Petri dish in order to produce the developed catalyst, which was shaped as a thin film. The structural features of the hybrid nanocomposite film were studied by FTIR, SEM, and XRD analytical tools. FTIR spectra confirmed the presence of the major characteristic peaks of chitosan, which were modified by interaction with La2O3 nanoparticles. Additionally, SEM graphs showed dramatic morphological changes on the surface of chitosan, which is attributed to surface adsorption with La2O3 molecules. The prepared CS/La2O3 nanocomposite film (15% by weight) was investigated as an effective, recyclable, and heterogeneous base catalyst in the synthesis of pyridines and pyrazoles. The nanocomposite used was sufficiently stable and was collected and reused more than three times without loss of catalytic activity. 相似文献
75.
The ability to induce and amplify motion at the molecular scale has seen tremendous progress ranging from simple molecular rotors to responsive materials. In the two decades since the discovery of light-driven rotary molecular motors, the development of these molecules has been extensive; moving from the realm of molecular chemistry to integration into dynamic molecular systems. They have been identified as actuators holding great potential to precisely control the dynamics of nanoscale devices, but integrating molecular motors effectively into evermore complex artificial molecular machinery is not trivial. Maximising efficiency without compromising function requires conscious and judicious selection of the structures used. In this perspective, we focus on the key aspects of motor design and discuss how to manipulate these properties without impeding motor integrity. Herein, we describe these principles in the context of molecular rotary motors featuring a central double bond axle and emphasise the strengths and weaknesses of each design, providing a comprehensive evaluation of all artificial light-driven rotary motor scaffolds currently present in the literature. Based on this discussion, we will explore the trajectory of research into the field of molecular motors in the coming years, including challenges to be addressed, potential applications, and future prospects.Various families of light-driven rotary molecular motors and the key aspects of motor design are discussed. Comparisons are made between the strengths and weaknesses of each motor. Challenges, applications, and future prospects are explored. 相似文献
76.
Zahraa Hammoud Maya Kayouka Adriana Trifan Elwira Sieniawska Jouda Mediouni Ben Jema Abdelhamid Elaissari Hlne Greige-Gerges 《Molecules (Basel, Switzerland)》2021,26(22)
The essential oil component α-pinene has multiple biological activities. However, its application is limited owing to its volatility, low aqueous solubility, and chemical instability. For the aim of improving its physicochemical properties, α-pinene was encapsulated in conventional liposomes (CLs) and drug-in-cyclodextrin-in-liposomes (DCLs). Hydroxypropyl-β-cyclodextrin/α-pinene (HP-β-CD/α-pinene) inclusion complexes were prepared in aqueous solution, and the optimal solubilization of α-pinene occurred at HP-β-CD:α-pinene molar ratio of 7.5:1. The ethanol-injection method was applied to produce different formulations using saturated (Phospholipon 90H) or unsaturated (Lipoid S100) phospholipids in combination with cholesterol. The size, the phospholipid and cholesterol incorporation rates, the encapsulation efficiency (EE), and the loading rate (LR) of α-pinene were determined, and the storage stability of liposomes was assessed. The results showed that α-pinene was efficiently entrapped in CLs and DCLs with high EE values. Moreover, Lipoid S100 CLs displayed the highest LR (22.9 ± 2.2%) of α-pinene compared to the other formulations. Both carrier systems HP-β-CD/α-pinene inclusion complex and Lipoid S100 CLs presented a gradual release of α-pinene. Furthermore, the DPPH radical scavenging activity of α-pinene was maintained upon encapsulation in Lipoid S100 CLs. Finally, it was found that all formulations were stable after three months of storage at 4 °C. 相似文献
77.
Ben L. M. Van Baar Peter C. Burgers John L. Holmes Johan K. Terlouw 《Journal of mass spectrometry : JMS》1988,23(5):355-363
By combining results from a variety of mass spectrometric techniques (metastatle ion, collisional activation, collision-induced dissociative ionization, neutralization–reionization spectrometry and appearance energy measurements) and the classical method of isotopic labelling, a unified mechanism is proposed for the complex unimolecular chemistry of ionized 1,2-propanediol. The key intermediates involved are the stable hydrogen-bridged radical cations [CH2?C(H)? H…?O…?O(H)CH3]+˙, which were generated independently from [4-methoxy, 1-butanol]+˙ (loss of C2H4) and [1-methoxyglycerol]+˙ (loss of CH2O), [CH3? C?O…?H…?O(H)CH3]+˙ and the related ion-dipole complex [CH2?C(OH)CH3/H2O]+˙. The latter species serves as the precursor for the loss of CH3˙ and in this reaction the same non-ergodic behaviour is observed as in the loss of CH3˙ from the ionized enol of acetone. 相似文献
78.
79.
80.