全文获取类型
收费全文 | 597篇 |
免费 | 81篇 |
国内免费 | 65篇 |
专业分类
化学 | 564篇 |
晶体学 | 6篇 |
力学 | 1篇 |
物理学 | 172篇 |
出版年
2024年 | 1篇 |
2023年 | 7篇 |
2022年 | 17篇 |
2021年 | 31篇 |
2020年 | 61篇 |
2019年 | 39篇 |
2018年 | 21篇 |
2017年 | 15篇 |
2016年 | 31篇 |
2015年 | 21篇 |
2014年 | 29篇 |
2013年 | 46篇 |
2012年 | 35篇 |
2011年 | 29篇 |
2010年 | 24篇 |
2009年 | 13篇 |
2008年 | 37篇 |
2007年 | 43篇 |
2006年 | 20篇 |
2005年 | 23篇 |
2004年 | 18篇 |
2003年 | 28篇 |
2002年 | 25篇 |
2001年 | 17篇 |
2000年 | 12篇 |
1999年 | 16篇 |
1998年 | 16篇 |
1997年 | 15篇 |
1996年 | 6篇 |
1995年 | 6篇 |
1994年 | 4篇 |
1993年 | 6篇 |
1992年 | 6篇 |
1991年 | 6篇 |
1990年 | 6篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1976年 | 1篇 |
排序方式: 共有743条查询结果,搜索用时 31 毫秒
21.
Shi-Rong Hu Jia-Ming Liu Tian-Long Yang Hai-Zhu Liu Jun-Li Huang Qing-Wei Lin Guo-Hui Zhu Xiao-Mei Huang 《Mikrochimica acta》2005,152(1-2):53-59
Luminescent nanoparticles of silicon dioxide (SiO2) containing fluorescein isothiocyanate (FITC) with a particle size of 20 nm were synthesized using the Sol–Gel method (abbreviated
FITC–SiO2). FITC–SiO2 nanoparticles whose surfaces are modified (FITC–SiO2–S–CH2COOH) can emit strong and stable solid substrate room temperature phosphorescence (SS-RTP) on acetyl cellulose membranes.
When the original color-producing agent (R) in the enzyme-linked immunosorbent assay (ELISA) kits for determination of alpha-fetoprotein
(AFP) was substituted with (FITC–SiO2–S–CH2COOH), the system maintained good FITC–SiO2 phosphorescence properties. Furthermore, the phosphorescence intensity enhanced markedly after the ELISA reaction. The relationship
between the phosphorescence intensity and the content of AFP obeyed Beer’s law. Based on the facts stated above, a new method
for the determination of human AFP by SS-RTP-ELISA (using the luminescent nanoparticle as marker) was established. The linear
range of this method is 0.040–16.0 pg of human AFP per spot (sample volume: 0.40 μL spot−1, corresponding concentration: 0.10–40.0 ng mL−1). The regression equation of the working curve is ΔIp = −6.289+18.075 mAFP (pg spot−1) (r = 0.9960, n = 6). The detection limit (LD) of this method calculated by 3 Sb/k is 6.7 fg spot−1 (corresponding concentration: 17 ng L−1). Compared to the ELISA method using a traditional color-producing agent, the new method exhibited a 34.8 times higher sensitivity
and a wider linear range. The method has been successfully applied to the determination of human AFP in serum. 相似文献
22.
Blanca San Vicente de la RivaJosé M. Costa-Fernández Wei Jun JinRosario Pereiro Alfredo Sanz-Medel 《Analytica chimica acta》2002,455(2):179-186
A novel method has been developed for the sensitive determination of mercury in aqueous media by room temperature phosphorescence (RTP). The measurement principle is based on the energy transfer (ET) from a phosphor molecule (acting as a donor) to a Hg-sensitive dye (acceptor). To our acknowledgment this is the first RTP method for mercury measurement developed so far. α-Bromonaphthalene (BrN) was selected as the phosphorescent donor molecule (BrN can produce significant RTP emission in aqueous media in a β-cyclodextrin rigid microenvironment without deoxygenation).The absorption spectrum of the complex formed between mercury and the dithizone dye possesses a desirable spectral overlap with the RTP emission spectrum of the donor (BrN), giving rise to a nonradiative ET from the phosphor molecules to the mercury complex. An increase in the concentration of Hg(II) causes an increase on the concentration of the dithizone complex (acceptor) with the subsequent increase of the absorbance and, therefore, resulting in a decrease of the RTP emission. Both, RTP intensities and triplet lifetimes of the BrN decreased with increases on the Hg(II) concentration.Possible interferences present in natural waters, including different cations and anions, which could affect the analytical response, were evaluated and the analytical performance characteristics investigated. The use of phosphorescence measurements (low background noise signals) resulted in an improvement on the sensitivity of the Hg(II) detection higher than five times as compared to the molecular absorption spectrophotometric method for Hg(II) detection based on dithizone as Hg-indicator. A detection limit (D.L.) of 14 ng ml−1 of Hg(II) was obtained by RTP with a precision of ±4.8% for five replicates of 300 ng ml−1 of Hg(II). The usefulness of the method was successfully evaluated by the determination of Hg(II) in spiked natural water samples. 相似文献
23.
24.
Liu JM Hu SR He XM Li XL Zhan FP Zeng LQ Li LD Zhu GH Huang XM 《Analytical and bioanalytical chemistry》2005,382(7):1507-1512
Silicon dioxide nano-particles, diameter 50 nm, containing morin (morin–SiO2) have been synthesized by the sol–gel method. They emit strong and stable room-temperature phosphorescence (SS-RTP) on filter paper as substrate, and bismuth can quench the intensity of the SS-RTP. On this basis a new morin–SiO2 solid-substrate room-temperature phosphorescence-quenching method has been established for determination of traces of bismuth. Reduction of phosphorescence intensity (Ip) is directly proportional to the concentration of bismuth in the working range 0.16–14.4 ag spot–1 (sample volume 0.40 L spot–1, corresponding to the concentration range 0.40–36.0 fg mL–1). The regression equation of the working curve is Ip=14.86+5.279×[Bi3+] (ag spot–1) (n=6, r=0.9982). The detection limit of this method is 0.026 ag spot–1 (corresponding to a concentration of 6.5×10–17 g mL–1).This sensitive, reproducible and accurate method has been used for successful analysis of real samples. 相似文献
25.
A Phosphorescent Platinum(II) Bipyridyl Supramolecular Polymer Based on Quadruple Hydrogen Bonds 下载免费PDF全文
Fang‐Wei Liu Dr. Li‐Ya Niu Prof. Yong Chen Prof. Vaidhyanathan Ramamurthy Prof. Li‐Zhu Wu Prof. Chen‐Ho Tung Prof. Yu‐Zhe Chen Prof. Qing‐Zheng Yang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(50):18132-18139
A platinum(II) bipyridyl complex bearing bis‐ureidopyrimidinone (Pt‐bisUPy) has been designed and its self‐assembling behavior has been thoroughly investigated by 1H NMR, DOSY NMR, Ubbelohde viscometry analysis, UV/Vis, and emission spectroscopies. Pt‐bisUPy underwent concentration‐dependent ring‐chain polymerization in apolar solvents. Hydrogen‐bonding interactions play an important role during the formation of the supramolecular polymers. Hydrogen‐bonded supramolecular polymers were transformed to nanoparticles in water through the miniemulsion method. These nanoparticles showed strong π–π excimeric emission. Metal‐metal‐to‐ligand charge transfer (MMLCT) from Pt–Pt interactions was not significant in the emission spectrum. The phosphorescence of the nanoparticle persisted even under aerobic conditions. The triplet state of these phosphorescent nanomaterials were long‐lived and possessed moderate emission quantum yields. Furthermore, the low toxicity of these materials promises a place for them in in vitro and in vivo bioimaging. 相似文献
26.
Due to the anisotropy of the conductivity in AsF5-intercalated HOPG, eddy current methods have to be used for the measurement of transport effects. The measurements yield carrier concentration, mobility and charge transfer for C8nAsF5 with n=l-4 at temperatures between 4.2K and 300K. 相似文献
27.
Prof. Hisahiro Sasabe Prof. Yuki Kato Dr. Yuichiro Watanabe Tatsuya Ohsawa Dr. Naoya Aizawa Prof. Wataru Fujiwara Dr. Yong-Jin Pu Prof. Hiroshi Katagiri Prof. Junji Kido 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(71):16294-16300
Exploration of pure metal-free organic molecules that exhibit strong room-temperature phosphorescence (RTP) is an emerging research topic. In this regard, unveiling the design principles for an efficient RTP molecule is an essential, but challenging, task. A small molecule is an ideal platform to precisely understand the fundamental role of each functional component because the parent molecule can be easily derivatized. Here, the RTP behaviors of a series of 3-pyridylcarbazole derivatives are presented. Experimental studies in combination with theoretical calculations reveal the crucial role of the n orbital on the central pyridine ring in the dramatic enhancement of the intersystem crossing between the charge-transfer-excited singlet state and the locally excited triplet states. Single-crystal X-ray crystallographic studies apparently indicate that both the pyridine ring and fluorine atom contribute to the enhancement of the RTP because of the restricted motion owing to weak C−H⋅⋅⋅N and H⋅⋅⋅F hydrogen-bonding interactions. The single crystal of the fluorine-substituted derivative shows an ultra-long phosphorescent lifetime (τP) of 1.1 s and a phosphorescence quantum yield (ΦP) of 1.2 %, whereas the bromine-substituted derivative exhibits τP of 0.15 s with a ΦP of 7.9 %. We believe that this work provides a fundamental and universal guideline for the generation of pure organic molecules exhibiting strong RTP. 相似文献
28.
Lili Huang Chen Qian Prof. Zhiyong Ma 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(52):11914-11930
This Minireview summarizes the recent progress of stimuli-responsive purely organic phosphorescence materials. Organic phosphorescence is closely related to the intermolecular interactions, because such interactions are beneficial to promote spin orbital coupling (SOC) and boost intersystem cross (ISC) efficiency and finally are conducive to satisfactory phosphorescence. It is found that the intermolecular interactions, which are essential for organic phosphorescence, are easily disturbed by external stimuli such as mechanical force, photon, acid, chemical vapor, leading to the luminescence change. According to this principle, various purely organic phosphorescence materials sensitive to external stimuli have been developed. This Minireview categorizes reported stimuli-responsive purely organic phosphorescence materials on the basis of different stimuli, including mechanochromism, mechanoluminescence, photoactivity, acid-responsiveness and other stimuli. Some prospective strategies for constructing stimuli-responsive purely organic phosphorescence molecules are provided. 相似文献
29.
Yu Zhang Dr. Novruz G. Akhmedov Prof. Jeffrey L. Petersen Prof. Carsten Milsmann 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(12):3042-3052
Luminescent seven-coordinated zirconium and hafnium complexes bearing three mono-anionic 2,2′-pyridylpyrrolide ligands and one chloride were synthesized. Solid-state structures and the dynamic behaviors in solution were probed by X-ray crystallography and variable temperature 1H NMR experiments, respectively. Absorption spectroscopy and time-dependent density functional theory (TD-DFT) calculations supported a hybrid of ligand-to-metal charge transfer (LMCT)/ligand-to-ligand charge transfer (LLCT) for the visible light absorption band. The complexes (MePMPMe)3MCl (M=Zr, Hf, MePMPMe=3,5-dimethyl-2-(2-pyridyl)pyrrolide) are emissive in solution at room temperature upon irradiation with visible light due to a combination of phosphorescence and fluorescence characterized by excited state lifetimes in the μs and low to sub-ns timescale, respectively. Electrochemical experiments revealed that the zirconium complex possesses a reversible redox event under highly reducing condition (−2.29 V vs. Fc+/0). 相似文献
30.
Taisiya S. Sukhikh Radmir M. Khisamov Sergey N. Konchenko 《Molecules (Basel, Switzerland)》2021,26(7)
We report a study of photoluminescent properties of 4-bromo-7-(3-pyridylamino)-2,1,3-benzothiadiazole (Py-btd) and its novel Lewis adducts: (PyH-btd)2(ZnCl4) and [Cu2Cl2(Py-btd)2{PPO}2]·2C7H8 (PPO = tetraphenyldiphosphine monoxide), whose crystal structure was determined by X-ray diffraction analysis. Py-btd exhibits a lifetime of 9 microseconds indicating its phosphorescent nature, which is rare for purely organic compounds. This phenomenon arises from the heavy atom effect: the presence of a bromine atom in Py-btd promotes mixing of the singlet and triplet states to allow efficient singlet-to-triplet intersystem crossing. The Lewis adducts also feature a microsecond lifetime while emitting in a higher energy range than free Py-btd, which opens up the possibility to color-tune luminescence of benzothiadiazole derivatives. 相似文献