全文获取类型
收费全文 | 862篇 |
免费 | 66篇 |
国内免费 | 145篇 |
专业分类
化学 | 925篇 |
晶体学 | 5篇 |
力学 | 2篇 |
综合类 | 16篇 |
数学 | 16篇 |
物理学 | 109篇 |
出版年
2024年 | 1篇 |
2023年 | 14篇 |
2022年 | 44篇 |
2021年 | 69篇 |
2020年 | 46篇 |
2019年 | 42篇 |
2018年 | 25篇 |
2017年 | 33篇 |
2016年 | 54篇 |
2015年 | 38篇 |
2014年 | 40篇 |
2013年 | 57篇 |
2012年 | 87篇 |
2011年 | 39篇 |
2010年 | 31篇 |
2009年 | 36篇 |
2008年 | 49篇 |
2007年 | 31篇 |
2006年 | 34篇 |
2005年 | 37篇 |
2004年 | 43篇 |
2003年 | 24篇 |
2002年 | 34篇 |
2001年 | 25篇 |
2000年 | 14篇 |
1999年 | 9篇 |
1998年 | 21篇 |
1997年 | 12篇 |
1996年 | 12篇 |
1995年 | 10篇 |
1994年 | 4篇 |
1993年 | 6篇 |
1992年 | 8篇 |
1991年 | 8篇 |
1990年 | 5篇 |
1989年 | 2篇 |
1988年 | 4篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1985年 | 6篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1982年 | 5篇 |
1981年 | 2篇 |
1978年 | 2篇 |
1976年 | 2篇 |
排序方式: 共有1073条查询结果,搜索用时 218 毫秒
121.
K. R. Sun M. W. Jang H. C. Park H. M. Jeong K. S. Yoon B. K. Kim 《Journal of Macromolecular Science: Physics》2013,52(4):795-805
The a-D-glucose was chemically modified with an allyl isocyanate (MG) and introduced into the polymer matrix for holographic polymer-dispersed liquid crystal (HPDLC), and the effects were studied in terms of morphology, grating formulation dynamics and electro-optical and biodegradable properties. Phase separation and diffraction efficiency increased at low content of (MG ≤ 4 wt%), while a rapid increase in crosslink density entrapped the LC droplets within the polymer to give poor phase separation, small droplet size, and low diffraction efficiency at high content. The HPDLC film was driven only with the addition of MG due to the increased droplet size with a minimum driving voltage of 18 V at 6.0 wt% MG. With the addition and an increasing amount of MG, the biodegradation of the composite film in a buffer solution was significantly increased in proportion to its amount. 相似文献
122.
123.
A low-field nuclear magnetic resonance spectrometer for non-invasive monitoring of human finger blood glucose fluctuations was developed. Saline solution and blood serum samples with different glucose concentrations were first detected by the spectrometer and it has been found that there was a high-linear correlation between the glucose concentration and the transverse relaxation time. Then, the spectrometer was employed to noninvasively measure a finger from each of the several volunteers. The experiment results showed that the transverse relaxation time of the human finger increases with human blood glucose concentration. In conclusion, the human finger nuclear magnetic resonance spectrometer could be a potential tool to noninvasive monitoring of human body’s blood glucose fluctuations in the future. 相似文献
124.
Qing Wang Mingxing Fu Xiaojun Li Runfeng Huang Rainer E. Glaser Lili Zhao 《Journal of computational chemistry》2019,40(16):1599-1608
Density functional theory calculations were performed to understand the detailed reaction mechanism of aluminum alkoxy-catalyzed conversion of glucose to 5-hydroxymethylfurfural (HMF) using Al(OMe)3 as catalyst. Potential energy surfaces were studied for aggregates formed between the organic compounds and Al(OMe)3 and effects of the medium were considered via continuum solvent models. The reaction takes place via two stages: isomerization from glucose to fructose (stage I) and transformation of fructose to HMF (stage II). Stage II includes three successive dehydrations, which begins with a 1,2-elimination to form an enolate (i.e., B), continues with the formation of the acrolein moiety (i.e., D), and ends with the formation of the furan ring (i.e., HMF). All of these steps are facilitated by aluminum alkoxy catalysis. The highest barriers for stage I and stage II are 23.9 and 31.2 kcal/mol, respectively, and the overall catalytic reaction is highly exothermic. The energetic and geometric results indicate that the catalyzed reaction path has feasible kinetics and thermodynamics and is consistent with the experimental process under high temperature (i.e., 120 °C). Remarkably, the released water molecules in stage II act as the product, reactant, proton shuttle, as well as stabilizer in the conversion of fructose to HMF. The metal–ligand functionality of the Al(OMe)3 catalyst, which combines cooperative Lewis acid and Lewis base properties and thereby enables proton shuttling, plays a crucial role in the overall catalysis and is responsible for the high reactivity. © 2019 Wiley Periodicals, Inc. 相似文献
125.
The development of a simple directly wearable approach for the rapid, specific and sensitive determination of biomarkers is of great importance to a variety of biomedical applications. Dental floss can provide a unique device platform for sensing of oral biomarkers. We show here for the first time the development of a smart dental floss for biosensing of glucose. The sensor was made by painting carbon graphite ink and Ag/AgCl ink on dental floss. Via the immobilization of glucose oxidase, we show the detection of glucose with a detection range of 0.048 mM to 19.5 mM and a response time of about 2 min. It is expected that our results could provide new exciting opportunities for the development of various flexible smart sensing devices in oral health applications. 相似文献
126.
Reactive oxygen species (ROS) forming enzymes are of significant interest as anticancer agents due to their potent cytotoxicity. A key challenge in their clinical translation is attaining site‐specific delivery and minimizing biodistribution to healthy tissues. Here, complexes composed of the ROS enzyme glucose oxidase (GOX), poly‐l ‐lysine‐grafted‐polyethylene glycol (PLL‐g‐PEG), and anti‐prostate specific membrane antigen (anti‐PSMA) monoclonal antibody are synthesized for localized delivery and uptake in prostate cancer cells. Formation of anti‐PSMA‐PLL‐g‐PEG/GOX results in nanoscale complexes ≈30 nm in diameter with a ζ‐potential of 6 mV. The anti‐PSMA‐PLL‐g‐PEG/GOX complexes show significant cytotoxicity (≈60% reduction in cell viability) against PSMA‐expressing LNCaP cells compared to unmodified GOX. Importantly, cytotoxicity in LNCaP cells occurrs concurrently with anti‐PSMA‐PLL‐g‐PEG/GOX uptake and increases in intracellular generation of ROS. These results demonstrate that cytotoxicity of ROS inducing enzymes can be enhanced by intracellular delivery compared to equivalent concentrations of free enzyme, providing a novel means for cancer therapy. 相似文献
127.
Aim
To study the effect of long-term glucose feeding on aortic lipid composition by using the time of flight-secondary ion mass spectrometry (TOF-SIMS).Method
Rats were divided into two groups, drinking water with or without 10% glucose from birth to 6 months of age. The aortic wall was dissected out, high-pressure frozen, freeze-fractured, freeze-dried and analyzed by TOF-SIMS using a Bismuth cluster ion source. Surface spectra were taken from standardized regions of the vessel wall.Results
Different peaks, such as cholesterol, fatty acids (FAs) and diacylglycerols (DAGs), were identified by the principal component analysis as carries of variance between two groups. These peaks were then compared by conventional t-test. Our data showed that the intensity of cholesterol, but not FAs and DAGs, was significantly decreased in the glucose-drinking rat. Moreover, the long-term glucose intake changed ratios between different FAs in the aorta.Conclusion
The long-term glucose intake led to decreased cholesterol intensity in the aortic wall and this effect was revealed through a global analytical approach with objective selection of significant variables. 相似文献128.
Dr. Sampa Maiti Dr. Saikat Manna Nicholas Banahene Lucynda Pham Zhijie Liang Jun Wang Yi Xu Reuben Bettinger John Zientko Prof. Dr. Aaron P. Esser-Kahn Prof. Dr. Wenjun Du 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(43):19105-19109
Efforts to synthesize degradable polymers from renewable resources are deterred by technical and economic challenges; especially, the conversion of natural building blocks into polymerizable monomers is inefficient, requiring multistep synthesis and chromatographic purification. Herein we report a chemoenzymatic process to address these challenges. An enzymatic reaction system was designed that allows for regioselective functional group transformation, efficiently converting glucose into a polymerizable monomer in quantitative yield, thus removing the need for chromatographic purification. With this key success, we further designed a continuous, three-step process, which enabled the synthesis of a sugar polymer, sugar poly(orthoester), directly from glucose in high yield (73 % from glucose). This work may provide a proof-of-concept in developing technically and economically viable approaches to address the many issues associated with current petroleum-based polymers. 相似文献
129.
Amira Mahmoud Mosaab Echabaane Karim Omri Julien Boudon Lucien Saviot Nadine Millot Rafik Ben Chaabane 《Molecules (Basel, Switzerland)》2021,26(4)
Copper-doped zinc oxide nanoparticles (NPs) CuxZn1−xO (x = 0, 0.01, 0.02, 0.03, and 0.04) were synthesized via a sol-gel process and used as an active electrode material to fabricate a non-enzymatic electrochemical sensor for the detection of glucose. Their structure, composition, and chemical properties were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier-transform infrared (FTIR) and Raman spectroscopies, and zeta potential measurements. The electrochemical characterization of the sensors was studied using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and differential pulse voltammetry (DPV). Cu doping was shown to improve the electrocatalytic activity for the oxidation of glucose, which resulted from the accelerated electron transfer and greatly improved electrochemical conductivity. The experimental conditions for the detection of glucose were optimized: a linear dependence between the glucose concentration and current intensity was established in the range from 1 nM to 100 μM with a limit of detection of 0.7 nM. The proposed sensor exhibited high selectivity for glucose in the presence of various interfering species. The developed sensor was also successfully tested for the detection of glucose in human serum samples. 相似文献
130.
This paper studies the ranking problem in the context of the regularization theory that allows a simultaneous analysis of a wide class of ranking algorithms. Some of them were previously studied separately. For such ones, our analysis gives a better convergence rate compared to the reported in the literature. We also supplement our theoretical results with numerical illustrations and discuss the application of ranking to the problem of estimating the risk from errors in blood glucose measurements of diabetic patients. 相似文献