全文获取类型
| 收费全文 | 948篇 |
| 免费 | 62篇 |
| 国内免费 | 128篇 |
专业分类
| 化学 | 982篇 |
| 晶体学 | 8篇 |
| 力学 | 1篇 |
| 综合类 | 16篇 |
| 数学 | 10篇 |
| 物理学 | 121篇 |
出版年
| 2025年 | 2篇 |
| 2024年 | 5篇 |
| 2023年 | 16篇 |
| 2022年 | 57篇 |
| 2021年 | 67篇 |
| 2020年 | 59篇 |
| 2019年 | 52篇 |
| 2018年 | 28篇 |
| 2017年 | 34篇 |
| 2016年 | 58篇 |
| 2015年 | 37篇 |
| 2014年 | 42篇 |
| 2013年 | 61篇 |
| 2012年 | 91篇 |
| 2011年 | 42篇 |
| 2010年 | 32篇 |
| 2009年 | 37篇 |
| 2008年 | 49篇 |
| 2007年 | 32篇 |
| 2006年 | 34篇 |
| 2005年 | 40篇 |
| 2004年 | 43篇 |
| 2003年 | 24篇 |
| 2002年 | 32篇 |
| 2001年 | 26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 | 5篇 |
| 1993年 | 6篇 |
| 1992年 | 8篇 |
| 1991年 | 8篇 |
| 1990年 | 5篇 |
| 1989年 | 2篇 |
| 1988年 | 3篇 |
| 1987年 | 2篇 |
| 1986年 | 1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1138条查询结果，搜索用时 0 毫秒
41.
Zongbo Xie Hongxia Li Bo Wang Zhiwen Wu Zhanggao Le 《Journal of heterocyclic chemistry》2021,58(8):1588-1593
A method for introducing a biologically active heterocycle, 2-methylquinoline into the 4-position of a 2-amino-4H-1-benzopyran skeleton is described. Choline chloride/glucose (1:1 molar ratio) was used as both the solvent and catalyst in the reaction of a salicylaldehyde, methylquinoline, and cyanoacetate to obtain 2-amino-4H-1-benzopyran derivatives in 48%–80% yields after short reaction times. The effects of the deep eutectic solvent type, substrate molar ratio, cosolvent, temperature, and reaction time were examined. The method has the advantages of simple steps, environmental friendliness, mild conditions, and wide substrate applicability. This is the first attempt to synthesize methylquinoline derivatives of 4H-1-benzopyran. 相似文献
42.
Subhadip Chakraborty Rajib Saha Anupam Karmakar Sanatan Chattopadhyay 《Electroanalysis》2021,33(5):1185-1193
The present work deals with fabrication and characterization of the zinc oxide (ZnO) nanowire based novel two-electrode capacitive biosensors on flexible Polyethylene terephthalate (PET) substrates for accurate estimation of glucose by analyzing the fundamental dielectric nature of the relevant sample. The morphology and crystalline quality of grown nanowires are analyzed by using field-emission scanning electron microscope (FESEM) and X-ray diffractometer (XRD), respectively. Current and capacitance values of the device have been studied for ten different glucose concentrations relevant to the physiological standards. The analytical performance of the devices in terms of enzyme activity, reliability and flexibility has also been evaluated. 相似文献
43.
Ding-kai WANG Wei ZHAO Ming-yu CUI Tian-tian GUO Shui-yuan FU Wei-gang LI 《Turkish Journal of Chemistry》2021,45(4):1133
A series of Zr(SO4)2/SiO2 solid acid catalysts with different Zr(SO4)2 loadings were prepared by water-soluble-impregnation method at room temperature. Then, the prepared catalysts were characterized by Fourier transform infrared spectroscopy, transmission electron microscopy and energy-dispersive X-ray spectrum, X-ray diffraction, adsorption/desorption of N2, and temperature-programmed desorption of NH3. The results showed that the active component Zr(SO4)2 was successfully adhered to the mesoporous SiO2, and the acid amount of Zr(SO4)2/SiO2 increased with the increasing of the Zr(SO4)2 loadings. Finally, the wheat stalk was used as raw material and depolymerized over Zr(SO4)2/SiO2 to produce ethyl levulinate (EL). The reaction mixture was separated and purified by filtration and vacuum distillation. The kinetic characteristics and the reaction pathway were also studied. A comparative study showed that 20 wt.% Zr(SO4)2/SiO2 exhibited higher catalytic activity. When reaction temperature, time, catalyst dosage and Zr(SO4)2 loadings were 190 °C, 50 min, 20 wt.% and 30 wt.%, the EL yield reached a maximum of 17.14%. The relative content of EL exceeded 90% after three steps of distillation. 相似文献
44.
Dr. Karin Mannerstedt Dr. Narendra Kumar Mishra Dr. Ebbe Engholm Dr. Morten Lundh Dr. Charlotte S. Madsen Dr. Philip J. Pedersen Dr. Priska Le-Huu Dr. Søren L. Pedersen Dr. Nina Buch-Månson Dr. Björn Borgström Dr. Thomas Brimert Dr. Lisbeth N. Fink Dr. Keld Fosgerau Prof. Niels Vrang Prof. Knud J. Jensen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(9):3166-3176
A glucose responsive insulin (GRI) that responds to changes in blood glucose concentrations has remained an elusive goal. Here we describe the development of glucose cleavable linkers based on hydrazone and thiazolidine structures. We developed linkers with low levels of spontaneous hydrolysis but increased level of hydrolysis with rising concentrations of glucose, which demonstrated their glucose responsiveness in vitro. Lipidated hydrazones and thiazolidines were conjugated to the LysB29 side-chain of HI by pH-controlled acylations providing GRIs with glucose responsiveness confirmed in vitro for thiazolidines. Clamp studies showed increased glucose infusion at hyperglycemic conditions for one GRI indicative of a true glucose response. The glucose responsive cleavable linker in these GRIs allow changes in glucose levels to drive the release of active insulin from a circulating depot. We have demonstrated an unprecedented, chemically responsive linker concept for biopharmaceuticals. 相似文献
45.
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
46.
Nhung Quynh Do Shengdao Zheng Bom Park Quynh T. N. Nguyen Bo-Ram Choi Minzhe Fang Minseon Kim Jeehaeng Jeong Junhui Choi Su-Jin Yang Tae-Hoo Yi 《Molecules (Basel, Switzerland)》2021,26(11)
Myrciaria dubia (HBK) McVaugh (camu-camu) belongs to the family Myrtaceae. Although camu-camu has received a great deal of attention for its potential pharmacological activities, there is little information on the anti-oxidative stress and anti-inflammatory effects of camu-camu fruit in skin diseases. In the present study, we investigated the preventative effect of 70% ethanol camu-camu fruit extract against high glucose-induced human keratinocytes. High glucose-induced overproduction of reactive oxygen species (ROS) was inhibited by camu-camu fruit treatment. In response to ROS reduction, camu-camu fruit modulated the mitogen-activated protein kinases (MAPK)/activator protein-1 (AP-1), nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), and nuclear factor of activated T cells (NFAT) signaling pathways related to inflammation by downregulating the expression of proinflammatory cytokines and chemokines. Furthermore, camu-camu fruit treatment activated the expression of nuclear factor E2-related factor 2 (Nrf2) and subsequently increased the NAD(P)H:quinone oxidoreductase1 (NQO1) expression to protect keratinocytes against high-glucose-induced oxidative stress. These results indicate that camu-camu fruit is a promising material for preventing oxidative stress and skin inflammation induced by high glucose level. 相似文献
47.
Shing-Hwa Liu Shih-An Feng Chen-Yuan Chiu Meng-Tsan Chiang 《Molecules (Basel, Switzerland)》2021,26(16)
This study was designed to investigate the influence of dietary chitosan feeding-duration on glucose and lipid metabolism in diabetic rats induced by streptozotocin and nicotinamide [a non-insulin-dependent diabetes mellitus (NIDDM) model]. Male Sprague-Dawley rats were used as experimental animals and divided into short-term (6 weeks) and long-term (11 weeks) feeding durations, and each duration contained five groups: (1) control, (2) control + 5% chitosan, (3) diabetes, (4) diabetes + 0.8 mg/kg rosiglitazone (a positive control), and (5) diabetes + 5% chitosan. Whether the chitosan feeding was for 6 or 11 weeks, the chitosan supplementation decreased blood glucose and lipids levels and liver lipid accumulation. However, chitosan supplementation decreased plasma tumor necrosis factor (TNF)-α, insulin levels, alanine aminotransferase (ALT) activity, insulin resistance (HOMA-IR), and adipose tissue lipoprotein lipase activity. Meanwhile, it increased plasma high-density lipoproteins (HDL)-cholesterol level, plasma angiopoietin-like-4 protein expression, and plasma triglyceride levels (at 11-week feeding duration only). Taken together, 11-week (long-term) chitosan feeding may help to ameliorate the glucose and lipid metabolism in a NIDDM diabetic rat model. 相似文献
48.
49.
50.