全文获取类型
收费全文 | 733篇 |
免费 | 244篇 |
国内免费 | 94篇 |
专业分类
化学 | 353篇 |
晶体学 | 21篇 |
力学 | 76篇 |
综合类 | 12篇 |
数学 | 172篇 |
物理学 | 437篇 |
出版年
2024年 | 5篇 |
2023年 | 12篇 |
2022年 | 32篇 |
2021年 | 42篇 |
2020年 | 31篇 |
2019年 | 31篇 |
2018年 | 35篇 |
2017年 | 35篇 |
2016年 | 66篇 |
2015年 | 30篇 |
2014年 | 49篇 |
2013年 | 90篇 |
2012年 | 61篇 |
2011年 | 64篇 |
2010年 | 43篇 |
2009年 | 40篇 |
2008年 | 40篇 |
2007年 | 57篇 |
2006年 | 37篇 |
2005年 | 29篇 |
2004年 | 34篇 |
2003年 | 19篇 |
2002年 | 25篇 |
2001年 | 17篇 |
2000年 | 30篇 |
1999年 | 12篇 |
1998年 | 13篇 |
1997年 | 23篇 |
1996年 | 5篇 |
1995年 | 4篇 |
1994年 | 8篇 |
1993年 | 5篇 |
1992年 | 9篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1988年 | 6篇 |
1987年 | 6篇 |
1986年 | 4篇 |
1985年 | 2篇 |
1984年 | 6篇 |
1982年 | 2篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1974年 | 1篇 |
排序方式: 共有1071条查询结果,搜索用时 390 毫秒
51.
Emilio Celotti Georgios Lazaridis Jakob Figelj Yuri Scutaru Andrea Natolino 《Molecules (Basel, Switzerland)》2022,27(1)
The oxidation processes of white wines can occur during storage and commercialization due to several factors, and these can negatively affect the color, aroma, and quality of the wine. Wineries should have faster and simpler methods that provide valuable information on oxidation stability of wines and allow fast decision-making procedures, able to trigger suitable technological interventions. Using a portable prototype instrument for light irradiations at different wavelengths and times was considered and evaluated on sensorial, spectrophotometric, and colorimetric parameters of white wines. The sensorial analysis revealed that white and light blue were the most significant, after only 1 h of irradiation. The experimental results showed that hydrogen peroxide could enhance the effect of light treatment, allowing a contemporary evaluation of the oxidation stability of wine against light and chemical stresses. As expected, a good correlation (R2 > 0.89) between optical density at 420 nm and b* parameter was highlighted. The synergic effect of light and H2O2 was also studied on the hydrolyzable and condensed tannins’ additions to white wine. The proposed methodology could be used to evaluate the oxidative stability of white wines, but also to evaluate the effect of some oenological adjuvants on wine stability. 相似文献
52.
53.
The Upper Semicontinuity of Random Attractors for Non-Autonomous Stochastic Plate Equations with Multiplicative Noise and Nonlinear Damping 下载免费PDF全文
Based on the existence of pullback attractors for the non-autonomous stochastic plate equations with multiplicative noise and nonlinear damping defined in the entire space $\mathbb{R}^n$ by Xiaobin Yao in \cite{Yao4}, in the paper, we further investigate the upper semicontinuity of pullback attractors for the problem. 相似文献
54.
Mustapha Muhammad Nasiru Muhammad Umair Evans Frimpong Boateng Fawze Alnadari Kashif-ur Rehman Khan Zhaobin Wang Ji Luo Wenjing Yan Hong Zhuang Ali Majrashi Jianhao Zhang Sameh A. Korma 《Molecules (Basel, Switzerland)》2022,27(3)
Egg white protein (EWP) is susceptible to denaturation and coagulation when exposed to high temperatures, adversely affecting its flavour, thereby influencing consumers’ decisions. Here, we employ high-voltage cold plasma (HVCP) as a novel nonthermal technique to investigate its influence on the EWP’s flavour attributes using E-nose, E-tongue, and headspace gas-chromatography-ion-mobilisation spectrometry (HS-GC-IMS) due to their rapidness and high sensitivity in identifying flavour fingerprints in foods. The EWP was investigated at 0, 60, 120, 180, 240, and 300 s of HVCP treatment time. The results revealed that HVCP significantly influences the odour and taste attributes of the EWP across all treatments, with a more significant influence at 60 and 120 s of HVCP treatment. Principal component analyses of the E-nose and E-tongue clearly distinguish the odour and taste sensors’ responses. The HS-GC-IMS analysis identified 65 volatile compounds across the treatments. The volatile compounds’ concentrations increased as the HVCP treatment time was increased from 0 to 300 s. The significant compounds contributing to EWP characterisation include heptanal, ethylbenzene, ethanol, acetic acid, nonanal, heptacosane, 5-octadecanal, decanal, p-xylene, and octanal. Thus, this study shows that HVCP could be utilised to modify and improve the EWP flavour attributes. 相似文献
55.
生晒参、全须生晒参中19种有机氯残留农药的毛细管气相色谱测定 总被引:2,自引:0,他引:2
建立了生晒参、全须生晒参中19种有机氯农药残留的毛细管气相色谱分析方法。对样品中六六六的4种异构体、滴滴涕的5种异构体、四氯苯胺、六氯苯、五氯硝基苯、七氯、五氯苯胺、艾氏剂、百菌清、环氧七氯、狄氏剂及异狄氏剂共19种有机氯农药的残留量进行了测定。以石油醚-丙酮混合物作为提取剂,样品采用索氏提取,提取液用弗罗里硅土柱层析净化。采用OV-1701石英毛细管气相色谱柱分离样品,ECD检测器进行检测。在3个水平添加时的回收率(n=5)分别为75.7%~96.1%、78.8%~111.6%和81.7%~115·2%;相对标准偏差分别为2.4%~10.6%、2.1%~9.8%和1.4~10.0%。方法用于生晒参和全须生晒参样品中农药残留的测定,结果满意。 相似文献
56.
ABSTRACTThis study was to investigate the piezotolerance and diversity indices of microflora of Indian white prawn (Fenneropenaeus indicus) after high pressure (HP)-treatment. Indian white prawns subjected to HP-treatments and its effect was studied up to species level and compared with unpressurized samples. The bacterium was identified by using bacterial identification schemes, biochemical tests and API kits (bioMérieux, Marcyl’Etoile, France). Diversity analysis was performed using PRIMER (Plymouth Routines in Multivariate Research) software v 5.2.2. The significant elimination of microflora was found to be proportional with the pressure level. In the case of spore formers, mere destruction was noticed after HP-treatment. Arthrobacter spp., Listeria grayi and Corynebacterium spp. were the most piezotolerant bacteria in HP-treated samples. Diversity indices revealed a significant reduction of microflora of Indian white prawn. The apparent reduction of microflora with pressure level was clearly evident from the diversity indices; moreover a diminished piezotolerance of Gram negative spoilage bacteria was also observed. 相似文献
57.
A new method for determination of antithrombotic activity of egg white protein hydrolysate by microplate reader 总被引:3,自引:0,他引:3
Wan Gen Yang Zhang Wang* Shi Ying Xu School of Food Science&Technology Southern Yangtze University Wuxi China 《中国化学快报》2007,18(4):449-451
A new method for the determination of antithrombotic activity of egg white protein hydrolysate(EWPH)was developed using amicroplate reader.Reaction was carried out at 37℃ and pH 7.2 with fibrinogen concentration 0.1%.Microplate reading wasconducted at 405 nm.Inhibition rate of EWPH on thrombin activity showed linearity(R~2=0.9971),when the inhibition rate was inthe range of 10-90%.The lower limit of detection(LLD,at 99.7%probability)and the biological limit of detection(BLD,at 99.7%probability)of the method were 10.643 and 40 mg/mL,respectively.The repeatability standard deviation(R.S.D.)was 1.08%.Thestandard deviation of the method was 0.027 AT-U. 相似文献
58.
碳纳米微粒的共振散射光谱研究 总被引:35,自引:1,他引:35
液相碳纳米微粒的共振散射光谱实验表明,当碳浓度小于360mg/L时,它在400、470、510和940nm产生4个共振散射峰;浓度大于900mg/L时无共振散射、碳微粒浓度在0.45-45mg/L范围内与共振散射光强度I470nm成良好的性关系,研究了光源和扫描速度对液相碳纳米微粒共振散射光谱的影响。结果表明,光源的发射强度分布不一是产生共振散射光谱峰的一个重要因素,并结合已有的实验结果提出了界面共振吸收和黑白纳米微粒共振散射概念,解释了碳纳米微粒体系的共振散射光谱。 相似文献
59.
白光发光二极管被誉为第4代照明光源。ZnO纳米结构因含有大量本征和/或非本征缺陷使其除出现在紫外区域的带边发射外还能产生覆盖400-700 nm可见光范围的深能级发光,从而可用于白光LED。本文系统地介绍了将ZnO纳米结构应用于白光LED的几种器件构造,并评述了各自的性能特点和研究进展。因为直接基于ZnO纳米结构电致发光的白光LED需要施加较高的偏压,所以将ZnO纳米结构与p型半导体复合制成异质结成为了研究的热点。ZnO纳米结构的制备方法和形貌特性会影响白光LED性能,对ZnO纳米结构进行掺杂是提升性能的重要手段。此外,将ZnO纳米材料和聚合物的优点集于一体的ZnO/聚合物异质结构也在白光LED中具有广阔的发展空间。最后,指出了纳米ZnO在白光LED应用中存在的问题和今后的发展方向。 相似文献
60.