全文获取类型
收费全文 | 2350篇 |
免费 | 396篇 |
国内免费 | 257篇 |
专业分类
化学 | 1098篇 |
晶体学 | 33篇 |
力学 | 146篇 |
综合类 | 92篇 |
数学 | 314篇 |
物理学 | 1320篇 |
出版年
2024年 | 11篇 |
2023年 | 36篇 |
2022年 | 117篇 |
2021年 | 132篇 |
2020年 | 94篇 |
2019年 | 66篇 |
2018年 | 68篇 |
2017年 | 128篇 |
2016年 | 143篇 |
2015年 | 90篇 |
2014年 | 148篇 |
2013年 | 133篇 |
2012年 | 130篇 |
2011年 | 152篇 |
2010年 | 114篇 |
2009年 | 130篇 |
2008年 | 134篇 |
2007年 | 157篇 |
2006年 | 142篇 |
2005年 | 123篇 |
2004年 | 145篇 |
2003年 | 112篇 |
2002年 | 130篇 |
2001年 | 65篇 |
2000年 | 47篇 |
1999年 | 52篇 |
1998年 | 39篇 |
1997年 | 25篇 |
1996年 | 18篇 |
1995年 | 20篇 |
1994年 | 19篇 |
1993年 | 14篇 |
1992年 | 12篇 |
1991年 | 9篇 |
1990年 | 5篇 |
1989年 | 6篇 |
1988年 | 9篇 |
1987年 | 3篇 |
1986年 | 8篇 |
1985年 | 3篇 |
1984年 | 5篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1981年 | 1篇 |
1979年 | 1篇 |
1974年 | 1篇 |
1971年 | 1篇 |
排序方式: 共有3003条查询结果,搜索用时 312 毫秒
61.
LIU Xiu-dong YU Wei-ting LIN Jun-zhang MA Xiao-jun YUAN Quan 《高等学校化学研究》2007,23(5):579-584
Alginate has been widely used in cell microencapsulation and drug delivery systems in the form of gel beads or microcapsules.Although an alternative novel emulsification-internal gelation technology has been established and both the properties and the potential applications of the beads in drug delivery systems have been studied,the mechanism has not been well understood compared with the traditional droplet method(external gelation technology).On the basis of our previous knowledge that the novel technology is composed of complicatedly consecutive processes with multistep diffusion and reaction,and the diffusion of acetic acid across oil/water interface being the prerequisite that determines the occurrence and rate for the reactions and the structures and properties of final produced gel beads,a special emphasis was placed on the diffusion process.With the aid of diffusion modeling and simple experimental design,the diffusion rate constant and diffusion coefficient of acetic acid across oil/water interface were determined to be in the orders of magnitude of 10-6 and 10-16,respectively.This knowledge will be of particular importance in understanding and interpreting the formation,structure of the gel beads and the relationship between the structure and properties and guiding the preparation and quality control of the gel beads. 相似文献
62.
Kizek R Masarik M Kramer KJ Potesil D Bailey M Howard JA Klejdus B Mikelova R Adam V Trnkova L Jelen F 《Analytical and bioanalytical chemistry》2005,381(6):1167-1178
The electroanalytical determination of avidin in solution, in a carbon paste, and in a transgenic maize extract was performed in acidic medium at a carbon paste electrode (CPE). The oxidative voltammetric signal resulting from the presence of tyrosine and tryptophan in avidin was observed using square-wave voltammetry. The process could be used to determine avidin concentrations up to 3 fM (100 amol in 3 l drop) in solution, 700 fM (174 fmol in 250 l solution) in an avidin-modified electrode, and 174 nM in a maize seed extract. In the case of the avidin-modified CPE, several parameters were studied in order to optimize the measurements, such as electrode accumulation time, composition of the avidin-modified CPE, and the elution time of avidin. In addition, the avidin-modified electrode was used to detect biotin in solution (the detection limit was 7.6 pmol in a 6 l drop) and to detect biotin in a pharmaceutical drug after various solvent extraction procedures. Comparable studies for the detection of biotin were developed using HPLC with diode array detection (HPLC-DAD) and flow injection analysis with electrochemical detection, which allowed biotin to be detected at levels as low as 614 pM and 6.6 nM, respectively. The effects of applied potential, acetonitrile content, and flow rate of the mobile phase on the FIA-ED signal were also studied. 相似文献
63.
64.
Fluorescence has been the preferred choice for data quantification in biomedical microarray formats since their earliest days. As much as the formats have grown and evolved over the years, the methods in optical analysis have become ever more sophisticated and complex in order to produce more and better output. This review will provide an insight into the most common methods and the state-of-the-art of all areas in microarray fluorescence analysis. Starting with an overview on microarray formats with a focus on their demands on the readout, the most common and useful organic fluorescent stains are discussed before proceeding on to other approaches; the use of semiconductor nanocrystals (quantum dots), polymer and silica nanoparticles and fluorescent proteins. Ways to enhance the intrinsically low signal on biochips have become increasingly important as they offer a sound approach towards the detection of low concentration sample content. The three main categories are presented: amplification using DNA, enzymes, and dendrimers. As much diversity as on the microarrays themselves can be found at the detection device. Standard optical microarray detectors, and non-standard methods using fluorescence anisotropy, fluorescence lifetime imaging (FLIM) and fluorescence resonance energy transfer (FRET), and their advantages and disadvantages are discussed. 相似文献
65.
综述了近8年来液相平行合成和组合合成中应用的不同技术, 包括可溶性载体、氟合成技术、离子液体、固相试剂树脂以及低聚乙烯二醇(OEG)衍生物的应用等几方面内容. 论述了它们的基本原理以及相关的应用实例, 并着重强调了目标化合物的分离纯化方法. 相似文献
66.
重金属污染土壤植物修复的强化措施研究进展 总被引:2,自引:0,他引:2
徐功军 《广东微量元素科学》2006,13(3):1-8
植物修复是一种有着巨大市场潜力的治理重金属污染土壤的技术,由于影响植物修复效率的因素较多,至今实际应用还很少。针对目前植物修复技术的不足,主要从植物本身的性能、重金属的生物有效性以及农艺管理措施等三方面,综述了近年来国内外有关植物修复强化措施的研究进展,并展望了今后该领域的研究方向。 相似文献
67.
As a new concept for the design of effective photocatalysts, an ion beam technology using accelerated metal ions, a metal ion implantation and an ionized cluster beam (ICB) method, have been applied to design unique photocatalysts. The metal ion implantation of TiO2 and Ti-containing zeolites with highly accelerated metal ions (V+, Cr+, etc.) is useful in designing photocatalysts that can operate efficiently under visible light irradiation. Also, an ICB method with a low acceleration energy is useful in preparing transparent TiO2 thin films on various types of substrates for the efficient photocatalytic degradation of pollutants diluted in water and air. The combination of the ICB method and metal ion implantation can develop the TiO2 thin films that are able to operate not only under UV light but also under visible light irradiation. 相似文献
68.
口腔癌系头颈部癌,癌组织均位于口腔内,其非侵入性早期诊断是减少该病死亡的有效手段.唾液系口腔癌变相关物质首先释放进入的体液,取材方便,安全无创,是口腔癌普查筛选、早期诊断的首选指标.本文对唾液肿瘤生物标志物的种类、目前国内外常用的检测方法进行概述,重点阐述新型电化学生物传感方法在口腔癌相关唾液肿瘤生物标志物检测方面的相关应用及其最新研究进展.并对口腔癌相关唾液肿瘤生物标志物电化学传感技术的未来发展方向提出展望,拟为其深入研究与应用提供参考. 相似文献
69.
YIN YingWu 《合成化学》2004,12(Z1)
Green chemistry is also called environment harmless or environment friendly chemistry.Green chemistry requires to use new synthetic methods, engineering technologies and processes to eliminate or reduce by-products, wastes or products that harmful to human health, community safety,and ecology environment. Green chemistry pursues to control the usage of the harmful and toxic materials, reduce waste emission, avoid necessity to treat the wastes; Green Chemistry advocates wastes management from the beginning, improving the efficiency of atoms, optimizing the use of resources and energy, lowering the cost of production. Green Chemistry technologies are the ultimate path to the clean chemical production in the future.Insight Co. takes "hospital of enterprises" and "bank of technologies" as our characteristics in business, and deems the development and spread of green chemistry as our mission. We developed an unique business model which combines education, research and production. In the past 8 years,we had applied and obtained more than 30 patents and received more than ten national and provincial awards in technology progress.We had made great progress in the manufacturing of organophosphorus pesticides, especially the production of omethoate, methamidophos, paraquat and glycyrrhizinic phosphor, etc., which made a stable foundation for INSIGHT's development. We had also achieved great success in the high efficiency low toxic pesticides, such as imidacloprid, etofenprox, metalaxyl and in the new synthetic methods in various amino acids as well as in the pharmaceutical intermediates. The new method of preparation indigo using N-phenylglycinonitrile is an advanced process in the world in terms of the clean production technology for Ferro cyanide and HCN's transformation rate improvement. We solved the pollution problem of the old route. The newly developed substituted product for indigo using a clean production technology which greatly reduced the material consumption and environmental pollution. Insight has facilities producing nearly 20 photo-initiators and developed the new technique for light-curing lubricity, water-born resin, the technique for water-bon coating and their associated applications. The successfully developed technology of new high performance emulsion will promote the technology advancement in the coating industry and the wide spread of new coating in China.Insight has developed a series of new technologies, including a novel reactor technology - using a newly designed patented blade, has been characterized as high efficiency & energy saving reactor.The novel technology research and development are widely applied in INSIGHT's ten-year practice.We studied and confirmed the non-thermal catalyzing effect of microwaves, proposed a "weak microwave" theory, and a chemical reaction rate equation. We proposed that in the existence of microwave magnesium ions and phosphate, amino acid can be activated to form peptide which maybe the path of the origin of life.A 3000mt/a pilot plant in Chongqing using carbon monoxide and hydrogen to produce dimethyl ether in a single step has been built via collaboration with the Dept. of Chemical Engineering at Tsinghua University. The large scale, low cost production of dimethyl ether may possible through comprehensive technology improvement. This technology will take full advantage of current ammonia production facilities, and try to solve the global fuel shortage problem. 相似文献
70.