全文获取类型
收费全文 | 8323篇 |
免费 | 105篇 |
国内免费 | 832篇 |
专业分类
化学 | 6826篇 |
晶体学 | 10篇 |
力学 | 8篇 |
综合类 | 73篇 |
物理学 | 2343篇 |
出版年
2024年 | 14篇 |
2023年 | 121篇 |
2022年 | 110篇 |
2021年 | 119篇 |
2020年 | 103篇 |
2019年 | 166篇 |
2018年 | 132篇 |
2017年 | 206篇 |
2016年 | 183篇 |
2015年 | 184篇 |
2014年 | 246篇 |
2013年 | 385篇 |
2012年 | 768篇 |
2011年 | 555篇 |
2010年 | 395篇 |
2009年 | 539篇 |
2008年 | 540篇 |
2007年 | 578篇 |
2006年 | 531篇 |
2005年 | 417篇 |
2004年 | 394篇 |
2003年 | 264篇 |
2002年 | 264篇 |
2001年 | 221篇 |
2000年 | 210篇 |
1999年 | 245篇 |
1998年 | 200篇 |
1997年 | 187篇 |
1996年 | 165篇 |
1995年 | 135篇 |
1994年 | 125篇 |
1993年 | 111篇 |
1992年 | 123篇 |
1991年 | 78篇 |
1990年 | 69篇 |
1989年 | 55篇 |
1988年 | 31篇 |
1987年 | 23篇 |
1986年 | 26篇 |
1985年 | 6篇 |
1984年 | 7篇 |
1983年 | 3篇 |
1982年 | 9篇 |
1981年 | 4篇 |
1980年 | 7篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1973年 | 1篇 |
1972年 | 1篇 |
排序方式: 共有9260条查询结果,搜索用时 15 毫秒
171.
Gary R. Burnett Gareth D. Rees David C. Steytler Brian H. Robinson 《Colloids and surfaces. A, Physicochemical and engineering aspects》2004,250(1-3):171-178
Fluorescence correlation spectroscopy (FCS) has been successfully used to characterise water-in-oil (w/o) microemulsions. The investigated systems were stabilised by sodium bis-2-ethylhexyl sulphosuccinate (AOT) and the measured diffusion times have been related to the radii of the aggregated species, which for some systems, were separately determined by small-angle neutron scattering (SANS). We demonstrate that FCS is capable of measuring hydrodynamic radii of microemulsions rapidly and at surfactant concentrations lower than previously reported for other techniques. FCS was also used to specifically interrogate microemulsion droplets containing a fluorescently-labelled biomolecule, specifically phalloidin, a peptide fungal toxin from Amanita phalloides, and the enzyme -chymotrypsin (-CT). The microemulsion droplets are only marginally increased in size if a small peptide (phalloidin) is included in the water phase, whereas the droplet size is significantly increased when a larger protein (-CT) is included. 相似文献
172.
The diffusion phenomenon of pyrene in silicone coatings prepared from various commercial silicone resins with different viscosities was investigated using steady state excimer fluorescence technique. The amount of pyrene lost from the coatings by diffusion at different temperatures ranging from 25 to 70 °C was estimated from the excimer emission intensity. The diffusion coefficients (D) and activation energy of diffusion of pyrene in silicone coatings were determined. It was found that the kinetic parameters of pyrene were comparable in all the four silicone coatings and independent of the viscosity of the resin. The D values were lower than those expected for pyrene in PDMS resins in the corresponding viscosity range. This may be attributed to restricted mobility of pyrene due to cross-linking of polymer chains in the cured silicone coatings. 相似文献
173.
Recent analytical innovations for nucleic acid detection have revolutionized the biological sciences. Single nucleic acid sequence detection methods have been expanded to incorporate multiplexed detection strategies. A variety of nucleic acid detection formats are now available that can address high throughput genomic interrogation. Many of these parallel detection platforms or arrays, employ fluorescence as the signaling method. Fluorescence-based assays offer many advantages, including increased sensitivity, safety and multiplexing capabilities, as well as the ability to measure multiple fluorescence properties. Multiplexed microarray platforms provide parallel detection capabilities capable of measuring thousands of simultaneous responses. This review will discuss both single target detection and microarray applications with a focus on gene expression and pathogenic microorganism (PM) detection. 相似文献
174.
基于芘的荧光熄灭的单质碘荧光敏感膜的研究 总被引:8,自引:0,他引:8
单质碘熄灭固定于增塑的PVC膜中的芘的荧光,且这种熄灭作用可逆。本据此研制了用于测定单质碘浓度的荧光敏感膜,最佳膜组成为2~4mg芘、50mgPVC粉、100mg邻苯二甲酸二异辛酯,测定碘的浓度范围为2.26×10^-5~1.04×10^-3mol/L。此膜测定单质碘的重现性好,响应时间小于40s。除Fe^3+、Bi^3+外,其它常见离子均无干扰。将此膜用于食盐中碘的测定,结果令人满意。 相似文献
175.
In this study, we developed an analytical method for the enantioseparation of ofloxacin, using capillary electrophoresis with fluorescence detection. The optimum background electrolyte was obtained to be 60 mM hydroxylpropyl‐β‐cyclodextrin (HP‐β‐CD) in 50 mM phosphate buffer at pH 2.30. Under these conditions, the (+) and (‐) ofloxacin were completely separated, with the detection limit of 10 nM when the sample was prepared in deionized water. The linear ranges of levofloxacin in deionized water and untreated urine were 10?7 to 5 × 10?3 M with R2 = 0.9989 and 5 × 10?6to 5 × 10?3 M with R2 = 0.9943, respectively. We also applied this method to investigate the purity of a commercial drug. The results revealed that the ratio between (+)‐ofloxacin and (‐)‐ofloxacin (levofloxacin) was 99.9:0.1, and there is about 93 mg levofloxacin per tablet (200 mg). The concentration of levofloxacin in patient's urine was founded to be 7.9 × 10?4M, and the ratio between the two optical isomers was 99.3:0.7. 相似文献
176.
丁基罗丹明B—钼酸盐光度法连续测定铈和钪 总被引:4,自引:0,他引:4
在聚乙烯醇(PVA)存在下,丁基罗丹明B(BRB)分别与铈钼、钪钼杂多酸络阴离子形成离子缔合物,其最大吸收均位于570nm,表面摩尔吸光度分别为εCe=3.96×10^6L.mol^-1.cm^-1,εSc=4.71×10^5L.mol^-1.cm^-1,服从比耳定律范围分别为0-24μg/L Ce和0-60μg/LSc,测定极限为Ce1.0μg/L(n=12)和Sc1.9μg/L(n=10),对 相似文献
177.
催化褪色光度法测定痕量钴的研究 总被引:15,自引:2,他引:15
研究了在PH10.5的Na2B4O7-NaOH介质中,痕量钴(Ⅱ)对过氧化氢氧化桑色素初色反应的催化作用,建立了催化动力学光度法测定痕量钴的新方法。方法的线性范围为0-1.2μ/mL检出限为4.4*10^-18g/L。用于水和维生素B12中钴的测定,结果满意。 相似文献
178.
Medha Rele Sudhir Kapoor Shweta Hedge Sergej Naumov Tulsi Mukherjee 《Research on Chemical Intermediates》2006,32(7):637-645
Many photo-physical studies have been reported for the detection of Hg2+ ions. Here we present the effect of Hg
2
2+
ions on the absorption and fluorescence of indole-2-carboxylic acid (I2C). Experimental evidence, supported by density functional
theory B3LYP/LANL2DZ/PCM, for the formation of a I2C-Hg
2
2+
complex, is reported for the first time. It was observed that I2C forms a ground-state complex with Hg
2
2+
ions in a ratio of 3:1. The possibility of I2C to be used as a selective novel chemical sensor for the spectrophotometric
detection of mercurous ions is described. 相似文献
179.
水中阴离子表面活性剂的吸附分光光度法测定 总被引:7,自引:0,他引:7
研究萘基二苯甲烷与阴离子表面活性剂的缔合反应及缔合物在聚合物颗粒表面的吸附及洗脱 ,提出了碱性艳蓝BO分光光度法测定河水中的阴离子表面活性剂 ;碱性艳蓝BO与十二烷基苯磺酸钠、十二烷基硫酸钠、十二烷基磺酸钠的缔合物的表观摩尔吸光系数分别为3.76×104、3.63×104、2.15×104L·mol -1·cm -1 ,方法的线性范围为0.0~2.0mg/L,相对标准偏差3.8% (n=8);应用该法测定河水中阴离子表面活性剂含量 ,结果令人满意 相似文献
180.
两种计算吸光光度法同时测定钙镁 总被引:3,自引:0,他引:3
研究了在pH10.5的硼砂-氢氧化钾缓冲溶液和乙醇的增敏作用条件下,偶氮氯膦Ⅰ与钙、镁的吸收特性,建立了多波长光度法同时测定钙和镁的方法。采用两种矩阵算法对试验数据进行处理,并对结果进行比较和分析。钙和镁含量在0~25μg/25ml范围内用计算法Ⅱ能得到准确结果。 相似文献