全文获取类型
收费全文 | 301篇 |
免费 | 12篇 |
国内免费 | 39篇 |
专业分类
化学 | 302篇 |
综合类 | 1篇 |
数学 | 17篇 |
物理学 | 32篇 |
出版年
2022年 | 8篇 |
2021年 | 7篇 |
2020年 | 10篇 |
2019年 | 10篇 |
2018年 | 15篇 |
2017年 | 14篇 |
2016年 | 12篇 |
2015年 | 11篇 |
2014年 | 16篇 |
2013年 | 15篇 |
2012年 | 31篇 |
2011年 | 34篇 |
2010年 | 24篇 |
2009年 | 21篇 |
2008年 | 19篇 |
2007年 | 12篇 |
2006年 | 14篇 |
2005年 | 13篇 |
2004年 | 10篇 |
2003年 | 16篇 |
2002年 | 7篇 |
2001年 | 3篇 |
2000年 | 8篇 |
1999年 | 5篇 |
1998年 | 1篇 |
1997年 | 7篇 |
1996年 | 2篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1988年 | 1篇 |
排序方式: 共有352条查询结果,搜索用时 0 毫秒
101.
界面缩聚法合成双酚A芳香环状聚醚砜 总被引:2,自引:0,他引:2
聚芳醚(酮、砜)是一类耐高温、耐溶剂的高性能的聚合材料,具有很好的机械和加工性能,广泛应用于工程塑料及复合材料等领域.线性聚芳醚(酮,砜)一般由亲核取代反应或亲电取代反应在极性溶剂中制得,Yoshio等[1]报道利用相转移催化法制备聚芳醚砜,近年来,... 相似文献
102.
A theoretical consideration of the phase-inversion technique to prepare waterborne particles based on the experimental facts
of the phase inversion process given in part 1 of this series is presented. The deformation and breakup of the water droplets
dispersed in an epoxy resin phase under shear action are analyzed in terms of microrheology. The interaction and coalescence
dynamics among the water droplets stabilized by an interfacial layer formed by the emulsifier molecules are discussed in terms
of Derjaguin–Landau–Verwey–Overbeek theory and effective collision theory, respectively. A criterion for the completion of
phase-inversion is that the attraction among the water droplets exceeds the entropic repulsion. Thus, a physical model of
phase-inversion is proposed to predict the effects of some control variables on the phase-inversion process as well as the
structural features of the waterborne particles, by which the experimental results could be well interpreted. It is indicated
that the achievement of phase inversion is determined by the dynamic coalescence among the water droplets before the phase-inversion
point (PIP). If the dynamic coalescence among the water droplets is ignored, phase inversion is achieved completely and sub-
micron-sized particles are prepared. In comparison, if the dynamic coalescence is significant, phase inversion is achieved
incompletely and a large complex water-in-oil-in-water structure is prepared. In the case of complete phase inversion, it
is shown that the size of the waterborne particles is comparable with the size of the water droplets before the PIP.
Received: 15 March 2000/Accepted: 16 May 2000 相似文献
103.
AF C~*-代数中的子代数上的保幂等映射和局部导子 总被引:2,自引:0,他引:2
证明了从AFC-代数E中的子代数A到任意赋范代数B上的范数连续保幂等映射是Jordan同态,以及从A到任意赋范E-双模M上的局部导子是导子,从而推广了Crist关于局部导子的结果. 相似文献
104.
105.
Chao Zhao Peisi Xie Ti Yang Hailin Wang Arthur Chi Kong Chung Zongwei Cai 《中国化学快报》2018,29(8):1281-1283
Exposure to BPS induced glycerophospholipid fatty acid remodeling, which might be useful in toxicity evaluation for bisphenols-induced hepatic diseases. 相似文献
106.
搅拌棒固相萃取与液相色谱联用测定水样品中烷基酚类污染物 总被引:4,自引:0,他引:4
建立了简单、快速、灵敏测定水环境中的双酚A(BPA)、辛基酚(OP)、壬基酚(NP)的方法。以聚(N-乙烯基咪唑-二乙烯基苯)整体材料为涂层的搅拌棒固相萃取技术富集目标物,然后与高效液相色谱-二极管阵列检测器联用测定水样品中烷基酚类污染物。考察了萃取时间、解析时间、样品基质的pH值、离子强度等实验条件对萃取效率的影响。在最佳条件下,3种目标化合物的线性范围是1.0~200μg/L,检出限LOD(S/N=3)在0.13~0.66μg/L之间,定量限LOQ(S/N=10)在0.44~2.19μg/L之间。在对海水和污水处理厂的实际水样测定中,3种目标化合物的不同加标水平的回收率为37.8%~101.1%。本方法具有简便、快速、高效、灵敏等优点。 相似文献
107.
包装材料中的酚类环境雌激素的测定-固相微萃取/气相色谱质谱法 总被引:2,自引:1,他引:2
建立了固相微萃取-气相色谱质谱法(SPME/GCMS)快速测定包装材料中的烷基酚、双酚A的分析方法,以CH2Cl2为提取溶剂,采用快速溶剂萃取法萃取包装材料中的酚类物质,萃取物经N,O双(三甲基硅烷基)三氟乙酰胺(BSTFA)衍生化后,用PDMS/DVB纤维萃取,利用GC-MS对包装材料中4-叔-丁基酚、4-叔-辛基酚、4-辛基酚、4-壬基酚、双酚A 5种目标物进行定性定量分析。结果表明,酚类物质主要存在于聚碳酸酯材料中,检测4-叔-辛基酚、4-辛基酚和双酚A的质量分数分别为82.44、60.28和78.35μg/kg。 相似文献
108.
建立了人体血清中多种环境雌激素:多溴联苯醚、邻苯二甲酸酯和双酚A的快速可靠的连续在线分离及在气相色谱-质谱上的分析方法.血清样品经过浓盐酸使蛋白质变性,用乙醚萃取,经硅胶柱分离出多个族组分:多溴联苯醚(Polybrominated diphenyl ethers,PBDEs)、邻苯二甲酸酯(Phthalate estcrs,PAEs)和双酚A(Bisphenol A,BPA),最后由气相色谱-质谱的选择离子检测测定.PBDEs,PAEs和BPA标准曲线回归方程拟合度R2均大于0.99,表明在测试的浓度范围内线性关系良好.PBDEs目标化合物的检出限为0.005~0.048μg/L,PAEs目标化合物的检出限为0.103~0.833μg/L,BPA的检出限是0.035 μg/L.标准样品重复样中,PBDEs的RSD(relative standard deviation)值分别为2.8%~10.9%;PAEs的RSD值为5.6%~9.9%;BPA的RSD值为3.0%.实际血清样品中,PBDEs的加标回收物PCB209(Polychloride diphenyl ether 209)的回收率范围是74.8%~88.5%;PAEs中的加标回收物DBP-D4(Dibutyl phthalateDeutorium 4)的回收率范围为78.7%~97.0%;BPA中的加标回收物BPA-D16( Bisphenol A-Deutorium 16)的回收率范围是76.3%~93.1%.本方法检测血液中多种环境雌激素灵敏度高、重现性和回收率均良好. 相似文献
109.
The absorbance characteristics and influential factors on these characteristics for a liquid-phase gas sensor, which is based on gas–permeable liquid core waveguides (LCWs), are studied from theoretical and experimental viewpoints in this paper. According to theory, it is predicted that absorbance is proportional to the analyte concentration, sampling time, analyte diffusion coefficient, and geometric factor of this device when the depletion layer of the analyte is ignored. The experimental results are in agreement with the theoretical hypothesis. According to the experimental results, absorbance is time-dependent and increasing linearly over time after the requisite response time with a linear correlation coefficient r2 > 0.999. In the linear region, the rate of absorbance change (RAC) indicates improved linearity with sample concentration and a relative higher sensitivity than instantaneous absorbance does. By using a core liquid that is more affinitive to the analyte, reducing wall thickness and the inner diameter of the tubing, or increasing sample flow rate limitedly, the response time can be decreased and the sensitivity can be increased. However, increasing the LCW length can only enhance sensitivity and has no effect on response time. For liquid phase detection, there is a maximum flow rate, and the absorbance will decrease beyond the stated limit. Under experimental conditions, hexane as the LCW core solvent, a tubing wall thickness of 0.1 mm, a length of 10 cm, and a flow rate of 12 mL min−1, the detection results for the aqueous benzene sample demonstrate a response time of 4 min. Additionally, the standard curve for the RAC versus concentration is RAC = 0.0267 c + 0.0351 (AU min−1), with r2 = 0.9922 within concentrations of 0.5–3.0 mg L−1. The relative error for 0.5 mg L−1 benzene (n = 6) is 7.4 ± 3.7%, and the LOD is 0.04 mg L−1. This research can provide theoretical and practical guides for liquid–phase gas sensor design and development based on a gas-permeable Teflon AF 2400 LCW. 相似文献
110.
以苯酚和含有不同链长的长链脂肪酮作为原料, 制备了与双酚A结构相似的双酚单体, 并与4, 4'-二氟二苯酮共聚, 合成了几种含有不同长度脂肪族侧链结构的聚醚醚酮类(PEEKs)聚合物. 利用元素分析和核磁共振氢谱(1H NMR)对所合成的双酚单体进行了表征, 并用红外光谱(FTIR)\, 示差量热扫描仪(DSC)、热失重分析仪(TGA)和电子拉力机对所合成的聚合物结构和性能的关系进行了研究. 相似文献