全文获取类型
收费全文 | 617篇 |
免费 | 34篇 |
国内免费 | 58篇 |
专业分类
化学 | 582篇 |
晶体学 | 4篇 |
力学 | 4篇 |
综合类 | 35篇 |
数学 | 18篇 |
物理学 | 66篇 |
出版年
2024年 | 2篇 |
2023年 | 13篇 |
2022年 | 42篇 |
2021年 | 65篇 |
2020年 | 38篇 |
2019年 | 25篇 |
2018年 | 16篇 |
2017年 | 30篇 |
2016年 | 20篇 |
2015年 | 21篇 |
2014年 | 21篇 |
2013年 | 43篇 |
2012年 | 36篇 |
2011年 | 36篇 |
2010年 | 25篇 |
2009年 | 27篇 |
2008年 | 38篇 |
2007年 | 30篇 |
2006年 | 30篇 |
2005年 | 23篇 |
2004年 | 23篇 |
2003年 | 28篇 |
2002年 | 20篇 |
2001年 | 6篇 |
2000年 | 10篇 |
1999年 | 13篇 |
1998年 | 5篇 |
1997年 | 4篇 |
1996年 | 2篇 |
1995年 | 3篇 |
1994年 | 3篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1991年 | 3篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1986年 | 2篇 |
1983年 | 1篇 |
排序方式: 共有709条查询结果,搜索用时 341 毫秒
131.
Bing Shao Dong Chen Jing Zhang Yongning Wu Chengjun Sun 《Journal of chromatography. A》2009,1216(47):8312-8318
A multi-residue method for the analysis of 76 pharmaceutical agents of nine classes of drugs (tetracyclines, macrolides, fluoroquinolones, β-agonists, β-blockers, diuretics, sedatives, sulfonamides and chloramphenicol) in slaughterhouse wastewater and a receiving river is presented. After simultaneous extraction with an Oasis HLB solid-phase extraction (SPE) cartridge and further purification using an amino SPE cartridge, analytes were detected by liquid chromatography–electrospray ionization-tandem mass spectrometry in positive or negative ion mode. Standard addition was used for quantification to overcome unavoidable matrix effects during ESI-MS analysis. Recoveries for most analytes based on matrix-matched calibration in different test matrices were >60%. The method quantification limits of 76 pharmaceuticals were in the range 0.2–30 ng/L. Nineteen compounds of 76 drugs were found in raw and treated slaughterhouse wastewater from four main slaughterhouses in Beijing. Sulfanamides (sulfanilamide, sulfameter), fluoroquenones (ofloxacin, pefloxacin, norfloxacin, ciprofloxacin, enrofloxacin), tetracyclines (tetracycline, oxytetracycline) and macrolides (kitasamycin, tylosin, erythromycin) were most frequently detected, with the highest levels up to ∼3 μg/L in slaughterhouse wastewater and ∼1 μg/L in treated wastewater. Illicit drugs for animal feeding such as clenbuterol and diazepam were commonly detected in slaughterhouse wastewater. These analytes were also observed in a river receiving slaughterhouse wastewater, with a highest level of up to 0.2 μg/L. 相似文献
132.
Preparation of magnetic chitosan microspheres and its applications in wastewater treatment 总被引:1,自引:0,他引:1
The methods of preparation of magnetic chitosan microspheres have been introduced. In addition, their applications in the
wastewater treatment, based on different kinds of wastewater, have been reviewed, and their mechanisms have been discussed.
Supported by the Key Natural Science Foundation of China (Grant No. 50633030) 相似文献
133.
Xinsong Yuan Baojun Yang Jianwen Hao Xingming Hu Jinmiao Zhu Huaze Dong Yanping Wang 《Crystal Research and Technology》2011,46(12):1296-1302
Single‐crystal α‐Mn2O3 nanowires were prepared via a “self‐sacrificing template” route, simply by calcining the prepared α‐MnO2 nanowire precursors at 550 °C for 1.5 h. XRD, TEM, SEM and HRTEM characterizations show that the as‐prepared α‐Mn2O3 samples are all phase pure and the nanowires have uniform diameters of approximately 15‐30 nm and lengths up to several micrometers. The catalytic performances of the prepared α‐Mn2O3 nanowires were studied in the degradation of coking wastewater with H2O2 as the oxidant, and the technological conditions were optimized by single‐factor and orthogonal experiments. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
134.
135.
紫外-可见光谱法分析难溶性黄药重金属配合物 总被引:1,自引:0,他引:1
提出可用于难溶性黄药重金属配合物检测的紫外光谱方法。实验首先考察了在黄药溶液中加入不同重金属离子后紫外-可见光谱的变化,发现Pb2+、Cu2+会与黄药生成难溶性配合物,而Fe2+,Zn2+,Mn2+对黄药溶液的紫外吸收影响很小。接下来实验比较了不同孔径的滤膜对难溶性配合物的去除效果,发现采用0.22 μm滤膜可以有效的将黄原酸铜或黄原酸铅与滤液分离。进一步的,实验研究了硫化钠与难溶性配合物反应的情况,结果表明S2-可以定量的将配合物中的黄原酸根置换到溶液中。研究得出可以通过加入硫化钠后滤液中黄药浓度的上升值得到原水样中难溶性黄药重金属配合物的含量。最后研究将该方法应用于郴州三十六湾三家铅锌选矿厂废水的分析中,其结果验证了该方法的可行性。 相似文献
136.
针对印染废水水质特性,在PbO2/Ti阳极、不锈钢板阴极的电解反应器中研究了电化学氧化对印染废水生化出水的处理效果. 试验结果表明,电氧化工艺可以实现化学需氧量(Chemical Oxygen Demand,COD)、氨氮和色度的同步去除. 在电流密度10 mA·cm-2时电解60 min,废水中COD、氨氮、色度、氯离子浓度以及pH值等指标均可达到GB/T 19923-2005《城市污水再生利用工业用水水质》中工艺与产品用水标准,电流效率达45.6%,吨水能耗4.1 kW·h. 相似文献
137.
138.
Systematically investigating the polarization gradient cooling in an optical molasses of ultracold cesium atoms
下载免费PDF全文
![点击此处可从《中国物理 B》网站下载免费的PDF全文](/ch/ext_images/free.gif)
We systematically investigate the polarization gradient cooling (PGC) process in an optical molasses of ultracold cesium atoms. The SR mode for changing the cooling laser, which means that the cooling laser frequency is stepped to the setting value while its intensity is ramped, is found to be the best for the PGC, compared with other modes studied. We verify that the heating effect of the cold atoms, which appears when the cooling laser intensity is lower than the saturation intensity, arises from insufficient polarization gradient cooling. Finally, an exponential decay function with a statistical explanation is introduced to explain the dependence of the cold atom temperature on the PGC interaction time. 相似文献
139.
石化废水排放量大、污染物成分复杂,对环境的危害较大。采用三维荧光光谱扫描技术分析了某大型石化企业综合污水处理厂各处理单元(水解酸化+A/O+接触氧化工艺)进出水的荧光光谱特征。污水厂总进水包含四个荧光峰Peak A,Peak B,Peak D,Peak E,分别位于λex/λem=220/300,225/340,270/300,275/340nm附近,荧光物质主要来自工业废水,水解酸化池出水各荧光峰强度有所降低,位置基本不变,厌氧池出水λex/λem=250/425nm附近出现新荧光峰Peak C,好氧池出水荧光峰Peak C处荧光强度有所增强,二沉池出水Peak A消失,二沉池之后水样荧光谱图变化不大;该处理工艺对荧光有机物的总去除率为92.0%,Peak A,Peak B,Peak D,Peak E附近的荧光有机物去除率分别为100.0%,91.2%,80.3%,92.0%;污水厂进水IPeak B/IPeak E值波动较大而出水变化不大,表明该污水处理厂运行稳定,其处理工艺具有较强的抗冲击负荷能力。 相似文献
140.
Wanhui Zhang Chunhua Feng Chaohai Wei Bo Yan Chaofei Wu Ning Li 《Journal of separation science》2012,35(23):3340-3346
GC‐MS analysis was performed on the coking sludge from a coking wastewater treatment plant (WWTP) to allow detailed chemical characterization of polycyclic aromatic hydrocarbons (PAHs). The identification and characterization of the isomers of PAHs was based on a positive match of mass spectral data of their isomers with mass spectra databases or based on a comparison of electron impact ionization mass spectra and retention times of target compounds with those reference compounds. In total, 160 PAH compounds including numerous N‐, O‐, S‐, OH‐, and Cl‐containing derivatives were positively identified for the first time. Quantitative analysis of target compounds was performed in the selected ion‐monitoring mode using the internal standard method. The total concentrations of selected compounds in the coking sludge samples from the anaerobic tank, aerobic tank, hydrolytic tank, and secondary clarifier of the WWTP ranged from 1690 ± 585 to 6690 ± 522 mg/kg, which were much higher than those in other industrial and municipal sludges. PAHs with four and five rings were found to be the dominant compounds, and diagnostic ratios of these compounds suggested that they had the characteristics of coal combustion and pyrolysis. 相似文献