全文获取类型
收费全文 | 1344篇 |
免费 | 45篇 |
国内免费 | 152篇 |
专业分类
化学 | 1401篇 |
晶体学 | 2篇 |
力学 | 3篇 |
综合类 | 15篇 |
数学 | 4篇 |
物理学 | 116篇 |
出版年
2023年 | 16篇 |
2022年 | 9篇 |
2021年 | 34篇 |
2020年 | 17篇 |
2019年 | 23篇 |
2018年 | 13篇 |
2017年 | 25篇 |
2016年 | 24篇 |
2015年 | 28篇 |
2014年 | 31篇 |
2013年 | 54篇 |
2012年 | 137篇 |
2011年 | 75篇 |
2010年 | 70篇 |
2009年 | 89篇 |
2008年 | 83篇 |
2007年 | 83篇 |
2006年 | 87篇 |
2005年 | 94篇 |
2004年 | 83篇 |
2003年 | 74篇 |
2002年 | 40篇 |
2001年 | 28篇 |
2000年 | 31篇 |
1999年 | 37篇 |
1998年 | 34篇 |
1997年 | 38篇 |
1996年 | 25篇 |
1995年 | 28篇 |
1994年 | 15篇 |
1993年 | 19篇 |
1992年 | 24篇 |
1991年 | 20篇 |
1990年 | 16篇 |
1989年 | 11篇 |
1988年 | 8篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1984年 | 2篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1975年 | 1篇 |
排序方式: 共有1541条查询结果,搜索用时 46 毫秒
121.
122.
《中国化学快报》2020,31(6):1576-1579
Reported herein is the first example of electrochemical selenocyanation of imidazo[1,5-a]quinolines with KSeCN under metal catalyst-and chemical oxidant-free conditions.This sustainable strategy shows a broad scope and great compatibility with functional groups,and affords synthetically and biologically important selenocyanated imidazo[1,5-a]quinolines in good to excellent yields with cheap graphite and Ni plates as the electrodes.The gram-scale synthesis was also successfully conducted,which might demonstrate the potential value of this electrochemical protocol. 相似文献
123.
铋膜电极微分电位溶出法测定生物材料中痕量铅 总被引:6,自引:0,他引:6
研究了镀铋膜电极替代镀汞膜电极痕量铅的微分电位溶出分析法(DPSA)。考察并优化了同位镀铋膜测定铅的条件。结果表明,在HAc-NaAc(pH=4.4)介质中,铅可在镀铋膜电极上得到灵敏的微分电位溶出峰;利用标准加入法对人尿及血中痕量铅进行了测定。本法避免了镀汞膜电极对人体健康及环境的危害。 相似文献
124.
Ammonia is a commonly used compound in the domestic and industrial fields. If ammonia found in wastewater after use is not treated, even at low concentrations it may cause toxic effects in the receiving environment. In this study, a hydrodynamic cavitation reactor (HDC) was designed with the aim of removing ammonia. The effect of parameters like different cavitation numbers, airflow, temperature and initial concentration on NH3 removal was researched. The potential of hydrodynamic cavitation for removal of volatile gases, like NH3, was assessed with the aid of two film theory mathematical equations. Experimental studies were performed at fixed pH = 11. Under the conditions of 0.12 cavitation number, 25 L/min airflow, 30 °C temperature and 2500 mg/L initial concentration, in 24 h 98.4% NH3 removal efficiency was achieved. With the same experimental conditions without any air, the HDC reactor provided 89.5% NH3 removal at the end of 24 h.The HDC reactor is very effective for the removal of volatile gases from wastewater and it was concluded that even in the absence of aeration, the desired NH3 removal efficiency was provided. 相似文献
125.
近年来,化学修饰电极以其独特的优越性,在分析测试中具有广阔的应用前景[1-6],因此对于新的修饰剂的研究,以及用修饰电极探讨灵敏度高,选择性好的测定方法具有重要的意义。2[2,3,5-三氮唑偶氮]-5-乙酰基氨基苯酚(2-(2,3,5-triazolylazo)-5-acetam idophenol,简称TZAAP)是一种新合成的有机化合物,其结构式为:由于TZAAP可以和金属离子形成稳定的配合物,在光谱法中可以作为显色剂用于环境及生物样品中微量元素的测定[7,8]。Nafion是一种优良的阳离子交换剂,用作电极修饰材料具有良好的离子交换特性[9]。本文作者制备了TZAAP-Nafion修饰… 相似文献
126.
Creatinine sensor based on a molecularly imprinted polymer-modified hanging mercury drop electrode 总被引:1,自引:0,他引:1
Molecularly imprinted polymers (MIP) have been elucidated to work as artificial receptors. In our present study, a MIP was applied as a molecular recognition element to a chemical sensor. We have constructed a creatinine sensor based on a MIP layer selective for creatinine and its differential pulse, cathodic stripping voltammetric detection (DPCSV) on a hanging mercury drop electrode (HMDE). The creatinine sensor was fabricated by the drop coating of dimethylformamide (DMF) solution of a creatinine-imprinted polymer onto the surface of HMDE. The modified-HMDE, preanodised in neutral medium at +0.4 V versus Ag/AgCl for 120 s, exhibited a marked enhancement in DPCSV current in comparison to the less anodised (≤+0.3 V) HMDE. The creatinine was preconcentrated and instantaneously oxidised in MIP layer giving DPCSV response in the concentration range of 0.0025-84.0 μg mL−1 [detection limit (3σ) 1.49 ng mL−1]. The sensor was found to be highly selective for creatinine without any response of interferents viz., NaCl, urea, creatine, glucose, phenylalanine, tyrosine, histidine and cytosine. The non-imprinted polymer-modified electrode did not show linear response to creatinine. The imprinting factor as high as 9.4 implies that the imprinted polymer exclusively acts as a recognition element of creatinine sensor. The proposed procedure can be used to determine creatinine in human blood serum without any preliminary treatment of the sample in an accurate, rapid and simple way. 相似文献
127.
研究了利用玻碳电极吸附伏安法测定痕量硫化物的新方法。在含高铁离子的酸性溶液中,硫化物与对-氨基苯二甲基盐酸盐(p-ADAD)反应生成亚甲基蓝,采用线性扫描伏安法亚甲基蓝于-0.30 V(vs.SCE)在玻碳电极上出现灵敏的还原峰,峰电流与S2-浓度在0~25μg/mL范围内呈良好的线性关系。优化了实验条件,研究了电极反应机理。该方法具有灵敏、简便、快速、避免汞污染等特点。已成功用于多种水样中痕量硫化物的测定,回收率为98.0%~104.6%,结果令人满意。 相似文献
128.
129.
130.