全文获取类型
收费全文 | 19782篇 |
免费 | 3377篇 |
国内免费 | 2684篇 |
专业分类
化学 | 14507篇 |
晶体学 | 279篇 |
力学 | 1169篇 |
综合类 | 203篇 |
数学 | 2278篇 |
物理学 | 7407篇 |
出版年
2024年 | 68篇 |
2023年 | 398篇 |
2022年 | 671篇 |
2021年 | 706篇 |
2020年 | 823篇 |
2019年 | 828篇 |
2018年 | 658篇 |
2017年 | 585篇 |
2016年 | 1021篇 |
2015年 | 958篇 |
2014年 | 1181篇 |
2013年 | 1479篇 |
2012年 | 1766篇 |
2011年 | 1721篇 |
2010年 | 1272篇 |
2009年 | 1164篇 |
2008年 | 1282篇 |
2007年 | 1228篇 |
2006年 | 1121篇 |
2005年 | 978篇 |
2004年 | 729篇 |
2003年 | 626篇 |
2002年 | 662篇 |
2001年 | 578篇 |
2000年 | 426篇 |
1999年 | 389篇 |
1998年 | 331篇 |
1997年 | 287篇 |
1996年 | 316篇 |
1995年 | 244篇 |
1994年 | 229篇 |
1993年 | 192篇 |
1992年 | 170篇 |
1991年 | 148篇 |
1990年 | 117篇 |
1989年 | 119篇 |
1988年 | 77篇 |
1987年 | 50篇 |
1986年 | 47篇 |
1985年 | 48篇 |
1984年 | 49篇 |
1983年 | 23篇 |
1982年 | 23篇 |
1981年 | 13篇 |
1980年 | 13篇 |
1978年 | 4篇 |
1977年 | 5篇 |
1976年 | 3篇 |
1974年 | 3篇 |
1957年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
112.
三正辛胺修饰电极伏安测定痕量金的研究 总被引:3,自引:0,他引:3
用化学修饰电极伏安测定痕量金,Kalcher K等曾采用阴离子交换剂碳糊修饰电极及打萨宗碳糊修饰电极检测100~300μg/L的金。本文采用三正辛胺(TOA)修饰玻碳电极,在1.5 mol/L介质中,Au(Ⅲ)在+0.16 V(vs SCE)处有一灵敏的不可逆还原峰。检出限为0.1μg/L。灵敏度比文献方法高千倍。Au(Ⅲ)浓度在5×10~(-7)~5×10~(-9)mol/L范围内峰高与浓度 相似文献
113.
In this review, we check out the number of published literature in the field of ECL biosensors trends during nearly a decade, and compare the research status of four different types of biosensors; summarize the application forms of nanomaterials in ECL biosensor. We have an overview of the building patterns and application example of the four main types of biosensors in the paper. 相似文献
114.
Meng Wang Weiyue Feng Junwen Shi Fang Zhang Bing Wang Motao Zhu BaiLi Yuliang Zhao Zhifang Chai 《Talanta》2007,71(5):2034-2039
A mild, efficient and convenient extraction method of using 2-mercaptoethanol contained extractant solution combined with an incubator shaker for determination of mercury species in biological samples by HPLC–ICP-MS has been developed. The effects of the concentration of 2-mercaptoethanol, the composition of the extractant solution and the shaking time on the efficiency of mercury extraction were evaluated. The optimization experiments indicated that the quantitative extraction of mercury species from biological samples could be achieved by using 0.1% (v/v) HCl, 0.1% (v/v) 2-mercapoethanol and 0.15% (m/v) KCl extractant solution in an incubator shaker for shaking overnight (about 12 h) at room temperature. The established method was validated by analysis of various biological certified reference materials, including NRCC DOLT-3 (dogfish liver), IAEA 436 (tuna fish), IAEA MA-B-3/TM (garfish filet), IAEA MA-M-2/TM (mussel tissue), GBW 08193 (bovine liver) and GBW 08572 (prawn). The analytical results of the reference materials were in good agreement with the certified or reference values of both methyl and total mercury, indicating that no distinguishable transformation between mercury species had occurred during the extraction and determination procedures. The limit of detection (LOD) for methyl (CH3Hg+) and inorganic mercury (Hg2+) by the method are both as 0.2 μg L−1. The relative standard deviation (R.S.D.s) for CH3Hg+ and Hg2+ are 3.0% and 5.8%, respectively. The advantages of the developed extraction method are that (1) it is easy to operate in HPLC–ICP-MS for mercury species determination since the extracted solution can be directly injected into the HPLC column without pH adjustment and (2) the memory effect of mercury in the ICP-MS measurement system can be reduced. 相似文献
115.
Xiaohua Zou Song Zhang Mianhong Shi Jilie Kong 《Journal of Solid State Electrochemistry》2007,11(2):317-322
A stepwise deposition method was employed to create ordered polyaniline (PANI) nanowires with remarkably enhanced capacitance. Cyclic voltammetry, AC impedance, and galvanostatic charge/discharge cycling were employed to investigate the electrochemical performance of the PANI electrodes. The PANI-deposited electrode exhibits much higher capacitance than those prepared by one-step deposition method, which were mainly contributed from the unique nano structure of PANI and the increased biological, economical, and technical surface areas. The superior capacitive behaviors of the nano PANI electrodes show great potential in preparation of high efficient electrochemical capacitors or rechargeable batteries. 相似文献
116.
117.
Shah BK Neckers DC Shi J Forsythe EW Morton D 《The journal of physical chemistry. A》2005,109(34):7677-7681
Anthanthrene (1) derivatives substituted at the 4,10 and 6,12 positions (2-6) were synthesized as promising candidates for organic light emitting diodes (OLEDs). The emission of these compounds can be manipulated in the blue region (lambda(max) = 437-467 nm) through structural modifications. Photophysical and electrochemical properties (phi(F) = 0.20-0.47; tau(F) = 2.97-6.06 ns; HOMO-LUMO energy gap = 2.25-2.56 eV) as well as geometry optimized structures of 1-6 are reported. 相似文献
118.
本文报道了一种新的简便的合成N-乙基α-甲基-间苯乙胺的方法。方法以三氟甲苯为原料,经氯甲基化,Gignard及Leuckart反应后得目标物,具有原料价廉易得,毒性较小,反应条件温和,工艺流程较短等特点。 相似文献
119.
120.
研究了直流电场对含LiClO4的聚氧化乙烯(PEO)400与环氧树脂形成的液晶态互穿网络高分子忆禽子导体的电导率的影响。在室温至90℃范围内,电导率随外加电压增加面降低。外加电压越高,对电导率变化的影响越大。 相似文献