全文获取类型
收费全文 | 19547篇 |
免费 | 3140篇 |
国内免费 | 2613篇 |
专业分类
化学 | 15147篇 |
晶体学 | 298篇 |
力学 | 901篇 |
综合类 | 195篇 |
数学 | 2241篇 |
物理学 | 6518篇 |
出版年
2024年 | 57篇 |
2023年 | 310篇 |
2022年 | 662篇 |
2021年 | 685篇 |
2020年 | 776篇 |
2019年 | 747篇 |
2018年 | 609篇 |
2017年 | 647篇 |
2016年 | 900篇 |
2015年 | 1003篇 |
2014年 | 1201篇 |
2013年 | 1462篇 |
2012年 | 1773篇 |
2011年 | 1856篇 |
2010年 | 1336篇 |
2009年 | 1256篇 |
2008年 | 1457篇 |
2007年 | 1240篇 |
2006年 | 1187篇 |
2005年 | 938篇 |
2004年 | 784篇 |
2003年 | 598篇 |
2002年 | 701篇 |
2001年 | 466篇 |
2000年 | 386篇 |
1999年 | 342篇 |
1998年 | 279篇 |
1997年 | 236篇 |
1996年 | 229篇 |
1995年 | 191篇 |
1994年 | 158篇 |
1993年 | 161篇 |
1992年 | 115篇 |
1991年 | 123篇 |
1990年 | 89篇 |
1989年 | 70篇 |
1988年 | 47篇 |
1987年 | 57篇 |
1986年 | 28篇 |
1985年 | 46篇 |
1984年 | 22篇 |
1983年 | 15篇 |
1982年 | 9篇 |
1981年 | 12篇 |
1980年 | 7篇 |
1979年 | 5篇 |
1978年 | 5篇 |
1977年 | 4篇 |
1976年 | 5篇 |
1975年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
Tian Jie Yang Weifeng Chen Min Zheng Minfang Chen Ding Qiu Yusheng 《Journal of Radioanalytical and Nuclear Chemistry》2022,331(2):1039-1049
Journal of Radioanalytical and Nuclear Chemistry - This study presents a time-efficient method of analysing 210Pb, 210Bi, and 210Po in natural waters. The optimum pH (1.00), temperature... 相似文献
2.
3.
This minireview describes the strategies for synthesis of fiuorinated surfactants potentially nonbioaccumulable.Various strategies have been focused on(Ⅰ) reducing the length of the perfluorocarbon chain,(Ⅱ) introducing hetero atoms into the fluorocarbon chain,(Ⅲ) introducing branch(herein and after branch means the fluoro-carbon chain section is not straight).In most cases,the surface tensions versus the surfactant concentrations have been assessed.These above strategies led to various highly fiuorinated(perfluorinated or not perfluorinated) surfactants whose chemical changes enabled to obtain novel alternatives to perfluorooctanoic acid(PFOA) and perfluorooctane sulphonate(PFOS). 相似文献
4.
We investigate terahertz radiation(T-rays) from a pentacene organic diode at room temperature. The quantum chemistry calculation for frequency-related Huang–Rhys factor of pentacene is also carried out. The results demonstrate that the T-rays can come from a bending vibration of pentacene skeleton after the energy of pentacene exciton transferring to the vibrational excited state via electron–phonon coupling. Frequency and natural bond orbital analytics of pentacene and its derivatives are performed in order to explain the result and develop new materials to get higher emission. This work provides a new way to produce T-rays with a simple device at room temperature. 相似文献
5.
Nonlinear Dynamics - In this paper, the current-controlled DC–DC buck converter from a new perspective are studied through the switching theory of flow, and the analytical conditions of the... 相似文献
6.
在管式反应器中采用苯甲酸、聚乙二醇、固体古马隆树脂(S)、液体古马隆树脂(L)为添加剂来降低煤沥青中有害物质苯并芘的含量,以期使得煤沥青可绿色化应用。采用紫外-可见分光光度计分析煤沥青中苯并芘含量。考察了反应温度、反应时间、添加剂添加量、催化剂等工艺条件对添加剂脱除煤沥青中苯并芘的影响。结果表明,不同工艺条件能降低煤沥青中苯并芘的含量。在优化条件下,不同添加剂对苯并芘脱除率由高到低依次为:液体古马隆树脂、聚乙二醇、苯甲酸和固体古马隆树脂。分析其反应机理,这与催化剂的酸性相关,发生亲电取代反应。结果表明,液体古马隆树脂(L)在催化剂存在下对煤沥青中苯并芘脱除率可达73.0%,显示了良好的应用前景。 相似文献
7.
8.
Liming Fan Feng Wang Dongsheng Zhao Yuxin Peng Yuxin Deng Yinwei Luo Xiutang Zhang 《应用有机金属化学》2020,34(12):e5960
Guided by the self-penetrating features can improve the stability of metal organic frameworks (MOFs), an unprecedented 3D self-penetrated framework, {[Zn (tptc)0.5(bimb)]·H2O}n ( NUC-6 , here NUC corresponding to North University of China), with 3D (4,4)-c {86} net, was designed. Benefit from the high chemical stability and excellent luminescent property, NUC-6 can be act as an efficient multi-response chemo-sensor in detecting dichloronitroaniline pesticide and nitrofuran antibiotics in water with the detection limits are 116 ppb for DCN pesticide, 16 ppb for NFT antibiotic, and 12 ppb for NTZ antibiotic. Besides, the mechanisms of luminescence quenching were revealed from the viewpoint of internal filter effect (IFE) and photo-induced electron transfer (PET), implied by the optical spectroscopy and quantum chemical calculation. This work provides a promising strategy to design stable MOFs by improving the self-penetrating features and to expand their practical applications in the detection of organic pollutants in aqueous medium. 相似文献
9.
10.
Four kinds of red phosphorescent organic light-emitting devices were fabricated and compared to investigate the effect of interfacial layers for hole transport and electron injection. 1 nm-thick LiF in the device A and C and 1 nm-thick Cs2CO3 in the device B and D were deposited as an electron injection layer between the anode and the electron transport layer, and 5 nm-thick layer of dipyrazion[2,3-f:2′,2′-h]quinoxaline-2,3,6,7,10,11-hexacarbonitrile[HATCN] was inserted as a hole transport interfacial layer between the hole injection layer and the hole transport layer only in the device C and D. Under a luminance of 1000 cd/m2, the power efficiencies were 7.6 lm/W and 8.5 lm/W in the device A and B, and 8.6 lm/W and 13.4 lm/W in the device C and D. The quantum efficiency of the device D was 15.8% under 1000 cd/m2 which was somewhat lower than those of the device A and C, but a little higher than that of the device B. The luminance of the device D was much higher than those of the other devices at a given votage. The luminance of the device D at 7 V was 23,710 cd/m2, which was 13.0, 3.4, and 4.0 times higher than those of the device A, B, and C at the same voltage, respectively. 相似文献