全文获取类型
收费全文 | 119079篇 |
免费 | 20010篇 |
国内免费 | 11929篇 |
专业分类
化学 | 81023篇 |
晶体学 | 1361篇 |
力学 | 8069篇 |
综合类 | 700篇 |
数学 | 14004篇 |
物理学 | 45861篇 |
出版年
2024年 | 269篇 |
2023年 | 2291篇 |
2022年 | 3405篇 |
2021年 | 4128篇 |
2020年 | 4728篇 |
2019年 | 4577篇 |
2018年 | 3896篇 |
2017年 | 3565篇 |
2016年 | 5689篇 |
2015年 | 5400篇 |
2014年 | 6605篇 |
2013年 | 8686篇 |
2012年 | 10542篇 |
2011年 | 11198篇 |
2010年 | 7435篇 |
2009年 | 7073篇 |
2008年 | 7448篇 |
2007年 | 6875篇 |
2006年 | 6354篇 |
2005年 | 5330篇 |
2004年 | 4063篇 |
2003年 | 3177篇 |
2002年 | 2891篇 |
2001年 | 2406篇 |
2000年 | 2132篇 |
1999年 | 2440篇 |
1998年 | 2167篇 |
1997年 | 1993篇 |
1996年 | 2168篇 |
1995年 | 1773篇 |
1994年 | 1723篇 |
1993年 | 1366篇 |
1992年 | 1292篇 |
1991年 | 1153篇 |
1990年 | 931篇 |
1989年 | 693篇 |
1988年 | 539篇 |
1987年 | 456篇 |
1986年 | 435篇 |
1985年 | 372篇 |
1984年 | 276篇 |
1983年 | 197篇 |
1982年 | 176篇 |
1981年 | 128篇 |
1980年 | 90篇 |
1979年 | 51篇 |
1978年 | 36篇 |
1976年 | 37篇 |
1975年 | 39篇 |
1974年 | 46篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Journal of Thermal Analysis and Calorimetry - The fire behavior of one flame-retardant PVC cable used as building wire is investigated in this work. Bench scale tests were performed using a cone... 相似文献
82.
83.
84.
85.
86.
87.
Xiaoshuang Luo Xinxian Qin Zhengyi Liu Dan Chen Weiwei Yu Kankan Zhang Deyu Hu 《Biomedical chromatography : BMC》2020,34(1):e4694
A simple and rapid analytical method for the detection of trifloxystrobin, trifloxystrobin acid and tebuconazole in soil, brown rice, paddy plants and rice hulls was established and validated by liquid chromatography with tandem mass spectrometry. Acceptable linearity (R2 > 0.99), accuracy (average recoveries of 74.3–108.5%) and precision (intra- and inter-day relative standard deviations of 0.9–8.8%) were obtained using the developed determination approach. In the field trial, the half-lives of trifloxystrobin and tebuconazole in paddy plants were 5.7–8.3 days in three locations throughout China, and the terminal residue concentrations of trifloxystrobin and tebuconazole were <100 and 500 μg/kg (maximum residue limits set by China), respectively, at harvest, which indicated that, based on the recommended application procedure, trifloxystrobin and tebuconazole are safe for use on rice. The risk assessment results demonstrated that, owing to risk quotient values of both fungicides being <100%, the potential risk of trifloxystrobin and tebuconazole on rice was acceptable for Chinese consumers. These data could provide supporting information for the proper use and safety evaluation of trifloxystrobin and tebuconazole in rice. 相似文献
88.
Wang Yingying Wang Donghui Shu Weiqing Sha Jingquan Zhang Haifeng 《Transition Metal Chemistry》2020,45(4):245-251
Transition Metal Chemistry - Two cubane-like complexes, namely [Ni4L4(HOEt)4] (1), [Co4L4(HOEt)4] (2) (H2L?=?(E)-2-((3-hydroxypropylimino)methyl)-6-methoxyphenol), were prepared under... 相似文献
89.
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
90.
We propose a system of time-division multiplexing(TDM) and spatial frequency-division multiplexing(SFDM). Extrinsic Fabry–Perot interferometric sensors are applied to detect weak acoustic signals. The broadband source is employed, the light from it is modulated by a pulse signal sequence and is efficiently amplified by semiconductor optical amplifiers. Experimental results show that the equivalent noise pressure spectrum level is-97.2 d B re 1 rad/√Hz below 1250 Hz, and the cross talk between two sensors in one TDM channel is-32.7 d B with a cavity length difference of 60 μm. The number of sensors in this multiplexing system can theoretically reach 160. 相似文献