全文获取类型
收费全文 | 279171篇 |
免费 | 1923篇 |
国内免费 | 526篇 |
专业分类
化学 | 129082篇 |
晶体学 | 3577篇 |
力学 | 14852篇 |
综合类 | 9篇 |
数学 | 42697篇 |
物理学 | 91403篇 |
出版年
2019年 | 1442篇 |
2018年 | 10623篇 |
2017年 | 11452篇 |
2016年 | 7067篇 |
2015年 | 2747篇 |
2014年 | 3137篇 |
2013年 | 7783篇 |
2012年 | 10379篇 |
2011年 | 19883篇 |
2010年 | 12406篇 |
2009年 | 12542篇 |
2008年 | 17388篇 |
2007年 | 20861篇 |
2006年 | 6730篇 |
2005年 | 12768篇 |
2004年 | 8742篇 |
2003年 | 8052篇 |
2002年 | 6086篇 |
2001年 | 5631篇 |
2000年 | 4446篇 |
1999年 | 3302篇 |
1998年 | 2800篇 |
1997年 | 2712篇 |
1996年 | 2592篇 |
1995年 | 2348篇 |
1994年 | 2316篇 |
1993年 | 2094篇 |
1992年 | 2426篇 |
1991年 | 2555篇 |
1990年 | 2323篇 |
1989年 | 2309篇 |
1988年 | 2300篇 |
1987年 | 2194篇 |
1986年 | 2060篇 |
1985年 | 2629篇 |
1984年 | 2824篇 |
1983年 | 2264篇 |
1982年 | 2474篇 |
1981年 | 2371篇 |
1980年 | 2224篇 |
1979年 | 2465篇 |
1978年 | 2629篇 |
1977年 | 2433篇 |
1976年 | 2503篇 |
1975年 | 2362篇 |
1974年 | 2388篇 |
1973年 | 2438篇 |
1972年 | 1629篇 |
1971年 | 1437篇 |
1968年 | 1403篇 |
排序方式: 共有10000条查询结果,搜索用时 250 毫秒
71.
João Marcos G. Barbosa Milenna K. Fernandes Rodrigues Lurian C. David Taynara C. e Silva Danielly A. Fortuna Lima Naiara Z. Pereira Emmanuel B. D'Alessandro Anselmo E. de Oliveira Paulo H. Jorge da Cunha Maria Clorinda S. Fioravanti Nelson R. Antoniosi Filho 《Biomedical chromatography : BMC》2020,34(11):e4935
An innovative volatolomic approach employs the detection of biomarkers present in cerumen (earwax) to identify cattle intoxication by Stryphnodendron rotundifolium Mart., Fabaceae (popularly known as barbatimão). S. rotundifolium is a poisonous plant with the toxic compound undefined and widely distributed throughout the Brazilian territory. Cerumen samples from cattle of two local Brazilian breeds (‘Curraleiro Pé-Duro’ and ‘Pantaneiro’) were collected during an experimental intoxication protocol and analyzed using headspace (HS)/GC–MS followed by multivariate analysis (genetic algorithm for a partial least squares, cluster analysis, and classification and regression trees). A total of 106 volatile organic metabolites were identified in the cerumen samples of bovines. The intoxication by S. rotundifolium influenced the cerumen volatolomic profile of the bovines throughout the intoxication protocol. In this way, it was possible to detect biomarkers for cattle intoxication. Among the biomarkers, 2-octyldecanol and 9-tetradecen-1-ol were able to discriminate all samples between intoxicated and nonintoxicated bovines. The cattle intoxication diagnosis by S. rotundifolium was accomplished by applying the cerumen analysis using HS/GC–MS, in an easy, accurate, and noninvasive way. Thus, the proposed bioanalytical chromatography protocol is a useful tool in veterinary applications to determine this kind of intoxication. 相似文献
72.
J. Conrad J. Cohen-Tanugi L. E. Strigari 《Journal of Experimental and Theoretical Physics》2015,121(6):1104-1135
The launch of the gamma-ray telescope Fermi Large Area Telescope (Fermi-LAT) started a pivotal period in indirect detection of dark matter. By outperforming expectations, for the first time a robust and stringent test of the paradigm of weakly interacting massive particles (WIMPs) is within reach. In this paper, we discuss astrophysical targets for WIMP detection and the challenges they present, review the analysis tools which have been employed to tackle these challenges, and summarize the status of constraints on and the claimed detections in the WIMP parameter space. Methods and results will be discussed in comparison to Imaging Air Cherenkov Telescopes. We also provide an outlook on short term and longer term developments. 相似文献
73.
S. V. Panin I. V. Vlasov V. P. Sergeev B. B. Ovechkin P. O. Marushchak Sunder Ramasubbu P. S. Lyubutin V. V. Titkov 《Physical Mesomechanics》2015,18(3):261-272
The structure and properties of 12Cr1MoV steel irradiated with a zirconium ion beam were studied by optical microscopy, scanning electron microscopy, and micro- and nanoindentation. It is shown that the modification covers the entire cross-section of the irradiated specimens to a depth of 1 mm. The data on irradiation-induced structural changes are used to interpret the changes in mechanical properties of the irradiated specimens under static and cyclic loading. Particular attention is given to analysis of strain estimation by the digital image correlation method. 相似文献
74.
75.
76.
77.
E. A. Andrianova V. D. Davidenko V. F. Tsibulskiy S. V. Tsibulskiy 《Physics of Atomic Nuclei》2015,78(11):1252-1258
Influence of the nuclear energy structure, the conditions of fuel burnup, and accumulation of new fissile isotopes from the raw isotopes on the main parameters of a closed fuel cycle is considered. The effects of the breeding ratio, the cooling time of the spent fuel in the external fuel cycle, and the separation of the breeding area and the fissile isotope burning area on the parameters of the fuel cycle are analyzed. 相似文献
78.
79.
Valiullina Z. R. Galeeva A. M. Miftakhov M. S. 《Russian Journal of Organic Chemistry》2021,57(9):1461-1465
Russian Journal of Organic Chemistry - The Reformatsky reaction of (3R,4R)-4-acetoxy-3-((1R)-1-{[tert-butyl(dimethyl)silyl]oxy}ethyl)azetidin-2-one with ethyl 4-bromo-3-oxopentanoate gave... 相似文献
80.