全文获取类型
收费全文 | 187864篇 |
免费 | 2823篇 |
国内免费 | 517篇 |
专业分类
化学 | 100997篇 |
晶体学 | 2222篇 |
力学 | 7646篇 |
综合类 | 12篇 |
数学 | 21480篇 |
物理学 | 58847篇 |
出版年
2020年 | 1577篇 |
2019年 | 1529篇 |
2018年 | 1961篇 |
2017年 | 1927篇 |
2016年 | 3456篇 |
2015年 | 2294篇 |
2014年 | 3316篇 |
2013年 | 8066篇 |
2012年 | 6561篇 |
2011年 | 8043篇 |
2010年 | 5489篇 |
2009年 | 5288篇 |
2008年 | 7356篇 |
2007年 | 7342篇 |
2006年 | 6895篇 |
2005年 | 6315篇 |
2004年 | 5553篇 |
2003年 | 4786篇 |
2002年 | 4690篇 |
2001年 | 5049篇 |
2000年 | 3909篇 |
1999年 | 2994篇 |
1998年 | 2604篇 |
1997年 | 2550篇 |
1996年 | 2436篇 |
1995年 | 2318篇 |
1994年 | 2339篇 |
1993年 | 2183篇 |
1992年 | 2499篇 |
1991年 | 2443篇 |
1990年 | 2258篇 |
1989年 | 2225篇 |
1988年 | 2146篇 |
1987年 | 2058篇 |
1986年 | 1953篇 |
1985年 | 2628篇 |
1984年 | 2731篇 |
1983年 | 2253篇 |
1982年 | 2442篇 |
1981年 | 2320篇 |
1980年 | 2273篇 |
1979年 | 2393篇 |
1978年 | 2537篇 |
1977年 | 2420篇 |
1976年 | 2426篇 |
1975年 | 2331篇 |
1974年 | 2374篇 |
1973年 | 2314篇 |
1972年 | 1494篇 |
1971年 | 1359篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
Mohammad Azam Saud I. Al-Resayes Agata Trzesowska-Kruszynska Rafal Kruszynski S.F. Adil N.K. Lokanath 《Journal of Saudi Chemical Society》2019,23(5):636-641
A new derivative of dioxouranium(VI) salen complex, [UO2(L)(pyridine)], where [L = N,N′-Bis(2-hydroxybenzylidene)-2,2-dimethyl-1,3-propanediamine] is synthesized and characterized by elemental analysis (C, H, N), FT-IR, ESI-MS spectrometry, UV/Vis, fluorescence, 1H and 13C NMR spectroscopy and thermal gravimetric (TG) study. Furthermore, the single crystal X-ray diffraction measurements of the complex were carried out at 100 and 273 K. The crystal structure measurements revealed that the complex has distorted pentagonal bipyramidal geometry with uranium atom located at the centre and bonded to two phenoxy oxygen and two azomethine nitrogen in tetradenate fashion and one nitrogen from pyridine making it seven coordinated. In addition, the photoluminescence property of the complex was also recorded. 相似文献
42.
Adly M. E. Gedawy E. M. El-Malah A. A. El-Telbany F. A. 《Russian Journal of Organic Chemistry》2019,55(8):1189-1196
Russian Journal of Organic Chemistry - Selenopheno[2,3-d]pyrimidine- and selenopheno[2,3-d][1,2,3]triazine-containing compounds were synthesized starting from... 相似文献
43.
Saleh Z. M. Nasser H. Özkol E. Günöven M. Abak K. Canli S. Bek A. Turan R. 《Journal of nanoparticle research》2015,17(10):1-12
Journal of Nanoparticle Research - Plasmonic interfaces consisting of silver nanoparticles of different sizes (50–100&;nbsp;nm) have been processed by the self-assembled dewetting... 相似文献
44.
45.
Dr. Sebastian Lars Müller Xinglong Zhou Dr. Peter Leonard Oxana Korzhenko Dr. Constantin Daniliuc Prof. Dr. Frank Seela 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(12):3077-3090
Silver-mediated α-dC–Ag+–β-dC hybrid base pairs decorated with 5-iodo- or 5-octadiynyl residues are well accommodated in duplex DNA. A strong Tm increase and favorable thermodynamic data for duplex DNA were observed after addition of silver ions. The phenomenon is particularly obvious when both nucleobases of the base pairs are functionalized. Neither the position of the base pair, nor the type of 5-substituent had a negative influence. On the contrary, functionalization of conventional silver-mediated β-dC–Ag+–β-dC homo base pairs showed a negative impact induced by the bulky substituents. To this end, cytosine modified 12-mer oligodeoxynucleotides were prepared by solid-phase synthesis employing new α-anomeric 2′-deoxycytidine phosphoramidites. A multigram scale synthesis was developed for 5-iodo-α-d -2′-deoxycytidine ( 1 ) employing the direct glycosylation of cytosine with Hoffer's α-d -halogenose followed by separation of anomeric DMT nucleosides. Regarding base-pair stability and functionalization silver-mediated α/β-dC hybrid base pairs were found to be superior to β/β-dC homo pairs. According to their extraordinary properties, they might find applications in DNA diagnostics, material science, or nanotechnology. 相似文献
46.
47.
48.
49.
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
50.