全文获取类型
收费全文 | 295316篇 |
免费 | 25869篇 |
国内免费 | 17762篇 |
专业分类
化学 | 161919篇 |
晶体学 | 3951篇 |
力学 | 14669篇 |
综合类 | 26篇 |
数学 | 36978篇 |
物理学 | 121404篇 |
出版年
2021年 | 2448篇 |
2020年 | 2909篇 |
2019年 | 3609篇 |
2018年 | 4262篇 |
2017年 | 4828篇 |
2016年 | 6369篇 |
2015年 | 5149篇 |
2014年 | 6319篇 |
2013年 | 14236篇 |
2012年 | 12521篇 |
2011年 | 15665篇 |
2010年 | 15073篇 |
2009年 | 15078篇 |
2008年 | 12335篇 |
2007年 | 12012篇 |
2006年 | 11471篇 |
2005年 | 10826篇 |
2004年 | 11185篇 |
2003年 | 9514篇 |
2002年 | 9146篇 |
2001年 | 9739篇 |
2000年 | 7458篇 |
1999年 | 6481篇 |
1998年 | 5390篇 |
1997年 | 5271篇 |
1996年 | 5276篇 |
1995年 | 5413篇 |
1994年 | 5402篇 |
1993年 | 5311篇 |
1992年 | 5224篇 |
1991年 | 4880篇 |
1990年 | 4434篇 |
1989年 | 4370篇 |
1988年 | 4375篇 |
1987年 | 3660篇 |
1986年 | 3497篇 |
1985年 | 4003篇 |
1984年 | 4371篇 |
1983年 | 3211篇 |
1982年 | 3878篇 |
1981年 | 3654篇 |
1980年 | 3594篇 |
1979年 | 3399篇 |
1978年 | 3551篇 |
1977年 | 3602篇 |
1976年 | 4007篇 |
1975年 | 2995篇 |
1974年 | 2978篇 |
1973年 | 3279篇 |
1972年 | 2302篇 |
排序方式: 共有10000条查询结果,搜索用时 95 毫秒
81.
Martín D. Safe 《Journal of Graph Theory》2020,93(2):268-298
A graph is concave-round if its vertices can be circularly enumerated so that the closed neighborhood of each vertex is an interval in the enumeration. In this study, we give a minimal forbidden induced subgraph characterization for the class of concave-round graphs, solving a problem posed by Bang-Jensen, Huang, and Yeo [SIAM J. Discrete Math., 13 (2000), pp. 179–193]. In addition, we show that it is possible to find one such forbidden induced subgraph in linear time in any given graph that is not concave-round. As part of the analysis, we obtain characterizations by minimal forbidden submatrices for the circular-ones property for rows and for the circular-ones property for rows and columns and show that, also for both variants of the property, one of the corresponding forbidden submatrices can be found (if present) in any given matrix in linear time. We make some final remarks regarding connections to some classes of circular-arc graphs. 相似文献
82.
JETP Letters - The leading role of the bremsstrahlung at resonant Compton scattering of a hard X-ray photon by a multielectron atom has been theoretically predicted. This result can be important in... 相似文献
83.
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
84.
International Applied Mechanics - Problems of parametric optimization of rod structure stated in terms of the nonlinear programming problem are considered. Use is made of the method of projection... 相似文献
85.
86.
87.
88.
89.
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
90.