全文获取类型
收费全文 | 250822篇 |
免费 | 1582篇 |
国内免费 | 402篇 |
专业分类
化学 | 114716篇 |
晶体学 | 3140篇 |
力学 | 13565篇 |
综合类 | 7篇 |
数学 | 39698篇 |
物理学 | 81680篇 |
出版年
2019年 | 1171篇 |
2018年 | 10432篇 |
2017年 | 11288篇 |
2016年 | 6590篇 |
2015年 | 2422篇 |
2014年 | 2540篇 |
2013年 | 6435篇 |
2012年 | 9315篇 |
2011年 | 18802篇 |
2010年 | 11514篇 |
2009年 | 11635篇 |
2008年 | 16450篇 |
2007年 | 20079篇 |
2006年 | 5604篇 |
2005年 | 11977篇 |
2004年 | 7910篇 |
2003年 | 7315篇 |
2002年 | 5318篇 |
2001年 | 4488篇 |
2000年 | 3629篇 |
1999年 | 2613篇 |
1998年 | 2285篇 |
1997年 | 2169篇 |
1996年 | 2012篇 |
1995年 | 1949篇 |
1994年 | 1931篇 |
1993年 | 1749篇 |
1992年 | 2018篇 |
1991年 | 2154篇 |
1990年 | 1944篇 |
1989年 | 1962篇 |
1988年 | 1915篇 |
1987年 | 1811篇 |
1986年 | 1738篇 |
1985年 | 2248篇 |
1984年 | 2405篇 |
1983年 | 1961篇 |
1982年 | 2140篇 |
1981年 | 2029篇 |
1980年 | 1948篇 |
1979年 | 2116篇 |
1978年 | 2294篇 |
1977年 | 2081篇 |
1976年 | 2160篇 |
1975年 | 2057篇 |
1974年 | 2107篇 |
1973年 | 2139篇 |
1972年 | 1379篇 |
1971年 | 1222篇 |
1968年 | 1177篇 |
排序方式: 共有10000条查询结果,搜索用时 296 毫秒
991.
992.
N. B. Valetova L. L. Semenycheva I. S. Il’ichev A. N. Artemov D. F. Grishin 《Russian Journal of Applied Chemistry》2007,80(5):818-821
Features of radical polymerization of styrene in the presence of (diphenylbutadiene)tricarbonylchromium were studied. 相似文献
993.
V. M. Arzhavitin 《Technical Physics》2003,48(6):797-799
The stressed state of in metallic composite systems is analyzed. It is analytically shown that the temperature dependences of the internal friction in the composites may have extrema that are caused by internal stresses. The analytical results are supported by the experimental temperature dependences of the internal friction in (Cu-13% Sn)-30% Nb and Cu-1.3% Cr composites. 相似文献
994.
R. Brunner R. Meisels F. Kuchar M. ElHassan J. Bird K. Ishibashi 《Physica E: Low-dimensional Systems and Nanostructures》2004,21(2-4):491
The properties of open quantum dots are examined in magneto-transport. The quantum dots are prepared from a two-dimensional electron system (2DES) in AlGaAs/GaAs by lateral gate structures. These quantum dots are open, i.e. they are still connected to the surrounding 2DES regions. The low magnetic field magnetoresistance shows peak structures. These structures can be related to semi-classical ballistic trajectories in the confining potential of a dot. The calculations of different confining potentials (abrupt “hard-wall” and parabolic “soft-wall”) are compared with the experimental results. The experiments are better described by a soft-wall potential. 相似文献
995.
996.
We investigate the connection between the dynamics of
synchronization and the modularity on complex networks. Simulating
the Kuramoto's model in complex networks we determine patterns of
meta-stability and calculate the modularity of the partition these
patterns provide. The results indicate that the more stable the
patterns are, the larger tends to be the modularity of the partition
defined by them. This correlation works pretty well in homogeneous
networks (all nodes have similar connectivity) but fails when
networks contain hubs, mainly because the modularity is never
improved where isolated nodes appear, whereas in the synchronization
process the characteristic of hubs is to have a large stability when
forming its own community. 相似文献
997.
S. Mentus Dijana Jelić Veselinka Grudić 《Journal of Thermal Analysis and Calorimetry》2007,90(2):393-397
Thermal decomposition of lanthanum nitrate to lanthanum oxide was carried out by both temperature programmed heating (TPH)
and citrate-gel combustion. The temperature programmed heating was carried out under flow of oxidizing (air), neutral (nitrogen)
and reducing (25 vol.% hydrogen+argone mixture) gases, and the processes were controlled by simultaneous thermogravimetry
and differential thermal analysis. It was shown that hydrogen atmosphere helps to reduce temperatures of all decomposition
steps. The results of TPH were utilized to check the nature of residues in the products of lanthanum nitrate-to-oxide conversion
performed via citrate-gel combustion technique. 相似文献
998.
999.
M. C. Caracoche J. A. Martínez P. C. Rivas M. A. Taylor A. F. Pasquevich S. Barolin O. A. de Sanctis 《Hyperfine Interactions》2007,179(1-3):87-93
The hyperfine quadrupole interaction at Hf sites in films and powders of 14 mol% CaO–HfO2 and 20 mol% CaO–HfO2 has been determined as a function of temperature. Results indicate the formation of a cubic solid solution and other microstructures assigned to the ?1 (CaHf4O9) and ?2 (Ca6Hf19O44) phases. Dynamical effects on the electric field gradient reveal the existence of oxygen vacancies movements in the solid solution. The thermal behavior of the relaxation constant observed in films allowed the determination of activation energies of 0.54 eV and 0.70 eV for the 14 mol% and 20 mol% CaO doped hafnias, respectively. The influence of the microdomains and the stability of the cubic solid solution are discussed. 相似文献
1000.