全文获取类型
收费全文 | 22586篇 |
免费 | 3322篇 |
国内免费 | 1853篇 |
专业分类
化学 | 14734篇 |
晶体学 | 536篇 |
力学 | 888篇 |
综合类 | 171篇 |
数学 | 699篇 |
物理学 | 10733篇 |
出版年
2024年 | 25篇 |
2023年 | 141篇 |
2022年 | 306篇 |
2021年 | 419篇 |
2020年 | 598篇 |
2019年 | 607篇 |
2018年 | 593篇 |
2017年 | 723篇 |
2016年 | 951篇 |
2015年 | 905篇 |
2014年 | 930篇 |
2013年 | 2341篇 |
2012年 | 1273篇 |
2011年 | 1353篇 |
2010年 | 1114篇 |
2009年 | 1216篇 |
2008年 | 1315篇 |
2007年 | 1314篇 |
2006年 | 1267篇 |
2005年 | 1113篇 |
2004年 | 1085篇 |
2003年 | 965篇 |
2002年 | 1121篇 |
2001年 | 764篇 |
2000年 | 807篇 |
1999年 | 665篇 |
1998年 | 579篇 |
1997年 | 427篇 |
1996年 | 378篇 |
1995年 | 401篇 |
1994年 | 302篇 |
1993年 | 259篇 |
1992年 | 245篇 |
1991年 | 172篇 |
1990年 | 158篇 |
1989年 | 121篇 |
1988年 | 124篇 |
1987年 | 111篇 |
1986年 | 102篇 |
1985年 | 88篇 |
1984年 | 85篇 |
1983年 | 41篇 |
1982年 | 66篇 |
1981年 | 34篇 |
1980年 | 38篇 |
1979年 | 41篇 |
1978年 | 16篇 |
1977年 | 10篇 |
1976年 | 8篇 |
1973年 | 19篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Abstract Cascade size may affect phase stability under irradiation because of two distinct contributions: the replacement to displacement cross-section ratio depends on the deposited energy density; ballistic jumps which tend to disorder ordered compounds occur by bursts, while thermal jumps which restore long range order occur one by one. The latter effect cannot be handled by standard rate theory. A stochastic treatment of the problem, based on a Fokker Planck approximation of the relevant master equation is summarized. It is shown that the possible values of the long range order parameter under irradiation are not affected by the size of the cascade but that the respective stability of the former is cascade size sensitive. As a consequence, the stability diagram of phases under irradiation varies with the size of the cascades. A numerical example of this is given for the B2 structure. 相似文献
992.
993.
994.
995.
A microscopic model for calculating the optical response of incommensurately modulated phases in insulating crystals is presented. The dominant contribution to the dielectric permittivity tensor is shown to originate from the lowest-index reciprocal lattice vectors, thus proving the validity of the mesoscopic approach developed in several earlier studies. The expression for the mesoscopic Fourier component of the dielectric tensor is obtained. These results may be useful in relation to the controversial problem of the optical activity observed in the incommensurate phases of some A2BX4 family crystals. 相似文献
996.
997.
V. Sankara Sastry S. Kalavathy B. K. Guha R. Baskaran U. De J. Janaki 《Phase Transitions》2013,86(1-2):97-105
Electrical resistance measurements at low temperatures and high quasihydrostatic pressures on superconducting and non-superconducting varieties of Y0.8Ba1.2Cu2O5 (obtained by annealing in oxygen and air respectively) show striking anomalies in the vicinity of 100K and 40K. Arguments are presented to show that these anomalies as also the occurrence of T 's in the oxide superconductors either in the vicinity of 100K or of 40K are connected with their layered structure containing planes of Cu-O otahedral complexes. 相似文献
998.
In the majority of cases, the effects of ion implantation are confined close to the implant zone but, potentially, the resultant distortions and chemical modifications could catalyse relaxations extending into the bulk substrate. Such possibilities are rarely considered but the present data suggest that high dose ion implantation of ZnO has induced bulk changes. Surface implants with Cu and Tb strongly modified the low temperature bulk thermoluminescence properties generated by X-ray irradiation. Suggestions are proposed for the possible mechanisms for bulk relaxations and structural characteristics, which may indicate where such instability may occur in other lattice structures. 相似文献
999.
F.A. Mikailov E. Başaran E. Şentürk L. Tümbek T.G. Mammadov V.P. Aliev 《Phase Transitions》2013,86(12):1057-1064
The results of measurements of the dielectric constant of TlGaSe2 in temperature range of successive phase transitions are presented. An anomaly in the temperature dependence of the real part of dielectric constant in TlGaSe2 has been observed at about 242?K in addition to anomalies at 115, 108, and also near 65?K as reported in previous publications. The presence of temperature hysteresis effects in temperature interval between 115 and 242?K allowed making a conclusion about possible existence of an incommensurate phase in the mentioned temperature range. A model of succession of the structural phase transitions in TlGaSe2 has been suggested. 相似文献
1000.
研究猪肝样品中莱克多巴胺测定的样品前处理方法。样品直接用HCl酸解并超声提取,同时添加70%~72%的高浓度HClO_4对酸解样品进行蛋白沉淀,然后经MCX固相萃取柱净化后,用液相色谱-串联质谱法检测。用正交试验考察了酸的种类、浓度、提取时间、提取温度和HClO_4体积对提取效率的影响,最佳条件为:HCl浓度为0.2mol/L,提取时间为40min,提取温度为25℃,HClO_4用量为200μL。从0.5、5.0和10.0μg/kg添加水平检测结果可以看出,方法平均回收率为82.0%~102%,日内和日间精密度4%,符合国家标准对检验方法的要求。该方法灵敏度高,精密度好,成本低,能简便、快速对样品中的莱克多巴胺进行提取,实现对动物源性食品的快速监测。 相似文献