全文获取类型
收费全文 | 37938篇 |
免费 | 7393篇 |
国内免费 | 12570篇 |
专业分类
化学 | 28754篇 |
晶体学 | 1285篇 |
力学 | 2710篇 |
综合类 | 1597篇 |
数学 | 5970篇 |
物理学 | 17585篇 |
出版年
2024年 | 86篇 |
2023年 | 379篇 |
2022年 | 1156篇 |
2021年 | 1284篇 |
2020年 | 1253篇 |
2019年 | 1257篇 |
2018年 | 1154篇 |
2017年 | 1601篇 |
2016年 | 1366篇 |
2015年 | 1827篇 |
2014年 | 2155篇 |
2013年 | 2955篇 |
2012年 | 2848篇 |
2011年 | 3307篇 |
2010年 | 3030篇 |
2009年 | 3316篇 |
2008年 | 3530篇 |
2007年 | 3201篇 |
2006年 | 3241篇 |
2005年 | 2812篇 |
2004年 | 2234篇 |
2003年 | 1627篇 |
2002年 | 1704篇 |
2001年 | 1847篇 |
2000年 | 1887篇 |
1999年 | 1177篇 |
1998年 | 657篇 |
1997年 | 552篇 |
1996年 | 446篇 |
1995年 | 423篇 |
1994年 | 439篇 |
1993年 | 429篇 |
1992年 | 375篇 |
1991年 | 297篇 |
1990年 | 286篇 |
1989年 | 270篇 |
1988年 | 225篇 |
1987年 | 179篇 |
1986年 | 179篇 |
1985年 | 123篇 |
1984年 | 137篇 |
1983年 | 128篇 |
1982年 | 89篇 |
1981年 | 95篇 |
1980年 | 69篇 |
1979年 | 58篇 |
1978年 | 34篇 |
1977年 | 18篇 |
1974年 | 18篇 |
1965年 | 21篇 |
排序方式: 共有10000条查询结果,搜索用时 93 毫秒
151.
For vertical-cavity surface-emitting lasers (VCSELs) with polarization-rotated feedback, there exist several synchronization
types such as synchronizations between total powers and synchronizations between separate polarization modes. Based on the
two-mode rate equations, we study and compare numerically the performances of different synchronization types. Our results
show that three synchronization types exhibit good performances when their synchronization conditions are satisfied. They
are the complete synchronization between total powers, complete synchronization between x-polarized modes, and generalized synchronization between x-polarized and y-polarized modes. The former two types are sensitive to the injection rate and spontaneous emission, while the third type
is contrary. Synchronization type with the best performance may switch from one to another, with changing of injection rate
and spontaneous emission factor. 相似文献
152.
CHEN Yue WANG Xuan-jun CONG Xian-ling ZHANG Pei-yin WU Xiu-li WEI Hong-fei WANG Li WAN Min WANG Li-ying YU Yong-li 《高等学校化学研究》2006,22(6):712-716
IntroductionClassical swine fever(CSF), included in the listA of the Office International des Epizooties(OIE), is ahighly contagious disease of domestic pigs and is con-sidered as the mostharmful disease occurring in pigs allover the world[1]. Outbreaks o… 相似文献
153.
154.
155.
Total Dose Radiation Tolerance of Phase Change Memory Cell with GeSbTe Alloy 总被引:1,自引:0,他引:1 下载免费PDF全文
Phase change memory (PCM) cell array is fabricated by a standard complementary metal-oxide-semiconductor process and the subsequent special fabrication technique. A chalcogenide Ge2Sb2Te5 film in thickness 50hm deposited by rf magnetron sputtering is used as storage medium for the PCM cell. Large snap-back effect is observed in current-voltage characteristics, indicating the phase transition from an amorphous state (higher resistance state) to the crystalline state (lower resistance state). The resistance of amorphous state is two orders of magnitude larger than that of the crystalline state from the resistance measurement, and the threshold current needed for phase transition of our fabricated PCM cell array is very low (only several μA). An x-ray total dose radiation test is carried out on the PCM cell array and the results show that this kind of PCM cell has excellent total dose radiation tolerance with total dose up to 2 ×10^6 rad(Si), which makes it attractive for space-based applications. 相似文献
156.
157.
本文研究具有受迫性的广义二维KdV-Burgers方程的周期行波解,为了获得周期行波解的存在唯一性定理,使唤用特定系数法和Schauder不动点定理获得了受迫广义KdV-Burgers方程周期行波解存在唯一性的条件.并获得了周期行波解的一些先验估计式. 相似文献
158.
The equivalence of three (2 1)-dimensional soliton equations is proved, and the quite generalsolutionswitha some arbitrary functions of x, t and y respectively are obtained. By selecting the arbitrary functions, many specialtypes of the localized excitations like the solitoff solitons, multi-dromion solutions, lump, and multi-ring soliton solutionsare obtained. 相似文献
159.
160.
1 Introduction Inrecentyears,boththetheoreticalandexperimentalinvestigationsonlasercoolingandtrappinghavebecomeoneofthemajorfieldsinatomic,molecularandoptical physics[1~ 8] .Thedevelopmentoflasercoolingandtrappingtechnologyisimportantfortheapplicationssu… 相似文献