全文获取类型
收费全文 | 1479篇 |
免费 | 55篇 |
国内免费 | 383篇 |
专业分类
化学 | 1017篇 |
晶体学 | 2篇 |
力学 | 79篇 |
综合类 | 5篇 |
数学 | 347篇 |
物理学 | 467篇 |
出版年
2016年 | 5篇 |
2015年 | 13篇 |
2014年 | 2篇 |
2013年 | 15篇 |
2012年 | 20篇 |
2011年 | 349篇 |
2010年 | 161篇 |
2009年 | 152篇 |
2008年 | 19篇 |
2007年 | 33篇 |
2006年 | 32篇 |
2005年 | 104篇 |
2004年 | 300篇 |
2003年 | 128篇 |
2002年 | 112篇 |
2001年 | 133篇 |
2000年 | 28篇 |
1999年 | 29篇 |
1998年 | 37篇 |
1997年 | 28篇 |
1996年 | 23篇 |
1995年 | 21篇 |
1994年 | 23篇 |
1993年 | 50篇 |
1992年 | 42篇 |
1991年 | 20篇 |
1990年 | 10篇 |
1989年 | 12篇 |
1988年 | 2篇 |
1986年 | 4篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1982年 | 2篇 |
1979年 | 1篇 |
1975年 | 1篇 |
1972年 | 1篇 |
1971年 | 2篇 |
1955年 | 1篇 |
排序方式: 共有1917条查询结果,搜索用时 15 毫秒
141.
WANG Bo LIU ZhengWei HAN YunKun LEI ZhenXin LUO YangPing & HAN ZhanWen National Astronomical Observatories/Yunnan Observatory Chinese Academy of Sciences Kunming China Key Laboratory for the Structure Evolution of Celestial Objects Graduate University of Chinese Academy of Sciences Beijing 《中国科学:物理学 力学 天文学(英文版)》2010,(3)
Type Ia supernovae (SNe Ia) play an important role in diverse areas of astrophysics, from the chemical evolution of galaxies to observational cosmology. However, the nature of the progenitors of SNe Ia is still unclear. In this paper, according to a detailed binary population synthesis study, we obtained SN Ia birthrates and delay times from different progenitor models, and compared them with observations. We find that the Galactic SN Ia birthrate from the double-degenerate (DD) model is close to those infe... 相似文献
142.
YING LungAn 《中国科学 数学(英文版)》2010,(4)
In this paper,we study the TE,TM model by using the decompositions of the vector fields in 2-D bounded multiply connected domains and 2-D unbounded domains,respectively.We find that the TE,TM model and the Darwin models are equivalent if we assume some regularity of the initial data. 相似文献
143.
Hong She Wang Wei Xing Zhao 《中国化学快报》2011,22(8):911-914
An efficient magnesium bistrifluoromethanesulfonimide[Mg(NTf_2)_2]catalyzed hydroalkylation of aromatic olefins with 1,3- diketones under solvent-free conditions has been developed.The reactions proceed smoothly to give the desired products in good yields in short reaction times. 相似文献
144.
WEI ChangGuo & WANG LiGuang School of Mathematical Sciences Ocean University of China Qingdao China School of Mathematical Sciences Qufu Normal University Qufu 《中国科学 数学(英文版)》2011,(2)
In this paper we give a certain classification theorem of extensions of the torus algebra up to isomorphism and also show that the K 0 -group K 0 (E) and the semigroup V (E) are two complete invariants of such extension algebras. 相似文献
145.
Air-breathing mode laser propulsion experiment with a long-pulse transversely excited(TE) CO2 laser is carried out,and its ignition problem is solved with the ignition needle of lightcraft.Owing to the ignition needle,an order of magnitude reduction in the ignition threshold is demonstrated.The result is compared with previous study.The momentum coupling coefficient is also measured in the experiment and its dependence upon laser pulse energy(6-14 J) and pulse width(20,32,and 40μs) is discussed. 相似文献
146.
High-spin states in nucleus 139Pm have been studied using the reaction 116Cd(27Al,4n)139Pm.Two dipole cascades have been found.Spin and parity assignments were based on the Directional Correlation of Oriented Nuclei(DCO) ratios and systematic behavior in neighboring odd-proton nuclei.The level structures of 139Pm are compared with those of the N =78 isotone 141Eu in which two dipole bands have been confirmed as magnetic rotational bands.The close similarity between them suggests that the dipole bands in 139... 相似文献
147.
WANG FengYu School of Mathematical Sciences Beijing Normal University Beijing China 《中国科学 数学(英文版)》2010,(4)
By establishing the intrinsic super-Poincar'e inequality,some explicit conditions are presented for diffusion semigroups on a non-compact complete Riemannian manifold to be intrinsically ultracontractive.These conditions,as well as the resulting uniform upper bounds on the intrinsic heat kernels,are sharp for some concrete examples. 相似文献
148.
WANG Nai-Xing LI Ji-Sheng ZHU Dao-BenInstitute of Chemistry Chinese Academy of Sciences Beijing China 《中国化学》1996,14(2):167-170
Ammo acid derivatives react with C60 at 110-120℃to form adduct compounds.The products were isolated by column chromatography and were identified by FD-MS,UV-Vis,FT-IR and 13C NMR spectroscopies. 相似文献
149.
TUNG Chen-Ho ZHANG Li-Ping LI YiInstitute of Photographic Chemistry Chinese Academy of Sciences Beijing China 《中国化学》1996,14(4):377-380
A diad compound 3β(bicyclo[2,2,1]hepta-2,5-diene-2-methylcarboxylate-3-carboxy)-an-drost-5-en-17-one (NBD-S-ONE) was synthesized and its photochemistry was examined. Irradiation of NBD-S-ONE in acetonitrile at λ > 300 nm selectively excited the keto chromophore. After intersystem crossing, the triplet energy of the keto group was transferred to the NBD group with 18.6% efficiency via a through-bond mechanism, resulting in the isomerization of the latter group to the quadricyclane group. 相似文献
150.
分析了制作高功率连续激光反射镜材料的热性能、缺陷及其加工工艺, 提出了制作高功率激光反射镜应考虑的几个关键问题: 反射镜材料的综合热性能比值S, 材料的微观结构、缺陷的大小和晶向的选择, 以及加工工艺的设计。并介绍了实验结果。 相似文献