全文获取类型
收费全文 | 24664篇 |
免费 | 4172篇 |
国内免费 | 3047篇 |
专业分类
化学 | 18214篇 |
晶体学 | 307篇 |
力学 | 1420篇 |
综合类 | 240篇 |
数学 | 2762篇 |
物理学 | 8940篇 |
出版年
2024年 | 64篇 |
2023年 | 500篇 |
2022年 | 954篇 |
2021年 | 888篇 |
2020年 | 1054篇 |
2019年 | 1065篇 |
2018年 | 877篇 |
2017年 | 870篇 |
2016年 | 1246篇 |
2015年 | 1240篇 |
2014年 | 1488篇 |
2013年 | 1898篇 |
2012年 | 2324篇 |
2011年 | 2300篇 |
2010年 | 1576篇 |
2009年 | 1585篇 |
2008年 | 1710篇 |
2007年 | 1444篇 |
2006年 | 1315篇 |
2005年 | 1089篇 |
2004年 | 892篇 |
2003年 | 717篇 |
2002年 | 701篇 |
2001年 | 577篇 |
2000年 | 411篇 |
1999年 | 462篇 |
1998年 | 331篇 |
1997年 | 298篇 |
1996年 | 287篇 |
1995年 | 250篇 |
1994年 | 214篇 |
1993年 | 209篇 |
1992年 | 173篇 |
1991年 | 161篇 |
1990年 | 110篇 |
1989年 | 94篇 |
1988年 | 75篇 |
1987年 | 65篇 |
1986年 | 63篇 |
1985年 | 61篇 |
1984年 | 27篇 |
1983年 | 26篇 |
1982年 | 14篇 |
1981年 | 17篇 |
1980年 | 13篇 |
1979年 | 13篇 |
1959年 | 13篇 |
1958年 | 11篇 |
1957年 | 18篇 |
1956年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
101.
We consider the 3D Navier–Stokes equation with generalized impermeability boundary conditions. As auxiliary results, we prove the local in time existence of a strong solution (‘strong’ in a limited sense) and a theorem on structure. Then, taking advantage of the boundary conditions, we formulate sufficient conditions for regularity up to the boundary of a weak solution by means of requirements on one of the eigenvalues of the rate of deformation tensor. Finally, we apply these general results to the case of an axially symmetric flow with zero angular velocity. 相似文献
102.
Y.-Q. Peng J.-H. Yang F.-P. Lu 《Applied Physics A: Materials Science & Processing》2006,83(2):305-311
Under the assumption of Gaussian energy distributions of the lowest unoccupied molecular orbital (LUMO) and the highest occupied
molecular orbital (HOMO), analytical expressions of generalized Einstein relation for electron and hole transport in doped
organic semiconductor thin films are developed. Numerical calculations show that, although traditional Einstein relation still
holds for low carrier concentrations, that is, the diffusion-coefficient-to-mobility ratio in units of kBT/q, with kB the Boltzmann’s constant, T the temperature and q the elementary charge, equals 1. But when the electron (hole) concentration
is high, the diffusion-coefficient-to-mobility ratio for electrons (holes) changes strongly with the electron (hole) concentration,
the doping level, the mean energy of LUMOs (HOMOs) of the dopant ELd (EHd) and the host EL (EH), as well as their variances. Dopants with ELd<EL (EHd>EH) affect the diffusion-coefficient-to-mobility ratio mainly in the range of low and middle carrier concentrations, while those
with ELd>EL (EHd<EH) have significant effect only in the range of high carrier concentrations. It was found that there can be a maximum in the
dependence of the diffusion-coefficient-to-mobility ratio on the quasi-Fermi energy or carrier concentration exist, for appropriate
values of the doping level, the mean energy and variance of LUMO or HOMO states of the dopant.
PACS 71.20.Rv; 72.90.+y; 73.50.-h 相似文献
103.
在应变速率为5.56×10-5s-1—5.56×10-3s-1的范围内,在不同温度下(从223K至773K),对3004铝合金进行系列拉伸试验,探索其锯齿屈服规律;通过激活能的计算、内耗研究、微观组织观察和能谱分析,探讨锯齿屈服的机理与物理本质.结果表明,3004铝合金在形变过程中会出现动态应变时效现象;发现了一种“反常”的锯齿屈服现象:在出现锯齿屈服的温区内,存在锯齿屈服临界应变量转变温度Tt,
关键词:
动态应变时效
锯齿屈服
铝合金
内耗 相似文献
104.
Hong Ming ZHANG Xian Hong WANG Xiao Jiang ZHAO Ji LI Fo Song WANG 《中国化学快报》2006,17(4):437-440
A novel method for the preparation of oligothiophene molecular wires is described via a bi-directional solid-phase synthesis. Using an alternating sequence of bromination and Stille coupling reactions, oligomers were obtained up to the heptamer in excellent yield and purity. 相似文献
105.
106.
107.
108.
用射频磁控溅射法在80℃衬底温度下制备出MgxZn1-xO(x=0.16)薄膜,用X射线衍射(XRD)、光致发光(PL)和透射谱研究了退火温度对MgxZn1-xO薄膜结构和光学性质的影响.测量结果显示,MgxZn1-xO薄膜为单相六角纤锌矿结构,并且具有沿c轴的择优取向;随着退火温度的升高,(002)XRD峰强度、平均晶粒尺寸和紫外PL峰强度增大,(002)XRD峰半高宽(F
关键词:
xZn1-xO薄膜')" href="#">MgxZn1-xO薄膜
射频磁控溅射
退火 相似文献
109.
Kyung Hwa Hong Jong Lyoul Park In Hwan Sul Ji Ho Youk Tae Jin Kang 《Journal of Polymer Science.Polymer Physics》2006,44(17):2468-2474
Polyvinyl alcohol (PVA) nanofibers containing Ag nanoparticles were prepared by electrospinning PVA/silver nitrate (AgNO3) aqueous solutions, followed by short heat treatment, and their antimicrobial activity was investigated for wound dressing applications. Since PVA is a water soluble and biocompatible polymer, it is one of the best materials for the preparation of wound dressing nanofibers. After heat treatment at 155 °C for 3 min, the PVA/AgNO3 nanofibers became insoluble, while the Ag+ ions therein were reduced so as to produce a large number of Ag nanoparticles situated preferentially on their surface. The residual Ag+ ions were reduced by subsequent UV irradiation for 3 h. The average diameter of the Ag nanoparticles after the heat treatment was 5.9 nm and this value increased slightly to 6.3 nm after UV irradiation. It was found that most of the Ag+ ions were reduced by the simple heat treatment. The PVA nanofibers containing Ag nanoparticles showed very strong antimicrobial activity. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2468–2474, 2006 相似文献
110.
Jiří Rais 《Journal of Radioanalytical and Nuclear Chemistry》2006,270(3):709-710
Dr. Miroslav Kyrš, DrSc. passed away prematurely and unexpectedly in August 2006 at age of 75. He was a leading person of
the Czech radiochemistry during the second half of the 20th century and his results have of world-wide impact. His diligence,
intelligence and permanent activity led him to be at first a laboratory chief and subsequently for about 25 years to be a
chief of the Radiochemical Department of Czech Nuclear Research Institute (NRI) at Řež near Prague. 相似文献