全文获取类型
收费全文 | 1650篇 |
免费 | 261篇 |
国内免费 | 164篇 |
专业分类
化学 | 1238篇 |
晶体学 | 19篇 |
力学 | 68篇 |
综合类 | 6篇 |
数学 | 176篇 |
物理学 | 568篇 |
出版年
2024年 | 1篇 |
2023年 | 41篇 |
2022年 | 69篇 |
2021年 | 66篇 |
2020年 | 83篇 |
2019年 | 72篇 |
2018年 | 56篇 |
2017年 | 56篇 |
2016年 | 77篇 |
2015年 | 88篇 |
2014年 | 100篇 |
2013年 | 119篇 |
2012年 | 160篇 |
2011年 | 179篇 |
2010年 | 110篇 |
2009年 | 96篇 |
2008年 | 102篇 |
2007年 | 98篇 |
2006年 | 84篇 |
2005年 | 68篇 |
2004年 | 65篇 |
2003年 | 32篇 |
2002年 | 31篇 |
2001年 | 10篇 |
2000年 | 24篇 |
1999年 | 27篇 |
1998年 | 31篇 |
1997年 | 19篇 |
1996年 | 23篇 |
1995年 | 15篇 |
1994年 | 16篇 |
1993年 | 5篇 |
1992年 | 7篇 |
1991年 | 7篇 |
1990年 | 12篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1987年 | 6篇 |
1986年 | 9篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 3篇 |
1982年 | 1篇 |
1981年 | 1篇 |
排序方式: 共有2075条查询结果,搜索用时 15 毫秒
131.
One-pot synthesis of benzylacetamide from oxime can be carried out in 80–95% yield at 35–40 °C under ultrasound irradiation. This method provided several advantages such as simple work-up procedure, shorter reaction time and higher yield. 相似文献
132.
L.H. KongY.L. Gao T.T. SongQ.J. Zhai 《Journal of magnetism and magnetic materials》2011,323(16):2165-2169
Structure and magnetic properties of Nb-doped (FeZrB)100−xNbx alloy are investigated by X-ray diffraction (XRD), differential scanning calorimetry and vibrating sample magnetometer. The fully amorphous structure of the as-quenched ribbons is confirmed by the XRD pattern. With increasing Nb, the glass transition temperature and the onset crystallization temperature are increased, indicating increased stability of the amorphous structure. For x=1, the saturation magnetization of the ribbons is 125.7 emu/g and the optimized annealing temperature increases from 550 to 630 °C. The morphology of the crystallized phases is observed by scanning electron microscopy. The results show that nanocrystalline α-Fe grains are dispersed in the amorphous matrix. 相似文献
133.
Ye Wu Irene Ling Li Ling Fu Jian pang Zhai Shuang Chen Ruan 《Applied Surface Science》2009,255(23):9409-9412
Excimer laser emitting at 248 nm is applied to produce microstructures on the surface of aluminum alloy. The surface morphology shows that hotspots and thermal fluidic structures both come to light. Two possible mechanisms of hotspots formation are proposed: near-field diffraction and interference, and extremely fast rapid thermal annealing. And for the formation of thermal fluidic pattern structure, a thin film model is applied. 相似文献
134.
135.
Wenguang Zhai 《中国科学A辑(英文版)》1999,42(11):1173-1183
Thek-dimensional Piatetski-Shapiro prime number problem fork⩾3 is studied. Let π(x
1
c
1,⋯,c
k
) denote the number of primesp withp⩽x,
, where 1<c
1<⋯<c
k
are fixed constants. It is proved that π(x;c
1,⋯,c
k
) has an asymptotic formula ifc
1
−1
+⋯+c
k
−1
>k−k/(4k
2+2).
Project supported by the National Natural Science Foundation of China (Grant No. 19801021) and the Natural Science Foundation
of Shandong Province (Grant No.Q98A02110). 相似文献
136.
137.
138.
The liquid to solid transformation of ternary Ag42.4Cu21.6Sb36 eutectic alloy was accomplished in an ultrasonic field with a frequency of 35 kHz, and the growth mechanism of this ternary eutectic was examined. Theoretical calculations predict that the sound intensity in the liquid phase at the solidification interface increases gradually as the interface moves up from the sample bottom to its top. The growth mode of (ε θ Sb) ternary eutectic exhibits a transition of "divorced eutectic- mixture of anomalous and regular structures-regular eutectic" along the sample axis due to the inhomogeneity of sound field distribution. In the top zone with the highest sound intensity, the cavitation effect promotes the three eutectic phases to nucleate independently, while the acoustic streaming efficiently suppresses the coupled growth of eutectic phases. In the meantime, the ultrasonic field accelerates the solute transportation at the solid-liquid interface, which reduces the solute solubility of eutectic phases. 相似文献
139.
X. Sheng Y. Zhao J. Zhai L. Jiang D. Zhu 《Applied Physics A: Materials Science & Processing》2007,87(4):715-719
The electro-hydrodynamic (EHD) technique has been successfully applied for manufacturing ZnO photoanode in dye sensitized
solar cells (DSSCs). Porous structure of ZnO film after calcinations was beneficial to the absorption of dye and infiltration
of electrolyte. By using ionic liquid as an electrolyte, a high short-circuit photocurrent density of 12.1 mA/cm2 was attained and the overall photo-to-electric energy conversion efficiency (η) was 3.4% under an AM-1.5 illumination at
100 mW/cm2. At the same time, the influence factors on the solar cell performance, such as the concentrations of polyvinyl alcohol (PVA)
during EHD process and light intensity were discussed.
PACS 81.07.Bc; 84.60.Jt; 81.15.Rs 相似文献
140.
In this report, we demonstrate the efficient generation of collinearly propagating photon pairs in a bulk periodically poled potassium titanyl phosphate pumped by a cw laser. The detected coincidence counts are more than 7400/s with 3.58 mW pump power in a Hanbury-Brown-Twiss-type experiment. The estimated photon pair production rate is about 0.73 MHz/mW. This is very promising for some applications, such as quantum key distribution, proof of the Bell-inequality, preparation of single photon states in broadband wave packets, Franson-type interference and so on. 相似文献