全文获取类型
收费全文 | 114573篇 |
免费 | 19351篇 |
国内免费 | 12200篇 |
专业分类
化学 | 78328篇 |
晶体学 | 1407篇 |
力学 | 7548篇 |
综合类 | 764篇 |
数学 | 13701篇 |
物理学 | 44376篇 |
出版年
2024年 | 240篇 |
2023年 | 2173篇 |
2022年 | 2458篇 |
2021年 | 3798篇 |
2020年 | 4471篇 |
2019年 | 4395篇 |
2018年 | 3778篇 |
2017年 | 3536篇 |
2016年 | 5523篇 |
2015年 | 5261篇 |
2014年 | 6476篇 |
2013年 | 8415篇 |
2012年 | 10192篇 |
2011年 | 10838篇 |
2010年 | 7315篇 |
2009年 | 7106篇 |
2008年 | 7576篇 |
2007年 | 6936篇 |
2006年 | 6382篇 |
2005年 | 5393篇 |
2004年 | 4051篇 |
2003年 | 3202篇 |
2002年 | 3091篇 |
2001年 | 2453篇 |
2000年 | 2156篇 |
1999年 | 2344篇 |
1998年 | 2028篇 |
1997年 | 1845篇 |
1996年 | 2000篇 |
1995年 | 1579篇 |
1994年 | 1526篇 |
1993年 | 1219篇 |
1992年 | 1120篇 |
1991年 | 1025篇 |
1990年 | 816篇 |
1989年 | 598篇 |
1988年 | 493篇 |
1987年 | 396篇 |
1986年 | 382篇 |
1985年 | 334篇 |
1984年 | 245篇 |
1983年 | 158篇 |
1982年 | 141篇 |
1981年 | 108篇 |
1980年 | 84篇 |
1979年 | 48篇 |
1978年 | 48篇 |
1976年 | 40篇 |
1975年 | 34篇 |
1974年 | 47篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
181.
通过反应磁控溅射过程中的等离子体发射光谱,研究了制备ZnO薄膜的沉积温度、氧气流量比例R=O2/(O2+Ar)对Zn和O原子发射光谱的影响,并结合ZnO薄膜的结构和物理性能,探讨了沉积温度在ZnO薄膜生长中的作用.研究结果显示:当R≥0.75%时, Zn的溅射产额随R的增加基本呈线性下降规律.当R介于10%—50%时,氧含量的变化相对平缓,有利于ZnO薄膜生长的稳定性控制.Zn原子发射光谱强度随沉积温度的变化可以分为三个阶段.当沉积温度低于250℃时,发射光谱强
关键词:
ZnO
薄膜生长
反应磁控溅射
等离子体发射光谱 相似文献
182.
183.
184.
设计性、研究性实验对学生创新能力的培养 总被引:6,自引:0,他引:6
根据设计性、研究性实验的特点,从几个方面、不同的角度,阐述了设计性、研究性实验对学生创新能力培养的作用与意义。 相似文献
185.
186.
Junxiang Zhang Yabin Dong Haihong Wang Jiangrui Gao 《量子光学学报》2006,12(B08):74-74
The quantum coherence effects of the transition Fe = 2←→Fg = 3 depending on the polarization of the coupling and probe beam are observed in a Cs vapor cell. The splitting of electromagnetically induced transparency (EIT) window is observed when the degeneracy of two-level system is broken using a magnetic field. It is also shown that the splitted transparency points of two of three windows are shifted with the intensity of magnetic field ( i. e. Zeeman splitting in the upper and lower levels ) increasing. On the contrary, when we fix the intensity of magnetic field, and increase the Rabi frequency of the coupling beam, the splitted transparency peaks become wider. A qualitative agreement between experiment and theory is found. 相似文献
187.
188.
Gang Wang Xiulin Zhu Zhenping Cheng Jian Zhu 《Journal of polymer science. Part A, Polymer chemistry》2006,44(9):2912-2921
A series of (di)picolinic acids and their derivates are investigated as novel complexing tridentate or bidentate ligands in the iron‐mediated reverse atom transfer radical polymerization of methyl methacrylate in N,N‐dimethylformamide at 100 °C with 2,2′‐azobisisobutyrontrile as an initiator. The polymerization rates and polydispersity indices (1.32–1.8) of the resulting polymers are dependent on the structures of the ligands employed. Different iron complexes may be involved in iron‐mediated reverse atom transfer radical polymerization, depending on the type of acid used. 1H NMR spectroscopy has been used to study the structure of the resulting polymers. Chain‐extension reactions have been performed to further confirm the living nature of this catalytic system. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2912–2921, 2006 相似文献
189.
L. Tong Y. Tian Q. Y. Wang Y. S. Ling 《International Journal of Infrared and Millimeter Waves》2006,27(9):1307-1314
The paper introduces a special system calibration technology in s-parameters measurement of microwave and millimeter wave
devices. The 8-term errors module is built by analyzing the signals flowing in the measurement system. Then the calibration
technology using non-standard kits is designed on the base. Finally, the experiment using the calibration technology is introduced. 相似文献
190.
Qipeng Guo Fei Chen Ke Wang Ling Chen 《Journal of Polymer Science.Polymer Physics》2006,44(21):3042-3052
An amphiphilic poly(ethylene oxide)‐block‐poly(dimethylsiloxane) (PEO–PDMS) diblock copolymer was used to template a bisphenol A type epoxy resin (ER); nanostructured thermoset blends of ER and PEO–PDMS were prepared with 4,4′‐methylenedianiline (MDA) as the curing agent. The phase behavior, crystallization, hydrogen‐bonding interactions, and nanoscale structures were investigated with differential scanning calorimetry, Fourier transform infrared spectroscopy, transmission electron microscopy, and small‐angle X‐ray scattering. The uncured ER was miscible with the poly(ethylene oxide) block of PEO–PDMS, and the uncured blends were not macroscopically phase‐separated. Macroscopic phase separation took place in the MDA‐cured ER/PEO–PDMS blends containing 60–80 wt % PEO–PDMS diblock copolymer. However, the composition‐dependent nanostructures were formed in the cured blends with 10–50 wt % PEO–PDMS, which did not show macroscopic phase separation. The poly(dimethylsiloxane) microdomains with sizes of 10–20 nm were dispersed in a continuous ER‐rich phase; the average distance between the neighboring microdomains was in the range of 20–50 nm. The miscibility between the cured ER and the poly(ethylene oxide) block of PEO–PDMS was ascribed to the favorable hydrogen‐bonding interaction. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 3042–3052, 2006 相似文献