全文获取类型
收费全文 | 116117篇 |
免费 | 19607篇 |
国内免费 | 12606篇 |
专业分类
化学 | 80237篇 |
晶体学 | 1446篇 |
力学 | 7390篇 |
综合类 | 737篇 |
数学 | 13161篇 |
物理学 | 45359篇 |
出版年
2024年 | 393篇 |
2023年 | 2277篇 |
2022年 | 3965篇 |
2021年 | 4226篇 |
2020年 | 4616篇 |
2019年 | 4531篇 |
2018年 | 3907篇 |
2017年 | 3678篇 |
2016年 | 5621篇 |
2015年 | 5466篇 |
2014年 | 6663篇 |
2013年 | 8699篇 |
2012年 | 10350篇 |
2011年 | 10775篇 |
2010年 | 7256篇 |
2009年 | 6932篇 |
2008年 | 7438篇 |
2007年 | 6824篇 |
2006年 | 6212篇 |
2005年 | 5207篇 |
2004年 | 3932篇 |
2003年 | 3096篇 |
2002年 | 2835篇 |
2001年 | 2366篇 |
2000年 | 2074篇 |
1999年 | 2311篇 |
1998年 | 2017篇 |
1997年 | 1837篇 |
1996年 | 1994篇 |
1995年 | 1606篇 |
1994年 | 1547篇 |
1993年 | 1233篇 |
1992年 | 1124篇 |
1991年 | 1033篇 |
1990年 | 847篇 |
1989年 | 587篇 |
1988年 | 499篇 |
1987年 | 395篇 |
1986年 | 396篇 |
1985年 | 342篇 |
1984年 | 260篇 |
1983年 | 169篇 |
1982年 | 148篇 |
1981年 | 111篇 |
1980年 | 79篇 |
1979年 | 49篇 |
1978年 | 35篇 |
1976年 | 39篇 |
1975年 | 35篇 |
1974年 | 47篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
131.
132.
Zhong-Qing Wang 《Journal of Mathematical Analysis and Applications》2002,274(1):374-403
An orthogonal system of rational functions is discussed. Some inverse inequalities, imbedding inequalities and approximation results are obtained. Two model problems are considered. The stabilities and convergences of proposed rational spectral schemes and rational pseudospectral schemes are proved. The techniques used in this paper are also applicable to other problems on the whole line. Numerical results show the efficiency of this approach. 相似文献
133.
The object of this note is to prove the followingTheorem Let{a_n}and{b_n}be sequences of real numbers such that0<∑∑a_n~2<+∞and0<∑b_n~2<+∞.Then we have the inequalitysum from m=1 to∞sum from n=1 to∞a_mb_n/m+n<{sum from n=1 to∞(π-θ/n~(1/2)a_n~2}~1/2{sum from n=1 to∞(π-θ/n~(1/2)b_n~2}~1/2 (1)whereθ=3/2~(1/2)-1=1.121320343. 相似文献
134.
利用室温下压电调制反射光(PzR)谱技术系统测量了N掺杂浓度为0.0%—3%的分子束外延生长GaNxAs1-x薄膜,并对图谱中所观察的光学跃迁进行了指认.在GaN0.005As0.995和GaN0.01As0.99薄膜的PzR谱中观察到此前只在椭圆偏振谱中才看到的N掺杂相关能态E1+Δ1+ΔN.当N掺杂浓度达到
关键词:
压电调制反射光谱(PzR)
xAs1-x薄膜')" href="#">GaNxAs1-x薄膜
分子束外延(MBE) 相似文献
135.
136.
137.
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
138.
139.
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
140.
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