全文获取类型
收费全文 | 1107篇 |
免费 | 209篇 |
国内免费 | 104篇 |
专业分类
化学 | 747篇 |
晶体学 | 16篇 |
力学 | 86篇 |
综合类 | 3篇 |
数学 | 99篇 |
物理学 | 469篇 |
出版年
2024年 | 2篇 |
2023年 | 22篇 |
2022年 | 16篇 |
2021年 | 27篇 |
2020年 | 37篇 |
2019年 | 54篇 |
2018年 | 32篇 |
2017年 | 28篇 |
2016年 | 53篇 |
2015年 | 47篇 |
2014年 | 43篇 |
2013年 | 84篇 |
2012年 | 118篇 |
2011年 | 129篇 |
2010年 | 86篇 |
2009年 | 76篇 |
2008年 | 75篇 |
2007年 | 51篇 |
2006年 | 50篇 |
2005年 | 42篇 |
2004年 | 47篇 |
2003年 | 23篇 |
2002年 | 22篇 |
2001年 | 21篇 |
2000年 | 30篇 |
1999年 | 31篇 |
1998年 | 23篇 |
1997年 | 16篇 |
1996年 | 26篇 |
1995年 | 21篇 |
1994年 | 10篇 |
1993年 | 14篇 |
1992年 | 10篇 |
1991年 | 12篇 |
1990年 | 12篇 |
1989年 | 6篇 |
1988年 | 1篇 |
1987年 | 7篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1978年 | 2篇 |
1976年 | 1篇 |
1973年 | 2篇 |
1972年 | 1篇 |
1971年 | 1篇 |
排序方式: 共有1420条查询结果,搜索用时 375 毫秒
71.
Based on the theories of nonlinear continuum mechanics, piezoelectricity and elastic waves in solids, theoretical analysis of Bleustein-Gulyaev surface acoustic wave propagation in a prestressed layered piezoelectric structure are described. Numerical calculations are performed for the case that the layer and the substrate are identical LiNbO(3) except that they are polarized in opposite directions. It is found that an almost linear behavior of the relative change in phase velocity versus the initial stress is obtained for both surface electrically free and shorted cases. Potential applications in the design of acoustic wave devices are suggested. 相似文献
72.
Ambrose D Arroyo C Bachman M Connor D Eckhause M Graessle S Hancock AD Hartman K Hebert M Hoff CH Hoffmann GW Irwin GM Kane JR Kanematsu N Kuang Y Lang K Lee R Martin RD McDonough J Milder A Molzon WR Pommot-Maia M Riley PJ Ritchie JL Rubin PD Vassilakopoulos VI 《Physical review letters》2000,84(7):1389-1392
We report results from Experiment 871, performed at the BNL AGS, of a measurement of the branching ratio K(0)(L)-->&mgr;(+)&mgr;(-) with respect to the CP-violating mode K(0)(L)-->pi(+)pi(-). This experiment detected over 6200 candidate &mgr;(+)&mgr;(-) events, a factor of 6 more than that seen in all previous measurements combined. The resulting branching ratio gamma(K(0)(L)-->&mgr;(+)&mgr;(-))/gamma(K(0)(L)-->pi(+)pi(-)) = (3. 474+/-0.057)x10(-6) leads to a branching fraction B(K(0)(L)-->&mgr;(+)&mgr;(-)) = (7.18+/-0.17)x10(-9), which is consistent with the current world average, and reduces the uncertainty in this decay mode by a factor of 3. 相似文献
73.
Lu‐Feng Zou Kuang Shen Yao Fu Qing‐Xiang Guo 《Journal of Physical Organic Chemistry》2007,20(10):754-763
Experimental studies showed that sulfur radicals play the vital role in petroleum formation. 1 Sulfur‐ centered radicals also exhibit activities in antioxidant functions. Here we conduct a theoretical investigation of their precursor‐disulfides. By investigation into substituent effect on sulfur? sulfur bond dissociation enthalpies (S? S BDEs), we would like to find the most effective provider for sulfur radicals. In the present work, 50 alpha‐substituted disulfides and 16 para‐substituted aryl disulfides are studied systematically, with the general formula XS‐SX or HS‐SX. The substituent effect on S? S BDEs is found to be very eminent, ranging from 33.2 to 75.0 kcal/mol for alpha‐substituted disulfide, and from 43.7 to 59.7 kcal/mol for para‐substituted phenyl disulfides. We also evaluate the performance of 44 density functional methods to get an accurate prediction. A further study indicates that substituents play a major role in radical energies, instead of molecule energies, which is substantiated by the good linearity between XS‐SX bond dissociation enthalpy (BDE) and HS‐SX BDE. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
74.
Liu Haiqing Wang Xiangwei Kuang Chunxia Li Lei Zhai Yunyun 《Journal of Solid State Electrochemistry》2018,22(11):3579-3587
Journal of Solid State Electrochemistry - Ionic conductivity is an important separator parameter influencing the cycle life and rate capability of lithium-ion batteries (LIBs). To improve the ionic... 相似文献
75.
76.
77.
Pd OECC薄膜的表面增强拉曼散射 总被引:2,自引:1,他引:1
利用较高检测灵敏度的 SERS技术 ,对浓度较低的 Pd OECC吸附在银表面上的薄层在室温下进行了拉曼谱的测量。得到 Pd OECC在强光破坏前后的 SERS光谱。在强光照射下 ,β-胡萝卜素分子的 SERS光谱的散射强度明显降低 ,且线宽增加 ,说明强光照射不但改变了β-胡萝卜素的构象 ,而且也改变了 β-胡萝卜素分子所处的微环境。其结果与强光照射前后吸收光谱的变化相一致。另外 ,没有观察到 Pd OECC薄层与银镜相互作用的其它新振动峰或Pd OECC中其它振动峰峰型的变化 ,可见 Pd OECC在银镜表面保持原来的状态 ,这证明SERS技术在光合作用光破坏机理研究中的可行性 相似文献
78.
79.
80.
R. Bernabei P. Belli F. Montecchia F. Nozzoli F. Cappella A. Incicchitti D. Prosperi R. Cerulli C.J. Dai H.L. He H.H. Kuang J.M. Ma X.H. Ma X.D. Sheng Z.P. Ye R.G. Wang Y.J. Zhang 《The European Physical Journal C - Particles and Fields》2008,53(2):205-213
The channeling effect of low energy ions along the crystallographic axes and planes of NaI(Tl) crystals is discussed in the
framework of corollary investigations on WIMP dark matter candidates. In fact, the modeling of this existing effect implies
a more complex evaluation of the luminosity yield for low energy recoiling Na and I ions. In the present paper related phenomenological
arguments are developed and possible implications are discussed at some extent.
PACS 95.35.+d 相似文献