首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   58篇
  免费   1篇
  国内免费   3篇
化学   14篇
晶体学   1篇
力学   1篇
数学   6篇
物理学   40篇
  2021年   2篇
  2013年   2篇
  2012年   3篇
  2010年   4篇
  2009年   3篇
  2008年   2篇
  2007年   2篇
  2006年   4篇
  2005年   2篇
  2004年   1篇
  2003年   1篇
  2002年   2篇
  2001年   3篇
  2000年   6篇
  1999年   2篇
  1998年   1篇
  1997年   2篇
  1996年   3篇
  1995年   1篇
  1994年   5篇
  1993年   3篇
  1992年   3篇
  1991年   1篇
  1990年   2篇
  1987年   1篇
  1974年   1篇
排序方式: 共有62条查询结果,搜索用时 828 毫秒
1.
2.
3.
4.
种植沙生植物--沙棘改善内蒙古地区生态环境   总被引:2,自引:0,他引:2  
结合内蒙古地区现状,对沙棘的生物学和生态学特性、沙棘属植物化学成分和微量元素及种植沙生植物——沙棘的重要性和必要性进行了详细的研究和探讨。研究表明,沙棘属植物具有极强的生态适应性并富含多种营养成分和生物活性物质,并以耐干旱、耐瘠薄、萌蘖及固氮能力强等特点被称为治理非宜林地水土流失、改善生态环境的先锋树种。种植沙棘是治理内蒙古脆弱生态环境最经济、最有效的措施,是贫瘠的不毛之地发展经济、增加收入的经济树种。另外.种植沙棘的技术简便,容易掌握,投资少,见效快。  相似文献   
5.
以内蒙古地区沙棘果实为原料,研究了提取黄色素的工艺条件,同时对该色素的性质进行了初步探讨。结果表明,以95%的乙醇溶液作浸提剂,提取的黄色素浓度最高,工艺流程简单易行,且无毒,无污染。对提取的黄色素进行的性质试验表明,沙棘黄色素对光、热具有较好的稳定性,适用于酸性或弱碱性的食品中,葡萄糖、氧化剂(H2O2)、还原剂(Na2SO3)等食品添加剂均无明显影响以上结果为这种优良天然色素的开发与应用提供了参考。  相似文献   
6.
Point-contact Andreev-reflection (PCAR) experiments were performed in the Fe-1111 layered superconductor LaFeAsO0.9F0.1 with resistive T c on ∼ 27 K. The observation of two pairs of peaks in the low-temperature Andreev-reflection spectra clearly indicates the presence of two order parameters. The behavior of the two gaps as a function of temperature, obtained by fitting the conductance curves by means of the generalized two-band Blonder-Tinkham-Klapwijk model, shows some anomalies. A theoretical analysis performed within the two-band Eliashberg theory with a generic electron-boson coupling can reproduce the low-temperature value of the two gaps but generally fails in giving a satisfactory fit of their overall temperature dependence, indicating the rich and complex physics of these newly discovered superconductors.   相似文献   
7.
We present the results of the first directional point-contact spectroscopy experiments in high-quality MgB2 single crystals. Because of the directionality of the current injection into the samples, the application of a magnetic field allowed us to separate the contributions of the sigma and pi bands to the total conductance of our point contacts. By using this technique, we were able to obtain the temperature dependency of each gap independent of the other. The consequent, strong reduction of the error on the value of the gap amplitude as a function of temperature allows a stricter test of the predictions of the two-band model for MgB2.  相似文献   
8.
Cross-linking ability is possible with the oligonucleotide-tethered, monofunctional trans-Pt(II) complex shown. It was synthesized by a novel solid-phase approach comprising conjugation of immobilized tetrathymidylic acid with a trans-a(2)Pt(II) building unit, ammonolysis, and transformation of the resulting complex (R=1-N-cyclohexylmethylthyminate) into the chloro derivative (R=Cl). a=NH(2)CH(3), T=thymine.  相似文献   
9.
We present the first observation of the dc and ac Josephson effect in MgB(2) break junctions. The junctions, obtained at 4.2 K in high-quality, high-density polycrystalline metallic MgB(2) samples, show a nonhysteretic dc Josephson effect. By irradiating the junctions with microwaves we observe clear Shapiro steps spaced by the ideal Delta V value. The temperature dependence of the dc Josephson current and the dependence of the height of the steps on the microwave power are obtained. These results directly prove the existence of pairs with charge 2e in MgB(2) and give evidence of the superconductor-normal metal-superconductor weak link character of these junctions.  相似文献   
10.
We calculate the possible interaction between a superconductor and the static Earth’s gravitational fields, making use of the gravito-Maxwell formalism combined with the time-dependent Ginzburg–Landau theory. We try to estimate which are the most favorable conditions to enhance the effect, optimizing the superconductor parameters characterizing the chosen sample. We also give a qualitative comparison of the behavior of high–Tc and classical low–Tc superconductors with respect to the gravity/superfluid interplay.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号