全文获取类型
收费全文 | 81篇 |
免费 | 11篇 |
国内免费 | 52篇 |
专业分类
化学 | 90篇 |
晶体学 | 1篇 |
数学 | 18篇 |
物理学 | 35篇 |
出版年
2023年 | 3篇 |
2022年 | 2篇 |
2021年 | 5篇 |
2020年 | 1篇 |
2019年 | 2篇 |
2017年 | 4篇 |
2016年 | 5篇 |
2015年 | 1篇 |
2014年 | 6篇 |
2013年 | 3篇 |
2012年 | 5篇 |
2011年 | 13篇 |
2010年 | 7篇 |
2009年 | 3篇 |
2008年 | 13篇 |
2007年 | 6篇 |
2006年 | 13篇 |
2005年 | 4篇 |
2004年 | 13篇 |
2003年 | 3篇 |
2002年 | 4篇 |
2001年 | 3篇 |
2000年 | 6篇 |
1999年 | 14篇 |
1993年 | 3篇 |
1992年 | 1篇 |
1990年 | 1篇 |
排序方式: 共有144条查询结果,搜索用时 0 毫秒
51.
激发态Na2与H2碰撞,使H2(V=3,J=3)得到布居,在H2和He总气压为800 Pa及温度为700 K的条件下,利用相干反斯托克斯拉曼散射(CARS)光谱技术研究了H2(3,3)与H2(He)间转动能量转移过程.改变CARS激光束与激发Na2的激光之间的延迟时间,测量He不同摩尔配比时H2(3,J)态CARS谱强度的时间演化,得到H2(3,3)的总弛豫速率系数分别为k3,3H2=(21士5)×10-3cm3·s-1和k3,3He=(5.6士1.6)×10-13cm3·s-1.测量H2(3,J)各转动态的相对CARS谱强度,由速率方程分析,得到H2(3,3)+H2→H2(3,J)+H2中,对于J=2,4,转移速率系数分别为(11±4)×10-13cm3·s-1和(8.2±3.1)×10-13cm3·s<sup>-1.在H2(3,3)+He→H2(3,J)+He中,对于J=2,4,转移速率系数分别为(3.1±1.2)×10-13cm3·s-1和(2.1士0.7)×1013cm3·s-1.对于H2(3,3),单量子弛豫|△J|=1约占该态总弛豫率的90%. 相似文献
52.
研究了实验室培养的小型水母弗洲指突水母(Blackfordia virginica)代谢过程中所释放的溶解有机物(DOM)及其吸收和荧光光谱特征的变化。与对照组海水相比,充分摄食后的水母在24h的代谢过程中向水体释放大量的溶解有机碳和总溶解态氮,有色溶解有机物的吸收系数a280也有显著增加。光谱斜率比值(SR)的增大和腐殖化指数(HIX)的降低,表明水母代谢产生的主要是腐殖化程度较弱的低分子量DOM。利用平行因子分析(PARAFAC)模型对三维荧光光谱进行解谱,识别出3个类腐殖质(C1-C3)和1个类蛋白质(C4)组分。发射波长在400nm以下的"海源"类腐殖质组分C2(<250,295/386nm)及类蛋白质组分C4(275/334nm)在代谢过程中有明显增加,表明它们是水母代谢释放的主要荧光物质;而发射波长在400nm以上的组分则变化不大。据此可将发射波长小于400nm与大于400nm的荧光组分强度和之间的比值,构建为DOM的浮游动物来源指标(ZIX),用于识别和示踪水环境中浮游动物代谢活动释放和产生的DOM。 相似文献
53.
分形多孔介质中的热传导 总被引:5,自引:0,他引:5
本文将多孔介质视为由骨架和空隙组成的二元混合介质,研究了多孔介质中的热传导过程,发现分形结构中的导热规律与孔隙的分布有关,存在着与实体导热完全不同的特征。计算表明,分形介质中的导热过程除了与基质(骨架)的分形维数有关外,还与基质率以及反映介质中热量传递动态过程有关。 相似文献
54.
55.
Jie Yang Ming-Hao Yao Dong-Hui Zhao Xiao-Shuai Zhang Rui-Mei Jin Yuan-Di Zhao Bo Liu 《Journal of nanoparticle research》2017,19(8):284
Nanogels have been widely used as multifunctional drug delivery carriers because of high water content, biocompatibility, and high loading capability. We designed and biosynthesized two triblock artificial polypeptides PC10A and PC10ARGD as vehicles for encapsulating hydrophobic materials. These polypeptides can form nanogels by self-assembly when the concentration is below 2% (w/v). The physical properties of nanogels, including size, surface potential, and targeting domain, are able to be tuned. Hydrophobic materials from molecular size to nano-size can be loaded into the polypeptide nanogels to form hybrid nanogels. Hydrophobic quantum dots CdSe@ZnS below 10 nM were loaded into the polypeptide nanogels by ultrasonic treatment. Encapsulation endows hydrophobic QDs with good tunability of size, water solubility, stability, targeting, and biocompatibility. PC10ARGD nanogels and PC10ARGD@QDs hybrid nanogels showed excellent biocompatibility, which the cellular viabilities of HeLa and MCF-7 cells treated with 1% PC10ARGD nanogels and PC10ARGD@QDs hybrid nanogels contained 20 nM QDs were above 90 and 80%, respectively. PC10ARGD@QDs hybrid nanogels with an arginine–glycine–aspartic acid motif present efficient receptor-mediated endocytosis in α v β 3 overexpressing HeLa cells but not in the control MCF-7 cells as analyzed by confocal microscopy. These results demonstrate that such polypeptide nanogels as nanocarriers are expected to have great potential applications in biomedicine. 相似文献
56.
Chen Hai-Hui Kuang Ren-Yun Wu Yan Guo Hong-Yu Xie Song-Hua Chen Dong-Hui Yi Xiu-Guang 《Journal of chemical crystallography》2021,51(4):516-522
Journal of Chemical Crystallography - A novel sodium complex [Na2(L)2(Phen)2(H2O)2]·2(H2O) (L?=?3-hydroxyquinoline-4-carboxylic acid anion; Phen?=?1,10-phenanthroline)... 相似文献
57.
58.
为探索介观尺度下固体燃料微粒的燃烧现象,本文提出采用光镊工具对活性炭微粒进行捕捉、悬浮、定位,再通过激光点燃,研究其着火及扩散燃烧特性.介观尺度燃烧室中,光镊捕捉7.0μm活性炭微粒的最低捕捉功率为3.2 mW,捕捉速率范围为103.7—70.0μm/s;活性炭微粒在静止气流中的最低点火功率为3.2 mW,颗粒的等效粒径、周长、面积和圆形度对最低点火功率影响甚微,点火延迟时间约48 ms,提高点火功率,点火延迟时间缩短,最小点火延迟时间小于6 ms;活性炭在着火后先发生无焰燃烧,紧接着发生有焰燃烧,无焰燃烧的扩散燃烧速率满足粒径平方直线规律,其燃烧速率范围为15.0—8.0μm/s;有焰燃烧的火焰面积和强度随燃烧时间发生闪烁,其闪烁频率约29.1 Hz.对于粒径为3.0μm的活性炭微粒,从加热到完全燃烧殆尽所需时间约0.648 s.结果表明:对于聚焦后的高能激光束点燃活性炭微粒的着火属于联合着火模式,在挥发份析出之前,活性炭非均相着火而发生无焰燃烧,挥发份析出后被点燃发生均相着火,火焰面始终保持圆形. 相似文献
59.
A Smoothing Newton Method for Semi-Infinite Programming 总被引:5,自引:0,他引:5
This paper is concerned with numerical methods for solving a semi-infinite programming problem. We reformulate the equations and nonlinear complementarity conditions of the first order optimality condition of the problem into a system of semismooth equations. By using a perturbed Fischer–Burmeister function, we develop a smoothing Newton method for solving this system of semismooth equations. An advantage of the proposed method is that at each iteration, only a system of linear equations is solved. We prove that under standard assumptions, the iterate sequence generated by the smoothing Newton method converges superlinearly/quadratically. 相似文献
60.
Experimental study on the chirped structure of the white-light continuum generation by femtosecond laser spectroscopy 下载免费PDF全文
The chirped structure of the white-light continuum generation (WLCG) pulse produced by focusing 800nm laser pulse with a pulse duration of 150fs (FWHM: full-width-at-half-maximum) onto a 2.4 mm thick sapphire plate was investigated by the optical Kerr gate technique with normal hexane as the optical Kerr gate medium. The observed WLCG was positively chirped, the measured anti-Stokes spectrum of WLCG ranges from 449 to 580nm with a temporal span of 2.56ps. When using metal reflecting mirrors to eliminate the group velocity dispersion (GVD) effect, we found that a span of 1.3ps still remained, indicating that the chirped pulse cannot be accounted for simply by GVD of the pulse propagation in the dispersive media. Our results suggest that the light-induced refractive index change due to the third-order nonlinear optical effect leads to an additional positive group velocity dispersion, which contributes to an important portion of the observed temporal broadening of the chirped WLCG. In addition to using reflective optical elements instead of dispersive optical elements, an effective way of reducing the chirp is to minimize the optical path length of the WLCG medium. 相似文献