全文获取类型
收费全文 | 392篇 |
免费 | 25篇 |
国内免费 | 89篇 |
专业分类
化学 | 263篇 |
晶体学 | 2篇 |
力学 | 7篇 |
综合类 | 2篇 |
物理学 | 119篇 |
综合类 | 113篇 |
出版年
2023年 | 2篇 |
2022年 | 7篇 |
2021年 | 3篇 |
2020年 | 9篇 |
2019年 | 9篇 |
2018年 | 11篇 |
2017年 | 5篇 |
2016年 | 10篇 |
2015年 | 9篇 |
2014年 | 16篇 |
2013年 | 22篇 |
2012年 | 27篇 |
2011年 | 14篇 |
2010年 | 14篇 |
2009年 | 21篇 |
2008年 | 30篇 |
2007年 | 30篇 |
2006年 | 33篇 |
2005年 | 38篇 |
2004年 | 30篇 |
2003年 | 31篇 |
2002年 | 27篇 |
2001年 | 13篇 |
2000年 | 11篇 |
1999年 | 11篇 |
1998年 | 8篇 |
1997年 | 7篇 |
1996年 | 14篇 |
1995年 | 7篇 |
1994年 | 7篇 |
1993年 | 10篇 |
1992年 | 7篇 |
1991年 | 7篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1986年 | 1篇 |
1984年 | 1篇 |
排序方式: 共有506条查询结果,搜索用时 388 毫秒
61.
Xiaofeng Shi Yong‐Hyok Kwon Jun Ma Ronger Zheng Chunyan Wang H.‐D. Kronfeldt 《Journal of Raman spectroscopy : JRS》2013,44(1):41-46
A surface‐enhanced Raman scattering (SERS) active substrate for the detection of polycyclic aromatic hydrocarbons (PAHs) was developed, which used 25, 27‐dimercaptoacetic acid‐26, 28‐dihydroxy‐4‐terbutyl calix[4]arene (DMCX) to functionalize a gold colloid film. This SERS‐active substrate prepared by self‐assembly method exhibits a high sensitivity, especially for the detection of PAHs. With the use of this SERS‐active substrate and with the application of the shifted excitation Raman difference spectroscopy (SERDS) technique, Raman signals of pyrene and anthracene in aqueous solutions at low concentration level (500 pM) can be obtained. Moreover, because PAHs are blocked from being directly adsorbed on gold colloid by DMCX and the photochemical reactions of adsorbates are avoided, the Raman bands of PAHs adsorbed on DMCX‐fuctionalized gold colloid film can be one‐to‐one correspondence with those of solid PAHs, and additionally, this SERS‐active substrate can be easily cleaned and reused. The obtained results demonstrate that the DMCX‐functionalized gold colloid films prepared by self‐assembly method have great potential to be developed to an in situ PAHs detection substrate. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
62.
63.
64.
Dr. So-Yeon Park Sehoon Han Dr. Younghoon Kim Prof. Sohee Jung Prof. Dong Hoe Kim Dr. Gill Sang Han Prof. Hyun Suk Jung 《Chemphyschem》2019,20(20):2657-2661
Multiple exciton generation (MEG) has great potential to improve the Shockley-Queisser (S-Q) efficiency limitation for colloidal quantum dot (CQD) solar cells. However, MEG has rarely been observed in CQD solar cells because of the loss of carriers through the transport mechanism between adjacent QDs. Herein, we demonstrate that excess charge carriers produced via MEG can be efficiently extracted using monolayer PbS QDs. The monolayer PbS QDs solar cells exhibit α=1 in the light intensity dependence of the short-circuit current density Jsc (Jsc∝Iα) and an internal quantum efficiency (IQE) value of 100 % at 2.95 eV because of their very short charge extraction path. In addition, the measured MEG threshold is 2.23 times the bandgap energy (Eg), which is the lowest value in PbS QD solar cells. We believe that this approach can provide a simple method to find suitable CQD materials and design interface engineering for MEG. 相似文献
65.
Edyta Podstawka Pawe Kafarski Leonard M. Proniewicz 《Journal of Raman spectroscopy : JRS》2008,39(12):1726-1739
A comparative study of molecular structures of five L ‐proline (L ‐Pro) phosphonodipeptides: L ‐Pro‐NH‐C(Me,Me)‐PO3H2 (P1), L ‐Pro‐NH‐C(Me,iPr)‐PO3H2 (P2), L ‐Pro‐L ‐NH‐CH(iBu)‐PO3H2 (P3), L ‐Pro‐L ‐NH‐CH(PA)‐PO3H2 (P4) and L ‐Pro‐L ‐NH‐CH(BA)‐PO3H2 (P5) has been carried out using Raman and absorption infrared techniques of molecular spectroscopy. The interpretation of the obtained spectra has been supported by density functional theory calculations (DFT) at the B3LYP; 6–31 + + G** level using Gaussian 2003 software. The surface‐enhanced Raman scattering (SERS) on Ag‐sol in aqueous solutions of these phosphonopeptides has also been investigated. The surface geometry of these molecules on a silver colloidal surface has been determined by observing the position and relative intensity changes of the Pro ring, amide, phosphonate and so‐called spacer (−R) groups vibrations of the enhanced bands in their SERS spectra. Results show that P4 and P5 adsorb onto the silver as anionic molecules mainly via the amide bond (∼1630, ∼1533, ∼1248, ∼800 and ∼565 cm−1), Pro ring (∼956, ∼907 and ∼876 cm−1) and carboxylate group (∼1395 and ∼909 cm−1). Coadsorption of the imine nitrogen atom and PO group with the silver surface, possibly by formation of a weaker interaction with the metal, is also suggested by the enhancement of the bands at 1158 and 1248 cm−1. P1, P2 and P3 show two orientations of their main chain on the silver surface resulting from different interactions of the C CH3, NH and CONH fragments with this surface. Bonding to the Ag surface occurs mainly through the imino atom (1166 cm−1) for P2, while for P1 and P3 it occurs via the methyl group(s) (1194–1208 cm−1). The amide group functionality (CONH) is practically not involved in the adsorption process for P1 and P2, whereas the Cs P bonds do assist in the adsorption. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
66.
亚单分子层三聚氰胺的便携式拉曼检测 总被引:1,自引:0,他引:1
通过改进Lee和Meisel法,制备了两种银胶。以三聚氰胺分子为探针分子,银胶为SERS基底,使用便携式拉曼光谱仪进行拉曼测试。拉曼光谱表明银纳米粒子和三聚氰胺发生的吸附作用明显,三聚氰胺的四个较强振动峰有4~9cm-1的频移和强度比变化较大。由于SERS基底的表面增强作用,三聚氰胺的便携式拉曼光谱仪最小检测量达到了6×10-12g,实现了三聚氰胺的亚单分子层检测水平。该检测方法快捷、简便,如果结合奶粉或食品中三聚氰胺的固相萃取技术,将可以应用于三聚氰胺的现场、快速、半定量检测。 相似文献
67.
本文综述了土壤多孔介质中胶体迁移的释放与沉积机制、影响胶体迁移的多种因素以及土壤中胶体与各种污染物的协同迁移作用,总结了模拟胶体迁移的数学模型以及计算机软件的应用。研究表明,胶体在土壤中的迁移主要受应变、附着、薄膜应变等迁移机制的影响,多孔介质的性质、流体的性质以及胶体自身的性质也会影响胶体的迁移。此外,胶体能有效吸附地下水多孔介质中的有机或无机污染物,并对其在地下环境中的迁移产生显著影响。目前已有许多学者通过数学模型来模拟胶体在土壤中的迁移过程,而计算机技术的进步也将促进更加先进的软件模型应用到胶体迁移的模拟中。 相似文献
68.
H. Bargozin R. A. Hadadhania T. Y. Amiri 《Journal of Dispersion Science and Technology》2016,37(6):806-815
In this work, the influence of chemical heterogeneity on the stability of nanocolloidal systems is surveyed with a new method. Zone of influence as a very important parameter for chemical patch surveying is modeled for sphere and flat surface. Surface chemical heterogeneity with specified properties, size, and position are created by spherical coordinate integration method. Rippled sphere model is used to create roughness and the flat surface is created by changing two sphere radius ratio. Using the spherical coordinate system for modeling of surface roughness and chemical heterogeneity is very accurate and fast. Results show that the patches could destabilize the colloidal system at very small sizes. Surface roughness reduces the effect of chemical patches for destabilizing the colloidal system, and with increasing the size of roughness the total DLVO energy interaction increases. 相似文献
69.
Vera Dugandžić Izabella Jolan Hidi Karina Weber Dana Cialla-May Jürgen Popp 《Analytica chimica acta》2016
Herein we report a novel strategy for the in situ synthesis of the silver colloids for LoC-SERS applications. Silver nanoparticles are obtained in a segmented flow based glass microfluidic chip by the reduction of silver ions with hydrazine in ammonium hydroxide solution. Citrate ions are used as protecting agents. The synthesized nanoparticles are characterized by UV-VIS spectroscopy, SEM and TEM imaging. The SERS performance of the in situ synthesized nanoparticles is tested by using adenine as a test analyte right after the colloid synthesis. Reproducibility is tested by repeating the measurements three times at independent days applying the same measurement conditions. In comparison with nanoparticles synthesized in a conventional strategy i.e. in a large batch, chip synthesized nanoparticles show a better day-to-day and long-term reproducibility, lower detection limits and broader working ranges. The great advantage offered by the in situ synthesized colloids combined with the already proven potential of LoC-SERS for bioanalytics, raises the possibility of the employment of LoC-SERS as a fast and sensitive analytic tool in a plethora of applications. 相似文献
70.
本文用自旋捕捆—ESR方法探讨了苯甲醇在超细微粒二氧化钛胶体表面的光诱导电子转移和光化学行为。结果明确地显示出,在不同pH条件下,笨甲醇在二氧化钛胶体表面的光化学行为有显著差别。在很低pH条件下,体系中检出明显的单重态氧加合物的信号,在pH=3.0左右,则以超氧负离子基为主;pH在4—6范围内时,产生较大量的苄氧基,且认pH=6时为最多;在pH为7左右时,除苄氧基外,同时还有一定量的羟甲基(·CH2OH)和苯基自由基产生。本文对于不同pH条件下的光诱导电子转移和光化学反应机理进行了讨论。 相似文献