全文获取类型
收费全文 | 173篇 |
免费 | 24篇 |
国内免费 | 26篇 |
专业分类
化学 | 150篇 |
晶体学 | 2篇 |
力学 | 15篇 |
综合类 | 3篇 |
数学 | 19篇 |
物理学 | 34篇 |
出版年
2023年 | 2篇 |
2022年 | 12篇 |
2021年 | 6篇 |
2020年 | 8篇 |
2019年 | 4篇 |
2018年 | 8篇 |
2017年 | 2篇 |
2016年 | 12篇 |
2015年 | 12篇 |
2014年 | 10篇 |
2013年 | 7篇 |
2012年 | 13篇 |
2011年 | 11篇 |
2010年 | 5篇 |
2009年 | 13篇 |
2008年 | 10篇 |
2007年 | 12篇 |
2006年 | 10篇 |
2005年 | 6篇 |
2004年 | 6篇 |
2003年 | 6篇 |
2002年 | 7篇 |
2001年 | 4篇 |
2000年 | 3篇 |
1999年 | 6篇 |
1998年 | 8篇 |
1997年 | 6篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1994年 | 3篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1991年 | 5篇 |
1989年 | 1篇 |
1986年 | 1篇 |
排序方式: 共有223条查询结果,搜索用时 46 毫秒
81.
Xiao Z Shangguan D Cao Z Fang X Tan W 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(6):1769-1775
Nucleic acid aptamers have been shown many unique applications as excellent probes in molecular recognition. However, few examples are reported which show that aptamers can be internalized inside living cells for aptamer functional studies and for targeted intracellular delivery. This is mainly due to the limited number of aptamers available for cell-specific recognition, and the lack of research on their extra- and intracellular functions. One of the major difficulties in aptamers' in vivo application is that most of aptamers, unlike small molecules, cannot be directly taken up by cells without external assistance. In this work, we have studied a newly developed and cell-specific DNA aptamer, sgc8. This aptamer has been selected through a novel cell selection process (cell-SELEX), in which whole intact cells are used as targets while another related cell line is used as a negative control. The cell-SELEX enables generation of multiple aptamers for molecular recognition of the target cells and has significant advantages in discovering cell surface binding molecules for the selected aptamers. We have studied the cellular internalization of one of the selected aptamers. Our results show that sgc8 is internalized efficiently and specifically to the lymphoblastic leukemia cells. The internalized sgc8 aptamers are located inside the endosome. Comparison studies are done with the antibody for the binding protein of sgc8, PTK7 (Human protein tyrosine kinase-7) on cell surface. We also studied the internalization kinetics of both the aptamer and the antibody for the same protein on the living cell surface. We have further evaluated the effects of sgc8 on cell viability, and no cytotoxicity is observed. This study indicates that sgc8 is a promising agent for cell-type specific intracellular delivery. 相似文献
82.
Li Faqiang Shangguan Xuehui Jia Guofeng Wang Qinglei Gong Yan Bai Bin Fan Wei 《Journal of Solid State Electrochemistry》2016,20(12):3491-3498
Journal of Solid State Electrochemistry - The LiNi0.5Mn1.5O4 has been investigated as promising because of its high operating voltage (4.7 V vs. Li+/Li) and decent specific capacity.... 相似文献
83.
Huangtianzhi Zhu Qi Li Zongchun Gao Dr. Hongliang Wang Dr. Bingbing Shi Yitao Wu Liqing Shangguan Prof. Dr. Xin Hong Prof. Dr. Feng Wang Prof. Dr. Feihe Huang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(27):10960-10964
The contradiction between the rising demands of optical chirality sensing and the failure in chiral detection of cryptochiral compounds encourages researchers to find new methods for chirality amplification. Inspired by planar chirality and the host–guest recognition of pillararenes, we establish a new concept for amplifying CD signals of cryptochiral molecules by pillararene host–guest complexation induced chirality amplification. The planar chirality of pillararenes is induced and stabilized in the presence of the chiral guest, which makes the cryptochiral molecule detectable by CD spectroscopy. Several chiral guests are selected in these experiments and the mechanism of chiral amplification is studied with a non-rotatable pillararene derivative and density functional theory calculations. We believe this work affords deeper understanding of chirality and provides a new perspective for chiral sensing. 相似文献
84.
Ethylene/propylene-random-copolymer(PPR)/clay nanocomposites were prepared by two-stage melt blending. Four types of compatibilizers,including an ethylene-octene copolymer grafted maleic anhydride(POE-g-MA) and three maleic-anhydride-grafted polypropylenes(PP-g-MA) with different melt flow indexes(MFI),were used to improve the dispersion of organic clay in matrix.On the other hand,the effects of organic montmorillonite(OMMT) content on the nanocomposite structure in terms of clay dispersion in PPR matrix,thermal behavior and tensile properties were also studied. The X-ray diffraction(XRD) and transmission electron microscopy(TEM) results show that the organic clay layers are mainly intercalated and partially exfoliated in the nanocomposites.Moreover,a PP-g-MA compatibilizer(compatibilizer B) having high MFI can greatly increase the interlayer spacing of the clay as compared with other compatibilizers.With the introduction of compatibilizer D(POE-g-MA),most of the clays are dispersed into the POE phase,and the shape of the dispersed OMMT appears elliptic,which differs from the strip of PP-g-MA.Compared with virgin PPR,the Young’s modulus of the nanocomposite evidently increases when a compatibilizer C(PP-g-MA) with medium MFI is used.For the nanocomposites with compatibilizer B and C,their crystallinities(X_c) increase as compared with that of the virgin PPR. Furthermore,the increase of OMMT loadings presents little effect on the melt temperature(T_m) of the PPR/OMMT nanocomposites,and slight effect on their crystallization temperature(T_c).Only compatibilizer B can lead to a marked increases in crystallinity and T_c of the nanocomposite when the OMMT content is 2 wt%. 相似文献
85.
Abstract A layered titanoniobate, in which the interlayer of the metal oxide based on octahedral framework is pillared with silica, has been prepared from HTiNbO5 by employing alkylamines (CnH2n+1NH2, n = 4, 6, 8, 10) and tetraethylorthosilicate as interlayer exchange guests and a pillar precursor, respectively. The incorporated amine had bilayer arrangements in the interlayer space and their ammonium head groups pointed to the host (TiNbO55 ?) layers. While the basal spacing of the compounds increased with the chain length of alkylamine. the inclination angle also increased. The intercalated structure facilitated the incorporation of tetraethylorthosilicate into the interlayers, and silica-pillared layered titanoniobate was obtained after calcination. The physicochemical properties of the resultant pillared compounds were characterized on the interlayer microstructure, nitrogen adsorption and UV-VIS absorption spectra. 相似文献
86.
相位敏感光学相干层析成像(OCT)系统可以用于高灵敏度的相位探测,在细胞分析、材料检测等方面具有重要应用,但扫频光源的不稳定性会影响扫频OCT系统的相位测量精度.本文提出了一种基于马赫-曾德尔干涉仪(MZI)时域相位信息的波数校正方法.利用MZI时域包裹相位的互相关运算确定各采集波数序列的相对偏移量,鉴于时域包裹相位的非严格周期特征,可确定偏移量的大小不受限制.依据相对偏移量对各序列信号进行时域同步,并基于同步后的MZI时域解包裹相位实施待测干涉信号在位相域的等间隔重采样.基于所提出的波数校正方法,实施了各扫频序列波数偏移量的校正,开展了基于位相信息的光程重复性测量实验.结果表明,即使在不稳定扫频光源的前提下,也能获得高精度的相位测量结果. 相似文献
87.
To investigate the nonlinear vibration behavior of a shrouded blade with friction dynamic contact interface, a friction contact stiffness model is proposed to describe the friction force at different rough interfaces and different normal loads. In the proposed model, the friction contact interface is discretized to a series of friction contact pairs and each of them can experience stick, slip, or separate states. Fractal geometry is used to simulate the topography of contact surfaces. The contact stiffness is calculated using the Hertz contact theory and fractal geometry, which is related to contact interfaces parameters including normal load, roughness, Young??s modulus, and Poisson??s ratio. The trajectory tracking method is used to predict the friction force and it is not necessary to judge the transition condition among stick, slip, and separate states. It is suitable for complicated periodic motion of the contact interfaces. The forced response of a real shrouded blade is predicted using the proposed model and the multi-harmonic balance method. The effect of surface roughness, initial normal load, and contact area on the forced response of a shrouded blade is studied. It is shown that contact stiffness increases with normal load and fractal dimension. The resonant amplitude is sensitive to the initial normal load and contact surface roughness. The response can be influenced by the contact area, which is an important parameter for blade designers. 相似文献
88.
A one-step copper-carbodimide elimination was used to provide the (E)-dehydroisoleucine moiety in the phomopsin side chain stereoselectively. An efficient approach to the phomopsin tripeptide side chain was developed to be used in the total syntheses of phomopsins A and B. 相似文献
89.
Qiang Wu Miao Du Tao Ye Yong-gang Shangguan Jian-ping Zhou Qiang Zheng 《Colloid and polymer science》2009,287(8):911-918
Interactions between anionic polyelectrolyte, poly(acrylic acid) (PAA), and cationic surfactant, alkyltrimethylammonium bromide
(C
n
TAB), were investigated by rheological measurements in semidilute PAA solution. The dependences of the rheological behavior
on the chain length of the surfactant, PAA neutralization degree, and temperature were discussed. The results revealed that
both dodecyl and cetyltrimethylammonium bromides (C12TAB and C16TAB) could increase the viscosity of PAA solution when the surfactant amounts surpassed a critical surfactant concentration
(C
c), and C
c of C16TAB was lower than that of C12TAB at same PAA neutralization degree. The increase of viscosity is attributed to the surfactant micelles bridging of the
polymer chains and confine the mobility PAA chain. On the other hand, it is found that the hydrogen bonding also played an
important role in the PAA–C
n
TAB system, especially in lower neutralization degree PAA solution, which results in the viscosity increase rapidly with the
added surfactant into lower neutralization degree PAA solution. 相似文献
90.
Utilizing a three-particle W state, we come up with a protocol for the teleportation of an unknown two-particle entangled state. It is shown that the teleportation can be deterministically and exactly realized. Moreover, two-particle entanglement teleportation is generalized to a system consisting of many particles via a three-particle W state and a multi-particle W state, respectively. All unitary transformations performed by the receiver are given in a concise formula. 相似文献