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排序方式: 共有257条查询结果,搜索用时 31 毫秒
81.
穴状Schiff碱铈配合物的合成与晶体结构 总被引:1,自引:1,他引:1
2,6-二甲酰对甲苯酚和三(2-氨乙基)胺在硝酸铈的模板作用下缩合得到单核穴状Schiff碱配合物[CeNO3·L](NO3)2,铈为九配位。配合物的晶体属三斜晶系,P1↑-空间群,a=1.0833(3)nm,b=1.2654(4)nm,c=1.7626(7)nm,α=83.48°(3),β=89.28(3)°,γ=83.70(3)°,V=2.386(2)nm^3,Z=2。 相似文献
82.
Yang YM Wu KC Huang ZL Chang CH 《Langmuir : the ACS journal of surfaces and colloids》2008,24(5):1695-1700
In this work, a systematic study of effects of three cosolvents (methanol, ethanol, and 1-propanol) on the stability of liposomes formed from soybean phosphatidylcholine (PL-90) by a semispontaneous process was carried out. The experimental results revealed that significant enhancement of PL-90 liposome stability could be achieved by cosolvent addition with suitable amounts. A similar phenomenon was also observed for catansomes formed from ion-pair amphiphiles (IPAs) as demonstrated by decyltrimethylammonium dodecyl sulfate (DeTMA-DS) with a comparatively high concentration of 5 mM. In general, with continued increase in the cosolvent concentration, the stability of liposomes and catansomes first increased, reached a maximum, and then decreased. Furthermore, it was realized that the cosolvent effects on the liposome stability were very similar to those on the catansome stability, which might be also explained by the mechanism proposed on the basis of the viewpoint of a mixed solvent dielectric constant. 相似文献
83.
The induced removal of dipalmitoyl phosphatidylcholine (DPPC) by the exclusion of fibrinogen from mixed DPPC/fibrinogen monolayers at compressed air/liquid interfaces was analyzed. The surface pressure-area hysteresis curves of the monolayers at interfaces were obtained by a Langmuir trough. The hysteresis curves of equilibrium fibrinogen adsorption layers suggest that fibrinogen desorption during the area compression stage became significant at a higher bulk concentration of 1000 ppm. For mixed monolayers of DPPC with fibrinogen, the fibrinogen molecules were expelled from the interface upon compression due to the presence of insoluble DPPC molecules. The squeeze-out of fibrinogen molecules evidently removed a significant number of DPPC molecules from the interface, with the extent depending on fibrinogen surface concentration. During the subsequent area expansion stage, fibrinogen molecules entered the interface and participated in the rise of surface pressure. The induced loss of free DPPC molecules at the interface by the expelled fibrinogen molecules during the area compression stage was then evaluated from the hysteresis curves. 相似文献
84.
85.
Chondrocytes are the only cell type present in mature articular cartilage (2-5% of total tissue). The biological activities of the chondrocyte population are regulated by genetic, biologic and biochemical factors, as well as environmental factors (stress, flow and electric field). Although compressive forces within joint articular cartilage are required for maintenance of the normal composition of articular cartilage, there is a lack of knowledge about the number of pressure-related proteins expressed in articular cartilage. Two-dimensional gel electrophoresis (2-DE) and high-performance liquid chromatography-electrospray/tandem mass spectrometry (HPLC/ESI-MS/MS) were used to identify the levels of pressure-related proteins expressed by chondrocytes grown in the presence or absence of hydrostatic pressure. A total of 266 spots were excised from the gels and analyzed by HPLC/ESI-MS/MS. Functional classification of up-regulated proteins indicated that energy and protein fate were the main biological processes occurring in pressurized chondrocytes. Furthermore, membrane-bound transferrin-like protein p97, a marker of chondrocyte differentiation, was only expressed in chondrocytes under hydrostatic pressure. These data suggest that hydrostatic pressure can induce cell differentiation by increasing the expression level of energy metabolism- and protein fate-related proteins, indicating that hydrostatic pressure may be needed for normal biosynthesis and differentiation of articular chondrocytes. 相似文献
86.
以4-溴-4'-二甲氨基查尔酮和苯乙炔为原料,通过Sonogashira钯催化偶联反应合成了4-苯乙炔基-4'-二甲氨基查尔酮,并通过红外光谱和核磁共振氢谱对其结构进行了表征.进一步研究了4-苯乙炔基-4’-二甲氨基查尔酮在不同极性的溶剂中的紫外可见吸收光谱和荧光光谱,结果表明该化合物具有极性敏感的发光特性. 相似文献
87.
88.
We perform a first-principles simulation to study the electronic and optical properties of wurtzite Zn1 xCuxO.The simulations are based upon the Perdew-Burke-Ernzerhof form of generalised gradient approximation within the density functional theory.Calculations are carried out in different concentrations.With increasing Cu concentration,the band gap of Zn1 xCuxO decreases due to the shift of valence band.The imaginary part of the dielectric function indicates that the optical transition between O 2p states in the highest valence band and Zn 4s states in the lowest conduction band shifts to the low energy range as the Cu concentration increases.Besides,it is shown that the insertion of Cu atom leads to redshift of the optical absorption edge.Meanwhile,the optical constants of pure ZnO and Zn0.75Cu0.25O,such as loss function,refractive index and reflectivity,are discussed. 相似文献
89.
利用静电自组装技术,以生物大分子材料壳聚糖杂化处理具有稳定结构的CdSe/ZnS核/壳量子点,形成复合多层薄膜. 与薄膜的吸收谱线比较,在375nm飞秒激光激发下测量的量子点的光致发光谱存在Stokes位移. 采用Z扫描技术,利用790nm飞秒激光研究了其三阶非线性吸收和折射特性,发现饱和吸收信号来自CdSe/ZnS量子点,而自聚焦的折射信号则部分来自壳聚糖. 测出多层膜的三阶非线性系数分别是β=6.5×10-6cm/W,n2=1.5×10-10cm2/W.
关键词:
CdSe/ZnS量子点
非线性性能
光致发光谱 相似文献
90.
Chih-Jung Wu An-Tsung Kuo Chen-Hsuan Lee Yu-Min Yang Chien-Hsiang Chang 《Colloid and polymer science》2014,292(3):589-597
In this study, a pseudodouble-chained ion pair amphiphile, hexadecyltrimethylammonium-dodecylsulfate (HTMA-DS), was prepared from a mixture of cationic surfactant, hexadecyltrimethylammonium bromide, and anionic surfactant, sodium dodecylsulfate. Positively charged catanionic vesicles were then successfully fabricated from HTMA-DS with the addition of cationic surfactants, dialkyldimethylammonium bromide (DXDAB), including ditetradecyldimethylammonium bromide (DTDAB), dihexadecyldimethylammonium bromide, and dioctadecyldimethylammonium bromide (DODAB), with a mechanical disruption approach. The control of charge characteristic and physical stability of the catanionic vesicles through the variations of DXDAB molar fraction and alkyl chain length was then explored by size, zeta potential, and Fourier transform infrared analyses. It was found that the molecular packing and/or molecular interaction of HTMA-DS with DXDAB rather than the electrostatic repulsion between the charged vesicles dominated the physical stability of the mixed HTMA-DS/DXDAB vesicles. The presence of DTDAB, which possesses short alkyl chains, could adjust the packing of the unmatched chains of HTMA+ and DS? and promote the vesicle formation. However, the weak molecular interaction due to the short chains of DTDA+ could not maintain the vesicle structures in long-term storage. With increasing the alkyl chain length of DXDAB, it was possible to improve the vesicle physical stability through the enhanced molecular interaction in the vesicular bilayer. However, the long alkyl chains of DODAB unmatched with those of HTMA-DS, resulting in the vesicle disintegration in long-term storage. For the formation of stable charged catanionic vesicles of HTMA-DS/DXDAB, a good match in hydrophobic chains and strong molecular interaction were preferred for the vesicle-forming molecules. 相似文献