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141.
Interfacial layers have been widely applied to study the formation and stability of emulsion-based systems. However, the application of isolated interfaces to address digestibility of emulsions is often limited because of the complexity of experimental methods and results. This review summarizes the latest developments in analytical methods and literature data on effects of digestion on interfacial layers. Particular emphasis is given to understand the changes on interfacial magnitudes during oral, gastric, and duodenal digestion, either applied separately or sequentially. Limitations of interfacial aspects and key factors that influence emulsion microstructure in bulk and lipid digestion are identified. Understanding the behavior of interfacial layers upon gastrointestinal digestion promotes an accurate tracking of the physiological fate of emulsions. 相似文献
142.
Ohsuna T Slater B Gao F Yu J Sakamoto Y Zhu G Terasaki O Vaughan DE Qiu S Catlow CR 《Chemistry (Weinheim an der Bergstrasse, Germany)》2004,10(20):5031-5040
High-resolution electron microscopy (HREM) has been used to image the surface structure of nano- and micrometer-sized synthetic crystals of zeolite-Linde-L (LTL). Columnar holes and rotational, nano-sized, wheel-like defects were observed within the crystals, where the hole has a minimum size equal to that of the rotational defect. Predictions of surface structure from atomistic computer simulation concur with the observations from HREM and provide insight into the crystal growth mechanism of perfect and defective LTL. Analysis of the energetics of the formation of rotational defect structures reveals that the driving force for defect creation is thermodynamic and furthermore, the rotational defects could be created in high concentrations. Formation of a columnar hole is found to be slightly energetically unfavourable and therefore we speculate that the incidence of both rotational and nano-sized vacancy defects is strongly dependent on kinetic factors and reaction conditions. The morphology of nano- and microcrystalline LTL is contradistinct and we use insights from simulation to propose an explanation of the disparity in crystal shape. 相似文献
143.
岩,心是油气储层的基本单元,其内部结构和渗流性质反映了油藏的基本特征.岩。心的精细描述是油藏描述、储层动态监测及设计强化采油方案的重要基础.本文利用核磁共振(NMR)自旋密度做成像,快速无损地观测到两类基本储油岩石——砂岩和灰岩的内部结构,提供了岩石渗透性、孔隙性及灰岩沉积环境等重要信息.1实验方法以自旋回波单片NMR成像脉冲序列为基础,设。P平面内样品的目施密度为P(。,v).演化期t。,在。方向梯度场G。作用下,各处横向磁化矢量获得的相移为式中,7为共振核(在成像中一般为质子)的旋磁比,g为坐标位置·… 相似文献
144.
Effect of bicarbonate ions on the copper passivity and its local breakdown is studied by cyclic voltammetry, Auger spectroscopy, x-ray photoelectron spectroscopy, and scanning electron microscopy. Comparing data for solutions with various sodium bicarbonate concentrations shows copper to undergo pitting in 0.02 M NaHCO3, whereas it remains stably passive in 0.10 M NaHCO3. Independent studies suggest that carbonates play a protective role in stabilization of the oxide-hydroxide passive film on copper. 相似文献
145.
Klaus van Benthem Stephan Krämer Wilfried Sigle Manfred Rühle 《Mikrochimica acta》2002,138(3-4):181-193
An understanding of the correlation between microstructures and properties of materials require the characterization of the
material on many different length scales. Often the properties depend primarily on the atomistics of defects, such as dislocations
and interfaces. The different techniques of transmission electron microscopy allow the characterization of the structure and
of the chemical composition of materials with high spatial resolution to the atomic level: high resolution transmission electron
microscopy allows the determination of the position of the columns of atoms (ions) with high accuracy. The accuracy which
can be achieved in these measurements depends not only on the instrumentation but also on the quality of the transmitted specimen
and on the scattering power of the atoms (ions) present in the analyzed column.
The chemical composition can be revealed from investigations by analytical microscopy which includes energy dispersive X-ray
spectroscopy, mainly quantitatively applied for heavy elements, and electron energy-loss spectroscopy. Furthermore, the energy-loss
near-edge structure of EELS data results in information on the local band structure of unoccupied states of the excited atoms
and, therefore, on bonding. A quantitative evaluation of convergent beam electron diffraction results in information on the
electron charge density distribution of the bulk (defect-free) material.
The different techniques are described and applied to different problems in materials science. It will be shown that nearly
atomic resolution can be achieved in high resolution electron microscopy and in analytical electron microscopy. Recent developments
in electron microscopy instrumentation will result in atomic resolution in the foreseeable future. 相似文献
146.
147.
利用AFM和SNOM对淋巴细胞膜表面超微结构及其光学性质的初步研究 总被引:5,自引:0,他引:5
利用原子力显微镜(Atomic Force Microscopy,AFM)对淋巴细胞表面形貌进行了形态学的初步研究,观察到了其膜表面其他显微技术所不能发现的超微结构.同时也运用扫描近场光学显微镜(Scanning Near field Optical Microscopy,SNOM)对淋巴细胞进行成像,观察了其对光的透射、吸收等光学性质,并对两种成像方法进行了比较.研究发现:淋巴细胞膜表面凹凸不平,分布着大量直径几十到几百纳米不等的小颗粒;淋巴细胞中央部位有自发荧光现象.结果表明,AFM和SNOM可作为进一步探讨淋巴细胞的结构与功能关系的有力工具. 相似文献
148.
Three novel perylene polyimides (PPIs) containing p‐n diblock units were designed and synthesized for use in dye‐sensitized mesoporous TiO2 solar cells. They all dissolve in m‐cresol and N‐methyl‐2‐pyrrolidone (NMP). Their visible light absorption, electrochemical and photoelectrochemical properties were systematically studied. The polyimides have band gap energies of 2.16, 2.19 and 2.25 eV deduced from ultraviolet–visible absorption spectra, and electron affinity (Ea) and ionization potential (IP) of ?3.93 and 6.10 eV for PPI1, ?3.94 and 6.13 eV for PPI2, ?3.93 and 6.59 eV for PPI3, respectively, deduced from cyclic voltammogram. Experimental data show that introduction of 4,4′‐bisaminetriphenylamine cannot only greatly enhance optic‐electro conversion efficiency, but also enhance the dissolubility which in favorable for making the devices. The relationship of structure and properties of PPI is discussed and the mechanism of photocurrent generation is explained. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
149.
Transmission electron microscopy of freeze fractured and replicated samples (TEM) and polarizing light microscopy (PLM) are
used to investigate the defect structures of the thermotropic and lyotropic mesophases of the non-steroidal antiinflammatory
drug fenoprofen sodium and of the thermotropic mesophase of the nonionic surfactant sucrose oleate (O1570). All mesophases
have a layered, smectic structure. The thermotropic liquid crystal of feno-profen sodium is an interdigitated smectic A phase
(smectic Ad) having the highest viscosity of the investigated samples. The thermotropic mesophase of the sugar ester is also
of the type smectic A, likely to be of subtype smectic A2 (bilayered smectic structure). The lyotropic mesophase is of lamellar
liquid crystalline nature and has a much lower viscosity than the thermotropic mesophases. In the PLM the lyotropic fenoprofen
mesophase has a strong tendency to form a pseudoisotropic texture, indicating a strong tendency to form undisturbed layered
structures. Other textures exhibited in the PLM are fan-shaped texture and maltese-cross texture. Confocal domains, cylinders,
pits and peaks as well as screw dislocations are found in great number in the TEM. However, no greater regions of undisturbed
lamellar arrangement in the lyotropic mesophase could be detected. The only texture of the thermotropic fenoprofen mesophase
visible in the PLM is the fan-shaped texture, indicating confocal domains as predominant structural elements. However, no
confocal domains (tori or Dupin cyclides) are found in the TEM. In the PLM the sugar–ester mesophase exhibited a fan-shaped
texture, maltese crosses and oily streaks as dominant textures. In the TEM only a few +π and −π disclinations and imperfect
confocal domains could be detected. The discrepancies in the appearance of defect structures and textures between the mesophases
as well as the discrepancies in the findings in the PLM and in the TEM investigations are caused by the different sample preparation
and the different viscosities of the mesophases.
Received: 28 May 1997 Accepted: 2 September 1997 相似文献
150.
Nano-mechanical mapping by atomic force microscopy has been developed as an useful application to measure mechanical properties of soft materials at nanometer scale. To date, the Hertzian theory was used for analyzing force-distance curves as the simplest model among several contact mechanics between elastic bodies. However, the preexisting methods based on this theory do not consider the adhesive interaction in principle, which cannot be neglected in the ambient condition. A new analytical method was introduced to estimate the elasticity and the adhesive energy simultaneously by means of the JKR theory, describing adhesive contact between elastic materials. Poly(dimethylsiloxane) (PDMS) and isobutylene-co-isoprene rubber (IIR) were analyzed to verify the applicable limit of the JKR analysis. For elastic samples such as PDMS, the force-deformation plots obtained experimentally were consistent with JKR theoretical curves. Meanwhile, for viscoelastic samples, especially for IIR, the experimental plots revealed large deviations from JKR curves depending on scanning velocity and maximum loading force. Some nano-rheological arguments were employed based on the difference between these specimens. 相似文献