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991.
Jindrich Kopecek 《Journal of polymer science. Part A, Polymer chemistry》2009,47(22):5929-5946
Hydrogels were the first biomaterials designed for clinical use. Their discovery and applications as soft contact lenses and implants are presented. This early hydrogel research served as a foundation for the expansion of biomedical polymers research into new directions: design of stimuli sensitive hydrogels that abruptly change their properties upon application of an external stimulus (pH, temperature, solvent, electrical field, biorecognition) and hydrogels as carriers for the delivery of drugs, peptides, and proteins. Finally, pathways to self‐assembly of block and graft copolymers into hydrogels of precise 3D structures are introduced. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5929–5946, 2009 相似文献
992.
L. Alexandrova K. Hanumantha Rao K.S.E. Forsberg L. Grigorov R.J. Pugh 《Colloids and surfaces. A, Physicochemical and engineering aspects》2009,348(1-3):228-233
The stability and interactions in thin wetting films between the silica surface and air bubble containing (a) straight chain C10 amine and (b) cationic/anionic surfactant mixture of a straight chain C10 amine with sodium C8, C10 and (straight chain) C12 sulfonates, were studied using the microscopic thin wetting film method developed by Platikanov [D. Platikanov, J. Phys. Chem. 68 (1964) 3619]. Film lifetimes, three-phase contact (TPC) expansion rate, receding contact angles and surface tension were measured. The presence of the mixed cationic/anionic surfactants was found to lessen contact angles and suppresses the thin aqueous film rupture, thus inducing longer film lifetime, as compared to the pure amine system. In the case of mixed surfactants heterocoagulation could arise through the formation of positively charged interfacial complexes. Mixed solution of cationic and anionic surfactants shows synergistic lowering in surface tension. The formation of the interfacial complex at the air/solution interface was confirmed by surface tension data. It was also shown, that the chain length compatibility between the anionic and cationic surfactants system controls the strength of the interfacial complex. The observed phenomena were discussed in terms of the electrostatic heterocoagulation theory, where the interactions can be attractive or repulsive depending on the different surface activity and charge of the respective surfactants at the two interfaces. 相似文献
993.
Yinpo Qiao Xiaopeng Zhao 《Colloids and surfaces. A, Physicochemical and engineering aspects》2009,340(1-3):33-39
Carbonaceous materials with different hierarchical porous structures for electrorheological (ER) dispersed phase have been synthesized by carbonization of as-prepared starch/silica precurser at different temperatures. The N2 adsorption isotherms show that Cmeso-700 and Cmeso-500 particles have the BET surface areas of 1028 and 603 m2 g−1, respectively. They both have the mesoporous pores with size of about 4.6 nm and the microporous pores (1.1 and 1.5 nm, respectively). The BET surface areas and C/O atomic ratio of porous carbon materials can be increased with the carbonization temperatures. The rheological measurements indicate that the Cmeso-700 and Cmeso-500 ERF have the better ER effect resulted from their hierarchical porous structures. The shear stress of Cmeso-700 ERF is 900 Pa at 1000 s−1 under 3 kV mm−1, which is almost 4.5 times larger than that of Cmicro-350 ERF. The mesoporous carbon ERFs also show the better sedimentation stability than microporous carbon ERFs. The different ER effect of carbonaceous particles may derive from their different dielectric polarization property induced by the hierarchical porous structures. 相似文献
994.
The oil industry has been facing the challenges of separation of xylene isomers, o-xylene, m-xylene and p-xylene or removing them from the environment. In our present work, we investigated the adsorption of the three isomers on
two mesoporous materials, FDU-15-350 polymer and FDU-15-900 carbon materials. The isomer adsorption capacities are well correlated
with their physical pore properties. It is found that the micropores are very crucial for the adsorption of these three isomers.
The more micropore volume the adsorbent has, the better the adsorption capacity is. Henry’s constants were also calculated
for the three isomers on the two adsorbents. Both on FDU-15-350 polymer and FDU-15-900, the Henry’s constants for the three
isomers show the same trend o>m>p xylene which is coincidently in accordance with their polarity trend, indicating more polar adsorbate is preferred for adsorption
on the two adsorbents. The isosteric heats of adsorption are correlated with the microporosity and the size of the adsorbate
molecule. More microporosity and smaller molecules give higher heats of adsorption. Extracted information on pore properties
of adsorbents by using the three isomers has very similar results as that resolved from nitrogen adsorption, indicating the
feasibility of using the three isomers as adsorbates to extract pore information.
This work is devoted to commemorating the 60th birthday of Professor Mieczyslaw (Mietek) Jaroniec. 相似文献
995.
Highly ordered SBA-15 nanoporous silica containing ethylene, phenylene bridges or/and amine, thiol, vinyl and phenyl surface
groups were synthesized by using amphiphilic block copolymer as the structure-directing agent. The XRD data shows high degree
of the order of the final structures. Obtained materials have well-developed porous structure—values of specific surface area
are in the range 700–1050 m2/g and the sizes of cylindrical mesopores are in the range 6.5–9.5 nm. It was determined that size of the mesopores strongly
depends even on small amounts of co-monomers co-condensing with TEOS. A new technique to introduce some amount of pendant
amine groups by co-condensation of proper monomers has been proposed. Tetragonal structure was obtained when small amount
of vinyl groups was introduced to the system. A new approach of determining pore size based only on the XRD measurements was
compared with KJS method, confirming full usefulness of the former for calculation of the size of mesopores in SBA-15 materials.
Dedicated to Professor Mietek Jaroniec on the occasion of his 60th birthday. 相似文献
996.
Mariusz Trytek Jan Fiedurek Agnieszka Lipke Stanisław Radzki 《Journal of Sol-Gel Science and Technology》2009,51(3):272-286
Two types of porphyrins (water-soluble and water-insoluble) were encapsulated in transparent monolithic silica gels. Their
properties in solutions and at various steps of the sol–gel process were studied by absorption and emission electron spectroscopy.
A photocatalytic system containing porphyrins immobilized in powdered silica gel for α-pinene biomimetic oxidation to pinocarveol,
pinocarvone and myrtenol is reported. The impact of several parameters (visible light irradiation time, organic solvent, the
presence of an electron acceptor/donor, and substrate concentration) on this biotransformation process was investigated and
optimized. It was established that photochemical excitation of sol–gel immobilized metal-free porphyrins is crucial for catalyzed
oxidation of monoterpenes. 相似文献
997.
利用同步辐射CT (SR-CT)技术, 在氮化硅陶瓷样品烧结过程中对其进行实时投影成像, 并应用滤波反投影算法和数字图像处理技术, 得到了样品在整个烧结过程中内部微结构演化的二维和三维重建图像, 实现了对陶瓷固相烧结过程实时、无损的观测. 通过重建图像清晰观测到了陶瓷样品在烧结三个阶段中颗粒接触、烧结颈形成、晶粒和气孔长大、气孔球化并收缩等烧结现象; 统计了样品在不同烧结时刻的孔隙率, 得到了孔隙率随烧结时间对数的变化曲线, 并根据曲线分析了样品在不同烧结时刻致密化速率的变化, 得到了烧结中期孔隙率和时间对数的线性关系. 实验的结果和现有烧结理论相吻合, 并为进一步完善烧结理论提供了有效的实验数据. 相似文献
998.
Isabel Izquierdo-Barba Edesia Sousa Juan Carlos Doadrio Antonio Luis Doadrio Joaquín Pérez Pariente Africa Martínez Florence Babonneau María Vallet-Regí 《Journal of Sol-Gel Science and Technology》2009,50(3):421-429
Ordered mesoporous materials exhibit potential features to be used as controlled drug delivery systems, including their wide
range of chemical compositions and their outstanding textural and structural properties. Therefore, it is possible to control
the drug release kinetics by tailoring such parameters. In this paper, mesoporous materials such as MCM-48 and SBA-15, which
present different pore sizes (3.7 and 8.8 nm) and structural characteristics (3D-bicontinuous cubic and 2D-hexagonal, respectively)
have been synthesized to evaluate their application as drug delivery system and to determine their influence on release kinetic
of ibuprofen. Moreover, a chemical modification of the SBA-15 mesoporous material with octadecyltrimethoxysilane has also
been performed to study its influence on the release rate of ibuprofen. The structural characteristics (3D cubic and 2D hexagonal
pore system) do not affect the release kinetic profiles of ibuprofen. On the contrary, the pore size affects highly to the
release kinetic profiles from first-order kinetic to zero-order kinetic for MCM-48 and SBA-15, respectively. Moreover, the
importance of surface functionalization was demonstrate through the very fast delivery of ibuprofen from SBA-15 mesoporous
materials functionalized with octadecyl chains. 相似文献
999.
Giulio Scocchi Dr. Paola Posocco Jan‐Willem Handgraaf Dr. Johannes G. E. M. Fraaije Prof. Maurizio Fermeglia Prof. Sabrina Pricl Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(31):7586-7592
We present an innovative, multiscale computational approach to probe the behaviour of polymer–clay nanocomposites (PCNs). Our modeling recipe is based on 1) quantum/force‐field‐based atomistic simulation to derive interaction energies among all system components; 2) mapping of these values onto mesoscopic bead–field (MBF) hybrid‐method parameters; 3) mesoscopic simulations to determine system density distributions and morphologies (i.e., intercalated versus exfoliated); and 4) simulations at finite‐element levels to calculate the relative macroscopic properties. The entire computational procedure has been applied to two well‐known PCN systems, namely Nylon 6/Cloisite 20A and Nylon 6/Cloisite 30B, as test materials, and their mechanical properties were predicted in excellent agreement with the available experimental data. Importantly, our methodology is a truly bottom‐up approach, and no “learning from experiment” was needed in any step of the entire procedure. 相似文献
1000.
David B. Cordes Dr. Marcin Smiglak Dr. C. Corey Hines Nicholas J. Bridges Dr. Meghna Dilip Dr. Geetha Srinivasan Dr. Andreas Metlen Dr. Robin D. Rogers Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(48):13441-13448
New, potentially green, and efficient synthetic routes for the remediation and/or re‐use of perchlorate‐based energetic materials have been developed. Four simple organic imidazolium‐ and phosphonium‐based perchlorate salts/ionic liquids have been synthesized by simple, inexpensive, and nonhazardous methods, using ammonium perchlorate as the perchlorate source. By appropriate choice of the cation, perchlorate can be incorporated into an ionic liquid which serves as its own electrolyte for the electrochemical reduction of the perchlorate anion, allowing for the regeneration of the chloride‐based parent ionic liquid. The electrochemical degradation of the hazardous perchlorate ion and its conversion to harmless chloride during electrolysis was studied using IR and 35Cl NMR spectroscopies. 相似文献