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Joe W. Tavacoli Job H. J. Thijssen Andrew B. Schofield Paul S. Clegg 《Advanced functional materials》2011,21(11):2020-2027
Bicontinuous, interfacially jammed emulsion gels (bijels) are a class of soft solid materials in which interpenetrating domains of two immiscible fluids are stabilized by an interfacial colloidal monolayer. Such structures form through the arrest of the spinodal decomposition of an initially single‐phase liquid mixture containing a colloidal suspension. With the use of hexalmethyldisilazane, the wetting character of silica colloids, ranging in size and dye content, can be modified for fabricating a novel bijel system comprising the binary liquid ethanediol–nitromethane. Unlike the preceding water‐lutidine based system, this bijel is stable at room temperature and its fabrication and resultant manipulation are comparatively straightforward. The new system has facilitated three advancements: firstly, we use sub 100 nm silica particles to stabilize the first bijel made from low molecular weight liquids that has domains smaller than ten micrometers. Secondly, our new and robust bijel permits qualitative rheological work which reveals the bijel to be significantly elastic and self healing whilst its domains are able to break, reform and locally rearrange. Thirdly, we encapsulate the ethanediol–nitromethane bijel in Pickering drops to form novel particle‐stabilized bicontinuous multiple emulsions that we christen bijel capsules. These emulsions are stimuli responsive – they liberate their contained materials in response to changes in temperature and solvency, and hence they show potential for controlled release applications. 相似文献
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Marjo Kettunen Riitta J. Silvennoinen Nikolay Houbenov Antti Nykänen Janne Ruokolainen Jani Sainio Viljami Pore Marianna Kemell Mikael Ankerfors Tom Lindström Mikko Ritala Robin H. A. Ras Olli Ikkala 《Advanced functional materials》2011,21(3):510-517
Chemical vapor deposition of a thin titanium dioxide (TiO2) film on lightweight native nanocellulose aerogels offers a novel type of functional material that shows photoswitching between water‐superabsorbent and water‐repellent states. Cellulose nanofibrils (diameters in the range of 5–20 nm) with native crystalline internal structures are topical due to their attractive mechanical properties, and they have become relevant for applications due to the recent progress in the methods of their preparation. Highly porous, nanocellulose aerogels are here first formed by freeze‐drying from the corresponding aqueous gels. Well‐defined, nearly conformal TiO2 coatings with thicknesses of about 7 nm are prepared by chemical vapor deposition on the aerogel skeleton. Weighing shows that such TiO2‐coated aerogel specimens essentially do not absorb water upon immersion, which is also evidenced by a high contact angle for water of 140° on the surface. Upon UV illumination, they absorb water 16 times their own weight and show a vanishing contact angle on the surface, allowing them to be denoted as superabsorbents. Recovery of the original absorption and wetting properties occurs upon storage in the dark. That the cellulose nanofibrils spontaneously aggregate into porous sheets of different length scales during freeze‐drying is relevant: in the water‐repellent state they may stabilize air pockets, as evidenced by a high contact angle, in the superabsorbent state they facilitate rapid water‐spreading into the aerogel cavities by capillary effects. The TiO2‐coated nanocellulose aerogels also show photo‐oxidative decomposition, i.e., photocatalytic activity, which, in combination with the porous structure, is interesting for applications such as water purification. It is expected that the present dynamic, externally controlled, organic/inorganic aerogels will open technically relevant approaches for various applications. 相似文献
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Microscale, quasi‐2D Au–polymer brush composite objects are fabricated by a versatile, controllable process based on microcontact printing followed by brush growth and etching of the substrate. These objects fold into 3D microstructures in response to a stimulus: crosslinked poly(glycidyl methacrylate) (PGMA) brushes fold on immersion in MeOH, and poly(methacryloxyethyl trimethylammonium chloride) (PMETAC) brushes fold on addition of salt. Microcages and microcontainers are fabricated. A multistep microcontact printing process is also used to create sheets of Au–PGMA bilayer lines linked by a PGMA film, which fold into cylindrical tubes. The bending of these objects can be predicted, and hence predefined during the synthesis process by controlling the parameters of the gold layer, and of the polymer brush. 相似文献
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Claudia R. Gordijo Khajag Koulajian Adam J. Shuhendler Leonardo D. Bonifacio Hui Yu Huang Simon Chiang Geoffrey A. Ozin Adria Giacca Xiao Yu Wu 《Advanced functional materials》2011,21(1):73-82
Recently, a new multifunctional, bio‐inorganic nanocomposite membrane with the ability to self‐regulate the release of insulin in response to blood glucose (BG) levels was reported. Herein, the application of this material as part of a small, implantable, closed‐loop insulin delivery device designed to continuously monitor BG concentrations and regulate insulin release is proposed. The insulin delivery device consists of a nanocomposite glucose‐responsive plug covalently bound to an insulin reservoir made of surface‐modified silicone. The plug is prepared with crosslinked bovine serum albumin (BSA) and enzymes (glucose oxidase (GOx) and catalase (CAT)), pH‐responsive hydrogel nanoparticles, and multifunctional MnO2 nanoparticles. The plug functions both as a glucose sensor and controlled delivery unit to release higher rates of insulin from the reservoir in response to hyperglycemic BG levels and basal insulin rates at normal BG concentration. The surfaces of the device are modified by silanization followed by PEGylation to ensure its safety and biocompatibility and the stability of encased insulin. Our results show that insulin release can be modulated in vitro in response to glucose concentrations. In vivo experiments show that the glycemia of diabetic rats can be controlled with implantation of the prototype device. The glucose‐responsiveness of the device is also demonstrated by rapid drop in BG level after challenging diabetic rats with bolus injection of glucose solution. In addition, it is demonstrated that surface PEGylation of the device is necessary for reducing the immune response of the host to the implanted foreign object and maintaining insulin stability and bioactivity. With this molecular architecture and the bio‐inorganic nanocomposite plug, the device has the ability to maintain normal BG levels in diabetic rats. 相似文献
119.
Jatinder S. Randhawa Kate E. Laflin Natasha Seelam David H. Gracias 《Advanced functional materials》2011,21(13):2395-2410
The development of microchemomechanical systems (MCMS) as an analogy to microelectromechanical systems (MEMS) is reviewed, with the distinction that the mechanical actuation of microscale structures is effected by chemical cues as opposed to electricity. The intellectual motivation to pursue MCMS, or the creation of integrated chemical‐stimuli‐responsive devices, is that such structures are widely observed in nature. From a practical standpoint, since chemicals can readily diffuse and produce changes over large distances, this approach is especially attractive in enabling wireless and autonomous devices at small size scales. 相似文献
120.
Inspired by the geometric structure of ecribellate spider capture silk and its spinning characteristics, we propose a one‐step electrohydrodynamic method to fabricate bead‐on‐string heterostructured fibers (BSHFs). By combining electrospinning and electrospraying strategies using a sprayable outer fluid with low viscosity and a spinnable inner fluid with high viscosity in a coaxial jetting process, hydrophilic poly(ethylene glycol) beads are successfully imprinted on a hydrophobic polystyrene string. It is demonstrated that the BSHFs are capable of intelligently responding to environmental change. With a change in relative humidity, the fibers show a segmented swelling and shrinking behavior in the “bead” parts whereas the “string” parts remain the same. The elastic BSHFs with alternating hydrophilic and hydrophobic surface characteristics represent a type of mesoscale analogues that block copolymers and may bring about new properties and applications. Moreover, the combined electrohydrodynamic approach developed herein should open new routes to multifunctional one‐dimensional heterostructured materials. 相似文献