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161.
A set of monolithic stationary phases representing a broad span of monomers and porogens have been characterized directly in their capillary chromatographic format by computational assessment of their pore structure from transmission electron micrographs obtained after in situ embedment of the monoliths in contrast resin, followed by dissolution of the fused-silica tubing, further encasement of the resin-embedded monolith, and microtomy. This technique has been compared to mercury intrusion, a more conventional technique for macroporosity estimation. Supplementing the embedding resin by lead methacrylate gave a negative staining, and the resulting micrographs showed a good contrast between the polymeric monoliths and the embedding resin that allowed studies on the pore formation and polymer development. The technique was also applied to a commercial monolithic silica column. 相似文献
162.
The discovery of natural RNA sensors that respond to a change in the environment by a conformational switch can be utilized for various biotechnological and nanobiotechnological advances. One class of RNA sensors is the riboswitch: an RNA genetic control element that is capable of sensing small molecules, responding to a deviation in ligand concentration with a structural change. Riboswitches are modularly built from smaller components. Computational methods can potentially be utilized in assembling these building block components and offering improvements in the biochemical design process. We describe a computational procedure to design RNA switches from building blocks with favorable properties. To achieve maximal throughput for genetic control purposes, future designer RNA switches can be assembled based on a computerized preprocessing buildup of the constituent domains, namely the aptamer and the expression platform in the case of a synthetic riboswitch. Conformational switching is enabled by the RNA versatility to possess two highly stable states that are energetically close to each other but topologically distinct, separated by an energy barrier between them. Initially, computer simulations can produce a list of short sequences that switch between two conformers when trigerred by point mutations or temperature. The short sequences should possess an additional desirable property; when these selected small RNA switch segments are attached to various aptamers, the ligand binding mechanism should replace the aforementioned event triggers, which will no longer be effective for crossing the energy barrier. In the assembled RNA sequence, energy minimization folding predictions should then show no difference between the folded structure of the entire sequence relative to the folded structure of each of its constituents. Moreover, energy minimization methods applied on the entire sequence could aid at this preprocessing stage by exhibiting high mutational robustness to capture the stability of the formed hairpin in the expression platform. The above computer-assisted assembly procedure together with application specific considerations may further be tailored for therapeutic gene regulation. Index Terms-Design of RNA switches, energy minimization methods, RNA folding predictions. 相似文献
163.
Karel Klíma Dan Ulmann Martin Barto Michal panko Jaroslava Dukov Radka Vrbov Jan Pinc Jií Kubsek Marek Vlk Tereza Ulmannov Ren Foltn Eitan Brizman Milan Draho Michal Beo Vladimír Macho Jaroslav apek 《International journal of molecular sciences》2021,22(24)
The increasing incidence of trauma in medicine brings with it new demands on the materials used for the surgical treatment of bone fractures. Titanium, its alloys, and steel are used worldwide in the treatment of skeletal injuries. These metallic materials, although inert, are often removed after the injured bone has healed. The second-stage procedure—the removal of the plates and screws—can overwhelm patients and overload healthcare systems. The development of suitable absorbable metallic materials would help us to overcome these issues. In this experimental study, we analyzed an extruded Zn-0.8Mg-0.2Sr (wt.%) alloy on a rabbit model. From this alloy we developed screws which were implanted into the rabbit tibia. After 120, 240, and 360 days, we tested the toxicity at the site of implantation and also within the vital organs: the liver, kidneys, and brain. The results were compared with a control group, implanted with a Ti-based screw and sacrificed after 360 days. The samples were analyzed using X-ray, micro-CT, and a scanning electron microscope. Chemical analysis revealed only small concentrations of zinc, strontium, and magnesium in the liver, kidneys, and brain. Histologically, the alloy was verified to possess very good biocompatibility after 360 days, without any signs of toxicity at the site of implantation. We did not observe raised levels of Sr, Zn, or Mg in any of the vital organs when compared with the Ti group at 360 days. The material was found to slowly degrade in vivo, forming solid corrosion products on its surface. 相似文献
164.
Michal panko Karolína Strnadov Ale Jan Pavlí
ek Pavol Szabo Ondej Kodet Jaroslav Valach Barbora Dvonkov Karel Smetana Jr. Luk Lacina 《International journal of molecular sciences》2021,22(20)
Interleukin-6 (IL-6) is a highly potent cytokine involved in multiple biological processes. It was previously reported to play a distinct role in inflammation, autoimmune and psychiatric disorders, ageing and various types of cancer. Furthermore, it is understood that IL-6 and its signaling pathways are substantial players in orchestrating the cancer microenvironment. Thus, they appear to be potential targets in anti-tumor therapy. The aim of this article is to elucidate the role of IL-6 in the tumor ecosystem and to review the possible therapeutic approaches in head and neck cancer. 相似文献
165.
166.
In this paper a parallel molecular dynamics (MD) model has been developed to investigate the nanoscratch process of single crystal iron. The simulations were performed for two cases with different crystallographic orientations and scratch directions. In Case I the scratch plane is (1 0 0) and the scratch direction is [0 0 1]. In Case II the scratch plane and the scratch direction are (1,−1,2) and [1 1 1], respectively. To validate the MD simulation the nanoscratch testing was conducted using the TriboIndenter. The simulation results reveal that the vertical force and the lateral force tend to increase with the scratch displacement for both cases. Case I has smaller forces than Case II. However, the coefficient of friction for both cases is similar, which is in good agreement with the experimental value. The crystallographic orientation also affects the scratch hardness. The scratch hardness of Case I is smaller than that of Case II. 相似文献
167.
Savvas Petrou Terence M. Sloan Muriel Mewissen Thorsten Forster Michal Piotrowski Bartosz Dobrzelecki Peter Ghazal Arthur Trew Jon Hill 《Concurrency and Computation》2011,23(17):2258-2268
The statistical language R and its Bioconductor package are favoured by many biostatisticians for processing microarray data. The amount of data produced by some analyses has reached the limits of many common bioinformatics computing infrastructures. High Performance Computing systems offer a solution to this issue. The Simple Parallel R Interface (SPRINT) is a package that provides biostatisticians with easy access to High Performance Computing systems and allows the addition of parallelized functions to R. Previous work has established that the SPRINT implementation of an R permutation testing function has close to optimal scaling on up to 512 processors on a supercomputer. Access to supercomputers, however, is not always possible, and so the work presented here compares the performance of the SPRINT implementation on a supercomputer with benchmarks on a range of platforms including cloud resources and a common desktop machine with multiprocessing capabilities. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
168.
In this study, the wettability properties and chemical reactions in ThO2 (~90?% dense)/Me (Me?=?Ce, Al, U) were measured. Sessile drop experiments were carried out at 1000, 1150, and 1250?°C for 60?min and the final apparent contact angles measured were 22°?±?2°, 45°?±?2°, and 135°?±?3°, respectively. Chemical reaction at the interface was detected only in the case of ThO2/Al, where a thick (100–200?μm) C4 structure layer containing α-Al2O3 and Th-rich Al metallic phases were found. In this study, correlation between the thermodynamic properties of the binary Me–Th melts, chemical reaction at the interfaces, and spreading behavior was demonstrated. The Th–Al liquid solution has a negative departure from ideality and the chemical reaction at the ThO2/Al interface was massive. The Th–U liquid solution displays a positive departure from ideality and the chemical reaction at the ThO2/U interface was negligible. Th–Ce liquid solution displays a close to ideal behavior with a small positive departure from ideality, which promoted spreading without significant Th dissolution in the Ce melt and no detectable formation of new oxides at the interface. It is proposed that the mild chemical reaction in the ThO2/Ce system is ideal for pressure-free infiltration processes. The dominance of the liquid solution properties concerning wettability behavior and chemical reaction at the interface was demonstrated using thermodynamic evaluation. 相似文献
169.
Lodewyck J Zawada M Lorini L Gurov M Lemonde P 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2012,59(3):411-415
We report on the observation of a dc Stark frequency shift at the 10-(13) level by comparing two strontium optical lattice clocks. This frequency shift arises from the presence of electric charges trapped on dielectric surfaces placed under vacuum close to the atomic sample. We show that these charges can be eliminated by shining UV light on the dielectric surfaces, and characterize the residual dc Stark frequency shift on the clock transition at the 10-(18) level by applying an external electric field. This study shows that the dc Stark shift can play an important role in the accuracy budget of lattice clocks, and should be duly taken into account. 相似文献
170.
The electronic, optical, and mechanical properties of bilayer and trilayer graphene vary with their structure, including the stacking order and relative twist, providing novel ways to realize useful characteristics not available to single layer graphene. However, developing controlled growth of bilayer and trilayer graphene requires efficient large-scale characterization of multilayer graphene structures. Here, we use dark-field transmission electron microscopy for rapid and accurate determination of key structural parameters (twist angle, stacking order, and interlayer spacing) of few-layer CVD graphene. We image the long-range atomic registry for oriented bilayer and trilayer graphene, find that it conforms exclusively to either Bernal or rhombohedral stacking, and determine their relative abundances. In contrast, our data on twisted multilayers suggest the absence of such long-range atomic registry. The atomic registry and its absence are consistent with the two different strain-induced deformations we observe; by tilting the samples to break mirror symmetry, we find a high density of twinned domains in oriented multilayer graphene, where multiple domains of two different stacking configurations coexist, connected by discrete twin boundaries. In contrast, individual layers in twisted regions continuously stretch and shear independently, forming elaborate Moiré patterns. These results, and the twist angle distribution in our CVD graphene, can be understood in terms of an angle-dependent interlayer potential model. 相似文献