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81.
Investigations on metal-cutting machining processes that were conducted since the second half of the twentieth century have
considerably contributed to disclosing the principles underlying the cutting process. Although numerous studies have been
carried out on this subject, a generally valid model of the cutting process and the interactions in the separating processes
does not exist yet. Such a model could guarantee the disclosure of the principles of thermodynamic interactions between the
cutting process and the involved machine structure. This contribution is twofold and presents an experimental setup used to
determine cutting forces and temperatures in orthogonal cutting processes. The results are then used as a reference for simulations
made with the Discrete Element Method (DEM). The DEM is due to its meshless nature well suited to capture large deformations
and rupture of material which is included very naturally. It is examined to which extent the measured results can be captured
with the DEM model. 相似文献
82.
The Autosar standard represents an emerging approach to unifying virtually all aspects of the development workflow of automotive embedded software. The standard features an XML schema used as a basis for interchanging documents containing Autosar model content. Although the schema is primarily for document exchange, it could also be the basis for creating a metamodel. However, a tool metamodel should probably be designed differently. 相似文献
83.
84.
Hans-Juergen Odenthal Uwe Thiedemann Udo Falkenreck Jochen Schlueter 《Metallurgical and Materials Transactions B》2010,41(2):396-413
The oscillation of argon oxygen decarburization (AOD) converters is flow related and depends on the process parameters (e.g., vessel geometry, melt fill height, process gas type and blowing rate, vessel tilting angle, as well as geometry, number,
and arrangement of the side-wall nozzles). For a 120-ton AOD converter with seven submerged side-wall nozzles, plant tests,
physical simulations on a 1:4 scale water model, and computational fluid dynamics simulations have been done. The investigations
show that the penetration depth of an inert gas jet into the melt does not exceed approximately 0.4 m. The plumes are located
close to the nozzle-side converter wall and induce a large-scale primary vortex as well as intensive surface movements; both
are responsible for the oscillation. Several process mechanisms were investigated. The oscillation is highest in the last
stage of the dynamic blow and is still high during the reduction stage. As the amount of inert gas increases, the vibration
level also increases. Inert gas has a greater influence on the oscillation than oxygen. Tilting the converter around 8 deg
clearly leads to more intensive oscillations. Increasing the blowing rate increases the forces and torques acting on the vessel,
whereas the oscillation frequency remains nearly constant. A varying fill level does not influence the vibration level the
same way as the blowing rate. The operational test shows, for example, that the maximum torque does not depend on the heat
size when the latter varies between –8 pct and +21 pct of the nominal heat size. The water model test shows decreasing forces
and torques with a rising fill level. 相似文献
85.
Angela Gerlach Enrico Preuss Paul Uwe Thamsen Flemming Lykholt-Ustrup 《Journal of Mechanical Science and Technology》2017,31(4):1711-1719
We did a numerical study of the internal flow field of a vortex pump. Five operating points were considered and validated through a measured characteristic curve. The internal flow pattern of a vortex pump was analyzed and compared to the Hamel-Oseen vortex model. The calculated flow field was assessed with respect to the circumferential velocity, the vorticity and the axial velocity. Whereas the trajectories of the circumferential velocity were largely in line with the Hamel-Oseen vortex model, the opposite was true for vorticity. Only the vorticity at strong part load was in line with the predictions of the Hamel-Oseen vortex model. We therefore compared the circumferential velocity and vorticity for strong part load operation to the analytical predictions of the Hamel-Oseen vortex model. The simulated values were below the analytical values. The study therefore suggests that a vortex similar to the Hamel-Oseen vortex is only present at the strong part load operation. 相似文献
86.
87.
Uwe Weigmann Knut Deimer Christian Leininger Ludwig Turba Steffen Jurran 《e & i Elektrotechnik und Informationstechnik》2002,119(11):a19-a19
Firmen&ProdukteDehn Austria
überspannungs-schutz in der Telekommunikation 相似文献88.
Lütke-Eversloh T Fischer A Remminghorst U Kawada J Marchessault RH Bögershausen A Kalwei M Eckert H Reichelt R Liu SJ Steinbüchel A 《Nature materials》2002,1(4):236-240
The development of non-petrochemical sources for the plastics industry continues to progress as large multinationals focus on renewable resources to replace fossil carbon. Many bacteria are known to accumulate polyoxoesters as water-insoluble granules in the cytoplasm. The thermoplastic and/or elastomeric behaviour of these biodegradable polymers holds promise for the development of various technological applications. Here, we report the synthesis and characterization of microbial polythioesters (PTEs), a novel class of biopolymers of general technological relevance. Biosynthesis of PTE homopolymers was achieved using a recombinant strain of Escherichia coli that expressed a non-natural pathway consisting of a butyrate kinase, a phosphotransbutyrylase, and a PHA synthase. Different homopolymers were produced, consisting of either 3-mercaptopropionate, 3-mercaptobutyrate, or 3-mercaptovalerate repeating units, if the respective mercaptoalkanoic acids were provided as precursor substrates to the fermentative process. The PTEs contributed up to 30% (w/w) of the cellular dry weight and were identified as hydrophobic inclusions in the cytoplasm. The chemical and stereochemical homogeneity of the purified PTEs were identified by different methods, and the estimated physical properties were compared to the oxypolyester equivalents, revealing low crystalline order and, for the poly(3-mercaptopropionate) improved thermal stability. The ability to produce PTEs through a biosynthetic route opens up new avenues in the field of biomaterials. 相似文献
89.
4-Nitro-7-piperazino-2,1,3-benzoxadiazole (NBDPZ) is presented as a new reagent for the determination of mono- and diisocyanates in air samples. NBDPZ readily reacts with the airborne analytes, thus yielding the corresponding urea derivatives, which are subsequently separated by means of reversed-phase liquid chromatography. On a phenyl-modified stationary phase, excellent baseline separation for numerous mono- and diisocyanate derivatives is obtained. Both diode array and fluorescence detection are performed with limits of detection of 11-35 and 5-9 nmol/L for the individual derivatives, respectively. In contrast to established derivatizing agents for the analysis of isocyanates, NBDPZ provides for increased selectivity due to the favorable detection wavelengths in the visible range (UV/visible, absorption maximums approximately 480 nm; fluorescence, excitation maximums approximately 470 nm, emission maximums approximately 535 nm). In addition, the high molar absorptivities of the reagent and the derivatives provide excellent sensitivity that is superior to most literature-known methods. Finally, air sampling methods comprising both the use of impingers and test tubes are developed and successfully applied to the determination of isocyanates in gaseous samples. Excellent recovery reaching values of >90% is observed for each of the two techniques investigated. 相似文献
90.
The automatic generation of adjoints of mathematical models that are implemented as computer programs is receiving increased attention in the scientific and engineering communities. Reverse-mode automatic differentiation is of particular interest for large-scale optimization problems. It allows the computation of gradients at a small constant multiple of the cost for evaluating the objective function itself, independent of the number of input parameters. Source-to-source transformation tools apply simple differentiation rules to generate adjoint codes based on the adjoint version of every statement. In order to guarantee correctness, certain values that are computed and overwritten in the original program must be made available in the adjoint program. For their determination we introduce a static data-flow analysis called “to be recorded” analysis. Possible overestimation of this set must be kept minimal to get efficient adjoint codes. This efficiency is essential for the applicability of source-to-source transformation tools to real-world applications. 相似文献