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排序方式: 共有314条查询结果,搜索用时 15 毫秒
11.
Tatjana Davidović Dušan Ramljak Milica Šelmić Dušan Teodorović 《Computers & Operations Research》2011
Bee colony optimization (BCO) is a relatively new meta-heuristic designed to deal with hard combinatorial optimization problems. It is biologically inspired method that explores collective intelligence applied by the honey bees during nectar collecting process. In this paper we apply BCO to the p-center problem in the case of symmetric distance matrix. On the contrary to the constructive variant of the BCO algorithm used in recent literature, we propose variant of BCO based on the improvement concept (BCOi). The BCOi has not been significantly used in the relevant BCO literature so far. In this paper it is proved that BCOi can be a very useful concept for solving difficult combinatorial problems. The numerical experiments performed on well-known benchmark problems show that the BCOi is competitive with other methods and it can generate high-quality solutions within negligible CPU times. 相似文献
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Marko Hölbl Tatjana Welzer Boštjan Brumen 《Journal of Computer and System Sciences》2012,78(1):142-150
Two-party authenticated key agreement protocols using pairings have gained much attention in the cryptographic community. Several protocols of this type where proposed in the past of which many were found to be flawed. This resulted in attacks or the inability to conform to security attributes. In this paper, we propose an efficient identity-based authenticated key agreement protocol employing pairings which employs a variant of a signature scheme and conforms to security attributes. Additionally, existing competitive and the proposed protocol are compared regarding efficiency and security. The criteria for efficiency are defined in this paper, whereas the criteria for security are defined by the fulfilment of security attributes from literature. 相似文献
14.
Henny M. Borsboom Tatjana Claasen-Vujčić Harry J. G. Gaykema Toon Mehlkopf 《Magma (New York, N.Y.)》1997,5(1):33-37
The birdcage resonator is frequently used in conventional MRI because of its excellent attributes. Its use in low-field MRI
is restricted to field strengths higher than, for example, 0.1 T, dependent on the size of the coil. This is because of the
intrinsically low inductance value of the birdcage coils. Furthermore, the sensitivity of the birdcage at low field strengths
is significantly lower when compared to, for example, the solenoid. Both problems can be overcome with the multiturn technique
and a novel wound birdcage coil. The quadrature mode wound birdcage coil presented in this paper can be used at frequencies
as low as 100 kHz. Its sensitivity is also increased when compared to the conventional strip-ring birdcage. Homogeneity effective
volume, and methods to increase the resonator bandwidth to match the signal bandwidth are left intact. The latter is a typical
low-field problem. 相似文献
15.
Stefan Alexander Tennigkeit Raziye Karapinar Till Rudack Max-Aylmer Dreier Philipp Althoff Dennis Eickelbeck Tatjana Surdin Michelle Grömmke Melanie D. Mark Katharina Spoida Mathias Lübben Udo Höweler Prof. Dr. Stefan Herlitze Prof. Dr. Klaus Gerwert 《Chembiochem : a European journal of chemical biology》2019,20(14):1766-1771
The primary goal of optogenetics is the light-controlled noninvasive and specific manipulation of various cellular processes. Herein, we present a hybrid strategy for targeted protein engineering combining computational techniques with electrophysiological and UV/visible spectroscopic experiments. We validated our concept for channelrhodopsin-2 and applied it to modify the less-well-studied vertebrate opsin melanopsin. Melanopsin is a promising optogenetic tool that functions as a selective molecular light switch for G protein-coupled receptor pathways. Thus, we constructed a model of the melanopsin Gq protein complex and predicted an absorption maximum shift of the Y211F variant. This variant displays a narrow blue-shifted action spectrum and twofold faster deactivation kinetics compared to wild-type melanopsin on G protein-coupled inward rectifying K+ (GIRK) channels in HEK293 cells. Furthermore, we verified the in vivo activity and optogenetic potential for the variant in mice. Thus, we propose that our developed concept will be generally applicable to designing optogenetic tools. 相似文献
16.
Tatjana N. Basharina Elena N. Danilovtseva Stanislav N. Zelinskiy Igor V. Klimenkov Yelena V. Likhoshway Vadim V. Annenkov 《SILICON》2012,4(4):239-249
The effect of three Group IV metals (titanium, zirconium and tin) on the growth, morphology and chemical composition of the freshwater diatom Synedra acus subsp. radians (Kützing) Skabichevsky was studied and compared with germanium. The elements in their highest oxidation states were introduced into the culture medium in the form of hydroxides. Germanium was found to be toxic at ??5?mol. % of the total Ge-Si content in the culture medium. In the presence of other elements, a slight decrease in the cell division rate was observed independent of the element within 1?C15% content interval. The analysis of the obtained biomass and silica valves revealed the presence of all the added elements within the cells. However, only germanium was incorporated into the valves in considerable amounts. S. acus cultivation with the addition of 5% Group IV elements resulted in cells having the following aberrations in the structure of the silica valves: changes in valve shape, thickening of valves, alterations of the areolae rows, irregularity or absence of the areolae and a decrease in the mechanical strength of valves. Moreover, the effect of Group IV elements on silica formation was simulated in vitro using a synthetic polymer bearing polyamine and phosphate groups found in silaffines (proteins from diatom frustules). The studied elements were observed to provoke the formation of unstable silica particles in solution. We propose that the observed effects of germanium, titanium, zirconium and tin on diatom growth and structure are due to uncontrollable silica condensation. 相似文献
17.
Bipedal animals experience ground reaction forces (GRFs) that pass close to the centre of mass (CoM) throughout stance, first decelerating the body, then re-accelerating it during the second half of stance. This results in fluctuations in kinetic energy, requiring mechanical work from the muscles. However, here we show analytically that, in extreme cases (with a very large body pitch moment of inertia), continuous alignment of the GRF through the CoM requires greater mechanical work than a maintained vertical force; we show numerically that GRFs passing between CoM and vertical throughout stance are energetically favourable under realistic conditions; and demonstrate that the magnitude, if not the precise form, of actual CoM-torque profiles in running is broadly consistent with simple mechanical work minimization for humans with appropriate pitch moment of inertia. While the potential energetic savings of CoM-torque support strategies are small (a few per cent) over the range of human running, their importance increases dramatically at high speeds and stance angles. Fast, compliant runners or hoppers would benefit considerably from GRFs more vertical than the zero-CoM-torque strategy, especially with bodies of high pitch moment of inertia—suggesting a novel advantage to kangaroos of their peculiar long-head/long-tail structure. 相似文献
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