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Michael Gerharz Christian de Waal Peter Martini Paul James 《Telecommunication Systems》2005,28(3-4):317-331
In this article, we introduce a simple distributed algorithm that assigns appropriate individual transmission powers to devices in a wireless ad hoc network. In contrast to many other proposed algorithms, it does without special hardware. It requires only local neighbourhood information and therefore avoids flooding information throughout the network. Finally, the cooperative nature of the algorithm avoids that devices cause excessive interference by using unnecessarily high transmission powers. By means of simulation, we show that the topologies created by this algorithm without any global knowledge are as effective as topologies resulting from a good choice of a common transmission power (which would require global knowledge) in terms of the achievable throughput.
This work was supported in part by the German Federal Ministry of Education and Research (BMBF) as part of the IPonAir project. 相似文献
13.
Martini Maria G. Istepanian Robert S. H. Mazzotti Matteo Philip Nada 《Mobile Computing, IEEE Transactions on》2010,9(1):5-16
M-health is an emerging area of research and one of the key challenges in future research in this area is medical video streaming over wireless channels. Contrasting requirements of almost lossless compression and low available bandwidth have to be tackled in medical quality video streaming in ultrasound and radiology applications. On one side, compression techniques need to be conservative, in order to avoid removing perceptively important information; on the other side, error resilience and correction should be provided, with the constraint of a limited bandwidth. A quality-driven, network-aware approach for joint source and channel coding based on a controller structure specifically designed for enhanced video streaming in a robotic teleultrasonography system is presented. The designed application based on robotic teleultrasonography is described and the proposed method is simulated in a wireless environment in two different scenarios; the video quality improvement achievable through the proposed scheme in such an application is remarkable, resulting in a peak signal-to-noise ratio (PSNR) improvement of more than 4 dB in both scenarios. 相似文献
14.
Wireless Networks - Single carrier-frequency division multiple access (SC-FDMA) is a multiple access technique in broadband wireless networks which has been adapted by 3GPP for uplink transmission... 相似文献
15.
Mina Shiran Chaharsoughi Dan Zhao Xavier Crispin Simone Fabiano Magnus P. Jonsson 《Advanced functional materials》2019,29(28)
Sensors for monitoring temperature, heat flux, and thermal radiation are essential for applications such as electronic skin. While pyroelectric and thermoelectric effects are suitable candidates as functional elements in such devices, both concepts show individual drawbacks in terms of zero equilibrium signals for pyroelectric materials and small or slow response of thermoelectric materials. Here, these drawbacks are overcome by introducing the concept of thermodiffusion‐assisted pyroelectrics, which combines and enhances the performance of pyroelectric and ionic thermoelectric materials. The presented integrated concept provides both rapid initial response upon heating and stable synergistically enhanced signals upon prolonged exposure to heat stimuli. Likewise, incorporation of plasmonic metasurfaces enables the concept to provide both rapid and stable signals for radiation‐induced heating. The performance of the concept and its working mechanism can be explained by ion–electron interactions at the interface between the pyroelectric and ionic thermoelectric materials. 相似文献
16.
Nam-In Kim Miad Yarali Mina Moradnia Muhammad Aqib Che-Hao Liao Feras AlQatari Mingtao Nong Xiaohang Li Jae-Hyun Ryou 《Advanced functional materials》2023,33(10):2212538
Extreme environments are often faced in energy, transportation, aerospace, and defense applications and pose a technical challenge in sensing. Piezoelectric sensor based on single-crystalline AlN transducers is developed to address this challenge. The pressure sensor shows high sensitivities of 0.4–0.5 mV per psi up to 900 °C and output voltages from 73.3 to 143.2 mV for input gas pressure range of 50 to 200 psi at 800 °C. The sensitivity and output voltage also exhibit the dependence on temperature due to two origins. A decrease in elastic modulus (Young's modulus) of the diaphragm slightly enhances the sensitivity and the generation of free carriers degrades the voltage output beyond 800 °C, which also matches with theoretical estimation. The performance characteristics of the sensor are also compared with polycrystalline AlN and single-crystalline GaN thin films to investigate the importance of single crystallinity on the piezoelectric effect and bandgap energy-related free carrier generation in piezoelectric devices for high-temperature operation. The operation of the sensor at 900 °C is amongst the highest for pressure sensors and the inherent properties of AlN including chemical and thermal stability and radiation resistance indicate this approach offers a new solution for sensing in extreme environments. 相似文献
17.
We consider the effect of multiple fibers on wavelength division multiplexing networks without wavelength conversion. We study networks with dynamic wavelength routing and develop accurate analytical models to compare various possible options using single- and multiple-fiber networks. We use results of an analytical model and simulation-based studies to evaluate the blocking performance and cost of multifiber networks. The number of fibers required providing high performance in multifiber networks and their costs are compared. A case is made for using multiple fibers in each link with fewer wavelengths instead of using a single fiber with many wavelengths. In particular, we show that a network with four fibers per link and with four wavelengths on each fiber without any wavelength conversion on any node yields similar same performance as the networks with one fiber per link and 16 wavelengths per fiber on each link and with full wavelength conversion capability on all nodes. In addition, the multifiber network may also offer the cost advantage depending on the relative cost of components. We develop a parametric cost model to show that multiple fibers in each link are an attractive option. Finally, such multifiber networks also has fault tolerance, with respect to a single fiber failure, already built into the system. 相似文献
18.
A hybrid finite-element-modal-expansion procedure for the three-dimensional analysis of passive microwave devices exploiting higher order vector basis functions and an innovative class of curved elements is presented. If modal expansions on ports are not analytically known, they can be numerically obtained via a preliminary two-and-one-half-dimensional finite-element analysis; curved triangular and tetrahedrical elements are defined by a rational Bezier mapping, which provides a remarkable increase in accuracy and flexibility over the conventional polynomial mapping without a significant increase in computational burden. Numerical results are provided to illustrate the efficiency and feasibility of the proposed technique. 相似文献
19.
为确定组成复杂、浮油和高价金属离子含量高、酸性强的塔里木油田酸压返排液处理后能否顺利地配制压裂液,通过对返排液水质分析,提出了一套"过滤-化学沉淀-絮凝沉降-压裂液配制"的处理工艺。大量的浮油影响压裂液的溶胀及交联,滤布过滤可去除浮油与块状杂质组成的黏稠物;高价金属离子阻碍稠化剂分子的伸展,影响压裂液的携砂性能,碳酸钠可直接沉淀金属离子并中和残酸;简单处理之后需絮凝剂进一步絮凝处理,除去返排液中的小颗粒杂质。将处理后的水调节至中性或弱酸性直接配制成压裂液使用,可杜绝环境污染,缓解油田水资源匮乏问题。沉淀剂质量浓度为145g/L、絮凝剂质量浓度为1 000mg/L时,返排液中悬浮颗粒杂质的去除率达98%,水质平均粒径2.36μm。利用处理后的酸压返排液配制的压裂液挑挂性能良好,其流变性能和黏弹性能与清水直接配制的压裂液相差不大,均满足SY/T 6376-2008《压裂液通用技术条件》常规压裂液性能标准,适用于塔里木油田超深井高温高剪切要求。研究表明,酸压返排液重复利用配制压裂液的工艺是可行的。 相似文献
20.
H. Martini 《Zeitschrift für Jagdwissenschaft》1981,27(2):81-90
Zusammenfassung Die Meßergebnisse der Unterkieferlängen von 396 Böcken werden mitgeteilt. Zwischen Unterkieferlänge und Gehörnqualität besteht eine mittelstarke positive Korrelation. Es wird gezeigt, daß die Unterkieferlänge eines Bockes nicht nur abhängig ist von den Umweltbedingungen, also demEisfeld- undEllenbergschen Konditionsfaktor, sondern auch von genetischen Einflüssen. Infolge einer unterschiedlichen relativen Häufigkeit dieser genetisch bedingten unterschiedlichen Unterkieferlängentypen innerhalb des Abschusses gegenüber der bejagten Ausgangspopulation kann das Ergebnis der mittleren Unterkieferlänge des Abschusses erheblich streuen. Das gleiche ist möglich durch eine gegenüber der Ausgangspopulation unterschiedliche relative Häufigkeit der verschiedenen Gehörnqualitäten innerhalb des Abschusses.
Lower jaw length of the roe bucks in an annual bag of the Saar-Pfalz hunting district in the Saarland
Summary The lengths are given of the lower jaws of 396 bucks which were measured. There is a moderately strong positive correlation between lower jaw length and antler quality. It is shown that the lower jaw length of a buck depends not only on environmental conditions, i.e. theEisfeld- undEllenberg condition factor, but also on genetic influences. As the result of a varying relative frequency of these genetically dependent differences within the cull as opposed to the original population which was hunted, the mean lower jaw length in the culled animals can very considerably from the mean of the original population. Similar variation may be found in antler qualities within the cull as against the original population.
Les longueurs de maxillaires inférieurs de brocards figurant au tableau d'une saison de chasse du district sarrois Sarre et Pfalz
Résumé Les résultats de mensurations de longueurs de maxillaires inférieurs de 396 brocards sont communiqués. Entre la longueur du maxillaire et la qualité des bois existe une corrélation positive moyennement significative. On montre que la longueur du maxillaire d'un brocard ne dépend pas seulement de conditions de milieu, c'est-à-dire qu'elle ne constitue pas seulement un indice de condition au sens où l'entendentEisfeld etEllenberg, mais qu'elle est aussi le produit d'influences génétiques.La fréquence relative des génotypes responsables des différentes longueurs de maxillaires relevées parmi ce tableau de chevreuils par rapport à la population d'origine peut expliquer la dispersion importante des valeurs observées. Une considération analogue peut être faite en ce qui concerne la fréquence relative des différentes qualités de trophées observée au sein du même échantillon.相似文献