全文获取类型
收费全文 | 85485篇 |
免费 | 1008篇 |
国内免费 | 408篇 |
专业分类
电工技术 | 811篇 |
综合类 | 2318篇 |
化学工业 | 12135篇 |
金属工艺 | 4808篇 |
机械仪表 | 3048篇 |
建筑科学 | 2312篇 |
矿业工程 | 565篇 |
能源动力 | 1166篇 |
轻工业 | 3715篇 |
水利工程 | 1268篇 |
石油天然气 | 343篇 |
无线电 | 9323篇 |
一般工业技术 | 16459篇 |
冶金工业 | 2796篇 |
原子能技术 | 264篇 |
自动化技术 | 25570篇 |
出版年
2019年 | 28篇 |
2018年 | 14465篇 |
2017年 | 13386篇 |
2016年 | 9996篇 |
2015年 | 648篇 |
2014年 | 292篇 |
2013年 | 256篇 |
2012年 | 3214篇 |
2011年 | 9488篇 |
2010年 | 8324篇 |
2009年 | 5612篇 |
2008年 | 6844篇 |
2007年 | 7837篇 |
2006年 | 198篇 |
2005年 | 1277篇 |
2004年 | 1201篇 |
2003年 | 1220篇 |
2002年 | 581篇 |
2001年 | 133篇 |
2000年 | 223篇 |
1999年 | 102篇 |
1998年 | 97篇 |
1997年 | 68篇 |
1996年 | 82篇 |
1995年 | 37篇 |
1994年 | 55篇 |
1993年 | 47篇 |
1992年 | 48篇 |
1991年 | 53篇 |
1990年 | 24篇 |
1989年 | 29篇 |
1988年 | 33篇 |
1985年 | 31篇 |
1984年 | 31篇 |
1983年 | 24篇 |
1982年 | 26篇 |
1981年 | 24篇 |
1969年 | 27篇 |
1968年 | 45篇 |
1967年 | 35篇 |
1966年 | 48篇 |
1965年 | 46篇 |
1963年 | 31篇 |
1960年 | 32篇 |
1959年 | 35篇 |
1958年 | 37篇 |
1957年 | 38篇 |
1956年 | 34篇 |
1955年 | 63篇 |
1954年 | 68篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
In this paper, the resilient control under the Denial-of-Service (DoS) attack is rebuilt within the framework of Joint Directors of Laboratories (JDL) data fusion model. The JDL data fusion process is characterized by the so-called Game-in-Game approach, where decisions are made at different layers. The interactions between different JDL levels are considered which take the form of Packet Delivery Rate of the communication channel. Some criterions to judge whether the cyber defense system is able to protect the underlying control system is provided. Finally, a numerical example is proposed to verify the validity of the proposed method. 相似文献
92.
Sez Atamturktur Zhifeng Liu Scott Cogan Hsein Juang 《Structural and Multidisciplinary Optimization》2015,51(3):659-671
Traditionally, model calibration is formulated as a single objective problem, where fidelity to measurements is maximized by adjusting model parameters. In such a formulation however, the model with best fidelity merely represents an optimum compromise between various forms of errors and uncertainties and thus, multiple calibrated models can be found to demonstrate comparable fidelity producing non-unique solutions. To alleviate this problem, the authors formulate model calibration as a multi-objective problem with two distinct objectives: fidelity and robustness. Herein, robustness is defined as the maximum allowable uncertainty in calibrating model parameters with which the model continues to yield acceptable agreement with measurements. The proposed approach is demonstrated through the calibration of a finite element model of a steel moment resisting frame. 相似文献
93.
Lionel March 《Nexus Network Journal》2015,17(3):697-721
The enigmatic Hypnerotomachia Poliphili published anonymously in 1499 has long posed puzzles for historians and other scholars. This present text argues that the volume can credibly be attributed, not to Francesca Colonna as is often done, but to the Renaissance humanist and polymath Leon Battista Alberti. Evidence for this is found in the unravelling of arithmogrammatical evidence sprinkled throughout the work, similar to those found in other of Alberti’s works. 相似文献
94.
Rasmus E. Christiansen Boyan S. Lazarov Jakob S. Jensen Ole Sigmund 《Structural and Multidisciplinary Optimization》2015,52(4):737-754
Resonance and wave-propagation problems are known to be highly sensitive towards parameter variations. This paper discusses topology optimization formulations for creating designs that perform robustly under spatial variations for acoustic cavity problems. For several structural problems, robust topology optimization methods have already proven their worth. However, it is shown that direct application of such methods is not suitable for the acoustic problem under consideration. A new double filter approach is suggested which makes robust optimization for spatial variations possible. Its effect and limitations are discussed. In addition, a known explicit penalization approach is considered for comparison. For near-uniform spatial variations it is shown that highly robust designs can be obtained using the double filter approach. It is finally demonstrated that taking non-uniform variations into account further improves the robustness of the designs. 相似文献
95.
Sabine Timpf 《Informatik-Spektrum》2008,31(1):70-74
Zusammenfassung Im Zeitalter der Informationsgesellschaft, so wurde postuliert, spielten r?umliche Distanzen keine Rolle mehr und unsere r?umliche
Mobilit?t n?hme ab. Die Mobilit?t in den letzten Jahren, speziell die Freizeitmobilit?t, hat hingegen zugenommen. Die Bereitstellung
ortsbezogener Dienste – ,,Location-based Services“ – unterstützt und f?rdert dieses Verhalten. 相似文献
96.
Aminollah Mahabadi Hamid Sarbazi-Azad Ebrahim Khodaie Keivan Navi 《The Journal of supercomputing》2008,45(1):1-14
This paper proposes an efficient parallel algorithm for computing Lagrange interpolation on k-ary n-cube networks. This is done using the fact that a k-ary n-cube can be decomposed into n link-disjoint Hamiltonian cycles. Using these n link-disjoint cycles, we interpolate Lagrange polynomial using full bandwidth of the employed network. Communication in the
main phase of the algorithm is based on an all-to-all broadcast algorithm on the n link-disjoint Hamiltonian cycles exploiting all network channels, and thus, resulting in high-efficiency in using network
resources. A performance evaluation of the proposed algorithm reveals an optimum speedup for a typical range of system parameters
used in current state-of-the-art implementations.
相似文献
Hamid Sarbazi-AzadEmail: Email: |
97.
This paper is concerned with the derivation of infinite schedules for timed automata that are in some sense optimal. To cover
a wide class of optimality criteria we start out by introducing an extension of the (priced) timed automata model that includes
both costs and rewards as separate modelling features. A precise definition is then given of what constitutes optimal infinite
behaviours for this class of models. We subsequently show that the derivation of optimal non-terminating schedules for such
double-priced timed automata is computable. This is done by a reduction of the problem to the determination of optimal mean-cycles
in finite graphs with weighted edges. This reduction is obtained by introducing the so-called corner-point abstraction, a
powerful abstraction technique of which we show that it preserves optimal schedules.
This work has been mostly done while visiting CISS at Aalborg University in Denmark and has been supported by CISS and by
ACI Cortos, a program of the French Ministry of Research. 相似文献
98.
Gemma Robles 《Journal of Logic, Language and Information》2008,17(2):161-181
In this paper, consistency is understood in the standard way, i.e. as the absence of a contradiction. The basic constructive
logic BKc4, which is adequate to this sense of consistency in the ternary relational semantics without a set of designated points, is
defined. Then, it is shown how to define a series of logics by extending BKc4 up to minimal intuitionistic logic. All logics defined in this paper are paraconsistent logics. 相似文献
99.
John Stachurski 《Computational Economics》2008,31(2):141-160
This paper studies fitted value iteration for continuous state numerical dynamic programming using nonexpansive function approximators.
A number of approximation schemes are discussed. The main contribution is to provide error bounds for approximate optimal
policies generated by the value iteration algorithm.
相似文献
100.
This work presents a driving system for a peristaltic micropump that is based on piezoelectric actuation. The effects of the
actuation sequence on pump performance are also considered. A valveless peristaltic micropump based on piezoelectric actuation
is designed and fabricated using microelectromechanical system technology. The pump has three parts––silicon, Pyrex glass
and commercially available bulk PZT (lead zirconate titanate) chips. The peristaltic micropump actuated by PZT chips comprises
three chambers that are in series. The driving system consists of an ATmega 8535 microprocessor, a high voltage power supply,
three differential amplifiers, a phase controller, an A/D converter, a 555 oscillator and an LCD module. It is supplied via
a 110 Vrms 60-Hz AC line and is programmable. The system can produce step-function signals with voltages of up to 100 Vpp and frequencies ranging from 10 Hz to 1 kHz, as the inputs for the pump. Fluid pumping with air is successfully demonstrated.
Additionally, 3-, 4- and 6-phase actuation sequences for the pump are designed and used to study the effects on pump performance,
as revealed by the flow rate and the displacement of a pump diaphragm. The experimental results show that the flow rate and
the displacement of the diaphragm actuated by the 4-phase sequence exceed those actuated by the 3- and 6-phase sequences.
A flow rate of 17.6 μl min−1 and a displacement of 2.91 μm (peak-to-peak) in 4-phase peristaltic motion are achieved at 100 Hz and 100 Vpp. The results demonstrate that the pump actuated in the 4-phase sequence is the most efficient. Consequently, the actuation
sequences can affect the pump performance. 相似文献