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991.
992.
In this study, TiC/TC4 composites were fabricated using selective laser melting (SLM), and the deformation mechanism and fracture characteristics of the composites with nano-sized TiC particles formed in situ were studied. The experimental results showed that the rapid melting and solidification characteristics of SLM and the Marangoni effect of the liquid pool promoted a considerably homogeneous dispersion of the in situ-formed nanoscale-TiC reinforcement in the TiC/TC4 composites. In particular, an enhanced compressive strength of 1490.2 MPa and a considerable fracture elongation of 21.5% were simultaneously achieved for the TiC/TC4 composites, which could be attributed to the load transfer effect and the formation of denser and more uniformly distributed dimples. Combined with the finite element (FE) analysis, the uneven stress distribution in the shear band of the TiC/TC4 composites led to the fracture. Further, the fracture surface analysis showed that the in situ nanoscale TiC reinforcement promoted the fracture of microbubbles from the α/β interface with the concentrated distribution of the V element to the interface between TiC and the Ti matrix because of the load transfer, which promoted the uniform distribution of the V element in the dimple. 相似文献
993.
Daniel Ritzberger Johannes Höflinger Zhang Peng Du Christoph Hametner Stefan Jakubek 《International Journal of Hydrogen Energy》2021,46(21):11878-11893
In order to mitigate the degradation and prolong the lifetime of polymer electrolyte membrane fuel cells, advanced, model-based control strategies are becoming indispensable. Thereby, the availability of accurate yet computationally efficient fuel cell models is of crucial importance. Associated with this is the need to efficiently parameterize a given model to a concise and cost-effective experimental data set. A challenging task due to the large number of unknown parameters and the resulting complex optimization problem. In this work, a parameterization scheme based on the simultaneous estimation of multiple structured state space models, obtained by analytic linearization of a candidate fuel cell stack model, is proposed. These local linear models have the advantage of high computational efficiency, regaining the desired flexibility required for the typically iterative task of model parameterization. Due to the analytic derivation of the local linear models, the relation to the original parameters of the non-linear model is retained. Furthermore, the local linear models enable a straight-forward parameter significance and identifiability analysis with respect to experimental data. The proposed method is demonstrated using experimental data from a 30 kW commercial polymer electrolyte membrane fuel cell stack. 相似文献
994.
Liangyun Lan Chunlin Qiu Dewen Zhao Xiuhua Gao Linxiu Du 《Journal of Materials Science》2012,47(11):4732-4742
Martensite–austenite (M–A) constituent formed during welding is generally recognized as an important factor to decrease the
toughness of welded joint. In this article, the morphology and chemical composition of M–A constituent in the low carbon bainitic
steel welded joint was analysed in detail by means of optical microscope, transmission electron microscope and scanning electron
microscope with electron probe microanalysis. The experimental results show that the M–A constituent formed in the different
sub-zones presents different morphologies and different amounts. The maximum amount of M–A constituent occurs in the coarse
grained heat affected zone (HAZ). It is evident that the carbon atoms segregate on the M–A constituent and carbon concentration
on the slender M–A constituent is higher than that on the massive M–A constituent. Meanwhile, the distribution profile of
silicon on the M–A constituent shows an obvious inhomogeneity. Most of M–A constituents have a twinned structure and/or a
high dislocation density. According to impact testing results, the crack initiation energy in the HAZ specimens deteriorates
significantly because the large M–A constituent can assist the formation of cleavage crack. On the other hand, the coarse
prior austenite grain in the HAZ lowers the crack propagation energy. 相似文献
995.
Xiaojun Du Wenge Wu Chunhua An Yunping Cheng Xinyu Zhang Youyi Sun Yaqing Liu 《国际能源研究杂志》2016,40(12):1731-1738
Three‐dimensional (3D) graphene network deposition on Ni foam without any conductive agents and polymer binders was successfully synthesized by radio frequency magnetron sputtering at low temperature. The direct and close contact between graphene and Ni foam is beneficial to the enhanced conductivity of the electrode, as well as the improvement of ion diffusion/transport into the electrode. As a result, the 3D graphene network deposition on Ni foam electrode delivered a high specific capacitance of 122.0 F g−1 at 1.0 A g−1 and excellent cycle stability with capacitance retention of 99.0% after 1000 charge–discharge cycles. The work shows a new way to facile synthesis of 3D graphene network for various applications in the future. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
996.
港口是城市发展的推进器,城市的诞生、发展和繁荣,大都是伴随着港口的形成、港口经济的发展而发展的。本文通过对清浦港业新城概念性规划设计的介绍,探讨了以港口产业的为核心的港业新城的打造途径,以及其对社会经济发展的推动作用。 相似文献
997.
998.
In this paper, the mixed Navier–Stokes/Darcy problem which describes a fluid flow filtrating through porous media is considered. Based on two-grid discretizations, two local and parallel finite element algorithms for solving this mixed model are proposed. Numerical analysis and experiments are presented to show the efficiency and effectiveness of the local and parallel finite element algorithms. 相似文献
999.
Chong Shen Wencai Du Robert Atkinson Kae Hsiang Kwong 《Wireless Personal Communications》2012,62(2):329-361
We propose a dynamic mobility management framework for Internet Protocol version 6 (IPv6) and policy enforcement enabled heterogenous
wireless networks. Policies and policy rules are defined depending on network infrastructure facilities, service agreements
and negotiation results. Each traffic is coupled with an identifiable traffic flow while the heterogenous interface flow bindings
are regulated by polices. The network selection, flow distribution, handovers and mobility procedures are flexible and we
propose to improve the decision making via Multiple Attributes Decision Making (MADM). Techniques considered in the framework
include the IPv6 based Network Mobility (NEMO), multihoming capability, transparent vertical handovers, horizontal handovers
and dynamic policy enforcement matching process to improve the Quality of Service (QoS), Quality of Experience (QoE) and ubiquitous
connectivity. A experiment testbed and simulation models have been constructed to verify the mobility framework performance
in a heterogeneous WiFi, WiMax and UMTS hybrid environment. 相似文献
1000.
Using a password manager is known to be more convenient and secure than not using one, on the assumption that the password manager itself is safe. However recent studies show that most popular password managers have security vulnerabilities that may be fooled to leak passwords without users’ awareness. In this paper, we propose a new password manager, SplitPass, which vertically separates both the storage and access of passwords into two mutually distrusting parties. During login, all the parties will collaborate to send their password shares to the web server, but none of these parties will ever have the complete password, which significantly raises the bar of a successful attack to compromise all of the parties. To retain transparency to existing applications and web servers, SplitPass seamlessly splits the secure sockets layer (SSL) and transport layer security (TCP) sessions to process on all parties, and makes the joining of two password shares transparent to the web servers. We have implemented SplitPass using an Android phone and a cloud assistant and evaluated it using 100 apps from top free apps in the Android official market. The evaluation shows that SplitPass securely protects users’ passwords, while incurring little performance overhead and power consumption. 相似文献