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991.
We consider the problem of static transmission-power assignment for lifetime maximization of a wireless sensor network with stationary nodes operating in a data-gathering scenario. Using a graph-theoretic approach, we propose two distributed algorithms, MLS and BSpan, that construct spanning trees with minimum maximum (minmax) edge cost. MLS is based on computation of minmax-cost paths from a reference node, while BSpan performs a binary search over the range of power levels and exploits the wireless broadcast advantage. We also present a simple distributed method for pruning a graph to its Relative Neighborhood Graph, which reduces the worst-case message complexity of MLS under natural assumptions on the path-loss. In our network simulations both MLS and BSpan significantly outperform the recently proposed Distributed Min–Max Tree algorithm in terms of number of messages required. 相似文献
992.
Linnéa Rosenbaum Per Löwenborg Håkan Johansson 《Circuits, Systems, and Signal Processing》2010,29(1):103-133
This paper introduces two classes of cosine-modulated causal and stable filter banks (FBs) with near perfect reconstruction
(NPR) and low implementation complexity. Both classes have the same infinite-length impulse response (IIR) analysis FB but
different synthesis FBs utilizing IIR and finite-length impulse response (FIR) filters, respectively. The two classes are
preferable for different types of specifications. The IIR/FIR FBs are preferred if small phase errors relative to the magnitude
error are desired, and vice versa. The paper provides systematic design procedures so that PR can be approximated as closely
as desired. It is demonstrated through several examples that the proposed FB classes, depending on the specification, can
have a lower implementation complexity compared to existing FIR and IIR cosine-modulated FBs (CMFBs). The price to pay for
the reduced complexity is generally an increased delay. Furthermore, two additional attractive features of the proposed FBs
are that they are asymmetric in the sense that one of the analysis and synthesis banks has a lower computational complexity
compared to the other, which can be beneficial in some applications, and that the number of distinct coefficients is small,
which facilitates the design of FBs with large numbers of channels. 相似文献
993.
Jean-Marc JéZéquel 《电信纪事》1995,50(11-12):848-858
We study in this paper the feasibility of using general purpose distributed memory parallel computers to implement some functions of high speed networks. We concentrate on the switching problem of the xtp high performance protocol (dealing with the network and transport layers of the osi stack), and on smds (switched multimegabit data service). We use methods and tools developed within the Pampa project (parallelizing methods, formal specification tools) to parallelize and prototype these kinds of switching systems on parallel architectures, and to make performance evaluations. 相似文献
994.
Vallati Carlo Mingozzi Enzo Tanganelli Giacomo Buonaccorsi Novella Valdambrini Nicola Zonidis Nikolaos Martínez Belén Mamelli Alessandro Sommacampagna Davide Anggorojati Bayu Kyriazakos Sofoklis Prasad Neeli Nieto Francisco Javier Rodriguez Oliver Barreto 《Wireless Personal Communications》2016,87(3):1071-1091
Wireless Personal Communications - The integration of everyday objects into the Internet represents the foundation of the forthcoming Internet of Things (IoT). Smart objects will be the building... 相似文献
995.
Ileana Recalde Andrés. F. Gualdrón-Reyes Carlos Echeverría-Arrondo Alexis Villanueva-Antolí Jorge Simancas Jhonatan Rodriguez-Pereira Marcileia Zanatta Iván Mora-Seró Victor Sans 《Advanced functional materials》2023,33(8):2210802
The use of non-toxic and low-cost vitamins like α-tocopherol (α-TCP, vitamin E) to improve the photophysical properties and stability of perovskite nanocrystals (PNCs), through post-synthetic ligand surface passivation, is demonstrated for the first time. Especially interesting is its effect on CsPbI3 the most unstable inorganic PNC. Adding α-TCP produces that the photoluminescence quantum yield (PLQY) of freshly prepared and aged PNCs achieves values of ≈98% and 100%, respectively. After storing 2 months under ambient air and 60% relative humidity, PLQY is maintained at 85% and 67%, respectively. α-TCP restores the PL features of aged CsPbI3 PNCs, and mediates the radiative recombination channels by reducing surface defects. In addition, the combination of α-TCP and PNCs facilitates the chemical formulation to prepare PNCs-acrylic polymer composites processable by additive manufacturing. This enables the development of complex shaped parts with improved luminescent features and long-term stability for 4 months, which is not possible for non-modified PNCs. A PLQY ≈92% is reached in the 3D printed polymer/PNC composite, the highest value obtained for a red-emitting composite solid until now as far as it is known. The passivation shell provided by α-TCP makes that PNCs inks do not suffer any degradation process avoiding the contact with the environment and preserve their properties after reacting with polar monomers during composite polymerization. 相似文献
996.
Eduardo Pompeo da Silva Mineiro Débora Christina Muchaluat-Saade 《International Journal of Wireless Information Networks》2014,21(3):223-237
This work presents an admission control mechanism for multi-hop wireless mesh networks based on the IEEE 802.11 standard and the OLSR routing protocol. This mechanism, called CAC-OLSR, aims at ensuring that traffic flows with quality of service (QoS) requirements, especially voice and video, are only admitted in the mesh network if it has available resources in order to provide flow requirements. In addition, QoS requirements of previously admitted traffic flows cannot be violated. The proposal was evaluated with NS-2 and Evalvid simulations. 相似文献
997.
C. R. Helms J. L. Meléndez H. G. Robinson S. Holander J. Hasan S. Halepete 《Journal of Electronic Materials》1995,24(9):1137-1142
The strategy and status of a process simulator for the flexible manufacture of HgCdTe infrared focal plane arrays is described.
It has capabilities to simulate Hg vacancy and interstitial effects and cation impurity diffusion, for various boundary conditions
in one dimension. Numerical complexity of these problems stems from the necessity of solving diffusion equations for each
defect that are coupled to each other via nonlinear interaction terms. The simulator has already led to the prediction of
heretofore unexplained experimental data. Current extensions of the one-dimensional simulator planned over the next few years
include the addition of Te antisites, antisite-Hg vacancy pairs, and In-Hg vacancy pairs, ion implantation, and various energetic
processes (such as ion milling). The sequential effect of various processes will be possible with the input to the simulator
looking much like a process run sheet. 相似文献
998.
Metal Organic Framework Crystals in Mixed‐Matrix Membranes: Impact of the Filler Morphology on the Gas Separation Performance 下载免费PDF全文
Anahid Sabetghadam Beatriz Seoane Damla Keskin Nicole Duim Tania Rodenas Salman Shahid Sara Sorribas Clément Le Guillouzer Guillaume Clet Carlos Tellez Marco Daturi Joaquin Coronas Freek Kapteijn Jorge Gascon 《Advanced functional materials》2016,26(18):3154-3163
Mixed‐matrix membranes comprising NH2‐MIL‐53(Al) and Matrimid or 6FDA‐DAM have been investigated. The metal organic framework (MOF) loading has been varied between 5 and 20 wt%, while NH2‐MIL‐53(Al) with three different morphologies, nanoparticles, nanorods, and microneedles has been dispersed in Matrimid. The synthesized membranes have been tested in the separation of CO2 from CH4 in an equimolar mixture. At 3 bar and 298 K for 8 wt% MOF loading, incorporation of NH2‐MIL‐53(Al) nanoparticles leads to the largest improvement compared to nanorods and microneedles. The incorporation of the best performing filler, i.e., NH2‐MIL‐53(Al) nanoparticles, into the highly permeable 6FDA‐DAM has a larger effect, and the CO2 permeability increases up to 85% with slightly lower selectivities for 20 wt% MOF loading. Specifically, these membranes have a permeability of 660 Barrer with a CO2/CH4 separation factor of 28, leading to a performance very close to the Robeson limit of 2008. Furthermore, a new non‐destructive technique based on Raman spectroscopy mapping is introduced to assess the homogeneity of the filler dispersion in the polymer matrix. The MOF contribution can be calculated by modeling the spectra. The determined homogeneity of the MOF filler distribution in the polymer is confirmed by focused ion beam scanning electron microscopy analysis. 相似文献
999.
1000.