全文获取类型
收费全文 | 6114篇 |
免费 | 469篇 |
国内免费 | 59篇 |
专业分类
电工技术 | 74篇 |
综合类 | 23篇 |
化学工业 | 1386篇 |
金属工艺 | 95篇 |
机械仪表 | 279篇 |
建筑科学 | 141篇 |
矿业工程 | 9篇 |
能源动力 | 416篇 |
轻工业 | 760篇 |
水利工程 | 67篇 |
石油天然气 | 38篇 |
武器工业 | 1篇 |
无线电 | 785篇 |
一般工业技术 | 1331篇 |
冶金工业 | 96篇 |
原子能技术 | 55篇 |
自动化技术 | 1086篇 |
出版年
2024年 | 39篇 |
2023年 | 216篇 |
2022年 | 510篇 |
2021年 | 803篇 |
2020年 | 473篇 |
2019年 | 545篇 |
2018年 | 502篇 |
2017年 | 422篇 |
2016年 | 416篇 |
2015年 | 261篇 |
2014年 | 310篇 |
2013年 | 470篇 |
2012年 | 261篇 |
2011年 | 322篇 |
2010年 | 192篇 |
2009年 | 171篇 |
2008年 | 121篇 |
2007年 | 113篇 |
2006年 | 55篇 |
2005年 | 38篇 |
2004年 | 52篇 |
2003年 | 43篇 |
2002年 | 30篇 |
2001年 | 15篇 |
2000年 | 23篇 |
1999年 | 26篇 |
1998年 | 26篇 |
1997年 | 20篇 |
1996年 | 22篇 |
1995年 | 25篇 |
1994年 | 10篇 |
1993年 | 18篇 |
1992年 | 10篇 |
1991年 | 10篇 |
1990年 | 3篇 |
1989年 | 7篇 |
1988年 | 7篇 |
1987年 | 7篇 |
1986年 | 2篇 |
1985年 | 8篇 |
1984年 | 4篇 |
1983年 | 2篇 |
1982年 | 6篇 |
1981年 | 6篇 |
1979年 | 4篇 |
1978年 | 2篇 |
1977年 | 4篇 |
1976年 | 4篇 |
1963年 | 1篇 |
1961年 | 1篇 |
排序方式: 共有6642条查询结果,搜索用时 15 毫秒
1.
2.
3.
Chakraborty Debasish Zabir Salahuddin Muhammad Salim Chayabejara Apichet Chakraborty Goutam 《Telecommunication Systems》2004,25(3-4):299-315
Single point, sender based control does not scale well for multicast delivery. For applications, such as group video or teleconferencing a low total cost multicast tree is required. In this article we present a destination driven algorithm to minimize the total tree cost of multicast tree in a dynamic situation for the whole session duration. In this heuristic approach we considered the staying duration of participants are available at the time of joining. The performance of our algorithm is analyzed through extensive simulation and evaluated against several other existing dynamic multicast routing and also against one well known near optimum heuristic algorithm used for solving Steiner tree problem. We have further tested our algorithm using erroneous information given by the joining participants. Simulation results show that its performance does not degrade that much even when the range of error is considerably high, which proves the robustness of our algorithm. 相似文献
4.
This study demonstrates that state observers can be developed and applied to infer the composition profiles of reactive distillation columns from noise-contaminated temperature measurements. The design and implementation of a Kalman filter (KF) and a Luenberger observer (LO) are carried out, and their performances are quantitatively assessed. The reliability, accuracy, and robustness of the two designs method are examined and compared quantitatively. The design and implementation of a Luenberger observer are simpler and easier to carry out than those of a Kalman filter. On the other hand, a Kalman filter is found to be more robust to a noisy measurements, erroneous initial estimates, and model uncertainties. A Luenberger observer could be used for composition estimation of reactive distillation when an ideal model of the system can reasonably approximate the real system; otherwise, a Kalman filter is recommended to be applied in more practical situations. 相似文献
5.
Muhammad Maqbool Hugh H. Richardson Martin E. Kordesch 《Journal of Materials Science》2007,42(14):5657-5660
Thin films of Praseodymium doped AlN are deposited on silicon (111) substrates at 77 K and 950 K by rf magnetron sputtering
method. About 500–1000 nm thick films are grown at 100–200 watts RF power and 5–8 mTorr nitrogen, using a metal target of
Al with Pr. X-rays diffraction results show that films deposited at 77 K are amorphous and those deposited at 950 K are crystalline.
Cathodoluminescence studies are performed at room temperature and luminescence peaks are observed in a wide range from ultraviolet
to infrared region. The most intense peak is obtained in green at 526 nm from amorphous films as a result from 3P1→3H5 transition. In crystalline films the intense peak was obtain in red at 648 nm as a result from 3P0→3F2 transition. Films are thermally activated at 1300 K for half an hour in a nitrogen atmosphere. Thermal activation enhances
the intensity of luminescence. Two peaks at 488 nm and 505 nm merged after thermal activation, giving rise to a single peak
at 495 nm. 相似文献
6.
Adnan Köksal 《Journal of Infrared, Millimeter and Terahertz Waves》1997,18(8):1525-1537
A parametric study of linearly tapered slot antenna (LTSA) in air and a method for optimization of its pattern are presented. A method of moments code is utilized to investigate the behavior of LTSA’s as the length, height and the taper angle varies. It is shown that the antenna pattern can be improved using a top layer of dielectric material with varying permittivity. 相似文献
7.
Muhammad Nabeel Ghayur Anwarul Hassan Gilani 《European Food Research and Technology》2007,224(4):477-481
In this study, we describe the tracheal-relaxant and tocolytic activities of the methanol (ME) and aqueous (AQ) crude extracts
of ginger (rhizome of Zingiber officinale) in an attempt to rationalize its traditional use in disorders of airways and uterine hyperactivity. Both of the ginger extracts
dose-dependently relaxed K+ (80 mM) and carbachol (CCh, 1 μM)-induced contractions with more potency against K+, similar to that elicited by verapamil, a Ca2+ channel blocker. In isolated uterine preparations, the extracts suppressed the K+-induced contractions with respective EC50 values of 0.03 mg/ml (0.02–0.05, 95% CI) and 0.05 mg/ml (0.04–0.06). Activity-directed fractionation of AQ yielded an organic
and an aqueous fraction with the activities concentrated in the former. Both the crude extracts were found safe in mice up
to the oral dose of 5 g/kg when tested for acute toxicity for 24 h. The study shows that ginger possesses tracheal and uterine
smooth muscle relaxant activity, possibility mediated via Ca2+ channel blockade, justifying its use in disorders such as asthma, cough as well as in dysmenorrhoea and uterine and menstrual
spasms and congestion. 相似文献
8.
9.
本文研究了无线局域网中使信号频谱得到优化的一种简单OFDM子载波加载算法。此算法基于边缘自适应(Margin Adaptive)加载准则及其在室内无线信道上的性能。 相似文献
10.
In this work we present the discrete models for dynamic fracture of structures built of brittle materials. The models construction is based on Voronoi cell representation of the heterogeneous structure, with the beam lattice network used to model the cohesive and compressive forces between the neighboring cells. Each lattice component is a geometrically exact shear deformable beam which can describe large rigid body motion and the most salient fracture mechanisms. The latter can be represented through the corresponding form of the beam constitutive equations, which are derived either at microscale with random distribution of material properties or at a mesoscale with average deterministic values. The proposed models are also placed within the framework of dynamics, where special attention is paid to constructing the lattice network mass matrix as well as the corresponding time-stepping schemes. Numerical simulations of compression and bending tests is given to illustrate the models performance. 相似文献