全文获取类型
收费全文 | 5357篇 |
免费 | 274篇 |
国内免费 | 8篇 |
专业分类
电工技术 | 61篇 |
综合类 | 3篇 |
化学工业 | 1410篇 |
金属工艺 | 67篇 |
机械仪表 | 94篇 |
建筑科学 | 208篇 |
矿业工程 | 8篇 |
能源动力 | 203篇 |
轻工业 | 851篇 |
水利工程 | 54篇 |
石油天然气 | 26篇 |
无线电 | 377篇 |
一般工业技术 | 717篇 |
冶金工业 | 489篇 |
原子能技术 | 18篇 |
自动化技术 | 1053篇 |
出版年
2024年 | 7篇 |
2023年 | 57篇 |
2022年 | 160篇 |
2021年 | 221篇 |
2020年 | 155篇 |
2019年 | 160篇 |
2018年 | 184篇 |
2017年 | 154篇 |
2016年 | 200篇 |
2015年 | 160篇 |
2014年 | 207篇 |
2013年 | 419篇 |
2012年 | 329篇 |
2011年 | 457篇 |
2010年 | 278篇 |
2009年 | 271篇 |
2008年 | 283篇 |
2007年 | 255篇 |
2006年 | 205篇 |
2005年 | 138篇 |
2004年 | 156篇 |
2003年 | 124篇 |
2002年 | 123篇 |
2001年 | 83篇 |
2000年 | 72篇 |
1999年 | 76篇 |
1998年 | 165篇 |
1997年 | 107篇 |
1996年 | 86篇 |
1995年 | 60篇 |
1994年 | 51篇 |
1993年 | 48篇 |
1992年 | 12篇 |
1991年 | 24篇 |
1990年 | 17篇 |
1989年 | 10篇 |
1988年 | 8篇 |
1987年 | 11篇 |
1986年 | 9篇 |
1985年 | 17篇 |
1984年 | 8篇 |
1983年 | 8篇 |
1982年 | 12篇 |
1981年 | 6篇 |
1980年 | 7篇 |
1978年 | 3篇 |
1977年 | 5篇 |
1976年 | 16篇 |
1975年 | 4篇 |
1967年 | 3篇 |
排序方式: 共有5639条查询结果,搜索用时 15 毫秒
1.
In this article, a general synthesis method is proposed for the design of discontinuous feedback strategies leading to asymptotically stabilizing sliding regimes. The method is applicable to the class of nonlinear dynamical systems possessing constant equilibrium points. A family of nonlinear stabilizing sliding manifolds, parametrized by generic desired equilibrium point, is specified on the basis of the extended linearization approach. Some examples including simulations are presented for illustrative purposes.
Editor: S. Zak 相似文献
2.
Christian P. Romero Jonathan I. Avila Edgardo Cisternas Guerau B. Cabrera Alejandro L. Cabrera Kristiaan Temst Margriet J. Van Bael 《Journal of Materials Science》2007,42(18):7667-7672
Hydrogen desorption curves were obtained from a sample composed of a square arrangement of Co dots with average diameter of
4.4 μm, separated by a distance of 11.6 μm. A macroscopic sample of Co dots grown on a 2.5 × 2.5 cm Si substrate was made
by standard lithographic techniques and used in these experiments. Thermal programmed desorption (TPD) was performed under
ultra-high vacuum conditions. Hydrogen TPD curves were obtained from a 1 × 1 cm Co dots samples displaying a maximum of intensity
at 425 K. Hydrogen TPD curve was also obtained from 1 cm× 1 cm samples of Co films and Co foils for comparison. The hydrogen
TPD curves have decreasing intensity from the Co foils to the Co dots and finally to the Co films. This indicates that there
are more sites for hydrogen adsorption on the Co dots than in the Co films. This is a surprising result because there is approximately
8.7 times less Co atoms exposed in the Co dots that in the Co film sample. A desorption energy of 27 kcal/mol was obtained
for the Co dots suggesting that hydrogen is adsorbed on an hcp hollow site of the Co dot crystalline structure. 相似文献
3.
Lithiasis may develop in the prostate loge following prostate surgery. Calculus formation in the prostate can be ascribed basically to foreign bodies, residual adenomatous spheroids and clots or fragments of sphacelous mucosa in the presence of a stenotic area after surgery and/or infection. The diagnosis is based on the physical examination and particularly on the radiological findings. Treatment is by open surgery or endoscopic or extracorporeal lithotripsy. 相似文献
4.
M Pan J Suárez de Lezo A Medina M Romero E Hernández J Segura F Melian F Wangüemert M Landin F Benítez M Amat F Velasco A Torres 《Canadian Metallurgical Quarterly》1997,80(10):1336-1338
Two hundred twenty-eight patients with successful coronary stent implantation were randomized either to protamine administration and femoral sheath removal (group I, n = 117) or no heparin neutralization and delayed sheath removal (group II, n = 111). The hospital stay after treatment was shorter in patients receiving protamine; therefore, protamine use for neutralizing circulating heparin may be safely administered immediately after stent implantation. 相似文献
5.
MP Romero A García-Perga?eda JM Guerrero C Osuna 《Canadian Metallurgical Quarterly》1998,12(13):1401-1408
Melatonin has been suggested as a physiological antagonist of calmodulin. In this work, we have characterized melatonin binding sites in Xenopus laevis oocyte membranes. Binding of [125I]melatonin by X. laevis oocyte membranes fulfills all criteria for binding to a receptor site. Binding was dependent on time, temperature, and membrane concentration and was stable, reversible, saturable, and specific. The binding site was also pharmacologically characterized. Stoichiometric studies showed a high-affinity binding site with a Kd of 1.18 nM. These data are in close agreement with data obtained from kinetic studies (Kd=0.12 nM). In competition studies, we observed a low-affinity binding site (Kd=63.41 microM). Moreover, the binding site was characterized as calmodulin. Thus, binding was dependent on calcium and blocked by anti-CaM antibodies in a concentration-dependent manner. Calmodulin inhibitor chlorpromazine also inhibited binding of the tracer. From these results, it is suggested that membrane-bound calmodulin acts as a melatonin binding site in Xenopus laevis oocytes, where it might couple cellular activities to rhythmic circulating levels of melatonin. This hypothesis correlates with the previous findings describing melatonin as a physiological antagonist of calmodulin. 相似文献
6.
Luiz Antonio Alcântara Pereira Miguel Hiroo Hirata Nelson Manzanares Filho 《Journal of Wind Engineering & Industrial Aerodynamics》2004,92(6):477-491
Two-dimensional, unsteady flow around bodies of complex geometry (or multiple bodies) at high Reynolds number is simulated using the vortex method. This method is modified to take into account the sub-grid scale phenomena through a second order velocity structure function model adapted to the Lagrangian scheme. The dynamics of the body wake is computed using the convection-diffusion splitting algorithm; the convection process is carried out with a Lagrangian Adams-Bashforth time-marching scheme and the diffusion process is simulated using the random walk method. The pressure distribution is obtained using an integral equation derived from the pressure Poisson equation, which was first developed for a single body. Results for the numerical simulation around a linear cascade of airfoils are presented. As the flow is periodic in the y direction, the discrete vortex shedding need only be considered for a reference airfoil. The flow characteristics around the NACA 65-410 series airfoils are calculated and comparisons are made with results available in the literature. 相似文献
7.
Bedload Transport in Alluvial Channels 总被引:1,自引:0,他引:1
Miguel Bravo-Espinosa W. R. Osterkamp Vicente L. Lopes 《Canadian Metallurgical Quarterly》2003,129(10):783-795
Hydraulic, sediment, land-use, and rock-erosivity data of 22 alluvial streams were used to evaluate conditions of bedload transport and the performance of selected bedload-transport equations. Transport categories of transport-limited (TL), partially transport-limited (PTL), and supply-limited (SL) were identified by a semiquantitative approach that considers hydraulic constraints on sediment movement and the processes that control sediment availability at the basin scale. Equations by Parker et al. in 1982, Schoklitsch in 1962, and Meyer-Peter and Muller in 1948 adequately predicted sediment transport in channels with TL condition, whereas the equations of Bagnold in 1980, and Schoklitsch, in 1962, performed well for PTL and SL conditions. Overall, the equation of Schoklitsch predicted well the measured bedload data for eight of 22 streams, and the Bagnold equation predicted the measured data in seven streams. 相似文献
8.
9.
Ana Mafalda RibeiroJosé Miguel Loureiro 《Chemical engineering science》2002,57(9):1621-1626
The system ASC carbon filter/cyanogen chloride was studied by simulation. Three filter configurations and several models, taking into account Langmuir adsorption and second-order reaction between the adsorbed toxic vapour and the active metal on the surface, were developed.The effects of axial dispersion, number of reaction units, film mass transfer units and intraparticle mass transfer resistance on the breakthrough time were studied.Simulation results show that a complex model should be used in order to predict with reasonable accuracy the protection imparted by these filters. 相似文献
10.
Miguel J. Bagajewicz Vasilios Manousiouthakis 《American Institute of Chemical Engineers》1992,38(11):1769-1800
This article introduces the “state space” conceptual framework to process synthesis, which is used to provide a novel representation of a distillation network as a composite heat- and mass-exchange network. This representation suggests that distillation network synthesis may best be viewed as an interacting heat- and mass-exchange network synthesis problem. In that regard, familiar tools (such as pinch diagrams) from both heat-exchange network (HEN) and mass-exchange network (MEN) synthesis are shown to be of use in arriving at energy-efficient distillation network designs. Examples of propylene-propane and solvent-water separations are used to illustrate the proposed conceptual framework. 相似文献