全文获取类型
收费全文 | 1384篇 |
免费 | 60篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 28篇 |
综合类 | 3篇 |
化学工业 | 352篇 |
金属工艺 | 12篇 |
机械仪表 | 18篇 |
建筑科学 | 58篇 |
矿业工程 | 1篇 |
能源动力 | 42篇 |
轻工业 | 214篇 |
水利工程 | 13篇 |
石油天然气 | 1篇 |
无线电 | 105篇 |
一般工业技术 | 155篇 |
冶金工业 | 231篇 |
原子能技术 | 10篇 |
自动化技术 | 202篇 |
出版年
2023年 | 6篇 |
2022年 | 19篇 |
2021年 | 19篇 |
2020年 | 18篇 |
2019年 | 18篇 |
2018年 | 23篇 |
2017年 | 18篇 |
2016年 | 21篇 |
2015年 | 25篇 |
2014年 | 41篇 |
2013年 | 54篇 |
2012年 | 51篇 |
2011年 | 68篇 |
2010年 | 55篇 |
2009年 | 71篇 |
2008年 | 68篇 |
2007年 | 71篇 |
2006年 | 46篇 |
2005年 | 53篇 |
2004年 | 41篇 |
2003年 | 44篇 |
2002年 | 43篇 |
2001年 | 31篇 |
2000年 | 29篇 |
1999年 | 31篇 |
1998年 | 50篇 |
1997年 | 41篇 |
1996年 | 37篇 |
1995年 | 32篇 |
1994年 | 18篇 |
1993年 | 27篇 |
1992年 | 19篇 |
1991年 | 25篇 |
1990年 | 15篇 |
1989年 | 17篇 |
1988年 | 16篇 |
1987年 | 12篇 |
1986年 | 19篇 |
1985年 | 10篇 |
1984年 | 14篇 |
1983年 | 15篇 |
1982年 | 8篇 |
1981年 | 16篇 |
1980年 | 6篇 |
1979年 | 10篇 |
1978年 | 11篇 |
1977年 | 6篇 |
1976年 | 6篇 |
1975年 | 6篇 |
1973年 | 6篇 |
排序方式: 共有1445条查询结果,搜索用时 15 毫秒
41.
No Heading We present vibrating wire viscometer experiments in concentrated and dilute 3He-4He mixtures showing that the slip length may become orders of magnitude larger than the mean free path due to increased specular scattering of the 3He quasiparticles with the superfluid 4He film on the wire. The experimental results are in good agreement with a recent theory for slip which accounts for the cylindrical geometry of the wire and for velocity slip in directions normal as well as tangential to the surface of the wire.PACS numbers: 67.60.Fp, 51.20.+d 相似文献
42.
In this paper we will present a graph-transformation based method for the verification of heterogeneous first order logic (FOL) and Euler/Venn proofs. It has been shown that a special collection of directed acyclic graphs (DAGs) can be used interchangeably with Euler/Venn diagrams in reasoning processes [4]. Thus, proofs which include Euler/Venn diagrams can be thought of as proofs with DAGs where steps involving only Euler/Venn diagrams can be treated as particular DAG transformations. In the work reported here, we will show how the characterization of these manipulations can be used to verify Euler/Venn proofs. Also, a method for verifying the use of heterogeneous Euler/Venn and FOL reasoning rules will be presented that is also based upon DAG transformations. 相似文献
43.
Smith E Lally F Stone MA Shaw JS Nash GB Buckley CD Ed Rainger G 《Microscopy research and technique》2006,69(11):875-884
The use of fluorescent probes that allow visualization of leukocyte-endothelial cell (EC) interactions has greatly informed our understanding of leukocyte recruitment. However, effects of these agents on the biological functions of leukocytes are poorly described, leading to concerns about the interpretation of such data. Here we used two flow-based neutrophil adhesion assays to compare the effects of phase contrast illumination (PCI) with high intensity illumination (HII) used for fluorescent microscopy, in the presence or absence of five commonly used fluorochromes. Isolated neutrophils were either (1) perfused across P-selectin to establish a population of rolling cells, which were subsequently activated with fMLP; or (2) perfused across EC activated with TNF-alpha. In the absence of fluorescent dyes, HII did not affect levels of leukocyte adhesion; however, subsequent neutrophil behavior was dramatically altered when compared with cells under PCI, for example, dramatically reducing their migration velocities. In the presence of fluorescent dyes, the effects of HII were exacerbated, although the precise nature of the biological effects of these probes was agent specific. Thus, for the first time, our experiments describe the effects of fluorescent microscopy on the separate stages of the neutrophil recruitment process and reveal a previously unsuspected effect of HII on neutrophil migration. 相似文献
44.
Balamurugan A Benhayoune H Kannan S Laquerriere P Michel J Balossier G Ferreira JM 《Microscopy research and technique》2008,71(9):684-688
The present study deals with the short-term physicochemical reactions at the interface between bioactive glass particles [55SiO(2)-20CaO-9P(2)O(5)-12Na(2)O-4MgO. mol%] and biological fluid (Dulbecco Modified Eagle's Medium (DMEM)). The physicochemical reactions within the interface are characterized by scanning transmission electron microscopy (TEM) (STEM) associated with Energy-dispersive X-ray spectroscopy (EDXS). Microanalysis of diffusible ions such as sodium, potassium, or oxygen requires a special care. In the present investigation the cryo-technique was adopted as a suitable tool for the specimen preparation and characterization. Cryosectioning is essential for preserving the native distribution of ions so that meaningful information about the local concentrations can be obtained by elemental microanalysis. The bioglass particles immersed in biological fluid for 24 h revealed five reaction stages: (i) dealkalization of the surface by cationic exchange (Na(+), Ca(2+) with H(+) or H(3)O(+)); (ii) loss of soluble silica in the form of Si(OH)(4) to the solution resulting from the breakdown of Si--O--Si bonds (iii); repolymerization of Si(OH)(4) leading to condensation of SiO(2)); (iv) migration of Ca(2+) and PO(4) (3-) to the surface through the SiO(2)-rich layer to form CaO-P(2)O(5) film; (v) crystallization of the amorphous CaO-P(2)O(5) by incorporating OH-- or CO(3) (2-) anions with the formation of three different surface layers on the bioactive glass periphery. The thickness of each layer is approximately 300 nm and from the inner part to the periphery they consist of Si--OH, which permits the diffusion of Ca(2+) and PO(4) (3-) ions and the formation of the middle Ca--P layer, and finally the outer layer composed of Na--O, which acts as an ion exchange layer between Na(+) ions and H(+) or H(3)O(+) from the solution. 相似文献
45.
Camilo Zúñiga Gerard Lligadas Juan Carlos Ronda Marina Galià Virginia Cádiz 《Polymer》2012,53(15):3089-3095
This work concerns the investigation of porous polybenzoxazines based on the non-toxic renewable diphenolic acid. The approach described relies on the in situ generation of foaming agent (CO2) during the thermal curing. For this purpose, the previously synthesized benzoxazine monomer from diphenolic acid was thermally polymerized at different temperatures. As the beginning of decarboxylation is about 200 °C, we selected five foaming temperatures (Tf) ranging from 190 to 230 °C. The influence of the foaming temperature on the cellular structure and its dependency on final properties is discussed. 相似文献
46.
Camilo Zúñiga Gerard Lligadas Juan C. Ronda Marina Galià Virginia Cádiz 《Polymer》2012,53(8):1617-1623
The reaction of mixtures of renewable diphenolic acid (DPA) and its methylesterbenzoxazine derivative (MDP-Bz) has been studied. The DPA was introduced to lower the high temperature needed to complete the curing of the pure benzoxazine. In this way, samples with different DPA/MDP-Bz ratio (0, 2, 5, 10 and 25% of DPA) were investigated. Moreover, high performance flame retardant thermosetting resins with phosphorus were prepared through the mixture of MDP-Bz and a DPA-phosphazene derivative (DPA-PPZ). The curing behavior of these materials was studied by differential scanning calorimetry (DSC). Finally, the properties of the materials were evaluated by termogravimetric analysis (TGA), dynamic mechanical analysis (DMTA), tensile measurements, limiting oxygen index (LOI) and UL-94 Burn Test. 相似文献
47.
Horacio Cardenas Daniel Arango Courtney Nicholas Silvia Duarte Gerard J. Nuovo Wei He Oliver H. Voss M. Elba Gonzalez-Mejia Denis C. Guttridge Erich Grotewold Andrea I. Doseff 《International journal of molecular sciences》2016,17(3)
The increasing prevalence of inflammatory diseases and the adverse effects associated with the long-term use of current anti-inflammatory therapies prompt the identification of alternative approaches to reestablish immune balance. Apigenin, an abundant dietary flavonoid, is emerging as a potential regulator of inflammation. Here, we show that apigenin has immune-regulatory activity in vivo. Apigenin conferred survival to mice treated with a lethal dose of Lipopolysaccharide (LPS) restoring normal cardiac function and heart mitochondrial Complex I activity. Despite the adverse effects associated with high levels of splenocyte apoptosis in septic models, apigenin had no effect on reducing cell death. However, we found that apigenin decreased LPS-induced apoptosis in lungs, infiltration of inflammatory cells and chemotactic factors’ accumulation, re-establishing normal lung architecture. Using NF-κB luciferase transgenic mice, we found that apigenin effectively modulated NF-κB activity in the lungs, suggesting the ability of dietary compounds to exert immune-regulatory activity in an organ-specific manner. Collectively, these findings provide novel insights into the underlying immune-regulatory mechanisms of dietary nutraceuticals in vivo. 相似文献
48.
To advance the design of a multimegawatt vertical‐axis wind turbine (VAWT), application‐specific airfoils need to be developed. In this research, airfoils are tailored for a VAWT with variable pitch. A genetic algorithm is used to optimise the airfoil shape considering a balance between the aerodynamic and structural performance of airfoils. At rotor scale, the aerodynamic objective aims to create the required optimal loading while minimising losses. The structural objective focusses on maximising the bending stiffness. Three airfoils from the Pareto front are selected and analysed using the actuator cylinder model and a prescribed‐wake vortex code. The optimal pitch schedule is determined, and the loadings and power performance are studied for different tip‐speed ratios and solidities. The comparison of the optimised airfoils with similar airfoils from the first generation shows a significant improvement in performance, and this proves the necessity to properly select the airfoil shape. 相似文献
49.
This article introduces and provides the context for the themed section on mobile communication in Asia. It suggests that much work remains to be done in adequately grasping the new mobile, mediated face of communication in the very diverse Asian region. It also suggests that such a new direction in research needs to go hand in hand with rethinking the conceptual and theoretical bases of mobile, and indeed, Internet and computer‐mediated communication. 相似文献
50.
基建仓库项目位于莱瓦顿的Harlingervaart运河岸边,作为周边建筑的仓库,它具有独特的趣味性良好的形体感,因此被认为是立于运河沿岸广场上的一座雕塑。建筑的入口处挑出悬臂,并且顺势突出建筑南侧的体量 相似文献