全文获取类型
收费全文 | 6547篇 |
免费 | 274篇 |
国内免费 | 17篇 |
专业分类
电工技术 | 73篇 |
综合类 | 7篇 |
化学工业 | 1534篇 |
金属工艺 | 107篇 |
机械仪表 | 148篇 |
建筑科学 | 327篇 |
矿业工程 | 9篇 |
能源动力 | 226篇 |
轻工业 | 540篇 |
水利工程 | 61篇 |
石油天然气 | 26篇 |
武器工业 | 2篇 |
无线电 | 581篇 |
一般工业技术 | 1107篇 |
冶金工业 | 913篇 |
原子能技术 | 34篇 |
自动化技术 | 1143篇 |
出版年
2023年 | 67篇 |
2022年 | 107篇 |
2021年 | 173篇 |
2020年 | 123篇 |
2019年 | 125篇 |
2018年 | 175篇 |
2017年 | 157篇 |
2016年 | 192篇 |
2015年 | 160篇 |
2014年 | 223篇 |
2013年 | 406篇 |
2012年 | 366篇 |
2011年 | 428篇 |
2010年 | 325篇 |
2009年 | 369篇 |
2008年 | 353篇 |
2007年 | 367篇 |
2006年 | 262篇 |
2005年 | 253篇 |
2004年 | 204篇 |
2003年 | 183篇 |
2002年 | 157篇 |
2001年 | 105篇 |
2000年 | 111篇 |
1999年 | 107篇 |
1998年 | 103篇 |
1997年 | 111篇 |
1996年 | 80篇 |
1995年 | 100篇 |
1994年 | 87篇 |
1993年 | 63篇 |
1992年 | 64篇 |
1991年 | 31篇 |
1990年 | 46篇 |
1989年 | 65篇 |
1988年 | 49篇 |
1987年 | 37篇 |
1986年 | 51篇 |
1985年 | 57篇 |
1984年 | 44篇 |
1983年 | 54篇 |
1982年 | 35篇 |
1981年 | 35篇 |
1980年 | 32篇 |
1979年 | 26篇 |
1978年 | 19篇 |
1977年 | 17篇 |
1976年 | 24篇 |
1975年 | 29篇 |
1974年 | 22篇 |
排序方式: 共有6838条查询结果,搜索用时 9 毫秒
61.
A semitheoretical correlation based on an extension of the random length, random angle statistical model of Davidson (1959) is developed which predicts liquid film mass transfer coefficients in a column packed with partially wetted Raschig rings. The method takes into account the ring size and the mixing which occurs at the packing junctions and allows an estimation of the effective length of a packing piece for a particular liquid viscosity. Predicted values of mass transfer coefficients are in good agreement with the experimental values obtained for the carbon dioxide-water and carbon dioxide-aqueous glycerol systems at 25°C reported by Mangers and Ponter (1980b) and other systems reported by Sherwood and Holloway (1940). 相似文献
62.
PVC profile extrusion compounds have a unique morphology. While other polymers gradually decrease in extrusion die swell with increasing length/thickness (L/D) ratio, PVC profile extrusion compounds have a low die swell, quite independent of the die's L/D ratio in the range of 5 to 20. The fact that the die land length can be changed without changing the extrudate swell is an important consideration, which makes die design and balancing dies simpler and easier for PVC profile extrusion compounds. While other polymers substantially increase extrudate swell with increased shear rate, the swell of the PVC profile compounds is not much affected by shear or extrusion rate. This unique behavior allows wider processing latitude in profile extrusion and faster extrusion rates than with other polymers. Another unique factor in the rheology of PVC profile extrusion compounds is that extrusion die swell increases with increasing melt temperature, while other polymers have decreasing die swell with increasing melt temperature. The unusual rheology of PVC profile extrusion compounds is attributed to its unique melt morphology, where the melt flow units are 1 um bundles and molecules that have low surface to surface interaction and entanglement at low processing temperatures but increased melting and increased entanglement at higher processing temperatures. Other polymers, unlike PVC, have melt flow at the molecular level. 相似文献
63.
The purpose of this work was to examine the possible significance in the formation of metallurgical coke of the anisotropic spherical mesophase exemplified by that found during the carbonization of pitch-like materials, and to ascertain if the various types of optical anisotropy found in coke could form a basis for the characterization of cokes produced from different coals. Vitrains from a wide range of coals were carbonized at temperatures from 370 to 1000 °C and the types and amounts of optical anisotropy in the resulting semi-cokes and cokes were determined from microscopic examination, the anisotropic components being classified according to grain size of the granular mosaics and appearance. The anisotropy developed directly from the isotropic phase, appearing initially as a fine-grained mosaic. With increasing carbonization temperature, this fine-grained mosaic was transformed into progressively coarser-grained anisotropy, the extent of this transformation depending on the rank of the vitrain. It is therefore concluded that the formation, growth and coalescence of anisotropic spherical bodies, such as occurs during the carbonization of pitch, is not a necessary precursor of the mosaic anisotropy in coke. The type and amount of anisotropy developed provide a quantitative means of characterising different cokes. 相似文献
64.
65.
PU YiFei SIARRY Patrick ZHOU JiLiu LIU YiGuang ZHANG Ni HUANG Guo LIU YiZhi 《中国科学:信息科学(英文版)》2014,(7):180-198
In this paper,a set of fractional partial differential equations based on fractional total variation and fractional steepest descent approach are proposed to address the problem of traditional drawbacks of PM and ROF multi-scale denoising for texture image.By extending Green,Gauss,Stokes and Euler-Lagrange formulas to fractional field,we can find that the integer formulas are just their special case of fractional ones.In order to improve the denoising capability,we proposed 4 fractional partial differential equation based multiscale denoising models,and then discussed their stabilities and convergence rate.Theoretic deduction and experimental evaluation demonstrate the stability and astringency of fractional steepest descent approach,and fractional nonlinearly multi-scale denoising capability and best value of parameters are discussed also.The experiments results prove that the ability for preserving high-frequency edge and complex texture information of the proposed denoising models are obviously superior to traditional integral based algorithms,especially for texture detail rich images. 相似文献
66.
Zhang Yingqian Lombardi Michele De Causmaecker Patrick 《Annals of Mathematics and Artificial Intelligence》2021,89(7):615-616
Annals of Mathematics and Artificial Intelligence - 相似文献
67.
Renaud Merlet Louis Winnubst Arian Nijmeijer Mohammad Amirilargani Ernst J. R. Sudhölter Louis C. P. M. de Smet Sara Salvador Cob Pieter Vandezande Matthieu Dorbec Soraya Sluijter Henk van Veen Yvonne VanDelft Ingrid Wienk Petrus Cuperus Subhalaxmi Behera Yusak Hartanto Ivo F. J. Vankelecom Patrick de Wit 《化学,工程师,技术》2021,93(9):1389-1395
Organic solvent nanofiltration (OSN) is gradually expanding from academic research to industrial implementation. The need for membranes with low and sharp molecular weight cutoffs that are able to operate under aggressive OSN conditions is increasing. However, the lack of comparable and uniform performance data frustrates the screening and membrane selection for processes. Here, a collaboration is presented between several academic and industrial partners analyzing the separation performance of 10 different membranes using three model process mixtures. Membrane materials range from classic polymeric and thin film composites (TFCs) to hybrid ceramic types. The model solutions were chosen to mimic cases relevant to today's industrial use: relatively low molar mass solutes (330–550 Da) in n-heptane, toluene, and anisole. 相似文献
68.
Patrick Pimenta R. Cruz Leonardo Cerqueira da Silva Raildo A. Fiuza-Jr Humberto Polli 《应用聚合物科学杂志》2021,138(25):50598
Thermal degradation of PVC occurs in two stages, with each stage subdivided into two substages. The first refers to the dehydrochlorination, where hydrochloric acid is formed, and giving polyene structures. Hitherto, the degradation mechanism and action of hydrochloric acid as a catalyst during the dehydrochlorination stage are poorly known. Recently, the importance of the tacticity has gained attention for its influence on the dehydrochlorination mechanism. The present work focused on the dehydrochlorination stage, studying the molecular structure by FTIR analysis and the kinetic parameters by TGA analysis in Nitrogen atmosphere, based on three mathematical methods: Friedman, Kissinger, and Flynn-Wall-Ozawa. The sample was a pure homopolymer obtained by suspension polymerization. The dehydrochlorination kinetics follows a first order reaction model and occurs by nucleation and growth. The dehydrochlorination begins with the loss of very labile chlorine atoms present in defective and isotactic molecular segments. The formed HCl acts as a catalyst in the degradation. Following 40% conversion, a drop in Ea is observed. After that, chlorine atoms present in syndiotactic and atactic sequences, are released and, added to the large number of polyene chain sequences, and an increase in Ea is observed up to 60% conversion, where the dehydrochlorination stage is concluded. 相似文献
69.
Vladimir Brailovski Patrick Terriault Sergei Prokoshkin 《Journal of Materials Engineering and Performance》2002,11(6):614-621
Shape memory alloys (SMA) suffer from the same impairing mechanisms experienced during cycling loading by classic alloys.
Moreover, SMA fatigue behavior is greatly influenced by thermomechanical cycling through the zone of thermoelastic phase transformation,
which is the basis of shape memory and superelasticity effects. Since the fatigue resistance of any material can be improved
by an appropriate thermomechanical treatment, in the present work combined differential scanning calorimetry and microhardness
testing were used to determine an optimum annealing temperature for the cold-worked Ni-50.1%Ti alloy. The optimization is
based on the assumption that latent heat of transformation is proportional to the mechanical work generated by SMA upon heating,
while material hardness is related to the yield stress of the material. It is supposed that an optimum trade-off in these
two properties guarantees the best dimensional and functional stability of SMA devices. The level and stability of the mechanical
work generated by the material during low-cycle fatigue testing are considered criteria for the material performance and thus
of the validity of the proposed optimization procedure. 相似文献
70.
Jörg Becker Patrick Delfmann Hanns-Alexander Dietrich Matthias Steinhorst Mathias Eggert 《Information Systems Frontiers》2016,18(2):359-405
Given the strong increase in regulatory requirements for business processes the management of business process compliance becomes a more and more regarded field in IS research. Several methods have been developed to support compliance checking of conceptual models. However, their focus on distinct modeling languages and mostly linear (i.e., predecessor-successor related) compliance rules may hinder widespread adoption and application in practice. Furthermore, hardly any of them has been evaluated in a real-world setting. We address this issue by applying a generic pattern matching approach for conceptual models to business process compliance checking in the financial sector. It consists of a model query language, a search algorithm and a corresponding modelling tool prototype. It is (1) applicable for all graph-based conceptual modeling languages and (2) for different kinds of compliance rules. Furthermore, based on an applicability check, we (3) evaluate the approach in a financial industry project setting against its relevance for decision support of audit and compliance management tasks. 相似文献