全文获取类型
收费全文 | 347065篇 |
免费 | 5068篇 |
国内免费 | 890篇 |
专业分类
电工技术 | 6996篇 |
综合类 | 464篇 |
化学工业 | 49787篇 |
金属工艺 | 16989篇 |
机械仪表 | 14088篇 |
建筑科学 | 8288篇 |
矿业工程 | 1925篇 |
能源动力 | 7347篇 |
轻工业 | 26630篇 |
水利工程 | 3729篇 |
石油天然气 | 5208篇 |
武器工业 | 68篇 |
无线电 | 42236篇 |
一般工业技术 | 72993篇 |
冶金工业 | 52742篇 |
原子能技术 | 6509篇 |
自动化技术 | 37024篇 |
出版年
2021年 | 2437篇 |
2020年 | 1898篇 |
2019年 | 2353篇 |
2018年 | 11874篇 |
2017年 | 12532篇 |
2016年 | 8876篇 |
2015年 | 3430篇 |
2014年 | 4928篇 |
2013年 | 12875篇 |
2012年 | 9923篇 |
2011年 | 17832篇 |
2010年 | 15490篇 |
2009年 | 15155篇 |
2008年 | 15797篇 |
2007年 | 17636篇 |
2006年 | 8538篇 |
2005年 | 11077篇 |
2004年 | 9202篇 |
2003年 | 8708篇 |
2002年 | 7486篇 |
2001年 | 6896篇 |
2000年 | 6633篇 |
1999年 | 6525篇 |
1998年 | 14610篇 |
1997年 | 10560篇 |
1996年 | 8340篇 |
1995年 | 6635篇 |
1994年 | 5907篇 |
1993年 | 5765篇 |
1992年 | 4688篇 |
1991年 | 4340篇 |
1990年 | 4141篇 |
1989年 | 3864篇 |
1988年 | 3713篇 |
1987年 | 3264篇 |
1986年 | 3133篇 |
1985年 | 3754篇 |
1984年 | 3551篇 |
1983年 | 3134篇 |
1982年 | 2961篇 |
1981年 | 3083篇 |
1980年 | 2869篇 |
1979年 | 2731篇 |
1978年 | 2582篇 |
1977年 | 3022篇 |
1976年 | 3667篇 |
1975年 | 2404篇 |
1974年 | 2384篇 |
1973年 | 2381篇 |
1972年 | 1884篇 |
排序方式: 共有10000条查询结果,搜索用时 640 毫秒
211.
212.
In this study, feasibility of membrane separation for the removal of indigenous noroviruses (NVs) is evaluated. The indigenous NV gene was never detected from ultrafiltration (UF) permeates of sewage sludge and treated wastewater. Indigenous NV gene was also not detected from permeates of sewage sludge and treated wastewater by microfiltration (MF) with a pore size of 0.1 microm (MF0.1). Even though the pore size of MF (0.1 microm) was much larger than the diameter of virus particle (approximately 30-40nm), more than 4-log10 reduction value (LRV) at maximum was achieved by membrane separation with MF0.1. NV genes were often detected from permeates of sewage sludge and treated wastewater by MF with a pore size of 0.45 microm (MF0.45), although the maximum log10 reduction values were more than 3.59 for sewage sludge and more than 2.90 for treated wastewater. It is important to verify factors determining the removal efficiency of viruses with MF membranes. 相似文献
213.
A. Yu. Pustynnikov V. G. Ryabov D. T. Kalimullin A. N. Nechaev Ya. A. Treskov 《Chemistry and Technology of Fuels and Oils》2006,42(3):188-191
Paving-and roofing-grade asphalts were obtained at LUKOIL-Permnefteorgsintez Ltd. by mixing peroxidized asphalt and a number
of high-boiling unoxidized petroleum products in certain ratios. The asphalts obtained have improved performance characteristics:
high plasticity and low brittleness temperature.
__________
Translated from Khimiya i Tekhnologiya Topliv i Masel, No. 2, pp. 26–28, May–June, 2006. 相似文献
214.
The NW‐SE trending Cantarell structure in the Gulf of Campeche hosts the largest oilfield in Mexico. The oil occurs predominantly in latest Cretaceous – earliest Tertiary breccias with subsidiary reserves in Upper Jurassic (Oxfordian and Kimmeridgian) and Lower Cretaceous oolitic and partially dolomitized limestones, dolomites and shaly limestones. Cantarell has been interpreted both as a fold‐and‐thrust zone and as a dextral transpressional structure. Analysis of structure contours at 100m intervals, on the tops of the Tertiary breccia and the Kimmeridgian (Upper Jurassic) dolomite, indicates that the structure is an upright cylindrical fold with gently plunging conical terminations; there is also a conical portion in the central part of the structure. The axes of the central, NW and SE cones are subvertical. This geometry indicates that the two fold terminations and the central cone are aprons rather than points, with the NW and central cone axes intersecting the cylindrical fold axis at the point where the geometry switches from conical to cylindrical. The apical angle (i.e. the angle between the fold and cone axes) varies as follows: (i) in the NW cone, it is ~70° in the breccia and ~76° in the Kimmeridgian dolomite; (ii) in the central cone, it is ~77° in the breccia and ~73° in the Kimmeridgian dolomite; and (iii) in the SE cone, it is ~64° in the breccia and ~57° in the Kimmeridgian dolomite. This indicates that whereas the fold opens with depth in the NW cone, it tightens with depth in the central and SE cones. Assuming a parallel fold geometry, these apical angles indicate an increase in volume in the NW cone (i.e. larger hydrocarbon reservoirs), compared to the central and SE cones. Theoretical considerations indicate that the curvature increases dramatically towards the point of the cone. In the case of the Cantarell structure, the apices of the cones are located at the conical‐cylindrical fold junctions, where the highest curvature may have resulted in a higher degree of fracturing. The coincidence of maximum curvature and the intersection of the conical and cylindrical fold axes in the fold culminations with porous and permeable reservoir rocks may have made these locations favourable for the accumulation of hydrocarbons. 相似文献
215.
Co-browsing is an activity in which a group of users navigate their way through of a set of Web pages together for a shared
purpose. Effective co-browsing among users with different device capabilities requires a shared understanding of those Web
pages. This paper demonstrates the concept of shared viewpoints (SVPs), and personal viewpoints (PVPs), for co-browsing, before
detailing a framework for implementing these concepts. Finally, the effectiveness of the framework is presented through a
perceptual experiment. 相似文献
216.
217.
An adaptive numerical dissipation control in a class of high order filter methods for compressible MHD equations is systematically discussed. The filter schemes consist of a divergence-free preserving high order spatial base scheme with a filter approach which can be divergence-free preserving depending on the type of filter operator being used, the method of applying the filter step, and the type of flow problem to be considered. Some of these filter variants provide a natural and efficient way for the minimization of the divergence of the magnetic field (∇·B) numerical error in the sense that commonly used divergence cleaning is not required. Numerical experiments presented emphasize the performance of the ∇·B numerical error. Many levels of grid refinement and detailed comparison of the filter methods with several commonly used compressible MHD shock-capturing schemes will be illustratedA condensed version appears in the Proceedings of the International Conference on High Performance Scientific Computing, March 10-14, 2003, Hanoi, Vietnam. This is a revised version of a longer internal report, Feb. 19, 2004. The longer internal report was published as a RIACS Technical Report TR03.10, July 2003, NASA Ames Research Center 相似文献
218.
This paper considers the principles of deciphering basin-scale hydrocarbon migration patterns using the geochemical information which is present in trapped petroleum. Petroleum accumulations in subsiding basins can be thought of as "data archives" within which stored information can help us to understand aspects of hydrocarbon formation and migration. This information can impart a time-resolved picture of hydrocarbon migration in a basin in response to processes associated with progressive burial, particularly in the context of the occurrence and periodic activity of faults.
This review, which includes a series of tentative models of migration-related processes in the extensional Halten Terrace area, offshore mid-Norway, illustrates how we can use information from the migrating mobile hydrocarbon phase to improve our knowledge of the static geological system. Of particular importance is the role of sub-seismic heterogeneities and faults in controlling migration processes. We focus on how the secondary migration process can be enhanced in a multi-source rock basin such as the Halten Terrace, thereby increasing prospectivity. 相似文献
This review, which includes a series of tentative models of migration-related processes in the extensional Halten Terrace area, offshore mid-Norway, illustrates how we can use information from the migrating mobile hydrocarbon phase to improve our knowledge of the static geological system. Of particular importance is the role of sub-seismic heterogeneities and faults in controlling migration processes. We focus on how the secondary migration process can be enhanced in a multi-source rock basin such as the Halten Terrace, thereby increasing prospectivity. 相似文献
219.
Effendi Rusli Timothy O. Drews David L. Ma Richard C. Alkire Richard D. Braatz 《Journal of Process Control》2006,16(4):409-417
Robust nonlinear feedforward–feedback controllers are designed for a multiscale system that dynamically couples kinetic Monte Carlo (KMC) and finite difference (FD) simulation codes. The coupled codes simulate the copper electrodeposition process for manufacturing on-chip copper interconnects in electronic devices. The control objective is to regulate the current density subject to the condition that the steady-state fluctuation of the overpotential remains bounded within ±0.01 V. The controller designs incorporate a low-order stochastic model that captures the input–output behavior of the coupled KMC–FD code. The controllers achieve the objectives and the closed-loop responses implemented on the low-order model and the coupled KMC–FD code match well within stochastic variations. The nonlinear feedforward control reduces the rise time of the controller response while the feedback control ensures robustness in the presence of model uncertainty. 相似文献
220.
Presented here are details of the development of a novel membrane integrated circuit (IC) probe card structure based on microsystems technology. The device design allows probing of both solder bumps and pads. A self-limiting sensor was integrated to prolong device lifetime. Comparison with and discussion of the use of modelling is made. Possible enhancements to the probing structure are discussed to improve alignment and measurements. Also shown is data using our microsystems probe card to access a simple IC device. Our device has a contact resistance of less than 0.5 Ω for a force of 0.004 N. A method to implement our probing structure for commercial application and the potential developments which can be made to improve its ease of use are then discussed. 相似文献