全文获取类型
收费全文 | 145738篇 |
免费 | 17477篇 |
国内免费 | 9484篇 |
专业分类
电工技术 | 16984篇 |
技术理论 | 4篇 |
综合类 | 16342篇 |
化学工业 | 13600篇 |
金属工艺 | 9827篇 |
机械仪表 | 14389篇 |
建筑科学 | 9259篇 |
矿业工程 | 7069篇 |
能源动力 | 7630篇 |
轻工业 | 2996篇 |
水利工程 | 4946篇 |
石油天然气 | 7182篇 |
武器工业 | 4154篇 |
无线电 | 17713篇 |
一般工业技术 | 13841篇 |
冶金工业 | 5059篇 |
原子能技术 | 1997篇 |
自动化技术 | 19707篇 |
出版年
2024年 | 752篇 |
2023年 | 2194篇 |
2022年 | 4185篇 |
2021年 | 4644篇 |
2020年 | 5040篇 |
2019年 | 3889篇 |
2018年 | 3877篇 |
2017年 | 5046篇 |
2016年 | 6033篇 |
2015年 | 6542篇 |
2014年 | 9704篇 |
2013年 | 9433篇 |
2012年 | 11566篇 |
2011年 | 12624篇 |
2010年 | 9289篇 |
2009年 | 9177篇 |
2008年 | 8710篇 |
2007年 | 10729篇 |
2006年 | 9192篇 |
2005年 | 7397篇 |
2004年 | 6160篇 |
2003年 | 5053篇 |
2002年 | 4055篇 |
2001年 | 3424篇 |
2000年 | 2720篇 |
1999年 | 2256篇 |
1998年 | 1725篇 |
1997年 | 1382篇 |
1996年 | 1224篇 |
1995年 | 997篇 |
1994年 | 823篇 |
1993年 | 566篇 |
1992年 | 449篇 |
1991年 | 391篇 |
1990年 | 289篇 |
1989年 | 262篇 |
1988年 | 182篇 |
1987年 | 116篇 |
1986年 | 98篇 |
1985年 | 58篇 |
1984年 | 71篇 |
1983年 | 42篇 |
1982年 | 38篇 |
1981年 | 23篇 |
1980年 | 27篇 |
1979年 | 29篇 |
1963年 | 12篇 |
1959年 | 35篇 |
1955年 | 18篇 |
1951年 | 35篇 |
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
31.
1 Introduction A double-walled invertube is difficult to fabricate other than applying inversion process. Such kind of invertube can be used as impact energy absorbing element in transport vehicles, like aircrafts and automobiles. Reddy T Y[1] did the analysis of Internal inversion and calculated the inversion load. Reid[2] et al. examined nosing and internal inversion of cold drawn steel tube by the finite element package ABAQUS. Recently, Rosa P A[3] et al. investigated Internal invers… 相似文献
32.
Repetitive processes are a distinct class of 2D systems (i.e. information propagation in two independent directions) of both systems theoretic and applications interest. They cannot be controlled by direct extension of existing techniques from either standard (termed 1D here) or 2D systems theory. In this paper, we exploit their unique physical structure to show how two term, i.e. proportional plus integral (or PI) action, can be used to control these processes to produce desired behavior (as opposed to just stability). 相似文献
33.
R. Tao 《Chemical engineering science》2006,61(7):2186-2190
Molecular dynamical simulation has been carried out to investigate the structure and dynamics of a dipolar fluid under strong shear. Dipolar fluid consists of polarizable particles, which have an induced dipole moment in the applied field direction. Shear stress is perpendicular to the field direction. When shear stress is small, the flow has a flowing-chain structure. If shear stress increases to pass a critical value, flowing-chain structure changes to flowing layer structure. Each layer is parallel to the flow direction and shear direction. Within one layer, particles form strings in the flow direction. 相似文献
34.
35.
M. J. O'sullivan 《国际能源研究杂志》1985,9(3):319-332
This paper is intended to be a state of the art review of geothermal reservoir simulation. Its recent application to the modelling of real geothermal reservoirs is described and put in the context of an emerging general approach to reservoir modelling. The use of computer simulation for geothermal well test analysis is described. One of the main recent uses of reservoir simulators has been for conducting numerical experiments aimed at improving the understanding of geothermal reservoir physics. Such studies on fractured reservoirs, the thermal structure of reservoirs and the effects of non-condensable gases and dissolved salts are outlined. 相似文献
36.
《Drying Technology》2007,25(6):971-983
This article reviews developments in the simulations of spray dryer behavior, including the challenges in modeling the complex flow patterns inside the equipment, which are often highly transient and three-dimensional in nature. There appears to be considerable scope for using CFD simulations for investigating methods to reduce the rates of wall deposition and of thermal degradation for particles by modifying the air flow patterns in the chamber through small changes in the air inlet geometry. Challenges include building particle drying kinetics and reaction processes, as well as agglomeration behavior, into these simulations. The numerical simulations should be valuable supplements to pilot-scale testing, enabling more extensive and accurate optimization to be carried out than hitherto possible. New understanding of reaction processes and materials science, in combination with recent knowledge of the application of CFD to these problems, may enable new engineered powder products to be developed from the one-step spray-drying process. 相似文献
37.
The mirror effect for word frequency refers to the finding that low-frequency words have higher hit rates and lower false alarm rates than high-frequency words. This result is typically interpreted in terms of conventional signal detection theory (SDT), in which case it indicates that the order of the underlying old item distributions mirrors the order of the new item distributions. However, when viewed in terms of a mixture version of SDT, the order of hits and false alarms does not necessarily imply the same order in the underlying distributions because of possible effects of mixing. A reversal in underlying distributions did not appear for fits of mixture SDT models to data from 4 experiments. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
38.
In this study, distribution and history of residual stresses in plaque-like geometries are simulated based on linear thermoviscoelastic
model, which helps to understand the mechanics and evolution of the residual stresses in the injection molding process. The
numerical calculation of direction, combined with the specified boundary conditions. Results show that the stress variation
across the thickness exhibits a high surface tensile value changing to a compressive peak value close to the surface, with
the core region experiencing a parabolic tensile peak. Residual stress distribution throughout the thickness is almost same
along the flowpath and the final residual stresses value near the gate is lower than the value near the end of flowpath. 相似文献
39.
多媒体业务对无线通信的带宽与品质提出了更高的要求,OFDM和MIMO由于满足了这一需求被越来越多的无线通信标准采用所为底层的调制和传输技术。频率同步问题是OFDM—MIMO物理层设计中正确解调的前提和基础,本文介绍了OFDM—MIMO的原理、特点和频率同步问题的研究现状。 相似文献
40.
薄板坯连铸连轧工艺对铌微合金化高强度钢组织和性能的影响 总被引:1,自引:0,他引:1
首先建立薄板坯连铸连轧工艺的试验室模拟技术,并运用该模拟技术,研究薄板坯连铸连轧工艺(CSP)和传统板坯再加热工艺(TRP)两种工艺对铌微合金化高强度钢的显微组织和力学性能的影响。研究结果表明:CSP钢的晶粒细化效果不如TRP钢,两者的平均铁素体晶粒尺寸分别为8.17μm和6.30μm。在CSP试验钢板中铌的析出量较大,特别是在铁素体中细小颗粒的铌的析出物较多,沉淀强化效果较强。CSP试验钢的σ0.5和σb分别较TRP工艺低约40MPa和约25MPa,同时其低温冲击韧性较好,FATT温度较低。 相似文献