全文获取类型
收费全文 | 214171篇 |
免费 | 3319篇 |
国内免费 | 624篇 |
专业分类
电工技术 | 3563篇 |
综合类 | 162篇 |
化学工业 | 34465篇 |
金属工艺 | 8211篇 |
机械仪表 | 6427篇 |
建筑科学 | 5339篇 |
矿业工程 | 1325篇 |
能源动力 | 5510篇 |
轻工业 | 20513篇 |
水利工程 | 2419篇 |
石油天然气 | 4109篇 |
武器工业 | 8篇 |
无线电 | 23679篇 |
一般工业技术 | 41994篇 |
冶金工业 | 37959篇 |
原子能技术 | 5137篇 |
自动化技术 | 17294篇 |
出版年
2022年 | 1879篇 |
2021年 | 2682篇 |
2020年 | 1624篇 |
2019年 | 2017篇 |
2018年 | 3107篇 |
2017年 | 3203篇 |
2016年 | 3382篇 |
2015年 | 2286篇 |
2014年 | 3723篇 |
2013年 | 9930篇 |
2012年 | 5997篇 |
2011年 | 8071篇 |
2010年 | 6402篇 |
2009年 | 7089篇 |
2008年 | 7157篇 |
2007年 | 7163篇 |
2006年 | 6091篇 |
2005年 | 5604篇 |
2004年 | 5330篇 |
2003年 | 5191篇 |
2002年 | 4802篇 |
2001年 | 4829篇 |
2000年 | 4702篇 |
1999年 | 4871篇 |
1998年 | 11528篇 |
1997年 | 8277篇 |
1996年 | 6532篇 |
1995年 | 4771篇 |
1994年 | 4347篇 |
1993年 | 4158篇 |
1992年 | 3297篇 |
1991年 | 3130篇 |
1990年 | 2925篇 |
1989年 | 2997篇 |
1988年 | 2869篇 |
1987年 | 2434篇 |
1986年 | 2358篇 |
1985年 | 2760篇 |
1984年 | 2533篇 |
1983年 | 2373篇 |
1982年 | 2110篇 |
1981年 | 2233篇 |
1980年 | 2059篇 |
1979年 | 2149篇 |
1978年 | 2148篇 |
1977年 | 2387篇 |
1976年 | 3199篇 |
1975年 | 1846篇 |
1974年 | 1765篇 |
1973年 | 1781篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
Y. Rey-Tauriac J. Badoc B. Reynard R.A. Bianchi D. Lachenal A. Bravaix 《Microelectronics Reliability》2005,45(9-11):1349
This paper presents results of reliability investigation of 20 V N-Drift MOS transistor in 0.13 μm CMOS technology. Due to high performances required for CMOS applications, adding high voltage devices becomes a big challenge to guarantee the reliability criteria. In this context, new reliability approaches are needed. Safe Operating Area are defined for switch, Vds limited and Vgs limited applications in order to improve circuit designs. For Vds limited applications, deep doping dose effects in drift area are investigated in correlation to lifetime evaluations based on device parameter shifts under hot carrier stressing. To further determine the amount and locations of hot carriers injections, accurate 2D technological and electrical simulations are performed and permit to select the best compromise between performance and reliability for N-Drift MOS transistor. 相似文献
122.
123.
This paper is devoted to presenting controllability and stabilizability issues associated to a class of nonsmooth dynamical systems, namely complementarity dynamical systems. The main existing results are summarized, and some possible research directions are provided. Convex analysis and complementarity problems are claimed to be the main analysis tools for control related studies. This paper mainly focuses on mechanical applications. 相似文献
124.
The quantities of olefins, polyaromatic hydrocarbons and char formed during thermal decomposition in closed systems of alkylbenzenes are substantially reduced if the decomposition takes place in the presence of a good acceptor molecule such as pyrene or adamantane. The chemistry seems to be applicable to the upgrading of whole crude oils by a thermal treatment at 425-450°C in a closed system for 20-25 minutes. 相似文献
125.
The Metaflow architecture, a unified approach to maximizing the performance of superscalar microprocessors, is introduced. The Metaflow architecture exploits inherent instruction-level parallelism in conventional sequential programs by hardware means, without relying on optimizing compilers. It is based on a unified structure, the DRIS (deferred-scheduling, register-renaming instruction shelf), that manages out-of-order execution and most of the attendant problems. Coupling the DRIS with a speculative-execution mechanism that avoids conditional branch stalls results in performance limited only be inherent instruction-level parallelism and available execution resources. Although presented in the context of superscalar machines, the technique is equally applicable to a superpipelined implementation. Lightning, the first implementation of the Metaflow architecture, which executes the Sparc RISC instruction set is described 相似文献
126.
P. C. Campbell E. B. Hawbolt J. K. Brimacombe 《Metallurgical and Materials Transactions A》1991,22(11):2769-2778
The goal of this study was to develop a mathematical model which incorporates heat flow, phase transformation kinetics, and
property-structure-composition relationships to predict the mechanical properties of steel rod being control cooled under
industrial conditions. Thus, the principles of microstructural engineering have been brought to bear on this interdisciplinary
problem by combining computer modeling with laboratory measurements of heat flow, austenite decomposition kinetics, microstructure
and mechanical properties, and industrial trials to determine heat transfer and obtain rod samples under known conditions.
Owing to the length and diversity of the study, it is reported in three parts,[8191]the first of which is concerned with the heat flow measurements. A relatively simple and reliable technique, involving a preheated
steel rod instrumented with a thermocouple secured at its centerline, has been devised to determine the cooling rate in different
regions of the moving bed of rod loops on an operating Stelmor line. The measured thermal response of the rod has been analyzed
by two transient conduction models (lumped and distributed parameter, respectively) to yield overall heat-transfer coefficients
for radiation and convection. The adequacy of the technique has been checked by cooling instrumented rods under well-defined,
air crossflow conditions in the laboratory and comparing measured heat-transfer coefficients to values predicted from well-established
equations. The industrial thermal measurements have permitted the characterization of a coefficient to account for radiative
interaction among adjacent rod loops near the edge and at the center of the bed.
Formerly Graduate Student, The University of British Columbia. 相似文献
127.
128.
Nucleation of solidification in liquid droplets 总被引:2,自引:0,他引:2
Analytical and numerical methods have been developed to analyze the solidification kinetics of a mass of liquid droplets dispersed
in a fluid or solid matrix using classical nucleation theory. The resulting analytical expressions and numerical calculations
can be compared directly with calorimetric measurements of the droplet solidification exotherms to obtain information about
the nucleation mechanism. With increasing contact angle at the solid-liquid-matrix triple point, the solidification onset,
peak, and end temperatures and exothermic peak height all decrease sharply and the droplet solidification exotherms become
broader. Decreasing either the droplet radius or the number of potential catalytic nucleation sites produces a similar but
smaller effect. Distributions in droplet radius, contact angle, and nucleation sites have no effect on the solidification
peak temperature, but the droplet solidification exotherms become broader and more symmetric. The solidification onset temperature
is independent of cooling rate in the calorimeter, but the solidification peak and end temperatures decrease and the exothermic
peak height increases with increasing cooling rate. Predicted droplet solidification exotherms are in excellent agreement
with detailed experimental measurements on 10-nm-radius Cd droplets embedded in a solid Al matrix. Analytical predictions
give best-fit values of 43 deg and 430 for the contact angle and the number of potential catalytic nucleation sites per droplet,
respectively; numerical predictions give best-fit values of 43 deg and 750 for the contact angle and the number of potential
catalytic nucleation sites per droplet, respectively. 相似文献
129.
130.