全文获取类型
收费全文 | 91463篇 |
免费 | 11466篇 |
国内免费 | 6428篇 |
专业分类
电工技术 | 10484篇 |
技术理论 | 2篇 |
综合类 | 9320篇 |
化学工业 | 8814篇 |
金属工艺 | 3027篇 |
机械仪表 | 7128篇 |
建筑科学 | 10806篇 |
矿业工程 | 3138篇 |
能源动力 | 4297篇 |
轻工业 | 6144篇 |
水利工程 | 3613篇 |
石油天然气 | 4614篇 |
武器工业 | 1061篇 |
无线电 | 6176篇 |
一般工业技术 | 7499篇 |
冶金工业 | 3042篇 |
原子能技术 | 460篇 |
自动化技术 | 19732篇 |
出版年
2024年 | 712篇 |
2023年 | 1879篇 |
2022年 | 3336篇 |
2021年 | 3590篇 |
2020年 | 3976篇 |
2019年 | 3389篇 |
2018年 | 3101篇 |
2017年 | 3739篇 |
2016年 | 4108篇 |
2015年 | 4519篇 |
2014年 | 6721篇 |
2013年 | 6332篇 |
2012年 | 7477篇 |
2011年 | 7638篇 |
2010年 | 5365篇 |
2009年 | 5647篇 |
2008年 | 5024篇 |
2007年 | 5830篇 |
2006年 | 4981篇 |
2005年 | 4006篇 |
2004年 | 3343篇 |
2003年 | 2643篇 |
2002年 | 2292篇 |
2001年 | 1874篇 |
2000年 | 1571篇 |
1999年 | 1132篇 |
1998年 | 1005篇 |
1997年 | 865篇 |
1996年 | 671篇 |
1995年 | 555篇 |
1994年 | 458篇 |
1993年 | 325篇 |
1992年 | 273篇 |
1991年 | 196篇 |
1990年 | 168篇 |
1989年 | 156篇 |
1988年 | 103篇 |
1987年 | 60篇 |
1986年 | 43篇 |
1985年 | 43篇 |
1984年 | 35篇 |
1983年 | 28篇 |
1982年 | 27篇 |
1981年 | 13篇 |
1980年 | 39篇 |
1979年 | 18篇 |
1978年 | 6篇 |
1977年 | 7篇 |
1959年 | 6篇 |
1951年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
The eye movements of young and older adults were tracked as they read sentences varying in syntactic complexity. In Experiment 1, cleft object and object relative clause sentences were more difficult to process than cleft subject and subject relative clause sentences; however, older adults made many more regressions, resulting in increased regression path fixation times and total fixation times, than young adults while processing cleft object and object relative clause sentences. In Experiment 2, older adults experienced more difficulty than young adults while reading cleft and relative clause sentences with temporary syntactic ambiguities created by deleting the that complementizers. Regression analyses indicated that readers with smaller working memories need more regressions and longer fixation times to process cleft object and object relative clause sentences. These results suggest that age-associated declines in working memory do affect syntactic processing. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
22.
Yi‐Hung Chen Ching‐Yuan Chang Wei‐Ling Su Chun‐Yu Chiu Yue‐Hwa Yu Pen‐Chi Chiang Chiung‐Fen Chang Je‐Lueng Shie Chyow‐San Chiou Sally IM Chiang 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2005,80(1):68-75
This study investigates the ozonation of CI Reactive Black 5 (RB5) by using the rotating packed bed (RPB) and completely stirred tank reactor (CSTR) as ozone contactors. The RPB, which provides high gravitational force by adjusting the rotational speed, was employed as a novel ozone contactor. The same ozone dosage was separately introduced into either the RPB or the CSTR for the investigation, while the experimental solution was continuously circulated within the apparatus consisting of the RPB and CSTR. The decolorization and mineralization efficiencies of RB5 in the course of ozonation are compared for these two methods. Moreover, the dissolved and off‐gas ozone concentrations were simultaneously monitored for the further analysis. As a result, the ozone mass transfer rate per unit volume of the RPB was significantly higher because of its higher mass transfer coefficient and gas–liquid concentration driving force. Furthermore, ozonation kinetics was found to be independent of the gravitational magnitude of an ozone gas–liquid contactor. Therefore, the results suggest employing RPBs as ozone‐contacting devices with the advantage of volume reduction. The experimental results, which can be used for further modeling of the ozonation process in the RPB, also show the requirement of correct design for the RPB. Consequently, the present study is useful for the understanding of practical application of RPBs. Copyright © 2004 Society of Chemical Industry 相似文献
23.
The anisotropic nature of fibre reinforced composites leads to large stress concentrations around pin-loaded holes through standard weave cloths. Proper understanding of how this anisotropic nature affects the load distribution around holes can be utilised to reduce these concentrations if sufficient thought is given to the internal fibre geometry near to the hole. Such local reinforcements need not be highly complex and can be readily produced without excessive effort, producing significant improvements in performance. 相似文献
24.
本文总结了近年冶金炉渣氮酸盐容量的研究方法,氮在炉渣中存在形态与炉渣氧分压的关系,炉渣氮化物容量与温度及炉渣成分的关系,并给出设计钢液脱氮渣系的基本原则。 相似文献
25.
The problem of determining the maximum mean response level crossing rate of a linear system driven by a partially specified Gaussian load process has been considered. The partial specification of the load is given only in terms of its total average energy. The critical input power spectral (PSD) function, which maximizes the mean response level crossing rate, is obtained. The critical input PSD turns out to be highly narrow-banded which fails to capture the erratic nature of the excitation. Consequently, the trade-off curve between the maximum mean response level crossing rate and the maximum disorder in the input process, quantified in terms of its entropy rate, has been generated. The method of Pareto optimization is used to tackle the conflicting objectives of the simultaneous maximization of the mean response level crossing rate and the input entropy rate. The non-linear multi-objective optimization has been carried out using a recently developed multi-criteria genetic algorithm scheme. Illustrative example of determining the critical input of an axially vibrating rod, excited by a partially specified stationary Gaussian load process, has been considered. 相似文献
26.
27.
Catherine Mongenet 《International journal of parallel programming》1997,25(6):497-524
This paper introduces results on placement and communications minimization for systems of affine recurrence equations. We show how to classify the dependences according to the number and nature of communications they may result in. We give both communication-free conditions and conditions for an efficient use of broadcast or neighbor-to-neighbor communication primitives. Since the dependences of a problem can generally not be all communication-free, we finally introduce a heuristic to globally minimize the communications based on the classification of dependences. 相似文献
28.
本文对采用S1和S2的混合物作为萃取剂的三聚甲醛萃取-精馏新工艺进行了模拟计算,得到了使总费用最低的三聚甲醛精制工艺的联合操作参数。模拟计算结果成功地指导了小试操作,并可为大型工程设计提供可靠的基础数据。 相似文献
29.
ADS Expert is an integrated system that (a) provides suggestions about suitable optimization algorithms for a particular structural optimization problem, (b) it offers explanations and guide lines, in the form of hypertext, that refer to the optimization strategy, optimizer and one dimensional search method, (c) it produces the required gradients for the objective function and the constraints using symbolic differentiation, (d) establishes a direct linking with ADS routines and (e) it monitors the evolution of the optimization process. The system can be used as an educational tool for structural optimization and as an efficient integrated system for small to medium size optimization problems for which the objective function and the constraints are given in the form of explicit functions of the design variables. The system is a Windows application and runs quite satisfactorily on PCs. 相似文献
30.