全文获取类型
收费全文 | 474045篇 |
免费 | 50600篇 |
国内免费 | 37627篇 |
专业分类
电工技术 | 34520篇 |
技术理论 | 37篇 |
综合类 | 40150篇 |
化学工业 | 81905篇 |
金属工艺 | 23177篇 |
机械仪表 | 27422篇 |
建筑科学 | 40341篇 |
矿业工程 | 16610篇 |
能源动力 | 15404篇 |
轻工业 | 33286篇 |
水利工程 | 13908篇 |
石油天然气 | 18249篇 |
武器工业 | 5722篇 |
无线电 | 52258篇 |
一般工业技术 | 48925篇 |
冶金工业 | 17838篇 |
原子能技术 | 5712篇 |
自动化技术 | 86808篇 |
出版年
2024年 | 1530篇 |
2023年 | 7025篇 |
2022年 | 11796篇 |
2021年 | 16824篇 |
2020年 | 15637篇 |
2019年 | 13230篇 |
2018年 | 12099篇 |
2017年 | 15655篇 |
2016年 | 18109篇 |
2015年 | 20231篇 |
2014年 | 28053篇 |
2013年 | 29465篇 |
2012年 | 34508篇 |
2011年 | 39573篇 |
2010年 | 29095篇 |
2009年 | 29783篇 |
2008年 | 29058篇 |
2007年 | 33663篇 |
2006年 | 30820篇 |
2005年 | 26707篇 |
2004年 | 22407篇 |
2003年 | 18826篇 |
2002年 | 15098篇 |
2001年 | 11625篇 |
2000年 | 9940篇 |
1999年 | 8050篇 |
1998年 | 6198篇 |
1997年 | 5145篇 |
1996年 | 4269篇 |
1995年 | 3480篇 |
1994年 | 3049篇 |
1993年 | 2252篇 |
1992年 | 1798篇 |
1991年 | 1349篇 |
1990年 | 1131篇 |
1989年 | 947篇 |
1988年 | 616篇 |
1987年 | 445篇 |
1986年 | 421篇 |
1985年 | 453篇 |
1984年 | 356篇 |
1983年 | 295篇 |
1982年 | 303篇 |
1981年 | 199篇 |
1980年 | 210篇 |
1979年 | 95篇 |
1978年 | 48篇 |
1977年 | 67篇 |
1976年 | 40篇 |
1959年 | 47篇 |
排序方式: 共有10000条查询结果,搜索用时 296 毫秒
991.
Human facial gestures often exhibit such natural stochastic variations as how often the eyes blink, how often the eyebrows and the nose twitch, and how the head moves while speaking. The stochastic movements of facial features are key ingredients for generating convincing facial expressions. Although such small variations have been simulated using noise functions in many graphics applications, modulating noise functions to match natural variations induced from the affective states and the personality of characters is difficult and not intuitive. We present a technique for generating subtle expressive facial gestures (facial expressions and head motion) semi‐automatically from motion capture data. Our approach is based on Markov random fields that are simulated in two levels. In the lower level, the coordinated movements of facial features are captured, parameterized, and transferred to synthetic faces using basis shapes. The upper level represents independent stochastic behavior of facial features. The experimental results show that our system generates expressive facial gestures synchronized with input speech. 相似文献
992.
CaCu3Ti4O12 electroceramic was prepared by a microwave assisted solid-state reaction technique from CaCO3, CuO and TiO2 powders. Processing involved the preparation of raw material, mixing and milling, calcination, pellet forming and sintering processes. Conventional furnace and microwave assisted sintering processes were employed in order to improve phase structures, morphology and dielectric properties of CaCu3Ti4O12 ceramics. Surface and fracture FESEM analysis showed that the microwave assisted sintered CaCu3Ti4O12 produced better densification and more uniform grain size compared to the conventional sintered sample. 相似文献
993.
R. Wongmaneerung W. Chaisan O. Khamman R. Yimnirun S. Ananta 《Ceramics International》2008,34(4):813-817
The potential of the vibro-milling technique as a simple method to obtain usable quantities of single-phase electroceramic powders with nanosized particles was examined. A detailed study considering the role of both milling time and firing condition on phase formation and particle size of the final product was performed. The calcination temperature for the formation of the desired phase was lower when longer milling times have been applied. More importantly, by employing an appropriate choice of the milling time and calcination condition, high purity electroceramic nanopowders have been successfully prepared with a simple solid-state reaction method. 相似文献
994.
Takayuki Honma Yuichiro Kuroki Tomoichiro Okamoto Masasuke Takata Yukihiro Kanechika Masanobu Azuma Hitofumi Taniguchi 《Ceramics International》2008,34(4):943-946
Aluminum nitride ceramics were prepared by sintering with 0–4.8 mass% of Ca3Al2O6 (C3A) as a sintering additive. The transmittance in the range of 260–550 nm increased with increasing amount of C3A. The cathodoluminescence intensity attributed to oxygen-induced defects decreased with increasing amount of C3A. From the results, the increase of the transmittance in the range of 260–550 nm was considered to be related to the decrease of the oxygen-induced defect density. 相似文献
995.
The stress intensity factors for a short crack partially penetrating an inclusion of arbitrary shape
Some approximate solutions for predicting the stress intensity factor of a short crack penetrating an inclusion of arbitrary
shape have been developed under mode I and mode II loading conditions. The derivation of the fundamental formula is based
on the transformation toughening theory. The transformation strains in the inclusion are induced by the crack-tip field and
remotely applied stresses, and approximately evaluated by the Eshelby equivalent inclusion theory. As validated by detailed
finite element (FE) analyses, the developed solutions have good accuracy for different inclusion shape and for a wide range
of modulus ratio between inclusion and matrix material. 相似文献
996.
基于MAPINFO和VB的自来水管网信息系统的建立 总被引:2,自引:0,他引:2
介绍基于MapInfo平台,利用VB语言进行二次开发,建立自来水管网地理信息系统的关键技术及其注意的问题。 相似文献
997.
999.
Hinshaw Stephen P.; Carte Estol T.; Fan Catherine; Jassy Jonathan S.; Owens Elizabeth B. 《Canadian Metallurgical Quarterly》2007,21(2):263
The current study prospectively followed girls with attention-deficit/hyperactivity disorder (ADHD), along with a matched comparison sample, 5 years after childhood neuropsychological assessments. Follow-up neuropsychological measures emphasized attentional skills, executive functions, and language abilities. Paralleling childhood findings, the childhood-diagnosed ADHD group displayed moderate to large deficits in executive/attentional performance as well as in rapid naming relative to the comparison group at follow up (Mage 14.2 years). ADHD-inattentive versus ADHD-combined contrasts were nonsignificant and of negligible effect size, even when a refined, sluggish cognitive tempo subgroup of the inattentive type was examined. Although ADHD versus comparison group differences largely withstood statistical control of baseline demographics and comorbidities, control of childhood IQ reduced executive function differences to nonsignificance. Yet when the subset of girls meeting diagnostic criteria for ADHD in adolescence was compared with the remainder of the participants, neuropsychological deficits emerged even with full statistical control. Overall, childhood ADHD in girls portends neuropsychological and executive deficits that persist for at least 5 years. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
1000.
MIMO (Multiple-Input Multiple-Output)的显著优点就是在不增加带宽的情况下,能够成倍地提高通信系统容量和频谱利用率,是未来移动通信与个人通信系统实现高速率数据传输,提高高传输质量的重要途径,也是未来移动通信系统广泛采用的关键技术.文中简要介绍了MIMO系统及其一种新的MIMO系统中的应用技术,即PARC(Per-antenna Rate Control)技术. 相似文献