全文获取类型
收费全文 | 282670篇 |
免费 | 23058篇 |
国内免费 | 12167篇 |
专业分类
电工技术 | 16077篇 |
技术理论 | 25篇 |
综合类 | 19756篇 |
化学工业 | 47321篇 |
金属工艺 | 15975篇 |
机械仪表 | 17571篇 |
建筑科学 | 21835篇 |
矿业工程 | 8894篇 |
能源动力 | 7638篇 |
轻工业 | 20625篇 |
水利工程 | 4803篇 |
石油天然气 | 18485篇 |
武器工业 | 2201篇 |
无线电 | 30929篇 |
一般工业技术 | 32455篇 |
冶金工业 | 14775篇 |
原子能技术 | 2774篇 |
自动化技术 | 35756篇 |
出版年
2024年 | 1266篇 |
2023年 | 4635篇 |
2022年 | 8275篇 |
2021年 | 11326篇 |
2020年 | 8844篇 |
2019年 | 7398篇 |
2018年 | 8150篇 |
2017年 | 9174篇 |
2016年 | 8303篇 |
2015年 | 11063篇 |
2014年 | 14273篇 |
2013年 | 16697篇 |
2012年 | 18157篇 |
2011年 | 19847篇 |
2010年 | 17545篇 |
2009年 | 16610篇 |
2008年 | 16358篇 |
2007年 | 15555篇 |
2006年 | 15786篇 |
2005年 | 13519篇 |
2004年 | 9242篇 |
2003年 | 7818篇 |
2002年 | 7101篇 |
2001年 | 6272篇 |
2000年 | 6475篇 |
1999年 | 7149篇 |
1998年 | 5892篇 |
1997年 | 4780篇 |
1996年 | 4517篇 |
1995年 | 3765篇 |
1994年 | 2995篇 |
1993年 | 2097篇 |
1992年 | 1634篇 |
1991年 | 1306篇 |
1990年 | 992篇 |
1989年 | 797篇 |
1988年 | 591篇 |
1987年 | 366篇 |
1986年 | 300篇 |
1985年 | 213篇 |
1984年 | 150篇 |
1983年 | 123篇 |
1982年 | 131篇 |
1981年 | 100篇 |
1980年 | 87篇 |
1979年 | 45篇 |
1978年 | 27篇 |
1977年 | 20篇 |
1976年 | 39篇 |
1973年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
961.
研究了55SiMnVB弹簧钢板疲劳断口特征及裂扩展过程。结果表明,喷丸强化在表层产生的残余压应力可明显提高疲劳抗力,增强裂纹闭合效应,降低裂纹扩展速度。 相似文献
962.
We reviewed the clinical features of 44 patients with invasive group A streptococcal (GAS) disease who were treated at two teaching hospitals in southern Taiwan from 1991 to 1994. Genes encoding streptococcal pyrogenic exotoxin types A (speA), B (speB), C (speC), and F (speF) and serotypes of M1, M6, and M12 were determined by polymerase chain reaction to target specific sequences in the 44 isolates recovered from these patients and in 28 isolates recovered from upper respiratory sites in 28 additional patients during the study period. The protease activity of these isolates was tested by using the casein plate method. Of the 44 patients with invasive diseases, 25 (57%) had no obvious underlying diseases, and 14 (32%) had preexisting neoplastic diseases or had previously used steroids. Twenty-five patients (57%) presented with cellulitis or necrotizing fasciitis, 24 (55%) had bacteremia, and eight (18%) had streptococcal toxic shock syndrome (STSS). Eight patients (18%) died of invasive GAS disease; seven had STSS, and seven had underlying diseases. All eight patients died within 48 hours after hospitalization. The presence of speA, speC, or speF was not implicated in any particular clinical syndrome in patients with invasive GAS disease. High-level protease activity and the M1 serotype of the isolates were significantly associated with the clinical signs of STSS and with mortality. M1 serotype and protease activity, as well as host immune status, might play significant roles in the pathogenesis of invasive GAS disease in Taiwan. 相似文献
963.
ST-4型全自动辊道双推板窑是为永磁铁氧体规模生产而研制的一种节能型空气烧结窑。它根据永磁铁氧体烧结的工艺要求,设计了合理的温区,使规模生产烧结成品率达95%以上;采用辊道推板相结合的窑床形式与复合保温结构,达到了永磁铁氧体能耗1.2kwh/kg;采用优化设计,使设备性能先进,稳定可靠。 相似文献
964.
Mei Xuan Xu Wen Guang Liu Yun Lin Guan Zuo Peng Bi Kang De Yao 《Polymer International》1995,38(2):205-209
The phase behavior of a hybrid polymer network (HPN) composed of poly[(propylene glycol maleate)-co-(propylene glycol phthalate)] crosslinked with styrene and polyester–urethane crosslinked with methylene-bis-ortho-chloroaniline was examined. The correlation between phase separation and impact strength of the HPNs is discussed. The composition of HPNs has an effect on their properties. 相似文献
965.
金刚石光电导探测器研制及在软X光测量中的初步应用 总被引:1,自引:0,他引:1
介绍了我们自己设计制造的天然Ⅱa型金刚石光导探测器的结构,原理,制造工艺,实验标定及其在ICF实验中软X光测量中的应用等。 相似文献
966.
967.
偶联剂对玻璃纤维/环氧基复合材料界面介电性能的影响研究 总被引:6,自引:3,他引:3
本文研究了五种偶联剂对玻璃纤维浸润性能和玻璃纤维/环氧基复合材料界面介电性能的影响。结果表明,玻璃纤维经偶联剂处理后,其浸润活化能降低,与环氧树脂基体间的相容性及化学反应活性得到改善;因此赋予了玻璃纤维与环氧基体间以良好的界面粘结性能,从而提高了玻璃纤维/环氧基复合材料界面的介电性能。其提高的幅度大小与偶联剂的极性及化学结构有关。 相似文献
968.
969.
Yu Long Author Vitae Kefei Chen Author Vitae Shengli Liu Author Vitae 《Computers & Electrical Engineering》2007,33(3):166-176
This paper proposes an identity-based threshold decryption scheme IB-ThDec and reduces its security to the Bilinear Diffie-Hellman problem. Compared with previous work, this conceals two pairing computations in the ciphertext validity verification procedure. The formal proof of security of this scheme is provided in the random oracle model. Additionally, we show that IB-ThDec can be applied to the threshold key escrow and the mediated cryptosystems. 相似文献
970.
Gradient Boundary Detection for Time Series Snapshot Construction in Sensor Networks 总被引:1,自引:0,他引:1
Jie Lian Lei Chen Naik K. Yunhao Liu Agnew G.B. 《Parallel and Distributed Systems, IEEE Transactions on》2007,18(10):1462-1475
In many applications of sensor networks, the sink needs to keep track of the history of sensed data of a monitored region for scientific analysis or supporting historical queries. We call these historical data a time series of value distributions or snapshots. Obviously, to build the time series snapshots by requiring all of the sensors to transmit their data to the sink periodically is not energy efficient. In this paper, we introduce the idea of gradient boundary and propose the gradient boundary detection (GBD) algorithm to construct these time series snapshots of a monitored region. In GBD, a monitored region is partitioned into a set of subregions and all sensed data in one subregion are within a predefined value range, namely, the gradient interval. Sensors located on the boundaries of the subregions are required to transmit the data to the sink and, then, the sink recovers all subregions to construct snapshots of the monitored area. In this process, only the boundary sensors transmit their data and, therefore, energy consumption is greatly reduced. The simulation results show that GBD is able to build snapshots with a comparable accuracy and has up to 40 percent energy savings compared with the existing approaches for large gradient intervals. 相似文献