全文获取类型
收费全文 | 87175篇 |
免费 | 10405篇 |
国内免费 | 7704篇 |
专业分类
电工技术 | 8127篇 |
综合类 | 9207篇 |
化学工业 | 10016篇 |
金属工艺 | 6178篇 |
机械仪表 | 6192篇 |
建筑科学 | 6648篇 |
矿业工程 | 3359篇 |
能源动力 | 2244篇 |
轻工业 | 9371篇 |
水利工程 | 3256篇 |
石油天然气 | 3321篇 |
武器工业 | 1211篇 |
无线电 | 9514篇 |
一般工业技术 | 7506篇 |
冶金工业 | 4602篇 |
原子能技术 | 1754篇 |
自动化技术 | 12778篇 |
出版年
2024年 | 555篇 |
2023年 | 1389篇 |
2022年 | 3421篇 |
2021年 | 4361篇 |
2020年 | 3099篇 |
2019年 | 2265篇 |
2018年 | 2356篇 |
2017年 | 2760篇 |
2016年 | 2416篇 |
2015年 | 3828篇 |
2014年 | 4701篇 |
2013年 | 5623篇 |
2012年 | 6991篇 |
2011年 | 7346篇 |
2010年 | 7238篇 |
2009年 | 6566篇 |
2008年 | 6993篇 |
2007年 | 6701篇 |
2006年 | 5761篇 |
2005年 | 4614篇 |
2004年 | 3438篇 |
2003年 | 2728篇 |
2002年 | 2948篇 |
2001年 | 2572篇 |
2000年 | 1716篇 |
1999年 | 718篇 |
1998年 | 483篇 |
1997年 | 291篇 |
1996年 | 216篇 |
1995年 | 169篇 |
1994年 | 125篇 |
1993年 | 141篇 |
1992年 | 81篇 |
1991年 | 58篇 |
1990年 | 83篇 |
1989年 | 95篇 |
1988年 | 32篇 |
1987年 | 37篇 |
1986年 | 33篇 |
1985年 | 24篇 |
1984年 | 10篇 |
1983年 | 13篇 |
1982年 | 16篇 |
1981年 | 23篇 |
1980年 | 35篇 |
1979年 | 20篇 |
1977年 | 46篇 |
1976年 | 89篇 |
1959年 | 15篇 |
1951年 | 18篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
舰船水声隐身技术(二) 总被引:2,自引:0,他引:2
本文探讨了水声隐身性能对舰船战技术性能的影响 ,舰船水噪声的主要噪声源、水噪声的治理措施及其展望。 相似文献
12.
发展和深化了集对分析(SPA)基础理论,并在此基础上探讨了基于集对分析的模式识别方法,给出了集对模式识别的三个判定原则,这对SPA的发展及其在模式识别中的应用提供了理论支持。 相似文献
13.
14.
J Lamoril C Andant C Bogard H Puy L Gouya JM Pawlotsky V Da Silva JC Soulé JC Deybach Y Nordmann 《Canadian Metallurgical Quarterly》1998,27(3):848-852
From 1995 to 1997, we prospectively evaluated the prevalence of hepatitis C virus (HCV) RNA in 124 patients with porphyria cutanea tarda (PCT) from Northern France (83 sporadic and 41 familial PCT). Serum samples were analyzed for ferritin, transaminases, HCV antibodies, and HCV RNA. In addition, genotyping of HCV and searches for HCV infection risk factors (blood transfusion, iv drug abuse, and surgical intervention) were performed. Twenty-six of 124 patients (21%; 95% CI: 13.9-28) were positive for serum HCV antibodies. All of them were also positive for HCV RNA. The prevalence of HCV infection was higher in the sporadic PCT group (26.5%, 22 out of 83) than in the familial PCT group (9.7%, 4 out of 41). Risk factors for hepatitis C infection were found to be significantly increased in the HCV-positive group when compared with the HCV-negative PCT group. In all HCV-positive patients with a risk factor, the suspected date of exposure to the virus always preceded the clinical onset of PCT. The HCV genotype pattern in PCT patients was similar to that observed in nonporphyric HCV patients in western European countries. Serum ferritin level was increased in both HCV-positive and HCV-negative porphyric patients. Transaminase levels were significantly higher in HCV-infected PCT patients. Sixty-seven out of 124 patients were retrospectively studied for hepatitis G virus (HGV) infection. Six of these 67 patients (8.9%; 95% CI: 2.1-15.8) were positive for HGV RNA. None of the six HGV-infected patients were positive for HCV RNA. The HGV-infected patients did not differ statistically from those without HGV infection with regard to age, ferritin, transaminase levels, and PCT treatment. These results support the view that sporadic cases of HGV infection may occur frequently. This study of a large cohort of HCV and PCT patients further documents an increasing gradient in HCV prevalence from northern to southern Europe, and shows that HCV infection acts as a triggering factor of PCT. Finally, the HGV prevalence found in the PCT patients was comparable with that found in French blood donors, suggesting that HGV is not a PCT triggering factor. 相似文献
15.
16.
Kyeongho Lee Yeshik Shin Sungjoon Kim Deog-Kyoon Jeong Kim G. Kim B. Da Costa V. 《Solid-State Circuits, IEEE Journal of》1998,33(5):816-823
In a high-resolution flat panel system, a conventional interface that directly connects a liquid crystal display (LCD) controller to a flat panel cannot overcome the problems of excess EMI (electromagnetic interference) and power caused by full-swing transmission signals in parallel lines. This paper presents a high-speed digital video interface system implemented with a low-cost standard CMOS (complimentary metal-oxide-semiconductor) technology that can mitigate EMI and power problems in high-resolution flat panel display systems. The combined architecture of the high-speed, small number of parallel lines and low-voltage swing serial interface can support resolutions from VGA (640×480 pixels) up to XGA (1024×768 pixels) with significant power improvement and drastic EMI reduction. To support high-speed, low-voltage swing signaling and overcome channel-to-channel skew problems, a robust data recovery system is required. The proposed digital phase-locked loop enables robust skew-insensitive data recovery of up to 1.04 GBd 相似文献
17.
The combination of the techniques of expert systems and neural networks has the potential of producing more powerful systems, for example, expert systems able to learn from experience. In this paper, we address the combinatorial neural model (CNM), a kind of fuzzy neural network able to accommodate in a simple framework the highly desirable property of incremental learning, as well as the usual capabilities of expert systems. We show how an interval-based representation for membership grades makes CNM capable of reasoning with several types of uncertainty: vagueness, ignorance, and relevance commonly found in practical applications. In addition, we show how basic functions of expert systems such as inference, inquiry, censorship of input information, and explanation may be implemented. We also report experimental results of the application of CNM to the problem of deforestation monitoring of the Amazon region using satellite images 相似文献
18.
The majority of patients with soft tissue or bone sarcomas of the upper extremity can be treated today with limb-saving procedures using combined modality therapies. For patients with a tumor in the shoulder area, sometimes an interscapulothoracic amputation is the only radical surgical treatment. However, in selected cases, in which the tumor does not involve the neurovascular bundle, a limb-sparing alternative might be the Tikhoff-Linberg resection. Normal function of the hand and forearm, with reasonable function of the elbow, can be maintained by this procedure. Four case histories are reported. 相似文献
19.
20.
柴油机低频排气噪声规律分析 总被引:4,自引:0,他引:4
针对柴油机(4-85)低频排气噪声,对其产生机理、规律及其影响因素等作了理论计算、分析及实验。对低频排气噪声信号进行频域分析后可知,其主要由一系列离散的谐波组成,是以柴油机点火频率为基频的一种类周期性噪声,有可能应用有源噪声控制技术。 相似文献