全文获取类型
收费全文 | 10895篇 |
免费 | 774篇 |
国内免费 | 22篇 |
专业分类
电工技术 | 135篇 |
综合类 | 7篇 |
化学工业 | 2752篇 |
金属工艺 | 234篇 |
机械仪表 | 424篇 |
建筑科学 | 408篇 |
矿业工程 | 20篇 |
能源动力 | 425篇 |
轻工业 | 1889篇 |
水利工程 | 134篇 |
石油天然气 | 54篇 |
武器工业 | 2篇 |
无线电 | 719篇 |
一般工业技术 | 1790篇 |
冶金工业 | 997篇 |
原子能技术 | 88篇 |
自动化技术 | 1613篇 |
出版年
2024年 | 34篇 |
2023年 | 128篇 |
2022年 | 375篇 |
2021年 | 498篇 |
2020年 | 327篇 |
2019年 | 359篇 |
2018年 | 453篇 |
2017年 | 453篇 |
2016年 | 488篇 |
2015年 | 339篇 |
2014年 | 466篇 |
2013年 | 829篇 |
2012年 | 704篇 |
2011年 | 871篇 |
2010年 | 585篇 |
2009年 | 613篇 |
2008年 | 563篇 |
2007年 | 459篇 |
2006年 | 360篇 |
2005年 | 271篇 |
2004年 | 227篇 |
2003年 | 206篇 |
2002年 | 197篇 |
2001年 | 143篇 |
2000年 | 144篇 |
1999年 | 131篇 |
1998年 | 326篇 |
1997年 | 251篇 |
1996年 | 168篇 |
1995年 | 109篇 |
1994年 | 80篇 |
1993年 | 64篇 |
1992年 | 41篇 |
1991年 | 37篇 |
1990年 | 32篇 |
1989年 | 33篇 |
1988年 | 26篇 |
1987年 | 22篇 |
1986年 | 18篇 |
1985年 | 27篇 |
1984年 | 29篇 |
1983年 | 30篇 |
1982年 | 16篇 |
1981年 | 19篇 |
1980年 | 19篇 |
1979年 | 14篇 |
1978年 | 9篇 |
1977年 | 23篇 |
1976年 | 32篇 |
1973年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Assessing the role of basic control measures, antivirals and vaccine in curtailing pandemic influenza: scenarios for the US, UK and the Netherlands 总被引:1,自引:0,他引:1 下载免费PDF全文
An increasing number of avian flu cases in humans, arising primarily from direct contact with poultry, in several regions of the world have prompted the urgency to develop pandemic preparedness plans worldwide. Leading recommendations in these plans include basic public health control measures for minimizing transmission in hospitals and communities, the use of antiviral drugs and vaccination. This paper presents a mathematical model for the evaluation of the pandemic flu preparedness plans of the United States (US), the United Kingdom (UK) and the Netherlands. The model is used to assess single and combined interventions. Using data from the US, we show that hospital and community transmission control measures alone can be highly effective in reducing the impact of a potential flu pandemic. We further show that while the use of antivirals alone could lead to very significant reductions in the burden of a pandemic, the combination of transmission control measures, antivirals and vaccine gives the most 'optimal' result. However, implementing such an optimal strategy at the onset of a pandemic may not be realistic. Thus, it is important to consider other plausible alternatives. An optimal preparedness plan is largely dependent on the availability of resources; hence, it is country-specific. We show that countries with limited antiviral stockpiles should emphasize their use therapeutically (rather than prophylactically). However, countries with large antiviral stockpiles can achieve greater reductions in disease burden by implementing them both prophylactically and therapeutically. This study promotes alternative strategies that may be feasible and attainable for the US, UK and the Netherlands. It emphasizes the role of hospital and community transmission control measures in addition to the timely administration of antiviral treatment in reducing the burden of a flu pandemic. The latter is consistent with the preparedness plans of the UK and the Netherlands. Our results indicate that for low efficacy and coverage levels of antivirals and vaccine, the use of a vaccine leads to the greatest reduction in morbidity and mortality compared with the singular use of antivirals. However, as these efficacy and coverage levels are increased, the use of antivirals is more effective. 相似文献
52.
A parallel version of quicksort on a CRCW PRAM is developed. The algorithm uses n processors and a linear space to sort n keys in the expected time O(log n) with large probability. 相似文献
53.
Isothermal short-term creep of poly (vinylidene fluoride) (PVDF) monofilament sutures was determined at several temperatures between 10 and 90 °C under the stress of 10 MPa. Long term service performance was predicted for 10 decades of time. The compliance master curve as a function of time fits a hyperbolic sine equation. The temperature shift factor as a function of the temperature aT (T) is accurately represented by a general equation based on free volume. A simple relationship between the two parameters of the equation is explored. The viscoelasticity of PVDF is also seen in dynamic mechanical analysis performed at the frequency of 1 Hz. The origin of the viscoelastic character well present in the deformability of the PVDF in service is due to the occurrence of the αc relaxation that is active at ∼50 °C (E″ peak at 1 Hz). 相似文献
54.
Experimental results of a low-power roadheader driving a gallery with different types of rock at the face 总被引:1,自引:0,他引:1
J. Torao lvarez M. Menndez lvarez R. Rodríguez Díez 《Tunnelling and Underground Space Technology incorporating Trenchless Technology Research》2003,18(4):395-404
In this paper, the experimental results of a 45-kW and 15-t roadheader excavating a gallery with two different types of rock at the face using two different cutting heads are shown. It is proved that the roadheader works properly with both cutting heads. In comparison with other results in the literature, the principal parameters, i.e. specific energy, cutting rate and tool wear, are at a level that can be considered satisfactory taking into account the low power of the roadheader. On the other hand, the influence of the number of picks, which is the main difference between the two cutting heads, on the operational parameters is shown. 相似文献
55.
Copper phthalocyanine as corrosion inhibitor for ASTM A606-4 steel in 16% hydrochloric acid 总被引:2,自引:0,他引:2
A study based on the corrosion inhibition properties of copper phthalocyanine is described. Coverage degrees of copper phthalocyanine (Cu-phcy) on ASTM-A606-4 steel, obtained by weight loss measurements, were fitted to Langmuir, Frumkin, Temkin and Flory–Huggins adsorption isotherms. A better fit to the Langmuir isotherm was obtained. The polarization curves showed that polarization of both the anodic and cathodic reactions were verified for concentrations higher than 10–4 M, indicating a mixed type action. Only the anodic reactions were polarized for lower concentrations. At high frequencies the Nyquist diagrams showed one capacitive loop attributable to double layer charging and a small one at intermediary frequencies attributable to the faradaic process of hydrogen evolution. The formation of an adsorbed film was characterized by increasing charge transfer resistance values in the low frequency range for increasing inhibitor concentrations. According to the techniques used in this study, copper phthalocyanines showed a high corrosion inhibiting efficiency for all concentrations. 相似文献
56.
57.
58.
Yoon-Ha Jeong Seong-Kue Jo Bong-Hoon Lee Sugano T. 《Electron Device Letters, IEEE》1995,16(3):109-111
High performance enhancement mode InP MISFET's have been successfully fabricated by using the sulfide passivation for lower interface states and with photo-CVD grown P3N5 film used as gate insulator. The MISFET's thus fabricated exhibited exhibited pinch-off behavior with essentially no hysteresis. Furthermore the device showed a superior stability of drain current. Specifically under the gate bias of 2 V for 104 seconds the room temperature drain current was shown to reduce from the initial value merely by 2.9% at the drain voltage of 4 V. The effective electron mobility and extrinsic transconductance are found to be about 2300 cm 2/V·s and 2.7 mS/mm, respectively. The capacitance-voltage characteristics of the sulfide passivated InP MIS diodes show little hysteresis and the minimum density of interface trap states as low as 2.6×1014/cm2 eV has been attained 相似文献
59.
R Pérez Ferrari L Lambra?o R Aranda L Ferrabone 《Canadian Metallurgical Quarterly》1993,18(3):229-232
We studied the incidence of infection with Helicobacter pylori in Panamanians with chronic dyspepsia, gastric or duodenal ulcer, gastritis or gastric cancer. The histopathology was positive in 54 (81%) of 66 patients; the urea test was positive in 52 (82.5%) of 63 cases; the impromptu was positive in 51 (79.6) of 64 patients; the endoscopic examination was positive in 64 (82.9%) of 77 examinations. 相似文献
60.
J Caballero Güeto R Arana G Calle FJ Caballero Güeto E García del Río M Sancho C Pi?ero 《Canadian Metallurgical Quarterly》1997,50(12):906-908
Propionibacterium acnes is often considered to be a contaminant but it has also been found to be the principal pathogen in serious infections. P. acnes is a rare cause of infective endocarditis. It has been suggested that aortic root abscesses are caused by bacteria that are particularly virulent. The strongest risk factor for serious infections by this bacteria is the presence of foreign bodies. A case is presented in which endocarditis of a native aortic valve caused by P. acnes was associated with an aortic root abscess. Transesophageal echocardiography is particularly helpful in the diagnosis of this severe complication of infective endocarditis. The literature for P. acnes endocarditis is reviewed. 相似文献