全文获取类型
收费全文 | 6080篇 |
免费 | 53篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 21篇 |
综合类 | 6篇 |
化学工业 | 155篇 |
金属工艺 | 10篇 |
机械仪表 | 43篇 |
建筑科学 | 9篇 |
矿业工程 | 7篇 |
能源动力 | 20篇 |
轻工业 | 62篇 |
水利工程 | 4篇 |
石油天然气 | 5篇 |
无线电 | 112篇 |
一般工业技术 | 122篇 |
冶金工业 | 5472篇 |
原子能技术 | 4篇 |
自动化技术 | 83篇 |
出版年
2023年 | 4篇 |
2022年 | 14篇 |
2021年 | 11篇 |
2020年 | 13篇 |
2019年 | 15篇 |
2018年 | 19篇 |
2017年 | 28篇 |
2016年 | 31篇 |
2015年 | 16篇 |
2014年 | 29篇 |
2013年 | 42篇 |
2012年 | 35篇 |
2011年 | 64篇 |
2010年 | 41篇 |
2009年 | 32篇 |
2008年 | 42篇 |
2007年 | 38篇 |
2006年 | 26篇 |
2005年 | 17篇 |
2004年 | 17篇 |
2003年 | 22篇 |
2002年 | 15篇 |
2001年 | 14篇 |
2000年 | 14篇 |
1999年 | 177篇 |
1998年 | 1682篇 |
1997年 | 932篇 |
1996年 | 598篇 |
1995年 | 341篇 |
1994年 | 299篇 |
1993年 | 315篇 |
1992年 | 46篇 |
1991年 | 61篇 |
1990年 | 79篇 |
1989年 | 67篇 |
1988年 | 75篇 |
1987年 | 73篇 |
1986年 | 57篇 |
1985年 | 65篇 |
1984年 | 3篇 |
1983年 | 13篇 |
1982年 | 32篇 |
1981年 | 30篇 |
1980年 | 54篇 |
1979年 | 6篇 |
1978年 | 14篇 |
1977年 | 158篇 |
1976年 | 341篇 |
1975年 | 5篇 |
1955年 | 4篇 |
排序方式: 共有6135条查询结果,搜索用时 15 毫秒
71.
Seung-hwan Choi Chunghwan Jeon Young June Chang 《Journal of Mechanical Science and Technology》2002,16(7):986-998
Flow and spray characteristics are critical factors that affect the performance and exhaust emissions of a direct injection
diesel engine. It is well known that the swirl control system is one of the useful ways to improve the fuel consumption and
emission reduction rate in a diesel engine. However, until now there have only been a few studies on the effect of flow on
spray. Because of this, the relationship between the flow pattern in the cylinder and its influence on the behavior of the
spray is in need of investigation. First, in-cylinder flow distributions for 4-valve cylinder head of Dl (Direct Injection)
Diesel engine were investigated under steady-state conditions for different SCV (Swirl Control Valve) opening angles using
a steady flow rig and 2-D LDV (Laser Doppler Velocimetry). It was found that swirl flow was more dominant than that of tumble
in the experimented engine. In addition, the in-cylinder flow was quantified in terms of swirl/tumble ratio and mean flow
coefficient. As the SCV opening angle was increased, high swirl ratios more than 3.0 were obtained in the case of SCV -70ΰ
and 90ΰ. Second, spray characteristics of the intermittent injection were investigated by a PDA (Phase Doppler Anemometer)
system. A Time Dividing Method (TDM) was used to analyze the microscopic spray characteristics. It was found that the atomization
characteristics such as velocity and SMD (Sauter Mean Diameter) of the spray were affected by the in-cylinder swirl ratio.
As a result, it was concluded that the swirl ratio improves atomization characteristics uniformly. 相似文献
72.
Effects of mineral oil coating on internal quality of chicken eggs under refrigerated storage 总被引:1,自引:0,他引:1
Wannita Jirangrat Damir Dennis Torrico June No Hong Kyoon No Witoon Prinyawiwatkul 《International Journal of Food Science & Technology》2010,45(3):490-495
The selected internal qualities (weight loss, Haugh unit, yolk index, and albumen pH) of noncoated and mineral oil‐coated chicken eggs during 15 weeks of storage at 4 °C and/or during 5 weeks of storage at 25 °C were evaluated. Results indicated that, without refrigeration, the noncoated and mineral oil‐coated eggs rapidly changed from AA to C and B grades as measured by Haugh unit, respectively, after 5 weeks of storage. However, the AA quality of the noncoated eggs could be maintained under refrigerated storage (4 °C) for at least 5 weeks. The mineral oil coating and refrigerated storage (4 °C) synergistically minimised weight loss and preserved the albumen and yolk qualities of chicken eggs during a long‐term storage. At 4 °C, the mineral oil‐coated eggs preserved the initial AA grade for at least 15 weeks with l.19% weight loss. 相似文献
73.
74.
Dipl. Wirt.-Inform. Ralf Knackstedt Christian Brelage RA Master of Arts Noogie C. Kaufmann 《WIRTSCHAFTSINFORMATIK》2006,48(1):27-35
A broad variety of juridical requirements has to be considered during the development of Web-applications. Disregard of these requirements holds severe financial dangers. A complete compilation of juridical requirements is complicated due to the multitude of juridical areas and the variety of Web-applications. Therefore, a development-driven juridical framework is suggested. From a software engineering point of view it is crucial to capture requirements at an early stage of development in order to avoid much higher costs at a later time. Thus, specialized conceptual modelling methods are examined with regard to their capability to model juridical requirements. A lack of methodical support is identified which is addressed by a systematic adaption and extension of the eW3DT method. 相似文献
75.
76.
NR Powe RI Griffiths AJ Watson GF Anderson G de Lissovoy JW Greer RJ Herbert RA Milam PK Whelton 《Canadian Metallurgical Quarterly》1994,4(7):1455-1465
To examine the effects of recombinant human erythropoietin (rHuEPO) on hospital utilization, hospital costs, and Medicare reimbursements for hospital care, a longitudinal, matched cohort study was conducted using Medicare claims data of 23,806 Medicare-eligible, dialysis patients who received rHuEPO, did not have a transplant, and were alive for 18 mo or longer and 22,720 controls matched on age, sex, race, cause of ESRD, and dialysis modality. The relative odds (rHuEPO versus control) of admission for all causes and for specific causes over 9 mo, adjusted for admission in the prior 9 mo and the per patient change in total admissions, inpatient days, hospital costs, and Medicare hospital payments between the prior 9-mo period and the subsequent 9-mo period was examined. The adjusted relative odds (95% confidence interval) of admission (rHuEPO versus control) was: higher and statistically significant for all causes, 1.08 (1.03 to 1.14); seizure, 1.52 (1.28 to 1.75); vascular access revision, 1.11 (1.06 to 1.17), and heart failure, 1.17 (1.09 to 1.26); higher but not statistically significant for angina, 1.09 (0.99 to 1.20) and stroke, 1.08 (0.86 to 1.31); and lower but not statistically significant for myocardial infarction, 0.91 (0.72 to 1.10); peripheral vascular disease, 0.81 (0.60 to 1.02); anemia, 0.86 (0.56 to 1.17); and depression, 0.89 (0.37 to 1.40). The mean change per 1,000 patients in admissions was less by 38 (P = 0.03) because of fewer readmissions, and in days was 1,309 less (P < 0.001), for patients treated with rHuEPO versus controls. The mean change per patient in hospital costs was $371 less and was statistically significant (P = 0.03) and in Medicare hospital payments was $132 less but was not statistically significant (P = 0.43) for patients treated with rHuEPO versus controls. rHuEPO was associated with an increase in the probability of hospital admission (particularly admissions potentially related to adverse effects) but a decrease in readmissions, overall admissions, hospital days, and cost to hospitals in this cohort of patients surviving for 18 mo. Although not realized short term, Medicare savings from potential rHuEPO-related reductions in hospital care may be long term through future adjustments in diagnosis-related group-based hospital payment. 相似文献
77.
78.
79.
80.
Five non-smoking patients were diagnosed as having allergic bronchopulmonary aspergillosis in 1978/9. All have been treated since then with inhaled corticosteroids, using short courses of self-administered oral corticosteroids for symptomatic exacerbations. Over a mean 15 years of follow-up, they have required on average less than one course of oral drugs per annum. Regular monitoring of spirometry has shown no evidence of deterioration, and all have close to normal gas transfer. All have some localized bronchiectasis on CT scanning, in two cases probably occurring after treatment started, but in no case is there any respiratory disability. We conclude that this is a safe and effective method for the management of allergic bronchopulmonary aspergillosis when diagnosed before persistent hyphal colonization of the airways has occurred. 相似文献