全文获取类型
收费全文 | 78281篇 |
免费 | 8225篇 |
国内免费 | 4581篇 |
专业分类
电工技术 | 5678篇 |
技术理论 | 6篇 |
综合类 | 6335篇 |
化学工业 | 12283篇 |
金属工艺 | 4347篇 |
机械仪表 | 5004篇 |
建筑科学 | 6342篇 |
矿业工程 | 2285篇 |
能源动力 | 2276篇 |
轻工业 | 7459篇 |
水利工程 | 1725篇 |
石油天然气 | 3564篇 |
武器工业 | 860篇 |
无线电 | 9027篇 |
一般工业技术 | 8567篇 |
冶金工业 | 3160篇 |
原子能技术 | 794篇 |
自动化技术 | 11375篇 |
出版年
2024年 | 522篇 |
2023年 | 1706篇 |
2022年 | 3265篇 |
2021年 | 4178篇 |
2020年 | 2988篇 |
2019年 | 2397篇 |
2018年 | 2516篇 |
2017年 | 2753篇 |
2016年 | 2427篇 |
2015年 | 3573篇 |
2014年 | 4250篇 |
2013年 | 4743篇 |
2012年 | 5674篇 |
2011年 | 5865篇 |
2010年 | 5046篇 |
2009年 | 4869篇 |
2008年 | 4733篇 |
2007年 | 4371篇 |
2006年 | 4037篇 |
2005年 | 3469篇 |
2004年 | 2469篇 |
2003年 | 2282篇 |
2002年 | 2409篇 |
2001年 | 2001篇 |
2000年 | 1622篇 |
1999年 | 1384篇 |
1998年 | 993篇 |
1997年 | 870篇 |
1996年 | 732篇 |
1995年 | 669篇 |
1994年 | 508篇 |
1993年 | 389篇 |
1992年 | 308篇 |
1991年 | 242篇 |
1990年 | 186篇 |
1989年 | 151篇 |
1988年 | 126篇 |
1987年 | 72篇 |
1986年 | 72篇 |
1985年 | 54篇 |
1984年 | 24篇 |
1983年 | 10篇 |
1982年 | 32篇 |
1981年 | 22篇 |
1980年 | 32篇 |
1979年 | 15篇 |
1978年 | 4篇 |
1976年 | 4篇 |
1970年 | 3篇 |
1951年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
采用小纸层析系统1:1的氯仿/四氢呋喃展开剂分析^99mTc-HMPAO的放射化学纯度,并与两个薄层析系统和一个纸层析系统的方法作比较。配对t检验结果表明两种方法测定的放射化学纯度无显著差异;放射化学纯度在74.2%-96.4%,小纸层析法与薄层/纸层析法紧密相关,回归公式y=1.006x-0.323。 相似文献
22.
23.
24.
25.
26.
27.
This paper presents a methodology for specifying the winter and summer peak-load limits for substation transformers that carry a temperature-sensitive load, taking into account the random nature of load and ambient temperature as well as their correlation. With this methodology, we can easily and accurately specify the peak-load limits for each substation transformer once the historical ambient temperature and load data are available. Also, we can collectively specify the peak-load limits for the transformer of each cooling type (OA, OA/FA, or OA/FA/FA) in a geographic region based on the mean and standard deviation of ambient temperatures in that region. Such peak-load limits are useful for power system planning. 相似文献
28.
29.
The cardioprotective effects of EGb 761 on the release of nitric oxide (NO), the concentration of serum thiobarbituric acid reaction substance (TBARS), the activity of creatine kinase (CK) and the incidence of ventricular arrhythmias were investigated in myocardial ischemia-reperfusion injury in vivo. Using sodium nitrite (NaNO2) as standard source of nitric oxide (NO), we compared the correlation coefficients of the three measuring methods used currently in the determination of NOFe2+(DETC)2 complex with that of the measuring method suggested in this study. The result showed that measuring the whole height of three splitting signals is the best linear correlation to the concentration of NO comparing with other methods in this system. Using this method, we observed the effects of EGb 761 on NOFe2+(DETC)2 complex in myocardial ischemia-reperfusion injury in vivo. The hearts of the Wistar rats were subjected to 30 min of ischemia and 10 min of reperfusion in vivo. Different doses of EGb 761 (25, 50, 100, 200 mg/kg i.p.), superoxide dismutase (SOD, 10(4) U/kg), l-arginine (50 mg/kg i.p.) and nitric oxide synthase (NOS) inhibitor NG-nitro-l-arginine (NNA, 50 mg/kg i.p.) were administered to the ischemia-reperfusion rats. EGb 761 under the dose of 100 mg/kg increased the signal intensity of NOFe2+(DETC)2 complex, while EGb 761 at 200 mg/kg showed an effect of decreasing the signal intensity of NOFe2+(DETC)2 complex. EGb 761 inhibited the formation of TBARS, the release of CK, and mitigated the incidence of ventricular arrhythmias in a dose dependent way. Both l-arginine and SOD increased the signal intensity of NOFe2+(DETC)2 complex and inhibited the formation of TBARS, the leakage of CK and the incidence of ventricular arrhythmia. NNA not only had no protective effects on myocardial injury, but also increased the incidence of reperfusion-induced arrhythmia. In conclusion, EGb 761 has cardiovascular protective effects by means of adjusting the level of NO and inhibiting oxygen free radicals induced lipid peroxidation in myocardial ischemia-reperfusion injury in vivo. 相似文献
30.
In group assessment, the focus is on finding high‐authority experts to improve the reliability of assessment results. In this study, we propose an authority updating algorithm while considering the power and judgement reliability of an expert on the basis of social networks and post‐evaluations. A network power index is established and used to reflect the power of an expert while considering social networks. The measurement of the judgement reliability of an expert considers the post‐evaluation of the objects selected by experts, thereby more scientifically reflecting the reliability of experts. The analysis shows the following: although the social‐network structure influences the authority of experts, the influence weakens when the assessment group is a highly or even fully connected group; the network effect may increase the authority of some experts and reduce that of others, and it will weaken as the network connectivity increases; moreover, the judgement reliability and authority of an expert while considering post‐evaluation can encourage him/her to make fair assessments and strive to reduce his/her motivation and cognitive biases. 相似文献