全文获取类型
收费全文 | 59867篇 |
免费 | 7363篇 |
国内免费 | 4738篇 |
专业分类
电工技术 | 5867篇 |
技术理论 | 7篇 |
综合类 | 6569篇 |
化学工业 | 9134篇 |
金属工艺 | 2155篇 |
机械仪表 | 4336篇 |
建筑科学 | 4961篇 |
矿业工程 | 1637篇 |
能源动力 | 5183篇 |
轻工业 | 1161篇 |
水利工程 | 5336篇 |
石油天然气 | 3944篇 |
武器工业 | 618篇 |
无线电 | 3395篇 |
一般工业技术 | 4755篇 |
冶金工业 | 3128篇 |
原子能技术 | 1368篇 |
自动化技术 | 8414篇 |
出版年
2024年 | 359篇 |
2023年 | 984篇 |
2022年 | 1831篇 |
2021年 | 2111篇 |
2020年 | 2213篇 |
2019年 | 1829篇 |
2018年 | 1658篇 |
2017年 | 2104篇 |
2016年 | 2302篇 |
2015年 | 2415篇 |
2014年 | 3577篇 |
2013年 | 3980篇 |
2012年 | 4166篇 |
2011年 | 4741篇 |
2010年 | 3392篇 |
2009年 | 3654篇 |
2008年 | 3399篇 |
2007年 | 4000篇 |
2006年 | 3689篇 |
2005年 | 3219篇 |
2004年 | 2669篇 |
2003年 | 2342篇 |
2002年 | 1895篇 |
2001年 | 1604篇 |
2000年 | 1316篇 |
1999年 | 1106篇 |
1998年 | 921篇 |
1997年 | 773篇 |
1996年 | 711篇 |
1995年 | 635篇 |
1994年 | 528篇 |
1993年 | 398篇 |
1992年 | 341篇 |
1991年 | 217篇 |
1990年 | 222篇 |
1989年 | 160篇 |
1988年 | 118篇 |
1987年 | 84篇 |
1986年 | 62篇 |
1985年 | 34篇 |
1984年 | 47篇 |
1983年 | 36篇 |
1982年 | 18篇 |
1981年 | 9篇 |
1980年 | 7篇 |
1979年 | 15篇 |
1977年 | 6篇 |
1975年 | 4篇 |
1959年 | 21篇 |
1951年 | 23篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
The recent trend of integration among new network services such as the long-term evolution (LTE) based on internet protocol (IP) needs reputable analyses and prediction information on the internet traffic. The IP along with increased internet traffics due to expanding new service platforms such as smartphones will reflect policies such as network QoS according to new services. The establishment of monitoring methods and analysis plans is thus required for the development of internet traffics that will analyze their status and predict their future. The paper with the speed of Internet traffic model is developed for monitoring the state of the experiment and verified. The problem is that the proposed service Internet service provider (ISP) to resolve the conflict between the occurrences can be considerably Internet traffic and that the state of data may be helpful in understanding. The paper advancement policy to reflect the network traffic volume of Internet services and users irradiation with increased traffic due to the development and management of the analysis was carried out experimental measurements. 相似文献
2.
Although rainfall input uncertainties are widely identified as being a key factor in hydrological models, the rainfall uncertainty is typically not included in the parameter identification and model output uncertainty analysis of complex distributed models such as SWAT and in maritime climate zones. This paper presents a methodology to assess the uncertainty of semi-distributed hydrological models by including, in addition to a list of model parameters, additional unknown factors in the calibration algorithm to account for the rainfall uncertainty (using multiplication factors for each separately identified rainfall event) and for the heteroscedastic nature of the errors of the stream flow. We used the Differential Evolution Adaptive Metropolis algorithm (DREAM(zs)) to infer the parameter posterior distributions and the output uncertainties of a SWAT model of the River Senne (Belgium). Explicitly considering heteroscedasticity and rainfall uncertainty leads to more realistic parameter values, better representation of water balance components and prediction uncertainty intervals. 相似文献
3.
A steelmaking-continuous casting (SCC) scheduling problem is an example of complex hybrid flow shop scheduling problem (HFSSP) with a strong industrial background. This paper investigates the SCC scheduling problem that involves controllable processing times (CPT) with multiple objectives concerning the total waiting time, earliness/tardiness and adjusting cost. The SCC scheduling problem with CPT is seldom discussed in the existing literature. This study is motivated by the practical situation of a large integrated steel company in which the just-in-time (JIT) and cost-cutting production strategy have become a significant concern. To address this complex HFSSP, the scheduling problem is decomposed into two subproblems: a parallel machine scheduling problem (PMSP) in the last stage and an HFSSP in the upstream stages. First, a hybrid differential evolution (HDE) algorithm combined with a variable neighborhood decomposition search (VNDS) is proposed for the former subproblem. Second, an iterative backward list scheduling (IBLS) algorithm is presented to solve the latter subproblem. The effectiveness of this bi-layer optimization approach is verified by computational experiments on well-designed and real-world scheduling instances. This study provides a new perspective on modeling and solving practical SCC scheduling problems. 相似文献
4.
Drunk drivers are a menace to themselves and to other road users, as drunk driving significantly increases the risk of involvement in road accidents and the probability of severe or fatal injuries. Although injuries and fatalities related to road accidents have decreased in recent decades, the prevalence of drunk driving among drivers killed in road accidents has remained stable, at around 25% or more during the past 10 years. Understanding drunk driving, and in particular, recidivism, is essential for designing effective countermeasures, and accordingly, the present study aims at identifying the differences between non-drunk drivers, drunk driving non-recidivists and drunk driving recidivists with respect to their demographic and socio-economic characteristics, road accident involvement and other traffic and non-traffic-related law violations. This study is based on register-data from Statistics Denmark and includes information from 2008 to 2012 for the entire population, aged 18 or older, of Denmark. The results from univariate and multivariate statistical analyses reveal a five year prevalence of 17% for drunk driving recidivism, and a significant relation between recidivism and the drunk drivers’ gender, age, income, education, receipt of an early retirement pension, household type, and residential area. Moreover, recidivists are found to have a higher involvement in alcohol-related road accidents, as well as other traffic and, in particular, non-traffic-related offences. These findings indicate that drunk driving recidivism is more likely to occur among persons who are in situations of socio-economic disadvantage and marginalisation. Thus, to increase their effectiveness, preventive measures aiming to reduce drunk driving should also address issues related to the general life situations of the drunk driving recidivists that contribute to an increased risk of drunk driving recidivism. 相似文献
5.
文章介绍了新一代IP骨干网上的IP QoS实现技术,论述了集成业务(IntServ)与差分业务(DiffServ)解决方案的特点,详细介绍了相关的队列管理与排队机制。并结合多协议标签交换(MPLS)技术的最新发展,阐述了综合多协议标签交换流量工程与DiffServ技术体系端到端IP QoS的实现。 相似文献
6.
7.
番禺30-1砂岩强水驱气藏储层非均质性研究 总被引:7,自引:5,他引:2
针对垂向非均质性严重且边底水能量强的番禺30-1气田面临的潜在开发问题,通过岩心分析及测井二次解释,对其夹层特征及储层非均质性等进行了研究,划分出19个流动单元并定量描述了各流动单元的特征参数,建立了该气田的精细地质模型。综合评价表明,新建的地质模型具有较高的精度,为该气藏合理开发提供了坚实的地质基础。 相似文献
8.
软件集成测试技术研究 总被引:1,自引:0,他引:1
首先分析了集成测试的原理和特点,并指出了集成测试的重要性。然后结合传统软件与面向对象软件开发的方法和技术,详细介绍了传统软件的集成测试方法和策略,并深入分析了面向对象软件集成测试的原理和方法。 相似文献
9.
为了提高非稳定渗流计算的计算精度 ,通过数学分析得到了水位传导系数随时间变化时 ,一类非稳定渗流井流模型的半解析解 ,并进行了计算比较 相似文献
10.
随着各高校校园网络规模的不断扩大和各种应用的急剧增加,各种新的网络问题也在不断出现。Sniffer是网络管理员进行网络管理的有效工具,可以有效地对网络进行实时监控,及时发现网络中存在的各种问题。本文首先介绍了Sniffer的工作原理,其次给出了实现Sniffer功能的编程流程图,并用C语言给出了编程所需的关键代码。 相似文献