全文获取类型
收费全文 | 111483篇 |
免费 | 10897篇 |
国内免费 | 5604篇 |
专业分类
电工技术 | 14216篇 |
技术理论 | 22篇 |
综合类 | 17344篇 |
化学工业 | 10395篇 |
金属工艺 | 3586篇 |
机械仪表 | 5999篇 |
建筑科学 | 15970篇 |
矿业工程 | 4977篇 |
能源动力 | 3485篇 |
轻工业 | 4908篇 |
水利工程 | 6012篇 |
石油天然气 | 5396篇 |
武器工业 | 879篇 |
无线电 | 8449篇 |
一般工业技术 | 7472篇 |
冶金工业 | 5116篇 |
原子能技术 | 1300篇 |
自动化技术 | 12458篇 |
出版年
2024年 | 448篇 |
2023年 | 1143篇 |
2022年 | 2327篇 |
2021年 | 2696篇 |
2020年 | 2930篇 |
2019年 | 2435篇 |
2018年 | 2365篇 |
2017年 | 3115篇 |
2016年 | 3442篇 |
2015年 | 4003篇 |
2014年 | 7867篇 |
2013年 | 6536篇 |
2012年 | 7839篇 |
2011年 | 8476篇 |
2010年 | 6584篇 |
2009年 | 7227篇 |
2008年 | 6645篇 |
2007年 | 8286篇 |
2006年 | 7650篇 |
2005年 | 6373篇 |
2004年 | 5390篇 |
2003年 | 4521篇 |
2002年 | 3681篇 |
2001年 | 3039篇 |
2000年 | 2626篇 |
1999年 | 2034篇 |
1998年 | 1425篇 |
1997年 | 1115篇 |
1996年 | 1018篇 |
1995年 | 881篇 |
1994年 | 819篇 |
1993年 | 593篇 |
1992年 | 498篇 |
1991年 | 356篇 |
1990年 | 320篇 |
1989年 | 309篇 |
1988年 | 224篇 |
1987年 | 151篇 |
1986年 | 122篇 |
1985年 | 87篇 |
1984年 | 74篇 |
1983年 | 50篇 |
1982年 | 42篇 |
1981年 | 46篇 |
1980年 | 37篇 |
1979年 | 27篇 |
1978年 | 12篇 |
1975年 | 16篇 |
1959年 | 12篇 |
1951年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
Jean-Claude Malela-Majika Sandile Charles Shongwe Olatunde Adebayo Adeoti 《Quality and Reliability Engineering International》2021,37(8):3314-3322
The sensitivity of a monitoring scheme depends on many factors including the variance of the charting statistic which is very important in the computation of the control limits. This paper discusses the computation of the variance of the recently proposed hybrid homogeneously weighted moving average (HHWMA) scheme which was based on an incorrect assumption. The correct variance is used to evaluate the run-length characteristics of the HHWMA scheme. It is observed that the incorrect variance has a significant impact on the sensitivity (or performance) of the HHWMA scheme. 相似文献
2.
Structural health monitoring system based on multi-agent coordination and fusion for large structure
In practical applications of structural health monitoring technology, a large number of distributed sensors are usually adopted to monitor the big dimension structures and different kinds of damage. The monitored structures are usually divided into different sub-structures and monitored by different sensor sets. Under this situation, how to manage the distributed sensor set and fuse different methods to obtain a fast and accurate evaluation result is an important problem to be addressed deeply. In the paper, a multi-agent fusion and coordination system is presented to deal with the damage identification for the strain distribution and joint failure in the large structure. Firstly, the monitoring system is adopted to distributedly monitor two kinds of damages, and it self-judges whether the static load happens in the monitored sub-region, and focuses on the static load on the sub-region boundary to obtain the sensor network information with blackboard model. Then, the improved contract net protocol is used to dynamically distribute the damage evaluation module for monitoring two kinds of damage uninterruptedly. Lastly, a reliable assessment for the whole structure is given by combing various heterogeneous classifiers strengths with voting-based fusion. The proposed multi-agent system is illustrated through a large aerospace aluminum plate structure experiment. The result shows that the method can significantly improve the monitoring performance for the large-scale structure. 相似文献
3.
4.
The supervision of a hybrid power plant, including solar panels, a gas microturbine and a storage unit operating under varying solar power profiles is considered. The Economic Supervisory Predictive controller assigns the power references to the controlled subsystems of the hybrid cell using a financial criterion. A prediction of the renewable sources power is embedded into the supervisor. Results deteriorate when the solar power is unsteady, owing to the inaccuracy of the predictions for a long-range horizon of 10 s. The receding horizon is switched between an upper and a lower value according to the amplitude of the solar power trend. Theoretical results show the relevance of horizon switching, according to a tradeoff between performance and prediction accuracy. Experimental results, obtained in a Hardware In the Loop (HIL) framework, show the relevance of the variable horizon approach. Power amplifiers allow us to simulate virtual components, such as a gas microturbine, and to blend their powers with that of real devices (storage unit, real solar panels). In this case, fuel savings, reaching 15%, obtained under unsteady operating conditions lead to a better overall performance of the hybrid cell. The overall savings obtained in the experiments amount to 12%. 相似文献
5.
Private information retrieval(PIR) is an important privacy protection issue of secure multi-party computation, but the PIR protocols based on classical cryptography are vulnerable because of new technologies,such as quantum computing and cloud computing. The quantum private queries(QPQ) protocols available, however, has a high complexity and is inefficient in the face of large database. This paper, based on the QKD technology which is mature now, proposes a novel QPQ protocol utilizing the key dilution and auxiliary parameter. Only N quits are required to be sent in the quantum channel to generate the raw key, then the straight k bits in the raw key are added bitwise to dilute the raw key, and a final key is consequently obtained to encrypt the database. By flexible adjusting of auxiliary parameters θ and k, privacy is secured and the query success ratio is improved. Feasibility and performance analyses indicate that the protocol has a high success ratio in first-trial query and is easy to implement, and that the communication complexity of O(N) is achieved. 相似文献
7.
电网的安全水平主要取决于其使用产品的质量是否过关。如果产品的质量较好,则能建造出优质的电网,电网的安全水平便会随之提高。因此,应加强对产品质量的监督管理,从而提高电网的安全水平。我们可建立质量监督管理系统,及时抽检出质量不过关的产品,从而消除电网运行过程中潜在的安全隐患。 相似文献
8.
《Planning》2015,(1)
目的 探讨气管上段腺样囊性癌的临床病理特征及诊断和鉴别诊断要点。方法 收集2000年1月至2014年2月在北京协和医院确诊的4例气管上段腺样囊性癌病例,通过光镜、免疫组织化学及组织化学染色分析其临床病理特征、免疫组织化学特点、诊断及鉴别诊断要点。结果 4例气管上段腺样囊性癌患者中,男1例,女3例,平均年龄47岁(38~57岁);既往均无腺样囊性癌病史,1例患者既往有结节性甲状腺肿手术史。镜下检查4例均为筛状/管状型腺样囊性癌,3例累及甲状腺组织,3例累及神经组织,未见淋巴结受累。免疫组织化学染色示4例P16、CD117、BCL2、P63、SMA均阳性,Ki67指数平均8%,TTF1和P53均阴性;4例中基底膜样物胶原Ⅳ阳性;组织化学染色示AB/PAS阳性。术后均接受总剂量为48~56 Gy的放疗,随访6~120个月,平均72.5个月,1例术后96个月复发,3例随访期间无复发及转移。结论 气管上段腺样囊性癌是罕见的原发于气管的低度恶性肿瘤,肿瘤生长缓慢,就诊时多数已侵及甲状腺组织,需要与原发于甲状腺的恶性肿瘤相鉴别,特别是在甲状腺穿刺及术中冰冻检查时。结合电子喉气管镜下表现、典型的形态学及免疫组织化学和组织化学染色有助于准确诊断。手术难以切除干净,术后放疗对延缓疾病复发有一定帮助。 相似文献
9.
Eight datasets of 1-h black carbon (BC) concentrations measured in Warsaw agglomeration (Poland), at urban background and sub-urban sites, and in Racibórz, a small town in Upper Silesia district (regional background site) were analyzed to evaluate BC levels, daily profiles and statistical distributions of concentrations in Central-Eastern European region. The observed mean levels ranged from 1483 ng m−3 in suburban site during summer to 3358 ng m−3 in regional background site in winter. Observed diurnal patterns were bimodal in the locations dominated by traffic emissions, but unimodal, with elevated evening peak in individually heated residential area. Three theoretical frequency distributions were applied to fit analyzed datasets separately. The lognormal distribution was the most appropriate to represent the middle-range values, while the high concentrations were satisfactorily predicted by the type I two-parameter exponential distribution which was used to estimate the return periods of extreme concentrations for winter months. 相似文献
10.