全文获取类型
收费全文 | 214201篇 |
免费 | 21437篇 |
国内免费 | 12524篇 |
专业分类
电工技术 | 19253篇 |
技术理论 | 8篇 |
综合类 | 21791篇 |
化学工业 | 23969篇 |
金属工艺 | 8640篇 |
机械仪表 | 17224篇 |
建筑科学 | 24133篇 |
矿业工程 | 8594篇 |
能源动力 | 9158篇 |
轻工业 | 18648篇 |
水利工程 | 9254篇 |
石油天然气 | 9991篇 |
武器工业 | 2366篇 |
无线电 | 11915篇 |
一般工业技术 | 20607篇 |
冶金工业 | 8037篇 |
原子能技术 | 2767篇 |
自动化技术 | 31807篇 |
出版年
2024年 | 975篇 |
2023年 | 2957篇 |
2022年 | 5495篇 |
2021年 | 6500篇 |
2020年 | 6929篇 |
2019年 | 5997篇 |
2018年 | 5813篇 |
2017年 | 6913篇 |
2016年 | 8131篇 |
2015年 | 8530篇 |
2014年 | 13516篇 |
2013年 | 13824篇 |
2012年 | 15696篇 |
2011年 | 17239篇 |
2010年 | 12391篇 |
2009年 | 12903篇 |
2008年 | 12002篇 |
2007年 | 14354篇 |
2006年 | 12513篇 |
2005年 | 10550篇 |
2004年 | 8973篇 |
2003年 | 7561篇 |
2002年 | 6105篇 |
2001年 | 5092篇 |
2000年 | 4398篇 |
1999年 | 3781篇 |
1998年 | 3194篇 |
1997年 | 2701篇 |
1996年 | 2245篇 |
1995年 | 1847篇 |
1994年 | 1651篇 |
1993年 | 1266篇 |
1992年 | 1181篇 |
1991年 | 841篇 |
1990年 | 667篇 |
1989年 | 580篇 |
1988年 | 472篇 |
1987年 | 325篇 |
1986年 | 277篇 |
1985年 | 239篇 |
1984年 | 297篇 |
1983年 | 269篇 |
1982年 | 230篇 |
1981年 | 109篇 |
1980年 | 111篇 |
1979年 | 81篇 |
1978年 | 62篇 |
1977年 | 53篇 |
1976年 | 45篇 |
1959年 | 31篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Guo-Yu Li Ya-Xin Zheng Fu-Zhou Sun Jian Huang Meng-Meng Lou Jing-Kai Gu Jin-Hui Wang 《International journal of molecular sciences》2015,16(9):22190-22204
This study aimed at investigating the possible mechanisms of hepatic protective activity of Cichorium intybus L. (chicory) in acute liver injury. Pathological observation, reactive oxygen species (ROS) detection and measurements of biochemical indexes on mouse models proved hepatic protective effect of Cichorium intybus L. Identification of active compounds in Cichorium intybus L. was executed through several methods including ultra performance liquid chromatography/time of flight mass spectrometry (UPLC-TOF-MS). Similarity ensemble approach (SEA) docking, molecular modeling, molecular docking, and molecular dynamics (MD) simulation were applied in this study to explore possible mechanisms of the hepato-protective potential of Cichorium intybus L. We then analyzed the chemical composition of Cichorium intybus L., and found their key targets. Furthermore, in vitro cytological examination and western blot were used for validating the efficacy of the selected compounds. In silico analysis and western blot together demonstrated that selected compound 10 in Cichorium intybus L. targeted Akt-1 in hepatocytes. Besides, compound 13 targeted both caspase-1 and Akt-1. These small compounds may ameliorate liver injury by acting on their targets, which are related to apoptosis or autophagy. The conclusions above may shed light on the complex molecular mechanisms of Cichorium intybus L. acting on hepatocytes and ameliorating liver injury. 相似文献
52.
《International Journal of Hydrogen Energy》2020,45(38):19720-19732
The need to reduce PEMFC systems cost as well as to increase their durability is crucial for their integration in various applications and especially for transport applications. A new simplified architecture of the anode circuit called Alternating Fuel Feeding (AFF) offers to reduce the development costs. Requiring a new stack concept, it combines the simplicity of Dead-End Anode (DEA) with the operation advantages of the hydrogen recirculation. The three architectures (DEA, recirculation and AFF) are compared in terms of performance on a 5-kW test bench in automotive conditions, through a sensitivity analysis. A gain of 17% on the system efficiency is observed when switching from DEA to AFF. Moreover, similar performances are obtained both for AFF and for recirculation after an accurate optimization of the AFF tuning parameters. Based on DoE data, a gain of 25% on the weight of the anodic line has been identified compared to pulsed ejector architecture and 43% with the classic recirculation architecture with blower only (Miraï). 相似文献
53.
An integrated approach to measure the cost efficiency of the postal network of Universal Service Provider is proposed. An integrated approach enables the measurement of cost efficiency for delivery and non-delivery postal network units. The proposed approach is verified and tested on the postal network of the selected provider and the results were derived by using Data Envelopment Analysis (DEA). The results show that the main sources of inefficiency are inadequate allocation of resources relative to the network units. In addition, the study indicates that economies of scale have a positive impact on the efficiency of postal network units. 相似文献
54.
Nazir Kizzie‐Hayford Doris Jaros Yvonne Schneider Harald Rohm 《International Journal of Food Science & Technology》2015,50(2):381-388
A standard method for the extraction of tiger nut milk has been introduced. It has been shown that, although milling duration improves the yield of tiger nut milk solids and its nutrient composition, there is a quantifiable loss of nutrient in the pressing residue during milk extraction. Milling duration improved the colloidal stability of the milk against creaming during 16 h of storage. A higher milling intensity resulted in the aggregation of biological polymers which resulted in colloidal destabilisation. Milling improved the lightness and stability and reduced browning rate of the tiger nut milk during storage. This report is important for the production of tiger nut milk of consistent and comparable characteristics. Milling has been introduced as a processing method for the qualitative and quantitative modulation of the properties of tiger nut milk. It is recommended to develop further strategies to improve the colloidal stability of tiger nut milk as a beverage. 相似文献
55.
56.
In this paper, an adaptive control approach is designed for compensating the faults in the actuators of chaotic systems and maintaining the acceptable system stability. We propose a state‐feedback model reference adaptive control scheme for unknown chaotic multi‐input systems. Only the dimensions of the chaotic systems are required to be known. Based on Lyapunov stability theory, new adaptive control laws are synthesized to accommodate actuator failures and system nonlinearities. An illustrative example is studied. The simulation results show the effectiveness of the design method. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
57.
This paper deals with the application of wavelet transforms for the detection, classification and location of faults on transmission lines. A Global Positioning System clock is used to synchronize sampling of voltage and current signals at both the ends of the transmission line. The detail coefficients of current signals of both the ends are utilized to calculate fault indices. These fault indices are compared with threshold values to detect and classify the faults. Artificial Neural Networks are employed to locate the fault, which make use of approximate decompositions of the voltages and currents of local end. The proposed algorithm is tested successfully for different locations and types of faults. 相似文献
58.
59.
The lack of consensus on the meaning of energy security and how it should be measured hinders the evaluation of alternatives for improving the Cape Verdean energy sector. The objective of the paper is to develop an energy security index adjusted to the country's context. The methods used are the multi-criteria analysis and the Delphi survey. Different alternatives to improve energy security are assessed: electrically interconnect Cape Verde's islands, increase the share of renewable energy, and a combination of the previous alternatives. The results of our analysis indicate that increasing renewable energy is the optimal alternative for Cape Verde. 相似文献
60.
为研究喷射混凝土套拱加固前后二次衬砌与混凝土套拱的受力状况,依托陕西汉中至留坝段八里关隧道,运用有限元软件建立隧道混凝土结构套拱加固分析模型,并通过现场监测获取二次衬砌与套拱间的接触压力、套拱格栅拱架钢筋应力、套拱混凝土应力,将数值模拟结果与现场测试结果相结合,得出套拱结构的一般受力变化规律。结果表明:套拱加固前衬砌结构的最不利荷载位置位于施工缝附近的拱顶、拱肩与拱脚处; 由于衬砌局部变形与温度应力的影响,套拱混凝土应力变化呈现反复“上升-下降-上升”最后趋于稳定的特点; 套拱的作用是控制二次衬砌的进一步变形,套拱施作后所承受荷载较小,套拱反作用力远小于围岩作用于衬砌的应力,在应力计算中不应将衬砌与套拱作为整体计算; 套拱结构数值模拟所得的结果与现场测试套拱结构内力(轴力、弯矩)的大小及分布相似度高,但在衬砌裂损严重部位,数值模拟所得结果误差较大,应以现场测试结果为准。 相似文献