全文获取类型
收费全文 | 122976篇 |
免费 | 15687篇 |
国内免费 | 6308篇 |
专业分类
电工技术 | 28334篇 |
综合类 | 8953篇 |
化学工业 | 17855篇 |
金属工艺 | 4643篇 |
机械仪表 | 6111篇 |
建筑科学 | 7498篇 |
矿业工程 | 3422篇 |
能源动力 | 3167篇 |
轻工业 | 8679篇 |
水利工程 | 2129篇 |
石油天然气 | 3796篇 |
武器工业 | 856篇 |
无线电 | 18566篇 |
一般工业技术 | 9779篇 |
冶金工业 | 5221篇 |
原子能技术 | 1360篇 |
自动化技术 | 14602篇 |
出版年
2024年 | 368篇 |
2023年 | 1805篇 |
2022年 | 3943篇 |
2021年 | 5859篇 |
2020年 | 3978篇 |
2019年 | 3479篇 |
2018年 | 3585篇 |
2017年 | 4876篇 |
2016年 | 6231篇 |
2015年 | 7118篇 |
2014年 | 8999篇 |
2013年 | 8320篇 |
2012年 | 8703篇 |
2011年 | 8460篇 |
2010年 | 6517篇 |
2009年 | 6635篇 |
2008年 | 6389篇 |
2007年 | 8139篇 |
2006年 | 7854篇 |
2005年 | 6437篇 |
2004年 | 4879篇 |
2003年 | 4364篇 |
2002年 | 3457篇 |
2001年 | 2720篇 |
2000年 | 2368篇 |
1999年 | 1639篇 |
1998年 | 1152篇 |
1997年 | 999篇 |
1996年 | 944篇 |
1995年 | 776篇 |
1994年 | 708篇 |
1993年 | 547篇 |
1992年 | 453篇 |
1991年 | 341篇 |
1990年 | 317篇 |
1989年 | 279篇 |
1988年 | 195篇 |
1987年 | 136篇 |
1986年 | 95篇 |
1985年 | 104篇 |
1984年 | 118篇 |
1983年 | 83篇 |
1982年 | 60篇 |
1981年 | 49篇 |
1980年 | 55篇 |
1979年 | 27篇 |
1966年 | 30篇 |
1964年 | 41篇 |
1962年 | 71篇 |
1955年 | 27篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Parkinson’s disease (PD) is a neurodegenerative disorder that affects 1% of the population over the age of 60. Diabetes Mellitus (DM) is a metabolic disorder that affects approximately 25% of adults over the age of 60. Recent studies showed that DM increases the risk of developing PD. The link between DM and PD has been discussed in the literature in relation to different mechanisms including mitochondrial dysfunction, oxidative stress, and protein aggregation. In this paper, we review the common microRNA (miRNA) biomarkers of both diseases. miRNAs play an important role in cell differentiation, development, the regulation of the cell cycle, and apoptosis. They are also involved in the pathology of many diseases. miRNAs can mediate the insulin pathway and glucose absorption. miRNAs can also regulate PD-related genes. Therefore, exploring the common miRNA biomarkers of both PD and DM can shed a light on how these two diseases are correlated, and targeting miRNAs is a potential therapeutic opportunity for both diseases. 相似文献
22.
Xiao-Lei Qiu Zi-Rui Fan Yang-Yang Liu Ding-Fu Wang Shi-Xin Wang Chun-Xia Li 《International journal of molecular sciences》2021,22(8)
A self-nanoemulsifying drug delivery system (SNEDDS) was developed to enhance the absorption of heparin after oral administration, in which heparin was compounded with phospholipids to achieve better fat solubility in the form of heparin-phospholipid (HEP-Pc) complex. HEP-Pc complex was prepared using the solvent evaporation method, which increased the solubility of heparin in n-octanol. The successful preparation of HEP-Pc complex was confirmed by differential scanning calorimetry (DSC), Fourier-transform infrared (FT-IR) spectroscopy, NMR, and SEM. A heparin lipid microemulsion (HEP-LM) was prepared by high-pressure homogenization and characterized. HEP-LM can enhance the absorption of heparin after oral administration, significantly prolong activated partial thromboplastin time (APTT) and thrombin time (TT) in mice, and reduce fibrinogen (FIB) content. All these outcomes indicate that HEP-LM has great potential as an oral heparin formulation. 相似文献
23.
24.
25.
针对现有基于视频监控的人流量统计方案成本高、算法复杂且不利于个人隐私保护的局限性,利用毫米波雷达体积小、成本低、分辨率高的特点,提出了一种基于双时间点检测的人流量监测方法。该方法先获取人体目标散射点位置和多普勒频移信息来构成点云数据,然后根据多普勒频移正负来判断人体的运动方向,并筛选具有高多普勒频移值的点云数据以降低干扰点对聚类结果的影响;在双时间点对特定区域内人员数量进行统计,并根据双时间点之间所获取的点云数据聚类结果对所统计人员数据进行修正。实验结果表明,该方法能够用匿名的方式以较高的正确率统计人员进出。 相似文献
26.
海胆酮是一种酮式类胡萝卜素,主要从海胆及藻类等海洋生物中提取。本文研究海胆酮对乙酰胆碱酯酶(acetylcholinesterase,AChE)的抑制作用,应用酶动力学、荧光光谱、圆二色光谱和分子对接技术研究海胆酮对AChE的抑制机理,并用淀粉样β蛋白片段25~35(amyloid beta-peptide 25-35,Aβ25-35)诱导大鼠肾上腺嗜铬细胞瘤细胞(PC12细胞)建立阿尔茨海默症(Alzheimer’s disease,AD)模型,研究海胆酮对AD细胞模型氧化应激损伤的作用。结果表明,海胆酮有很强的AChE抑制活性,其半抑制质量浓度为(16.29±0.97)μg/mL,抑制常数Ki为3.82 μg/mL,表现为竞争性抑制;海胆酮可诱导AChE二级结构改变,更容易与AChE活性中心氨基酸Ser200、His440、Trp84和Tyr121结合,阻碍底物碘代硫代乙酰胆碱(acetylthiocholine iodide,ATCI)与酶结合,从而引起酶活力降低。海胆酮能有效抑制Aβ25-35诱导PC12细胞的AChE活力,降低丙二醛含量,增加超氧化物歧化酶、过氧化氢酶和谷胱甘肽过氧化物酶活力,减轻Aβ25-35诱导的PC12细胞氧化应激损伤。本研究基于AChE和氧化应激阐明了海胆酮对AD的潜在作用机制,为海胆酮在功能食品、生物医药等领域的应用提供了数据支持和理论根据。 相似文献
27.
One specific class of non-linear evolution equations, known as the Tzitzéica-type equations, has received great attention from a group of researchers involved in non-linear science. In this article, new exact solutions of the Tzitzéica-type equations arising in non-linear optics, including the Tzitzéica, Dodd–Bullough–Mikhailov and Tzitzéica–Dodd–Bullough equations, are obtained using the expa function method. The integration technique actually suggests a useful and reliable method to extract new exact solutions of a wide range of non-linear evolution equations. 相似文献
28.
This paper proposes a method for the coordinated control of power factor by means of a multiagent approach. The proposed multiagent system consists of two types of agent: single feeder agent (F_AG) and bus agent (B_AG). In the proposed system, an F_AG plays as an important role, which decides the power factors of all distributed generators by executing the load flow calculations repeatedly. The voltage control strategies are implemented as the class definition of Java into the system. In order to verify the performance of the proposed method, it has been applied to a typical distribution model system. The simulation results show that the system is able to control very violent fluctuation of the demands and the photovoltaic (PV) generations. 相似文献
29.
30.
To improve the convertibility of reconfigurable manufacturing system (RMS), the concept of delayed reconfigurable manufacturing system (D-RMS) was proposed. RMS and D-RMS are both constructed around part family. However, D-RMS may suffer from ultra-long system problem with unacceptable idle machines using generic RMS part families. Besides, considering the complex basic system structure of D-RMS, machine selection of D-RMS should be addressed, including dedicated machine, flexible machine, and reconfigurable machine. Therefore, a system design method for D-RMS based on part family grouping and machine selection is proposed. Firstly, a part family grouping method is proposed for D-RMS that groups the parts with more former common operations into the same part family. The concept of longest relative position common operation subsequence (LPCS) is proposed. The similarity coefficient among the parts is calculated based on LPCS. The reciprocal value of the operation position of LPCS is adopted as the characteristic value. The average linkage clustering (ALC) algorithm is used to cluster the parts. Secondly, a machine selection method is proposed to complete the system design of D-RMS, including machine selection rules and the dividing point decision model. Finally, a case study is given to implement and verify the proposed system design method for D-RMS. The results show that the proposed system design method is effective, which can group parts with more former common operations into the same part family and select appropriate machine types. 相似文献