全文获取类型
收费全文 | 2281篇 |
免费 | 137篇 |
国内免费 | 10篇 |
专业分类
电工技术 | 38篇 |
综合类 | 5篇 |
化学工业 | 460篇 |
金属工艺 | 47篇 |
机械仪表 | 55篇 |
建筑科学 | 58篇 |
矿业工程 | 2篇 |
能源动力 | 116篇 |
轻工业 | 189篇 |
水利工程 | 12篇 |
石油天然气 | 40篇 |
武器工业 | 1篇 |
无线电 | 310篇 |
一般工业技术 | 474篇 |
冶金工业 | 216篇 |
原子能技术 | 18篇 |
自动化技术 | 387篇 |
出版年
2024年 | 5篇 |
2023年 | 48篇 |
2022年 | 79篇 |
2021年 | 111篇 |
2020年 | 77篇 |
2019年 | 69篇 |
2018年 | 103篇 |
2017年 | 94篇 |
2016年 | 101篇 |
2015年 | 60篇 |
2014年 | 83篇 |
2013年 | 161篇 |
2012年 | 116篇 |
2011年 | 159篇 |
2010年 | 81篇 |
2009年 | 109篇 |
2008年 | 108篇 |
2007年 | 110篇 |
2006年 | 83篇 |
2005年 | 58篇 |
2004年 | 55篇 |
2003年 | 50篇 |
2002年 | 27篇 |
2001年 | 22篇 |
2000年 | 37篇 |
1999年 | 38篇 |
1998年 | 39篇 |
1997年 | 41篇 |
1996年 | 23篇 |
1995年 | 29篇 |
1994年 | 23篇 |
1993年 | 25篇 |
1992年 | 16篇 |
1991年 | 16篇 |
1990年 | 14篇 |
1989年 | 15篇 |
1988年 | 16篇 |
1987年 | 16篇 |
1986年 | 10篇 |
1985年 | 13篇 |
1984年 | 15篇 |
1983年 | 15篇 |
1982年 | 13篇 |
1981年 | 14篇 |
1980年 | 6篇 |
1978年 | 4篇 |
1977年 | 4篇 |
1976年 | 3篇 |
1974年 | 3篇 |
1967年 | 2篇 |
排序方式: 共有2428条查询结果,搜索用时 10 毫秒
51.
52.
瞬态包络分析算法是一种快速有效的仿真算法,被广泛应用于RF电路仿真中,文章主要研究了基于打靶法的瞬态包络分析算法-采样包络算法,并给出了该算法的具体流程和计算机实现结果。 相似文献
53.
Meng Qiu Yanhong Duo Weiyuan Liang Yunlong Yang Bin Zhang Zhongjian Xie Xiaoli Yang Guiqing Wang Ni Xie Guohui Nie Omar A. Alhartomy Ahmed A. ALGhamdi Swelm Wageh Yihai Cao Han Zhang 《Advanced functional materials》2021,31(42):2104607
Most anticancer drugs with broad toxicities are systematically administrated to cancer patients and their distribution in tumors is extremely low owing to hypoxia, which compromises the therapeutic efficacies of these cancer drugs. Consequently, a preponderant proportion of cancer drugs is distributed in off-target-healthy tissues, which often causes severe adverse effects. Precision cancer therapy without overdosing patients with drugs remains one of the most challenging issues in cancer therapy. Here, a novel concept of nanopoxia is presented, which is a tumor-hypoxia-based photodynamic nanoplatform for the release of therapeutic agents to achieve precision cancer therapy. Under tumor hypoxia, exposure of tumors to laser irradiation induces the fracture of polymer outer shell and produces anticancer reactive oxygen species, and switches 2D antimonene (Sb) nanomaterials to cytotoxic trivalent antimony to synergistically kill tumors. In preclinical cancer models, delivery of Sb nanomaterials to mice virtually ablates tumor growth without producing any detectable adverse effects. Mechanistically, the tumor hypoxia-triggered generation of trivalent antimony displays direct damaging effects on cancer cells and suppression of tumor angiogenesis. Together, the study provides a proof-of-concept of hypoxia-based precision cancer therapy by developing a novel nanoplatform that offers multifarious mechanisms of cancer eradication. 相似文献
54.
Omar E. Abdel-Salam Madiha A. Shoeib Hagar Ashour Elkilany 《Egyptian Journal of Petroleum》2018,27(4):497-504
The properties of hard anodizing layers formed on 2014 Al alloy in sulphuric acid electrolyte containing sodium lignin sulphonate were investigated. The corrosion behavior of 2014 Al alloy has been studied using potentiodynamic polarization technique. Anodic layers morphology and composition were examined by scanning electron microscope, energy dispersion X-ray (EDX), X-ray diffraction (XRD) and Fourier infrared spectroscopy (FTIR). The results showed that the corrosion resistance has been enhanced after hard anodizing of 2014 Al alloy. Addition of lignin sulphonate to the sulphuric acid electrolyte significantly improved the corrosion resistance of the anodized 2014 aluminum alloy by adsorption on copper-intermetallic phases. Adsorption of sodium lignin sulphonate on oxide surface has been confirmed by SEM, EDX, and FTIR. Phenolic and carboxylic groups in sodium lignin sulphonate are functional groups, which are responsible of complex formation on oxide surface. The morphology of the hard anodizing layer is non-homogenous due to the high copper content of 2014 Al alloy. Addition of sodium lignin sulphonate resulted in the formation of anodic layers with more homogeneity and fewer cracks. 相似文献
55.
The authors consider a multirate code-division multiple acess system, in which all users have the same chip rate and vary their data rate by adjusting the processing gain. The receivers are assumed to be implemented using conventional matched filters, whose performance is sensitive to the received power levels. The authors' goal is to maximize the total system throughput by means of power control. A game theoretic approach is adopted. It is shown that for a certain type of pricing function, a unique Nash equilibrium solution exists and it possesses nice global properties. For example, it can be shown that for the optimal solution a high-rate connection should maintain a higher energy per bit than low-rate ones. The asymptotic spectral efficiency is also derived. 相似文献
56.
Chi Wan Sung Wing Shing Wong 《Vehicular Technology, IEEE Transactions on》1997,46(3):676-686
Generally, the channel-assignment problem (CAP) for mobile cellular systems is solved by graph-coloring algorithms. These algorithms, though sometimes can yield an optimal solution, do not supply any information on whether an optimal solution has been found or bow far away it is from the optimum. In view of these undesirable features, two relevant results are presented. First, a lower bound for the minimum number of channels required to satisfy a given call-traffic demand is derived. This lower bound is tighter than the existing ones under certain conditions and can be used as a supplement for other approximate algorithms. Second, we propose an efficient heuristic algorithm to solve this problem. Although the CAP is nondeterministic polynomial (NP) complete in general, our algorithm provides an optimal solution for a special class of network topologies. For the general case, promising results are obtained, and numerical examples show that our algorithm has a better performance than many existing algorithms 相似文献
57.
Li Xingjun Shao Zhiwei Cheng Hongping Bayan Omar Mohammed 《International Journal of Communication Systems》2020,33(8)
Cloud computing provides high accessibility, scalability, and flexibility in the era of computing for different practical applications. Internet of things (IoT) is a new technology that connects the devices and things to provide user required services. Due to data and information upsurge on IoT, cloud computing is usually used for managing these data, which is known as cloud‐based IoT. Due to the high volume of requirements, service diversity is one of the critical challenges in cloud‐based IoT. Since the load balancing issue is one of the NP‐hard problems in heterogeneous environments, this article provides a new method for response time reduction using a well‐known grey wolf optimization algorithm. In this paper, we supposed that the response time is the same as the execution time of all the tasks that this parameter must be minimized. The way is determining the status of virtual machines based on the current load. Then the tasks will be removed from the machine with the additional load depending on the condition of the virtual machine and will be transferred to the appropriate virtual machine, which is the criterion for assigning the task to the virtual machine based on the least distance. The results of the CloudSim simulation environment showed that the response time is developed in compared to the HBB‐LB and EBCA‐LB algorithm. Also, the load imbalancing degree is improved in comparison to TSLBACO and HJSA. 相似文献
58.
Jesse R. Manders Sai‐Wing Tsang Michael J. Hartel Tzung‐Han Lai Song Chen Chad M. Amb John R. Reynolds Franky So 《Advanced functional materials》2013,23(23):2993-3001
The detailed characterization of solution‐derived nickel (II) oxide (NiO) hole‐transporting layer (HTL) films and their application in high efficiency organic photovoltaic (OPV) cells is reported. The NiO precursor solution is examined in situ to determine the chemical species present. Coordination complexes of monoethanolamine (MEA) with Ni in ethanol thermally decompose to form non‐stoichiometric NiO. Specifically, the [Ni(MEA)2(OAc)]+ ion is found to be the most prevalent species in the precursor solution. The defect‐induced Ni3+ ion, which is present in non‐stoichiometric NiO and signifies the p‐type conduction of NiO, as well as the dipolar nickel oxyhydroxide (NiOOH) species are confirmed using X‐ray photoelectron spectroscopy. Bulk heterojunction (BHJ) solar cells with a polymer/fullerene photoactive layer blend composed of poly‐dithienogermole‐thienopyrrolodione (pDTG‐TPD) and [6,6]‐phenyl‐C71‐butyric acid methyl ester (PC71BM) are fabricated using these solution‐processed NiO films. The resulting devices show an average power conversion efficiency (PCE) of 7.8%, which is a 15% improvement over devices utilizing a poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) HTL. The enhancement is due to the optical resonance in the solar cell and the hydrophobicity of NiO, which promotes a more homogeneous donor/acceptor morphology in the active layer at the NiO/BHJ interface. Finally, devices incorporating NiO as a HTL are more stable in air than devices using PEDOT:PSS. 相似文献
59.
El-Moursy Ali A. Sibai Fadi N. Rehman Jahanzeb Gouda Omar M. Gaber Abdelrahman T. Khedr Ahmed M. 《Wireless Personal Communications》2022,124(2):1525-1555
Wireless Personal Communications - The development of Smart Home Controllers has seen rapid growth in recent years, especially for smart devices, that can utilize the Internet of Things (IoT).... 相似文献
60.
The purpose of this paper is to evaluate theoretically and experimentally the transient electric field in anemp simulator. Using a time domain analysis, the mechanism of the field deformation can be analysed and consequently modifications can be introduced in the conception of new simulators (for example: rhombic simulator). 相似文献