全文获取类型
收费全文 | 2038篇 |
免费 | 216篇 |
国内免费 | 55篇 |
专业分类
电工技术 | 109篇 |
综合类 | 160篇 |
化学工业 | 346篇 |
金属工艺 | 125篇 |
机械仪表 | 115篇 |
建筑科学 | 108篇 |
矿业工程 | 65篇 |
能源动力 | 70篇 |
轻工业 | 112篇 |
水利工程 | 30篇 |
石油天然气 | 125篇 |
武器工业 | 23篇 |
无线电 | 187篇 |
一般工业技术 | 308篇 |
冶金工业 | 194篇 |
原子能技术 | 20篇 |
自动化技术 | 212篇 |
出版年
2024年 | 9篇 |
2023年 | 32篇 |
2022年 | 57篇 |
2021年 | 84篇 |
2020年 | 68篇 |
2019年 | 57篇 |
2018年 | 60篇 |
2017年 | 80篇 |
2016年 | 68篇 |
2015年 | 90篇 |
2014年 | 120篇 |
2013年 | 92篇 |
2012年 | 109篇 |
2011年 | 124篇 |
2010年 | 121篇 |
2009年 | 121篇 |
2008年 | 125篇 |
2007年 | 75篇 |
2006年 | 111篇 |
2005年 | 85篇 |
2004年 | 60篇 |
2003年 | 61篇 |
2002年 | 41篇 |
2001年 | 47篇 |
2000年 | 45篇 |
1999年 | 41篇 |
1998年 | 39篇 |
1997年 | 63篇 |
1996年 | 49篇 |
1995年 | 31篇 |
1994年 | 30篇 |
1993年 | 26篇 |
1992年 | 14篇 |
1991年 | 16篇 |
1990年 | 15篇 |
1989年 | 14篇 |
1988年 | 11篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1985年 | 5篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1980年 | 1篇 |
1968年 | 1篇 |
1965年 | 1篇 |
1956年 | 1篇 |
排序方式: 共有2309条查询结果,搜索用时 26 毫秒
981.
Huilong Fei Juncai Dong Chengzhang Wan Zipeng Zhao Xiang Xu Zhaoyang Lin Yiliu Wang Haotian Liu Ketao Zang Jun Luo Shenglong Zhao Wei Hu Wensheng Yan Imran Shakir Yu Huang Xiangfeng Duan 《Advanced materials (Deerfield Beach, Fla.)》2018,30(35)
Graphene‐supported single atomic metals (G‐SAMs) have recently attracted considerable research interest for their intriguing catalytic, electronic, and magnetic properties. The development of effective synthetic methodologies toward G‐SAMs with monodispersed metal atoms is vital for exploring their fundamental properties and potential applications. A convenient, rapid, and general strategy to synthesize a series of monodispersed atomic transition metals (for example, Co, Ni, Cu) embedded in nitrogen‐doped graphene by two‐second microwave (MW) heating the mixture of amine‐functionalized graphene oxide and metal salts is reported here. The MW heating is able to simultaneously induce the reduction of graphene oxide, the doping of nitrogen, and the incorporation of metal atoms into the graphene lattices in one simple step. The rapid MW process minimizes metal diffusion and aggregation to ensure exclusive single metal atom dispersion in graphene lattices. Electrochemical studies demonstrate that graphene‐supported Co atoms can function as highly active electrocatalysts toward the hydrogen evolution reaction. This MW‐assisted method provides a rapid and efficient avenue to supported metal atoms for wide ranges of applications. 相似文献
982.
Xiaosheng Tang Weiwei Chen Zhengzheng Liu Juan Du Zhiqiang Yao Yi Huang Cheng Chen Zhaoqi Yang Tongchao Shi Wei Hu Zhigang Zang Yu Chen Yuxin Leng 《Small (Weinheim an der Bergstrasse, Germany)》2019,15(19)
All‐inorganic semiconductor perovskite quantum dots (QDs) with outstanding optoelectronic properties have already been extensively investigated and implemented in various applications. However, great challenges exist for the fabrication of nanodevices including toxicity, fast anion‐exchange reactions, and unsatisfactory stability. Here, the ultrathin, core–shell structured SiO2 coated Mn2+ doped CsPbX3 (X = Br, Cl) QDs are prepared via one facile reverse microemulsion method at room temperature. By incorporation of a multibranched capping ligand of trioctylphosphine oxide, it is found that the breakage of the CsPbMnX3 core QDs contributed from the hydrolysis of silane could be effectively blocked. The thickness of silica shell can be well‐controlled within 2 nm, which gives the CsPbMnX3@SiO2 QDs a high quantum yield of 50.5% and improves thermostability and water resistance. Moreover, the mixture of CsPbBr3 QDs with green emission and CsPbMnX3@SiO2 QDs with yellow emission presents no ion exchange effect and provides white light emission. As a result, a white light‐emitting diode (LED) is successfully prepared by the combination of a blue on‐chip LED device and the above perovskite mixture. The as‐prepared white LED displays a high luminous efficiency of 68.4 lm W?1 and a high color‐rendering index of Ra = 91, demonstrating their broad future applications in solid‐state lighting fields. 相似文献
983.
Chemo/Photoacoustic Dual Therapy with mRNA‐Triggered DOX Release and Photoinduced Shockwave Based on a DNA‐Gold Nanoplatform 下载免费PDF全文
Yundong Zang Yanchun Wei Yujiao Shi Qun Chen Da Xing 《Small (Weinheim an der Bergstrasse, Germany)》2016,12(6):756-769
A multifunctional nanoparticle based on gold nanorod (GNR), utilizing mRNA triggered chemo‐drug release and near‐infrared photoacoustic effect, is developed for a combined chemo‐photoacoustic therapy. The constructed nanoparticle (GNR‐DNA/FA:DOX) comprises three functional components: (i) GNR as the drug delivery platform and photoacoustic effect enhancer; (ii) toehold‐possessed DNA dressed on the GNR to load doxorubicin (DOX) to implement a tumor cell specific chemotherapy; and (iii) folate acid (FA) modified on GNR to guide the nanoparticle to target tumor cells. The results show that, upon an effective and specific delivery of the nanoparticles to the tumor cells with overexpressed folate receptors, the cytotoxic DOX loaded on the GNR‐DNA nanoplatform can be released through DNA displacement reaction in melanoma‐associated antigen gene mRNA expressed cells. With 808 nm pulse laser irradiation, the photoacoustic effect of the GNR leads to a direct physical damage to the cells. The combined treatment of the two modalities can effectively destroy tumor cells and eradicate the tumors with two distinctively different and supplementing mechanisms. With the nanoparticle, photoacoustic imaging is successfully performed in situ to monitor the drug distribution and tumor morphology for therapeutical guidance. With further in‐depth investigation, the proposed nanoparticle may provide an effective and safe alternative cancer treatment modality. 相似文献
984.
985.
986.
Blockchain is becoming popular as a distributed and reliable ledger which allows distrustful parties to transact safely without trusting third parties. Emerging blockchain systems like Ethereum support smart contracts where miners can run arbitrary user-defined programs. However, one of the biggest concerns about the blockchain and the smart contract is privacy, since all the transactions on the chain are exposed to the public. In this paper, we present ShadowEth, a system that leverages hardware enclave to ensure the confidentiality of smart contracts while keeping the integrity and availability based on existing public blockchains like Ethereum. ShadowEth establishes a confidential and secure platform protected by trusted execution environment (TEE) off the public blockchain for the execution and storage of private contracts. It only puts the process of verification on the blockchain. We provide a design of our system including a protocol of the cryptographic communication and verification and show the applicability and feasibility of ShadowEth by various case studies. We implement a prototype using the Intel SGX on the Ethereum network and analyze the security and availability of the system. 相似文献
987.
This paper investigates finite‐time adaptive robust control problem for a general class of nonlinear time‐delay systems with uncertain and external disturbance via the Lyapunov‐Krasovskii (L‐K) method and presents some delay‐independent and delay‐dependent results on the issue. First, by applying the orthogonal decomposition method, this paper presents an equivalent form. Based on which, we study the finite‐time adaptive robust control problem for the systems by constructing a specific L‐K functional and designing a suitable controller. Different from existing works, this paper studies finite‐time adaptive robust control problem for general nonlinear delay system and presents a delay‐dependent sufficient condition on the problem. Finally, an illustrative example is given to show the effectiveness of the result in this paper. 相似文献
988.
针对随机值冲击噪声污染图像的恢复问题,研究了冲击噪声环境下的非局部平均滤波模型,并在模糊权重非局部平均滤波算法的基础上加以改进,解决了原算法在低噪声比率下恢复性能欠佳以及算法时耗过高的问题。改进之处如下:第一,提出了一种信赖度参数设置准则,并在该准则指导下设置了新的信赖度门限参数;第二,根据冲击噪声模型特点重新规划了滤波策略,提升了算法的运算效率。大量实验数据证明,所提算法无论在低噪声比率还是高噪声比率下均能有效去除冲击噪声,尤其对于纹理性较强的图像有显著的去噪效果。同时,所提算法拥有较高运算效率,实用性得以提高。 相似文献
989.
目的 为了解决从曲线库(轮廓线集合)中筛选出与期望曲线相匹配的相似曲线段问题,研究基于Kabsch算法的NURBS(非均匀有理B样条)曲线优化匹配组合方法。方法 首先提出一种基于Kabsch算法的曲线相似性判断方法,针对两条NURBS曲线上相同个数点阵,经最优旋转和平移变换得到其最小均方根偏差,进而依据基于最小均方根偏差和相似度指标判断曲线相似性;在此基础上,提出一种类似二分查找法的曲线优化匹配组合方法,对于给定相似度和最小搜索步长,通过曲线分割和相似性判断得到期望曲线分割段数最少的相似组合曲线。结果 给定一条期望的3D曲线,在相似度为0.025和最小搜索步长为0.05情况下,采用所提方法从包含4条3D曲线的曲线库中依次筛选出10段基元构建相似组合曲线。结论 提出了一种新的NURBS曲线优化匹配组合方法,实验结果表明,对不同期望曲线能高效稳定构建相对应的相似组合曲线,适用于类似碎片拼接重构问题。 相似文献
990.
Yufang Xie Jinyan Cai Yishang Wu Yipeng Zang Xusheng Zheng Jian Ye Peixin Cui Shuwen Niu Yun Liu Junfa Zhu Xiaojing Liu Gongming Wang Yitai Qian 《Advanced materials (Deerfield Beach, Fla.)》2019,31(16)
Although it is commonly believed that the water‐dissociation‐related Volmer process is the rate‐limiting step for alkaline hydrogen evolution reaction (HER) on Pt‐based catalysts, the underlying essence, particularly on the atomic scale, still remains unclear. Herein, it is revealed that the sluggish water‐dissociation behavior probably stems from unfavorable orbital orientation and the kinetic issue is successfully resolved via N‐induced orbital tuning. Impressively, N modified Pt–Ni nanowires deliver an ultralow overpotential of 13 mV at 10 mA cm?2, which represents a new benchmark for alkaline HER catalysis. Fine‐structural characterization and density functional theory analysis illustrate that the introduced nitrogen can uniquely modulate the electron densities around the Ni sites, and further create empty dz2 orbitals with superior orientation for water adsorption and activation. More importantly, it is demonstrated that N‐induced orbital modulation can generally boost the alkaline HER activities of Pt–Co, Pt–Ni, and Pt–Cu, offering a new perspective for the design of HER catalysts and beyond. 相似文献