全文获取类型
收费全文 | 44515篇 |
免费 | 4116篇 |
国内免费 | 2229篇 |
专业分类
电工技术 | 2555篇 |
技术理论 | 2篇 |
综合类 | 3137篇 |
化学工业 | 7300篇 |
金属工艺 | 2729篇 |
机械仪表 | 2677篇 |
建筑科学 | 3350篇 |
矿业工程 | 1069篇 |
能源动力 | 1273篇 |
轻工业 | 3493篇 |
水利工程 | 915篇 |
石油天然气 | 1926篇 |
武器工业 | 378篇 |
无线电 | 4787篇 |
一般工业技术 | 5517篇 |
冶金工业 | 2998篇 |
原子能技术 | 422篇 |
自动化技术 | 6332篇 |
出版年
2024年 | 173篇 |
2023年 | 654篇 |
2022年 | 1251篇 |
2021年 | 1912篇 |
2020年 | 1341篇 |
2019年 | 1153篇 |
2018年 | 1248篇 |
2017年 | 1371篇 |
2016年 | 1216篇 |
2015年 | 1741篇 |
2014年 | 2123篇 |
2013年 | 2488篇 |
2012年 | 2821篇 |
2011年 | 3022篇 |
2010年 | 2687篇 |
2009年 | 2708篇 |
2008年 | 2522篇 |
2007年 | 2392篇 |
2006年 | 2488篇 |
2005年 | 2021篇 |
2004年 | 1523篇 |
2003年 | 1536篇 |
2002年 | 1758篇 |
2001年 | 1525篇 |
2000年 | 1031篇 |
1999年 | 1043篇 |
1998年 | 1061篇 |
1997年 | 830篇 |
1996年 | 706篇 |
1995年 | 555篇 |
1994年 | 407篇 |
1993年 | 364篇 |
1992年 | 233篇 |
1991年 | 148篇 |
1990年 | 145篇 |
1989年 | 117篇 |
1988年 | 92篇 |
1987年 | 67篇 |
1986年 | 33篇 |
1985年 | 45篇 |
1984年 | 36篇 |
1983年 | 27篇 |
1982年 | 29篇 |
1981年 | 46篇 |
1980年 | 33篇 |
1979年 | 17篇 |
1978年 | 14篇 |
1977年 | 28篇 |
1976年 | 32篇 |
1975年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
931.
932.
钟小斐 《宁波工程学院学报》1995,(2)
本文从思想工作应该“康事实做”出发,讨论如何做好大学生德育纪实考评工作,提出了应该“思想到位”以提高认识,“措施到位”以建立规范,“工作到位”以保证落实。 相似文献
933.
The microstructures of MTG YBCO near 2 1 1 phase clusters inside the sample are studied by means of transmission electron microscopy. The results indicate that crystal defects around 2 1 1 phase are closely related to the distance between 2 1 1 particles (d
2 1 1). With the decrease ofd
2 1 1, the twin spacing increases. Simultaneously, the thickness of the twin boundary decreases. Whend
2 1 1 is less than 0.51 m, there are almost no defects between 2 1 1 particles. According to the established crack model, the mechanism of the appearance of a defect-free-zone is explained. The relationship betweend
2 1 1 and Jc is discussed in this paper. 相似文献
934.
P Boscolo M Di Gioacchino M Cervone F Di Giacomo P Bavazzano G Giuliano 《Canadian Metallurgical Quarterly》1995,17(1-6):27-31
Lymphocyte subpopulations were studied in 31 men working in a plant producing plastic materials in relation with control groups of similar age and smoking habit. 8 workers (group A) were exposed to solvents (mainly methylethylketone and dimethylformamide), 8 men (group B) to dust containing particles of calcium carbonate, polyvinylchloride, phtalates, unsaturated oils, paraffin wax, iron oxides, titanium bioxides, barium, zinc and lead and 15 men (group C), working in the same department as group B, were studied after a period of 16 months during which lead chromate was employed in the preparation of colors. The lymphocyte subpopulations were normal in group A, while in B there was a significant increase of HLA-DR + cells (monocytes, B and activated T lymphocytes). In group C, T helper/inducer lymphocytes (mainly CD4(+)-CD45RO- "virgin" lymphocytes), CD19+ B lymphocytes, CD3-HLADR+ and CD3-CD25+ (activated B lymphocytes and monocytes) were significantly reduced without changes of serum IgM, IgG and IgA. Highly significant correlation was found between B lymphocytes (reduced in the workers about 40%) and CD4(+)-CD45R0+ "memory" lymphocytes (reduced about 20%). Moreover, blood lead (correlated with urinary chromium) showed a highly significant negative correlation with the B lymphocytes. This study demonstrates that combined exposure to toxic agents produces specific modifications in the lymphocyte subsets without changes in immunoglobulins and confirms the results of previous researches showing that the exposure to lead or chromate induces reduction of lymphocytes in the peripheral blood. 相似文献
935.
基于TSMC 180 nm工艺设计并流片测试了一款用于高能物理实验的电子读出系统的低噪声、低功耗锁相环芯片。该芯片主要由鉴频鉴相器、电荷泵、环路滤波器、压控振荡器和分频器等子模块组成,在锁相环电荷泵模块中,使用共源共栅电流镜结构精准镜像电流以减小电流失配和用运放钳位电压进一步减小相位噪声。测试结果表明,该锁相环芯片在1.8 V电源电压、输入50 MHz参考时钟条件下,可稳定输出200 MHz的差分时钟信号,时钟均方根抖动为2.26 ps(0.45 mUI),相位噪声在1 MHz频偏处为-105.83 dBc/Hz。芯片整体功耗实测为23.4 mW,锁相环核心功耗为2.02 mW。 相似文献
936.
针对目前复杂交通环境下还存在多目标检测精度和速度不高等问题,以特征金字塔网络(Feature Pyramid Network, FPN)为基础,提出了一种多层融合多目标检测与识别算法,以提高目标检测精度和网络泛化能力。首先,采用ResNet101的五层架构将空间分辨率上采样2倍构建自上而下的特征图,按照元素相加的方式将上采样图和自下而上的特征图合并,并构建一个融合高层语义信息与低层几何信息的特征层;然后,根据BBox回归存在训练样本不平衡问题,选择Efficient IOU Loss损失函数并结合Focal Loss提出一种改进Focal EIOU Loss;最后,充分考虑复杂交通环境下的实际情况,进行人工标注混合数据集进行训练。该模型在KITTI测试集上的平均检测精度和速度比FPN分别提升了2.4%和5 frame/s,在Cityscale测试集上平均检测精度和速度比FPN提升了1.9%和4 frame/s。 相似文献
937.
Jiacheng Yin Na Li Ming Liu Zhigang Li Xuemin Wang Mingren Cheng Ming Zhong Wei Li Yunhua Xu Xian-He Bu 《Advanced functional materials》2023,33(21):2211950
Organic redox-active materials are promising electrode candidates for lithium-ion batteries by virtue of their designable structure and cost-effectiveness. However, their poor electrical conductivity and high solubility in organic electrolytes limit the device's performance and practical applications. Herein, the π-conjugated nitrogen-containing heteroaromatic molecule hexaazatriphenylene (HATN) is strategically embedded with redox-active centers in the skeleton of a Cu-based 2D conductive metal–organic framework (2D c-MOF) to optimize the lithium (Li) storage performance of organic electrodes, which delivers improved specific capacity (763 mAh g−1 at 300 mA g−1), long-term cycling stability (≈90% capacity retention after 600 cycles at 300 mA g−1), and excellent rate performance. The correlation of experimental and computational results confirms that this high Li storage performance derives from the maximum number of active sites (CN sites in the HATN unit and CO sites in the CuO4 unit), favorable electrical conductivity, and efficient mass transfer channels. This strategy of integrating multiple redox-active moieties into the 2D c-MOF opens up a new avenue for the design of high-performance electrode materials. 相似文献
938.
Dovletgeldi Seyitliyev Xixi Qin Manoj K. Jana Svenja M. Janke Xiaowei Zhong Wei You David B. Mitzi Volker Blum Kenan Gundogdu 《Advanced functional materials》2023,33(21):2213021
Electron–phonon interactions play an essential role in charge transport and transfer processes in semiconductors. For most structures, tailoring electron–phonon interactions for specific functionality remains elusive. Here, it is shown that, in hybrid perovskites, coherent phonon modes can be used to manipulate charge transfer. In the 2D double perovskite, (AE2T)2AgBiI8 (AE2T: 5,5“-diylbis(amino-ethyl)-(2,2”-(2)thiophene)), the valence band maximum derived from the [Ag0.5Bi0.5I4]2– framework lies in close proximity to the AE2T-derived HOMO level, thereby forming a type-II heterostructure. During transient absorption spectroscopy, pulsed excitation creates sustained coherent phonon modes, which periodically modulate the associated electronic levels. Thus, the energy offset at the organic–inorganic interface also oscillates periodically, providing a unique opportunity for modulation of interfacial charge transfer. Density-functional theory corroborates the mechanism and identifies specific phonon modes as likely drivers of the coherent charge transfer. These observations are a striking example of how electron–phonon interactions can be used to manipulate fundamentally important charge and energy transfer processes in hybrid perovskites. 相似文献
939.
Xingying Zhang Chen Song Huijia Nong Kaige Xu Xiaozhuo Wu Wen Zhong Malcolm Xing Leyu Wang 《Advanced functional materials》2023,33(32):2300866
A conductive engineered cardiac patch (ECP) can reconstruct the biomimetic regenerative microenvironment of an infarcted myocardium. Direct ink writing (DIW) and 3D printing can produce an ECP with precisely controlled microarchitectures. However, developing a printed ECP with high conductivity and flexibility for gapless attachment to conform to epicardial geometry remains a challenge. Herein, an asymmetrical DIW hydrophobic/hydrophilic membrane using heat-processed graphene oxide (GO) ink is developed. The “Masked spin coating” method is also developed that leads to a microscale GO (hydrophilic)/reduced GO (rGO, hydrophobic) physiological sensor, as well as a macroscale moisture-driven GO/rGO actuator. Depositing mussel-inspired polydopamine (PDA) coating on the one side of the DIW rGO , the ultrathin (approximately 500 nm) PDA-rGO (hydrophilic)/rGO (hydrophobic) microlattice (DrGOM) ECP is bestowed with the flexibility and moisture-responsive actuation that allows gapless attachment to the curved surface of the epicardium. Conformable DrGOM exhibits a promising therapeutic effect on rats' infarcted hearts through conductive microenvironment reconstruction and improved neovascularization. 相似文献
940.
Xueyan Huang Sheng Huang Tianyi Wang Lei Zhong Dongmei Han Min Xiao Shuanjin Wang Yuezhong Meng 《Advanced functional materials》2023,33(27):2300683
Solid-state lithium metal batteries (SSLMBs) are highly desirable for energy storage because of the urgent need for higher energy density and safer batteries. However, it remains a critical challenge for stable cycling of SSLMBs at low temperature. Here, a highly viscoelastic polyether-b-amide (PEO-b-PA) based composite solid-state electrolyte is proposed through a one-pot melt processing without solvent to address this key process. By adjusting the molar ratio of PEO-b-PA to lithium bis(trifluoromethanesulphonyl)imide (ethylene oxide:Li = 6:1) and adding 20 wt.% succinonitrile, fast Li+ transport channel is conducted within the homogeneous polymer electrolyte, which enables its application at ultra-low temperature (−20 to 25 °C). The composite solid-state electrolyte utilizes dynamic hydrogen-bonding domains and ion-conducting domains to achieve a low interfacial charge transfer resistance (<600 Ω) at −20 °C and high ionic conductivity (25 °C, 3.7 × 10−4 S cm−1). As a result, the LiFePO4|Li battery based on composite electrolyte exhibits outstanding electrochemical performance with 81.5% capacity retention after 1200 cycles at −20 °C and high discharge specific capacities of 141.1 mAh g−1 with high loading (16.1 mg cm−2) at 25 °C. Moreover, the solid-state SNCM811|Li cell achieves excellent safety performance under nail penetration test, showing great promise for practical application. 相似文献