全文获取类型
收费全文 | 62785篇 |
免费 | 6699篇 |
国内免费 | 4508篇 |
专业分类
电工技术 | 5094篇 |
技术理论 | 1篇 |
综合类 | 5843篇 |
化学工业 | 9414篇 |
金属工艺 | 4100篇 |
机械仪表 | 4484篇 |
建筑科学 | 4823篇 |
矿业工程 | 2334篇 |
能源动力 | 1766篇 |
轻工业 | 5746篇 |
水利工程 | 1796篇 |
石油天然气 | 2714篇 |
武器工业 | 739篇 |
无线电 | 6860篇 |
一般工业技术 | 6277篇 |
冶金工业 | 2229篇 |
原子能技术 | 1022篇 |
自动化技术 | 8750篇 |
出版年
2024年 | 269篇 |
2023年 | 975篇 |
2022年 | 2249篇 |
2021年 | 3027篇 |
2020年 | 2194篇 |
2019年 | 1754篇 |
2018年 | 1826篇 |
2017年 | 1895篇 |
2016年 | 1792篇 |
2015年 | 2727篇 |
2014年 | 3494篇 |
2013年 | 4030篇 |
2012年 | 4894篇 |
2011年 | 5279篇 |
2010年 | 4671篇 |
2009年 | 4605篇 |
2008年 | 4531篇 |
2007年 | 4467篇 |
2006年 | 3966篇 |
2005年 | 3108篇 |
2004年 | 2356篇 |
2003年 | 1800篇 |
2002年 | 1942篇 |
2001年 | 1658篇 |
2000年 | 1295篇 |
1999年 | 845篇 |
1998年 | 468篇 |
1997年 | 361篇 |
1996年 | 332篇 |
1995年 | 281篇 |
1994年 | 228篇 |
1993年 | 168篇 |
1992年 | 94篇 |
1991年 | 75篇 |
1990年 | 72篇 |
1989年 | 72篇 |
1988年 | 46篇 |
1987年 | 33篇 |
1986年 | 23篇 |
1985年 | 15篇 |
1984年 | 10篇 |
1983年 | 12篇 |
1982年 | 7篇 |
1981年 | 7篇 |
1980年 | 7篇 |
1979年 | 14篇 |
1960年 | 1篇 |
1959年 | 6篇 |
1951年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Chenchen Zhou Jia Man Haibo Yu He Xia Luming Man Bin Qi Jianfeng Li 《Ceramics International》2021,47(8):10866-10872
Ceramic microparticles have great potentials in various fields such as materials engineering, biotechnology, microelectromechanical systems, etc. Morphology of the microparticle performs an important role on their application. To date, it remains difficult to find an effective and controllable way for fabricating nonspherical ceramic microparticles with 3D features. This work demonstrates a method that combines UV light lithography and single emulsion opaque-droplet-templated microfluidic molding to prepare the crescent-shaped ceramic microparticles. By tailoring the intensity of UV light and flow rate of fluid, the shapes of microparticles are accordingly tuned. Therefore, varieties of crescent-shaped microparticles and their variations have been fabricated. After sintering, the crescent-shaped alumina ceramic microparticles were obtained. Benefitting from the light absorption and scattering behavior of most ceramic nanoparticles, this system can serve as a general platform to produce crescent-shaped microparticles made from different materials, and hold great potentials for applications in microrobotics, structural materials in MEMS, and biotechnology. 相似文献
2.
以智能反射面(intelligent reflecting surface,IRS)辅助的无线携能通信(simultaneous wireless information and power transfer,SWIPT)系统为背景,研究了该系统中基于能效优先的多天线发送端有源波束成形与IRS无源波束成形联合设计与优化方法。以最大化接收端的最小能效为优化目标,构造在发送端功率、接收端能量阈值、IRS相移等多约束下的非线性优化问题,用交替方向乘子法(alternating direction method of multipliers,ADMM)求解。采用Dinkelbach算法转化目标函数,通过奇异值分解(singular value decomposition,SVD)和半定松弛(semi-definite relaxation,SDR)得到发送端有源波束成形向量。采用SDR得到IRS相移矩阵与反射波束成形向量。结果表明,该系统显著降低了系统能量收集(energy harvesting,EH)接收端的能量阈值。当系统总电路功耗为?15 dBm时,所提方案的用户能效为300 KB/J。当IRS反射阵源数与发送天线数均为最大值时,系统可达最大能效。 相似文献
3.
Jia Dai Xiang Cheng Xiaofeng Li Zhisheng Wang Yufeng Wang Jing Zheng Jun Liu Jiawei Chen Changjin Wu Jinyao Tang 《Advanced functional materials》2021,31(48):2106204
Synthetic active matters are perfect model systems for non-equilibrium thermodynamics and of great potential for novel biomedical and environmental applications. However, most applications are limited by the complicated and low-yield preparation, while a scalable synthesis for highly functional microswimmers is highly desired. In this paper, an all-solution synthesis method is developed where the gold-loaded titania-silica nanotree can be produced as a multi-functional self-propulsion microswimmer. By applying light, heat, and electric field, the Janus nanotree demonstrated multi-mode self-propulsion, including photochemical self-electrophoresis by UV and visible light radiation, thermophoresis by near-infrared light radiation, and induced-charge electrophoresis under AC electric field. Due to the scalable synthesis, the Janus nanotree is further demonstrated as a high-efficiency, low-cost, active adsorbent for water decontamination, where the toxic mercury ions can be reclaimed with enhanced efficiency. 相似文献
4.
以蚕丝蛋白为模板,在相对温和的条件下通过生物矿化的手段形成具有特殊形貌的α-GaOOH颗粒,并通过在不同温度下煅烧α-GaOOH得到α-Ga2O3和β-Ga2O3.采用扫描电镜(SEM)、透射电镜(TEM)、X射线衍射仪(XRD)和荧光分光光度计(PL)等手段研究了丝素蛋白多肽和矿化时间对颗粒的影响,对其生物矿化机理进行了初步探讨.结果表明,所制备的β-Ga2O3具有优良的发光特性,丝素蛋白多肽模板以无定形的结构与产物结合在一起,并且经过高温烧结后仍以碳膜的形式包覆在材料的表面.这种碳膜结构对于提高材料的生物学性能起着重要的作用. 相似文献
5.
6.
7.
The slight-alkalization of generator internal cooling water (GICW) is widely used to inhibit the corrosion of hollow copper conductor and thereby ensure the safe operation of the generator. CO2 inleakage is increasingly identified as a potential security risk for GICW system. In this paper, the influence of CO2 inleakage on the slight-alkalization of GICW was theoretically discussed. Based on the equilibriums of the CO2-NaOH-H2O system, CO2 inleakage saturation was derived to quantify the amount of the dissolved CO2 in GICW. This parameter can be directly calculated with the measured conductivity and the [Na+] of GICW. The influence of CO2 inleakage on the slight-alkalization conditioning of GICW and the measurement of its water quality parameters were then analyzed. The more severe the inleakage, the narrower the water quality operation ranges of GICW, resulting in the more difficult the slight-alkalization conditioning of GICW. The temperature calibrations of the conductivity and the pH value of GICW show non-linear correlations with the amount of CO2 inleakage and the NaOH dosage. This study provides insights into the influence of CO2 inleakage on the slight-alkalization of GICW, which can serve as the theoretical basis for the actual slight-alkalization when CO2 inleakage occurs. 相似文献
9.
10.
Nitrile rubber (NBR) blends with excellent performance have always been a hot research topic in petroleum field. Due to the excellent performance and compatibility of polyamide 6 (PA6), it provides an opportunity for the preparation of high-performance NBR/PA6 blends. In this article, NBR/PA6 blends were prepared by the three-step molding process. Experimentally, it was found that PA6 has a prominent reinforcement effect in NBR matrix. The variation of this mechanical property was investigated from different aspects of the crystal structure, crystallinities, phase morphology, and so on. It can be cleared that the formation of fibrous structure of PA6 phase is the main factor for reinforcement of the polymer blends. Meanwhile, the formation mechanism of the special phase structure induced by the three-step process is deeply expounded and its structural evolution schematic is established. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47472. 相似文献