全文获取类型
收费全文 | 36816篇 |
免费 | 2756篇 |
国内免费 | 2003篇 |
专业分类
电工技术 | 1282篇 |
技术理论 | 1篇 |
综合类 | 1988篇 |
化学工业 | 12395篇 |
金属工艺 | 3659篇 |
机械仪表 | 1017篇 |
建筑科学 | 2999篇 |
矿业工程 | 506篇 |
能源动力 | 1121篇 |
轻工业 | 1637篇 |
水利工程 | 99篇 |
石油天然气 | 1266篇 |
武器工业 | 317篇 |
无线电 | 3317篇 |
一般工业技术 | 5322篇 |
冶金工业 | 1449篇 |
原子能技术 | 675篇 |
自动化技术 | 2525篇 |
出版年
2024年 | 391篇 |
2023年 | 646篇 |
2022年 | 1245篇 |
2021年 | 1245篇 |
2020年 | 1056篇 |
2019年 | 889篇 |
2018年 | 760篇 |
2017年 | 1071篇 |
2016年 | 1296篇 |
2015年 | 1252篇 |
2014年 | 1682篇 |
2013年 | 1892篇 |
2012年 | 2137篇 |
2011年 | 2737篇 |
2010年 | 1996篇 |
2009年 | 2464篇 |
2008年 | 1916篇 |
2007年 | 2378篇 |
2006年 | 2205篇 |
2005年 | 1764篇 |
2004年 | 1473篇 |
2003年 | 1479篇 |
2002年 | 1203篇 |
2001年 | 932篇 |
2000年 | 849篇 |
1999年 | 686篇 |
1998年 | 527篇 |
1997年 | 376篇 |
1996年 | 340篇 |
1995年 | 285篇 |
1994年 | 258篇 |
1993年 | 228篇 |
1992年 | 204篇 |
1991年 | 175篇 |
1990年 | 150篇 |
1989年 | 116篇 |
1988年 | 92篇 |
1987年 | 94篇 |
1986年 | 107篇 |
1985年 | 103篇 |
1984年 | 90篇 |
1983年 | 76篇 |
1982年 | 76篇 |
1981年 | 85篇 |
1980年 | 77篇 |
1978年 | 72篇 |
1977年 | 73篇 |
1976年 | 88篇 |
1975年 | 86篇 |
1974年 | 70篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
①C值k值统计。②C极平差等等因素对Δ计程的影响。③MU评定。④Uk=2≮0.3MPE半区间。⑤分析MPE。⑥公路法MPE±2%。⑦滚筒法MPE±3%。 相似文献
992.
ABSTRACTThis paper presents investigations to create a structural supercapacitor with activated carbon fabric electrodes and a solid composite electrolyte, consisting of organic liquid electrolyte 1?M TEABF4 in propylene carbonate and an epoxy matrix where different compositions were considered of 1:2, 1:1 and 2:1 w/w epoxy:liquid electrolyte. Vacuum-assisted resin transfer moulding was used for the impregnation of the electrolyte mixture into the electrochemical double layer capacitor (EDLC) assembly. The best electrochemical performance was exhibited by the 1:2 w/w epoxy: liquid electrolyte ratio, with a cell equivalent-in-series resistance of 160?Ω?cm2 and a maximum electrode-specific capacitance of 101.6?mF?g?1 while the flexural modulus and strength were 0.3?GPa and 29.1?MPa, respectively, indicating a solid EDLC device. 相似文献
993.
针对目前酯化工艺过程中存在的环境污染问题,以丙酸正丁酯催化合成为例,对酯化过程清洁生产工艺中固体酸催化剂的制备进行了研究.制备了 SO_4~(2-)/TiO_2固体超强酸催化剂,讨论了各种制备条件对该催化剂的丙酸正丁酯合成催化活性的影响,采用 TG/DTA、FTIR、XRD 等仪器分析手段对催化剂结构进行了表征,实验结果表明,SO_4~(2-)/TiO_2固体超强酸催化剂具有很好的催化活性和选择性,且无腐蚀、反应时间短、后处理简单、重复使用性好. 相似文献
994.
We propose a method for automatically copying facial motion from one 3D face model to another, while preserving the compliance of the motion to the MPEG-4 Face and Body Animation (FBA) standard. Despite the enormous progress in the field of Facial Animation, producing a new animatable face from scratch is still a tremendous task for an artist. Although many methods exist to animate a face automatically based on procedural methods, these methods still need to be initialized by defining facial regions or similar, and they lack flexibility because the artist can only obtain the facial motion that a particular algorithm offers. Therefore a very common approach is interpolation between key facial expressions, usually called morph targets, containing either speech elements (visemes) or emotional expressions. Following the same approach, the MPEG-4 Facial Animation specification offers a method for interpolation of facial motion from key positions, called Facial Animation Tables, which are essentially morph targets corresponding to all possible motions specified in MPEG-4. The problem of this approach is that the artist needs to create a new set of morph targets for each new face model. In case of MPEG-4 there are 86 morph targets, which is a lot of work to create manually. Our method solves this problem by cloning the morph targets, i.e. by automatically copying the motion of vertices, as well as geometry transforms, from source face to target face while maintaining the regional correspondences and the correct scale of motion. It requires the user only to identify a subset of the MPEG-4 Feature Points in the source and target faces. The scale of the movement is normalized with respect to MPEG-4 normalization units (FAPUs), meaning that the MPEG-4 FBA compliance of the copied motion is preserved. Our method is therefore suitable not only for cloning of free facial expressions, but also of MPEG-4 compatible facial motion, in particular the Facial Animation Tables. We believe that Facial Motion Cloning offers dramatic time saving to artists producing morph targets for facial animation or MPEG-4 Facial Animation Tables. 相似文献
995.
以 3-三氟甲基 - 4-氨基 - 5 -巯基 - 1 ,2 ,4-三唑为原料 ,分别与 2 - ,3- ,4-吡啶甲酸及α-萘乙酸在 POCl3催化下反应 ,制得 4种新的 3-三氟甲基 - 6-取代均三唑并 [3,4- b]- 1 ,3,4-噻二唑( 3a~ 3d) ,并利用 EA,IR,1H NMR等确定了其结构 相似文献
996.
J. Sabadell C. Aldea S. Celma P. A. Martínez 《Analog Integrated Circuits and Signal Processing》2001,28(1):35-42
In this paper, a continuous-time 4th order Butterworth low-pass filter based on current-mode processing is presented for applications over the video frequency range. A new type of integrator in which both voltage and currents may be integrated is presented and used as the main active block. The filter has been implemented using a very low-cost 2.4 m CMOS process (Mietec). The whole circuit occupies 2.8 mm2 and consumes 19 mW from a ±1.5 V supply. Experimental results are given for a 4.5 MHz to 12 MHz tunable low-pass filter with 58 dB of dynamic range at 10 MHz. 相似文献
997.
Glutathione Mediated Size‐Tunable UCNPs‐Pt(IV)‐ZnFe2O4 Nanocomposite for Multiple Bioimaging Guided Synergetic Therapy 下载免费PDF全文
Huiting Bi Yunlu Dai Piaoping Yang Jiating Xu Dan Yang Shili Gai Fei He Bin Liu Chongna Zhong Guanghui An Jun Lin 《Small (Weinheim an der Bergstrasse, Germany)》2018,14(13)
Here a multifunctional nanoplatform (upconversion nanoparticles (UCNPs)‐platinum(IV) (Pt(IV))?ZnFe2O4, denoted as UCPZ) is designed for collaborative cancer treatment, including photodynamic therapy (PDT), chemotherapy, and Fenton reaction. In the system, the UCNPs triggered by near‐infrared light can convert low energy photons to high energy ones, which act as the UV–vis source to simultaneously mediate the PDT effect and Fenton's reaction of ZnFe2O4 nanoparticles. Meanwhile, the Pt(IV) prodrugs can be reduced to high virulent Pt(II) by glutathione in the cancer cells, which can bond to DNA and inhibit the copy of DNA. The synergistic therapeutic effect is verified in vitro and in vivo results. The cleavage of Pt(IV) from UCNPs during the reduction process can shift the larger UCPZ nanoparticles (NPs) to the smaller ones, which promotes the enhanced permeability and retention (EPR) and deep tumor penetration. In addition, due to the inherent upconversion luminescence (UCL) and the doped Yb3+ and Fe3+ in UCPZ, this system can serve as a multimodality bioimaging contrast agent, covering UCL, X‐ray computed tomography, magnetic resonance imaging, and photoacoustic. A smart all‐in‐one imaging‐guided diagnosis and treatment system is realized, which should have a potential value in the treatment of tumor. 相似文献
998.
Compared with other flexible energy‐storage devices, the design and construction of the compressible energy‐storage devices face more difficulty because they must accommodate large strain and shape deformations. In the present work, CoNi2S4 nanoparticles/3D porous carbon nanotube (CNT) sponge cathode with highly compressible property and excellent capacitance is prepared by electrodepositing CoNi2S4 on CNT sponge, in which CoNi2S4 nanoparticles with size among 10–15 nm are uniformly anchored on CNT, causing the cathode to show a high compression property and gives high specific capacitance of 1530 F g−1. Meanwhile, Fe2O3/CNT sponge anode with specific capacitance of 460 F g−1 in a prolonged voltage window is also prepared by electrodepositing Fe2O3 nanosheets on CNT sponge. An asymmetric supercapacitor (CoNi2S4/CNT//Fe2O3/CNT) is assembled by using CoNi2S4/CNT sponge as positive electrode and Fe2O3/CNT sponge as negative electrode in 2 m KOH solution. It exhibits excellent energy density of up to 50 Wh kg−1 at a power density of 847 W kg−1 and excellent cycling stability at high compression. Even at a strain of 85%, about 75% of the initial capacitance is retained after 10 000 consecutive cycles. The CoNi2S4/CNT//Fe2O3/CNT device is a promising candidate for flexible energy devices due to its excellent compressibility and high energy density. 相似文献
999.
Experimental investigation on machinability of DMLS Ti6Al4V under dry drilling process 总被引:1,自引:0,他引:1
Jiaqiang Dang Gongyu Liu Yaofeng Chen Weiwei Ming Ming Chen 《Materials and Manufacturing Processes》2019,34(7):749-758
Additive Manufacturing (AM) technology is being extensively utilized in many industries concerning its superior advantage of easily fabricating the 3D parts possessing relatively high geometrical complicacy. Nevertheless, the AM parts generally need conventional machining, such as drilling, to meet the practical requirements, indicating disparate machinability compared with those manufactured by conventional wrought processes. Hence, to investigate the effects of machining parameters on the drilling characteristics of AM parts is of great significance. This work experimentally studied the machinability of the additive manufactured Ti6Al4V by covering a variety of topics including the cutting forces, temperatures, machined surface roughness, tool wear modes and chip morphology with selected cutting speeds and feed rates under dry drilling process. The material utilized in experiments is the Ti6Al4V manufactured by Direct Metal Laser Sintering (DMLS) technology. The experimental results highlight the parametric influence on the machinability of DMLS Ti6Al4V and present the possibility to validly redesign the machining parameters accordingly. 相似文献
1000.