全文获取类型
收费全文 | 4261篇 |
免费 | 310篇 |
国内免费 | 20篇 |
专业分类
电工技术 | 59篇 |
综合类 | 11篇 |
化学工业 | 851篇 |
金属工艺 | 70篇 |
机械仪表 | 162篇 |
建筑科学 | 137篇 |
矿业工程 | 1篇 |
能源动力 | 193篇 |
轻工业 | 278篇 |
水利工程 | 29篇 |
石油天然气 | 8篇 |
无线电 | 832篇 |
一般工业技术 | 806篇 |
冶金工业 | 310篇 |
原子能技术 | 16篇 |
自动化技术 | 828篇 |
出版年
2023年 | 48篇 |
2022年 | 64篇 |
2021年 | 159篇 |
2020年 | 117篇 |
2019年 | 128篇 |
2018年 | 157篇 |
2017年 | 126篇 |
2016年 | 176篇 |
2015年 | 122篇 |
2014年 | 196篇 |
2013年 | 366篇 |
2012年 | 258篇 |
2011年 | 241篇 |
2010年 | 235篇 |
2009年 | 223篇 |
2008年 | 209篇 |
2007年 | 198篇 |
2006年 | 157篇 |
2005年 | 120篇 |
2004年 | 108篇 |
2003年 | 107篇 |
2002年 | 103篇 |
2001年 | 79篇 |
2000年 | 74篇 |
1999年 | 88篇 |
1998年 | 142篇 |
1997年 | 97篇 |
1996年 | 60篇 |
1995年 | 58篇 |
1994年 | 52篇 |
1993年 | 54篇 |
1992年 | 43篇 |
1991年 | 27篇 |
1990年 | 23篇 |
1989年 | 22篇 |
1988年 | 15篇 |
1987年 | 12篇 |
1986年 | 15篇 |
1985年 | 13篇 |
1984年 | 15篇 |
1983年 | 16篇 |
1982年 | 11篇 |
1981年 | 8篇 |
1980年 | 5篇 |
1979年 | 3篇 |
1978年 | 5篇 |
1977年 | 13篇 |
1976年 | 4篇 |
1971年 | 3篇 |
1970年 | 5篇 |
排序方式: 共有4591条查询结果,搜索用时 15 毫秒
61.
Chun‐Wei Liu Chi‐Hung Lee Shih‐Chieh Lin 《Journal of the Society for Information Display》2012,20(12):646-652
This study proposes a roll‐to‐roll process‐based sub‐wavelength grating, which is attached on a light bar to turn the side‐lit red/green/blue (620, 520, and 450 nm) incident rays into a uniformly and normally output white light with high illuminance from the light bar's surface. On the basis of the rigorous coupling wave analysis, the relationship between the first‐order transmission/reflection efficiency and the pitch of the gratings with different shapes was analyzed. The optimal design can effectively reduce the coupling length and enhance the white color balance for display applications. 相似文献
62.
Jean-Pierre Montheard Bernard Boinon Ahmed Belfkira Abderahim Sadel Quang-Tho Pham 《Polymer Bulletin》1992,28(6):615-620
Summary Vinylidene cyanide has been copolymerized in solution by radical reaction with equal initial mole fraction of para substituted acetoxystyrenes. The copolymers have been characterized by means of DSC, TGA and GPC. These products are stable up to 220° and have no visible glass transition temperature. The microstructure of these new copolymers has been studied by 13CNMR; they have an alternating structure and monomers units are arranged in head-to-tail placements. 相似文献
63.
DNA methylation is a prevalent regulatory modification in prokaryotes and eukaryotes. N1-methyladenine (m1A) and N6-methyladenine (m6A) have been found to be capable of altering DNA structures via disturbing Watson–Crick base pairing. However, little has been known about their influences on non-B DNA structures, which are associated with genetic instabilities. In this work, we investigated the effects of m1A and m6A on both the structure and thermodynamic stability of a newly reported DNA minidumbbell formed by two TTTA tetranucleotide repeats. As revealed by the results of nuclear magnetic resonance spectroscopic studies, both m1A and m6A favored the formation of a T·m1A and T·m6A Hoogsteen base pair, respectively. More intriguingly, the m1A and m6A modifications brought about stabilization and destabilization effects on the DNA minidumbbell, respectively. This work provides new biophysical insights into the effects of adenine methylation on the structure and thermodynamic stability of DNA. 相似文献
64.
Yuk Ming X. Hung Hung Mariano H. Talou María A. Camerucci 《International Journal of Applied Ceramic Technology》2021,18(5):1466-1477
Alumina ceramic porous structures were shaped by the fused deposition of alumina/polyamide 612 composite granules using an FDM 3D printer with a modified extruder to process granulated powder instead of a filament. The composite granules were prepared via thermally induced phase separation (TIPS). Firstly, in order to determine the proportion of polymer/solvent to be used in the TIPS process, different volume fractions of PA612 in dimethyl sulfoxide (DMSO) were studied (0.01 to 0.20), and the granules obtained were characterized by SEM, DSC, and Raman spectroscopy. Secondly, the addition of different ceramic loadings to the PA612/DMSO solution was studied with the aim of determining the amount to be used for preparing the composite granules by TIPS. In particular, the effect of the alumina content on the morphology and size of the obtained composite granules was studied. In addition, rheological properties (oscillatory and rotational tests) of the feed materials were studied. Finally, the printing conditions, including the nozzle temperature and nozzle diameter, and the extrusion process, were optimized in order to obtain porous structures with good quality. Alumina porous structures were successfully printed, debinded, and sintered. Adequate bonding between layers was achieved, and no defects at interfaces were detected. 相似文献
65.
Hung C. Ling Man F. Yan Warren W. Rhodes 《Journal of the American Ceramic Society》1991,74(2):287-289
The aging behavior of a series of lead perovskite dielectrics with the compositions x Pb(Fe2/3 W1/3 )O3 ·(1 – x )Pb(Fe1/2 -Nb1/2 )O3 , where 0 ≤ x ≤ 1, and the effect of dopants were studied. Below the Curie temperature ( T c ), the capacitance and the dissipation factor (tan δ) decrease approximately linearly with logarithmic time. The aging rate depends on the temperature difference, Δ T , between the aging temperature and T c , and on the dopant concentration, but is independent of the measurement frequency between 1 and 1000 kHz. The maximum aging rate is about 3% per decade of time for capacitance and 5% per decade for tan δ at 1 mol% dopant concentration, and increases to 6.3% for capacitance and 8.5% for tan δ at 0.7 mol% dopant concentration. These results are consistent with an aging mechanism caused by changing ferroelectric domain structure with time, as proposed for BaTiO3 . 相似文献
66.
Fanqin Meng Steven F. Dec Don Williamson Phat Pham Michael A. Yandrasits Andrew M. Herring 《Electrochimica acta》2007,53(3):1372-1378
A perfluorosulfonic acid (PFSA) polymer with pendant side chain -O(CF2)4SO3H was doped with the heteropoly acids (HPAs), H3PW12O40 and H4SiW12O40. Infrared spectroscopy revealed a strong interaction between the HPA and the PFSA ionomer. Modes associated with the peripheral bonds of the HPA were shifted to lower wave numbers when doped into PFSA membranes. Small-angle X-ray scattering (SAXS) measurements showed the presence of large crystallites of HPA in the membrane with d spacings of ca. 10 Å, close to the lattice spacing observed in bulk HPA crystals. Under wet conditions the HPA was more dispersed and constrained the size of the sulfonic acid clusters to 20 Å at a 5 wt% HPA doping level, the same as in the vacuum treated ionomer samples. Under conditions of minimum hydration the HPA decreased the Ea for the self-diffusion of water from 27 to 15 kJ mol−1. The reverse trend was seen under 100% RH conditions. Proton conductivity measurements showed improved proton conductivity of the HPA doped PFSAs at a constant dew point of 80 °C for all temperatures up to 120 °C and at all relative hummidities up to 80%. The activation energy for proton conduction generally was lower than for the undoped materials at RH ≤80%. Significantly the Ea was 1/2 that of the undoped material at RHs of 40 and 60%. A practical proton conductivity of 113 mS cm−1 was observed at 100 °C and 80% RH. 相似文献
67.
Parallelizing Complex Streaming Applications on Distributed Scratchpad Memory Multicore Architecture
Shin-Kai Chen Cheng-Yu Hung Ching-Chih Chen Chih-Wei Liu 《International journal of parallel programming》2014,42(6):875-899
Multicore processors can provide sufficient computing power and flexibility for complex streaming applications, such as high-definition video processing. For less hardware complexity and power consumption, the distributed scratchpad memory architecture is considered, instead of the cache memory architecture. However, the distributed design poses new challenges to programming. It is difficult to exploit all available capabilities and achieve maximal throughput, due to the combined complexity of inter-processor communication, synchronization, and workload balancing. In this study, we developed an efficient design flow for parallelizing multimedia applications on a distributed scratchpad memory multicore architecture. An application is first partitioned into streaming components and then mapped onto multicore processors. Various hardware-dependent factors and application-specific characteristics are involved in generating efficient task partitions and allocating resources appropriately. To test and verify the proposed design flow, three popular multimedia applications were implemented: a full-HD motion JPEG decoder, an object detector, and a full-HD H.264/AVC decoder. For demonstration purposes, SONY PlayStation \(^{\circledR }\) 3 was selected as the target platform. Simulation results show that, on PS3, the full-HD motion JPEG decoder with the proposed design flow can decode about 108.9 frames per second (fps) in the 1080p format. The object detection application can perform real-time object detection at 2.84 fps at \(1280 \times 960\) resolution, 11.75 fps at \(640 \times 480\) resolution, and 62.52 fps at \(320 \times 240\) resolution. The full-HD H.264/AVC decoder applications can achieve nearly 50 fps. 相似文献
69.
Tuan D. Pham Dinh T.P. Le Jinwei Xu Duc T. Nguyen Robert G. Martindale Clifford W. Deveney 《Computer methods and programs in biomedicine》2014
An abdominal wall hernia is a protrusion of the intestine through an opening or area of weakness in the abdominal wall. Correct pre-operative identification of abdominal wall hernia meshes could help surgeons adjust the surgical plan to meet the expected difficulty and morbidity of operating through or removing the previous mesh. First, we present herein for the first time the application of image analysis for automated identification of hernia meshes. Second, we discuss the novel development of a new entropy-based image texture feature using geostatistics and indicator kriging. Third, we seek to enhance the hernia mesh identification by combining the new texture feature with the gray-level co-occurrence matrix feature of the image. The two features can characterize complementary information of anatomic details of the abdominal hernia wall and its mesh on computed tomography. Experimental results have demonstrated the effectiveness of the proposed study. The new computational tool has potential for personalized mesh identification which can assist surgeons in the diagnosis and repair of complex abdominal wall hernias. 相似文献
70.
Extraction and implementation of muscle synergies in neuro-mechanical control of upper limb movement
Hang Pham Yohei Ariga Kenta Tominaga Takanori Oku Kanna Nakayama Mitsunori Uemura 《Advanced Robotics》2014,28(11):745-757
This work faces the redundancy problem, a central concern in robotics, in a particular force-producing task by using muscle synergies to simplify the control. We extracted muscle synergies from human electromyograph signals and interpreted the physical meaning of the identified muscle synergies. Based on the human analysis results, we hypothesized a novel control framework that can explain the mechanism of the human motor control. The framework was tested in controlling a pneumatic-driven robotic arm to perform a reaching task. This control method, which uses only two synergies as manipulated variables for driving antagonistic pneumatic artificial muscles to generate desired movements, would be useful to deal with the redundancy problem; thus, suggesting a simple but efficient control for human-like robots to work safely and compliantly with humans. 相似文献