全文获取类型
收费全文 | 26138篇 |
免费 | 1495篇 |
国内免费 | 1466篇 |
专业分类
电工技术 | 845篇 |
技术理论 | 1篇 |
综合类 | 1054篇 |
化学工业 | 7291篇 |
金属工艺 | 7054篇 |
机械仪表 | 1193篇 |
建筑科学 | 1149篇 |
矿业工程 | 314篇 |
能源动力 | 706篇 |
轻工业 | 1692篇 |
水利工程 | 71篇 |
石油天然气 | 553篇 |
武器工业 | 215篇 |
无线电 | 938篇 |
一般工业技术 | 4466篇 |
冶金工业 | 1112篇 |
原子能技术 | 144篇 |
自动化技术 | 301篇 |
出版年
2024年 | 147篇 |
2023年 | 522篇 |
2022年 | 746篇 |
2021年 | 825篇 |
2020年 | 785篇 |
2019年 | 741篇 |
2018年 | 739篇 |
2017年 | 943篇 |
2016年 | 798篇 |
2015年 | 839篇 |
2014年 | 1253篇 |
2013年 | 1353篇 |
2012年 | 1644篇 |
2011年 | 1969篇 |
2010年 | 1554篇 |
2009年 | 1561篇 |
2008年 | 1323篇 |
2007年 | 1591篇 |
2006年 | 1621篇 |
2005年 | 1342篇 |
2004年 | 1170篇 |
2003年 | 961篇 |
2002年 | 865篇 |
2001年 | 685篇 |
2000年 | 647篇 |
1999年 | 486篇 |
1998年 | 420篇 |
1997年 | 313篇 |
1996年 | 280篇 |
1995年 | 232篇 |
1994年 | 196篇 |
1993年 | 152篇 |
1992年 | 139篇 |
1991年 | 80篇 |
1990年 | 55篇 |
1989年 | 52篇 |
1988年 | 20篇 |
1987年 | 7篇 |
1986年 | 15篇 |
1985年 | 4篇 |
1984年 | 3篇 |
1983年 | 6篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1976年 | 2篇 |
1974年 | 1篇 |
1959年 | 2篇 |
1951年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
TBC experience in land- based gas turbines 总被引:1,自引:0,他引:1
This paper summarizes prior and on-going machine evaluations of thermal barrier coatings (TBC) for power generation, that
is large industrial gas turbine applications. Rainbow testing of TBCs on turbine nozzles, shrouds, and buckets are described
along with a test of combustor liners. General Electric Power Generation has conducted more than IS machine tests on TBC turbine
nozzles with various coatings. TBC performance has been quite good, and additional testing, including TBCs on shrouds and
buckets, is continuing. Included is a brief comparison of TBC requirements for power generation and aircraft turbines. 相似文献
82.
83.
84.
Michael E. Becker 《Journal of the Society for Information Display》2015,23(10):472-485
Four years after introduction of the first instrument for measurement of sparkle, the foundations have been reconsidered, and the pool of practical experience has been analyzed to provide a more detailed and complete picture of the subject matter. The following aspects are introduced and discussed: observation conditions and resulting requirements for imaging (sampling) and filtering, analysis of spatial periods and frequencies as a basis for filtering, spatial filtering concepts, sparkle in the frequency domain, sparkle evaluation based on analysis of single images and difference images, origins of unwanted sparkle components, scaling and offset in sparkle evaluation, and verification of the method. 相似文献
85.
A new approach to the design of a neural network (NN) based navigator is proposed in which the mobile robot travels to a pre-defined
goal position safely and efficiently without any prior map of the environment. This navigator can be optimized for any user-defined
objective function through the use of an evolutionary algorithm. The motivation of this research is to develop an efficient
methodology for general goal-directed navigation in generic indoor environments as opposed to learning specialized primitive
behaviors in a limited environment. To this end, a modular NN has been employed to achieve the necessary generalization capability
across a variety of indoor environments. Herein, each NN module takes charge of navigating in a specialized local environment,
which is the result of decomposing the whole path into a sequence of local paths through clustering of all the possible environments.
We verify the efficacy of the proposed algorithm over a variety of both simulated and real unstructured indoor environments
using our autonomous mobile robot platform. 相似文献
86.
The impact of steady-state multiplicities on the control of a simulated industrial scale methyl acetate reactive distillation (RD) column is studied. At a fixed reflux rate, output multiplicity, with multiple output values for the same reboiler duty, causes the column to drift to an undesirable steady-state under open loop operation. The same is avoided for a fixed reflux ratio policy. Input multiplicity, where multiple input values give the same output, leads to “wrong” control action under feedback control severely compromising control system robustness. A new metric, rangeability, is defined to quantify the severity of input multiplicity in a steady-state input–output (IO) relation. Rangeability is used in conjunction with conventional sensitivity analysis for the design of robust control structures for the RD column. Results for the two synthesized control structures show that controlling the most sensitive reactive tray temperature results in poor robustness due to low rangeability causing “wrong” control action for large disturbances. Controlling a reactive tray temperature with acceptable sensitivity but larger rangeability gives better robustness. It is also shown that controlling the difference in the temperature of two suitably chosen reactive trays further improves robustness of both the structures as input multiplicity is avoided. The article brings out the importance of IO relations for control system design and understanding the complex dynamic behavior of RD systems. 相似文献
87.
Due to its excellent chemical and mechanical properties, silicone sealing has been widely used in many industries. Currently, the majority of these sealing tasks are performed by human workers. Hence, they are susceptible to labor shortage problems. The use of vision-guided robotic systems is a feasible alternative to automate these types of repetitive and tedious manipulation tasks. In this paper, we present the development of a new method to automate silicone sealing with robotic manipulators. To this end, we propose a novel neural path planning framework that leverages fractional-order differentiation for robust seam detection with vision and a Riemannian motion policy for effectively learning the manipulation of a sealing gun. Optimal control commands can be computed analytically by designing a deep neural network that predicts the acceleration and associated Riemannian metric of the sealing gun from feedback signals. The performance of our new methodology is experimentally validated with a robotic platform conducting multiple silicone sealing tasks in unstructured situations. The reported results demonstrate that compared with directly predicting the control commands, our neural path planner achieves a more generalizable performance on unseen workpieces and is more robust to human/environment disturbances. 相似文献
88.
E. Vetrivendan G. Thendral A. Ravi Shankar C. Mallika 《Materials and Manufacturing Processes》2017,32(12):1435-1441
The insulation resistance of conventional atmospheric plasma-sprayed alumina coatings with 10–15% porosity is ~1011 Ω. The presence of pores, lamellae boundaries, and other non-fillings dampens the insulation resistance of the coating. In the present study, aluminum phosphate was used to seal the surface of plasma-sprayed alumina coating and evaluate the effect of sealing on the insulation resistance and its thermal cycling response. Sealing was carried out with three concentrations of sealant (P/Al molar ratio of 3, 10, and 15). Characterization by X-ray diffraction and scanning electron microscopy revealed the primary sealing phase as aluminum metaphosphate and effective sealing of the pores by the aluminum phosphate phases. Insulation resistance is improved by two orders of magnitude after sealing the coated samples. Sealing with P/Al molar ratio 3 exhibited maximum insulation resistance of ~1013 Ω at room temperature. Thermal cycling studies between 650°C and 200°C on the sealed samples showed deterioration in thermal cycling life after sealing. 相似文献
89.
Phase Separation Derived Core/Shell Structured Cu11V6O26/V2O5 Microspheres: First Synthesis and Excellent Lithium‐Ion Anode Performance with Outstanding Capacity Self‐Restoration 下载免费PDF全文
Jian Pei Gang Chen Qiang Zhang Changfeng Bie Jingxue Sun 《Small (Weinheim an der Bergstrasse, Germany)》2017,13(17)
Novel amorphous vanadium oxide coated copper vanadium oxide (Cu11V6O26/V2O5) microspheres with 3D hierarchical architecture have been successfully prepared via a microwave‐assisted solution method and subsequent annealing induced phase separation process. Pure Cu11V6O26 microspheres without V2O5 coating are also obtained by an H2O2 solution dissolving treatment. When evaluated as an anode material for lithium‐ion batteries (LIBs), the as‐synthesized hybrid exhibits large reversible capacity, excellent rate capability, and outstanding capacity self‐recovery. Under the condition of high current density of 1 A g?1, the 3D hierarchical Cu11V6O26/V2O5 hybrid maintains a reversible capacity of ≈1110 mA h g?1. Combined electrochemical analysis and high‐resolution transmission electron microscopy observation during cycling reveals that the amorphous V2O5 coating plays an important role on enhancing the electrochemical performances and capacity self‐recovery, which provides an active amorphous protective layer and abundant grain interfaces for efficient inserting and extracting of Li‐ion. As a result, this new copper vanadium oxide hybrid is proposed as a promising anode material for LIBs. 相似文献
90.
Dong-Jun Kwon Jin-Yeong Choi Pyeong-Su Shin K. Lawrence DeVries 《Advanced Composite Materials》2016,25(6):515-524
Dispersion and shape of nanoparticles, as well as interfacial conditions, add significantly to difficulties in composite manufacture. In the work reported here, an innovative method of recycling composites using out-of-date prepreg was investigated in which the carbon nanotube (CNT) on the prepreg was optimally coated. Nanocomposites utilizing the out-of-date prepreg were coated with CNT and fabricated by a sheet molding method. CNT nanofillers were observed to be uniformly dispersed on epoxy prepreg by spray coating. The mechanical and interfacial properties of these CNT coated nanocomposites were improved over those of more conventionally manufactured carbon fiber/epoxy composites. The CNT nanofillers were embedded at the epoxy and fiber interface, as a result of etching of the epoxy prepreg surface by a CNT dispersion solution which enhanced interfacial reactivity. 相似文献