全文获取类型
收费全文 | 10990篇 |
免费 | 247篇 |
国内免费 | 19篇 |
专业分类
电工技术 | 113篇 |
综合类 | 15篇 |
化学工业 | 1549篇 |
金属工艺 | 94篇 |
机械仪表 | 87篇 |
建筑科学 | 541篇 |
矿业工程 | 38篇 |
能源动力 | 130篇 |
轻工业 | 5744篇 |
水利工程 | 30篇 |
石油天然气 | 23篇 |
无线电 | 408篇 |
一般工业技术 | 962篇 |
冶金工业 | 654篇 |
原子能技术 | 38篇 |
自动化技术 | 830篇 |
出版年
2021年 | 102篇 |
2019年 | 99篇 |
2016年 | 164篇 |
2015年 | 150篇 |
2014年 | 242篇 |
2013年 | 297篇 |
2012年 | 262篇 |
2011年 | 264篇 |
2010年 | 218篇 |
2009年 | 278篇 |
2008年 | 291篇 |
2007年 | 298篇 |
2006年 | 235篇 |
2005年 | 204篇 |
2004年 | 170篇 |
2003年 | 163篇 |
2002年 | 107篇 |
2000年 | 100篇 |
1998年 | 130篇 |
1993年 | 100篇 |
1990年 | 109篇 |
1989年 | 121篇 |
1988年 | 97篇 |
1987年 | 117篇 |
1986年 | 96篇 |
1985年 | 114篇 |
1984年 | 119篇 |
1981年 | 104篇 |
1980年 | 109篇 |
1979年 | 97篇 |
1978年 | 102篇 |
1977年 | 120篇 |
1976年 | 121篇 |
1973年 | 110篇 |
1972年 | 94篇 |
1971年 | 98篇 |
1970年 | 100篇 |
1916年 | 110篇 |
1915年 | 108篇 |
1914年 | 98篇 |
1913年 | 108篇 |
1912年 | 140篇 |
1911年 | 120篇 |
1910年 | 127篇 |
1909年 | 136篇 |
1908年 | 137篇 |
1907年 | 130篇 |
1906年 | 130篇 |
1905年 | 140篇 |
1904年 | 130篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Flow profile measurement in microchannel using the optical feedback interferometry sensing technique 总被引:1,自引:1,他引:0
Lucie Campagnolo Milan Nikolić Julien Perchoux Yah Leng Lim Karl Bertling Karine Loubière Laurent Prat Aleksandar D. Rakić Thierry Bosch 《Microfluidics and nanofluidics》2013,14(1-2):113-119
The need to accurately measure flow profiles in microfluidic channels is well recognised. In this work, we present a new optical feedback interferometry (OFI) flow sensor that accurately measures local velocity in fluids and enables reconstruction of a velocity profile inside a microchannel. OFI is a self-aligned interferometric technique that uses the laser as both the transmitter and the receiver thus offering high sensitivity, fast response, and a simple and compact optical design. The system described here is based on a commercial semiconductor laser and has been designed to achieve a micrometer-range spatial resolution. The sensor performance was validated by reconstructing the velocity profile inside a circular cross-section flow-channel with 320 $\upmu $ m internal diameter, with a relative error smaller than 1.8 %. The local flow velocity is directly measured, thus avoiding the need for model based profile calculation and uncertainties inherent to this approach. The system was validated by successfully extracting the flow profiles in both Newtonian and shear-thinning liquids. 相似文献
52.
Modern techniques for fitting generalized additive models mostly rely on basis expansions of covariates using a large number of basis functions and penalized estimation of parameters. For example, a mixed model approach is used to fit a model for children’s lung function that allows for non-linear influence of several covariates available in a substantial data set. While the resulting model is expected to have good prediction performance, its handling beyond simple visual presentation is problematic. It is shown how the number basis functions of the underlying B-spline representation can be reduced by knot removal techniques without refitting, while preserving the shape of the fitted functions. The condition for exact knot removal is extended towards approximate knot removal by incorporating the covariance matrix of the initial parameter estimates, resulting in considerable simplification of the model. Covariance matrices for the transformed parameter estimates are provided. It is demonstrated that enforcing the knot removal condition during estimation leads to the difference penalties employed in the P-spline approach for estimation of B-spline coefficients, and therefore provides a further justification for this type of penalty. A final transform to a truncated power basis provides a simple equation for the model. This increases transportability, while retaining properties of the initial fit such as good prediction performance. 相似文献
53.
54.
Jolita Ralyt Manfred A. Jeusfeld Per Backlund Harald Kühn Nicolas Arni-Bloch 《Information Systems》2008,33(7-8):754
Interoperability is a key property of enterprise applications, which is hard to achieve due to the large number of interoperating components and semantic heterogeneity. The inherent complexity of interoperability problems implies that there exists no silver bullet to solve them. Rather, the knowledge about how to solve wicked interoperability problems is hidden in the application cases that expose those problems. The paper addresses the question of how to organise and use method knowledge to resolve interoperability problems. We propose the structure of a knowledge-based system that can deliver situation-specific solutions, called method chunks. Situational Method Engineering promotes modularisation and formalisation of method knowledge in the form of reusable method chunks, which can be combined to compose a situation-specific method. The method chunks are stored in a method chunk repository. In order to cater for management and retrieval, we introduce an Interoperability Classification Framework, which is used to classify and tag method chunks and to assess the project situation in which they are to be used. The classification framework incorporates technical as well as business and organisational aspects of interoperability. This is an important feature as interoperability problems typically are multifaceted spanning multiple aspects. We have applied the approach to analyse an industry case from the insurance sector to identify and classify a set of method chunks. 相似文献
55.
Yannick Schellander Marius Winter Maurice Schamber Fabian Munkes Patrick Schalberger Harald Kuebler Tilman Pfau Norbert Fruehauf 《Journal of the Society for Information Display》2023,31(5):363-372
In this work, real-time ultraviolet photodetectors are realized through metal–semiconductor–metal (MSM) structures. Amorphous indium gallium zinc oxide (a-IGZO) is used as semiconductor material and gold as metal electrodes. The readout of an individual sensor is implemented by a transimpedance amplifier (TIA) consisting of an all-enhancement a-IGZO thin-film transistor (TFT) operational amplifier and a switched capacitor (SC) as feedback resistance. The photosensor and the transimpedance amplifier are both manufactured on glass substrates. The measured photosensor possesses a high responsivity R , a low response time t R E S , and a good noise equivalent power value NEP . 相似文献
56.
57.
Decoupling Charge Transport and Electroluminescence in a High Mobility Polymer Semiconductor 下载免费PDF全文
58.
Single‐Molecule Magnets: Giant Hysteresis of Single‐Molecule Magnets Adsorbed on a Nonmagnetic Insulator (Adv. Mater. 26/2016) 下载免费PDF全文
59.
Web‐Like Interconnected Carbon Networks from NaCl‐Assisted Pyrolysis of ZIF‐8 for Highly Efficient Oxygen Reduction Catalysis 下载免费PDF全文
Yuhong Qian Tao An Karl Erik Birgersson Zhaolin Liu Dan Zhao 《Small (Weinheim an der Bergstrasse, Germany)》2018,14(16)
The oxygen reduction reaction (ORR) is under intense research due to its significance in energy storage and conversion processes. Recent studies show that interconnected and hierarchically porous structures can further enhance ORR kinetics as well as catalyst durability, but their preparation can be quite time and/or chemical consuming. Here, a simple approach is reported to prepare such complex structures by pyrolyzing composites containing NaCl and ZIF‐8. The templating effect of molten NaCl connects ZIF‐8 particles into web‐like carbon networks. During ORR activity measurements, it achieves a 0.964 V onset potential and a 38 mV dec?1 Tafel slope, which are comparable to those of the benchmark Pt/C (0.979 V and 40 mV dec?1). Due to the metal‐free feature, this catalyst exhibits a 16 mV shift in half‐wave potential after a 10 000‐cycle durability test, which is only 60% of that of Pt/C. The catalyst is also tested in Zn–air batteries and the assemblies are able to work at above 1.2 V for 140 h, which triples the life held by those with Pt/C. This study demonstrates a facile strategy to prepare metal‐free ORR catalysts with interconnectivity and hierarchical porosity, and proves their great potentials in ORR catalysis and Zn–air batteries. 相似文献
60.
Integrating intelligent job-scheduling into a real-world production-scheduling system 总被引:1,自引:0,他引:1
The paper addresses the problem of scheduling production orders (jobs). First, an approach based on simulated annealing and Hopfield nets is described. Since performance was unsatisfactory for real-world applications, we changed the problem representation and tuned the scheduling method, dropping features of the Hopfield net and retaining simulated annealing. Both computing time and solution quality were significantly improved. The scheduling method was then integrated into a software system for short-term production planning and control (electronic leitstand). The paper describes how real-world requirements are met, and how the scheduling method interacts with the leitstand's database and graphical representation of schedules. 相似文献