全文获取类型
收费全文 | 3599篇 |
免费 | 211篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 29篇 |
综合类 | 2篇 |
化学工业 | 900篇 |
金属工艺 | 79篇 |
机械仪表 | 84篇 |
建筑科学 | 137篇 |
矿业工程 | 12篇 |
能源动力 | 131篇 |
轻工业 | 270篇 |
水利工程 | 30篇 |
石油天然气 | 8篇 |
无线电 | 278篇 |
一般工业技术 | 753篇 |
冶金工业 | 487篇 |
原子能技术 | 17篇 |
自动化技术 | 595篇 |
出版年
2024年 | 8篇 |
2023年 | 49篇 |
2022年 | 94篇 |
2021年 | 174篇 |
2020年 | 89篇 |
2019年 | 84篇 |
2018年 | 125篇 |
2017年 | 114篇 |
2016年 | 122篇 |
2015年 | 103篇 |
2014年 | 164篇 |
2013年 | 255篇 |
2012年 | 227篇 |
2011年 | 287篇 |
2010年 | 206篇 |
2009年 | 171篇 |
2008年 | 172篇 |
2007年 | 183篇 |
2006年 | 121篇 |
2005年 | 103篇 |
2004年 | 100篇 |
2003年 | 88篇 |
2002年 | 78篇 |
2001年 | 44篇 |
2000年 | 40篇 |
1999年 | 37篇 |
1998年 | 73篇 |
1997年 | 70篇 |
1996年 | 37篇 |
1995年 | 39篇 |
1994年 | 29篇 |
1993年 | 26篇 |
1992年 | 24篇 |
1991年 | 16篇 |
1990年 | 28篇 |
1989年 | 18篇 |
1988年 | 11篇 |
1987年 | 9篇 |
1986年 | 11篇 |
1985年 | 18篇 |
1984年 | 9篇 |
1983年 | 13篇 |
1982年 | 9篇 |
1981年 | 13篇 |
1980年 | 11篇 |
1979年 | 10篇 |
1977年 | 10篇 |
1976年 | 21篇 |
1975年 | 8篇 |
1974年 | 9篇 |
排序方式: 共有3812条查询结果,搜索用时 15 毫秒
151.
Nupur Bhargava Jay Prakash Gupta Thomas Adam James Kolodzey 《Journal of Electronic Materials》2014,43(4):931-937
Boron-doped Ge1?x Sn x alloys with atomic fractions of tin up to x = 0.08 were grown on n-Ge(001) substrates using solid-source molecular beam epitaxy, in order to study their structural properties. The total boron concentration in the alloys was ~ 1018 cm?3 as measured by secondary-ion mass spectroscopy, which also indicated low amounts of impurities such as carbon and oxygen. More than 90% of the Sn atoms occupied substitutional lattice sites in the alloy as determined by Rutherford backscattering spectrometry. High-resolution x-ray diffraction showed that the boron-doped Ge1?x Sn x alloys were single crystals that were completely strained with low defect densities and coherent interfaces for thickness up to 90 nm, and for Sn composition of 8%. The boron-doped Ge1?x Sn x /n-Ge formed p–n junctions with conventional rectifying characteristics, indicating that the boron produced electrically active acceptor states. 相似文献
152.
153.
Adam Okulicz-Kozaryn 《Scientometrics》2013,96(3):679-681
Scientific writing is about communicating ideas. Today, simplicity is more important than ever. Scientist are overwhelmed with new information. The overall growth rate for scientific publication over the last few decades has been at least 4.7 % per year, which means doubling publication volume every 15 years. I measure simplicity/readability with proportion of adjectives and adverbs in a paper, and find natural science to be the most readable and social science the least readable. 相似文献
154.
In an asymmetric rendezvous system, such as an unfair synchronous queue or an elimination array, threads of two types, consumers and producers, show up and are matched each with a unique thread of the other type. Here we present new highly scalable, high throughput asymmetric rendezvous systems that outperform prior synchronous queue and elimination array implementations under both symmetric and asymmetric workloads (more operations of one type than the other). Based on this rendezvous system, we also construct a highly scalable and competitive stack implementation. 相似文献
155.
156.
157.
Yanmin Zhou Adam Robinson Ullrich Steiner Walter Federle 《Journal of the Royal Society Interface》2014,11(98)
Insect climbing footpads are able to adhere to rough surfaces, but the details of this capability are still unclear. To overcome experimental limitations of randomly rough, opaque surfaces, we fabricated transparent test substrates containing square arrays of 1.4 µm diameter pillars, with variable height (0.5 and 1.4 µm) and spacing (from 3 to 22 µm). Smooth pads of cockroaches (Nauphoeta cinerea) made partial contact (limited to the tops of the structures) for the two densest arrays of tall pillars, but full contact (touching the substrate in between pillars) for larger spacings. The transition from partial to full contact was accompanied by a sharp increase in shear forces. Tests on hairy pads of dock beetles (Gastrophysa viridula) showed that setae adhered between pillars for larger spacings, but pads were equally unable to make full contact on the densest arrays. The beetles'' shear forces similarly decreased for denser arrays, but also for short pillars and with a more gradual transition. These observations can be explained by simple contact models derived for soft uniform materials (smooth pads) or thin flat plates (hairy-pad spatulae). Our results show that microstructured substrates are powerful tools to reveal adaptations of natural adhesives for rough surfaces. 相似文献
158.
Adam I. Cygankiewicz Alicja Maslowska Wanda M. Krajewska 《Critical reviews in food science and nutrition》2014,54(6):771-780
Taste perception is one of the senses crucial for many organisms. There are five basic tastes, i.e., sweet, bitter, salty, sour, and umami, and it is suggested that the taste of fat should be included in this list. This paper reviews the current state of knowledge about the involvement of G protein coupled receptors (GPCRs) in taste sensing and intracellular signaling. GPCR receptors are focal point of interest for pharmaceutical industry. However, their ability to interact with a variety of taste substances makes these receptors interesting target for food and nutrient companies. 相似文献
159.
Renata Rybakiewicz David Djurado Hubert Cybulski Ewelina Dobrzynska Irena Kulszewicz-Bajer Damien Boudinet Jean-Marie Verilhac Malgorzata Zagorska Adam Pron 《Synthetic Metals》2011,161(15-16):1600-1610
New solution processable organic semiconductors, consisting of pyrromelitic, naphthalene or perylene bisimide core and triarylamine N-substituents, have been synthesized. All three compounds are electrochemically active and undergo quasi-reversible oxidation and reduction as evidenced by cyclic voltammetry investigations. The oxidation process involves the transformation of the triarylamine substituents into radical cations as proven spectroscopically and spectroelectrochemically. The reduction process occurs at the arylene bisimide core leading to the formation of a radical anion and eventually a dianion in the second step. These findings are in perfect agreement with the DFT calculations which show that in the synthesized molecules the HOMO orbital is located on the triarylamine moiety whereas the LUMO one on the bisimide core. In all molecules studied the electrochemically determined ionization potential (IP) is slightly higher than 5.0 eV whereas in naphthalene and perylene derivatives the electron affinity (EA) is close to ?3.9 eV. These values fulfill the requirements for n-type (electron) semiconductors in air operating n-channel field effect transistors (FETs) as well as for p-type (hole) conductors in p-channel FETs. To verify whether the newly synthesized compounds exhibit the expected electrical transport properties all organic (CYTOP dielectric) test transistors were fabricated. All three semiconductors showed no field effect in the n-channel configuration. To the contrary, they could be used in p-channel FETs showing, in the saturation regime, the hole mobility approaching 10?4 cm2 V?1 s?1 – the value which slightly exceeds that measured for low molecular weight, amorphous triarylamine semiconductors. 相似文献
160.
In this paper the minmax (regret) versions of some basic polynomially solvable deterministic network problems are discussed. It is shown that if the number of scenarios is unbounded, then the problems under consideration are not approximable within log1−?K for any ?>0 unless NP⊆DTIME(npolylogn), where K is the number of scenarios. 相似文献