全文获取类型
收费全文 | 12667篇 |
免费 | 915篇 |
国内免费 | 9篇 |
专业分类
电工技术 | 77篇 |
综合类 | 8篇 |
化学工业 | 5066篇 |
金属工艺 | 127篇 |
机械仪表 | 296篇 |
建筑科学 | 452篇 |
矿业工程 | 17篇 |
能源动力 | 319篇 |
轻工业 | 3144篇 |
水利工程 | 109篇 |
石油天然气 | 69篇 |
无线电 | 468篇 |
一般工业技术 | 1673篇 |
冶金工业 | 530篇 |
原子能技术 | 35篇 |
自动化技术 | 1201篇 |
出版年
2024年 | 41篇 |
2023年 | 179篇 |
2022年 | 901篇 |
2021年 | 1017篇 |
2020年 | 413篇 |
2019年 | 422篇 |
2018年 | 473篇 |
2017年 | 496篇 |
2016年 | 541篇 |
2015年 | 440篇 |
2014年 | 574篇 |
2013年 | 865篇 |
2012年 | 826篇 |
2011年 | 936篇 |
2010年 | 711篇 |
2009年 | 662篇 |
2008年 | 604篇 |
2007年 | 571篇 |
2006年 | 440篇 |
2005年 | 330篇 |
2004年 | 280篇 |
2003年 | 251篇 |
2002年 | 234篇 |
2001年 | 142篇 |
2000年 | 94篇 |
1999年 | 127篇 |
1998年 | 106篇 |
1997年 | 107篇 |
1996年 | 100篇 |
1995年 | 70篇 |
1994年 | 58篇 |
1993年 | 58篇 |
1992年 | 64篇 |
1991年 | 46篇 |
1990年 | 38篇 |
1989年 | 33篇 |
1988年 | 33篇 |
1987年 | 31篇 |
1986年 | 40篇 |
1985年 | 35篇 |
1984年 | 26篇 |
1983年 | 22篇 |
1982年 | 15篇 |
1981年 | 16篇 |
1980年 | 19篇 |
1979年 | 19篇 |
1978年 | 20篇 |
1977年 | 13篇 |
1976年 | 7篇 |
1975年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Giordano Maria C. Longhi Stefano Barelli Matteo Mazzanti Andrea Buatier de Mongeot Francesco Della Valle Giuseppe 《Nano Research》2018,11(7):3943-3956
Nano Research - The engineering of self-organized plasmonic metasurfaces is demonstrated using a maskless technique with defocused ion-beam sputtering and kinetically controlled deposition. The... 相似文献
82.
Nima Taghipour Mariona Dalmases Guy L. Whitworth Miguel Dosil Andreas Othonos Sotirios Christodoulou Shanti Maria Liga Gerasimos Konstantatos 《Advanced materials (Deerfield Beach, Fla.)》2023,35(1):2207678
The use of colloidal quantum dots (CQDs) as a gain medium in infrared laser devices has been underpinned by the need for high pumping intensities, very short gain lifetimes, and low gain coefficients. Here, PbS/PbSSe core/alloyed-shell CQDs are employed as an infrared gain medium that results in highly suppressed Auger recombination with a lifetime of 485 ps, lowering the amplified spontaneous emission (ASE) threshold down to 300 µJ cm−2, and showing a record high net modal gain coefficient of 2180 cm−1. By doping these engineered core/shell CQDs up to nearly filling the first excited state, a significant reduction of optical gain threshold is demonstrated, measured by transient absorption, to an average-exciton population-per-dot 〈Nth〉g of 0.45 due to bleaching of the ground state absorption. This in turn have led to a fivefold reduction in ASE threshold at 〈Nth〉ASE = 0.70 excitons-per-dot, associated with a gain lifetime of 280 ps. Finally, these heterostructured QDs are used to achieve near-infrared lasing at 1670 nm at a pump fluences corresponding to sub-single-exciton-per-dot threshold (〈Nth〉Las = 0.87). This work brings infrared CQD lasing thresholds on par to their visible counterparts, and paves the way toward solution-processed infrared laser diodes. 相似文献
83.
G Maria G Brisinda AR Bentivoglio E Cassetta D Gui A Albanese 《Canadian Metallurgical Quarterly》1998,228(5):664-669
OBJECTIVE: To determine whether the recently published guidelines on neuroimaging in patients with new-onset seizures are applicable to children. METHODS: We carried out a retrospective analysis of 107 neurologically normal children (excluding children with simple febrile seizures) who had undergone neuroimaging when they presented to the emergency department with a possible "first seizure." RESULTS: Eight of the 107 children had nonepileptic events (gastroesophageal reflux, syncopal event, rigor). Of the remaining 99 children, 49 had provoked seizures (complicated febrile seizure, meningo-encephalitis, toxic or metabolic abnormalities), and 50 had unprovoked seizures. A total of 19 children had brain abnormalities identified on computed tomography (CT) scan; 7 received further investigation or intervention as a result of CT scan findings (2 with tumors, 3 with vascular anomalies, 1 with cysticercosis, and 1 with obstructive hydrocephalus). CT scan abnormalities requiring treatment or monitoring were more frequently seen in children with their first unprovoked seizure (P < .01) and in those children whose seizure onset had been focal or who had focal abnormalities identified on postictal neurologic examination (P < .04). CONCLUSION: In a child, a seizure in the setting of a fever rarely indicates the presence of an unexpected CT scan lesion requiring intervention. 相似文献
84.
A case situation arising in a normal interaction among people is the baseline for discussing properties of the theory of viewpoints. In particular we consider how to ensure agreement on the meaning of certain utterances by agents who have different perspectives on the situation, while maintaning other knowledge as private. We argue that communication should be modeled as adding facts to the common knowledge of agents. We introduce the principle of 'referent sharing' in communications and argue that common knowledge resulting from communication should only use constants whose referent is manifest to the parties involved. 相似文献
85.
Maria Izquierdo-Pulido Soledad Albalá-Hurtado Abel Mariné-Font M. Carmen Vidal-Carou 《Zeitschrift für Lebensmitteluntersuchung und -Forschung A》1996,203(6):507-511
Ten biogenic amines in Spanish beers were studied using HPLC. Agmatine, tyramine and putrescine were the prevailing amines, while histamine,-phenylethylamine, tryptamine, cadaverine, spermine and spermidine were detected at relatively low levels (in general <2 mg/l). On the basis of the wide range of levels observed for tyramine (from 1.90 to 31.55 mg/l), the consumption of beer requires restriction in patients receiving monoamine oxidase inhibitor drugs. Biogenic amine levels in beers of the same type from the same company and from different companies were monitored every month over 1 year. Agmatine and putrescine levels showed minimal fluctuations in beers from the same company as well as from different breweries. Raw materials and brewing conditions would not affect the levels of those amines. However, tyramine levels were subject to wide fluctuations in beers produced by particular breweries irrespective of whether they were produced by the same company. Relatively high levels of tyramine were specific to some breweries. 相似文献
86.
I. N. Mihailescu Adriana Lita V. S. Teodorescu A. Luches M. Martino A. Perrone Maria Gartner 《Journal of Materials Science》1996,31(11):2839-2847
We report the deposition of Si-N films by multipulse excimer laser ( = 308 nm, FWHM = 30 ns) ablation of Si wafers placed in a slow flow of NH3 in the pressure range (1 bar-1 mbar). The films are deposited on to a Si collector placed parallel to the Si target. We succeeded in depositing pure amorphous Si3N4 films at a pressure of 1 mbar of NH3. The deposition rate reached a maximum value of 0.2–0.3 nm per pulse. At lower pressures, the deposited films consist of a fine mixture of three amorphous phases (amorphous stoichiometric silicon nitride, amorphous non-stoichiometric silicon nitride and amorphous silicon). The amorphous silicon is prevalent in films deposited at a pressure of several to several tens of bars. Droplets of polycrystalline -Si are sometimes visible on the film surface. The experimental evidence, is analysed with a view to elucidating the participation in the chemical synthesis of the three main stages of the process: the substance expulsion from the target by laser ablation, the transition through the gas of the expulsed substance and it's final impact on the collector. We conclude that silicon nitride is mostly synthesized during the impact on the collector of the flow of the ablated substance. 相似文献
87.
A number of robust and diagnostic techniques for the linear regression are in terms of p-dimensional subsets of the original sample. In a sample of size n this leads to consider
n
C
p
subsets. To reduce the computational burden, a limited number of subsets can be selected by means of a sub-sampling scheme. In this paper we suggest and discuss the use of a Balanced Incomplete Block design plan. 相似文献
88.
89.
In this paper a new nonlinear feedback control law for continuous stirred tank reactors, obtained by exact Input/Output (I/O) linearization and Sontag's input‐to‐state stability feedback control redesign methods, is studied. By the new feedback control law, a significant attenuation of the disturbance effect is guaranteed, with evident improvement with respect to control laws obtained by the exact I/O linearization method. The performed simulations validate the theoretical results. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
90.
In this paper, we propose novel elastic graph matching (EGM) algorithms for face recognition assisted by the availability of 3D facial geometry. More specifically, we conceptually extend the EGM algorithm in order to exploit the 3D nature of human facial geometry for face recognition/verification. In order to achieve that, first we extend the matching module of the EGM algorithm in order to capitalize on the 2.5D facial data. Furthermore, we incorporate the 3D geometry into the multiscale analysis used and build a novel geodesic multiscale morphological pyramid of dilations/erosions in order to fill the graph jets. We show that the proposed advances significantly enhance the performance of EGM algorithms. We demonstrate the efficiency of the proposed advances in the face recognition/verification problem using photometric stereo. 相似文献