全文获取类型
收费全文 | 534篇 |
免费 | 21篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 3篇 |
化学工业 | 111篇 |
金属工艺 | 56篇 |
机械仪表 | 5篇 |
建筑科学 | 12篇 |
能源动力 | 13篇 |
轻工业 | 36篇 |
石油天然气 | 3篇 |
无线电 | 42篇 |
一般工业技术 | 106篇 |
冶金工业 | 96篇 |
原子能技术 | 5篇 |
自动化技术 | 68篇 |
出版年
2024年 | 2篇 |
2023年 | 3篇 |
2022年 | 16篇 |
2021年 | 19篇 |
2020年 | 9篇 |
2019年 | 14篇 |
2018年 | 12篇 |
2017年 | 14篇 |
2016年 | 15篇 |
2015年 | 9篇 |
2014年 | 9篇 |
2013年 | 27篇 |
2012年 | 16篇 |
2011年 | 22篇 |
2010年 | 20篇 |
2009年 | 23篇 |
2008年 | 18篇 |
2007年 | 23篇 |
2006年 | 16篇 |
2005年 | 15篇 |
2004年 | 17篇 |
2003年 | 14篇 |
2002年 | 22篇 |
2001年 | 14篇 |
2000年 | 9篇 |
1999年 | 10篇 |
1998年 | 22篇 |
1997年 | 20篇 |
1996年 | 17篇 |
1995年 | 18篇 |
1994年 | 11篇 |
1993年 | 8篇 |
1992年 | 7篇 |
1991年 | 6篇 |
1990年 | 5篇 |
1989年 | 7篇 |
1988年 | 4篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1981年 | 5篇 |
1980年 | 6篇 |
1979年 | 4篇 |
1978年 | 3篇 |
1976年 | 3篇 |
1973年 | 2篇 |
1972年 | 3篇 |
1968年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有556条查询结果,搜索用时 15 毫秒
51.
52.
Pamela Rodrigues Passos Severino Natália Ferreira Braga Guilherme Ferreira de Melo Morgado Juliano Marini Orestes Ferro Fábio Roberto Passador Larissa Stieven Montagna 《应用聚合物科学杂志》2021,138(24):50559
Prepreg is a pre-impregnated composite fiber where a thermoset polymer matrix material is present. Before being used, these materials are kept at low temperatures and have a low-density polyethylene (LDPE) film for your protection. The increase in the use of structural composites based on prepregs causes an increase in the amount of protective LDPE film. This material is usually discarded or incinerated and can cause great damage to the environment. Thus, the present work aimed to study the feasibility of recycling up to 100% of protective LDPE (rLDPE) to develop blends-based nanocomposites with rLDPE/virgin LDPE (60/40, 70/30, 80/20, 90/10 and 100/0) with the addition of 5 wt% of compatibilizer agent (maleic anhydride grafted LDPE, LDPE-g-MA), and 1 wt% of bentonite (BNT) using a co-rotational twin-screw extruder, followed by hot pressing in a hydropneumatic press and die-cutting. Water absorption test, thermal aging resistance, morphological characterization by scanning electron microscopy, mechanical properties by Izod impact strength and tensile tests, and differential scanning calorimetry were performed. By the results, it was possible to verify the viability of 100% of the recycling of rLDPE. The results showed a good distribution of 1 wt% of BNT in the matrix, better mechanical properties when compared with virgin LDPE. Furthermore, the thermal properties, water absorption test, and thermal aging resistance showed no statistical differences between the samples. These results confirm the effectiveness and the environmental gain in the use of the recycled material. 相似文献
53.
54.
55.
56.
M. Bechelany A. Brioude P. Stadelmann G. Ferro D. Cornu P. Miele 《Advanced functional materials》2007,17(16):3251-3257
We present a simple process for the fabrication of very long SiC‐based coaxial nanocables (NCs). The versatility of this technique is confirmed by the ability to change the chemical composition of the NC outer layers from silica to carbon and boron nitride. The NCs consist of a SiC core approximately 30 nm in diameter with lengths up to several hundred of nanometers. The thickness of the coating is in the range 2–10 nm. The morphology and structural characterization of the NCs is investigated by scanning electron microscopy (SEM) and high‐resolution transmission electron microscopy (HRTEM), respectively, and their chemical composition is probed by electron energy loss spectroscopy (EELS). A vapor–solid growth mechanism is proposed to explain the growth of SiC‐based NCs of various chemical compositions, depending on the chemical nature of the vapor phase. Because of the large quantity of very long and interlaced NCs produced during the synthesis, the macroscopic aspect of the as‐grown material is like a self‐supported felt. 相似文献
57.
DO Freedman DA Plier A de Almeida J Miranda C Braga MC Maia e Silva J Tang A Furtado 《Canadian Metallurgical Quarterly》1999,162(3):1756-1764
To investigate the hypothesis that T cells recognizing specific Ags localize to the site of disease activity in human bancroftian filariasis, we have compared the repertoire of TCR Vbeta gene segments in lesions vs blood in individual patients by RT-PCR ELISA. Vbeta14 and Vbeta24 were overrepresented (5% greater in tissue compared with PBMCs and/or tissue/PBMC ratios in the highest 5% of all tissue/PBMC ratios for all Vbetas for all subjects) in 50% and 40% of study subjects, respectively. Overrepresentation of these two Vbetas did not occur in any control subject. In comparing three patient groups, the proportion of individuals meeting at least one criterion for Vbeta14 overrepresentation was shown to increase in tandem with our current concepts of disease progression (asymptomatic filariasis = 25%; clinical filariasis with active infection = 60%; clinical filariasis without active infection = 71%). In 6 of the 10 individuals with Vbeta14 overrepresentation, Vbeta14 represented >20% of the entire lesional Vbeta repertoire. All but one of the 20 study subjects had at least one Vbeta gene segment that was overrepresented in tissue compared with PBMCs. Only a small number of Vbetas, usually three or less, were overrepresented in any single filariasis patient. However, in the same tissue, no differences between patient groups were found when IFN-gamma, TNF-alpha, IL-4, IL-5, and IL-12 mRNA expression were examined. Taken together, these findings suggest that, in principle, in essentially all patients, whether with subclinical or with clinical filariasis, distinct and limited T cell populations are concentrated in affected tissue. 相似文献
58.
Simultaneous Flow over and under a Gate 总被引:2,自引:0,他引:2
Vito Ferro 《Canadian Metallurgical Quarterly》2000,126(3):190-193
This paper reports the results of an investigation carried out to establish the stage-discharge relationship for a flow simultaneously discharging over and under a sluice or a broad-crested gate. The stage-discharge relationship is deduced by a theoretical analysis, based on the application of the Π-theorem of the dimensional analysis and the incomplete self-similarity theory, coupled with an experimental investigation carried out by using a laboratory flume. 相似文献
59.
OBJECTIVES: We sought to describe the frequency and location of headache in intracerebral hematoma (ICH) and to analyze its clinical and CT predictors by means of multivariate analysis. BACKGROUND: Headache is more common in intracerebral hemorrhage than in ischemic stroke, and its frequency varies with hematoma location, but the pathophysiologic mechanisms of headache associated with ICH are not fully known. METHODS: We examined a cohort of 289 patients with ICH during a 14-month period in a university hospital. Clinical, including the presence and location of headache, and CT features were collected by two neurologists. RESULTS: One hundred and sixty-five (57%) patients with ICH had a headache at the onset of their stroke. Headache was more common in cerebellar and lobar hemorrhages than in deep ones (thalamic, caudate, capsuloputaminal, brainstem). Headache was also more common in women, patients younger than 70 years, those who vomited, and those with meningeal signs, a Glasgow Coma Scale score < 10, a hematoma volume > 10 ml or CT evidence of intraventricular or subarachnoid bleeding, moderate to severe hydrocephalus, or transtentorial herniation or midline shift. In multiple logistic regression analysis, only meningeal signs (odds ratio [OR] = 2.3), cerebellar or lobar location (OR = 2.1), transtentorial herniation (OR = 1.8), and female gender (OR = 1.6) were significant predictors of headache at the onset of ICH. CONCLUSIONS: Hematoma location, meningeal signs, and gender are more predictive of headache than hematoma volume, suggesting that headache is more often related to the activation of an anatomically distributed system in susceptible individuals and to subarachnoid bleeding than to intracranial hypertension. 相似文献
60.
Growing device‐quality 3C‐SiC monocrystalline material is still an issue despite two decades of work dedicated to the subject. Using silicon as the substrate generates too many defects in the layers, owing to lattice mismatch, while it is very difficult to control the initial nucleation on an α‐SiC substrate so that 60° rotated domains are randomly formed. Herein, the elaboration of mono‐orientated 3C‐SiC layers on a 6H‐SiC(0001) on‐axis, Si face substrate using a vapor–liquid–solid mechanism is reported. This non‐conventional approach for growing monocrystalline layers involves feeding a Ge–Si melt by a propane flux at a temperature ranging from 1250 to 1550 °C. We show that, by using this technique, the 3C‐SiC material is almost always obtained on an hexagonal substrate, even if the crystal seed is oriented 8° off‐axis. Using on‐axis 6H‐SiC seeds and optimal growth conditions results in the reproducible deposition of single‐domain 3C‐SiC layers. A mechanism is proposed to clarify some aspects of this process. 相似文献