全文获取类型
收费全文 | 1397篇 |
免费 | 19篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 14篇 |
综合类 | 4篇 |
化学工业 | 309篇 |
金属工艺 | 18篇 |
机械仪表 | 37篇 |
建筑科学 | 34篇 |
矿业工程 | 10篇 |
能源动力 | 37篇 |
轻工业 | 101篇 |
水利工程 | 16篇 |
石油天然气 | 6篇 |
无线电 | 88篇 |
一般工业技术 | 201篇 |
冶金工业 | 371篇 |
原子能技术 | 16篇 |
自动化技术 | 155篇 |
出版年
2022年 | 14篇 |
2021年 | 9篇 |
2020年 | 7篇 |
2018年 | 15篇 |
2017年 | 16篇 |
2015年 | 16篇 |
2014年 | 22篇 |
2013年 | 57篇 |
2012年 | 37篇 |
2011年 | 52篇 |
2010年 | 41篇 |
2009年 | 46篇 |
2008年 | 51篇 |
2007年 | 47篇 |
2006年 | 47篇 |
2005年 | 39篇 |
2004年 | 32篇 |
2003年 | 30篇 |
2002年 | 40篇 |
2001年 | 33篇 |
2000年 | 21篇 |
1999年 | 27篇 |
1998年 | 63篇 |
1997年 | 46篇 |
1996年 | 45篇 |
1995年 | 28篇 |
1994年 | 30篇 |
1993年 | 31篇 |
1992年 | 24篇 |
1991年 | 21篇 |
1990年 | 35篇 |
1989年 | 34篇 |
1988年 | 35篇 |
1987年 | 22篇 |
1986年 | 20篇 |
1985年 | 24篇 |
1984年 | 20篇 |
1983年 | 16篇 |
1982年 | 22篇 |
1981年 | 27篇 |
1980年 | 15篇 |
1979年 | 11篇 |
1978年 | 18篇 |
1977年 | 14篇 |
1976年 | 22篇 |
1975年 | 13篇 |
1974年 | 13篇 |
1973年 | 17篇 |
1972年 | 7篇 |
1971年 | 8篇 |
排序方式: 共有1417条查询结果,搜索用时 0 毫秒
51.
Safety Evaluation of Green Tea Polyphenols Consumption in Middle‐aged Ovariectomized Rat Model 下载免费PDF全文
Chwan‐Li Shen Gordon Brackee Xiao Song Michael D. Tomison VelvetLee Finckbone Kelly T. Mitchell Lili Tang Ming‐Chien Chyu Dale M. Dunn Jia‐Sheng Wang 《Journal of food science》2017,82(9):2192-2205
This work evaluates chronic safety in middle‐aged ovariectomized rats supplemented with different dosages of green tea polyphenols (GTP) in drinking water. The experiment used 6‐mo‐old sham (n = 39) and ovariectomized (OVX, n = 143) female rats. All sham (n = 39) and 39 of the OVX animals received no GTP treatment and their samples were collected for outcome measures at baseline, 3 mo, and 6 mo (n = 13 per group for each). The remaining OVX animals were randomized into 4 groups receiving 0.15%, 0.5%, 1%, and 1.5% (n = 26 for each) of GTP (wt/vol), respectively, in drinking water for 3 and 6 mo. No mortality or abnormal treatment‐related findings in clinical observations or ophthalmologic examinations were noted. No treatment‐related macroscopic or microscopic findings were noted for animals administered 1.5% GTP supplementation. Throughout the study, there was no difference in the body weight among all OVX groups. In all OVX groups, feed intake and water consumption significantly decreased with GTP dose throughout the study period. At 6 mo, GTP intake did not affect hematology, clinical chemistry, and urinalysis, except for phosphorus and blood urea nitrogen (increased), total cholesterol, lactate dehydrogenase, and urine pH (decreased). This study reveals that the no‐observed‐adverse‐effect level (NOAEL) of GTP is 1.5% (wt/vol) in drinking water, the highest dose used in this study. 相似文献
52.
53.
Kimberly Sturk-Andreaggi Joseph D. Ring Adam Ameur Ulf Gyllensten Martin Bodner Walther Parson Charla Marshall Marie Allen 《International journal of molecular sciences》2022,23(4)
Whole-genome sequencing (WGS) data present a readily available resource for mitochondrial genome (mitogenome) haplotypes that can be utilized for genetics research including population studies. However, the reconstruction of the mitogenome is complicated by nuclear mitochondrial DNA (mtDNA) segments (NUMTs) that co-align with the mtDNA sequences and mimic authentic heteroplasmy. Two minimum variant detection thresholds, 5% and 10%, were assessed for the ability to produce authentic mitogenome haplotypes from a previously generated WGS dataset. Variants associated with NUMTs were detected in the mtDNA alignments for 91 of 917 (~8%) Swedish samples when the 5% frequency threshold was applied. The 413 observed NUMT variants were predominantly detected in two regions (nps 12,612–13,105 and 16,390–16,527), which were consistent with previously documented NUMTs. The number of NUMT variants was reduced by ~97% (400) using a 10% frequency threshold. Furthermore, the 5% frequency data were inconsistent with a platinum-quality mitogenome dataset with respect to observed heteroplasmy. These analyses illustrate that a 10% variant detection threshold may be necessary to ensure the generation of reliable mitogenome haplotypes from WGS data resources. 相似文献
54.
Dale L. Muccignat Peter W. Stokes Daniel G. Cocks Jason R. Gascooke Darryl B. Jones Michael J. Brunger Ronald D. White 《International journal of molecular sciences》2022,23(6)
The extraction of electron–liquid phase cross-sections (surface and bulk) is proposed through the measurement of (differential) energy loss spectra for electrons scattered from a liquid micro-jet. The signature physical elements of the scattering processes on the energy loss spectra are highlighted using a Monte Carlo simulation technique, originally developed for simulating electron transport in liquids. Machine learning techniques are applied to the simulated electron energy loss spectra, to invert the data and extract the cross-sections. The extraction of the elastic cross-section for neon was determined within 9% accuracy over the energy range 1–100 eV. The extension toward the simultaneous determination of elastic and ionisation cross-sections resulted in a decrease in accuracy, now to within 18% accuracy for elastic scattering and 1% for ionisation. Additional methods are explored to enhance the accuracy of the simultaneous extraction of liquid phase cross-sections. 相似文献
55.
Epitaxially grown GaAs planar doped barrier diodes have been designed and fabricated into coplanar structures specifically for millimetre-wave zero-bias detector applications. Results at 35 GHz and 94 GHz show that the tangential sensitivity, voltage sensitivity and dynamic range of these devices can significantly exceed those of any comparable Schottky diode detector. This is the first report of such a result.<> 相似文献
56.
Levels and distribution of polybrominated diphenyl ethers in water, surface sediments, and bivalves from the San Francisco Estuary 总被引:5,自引:0,他引:5
Polybrominated diphenyl ethers (PBDEs) were found in water, surface sediments, and bivalve samples that were collected from the San Francisco Estuary in 2002. sigmaPBDE concentrations in water samples ranged from 3 to 513 pg/ L, with the highest concentrations found in the Lower South Bay (range 103-513 pg/L) region, which receives approximately 26% of the Estuary's wastewater treatment plant effluents. The sigmaPBDEs in sediments ranged from below detection limits to 212 ng/g dry wt, with the highest concentration found at a South Bay station (212 ng/g dry wt), which was up to 3 orders of magnitude higher than other stations. The sigmaPBDE concentrations ranged from 9 to 64 ng/g dry wt in oysters (Crassostrea gigas), from 13 to 47 ng/g dry wt in mussels (Mytilus californianus), and from 85 to 106 ng/g dry wt in clams (Corbicula fluminea). Only three PBDE congeners were detected in bivalves, BDE-47, BDE-99, and BOE-100; these are the most bioaccumulative congeners from the commercial Penta-BDE mixture. 相似文献
57.
58.
Venkatesh Balan Chad A. Rogers Shishir P. S. Chundawat Leonardo da Costa Sousa Patricia J. Slininger Rajesh Gupta Bruce E. Dale 《Journal of the American Oil Chemists' Society》2009,86(2):157-165
We have come up with a novel, integrated approach for making biodiesel by in-house producion of ethanol after fermentation
of hexane extracted edible oil cake fiber. In addition, we have demonstrated how ethanol could be manufactured from commonly
available oil cakes (such as canola, sunflower, sesame, soy, peanut) and dried distiller’s grains with solubles (DDGS). The
edible oil cakes and DDGS were hexane extracted, ammonia fiber expansion pretreated, enzymatically hydrolysed and fermented
to produce ethanol. From all the oil cakes tested in this work, DDGS and peanut oil cake showed the most promising results
giving more than 180 g of glucose/kg of oil cake. These two feedstock’s were hydrolyzed at 15% solids loading and fermented
by a native strain of Pichia stipitis. Most sugars were consumed during the first 24 h, with no pronounced inhibition of P. stipitis by the degradation products in the hydrolysate. Xylose consumption was more effective for peanut cake hydrolyzate compared
to DDGS. 相似文献
59.
Processing, Microstructure, and Wear Behavior of Silicon Nitride Hot-Pressed with Alumina and Yttria 总被引:3,自引:0,他引:3
Ajoy Zutshi Richard A. Haber Dale E. Niesz Jane W. Adams John B. Wachtman Mattison K. Ferber Stephen M. Hsu 《Journal of the American Ceramic Society》1994,77(4):883-890
Commercial silicon nitride powder with A12 O3 and Y2 O3 additives was hot-pressed to complete density. The resulting microstructure contained elongated grains with no trace of remaining α-Si3 N4 . The aspect ratio of the elongated grains increased with increasing soak time at a fixed hot-pressing temperature. X-ray diffraction analysis showed that the crystalline phase in the hot-pressed samples was β-sialon (Si6−z Alz Oz N8−z ) with z values that increased with soak time. The fracture strength and fracture toughness of the samples increased as the aspect ratio of the grains increased. The Vickers hardness decreased slightly as the soak time was increased, which was attributed to a grain size effect. Wear tests of silicon nitride against silicon nitride were conducted on a reciprocating pin-on-disk apparatus with paraffin oil as a lubricant. Correlation studies of wear with microstructure and mechanical properties were performed. The wear rate increased rapidly with increasing soak time in spite of the increased strength and toughness. This was attributed to increased third-body wear caused by pullout of pieces from the wear surface. The pullout mechanism was not conclusively identified. However, TEM examination showed clear evidence of dislocation motion under the wear scar. Grain boundary microstresses caused by the anisotropic thermal expansion and elastic properties of the elongated grains may have contributed to the observed pullout. 相似文献
60.
Practitioners and researchers need to stay up-to-date with the latest advances in their fields, but the continual growth in the amount of literature available makes this task increasingly difficult. In this article, we describe the Citation-Sensitive In-Browser Summariser (CSIBS), a new research tool to help manage the literature browsing task. The design of CSIBS was based on a user requirements analysis which identified the information needs that biomedical researchers commonly encounter when browsing through academic literature. CSIBS supports researchers in their browsing tasks by presenting both a generic and a tailored preview about a citation at the point at which they encounter it. This information is aimed at helping the reader determine whether or not to invest the time in exploring the cited article further, thus alleviating information overload. Feedback from biomedical researchers indicates that CSIBS facilitates this relevance judgement task, and that the interface and previews are informative and easy to use. 相似文献