全文获取类型
收费全文 | 2796篇 |
免费 | 11篇 |
专业分类
电工技术 | 12篇 |
化学工业 | 68篇 |
金属工艺 | 8篇 |
机械仪表 | 15篇 |
建筑科学 | 34篇 |
能源动力 | 13篇 |
轻工业 | 34篇 |
水利工程 | 4篇 |
石油天然气 | 1篇 |
无线电 | 154篇 |
一般工业技术 | 90篇 |
冶金工业 | 2315篇 |
原子能技术 | 2篇 |
自动化技术 | 57篇 |
出版年
2022年 | 5篇 |
2021年 | 7篇 |
2020年 | 6篇 |
2018年 | 7篇 |
2017年 | 9篇 |
2016年 | 9篇 |
2014年 | 13篇 |
2013年 | 21篇 |
2012年 | 18篇 |
2011年 | 26篇 |
2010年 | 19篇 |
2009年 | 17篇 |
2008年 | 31篇 |
2007年 | 21篇 |
2006年 | 28篇 |
2005年 | 18篇 |
2004年 | 25篇 |
2003年 | 18篇 |
2002年 | 23篇 |
2001年 | 24篇 |
2000年 | 15篇 |
1999年 | 83篇 |
1998年 | 693篇 |
1997年 | 399篇 |
1996年 | 252篇 |
1995年 | 172篇 |
1994年 | 128篇 |
1993年 | 154篇 |
1992年 | 26篇 |
1991年 | 37篇 |
1990年 | 36篇 |
1989年 | 43篇 |
1988年 | 26篇 |
1987年 | 28篇 |
1986年 | 30篇 |
1985年 | 27篇 |
1984年 | 8篇 |
1983年 | 7篇 |
1982年 | 17篇 |
1981年 | 26篇 |
1980年 | 30篇 |
1979年 | 5篇 |
1978年 | 6篇 |
1977年 | 59篇 |
1976年 | 100篇 |
1975年 | 7篇 |
1974年 | 9篇 |
1972年 | 4篇 |
1971年 | 4篇 |
1966年 | 5篇 |
排序方式: 共有2807条查询结果,搜索用时 17 毫秒
81.
Reliability-Based Design for Internal Stability of Mechanically Stabilized Earth Walls 总被引:1,自引:0,他引:1
A parametric study was conducted using Monte Carlo simulation to assess how uncertainty in design parameters affects the probability of internal failure of mechanically stabilized earth (MSE) walls. Bishop’s simplified method was used to conduct the internal stability analyses. The results of the analyses indicate that the mean and coefficient of variation of the backfill friction angle, mean and coefficient of variation of the tensile strength of reinforcement, mean unit weight of the backfill, mean surcharge, mean reinforcement vertical spacing, and mean reinforcement length have a significant effect on the probability of internal failure of MSE walls. Based on the results of the parametric study, a series of additional simulations were conducted where the significant parameters were varied over a broad range. The results of these simulations were used to develop a set of reliability-based design (RBD) charts for internal stability of MSE walls. A method to adapt these charts to address model bias and model uncertainty is also presented. A MSE wall was designed using the RBD method and two other deterministic design methods. The required tensile strength of the reinforcement obtained from the RBD method fell between the strengths determined from the deterministic methods. 相似文献
82.
The effects of blow-molding process variables on the environmental stress crack resistance (ESCR) of high-density polyethylene (HDPE) bottles were studied. Experimental design was employed to test the effect of die temperature, mold temperature, molding time, and drop time. Bottles blown at each condition were tested using the internal pressure ESCR test. Through the use of regression analysis, the effect of each variable was quantified. Increasing die temperature, mold temperature, or molding time decreased ESCR. However, increasing drop time increased ESCR. 相似文献
83.
Freshly collectedCalanus pacificus were maintained in sea water containing 25 μCi/ml [32P]orthophosphate or 1 μCi/ml [14C]acetate at 10 C for 24 hr. The animals took up label from the environment and incorporated it into various lipid fractions.
After incubation with [14C]acetate the order of specific activity of the different lipid classes was: phospholipids > free fatty acids > wax esters
> triglycerides. Argentation thin layer chromatography of the fatty acid methyl esters showed that ca. 50% of the activity
was in saturated fatty acids and 34% in polyunsaturated acids. When the animals were exposed to [32P]orthophosphate, lysophosphatidyl choline became most heavily labeled, followed by lysophosphatidyl ethanolamine, sphingomyelin,
phosphatidyl ethanolamine, and phosphatidyl choline. Comparison of the data obtained with those available for decapods and
mammals revealed striking similarities between these phylogenetically distant groups. It is believed that labeling the lipids
of marine and freshwater planktonic crustaceans in this way will provide much information about the metabolism of lipids in
these organisms. 相似文献
84.
M. Jaime-Vasquez R.N. Jacobs C. Nozaki J.D. Benson L.A. Almeida J. Arias J. Pellegrino 《Journal of Electronic Materials》2012,41(10):2975-2980
We present the results of a detailed study of the changes that occur on CdTe buffer layer surfaces grown on ZnTe/Si(211) and GaAs(211)B during the routine thermal cyclic annealing (TCA) process. Observations indicate that CdTe buffer layer surfaces are Te saturated when the TCA is performed under Te overpressure. In the absence of Te flux during the TCA step, the CdTe surface loses CdTe congruently and the typical CdTe nanowires show the presence of nodules on their surfaces. The observed changes in reflection high-energy electron diffraction patterns during TCA are explained in terms of surface chemistry and topography observations. Overall, the Te overpressure is necessary to maintain a smoother and pristine surface to continue the molecular beam epitaxy (MBE) growth. 相似文献
85.
E. P. G. Smith G. M. Venzor M. D. Newton M. V. Liguori J. K. Gleason R. E. Bornfreund S. M. Johnson J. D. Benson A. J. Stoltz J. B. Varesi J. H. Dinan W. A. Radford 《Journal of Electronic Materials》2005,34(6):746-753
Inductively coupled plasma (ICP) using hydrogen-based gas chemistry has been developed to meet requirements for deep HgCdTe
mesa etching and shallow CdTe passivation etching in large format HgCdTe infrared focal plane array (FPA) fabrication. Large
format 2048×2048, 20-μm unit-cell short wavelength infrared (SWIR) and 2560×512, 25-μm unit-cell midwavelength infrared (MWIR)
double-layer heterojunction (DLHJ) p-on-n HgCdTe FPAs fabricated using ICP processing exhibit >99% pixel operability. The
HgCdTe FPAs are grown by molecular beam epitaxy (MBE) on Si substrates with suitable buffer layers. Midwavelength infrared
detectors fabricated from 4-in. MBE-grown HgCdTe/Si substrates using ICP for mesa delineation and CdTe passivation etching
demonstrate measured spectral characteristics, RoA product, and quantum efficiency comparable to detectors fabricated using
wet chemical processes. Mechanical samples prepared to examine physical characteristics of ICP reveal plasma with high energy
and low ion angle distribution, which is necessary for fine definition, high-aspect ratio mesa etching with accurate replication
of photolithographic mask dimensions. 相似文献
86.
J. D. Benson L. O. Bubulac P. J. Smith R. N. Jacobs J. K. Markunas M. Jaime-Vasquez L. A. Almeida A. Stoltz P. S. Wijewarnasuriya G. Brill Y. Chen J. Peterson M. Reddy M. F. Vilela S. M. Johnson D. D. Lofgreen A. Yulius G. Bostrup M. Carmody D. Lee S. Couture 《Journal of Electronic Materials》2014,43(11):3993-3998
State-of-the-art (112)B CdZnTe substrates were examined for near-surface tellurium precipitate-related defects. The Te precipitate density was observed to be fairly uniform throughout the bulk of the wafer, including the near-surface region. After a molecular beam epitaxy (MBE) preparation etch, exposed Te precipitates, small pits, and bumps on the (112)B surface of the CdZnTe wafer were observed. From near-infrared and dark field microscopy, the bumps and small pits on the CdZnTe surface are associated with strings of Te precipitates. Raised bumps are Te precipitates near the surface of the (112)B CdZnTe where the MBE preparation etch has not yet exposed the Te precipitate(s). An exposed Te precipitate sticking above the etched CdZnTe surface plane occurs when the MBE preparation etch rapidly undercuts a Te precipitate. Shallow surface pits are formed when the Te precipitate is completely undercut from the surrounding (112)B surface plane. The Te precipitate that was previously located at the center of the pit is liberated by the MBE preparation etch process. 相似文献
87.
M. Reddy D. D. Lofgreen K. A. Jones J. M. Peterson W. A. Radford J. D. Benson S. M. Johnson 《Journal of Electronic Materials》2013,42(11):3114-3118
HgCdTe dual-band mid-wave infrared/long-wave infrared focal-plane arrays on CdZnTe are a key component in advanced electrooptic sensor applications. Molecular beam epitaxy (MBE) has been used successfully for growth of dual-band layers on larger CdZnTe substrates. However, the macrodefect density, which is known to reduce the pixel operability and its run-to-run variation, is larger when compared with layers grown on Si substrate. This paper reports the macrodefect density versus size signature of a well-optimized MBE dual-band growth and a cross-sectional study of a macrodefect that represents the most prevalent class using focused ion beam, scanning transmission electron microscopy, and energy-dispersive x-ray spectroscopy. The results show that the macrodefect originates from a void, which in turn is associated with a pit on the CdZnTe substrate. 相似文献
88.
Inductively coupled plasma (ICP) processing has become the industrial processing standard for HgCdTe and its related II–VI
compounds. In this study ICP processes were developed that allow several microns of HgCdTe to be plasma etched while maintaining
a low root-mean-square (RMS) roughness, and even improving the surface roughness in the case of HgCdTe-on-Si. These ICP processes
are superior to older electron cyclotron resonance (ECR) plasma etches. The resulting ICP plasma processed surfaces are oxygen
and carbon free, have a good reflection high-energy electron diffraction (RHEED) pattern, and have only a small amount of
mercury depletion, x = 0.22 to 0.47 (where x is the ratio of Cd to␣Hg), in the first 25 ? to 30 ? of the HgCdTe. Nanofeatures of the as-grown HgCdTe are retained during
the process and are believed to be indicative of the fundamental defect mechanisms in the different HgCdTe etched surfaces.
Results from these experiments strongly suggest that ICP plasma processes can be used to delineate pixels, etch vias, clean
surfaces, and even produce epi-ready surfaces that would allow HgCdTe to become much more manufacturable, and perhaps allow
the replacement of wet processing in HgCdTe. 相似文献
89.
90.