全文获取类型
收费全文 | 2842篇 |
免费 | 105篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 12篇 |
综合类 | 1篇 |
化学工业 | 572篇 |
金属工艺 | 19篇 |
机械仪表 | 36篇 |
建筑科学 | 147篇 |
矿业工程 | 5篇 |
能源动力 | 60篇 |
轻工业 | 337篇 |
水利工程 | 23篇 |
石油天然气 | 5篇 |
无线电 | 136篇 |
一般工业技术 | 401篇 |
冶金工业 | 905篇 |
原子能技术 | 2篇 |
自动化技术 | 288篇 |
出版年
2023年 | 19篇 |
2022年 | 68篇 |
2021年 | 77篇 |
2020年 | 39篇 |
2019年 | 46篇 |
2018年 | 67篇 |
2017年 | 65篇 |
2016年 | 49篇 |
2015年 | 59篇 |
2014年 | 66篇 |
2013年 | 146篇 |
2012年 | 130篇 |
2011年 | 175篇 |
2010年 | 124篇 |
2009年 | 146篇 |
2008年 | 134篇 |
2007年 | 133篇 |
2006年 | 126篇 |
2005年 | 116篇 |
2004年 | 98篇 |
2003年 | 80篇 |
2002年 | 101篇 |
2001年 | 50篇 |
2000年 | 61篇 |
1999年 | 65篇 |
1998年 | 47篇 |
1997年 | 45篇 |
1996年 | 62篇 |
1995年 | 49篇 |
1994年 | 49篇 |
1993年 | 43篇 |
1992年 | 43篇 |
1991年 | 11篇 |
1990年 | 31篇 |
1989年 | 36篇 |
1988年 | 28篇 |
1987年 | 30篇 |
1986年 | 27篇 |
1985年 | 20篇 |
1984年 | 29篇 |
1983年 | 24篇 |
1982年 | 26篇 |
1981年 | 19篇 |
1980年 | 14篇 |
1979年 | 12篇 |
1978年 | 8篇 |
1977年 | 7篇 |
1976年 | 8篇 |
1975年 | 9篇 |
1974年 | 8篇 |
排序方式: 共有2949条查询结果,搜索用时 15 毫秒
41.
The incidence and mortality of pancreas cancer converge. There has been little advancement in the treatment of pancreas cancer since the acceptance of gemcitabine as the standard therapy. Unfortunately, the efficacy of gemcitabine is dismal. While there is much discussion for the development of biomarkers to help direct therapy in this area, there is little action to move them into clinical practice. Herein, we review potential pancreatic cancer biomarkers and discuss the limitations in their implementation. 相似文献
42.
De Vico L Iversen L Sørensen MH Brandbyge M Nygård J Martinez KL Jensen JH 《Nanoscale》2011,3(9):3635-3640
A single charge screening model of surface charge sensors in liquids (De Vico et al., Nanoscale, 2011, 3, 706-717) is extended to multiple charges to model the effect of the charge distributions of analyte proteins on FET sensor response. With this model we show that counter-intuitive signal changes (e.g. a positive signal change due to a net positive protein binding to a p-type conductor) can occur for certain combinations of charge distributions and Debye lengths. The new method is applied to interpret published experimental data on Streptavidin (Ishikawa et al., ACS Nano, 2009, 3, 3969-3976) and Nucleocapsid protein (Ishikawa et al., ACS Nano, 2009, 3, 1219-1224). 相似文献
43.
Supplementary cementitious materials 总被引:3,自引:0,他引:3
The use of silica rich SCMs influences the amount and kind of hydrates formed and thus the volume, the porosity and finally the durability of these materials. At the levels of substitution normally used, major changes are the lower Ca/Si ratio in the C–S–H phase and consumption of portlandite. Alumina-rich SCMs increase the Al-uptake in C–S–H and the amounts of aluminate containing hydrates. In general the changes in phase assemblages are well captured by thermodynamic modelling, although better knowledge of the C–S–H is needed.At early ages, “filler” effects lead to an increased reaction of the clinker phases. Reaction of SCMs starts later and is enhanced with pH and temperature. Composition, fineness and the amount of glassy phase play also an important role. Due to the diverse range of SCM used, generic relations between composition, particle size, exposure conditions as temperature or relative humidity become increasingly crucial. 相似文献
44.
There have been significant advances in the understanding of wet granulation processes. Foam granulation is the latest development and an emerging area of interest for pharmaceutical manufacturing.Single foam penetration experiments were carried out on static powder beds, followed by short-nucleation experiments (where nuclei are formed by a nucleation-only mechanism) and full foam granulation experiments (where nucleation, growth and breakage are occurring simultaneously). All experiments were performed with lactose monohydrate powder using a 5 L high shear mixer–granulator. The foam penetration/dispersion behaviour was examined and the granule size distributions were investigated as a function of foam quality (83–97% FQ), impeller speed (105–515 rpm) and wet massing period (0–4 min).Nucleation in foam granulation is postulated to undergo either “foam drainage” or “mechanical dispersion” controlled mechanisms. For “foam drainage” mechanism, the foam penetrates the powder bed to form coarse and broad granule size distributions. For “mechanical dispersion” mechanism, the wetting and nucleation conditions are governed by the powder mixing conditions and similar granule size distributions are produced. Regardless of the mechanism, the initial wetting and nucleation behaviour controls the initial nuclei size distribution, and this initial distribution is retained in the final granule size distribution. This work demonstrated the critical importance of the nucleation and binder distribution in determining the granule size distributions for foam granulation process. 相似文献
45.
A diesel particulate filter (DPF) is used to remove particulate matter (PM) from the diesel engine exhaust. The accumulated PM is periodically removed by combustion, which sometimes leads to excessive temperature excursions that melt the ceramic filter. This behavior cannot be explained by operation under stationary feed conditions. We propose that these temperature excursions are a dynamic effect following a rapid change in the driving mode while the DPF is being regenerated. Specifically, a rapid decrease in the exhaust temperature can lead to a counterintuitive large transient temperature rise above that which would exist under a higher stationary feed temperature. This unexpected behavior is similar to the well‐known wrong‐way behavior in packed‐bed reactors, even though the axial‐dependent flow through the filter in a DPF is rather different from the constant axial flow through a packed bed. We present simulations that provide insight about the dependence of the amplitude of this wrong‐way temperature rise on the filtration velocity, the PM loading, dimensions of the DPF, and the amplitude of the rapid temperature decrease and when it occurs after the start of the regeneration. The insight provided by these simulations will help develop operation and control protocols that circumvent or at least decrease the probability of the occurrence of the destructive melting of the DPF. © 2010 American Institute of Chemical Engineers AIChE J, 2011 相似文献
46.
The degradation mechanisms of cementitious materials exposed to sulfate solutions have been controversial, despite considerable research. In this paper, two methodologies of image analysis based on scanning electron microscope and chemical mapping are used to analyse Portland cement mortars exposed to sodium sulfate solution. The effects of sulfate concentration in solution and water to cement ratio of mortar, which are considered as the most sensitive factors to sulfate attack, are investigated respectively by comparing the macro expansion with microstructure analysis. It is found that the sulfate concentration in pore solution, expressed as sulfate content in C-S-H, plays a critical role on the supersaturation with respect to ettringite and so on the expansion force generated. 相似文献
47.
Karen De Clerck Hubert Rahier Bruno Van Mele Philippe Westbroek Paul Kiekens 《应用聚合物科学杂志》2007,106(3):1648-1658
Dye–fiber interactions are studied in poly (ethylene terephthalate) fibers by FT‐IR spectroscopy. It is shown for the first time that DRIFTS (diffuse reflectance infrared Fourier transform spectroscopy) serves as an easy applicable and accurate technique for the study of fibrous structures. This article focuses on the possible hydrogen bond interactions in the dye–fiber system, where the PET fibers are dyed with anthraquinone‐based disperse dyes. The dyes and related anthraquinone structures are studied in both the dilute solution state, the solid state, and as present in the PET fibers. It is proven that 1‐amino anthraquinones show strong “chelate‐type” intramolecular hydrogen bonding in all three states. In the fibers an important supplementary intermolecular hydrogen bonding with the C?O groups in the PET fiber is observed. The extend of hydrogen bonding seems to be prone to dye concentration variations. Further analysis by modulated differential scanning calorimetry links the hydrogen bonding to an intrinsic plasticizing effect of the dyes affecting the dye diffusion process. This thus offers a tool for the fundamental understanding of the dyeing process and possible observed differences in dyeing behavior in dye–fiber systems. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 相似文献
48.
Since the discovery of Metal Organic Frameworks (MOFs) in the early 1990s, the amount of new structures has grown exponentially. A MOF typically consists of inorganic nodes that are connected by organic linkers to form crystalline, highly porous structures. MOFs have attracted a lot of attention lately, as the versatile design of such materials holds promises of interesting applications in various fields. In this review, we will focus on the use of MOFs as heterogeneous oxidation catalysts. MOFs are very promising candidates to replace homogeneous catalysts by sustainable and stable heterogeneous catalysts.
The catalytic active function can be either the active metal sites of the MOF itself or can be introduced as an extra functionality in the linker, a dopant or a “ship-in-a-bottle” complex. As the pore size, pore shape, and functionality of MOFs can be designed in numerous ways, shape selectivity, and even chiral selectivity can be created. In this article, we will present an overview on the state of the art of the use of MOFs as a heterogeneous catalyst in liquid phase oxidation reactions. 相似文献
49.
Mladen Ladika Thomas H. Kalantar Hui Shao Stacey L. Dean J. Keith Harris Paul J. Sheskey Karen Coppens Karen M. Balwinski Debora L. Holbrook 《应用聚合物科学杂志》2014,131(7)
Polyampholyte latexes can exist within a certain pH range as low‐viscosity aqueous dispersions, while upon a pH shift to the vicinity of the isoelectric point they undergo ionic coacervation. Three classes of coacervation latexes were synthesized and evaluated for their suitability for use in tablet coating applications. Pharmaceutical tablet coatings are commonly based on hydroxypropyl methyl cellulose, poly(vinyl alcohol), and acrylic polymers. Because of the high viscosity of their aqueous solutions, and to the consequent required low concentrations of the tablet coating polymers in the coating solutions to enable sufficiently low viscosity for effective spray application, the current commercial pharmaceutical tablet coating technology requires the removal of large amounts of water during the manufacturing process. In this work, films prepared from high‐solids, low‐viscosity coacervated acrylic latexes showed good hardness, very low tackiness, an excellent combination of optical properties, and very low water vapor permeability. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40049. 相似文献
50.
Zn in Athenian Black Gloss Ceramic Slips: A Trace Element Marker for Fabrication Technology 下载免费PDF全文
Marc Walton Karen Trentelman Ilaria Cianchetta Jeffrey Maish David Saunders Brendan Foran Apurva Mehta 《Journal of the American Ceramic Society》2015,98(2):430-436
The black‐colored pottery slips produced in Athens from the 6th to 4th centuries B.C., had a consistent composition achieved through processing and refinement of raw clay. Little direct evidence has been established as to what were these refinement methods. To better understand how the slip material was prepared, the major and trace elemental compositions of 19 slips from different ceramic vessels and their corresponding bodies of Athenian red‐figure and black‐figure vases were determined using laser ablation inductively coupled plasma mass spectrometry (LA‐ICPMS). Notably higher Zn concentrations were found in the slips (271–1959 ppm) than in their corresponding body ceramics (<361 ppm). The Zn concentrations in the slips were also found to be above the natural background for typical clay (between 10 and 300 ppm) suggesting an unintentional anthropogenic enrichment of this metal. Based on the abnormally high Zn content of the slip, it is speculated that the clay was treated using vitriol (concentrated acid mine runoff which is rich in Zn), to induce flocculation and remove carbonate mineral phases from the raw material that, if present, would prevent the slip from vitrifying. This same signature of elevated levels of Zn with a corresponding Ce anomaly is also observed for black glosses produced in Corinthian and Etrurian (Italy) workshops indicating that these trace element signatures were imparted to the material by means of shared methods of manufacturing instead of being indicative of a single unique source for this material. 相似文献