全文获取类型
收费全文 | 1631篇 |
免费 | 54篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 13篇 |
化学工业 | 345篇 |
金属工艺 | 101篇 |
机械仪表 | 21篇 |
建筑科学 | 98篇 |
矿业工程 | 3篇 |
能源动力 | 56篇 |
轻工业 | 174篇 |
水利工程 | 8篇 |
石油天然气 | 2篇 |
无线电 | 158篇 |
一般工业技术 | 235篇 |
冶金工业 | 233篇 |
原子能技术 | 8篇 |
自动化技术 | 231篇 |
出版年
2023年 | 7篇 |
2022年 | 11篇 |
2021年 | 26篇 |
2020年 | 19篇 |
2019年 | 25篇 |
2018年 | 26篇 |
2017年 | 40篇 |
2016年 | 52篇 |
2015年 | 33篇 |
2014年 | 48篇 |
2013年 | 94篇 |
2012年 | 71篇 |
2011年 | 75篇 |
2010年 | 67篇 |
2009年 | 66篇 |
2008年 | 59篇 |
2007年 | 53篇 |
2006年 | 57篇 |
2005年 | 77篇 |
2004年 | 59篇 |
2003年 | 82篇 |
2002年 | 46篇 |
2001年 | 30篇 |
2000年 | 31篇 |
1999年 | 40篇 |
1998年 | 78篇 |
1997年 | 57篇 |
1996年 | 37篇 |
1995年 | 23篇 |
1994年 | 29篇 |
1993年 | 37篇 |
1992年 | 13篇 |
1991年 | 15篇 |
1990年 | 12篇 |
1989年 | 11篇 |
1988年 | 13篇 |
1987年 | 8篇 |
1986年 | 9篇 |
1985年 | 18篇 |
1984年 | 14篇 |
1983年 | 14篇 |
1982年 | 7篇 |
1981年 | 7篇 |
1980年 | 6篇 |
1979年 | 10篇 |
1978年 | 8篇 |
1977年 | 12篇 |
1976年 | 16篇 |
1975年 | 9篇 |
1974年 | 7篇 |
排序方式: 共有1686条查询结果,搜索用时 15 毫秒
71.
J Haydersah I Chevallier I Rochette C Mouquet-Rivier C Picq T Marianne-Pépin C Icard-Vernière JP Guyot 《Journal of food science》2012,77(8):M466-M472
The potential of tropical starchy plants such as plantain (Musa paradisiaca), breadfruit (Artocarpus communis), and sweet potato (Ipomoea batatas) for the development of new fermented foods was investigated by exploiting the capacity of some lactic acid bacteria to hydrolyze starch. The amylolytic lactic acid bacteria (ALAB) Lactobacillus plantarum A6 and Lactobacillus fermentum Ogi E1 were able to change the consistency of thick sticky gelatinized slurries of these starchy fruits and tubers into semiliquid to liquid products. Consequently, a decrease in apparent viscosity and an increase in Bostwick flow were observed. These changes and the production of maltooligosaccharides confirmed starch hydrolysis. Sucrose in sweet potato was not fermented by strain A6 and poorly fermented by strain Ogi E1, suggesting possible inhibition of sucrose fermentation. In all 3 starchy plants, rapidly digestible starch (RDS) was higher than slowly digestible starch (SDS) and resistant starch (RS) represented between 17% and 30% dry matter (DM). The digestibility of plantain was not affected by fermentation, whereas the RDS content of breadfruit and sweet potato decreased and the RS content increased after fermentation. Practical Application: The characteristics resulting from different combinations of gluten free starchy plants (plantain, breadfruit, sweet potato) and amylolytic lactic acid bacteria (ALAB) offer opportunities to develop new functional fermented beverages, mainly for breadfruit and sweet potato, after further investigation of their formulation, sensory attributes, nutritional, and prebiotic characteristics. 相似文献
72.
73.
Hanne Boskov Hansen Claus V Rasmussen Knud Erik Bach Knudsen se Hansen 《Journal of the science of food and agriculture》2003,83(1):76-85
The aim of this study was to measure the variation in dietary fibre (DF) content and composition among different rye varieties grown in the same location in three successive years and to estimate the contributions of genotype and harvest year to this variation. The study included grain from 19 different varieties of rye, of which seven varieties were analysed in all three years. The content of total DF in all samples ranged from 147 to 209 g kg?1 dry matter (dm), with 34–66 g kg?1 being water‐extractable (WE) DF and 108–159 g kg?1 being water‐unextractable (WUE) DF. The main DF component was arabinoxylan (AX) with a content of 80–121 g kg?1 dm, of which 26–41 g kg?1 dm was WE AX. The ratio of arabinose to xylose (ara/xyl) of total AX ranged from 0.59 to 0.69. The content of β‐glucan was 13–22 g kg?1 dm and that of fructan was 45–64 g kg?1 dm. Analysis of the data from seven varieties and three harvest years showed a highly significant influence of harvest year on most DF components. Significant genotype effects were found for the contents of total DF, total AX, β‐glucan and fructan and for the ara/xyl ratio of total and WUE AX. Estimation of variance components showed that yearly variations in the contents of total DF, total AX, WUE DF, WUE AX and β‐glucan were generally higher (27–55% of total variance) than genotype effects (14–19%). The ara/xyl ratio of total and WUE AX showed a high influence of genotype (46 and 43% respectively). Non‐adapted rye varieties with small kernel size had the highest contents of total DF and total AX. The content of β‐glucan was positively correlated with kernel weight (r = 0.68), whereas no overall correlation was found between kernel size and the content of DF. As a conclusion, the variation in DF content and composition in this study was significantly influenced by both harvest year and rye genotype. © 2002 Society of Chemical Industry 相似文献
74.
Methane is an important climate gas contributing significantly to global warming. A large part of the anthropogenic emissions of methane comes from landfills. Due to the biogenic origin of these emissions and the inhomogeneous characteristics of landfills and their soil cover, these emissions show large spatial variation. Thus, development of reliable and cost-effective methods for measurements of these emissions is an important task and a challenge to the scientific community. Traditionally, field chamber methods have been used but also different area integrating methods based on downwind plume measurements. These measurements have been supported by meteorological data either directly from local measurements or by controlled release of tracer gas from the landfill providing the dispersion characteristics of the plume. In this paperwe describe a method,the Time Correlation Tracer method, combining controlled tracer gas release from the landfill with time-resolved concentration measurements downwind the landfill using FTIR absorption spectroscopy. The method has been tested and used on measurements at a landfill in southern Sweden over the past 1.5 years. The method has proven to be a usable method for measurements of total methane emission from landfills, and under favorable meteorological conditions we estimate an achievable accuracy of 15-30%. The real time analysis capability of the FTIR makes it possible to judge the success of the measurement already on site and to decide whether more measurements are necessary. The measurement strategy is relatively simple and straightforward, and one person can make a measurement from a medium sized landfill (1-4 ha) within a few days to a week depending on the meteorological situation. 相似文献
75.
Markström E Svensson ECh Shao R Svanberg B Billig H 《Reproduction (Cambridge, England)》2002,123(1):23-30
Only a minute fraction of the ovarian follicles present in a fetal ovary will complete the path to ovulation. Most of the follicles will undergo atresia, a hormonally controlled apoptotic process. Apoptosis occurs at each stage of follicular development and there is a marked reduction in the number of follicles present at birth. Stage-dependent mechanisms of follicle survival can be postulated to achieve co-ordinated development, leading to ovulation of a small fraction of follicles. Indeed, hormone and growth factor regulation of follicular atresia is stage-specific. This short review considers the factors that promote survival of ovarian follicles throughout development, including endocrine, locally produced and intracellular mediators, as exemplified mainly by follicular development in rodents. In primordial follicles, oocyte apoptosis is considered to be the cause of subsequent follicle degeneration. In slow-growing preantral follicles, FSH is not a survival factor, but some locally produced growth factors are. Progression to the antral follicle stage is probably the most critical stage of follicle development in vivo, and FSH is a major survival factor at this stage. In addition, insulin-like growth factor I and interleukin 1beta are potent survival factors for cultured rat follicles at the antral stage. Preovulatory follicles express receptors for LH, and both of the gonadotrophins are survival factors at this stage. Relatively little is known about the period between the LH surge and ovulation; however, it has been suggested that at this stage progesterone acts as a survival factor. 相似文献
76.
The effect of the reaction temperature and the metals of an iron subgroup on the thermo-chemical treatment of titanium carbide with a chlorine gas and their influence on the carbon structure obtained thereby was studied. Different analytical methods such as porosity measurements, X-ray diffraction spectrometry and a high-resolution electron microscopy revealed the catalytic behaviour of the above-mentioned metals, which appeared to support the formation of graphitised carbon at much lower temperatures compared to those needed for the ordinary thermo-chemical chlorination of titanium carbide. 相似文献
77.
Afaf Kamal-Eldin Lars Åke Appelqvist 《Journal of the American Oil Chemists' Society》1994,71(2):135-139
Seeds from different collections of cultivatedSesamum indicum Linn. and three related wild species [specifically,S. alatum Thonn.,S. radiatum Schum and Thonn. andS. angustifolium (Oliv.) Engl.] were studied for their oil content and fatty acid composition of the total lipids. The wild seeds contained
less oil (ca. 30%) than the cultivated seeds (ca. 50%). Lipids from all four species were comparable in their total fatty acid composition, with palmitic (8.2–12.7%), stearic
(5.6–9.1%), oleic (33.4–46.9%) and linoleic acid (33.2–48.4%) as the major acids. The total lipids from selected samples were
fractionated by thin-layer chromatography into five fractions: triacylglycerols (TAG; 80.3–88.9%), diacylglycerols (DAG; 6.5–10.4%),
free fatty acids (FFA; 1.2–5.1%), polar lipids (PL; 2.3–3.5%) and steryl esters (SE; 0.3–0.6%). Compared to the TAG, the four
other fractions (viz, DAG, FFA, PL and SE) were generally characterized by higher percentages of saturated acids, notably palmitic and stearic
acids, and lower percentages of linoleic and oleic acids in all species. Slightly higher percentages of long-chain fatty acids
(20∶0, 20∶1, 22∶0 and 24∶0) were observed for lipid classes other than TAG in all four species. Based on the fatty acid composition
of the total lipids and of the different acyl lipid classes, it seems thatS. radiatum andS. angustifolium are more related to each other than they are to the other two species. 相似文献
78.
The aim of the present study was to investigate the influence of partially hydrogenated vegetable and marine oils on membrane
composition and function of liver microsomes and platelets with particular reference to the metabolism of linoleic acid and
the production of arachidonic acid metabolites. Four groups of male weanling rats were fed linoleic acid supplemented diets
containing 20% (w/w) of partially hydrogenated low erucic acid rapeseed oil (HLRSO), partially hydrogenated herring oil (HHO),
olive oil (OO) and trierucin + triolein (TE) for 10 weeks. An additional two groups were fed partially hydrogenated low erucic
acid rapeseed oil and partially hydrogenated herring oil without linoleic acid supplementation (HLRSO- and HHO-, respectively).
Substantial amounts oftrans fatty acids were incorporated into liver microsomes (12.6% in group HLRSO) and platelets (7.0% in group HLRSO-). This incorporation
was not dependent on the dietary linoleic acid level. Hepatic microsomal Δ5-desaturase activity was significantly increased after HLRSO feeding compared to OO feeding. Δ6-Desaturase activity did not vary in the linoleic acid supplemented groups. Both Δ5- and Δ6-desaturase activities were significantly increased in groups without linoleic acid supplementation.
Docosenoic acid was incorporated into platelet phospholipids in contrast to liver microsomes. In the platelet, docosenoic
acid seemed to have a special preference for phosphatidylserine. Very small amounts were incorporated into platelet phosphatidylinositol.
Feeding diets HLRSO, HHO and OO did not influence rat platelet cyclooxygenase or 12-lipoxygenase activity. Platelets from
rats fed TE, however, produced significantly less 12-hydroxy-5,8,10,14-eicosatetraenoic acid (12-HETE) than platelets from
rats fed OO. Feeding of HLRSO- and HHO- resulted in a significantly diminished production of the arachidonic acid metabolites
12-HETE, 12-hydroxy-5,8,10-heptadecatrienoic acid (HHT) and 6-keto-prostaglandin F1α in stimulated platelets and aorta. Thus, high dietary levels oftrans isomers of monoenoic acids do not interfere with platelet cyclooxygenase or lipoxygenase activity provided sufficient amounts
of linoleic acid are available. 相似文献
79.
Effects of a titanate coupling agent on the mechanical and thermo‐physical properties of talc‐reinforced polyethylene compounds
下载免费PDF全文
![点击此处可从《应用聚合物科学杂志》网站下载免费的PDF全文](/ch/ext_images/free.gif)
An experimental study was carried out to investigate the effects of a titanate coupling agent on the mechanical properties, moisture absorption, and thermal conductivity of talc‐filled high‐density polyethylene (HDPE). Talc (0–35 wt %) was used as reinforcement particulate filler in an HDPE matrix and samples were prepared in a micro‐compounder and an injection molding machine. Isopropyl tri(dioctyl)phosphate titanate (0.5 wt %) was used as coupling agent. Composites with and without coupling agent were evaluated for changes in mechanical and thermo‐physical properties, morphology, and void content. Addition of the titanate coupling agent most often resulted in an increase in stiffness and tensile strength. Furthermore, both the void content and the elongation at break of composites were reduced. Results also showed that the coupling agent had no effects on the thermal conductivity, thermal diffusivity, and specific heat capacity of the composites. In addition, it was observed that the coupling agent was more effective at low concentrations of filler. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40449. 相似文献
80.
New developments at JET in diagnostics, real-time control, data acquisition and information retrieval with potential application to ITER 总被引:1,自引:0,他引:1
J. Vega A. Murari G. de Arcas M. Riva J. Svensson 《Fusion Engineering and Design》2009,84(12):2136-2144
In magnetic confinement fusion, the operation of next generation devices will be significantly different compared to present day machines. The duration length of the discharges will require abandoning the traditional paradigm of processing and storing the data after the shot. In fact most information will have to be made available in real-time. The significant issues of machine protection will require more sophisticated and at the same time more robust feedback control schemes. Another very important issue emerged in the last years of JET operation, and which is expected to become more severe in ITER, is the large amount of data to be analysed, which cannot be handled in the most efficient way with traditional methods.In order to prepare for the operation of ITER, some tests are being performed at JET. The capacity of the real-time network has increased in the last years, and many more systems, mainly diagnostics have been connected to it in order to test their reliability and to assess the quality of the information they can provide for feedback control. To reduce the amount of data, a prototype of real-time adaptive data acquisition techniques is being implemented, to adjust the acquisition frequency to the time resolution of the phenomena to be analysed in the plasma. Lossless data compression techniques have been refined and various intelligent signal processing methods have already been implemented to allow an easier and more objective first screening of the data. To allow scientists from wide and diffuse communities to participate in the scientific and technical programme, various innovative tools for remote participation and experimentation are also being actively investigated. 相似文献