全文获取类型
收费全文 | 4917篇 |
免费 | 199篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 61篇 |
综合类 | 2篇 |
化学工业 | 1413篇 |
金属工艺 | 133篇 |
机械仪表 | 81篇 |
建筑科学 | 218篇 |
矿业工程 | 35篇 |
能源动力 | 82篇 |
轻工业 | 578篇 |
水利工程 | 34篇 |
石油天然气 | 13篇 |
无线电 | 329篇 |
一般工业技术 | 652篇 |
冶金工业 | 1041篇 |
原子能技术 | 40篇 |
自动化技术 | 407篇 |
出版年
2023年 | 48篇 |
2022年 | 178篇 |
2021年 | 281篇 |
2020年 | 111篇 |
2019年 | 97篇 |
2018年 | 104篇 |
2017年 | 100篇 |
2016年 | 143篇 |
2015年 | 105篇 |
2014年 | 138篇 |
2013年 | 155篇 |
2012年 | 173篇 |
2011年 | 195篇 |
2010年 | 148篇 |
2009年 | 158篇 |
2008年 | 152篇 |
2007年 | 141篇 |
2006年 | 126篇 |
2005年 | 142篇 |
2004年 | 94篇 |
2003年 | 90篇 |
2002年 | 92篇 |
2001年 | 94篇 |
2000年 | 86篇 |
1999年 | 85篇 |
1998年 | 306篇 |
1997年 | 180篇 |
1996年 | 130篇 |
1995年 | 116篇 |
1994年 | 87篇 |
1993年 | 92篇 |
1992年 | 59篇 |
1991年 | 55篇 |
1990年 | 54篇 |
1989年 | 50篇 |
1988年 | 37篇 |
1987年 | 35篇 |
1986年 | 35篇 |
1985年 | 43篇 |
1984年 | 33篇 |
1983年 | 31篇 |
1982年 | 39篇 |
1981年 | 37篇 |
1980年 | 31篇 |
1979年 | 50篇 |
1978年 | 21篇 |
1977年 | 48篇 |
1976年 | 91篇 |
1975年 | 23篇 |
1972年 | 18篇 |
排序方式: 共有5119条查询结果,搜索用时 15 毫秒
101.
Rita Głowacka Agata Górska Magdalena Wirkowska-Wojdyła Rafał Wołosiak Ewa Majewska Dorota Derewiaka 《International Journal of Food Science & Technology》2019,54(11):3008-3014
The content of bioactive compounds in spent coffee grounds (SGC) was studied. SGC were obtained from Coffea arabica beans of different roasting degrees (light and dark) and different geographical origins (Nicaragua, Columbia and Mexico) processed using four brewing methods (mocha, filtered, drip and infusion). The highest caffeine and chlorogenic acid contents were determined in filtered spent coffee extracts. All extracts of light roasted spent coffee grounds showed lower browning index levels in comparison to that from dark roasted spent coffee grounds. Generally, the highest content of total polyphenolic compounds and highest antioxidant capacity were determined in extracts prepared in drip. In conclusion, the results obtained in this study indicate that the spent coffee grounds produced of domestic levels, especially those obtained from filter coffeemaker, could be considered as a good source of natural antioxidants. 相似文献
102.
Fl��via Santos Twardowski Pinto Simone Hickmann Fl?res Carolina Elisa Schneider Marco Antonio Z��chia Ayub Plinho Francisco Hertz 《Food and Bioprocess Technology》2011,4(4):559-565
In this work, the influence of oxygen mass transfer rates on the production of cyclodextrin glycosyltransferase (CGTase) by the alkaliphilic bacterium Bacillus circulans ATCC 21783 was investigated. Experimental design and response surface methodology were applied to optimize agitation speed and air flow rate in batch cultivations, in order to identify their significant effects and interactions with the synthesis of CGTase. Results were expressed as the volumetric mass transfer rates of oxygen (kla, [per hour]). The maximal CGTase productivity of 155 U mL−1 h−1 was achieved with kla of 48 h−1. CGTase production was also studied in fed-batch cultures using the optimized parameters obtained in the batch experiments. The maximal CGTase productivity on fed-batch cultivations was 137 U mL−1 h−1 with feeding rates of starch at 0.17 g L−1 h−1. 相似文献
103.
The objective of this research was to study whether survival analysis results in a more accurate genetic evaluation for female fertility traits compared with the usual methodology based on linear models. The fertility trait studied was interval between calving and last insemination. A stochastic simulation describing the reproductive cycle of first-parity cows was done, in which true breeding values for conception rate were created. A model containing effects of sire and herd was used both with survival analysis and with mixed linear model analysis to predict sire breeding values. Correlations between true breeding values for conception rate and breeding values for calving to last insemination predicted by the best survival analysis model or the best linear model were 0.77 and 0.68, respectively. The results showed that when pregnancy status is known, survival analysis is a better method than linear models for genetic evaluation of conception rate when using observations on the interval between calving and last insemination. 相似文献
104.
BACKGROUND: In this study the interspecies differences in two‐dimensional electrophoresis patterns of skeletal muscle myosin light chain (MLC) isoforms between Bos taurus (cattle), Sus scrofa (pig), Gallus gallus (chicken), Meleagris gallopavo (turkey), Anas platyrhynchos (duck) and Anser anser (goose) were characterised on the basis of specific properties of MLCs associated with their structure and mobility in gel. RESULTS: Two‐dimensional electrophoresis separations revealed species‐specific differences in the molecular weight and pI of individual MLC isoforms (MLC1f, MLC2f and MLC3f). In the case of closely related animal species such as goose and duck or turkey and chicken, significant differences occurred in MLC1f. For MLC2f, differences between cattle and turkey and between pig and chicken were around 1 and 0.3 kDa respectively. It appeared from the comparison of amino acid sequences that even MLCs with only 2% difference in sequences have different electrophoretic mobilities. CONCLUSION: Interspecies differences in skeletal MLC isoforms appeared between cattle, pig, chicken, turkey, duck and goose. The slight changes observed in the course of the aging process confirmed that these proteins are relatively little susceptible to proteolytic enzymes during meat aging. Copyright © 2011 Society of Chemical Industry 相似文献
105.
106.
Heinrich U Koop U Leneveu-Duchemin MC Osterrieder K Bielfeldt S Chkarnat C Degwert J Häntschel D Jaspers S Nissen HP Rohr M Schneider G Tronnier H 《International journal of cosmetic science》2003,25(1-2):45-53
A multicentre study for measuring skin hydration with 349 volunteers was carried out in six different laboratories. The purpose of the study was to investigate physical-, physiological- and product-dependent parameters of three test emulsions (base, base + moisturizer and base + moisturizer + lipids) in a double-blind study. A comparison between analogous and digital sensor technology of the Corneometer CM825 was examined. Here, a clear relationship between both sensor types could be highlighted. A vital point of the study was the division of the test subjects according to their skin type. To get more objective limits for three different skin types - very dry, dry and normal skin - visual expert evaluation, self-assessment and hydration measurements were analysed by means of statistical methods. The moisture-related skin types were determined as follows: very dry skin was characterized with corneometer units below 30, dry skin between 30 and 40 and normal skin higher than 40 a.u. (arbitrary units). The efficacy of the three test emulsions was examined in relation to the mentioned skin types. Analysing the measured data of all test centres, a clear dependency of skin physiology (skin type) and product efficacy became evident. The drier the skin, the higher the increase of hydration. The product performance of the three test emulsions compared to the untreated control resulted in a significant increase of skin hydration in all measuring centres. The evaluation of a product ranking showed a good differentiation between the basic emulsion and the two other products. An increase of efficacy by adding lipids could be observed in four of six centres. The important influence of the skin type of the volunteers on the degree of product performance, as demonstrated in this study, should be especially considered when drawing up guidelines for efficacy testing. 相似文献
107.
This work presents a new adsorption technique where the adsorbent (powdered activated carbon-PAC) is in the form of suspended flocs formed with water-soluble polymer flocculants. Thus, the adsorption of a typical dye, methylene blue (MB), was studied onto polyacrylamide flocs of PAC (PACF) in a fluidized bed reactor. The technique is based on the fact that the adsorption capacity of PAC does not decrease after flocculation because the adsorbed polymer occupies only a few surface sites, in the form of trains, loops, and tails. Moreover, the adsorption was found to proceed through a rapid mass transfer of MB to the adsorbing PAC flocs, in the same extent as onto PAC. Because of the rapid settling characteristics of the aggregates formed, the two phase separations, loaded PAC and solution, become easier. Thus, the technique offers the advantages of conducting simultaneously both adsorption and solid/liquid separation all in one single stage. Results obtained showed that high MB removal values can be attained in a fluidized bed reactor (>90%) and that PACF presents a much higher adsorption capacity (breakthrough points) than granulated activated carbon (GAC) in the same adsorbing bed. It is believed that this technique highly broadens the potential of the use of powdered activated carbon or other similar ultrafine adsorbents. 相似文献
108.
Ferracin LM Fier CB Vieira ML Monteiro-Vitorello CB Varani Ade M Rossi MM Müller-Santos M Taniwaki MH Thie Iamanaka B Fungaro MH 《International journal of food microbiology》2012,155(3):137-145
In silico comparison of 34 putative pks genes in Aspergillus niger strain CBS 513.88 versus A. niger strain ATCC 1015 genome revealed significant nucleotide identity (>95% covering a minimum of 99% of the gene sequence) for 31 of these genes (approximately 91%). A. niger CBS 513.88 harbors three putative pks genes (An01g01130, An11g05940, and An15g07920), for which nucleotide identity was not found in A. niger ATCC 1015. To compare the results of the in silico analysis with the in vivo situation, experimental data were obtained for a large number of A. niger strains obtained from different substrates and geographical regions. Three putative pks genes that were found to be variable between the two A. niger strains using bioinformatics tools were in fact strain-specific genes based on experimental data. The PCR amplification signals for the An01g01130, An11g05940, and An15g07920 pks genes were detected in only 97%, 71%, and 26% of the strains, respectively. Southern blot analyses confirmed the PCR data. Because one of the strain-specific pks genes (An15g07920) is located in a putative ochratoxin cluster, we focused our investigation on that region. We assessed the ochratoxin production capability of the 119 A. niger strains and found a positive association between the presence of this pks gene and the capability of the respective strain to produce ochratoxin. 相似文献
109.
The effect of free and liposomal forms of phenolic lipids isolated from rye grains, cashew nut-shell liquid (CNSL) from Anacardium occidentale, and Merrulius tremellosus fruit body on the glycosyl-phosphatidylinositol (GPI)-anchor-deprived erythrocyte-ghost acetylcholinesterase activity was studied. It was shown that the observed effect distinctly depends on the form of the phenolic lipids available for interaction with the enzyme. The free form of the phenolic lipids decreased the enzymatic activity of GPI-anchor-deprived acetylcholinesterase less than the acetylcholinesterase anchored in erythrocytes ghosts, whereas the same phenolic lipids present in the medium in liposomal form, increased it. 相似文献
110.