全文获取类型
收费全文 | 1437篇 |
免费 | 78篇 |
专业分类
电工技术 | 1篇 |
化学工业 | 537篇 |
金属工艺 | 25篇 |
机械仪表 | 30篇 |
建筑科学 | 58篇 |
矿业工程 | 1篇 |
能源动力 | 34篇 |
轻工业 | 300篇 |
水利工程 | 8篇 |
石油天然气 | 6篇 |
无线电 | 58篇 |
一般工业技术 | 140篇 |
冶金工业 | 162篇 |
原子能技术 | 2篇 |
自动化技术 | 153篇 |
出版年
2023年 | 14篇 |
2022年 | 101篇 |
2021年 | 92篇 |
2020年 | 39篇 |
2019年 | 46篇 |
2018年 | 45篇 |
2017年 | 40篇 |
2016年 | 53篇 |
2015年 | 47篇 |
2014年 | 53篇 |
2013年 | 97篇 |
2012年 | 85篇 |
2011年 | 83篇 |
2010年 | 73篇 |
2009年 | 76篇 |
2008年 | 83篇 |
2007年 | 60篇 |
2006年 | 57篇 |
2005年 | 38篇 |
2004年 | 39篇 |
2003年 | 21篇 |
2002年 | 23篇 |
2001年 | 27篇 |
2000年 | 13篇 |
1999年 | 16篇 |
1998年 | 17篇 |
1997年 | 19篇 |
1996年 | 16篇 |
1995年 | 12篇 |
1994年 | 9篇 |
1993年 | 9篇 |
1991年 | 4篇 |
1990年 | 7篇 |
1989年 | 6篇 |
1988年 | 4篇 |
1987年 | 5篇 |
1986年 | 3篇 |
1985年 | 3篇 |
1984年 | 5篇 |
1983年 | 3篇 |
1980年 | 3篇 |
1979年 | 5篇 |
1977年 | 3篇 |
1974年 | 5篇 |
1972年 | 5篇 |
1931年 | 5篇 |
1930年 | 5篇 |
1929年 | 5篇 |
1926年 | 5篇 |
1925年 | 11篇 |
排序方式: 共有1515条查询结果,搜索用时 8 毫秒
121.
122.
António César Silva Ferreira Judith Monteiro Carla Oliveira Paula Guedes de Pinho 《Food chemistry》2008
The carotenoids degradation and the formation of volatiles were examined by simulating Port wine aging. A two year old red Port wine was saturated with oxygen, supplemented with lutein and β-carotene and kept at 60 °C during 87 h. A similar study was performed in a model wine solution. Results showed that the percentage decrease in lutein levels was, respectively, 79% and 95%, in the wine model solution and in the Port wine, and 55% and 10% for β-carotene, indicating that lutein was more sensitive to degradation than β-carotene. Two other unknown degradation carotenoid compounds were identified by HPLC/DAD (reverse phase λmax: 422; 445; 475 and 422; 445; 472) in the lutein supplemented wine. Levels of β-ionone and β-cyclocitral increased (2.5 times) in both, wine and wine model solution, supplemented with β-carotene. Along with these compounds, the same behaviour was observed in β-damascenone in the supplemented lutein wine and wine model solution. New insights were provided into the understanding of aroma modifications occurring during Port wine aging. The relationship between carotenoid molecules (β-carotene and lutein) and some volatiles has also been provided. 相似文献
123.
124.
125.
Kaiser Susan B.; Wingate Stacy B.; Freeman Carla M.; Chandler Joan L. 《Canadian Metallurgical Quarterly》1987,32(1):51
Investigated appearance management (AM) as a social–psychological variable in 322 physically disabled university students. The questionnaire included an AM and social interaction scale and measures of acceptance of disability. A tendency to regard AM as a form of compensation was associated with a tendency to view physical disability as a central or salient aspect of personal identity. Data suggest that AM is regarded by some as a means for ameliorating the social impact of a physical disability, but is expected to serve only a secondary role in impression formation. The relationship between disability acceptance and predisposition toward AM is discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
126.
127.
Rogério Mendes Carla Pestana Amparo Gonçalves 《International Journal of Food Science & Technology》2008,43(11):2000-2009
Sardine (Sardina pilchardus) is a species that for its abundance assumes great importance in the Portuguese fishing sector. In order to contribute for a better utilisation of this species, the aim of this study was to investigate the effect of the pre‐treatment with soluble gas stabilisation (SGS) (100% CO2 at 2 bar, during 15 and 30 min) on the quality and shelf‐life of sardine fillets, packed in air (AP), vacuum (VP) and modified atmosphere (MAP: 5% O2/35% CO2/60% N2). During the chilled storage, the quality changes were evaluated by sensory evaluation, chemical and microbiological analysis. The total volatile basic nitrogen content remained almost constant, between 16 and 19 mg N/100 g muscle, during the storage period, for all samples. The TBARs values increased with storage time, for all batches and storage conditions. The application of SGS treatment to sardine fillets, resulted in a bacteriostatic effect, contributing to the improvement of the microbiological quality of fillets. Considering a sensory criteria, the shelf‐life of SGS pre‐treated sardine fillets was found to be 5 days in AP and MAP while in VP‐treated fillets a shelf‐life of 8 days was reported. At sensory rejection, sardine fillets presented a K‐value of 30% in AP and MAP batches and 40% in VP batch. 相似文献
128.
Specimens representing six different bond compositions in soft, medium, and hard grades of artificial aluminous grinding wheels were tested for various physical properties such as hardness, elasticity, expansion, mechanical endurance, impact strength, etc. It was found that the expansion of present commercial grinding wheels and abrasive bonds is much less than that of artificial corundum. The strength of the wheels increases greatly with increasing percentages of bond. The methods of making the various physical determinations are given along with their interpretation. 相似文献
129.
Antonio Marigo Valerio Causin Carla Marega Paolo Ferrari 《Polymer International》2004,53(12):2001-2008
Wide‐angle X‐ray scattering and differential scanning calorimetry measurements have been conducted on seven random copolymers of propylene with ethylene in order to study the γ phase formation as a function of the comonomer content. The lamellar morphology of the samples was also investigated by small‐angle X‐ray scattering. The content of the γ phase was found to go through a maximum with crystallization temperature and to increase with comonomer concentration, up to a point (ethylene ≥6.5 wt%) where the latter parameter became less influential. The multiple melting endotherms behaviour of the samples was studied by DSC and temperature‐controlled diffractometric techniques. The attribution of the DSC peaks to the different isotactic polypropylene polymorphs that form in these conditions was confirmed. The results obtained permitted us to ascertain that, in the experimental conditions chosen, some further formation of crystallites takes place during the quenching to room temperature after the crystallization isotherm. In this phase, the chains organize themselves in stacks with thin lamellae, forming a distinct population with respect to those formed on isothermal crystallization. The melting of the thinner lamellae determines a convergence of the two populations into just one, still retaining an organization in stacks, that gradually disappears until complete melting of the material. Copyright © 2004 Society of Chemical Industry 相似文献
130.
The study investigated the effect of wearing chipper knives on machine productivity, fuel consumption and particles size distribution. The test included two different tree species (poplar and pine), two tree parts (branches and logs) and two screen types (large and medium). Chip quality was defined by CEN international technical standards. Knife wear causes a significant reduction of chipping productivity and a remarkable increase of fuel consumption. The replacement of the standard wide mesh screen with a narrower screen has a similar effect, further decreasing productivity and increasing fuel consumption. For the same screen type and knife wear level, productivity and fuel consumption are the same for poplar and pine. Knife, tree species and tree part also have a significant impact on chip size distribution. Chips produced from logs always contain a smaller proportion of oversize particles and a higher proportion of accepts. For the same large mesh screen, poplar chips tend to be larger than pine chips and to contain a higher proportion of oversize particles. On the contrary, pine chips tend to be smaller and to contain a higher proportion of fines. The use of a narrower mesh screen on pine material does not seem to offer any significant reduction of oversize particles, whose presence is already very limited. Therefore, a standard large mesh screen should be used when chipping pine material. 相似文献