全文获取类型
收费全文 | 349篇 |
免费 | 12篇 |
专业分类
电工技术 | 15篇 |
化学工业 | 45篇 |
金属工艺 | 4篇 |
机械仪表 | 10篇 |
建筑科学 | 17篇 |
能源动力 | 13篇 |
轻工业 | 28篇 |
水利工程 | 1篇 |
无线电 | 21篇 |
一般工业技术 | 91篇 |
冶金工业 | 87篇 |
原子能技术 | 2篇 |
自动化技术 | 27篇 |
出版年
2023年 | 3篇 |
2022年 | 6篇 |
2021年 | 14篇 |
2020年 | 6篇 |
2019年 | 3篇 |
2018年 | 4篇 |
2017年 | 7篇 |
2016年 | 14篇 |
2015年 | 5篇 |
2014年 | 11篇 |
2013年 | 10篇 |
2012年 | 11篇 |
2011年 | 15篇 |
2010年 | 9篇 |
2009年 | 7篇 |
2008年 | 9篇 |
2007年 | 8篇 |
2006年 | 9篇 |
2005年 | 8篇 |
2004年 | 10篇 |
2003年 | 4篇 |
2002年 | 3篇 |
2001年 | 5篇 |
2000年 | 7篇 |
1999年 | 3篇 |
1998年 | 37篇 |
1997年 | 7篇 |
1996年 | 15篇 |
1995年 | 14篇 |
1994年 | 15篇 |
1993年 | 9篇 |
1992年 | 2篇 |
1991年 | 6篇 |
1990年 | 5篇 |
1989年 | 4篇 |
1987年 | 3篇 |
1986年 | 4篇 |
1985年 | 8篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1982年 | 2篇 |
1981年 | 4篇 |
1977年 | 6篇 |
1976年 | 5篇 |
1973年 | 4篇 |
1940年 | 2篇 |
1938年 | 1篇 |
1937年 | 1篇 |
1935年 | 3篇 |
1934年 | 1篇 |
排序方式: 共有361条查询结果,搜索用时 156 毫秒
91.
Heat exchangers should work for many years satisfying and by low lifecycle costs. Equipping the tubes with brushes for cleaning inside can help to reduce corrosion and costs. But an additional risk of corrosion arises by running a heat exchanger at low velocity of water, causing brushes being blocked. The minimum velocity of water required depends on thickness, number and oversize length of the bristles, temperature of water, inside diameter, surface and on the total length of the tubes. For example in tubes of 4 m length, ID 16 mm, 480 bristles D 0.15 mm at 16°C, the water velocity should be minimum 0.8 m/s. Shorter tubes, thicker bristles, more bristles, lower temperature or lower water velocity are a higher risk. 相似文献
92.
White Bass (<Emphasis Type="Italic">Morone chrysops</Emphasis>) Preferentially Retain n-3 PUFA in Ova When Fed Prepared Diets with Varying FA Content
下载免费PDF全文
![点击此处可从《Lipids》网站下载免费的PDF全文](/ch/ext_images/free.gif)
S.?Adam?FullerEmail author Steven?D.?Rawles Matthew?E.?McEntire Troy?J.?Bader Marty?Riche Benjamin?H.?Beck Carl?D.?Webster 《Lipids》2017,52(10):823-836
We evaluated the fatty acid (FA) composition of broodstock white bass ova fed one of six commercial diets with increasing polyunsaturated FA content (n‐6/n‐3 ratio; 0.36, 0.39, 0.46, 0.83, 1.07, 1.12) eight weeks prior to sampling. Fatty acid profiles of ova from brooders fed each of the six diets were significantly altered according to canonical discriminant analysis. Ova FA profiles resulting from the 0.39 diet separated those from the 0.36 diet based on lower 18:2n‐6 (LNA) and higher 20:1n‐9 concentrations from the 0.36 diet. Ova profiles were further separated based on lower concentrations of 22:5n‐3 (DPA) from the 0.46 diet, lower concentrations of 20:5n‐3 (EPA) in the 1.12 and 0.83 diets, and lower concentrations of 22:6n‐3 (DHA) in all other diets relative to the 0.46 diet. Changes in ova FA profile at four and eight weeks were consistent with dietary intake with an approximate 2% increase in any given FA class with increasing time on individual diet. There was no correlation between dietary ARA concentrations (0.7–1.1 mol%), or dietary EPA/ARA ratios (7–15), and the concentrations (1.4–1.7 mol%) or ratios (3.3–4.4) found in the ova by diet. Our results suggest that white bass females have the ability to preferentially incorporate n‐3 PUFA, particularly DHA, suggesting mobilization of this FA from other tissues for ova deposition or preferential dietary incorporation of PUFA into ova. These results will add to the limited FA information available in white bass and enable nutritionists to formulate broodstock diets that maximize reproductive potential in this species. 相似文献
93.
Rate constants of reactions of ozone with non-ionized solutes, such as aliphatic alcohols, olefins, chlorosubstituted ethylenes, substituted benzenes and carbohydrates, have been determined from the absolute rates with which ozone reacts in the presence of various concentrations of these compounds in water. They have been tested by comparison with the relative rates by which pairs of these solutes are transformed by ozone. Different experimental methods have been developed to determine such rate constants in the range from 10?2 to 105 M?1 s?1. Interferences between the direct reactions of ozone and reactions due to its preliminary decomposition to secondary oxidants could be eliminated. The kinetics of all the reactions studied are first order with respect to ozone and solute concentration. The rate constants of many types of organic compounds in water are of the same order of magnitude as in organic solvents. Substituted benzenes, however, react in water about 100 times faster. They obey a linear free energy relationship with p = ?3.1 when based on δp+ values. Comparisons of rate constants with chemical structures of the reacting groups show that all reactions of ozone are highly selective and electrophilic. The kinetic data allow explanation of the chemical effects of ozone observed in water treatment practice. 相似文献
94.
Julia Fekadu Ute Modlich Peter Bader Shahrzad Bakhtiar 《International journal of molecular sciences》2022,23(7)
LFA-1 (Lymphocyte function-associated antigen-1) is a heterodimeric integrin (CD11a/CD18) present on the surface of all leukocytes; it is essential for leukocyte recruitment to the site of tissue inflammation, but also for other immunological processes such as T cell activation and formation of the immunological synapse. Absent or dysfunctional expression of LFA-1, caused by mutations in the ITGB2 (integrin subunit beta 2) gene, results in a rare immunodeficiency syndrome known as Leukocyte adhesion deficiency type I (LAD I). Patients suffering from severe LAD I present with recurrent infections of the skin and mucosa, as well as inflammatory symptoms complicating the clinical course of the disease before and after allogeneic hematopoietic stem cell transplantation (alloHSCT); alloHSCT is currently the only established curative treatment option. With this review, we aim to provide an overview of the intrinsic role of inflammation in LAD I. 相似文献
95.
The method of material flux analysis is applied as an instrument for the early recognition of environmental problems in an urban region of developing countries. It is shown that, even with poor data quality and quantity, it is possible to apply the method in Tunja, an urban region in Colombia. With sensitivity analysis monitoring points are developed to attain 'early recognition' concerning changes in water quality and quantity in this region. Using the scenario technique it is shown that, owing to the low dilution capacity for sewage in the region, surface water cannot reach the quality of water at a natural state even if technical measures used in industrialized countries are taken. 相似文献
96.
97.
Dumitru V. Schweizer H. Grabeldinger H. Harle R. Bader S. Brurderl G. Weimar A. Lell A. Harle V. 《Electronics letters》2003,39(4):372-373
Device fabrication and measurement results of an electrically injected distributed Bragg reflector InGaN/GaN laser operated at room temperature are presented. Using second-order gratings, the emission at 407.6 nm was achieved in the vertical direction, the device acting like a surface emitting laser. A voltage drop at threshold of 11.2 V and temperature stable emission with a wavelength shift of 0.0119 nm/K was obtained for the device. 相似文献
98.
W. Bader 《Electrical Engineering (Archiv fur Elektrotechnik)》1935,29(4):259-271
Ohne Zusammenfassung 相似文献
99.
T Walther D Balschun JP Voigt H Fink W Zuschratter C Birchmeier D Ganten M Bader 《Canadian Metallurgical Quarterly》1998,273(19):11867-11873
The Mas protooncogene is a maternally imprinted gene encoding an orphan G protein-coupled receptor expressed mainly in forebrain and testis. Here, we provide evidence for a function of Mas in the central nervous system. Targeted disruption of the Mas protooncogene leads to an increased durability of long term potentiation in the dentate gyrus, without affecting hippocampal morphology, basal synaptic transmission, and presynaptic function. In addition, Mas-/- mice show alterations in the onset of depotentiation. The permissive influence of Mas ablation on hippocampal synaptic plasticity is paralleled by behavioral changes. While spatial learning in the Morris water maze is not significantly influenced, Mas-deficient animals display an increased anxiety as assessed in the elevated-plus maze. Thus, Mas is an important modulating factor in the electrophysiology of the hippocampus and is involved in behavioral pathways in the adult brain. 相似文献
100.
Dynamic mechanical compression influences nitric oxide production by articular chondrocytes seeded in agarose 总被引:1,自引:0,他引:1
Nitric oxide (NO) has been implicated in the inhibition of cell proliferation in cytokine and lipopolysaccharide (LPS)-stimulated chondrocytes and is known to be influenced by physical forces in several tissues. In this study, a well-characterized model system utilizing bovine chondrocytes embedded in 3% agarose constructs has been used to investigate the effect of dynamic strain at 0.3, 1, or 3 Hz on NO production. LPS induced a significant increase in nitrite levels, which was reversed by both L-NAME and dexamethasone. Dynamic compressive strain produced a significant reduction in nitrite production. The effect was partially blocked by L-NAME but unaffected by dexamethasone. L-NAME also reversed dynamic compression-induced stimulation of [3H]-thymidine incorporation. NO appears to be a constituent of mechanotransduction pathways which influence proliferation of bovine chondrocytes seeded within agarose constructs. The inhibitor experiments also infer that alterations in cNOS activity primarily determine the response. 相似文献