全文获取类型
收费全文 | 3344篇 |
免费 | 122篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 35篇 |
综合类 | 1篇 |
化学工业 | 609篇 |
金属工艺 | 55篇 |
机械仪表 | 62篇 |
建筑科学 | 180篇 |
矿业工程 | 23篇 |
能源动力 | 131篇 |
轻工业 | 383篇 |
水利工程 | 25篇 |
石油天然气 | 8篇 |
无线电 | 296篇 |
一般工业技术 | 502篇 |
冶金工业 | 737篇 |
原子能技术 | 23篇 |
自动化技术 | 401篇 |
出版年
2023年 | 15篇 |
2022年 | 30篇 |
2021年 | 59篇 |
2020年 | 32篇 |
2019年 | 43篇 |
2018年 | 57篇 |
2017年 | 52篇 |
2016年 | 71篇 |
2015年 | 72篇 |
2014年 | 99篇 |
2013年 | 172篇 |
2012年 | 133篇 |
2011年 | 156篇 |
2010年 | 118篇 |
2009年 | 115篇 |
2008年 | 163篇 |
2007年 | 146篇 |
2006年 | 113篇 |
2005年 | 112篇 |
2004年 | 87篇 |
2003年 | 84篇 |
2002年 | 75篇 |
2001年 | 76篇 |
2000年 | 61篇 |
1999年 | 72篇 |
1998年 | 232篇 |
1997年 | 150篇 |
1996年 | 103篇 |
1995年 | 70篇 |
1994年 | 54篇 |
1993年 | 67篇 |
1992年 | 42篇 |
1991年 | 36篇 |
1990年 | 33篇 |
1989年 | 33篇 |
1988年 | 26篇 |
1987年 | 23篇 |
1986年 | 28篇 |
1985年 | 25篇 |
1984年 | 22篇 |
1983年 | 27篇 |
1982年 | 15篇 |
1981年 | 13篇 |
1980年 | 22篇 |
1978年 | 19篇 |
1977年 | 22篇 |
1976年 | 57篇 |
1975年 | 13篇 |
1973年 | 17篇 |
1972年 | 13篇 |
排序方式: 共有3471条查询结果,搜索用时 31 毫秒
51.
52.
J. Sampugna R. G. Jensen R. M. Parry C. F. Krewson 《Journal of the American Oil Chemists' Society》1964,41(2):132-133
Vernolic acid (cis-12,13-epoxy-cis-9-oetadece-noic acid) occurs as the triglyceride in the seed ofVernonia anthelmintica. Incubation of the seed produces a 1,3-divernolin. To determine whether the structure of trivernolin is responsible for the apparent secondary ester position specificity of the natural enzyme, trivernolin and tri-olein, were incubated with pancreatic lipase and the free fatty acids and monoglycerides were determined after 5 and 15 min digestion periods. The preponderance of 2-monoglyceride produced by the action of pancreatic lipase was interpreted to indicate that the structure of trivernolin was not solely responsible for the secondary position specificity of theV. anthelmintica lipase toward trivernolin. 相似文献
53.
Robin A. Henderson Robert G. Jensen Carol J. Lammi-Keefe Ann M. Ferris Kenneth R. Dardick 《Lipids》1992,27(11):863-869
To examine the effect of fish oil supplementation on the fatty acid (FA) composition of human milk and maternal and infant
erythrocytes, five lactating women were supplemented with 6 g of fish oil daily for 21d. Usual maternal diets contained 1,147
mg of total n−3 FA, with 120 mg from very long-chain (>C18) n−3 FA. Supplementation increased dietary levels to 3,092 mg of total n−3 FA and 2,006 mg of very long-chain n−3 FA. Milk
samples were collected daily, prior to fish oil ingestion, and at 4-h intervals on days 1, 7, 14 and 21. Milk n−3 FA content
increased within 8 h and reached steady state levels within one week. The n−6 fatty acid content decreased. Erythrocyte eicosapentaenoic
acid content increased from 0.24% to 1.4% (P<0.01) in mothers and from 0.11% to 0.70% (P<0.05) in infants. Docosapentaenoic acid increased from 1.4% to 2.2% (P<0.05) in mothers and from 0.30% to 0.78% (P<0.01) in infants. There was no significant change in docosahexaenoic acid or n−6 fatty acid content. Maternal platelet aggregation
responses were variable. No differences in milk or plasma tocopherol levels were noted.
Based on a paper presented at the Symposium on Milk Lipids held at the AOCS Annual Meeting, Baltimore, MD, April 1990. 相似文献
54.
The adhesion and interfacial properties of polyurethane (PU) foams with thermoplastic (TP) materials were investigated using different techniques. The adhesion performance of PU foam with TP materials was evaluated using the peel test method, and the adhesion durability was checked after different climate treatments. X‐ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and contact angle measurements were used to study the surface and interface morphology of PU foam and TP material system. Three types of PU foam samples which differ in their composition and also five commercially available TP blends systems, based on poly(carbonate), poly(styrene‐co‐maleic anhydride), poly(acrylonitrile‐butadiene‐styrene), and silicone acrylate rubber have been used. The slow reacting foam shows the best adhesion properties with all the TP materials. The climate treatments strongly effected the PU foam adhesion durability with poly(carbonate) containing TP materials (70–80% loss in adhesion), but nearly no effect with poly(styrene‐co‐maleic anhydride). The samples with lowered adhesion could be separated by peeling without visible foam residues on the TP surface. AFM, XPS, and surface tension studies have shown that the surface properties of the TP material are still governed by the PU foam. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 479–488, 2007 相似文献
55.
Rogers Jeffrey M. Jensen Jenny Valderrama Joaquin T. Johnstone Stuart J. Wilson Peter H. 《Virtual Reality》2021,25(2):357-366
Virtual Reality - Stroke rehabilitation suffers from low levels of patient engagement, impeding recovery. Virtual rehabilitation (VR) approaches can improve patient outcomes; however, there is... 相似文献
56.
57.
Zhiqiang Du Yang Chen Martin Jensen Ning Wang Xianfeng Li Xingxiang Zhang 《应用聚合物科学杂志》2021,138(9):49908
Zinc oxide (ZnO) nanostructures have received widespread attention due to their unique structure and broad application possibilities, but high preparation costs and agglomeration limit their usage. In this article, low-cost and environmentally friendly cellulose and ZnCl2 are used to synthesize ZnO nanoparticles (ZnO NPs). Subsequently, multifunctional ZnO/polyacrylonitrile hybrid nanofiber mats (ZnO/PAN@NFMs) with mechanical stability suitable for large-scale application are prepared via solution blow-spinning. The synthesized ZnO/PAN@NFMs exhibit higher photodegradation of organic dyes than earlier reported semiconductors and good recycling performance with an organic dye degradation above 94%–98% after five cycles, which is ascribed to fixation of the ZnO NPs in the nanofibers. In addition, the inhibition rate for Escherichia coli and Staphylococcus aureus is above 99.9% and the bacteriostatic rate against E. coli remains as high as 99% after 10 cycles. From these properties, the synthesized composite ZnO/PAN@NFMs are promising for wastewater cleaning and antibacterial fabrics. 相似文献
58.
Erika Leitel Wolfgang Hübner Karsten P. Thiessen Ju. B. Makari
ev A. G. Akimov 《工业材料与腐蚀》1988,39(1):1-7
Investigation into the passivation mechanism of iron in phosphate electrolytes on surfaces exposed to erosive attack On iron electrodes in neutral phosphate electrolytes by continuous solid particle impingement a reaction layer is formed within the transition potential region under anodic polarization. XPS and AES investigations show that the reaction layer formed under impingement will be replaced by an oxide layer during the transition into the passive state under simultaneous decrease of the layer thickness. The active/passive transition in phosphate electrolytes may be attached to the equilibrium potential of the reaction . According to this thermodynamic interpretation of both the active/passive transition and the passive/active transition, respectively on iron in presence of phosphate ions may be described as the Fe(II)/Fe(III)-redox reaction with two solid phases, the iron(II)-phosphate phase and the iron(III)-oxide phase. The increase of the interfacial dynamic processes at the solid/liquid interface causes in consequence of the solid particle impingement that thermodynamic laws govern the course of reactions. 相似文献
59.
By the use of an experimental setup for microfluidic flows, we have characterized the separation and concentration characteristics of the so-called Trilobite? separation unit. Our separation unit consists of microfluidic channels and an elliptical separation geometry with a solid and a permeable wall region. We show that it is possible to adjust the thickness of different flow layers by changing the flow rates and pressure drop over the permeable wall. For high pressure drops, the separator shows promising concentration characteristics. For low pressure drops, an increase in flow rate results in a thinning of the flow layers. For sufficiently high flow rates, it should therefore be possible to create flow layers sufficiently thin that the particle separation is entirely dominated by hydrodynamic forces. This, in turn, will enable clog-free particle separation. 相似文献
60.
Rasmus E. Christiansen Boyan S. Lazarov Jakob S. Jensen Ole Sigmund 《Structural and Multidisciplinary Optimization》2015,52(4):737-754
Resonance and wave-propagation problems are known to be highly sensitive towards parameter variations. This paper discusses topology optimization formulations for creating designs that perform robustly under spatial variations for acoustic cavity problems. For several structural problems, robust topology optimization methods have already proven their worth. However, it is shown that direct application of such methods is not suitable for the acoustic problem under consideration. A new double filter approach is suggested which makes robust optimization for spatial variations possible. Its effect and limitations are discussed. In addition, a known explicit penalization approach is considered for comparison. For near-uniform spatial variations it is shown that highly robust designs can be obtained using the double filter approach. It is finally demonstrated that taking non-uniform variations into account further improves the robustness of the designs. 相似文献