全文获取类型
收费全文 | 1249篇 |
免费 | 92篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 12篇 |
综合类 | 1篇 |
化学工业 | 291篇 |
金属工艺 | 17篇 |
机械仪表 | 19篇 |
建筑科学 | 51篇 |
矿业工程 | 2篇 |
能源动力 | 48篇 |
轻工业 | 82篇 |
水利工程 | 24篇 |
石油天然气 | 1篇 |
无线电 | 91篇 |
一般工业技术 | 317篇 |
冶金工业 | 163篇 |
原子能技术 | 7篇 |
自动化技术 | 218篇 |
出版年
2024年 | 3篇 |
2023年 | 19篇 |
2022年 | 32篇 |
2021年 | 49篇 |
2020年 | 35篇 |
2019年 | 39篇 |
2018年 | 46篇 |
2017年 | 45篇 |
2016年 | 50篇 |
2015年 | 35篇 |
2014年 | 52篇 |
2013年 | 86篇 |
2012年 | 118篇 |
2011年 | 130篇 |
2010年 | 81篇 |
2009年 | 85篇 |
2008年 | 78篇 |
2007年 | 82篇 |
2006年 | 54篇 |
2005年 | 45篇 |
2004年 | 36篇 |
2003年 | 30篇 |
2002年 | 21篇 |
2001年 | 11篇 |
2000年 | 8篇 |
1999年 | 11篇 |
1998年 | 7篇 |
1997年 | 7篇 |
1996年 | 4篇 |
1995年 | 8篇 |
1994年 | 4篇 |
1993年 | 5篇 |
1992年 | 3篇 |
1991年 | 1篇 |
1990年 | 2篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1978年 | 2篇 |
1975年 | 1篇 |
1973年 | 1篇 |
1963年 | 1篇 |
1946年 | 1篇 |
1930年 | 1篇 |
1923年 | 5篇 |
1922年 | 2篇 |
1921年 | 2篇 |
排序方式: 共有1344条查询结果,搜索用时 31 毫秒
51.
Giuseppe Grosso Stefano Marventano Justin Yang Agnieszka Micek Andrzej Pajak Luca Scalfi 《Critical reviews in food science and nutrition》2017,57(15):3218-3232
Many studies have reported that higher adherence to Mediterranean diet may decrease cardiovascular disease (CVD) incidence and mortality. We performed a meta-analysis to explore the association in prospective studies and randomized control trials (RCTs) between Mediterranean diet adherence and CVD incidence and mortality. The PubMed database was searched up to June 2014. A total of 17 studies were extracted and 11 qualified for the quantitative analysis. Individuals in the highest quantile of adherence to the diet had lower incidence [relative risk (RR): 0.76, 95% confidence intervals (CI): 0.68, 0.83] and mortality (RR: 0.76, 95% CI: 0.68, 0.83) from CVD compared to those least adherent. A significant reduction of risk was found also for coronary heart disease (CHD) (RR: 0.72, 95% CI: 0.60, 0.86), myocardial infarction (MI) (RR: 0.67; 95% CI: 0.54, 0.83), and stroke (RR: 0.76; 95% CI: 0.60, 0.96) incidence. Pooled analyses of individual components of the diet revealed that the protective effects of the diet appear to be most attributable to olive oil, fruits, vegetables, and legumes. An average reduced risk of 40% for the aforementioned outcomes has been retrieved when pooling results of RCTs. A Mediterranean dietary pattern is associated with lower risks of CVD incidence and mortality, including CHD and MI. The relative effects of specific food groups should be further investigated. 相似文献
52.
Jayven Chee Chuan Yeo Joseph Kinyanjui Muiruri Justin Junqiang Koh Warintorn Thitsartarn Xikui Zhang Junhua Kong Ting Ting Lin Zibiao Li Chaobin He 《Advanced functional materials》2020,30(30)
The future of green electronics possessing great strength and toughness proves to be a promising area of research in this technologically advanced society. This work develops the first fully bendable and malleable toughened polylactic acid (PLA) green composite by incorporating a multifunctional polyhydroxybutyrate rubber copolymer filler that acts as an effective nucleating agent to accelerate PLA crystallization and performs as a dynamic plasticizer to generate massive polymer chain movement. The resultant biocomposite exhibits a 24‐fold and 15‐fold increment in both elongation and toughness, respectively, while retaining its elastic modulus at >3 GPa. Mechanism studies show the toughening effect is due to an amalgamation of massive shear yielding, crazing, and nanocavitation in the highly dense PLA matrix. Uniquely distinguished from the typical flexible polymer that stretches and recovers, this biocomposite is the first report of PLA that can be “bend, twist, turn, and fold” at room temperature and exhibit excellent mechanical robustness even after a 180° bend, attributes to the highly interconnected polymer network of innumerable nanocavitation complemented with an extensively unified fibrillar bridge. This unique trait certainly opens up a new horizon to future sustainable green electronics development. 相似文献
53.
正一家在上海创办的建筑与室内设计事务所,致力于根据客户的需求制定美观新颖的空间解决方案。我们对概念的艺术性和施工的工艺同样重视。每个项目都根据其环境和条件量身定做,并在有限的造价和时间里做出最好的效果。来到这个剧院的观众,都是自己这出戏的演员和导演。间离剧以独特的形态,为观众提供了别具一格 相似文献
54.
Benjamin Alexander Tyrone L. Daulton Guy M. Genin Justin Lipner Jill D. Pasteris Brigitte Wopenka Stavros Thomopoulos 《Journal of the Royal Society Interface》2012,9(73):1774-1786
The nanometre-scale structure of collagen and bioapatite within bone establishes bone''s physical properties, including strength and toughness. However, the nanostructural organization within bone is not well known and is debated. Widely accepted models hypothesize that apatite mineral (‘bioapatite’) is present predominantly inside collagen fibrils: in ‘gap channels’ between abutting collagen molecules, and in ‘intermolecular spaces’ between adjacent collagen molecules. However, recent studies report evidence of substantial extrafibrillar bioapatite, challenging this hypothesis. We studied the nanostructure of bioapatite and collagen in mouse bones by scanning transmission electron microscopy (STEM) using electron energy loss spectroscopy and high-angle annular dark-field imaging. Additionally, we developed a steric model to estimate the packing density of bioapatite within gap channels. Our steric model and STEM results constrain the fraction of total bioapatite in bone that is distributed within fibrils at less than or equal to 0.42 inside gap channels and less than or equal to 0.28 inside intermolecular overlap regions. Therefore, a significant fraction of bone''s bioapatite (greater than or equal to 0.3) must be external to the fibrils. Furthermore, we observe extrafibrillar bioapatite between non-mineralized collagen fibrils, suggesting that initial bioapatite nucleation and growth are not confined to the gap channels as hypothesized in some models. These results have important implications for the mechanics of partially mineralized and developing tissues. 相似文献
55.
Tejminder S. Sidhu Shauna L. French Justin R. Hamilton 《International journal of molecular sciences》2014,15(4):6169-6183
Protease-activated receptors (PARs) are a family of four G protein-coupled receptors that exhibit increasingly appreciated differences in signaling and regulation both within and between the receptor class. By nature of their proteolytic self-activation mechanism, PARs have unique processes of receptor activation, “ligand” binding, and desensitization/resensitization. These distinctive aspects have presented both challenges and opportunities in the targeting of PARs for therapeutic benefit—the most notable example of which is inhibition of PAR1 on platelets for the prevention of arterial thrombosis. However, more recent studies have uncovered further distinguishing features of PAR-mediated signaling, revealing mechanisms by which identical proteases elicit distinct effects in the same cell, as well as how distinct proteases produce different cellular consequences via the same receptor. Here we review this differential signaling by PARs, highlight how important distinctions between PAR1 and PAR4 are impacting on the progress of a new class of anti-thrombotic drugs, and discuss how these more recent insights into PAR signaling may present further opportunities for manipulating PAR activation and signaling in the development of novel therapies. 相似文献
56.
Srikanth S. Pathapati Angelo L. Mazzei James R. Jackson Paul K. Overbeck Justin P. Bennett Cece M. Cobar 《臭氧:科学与工程》2016,38(4):245-252
Typical ozone mixing and mass transfer calculations are lumped approaches based on ideal operating conditions and can misrepresent behavior in real-life installations. This article models the effect of local hydrodynamics and mixing on the overall mass transfer of ozone into water with the aid of multiphase computational fluid dynamics (CFD). CFD models were validated with measured data from a pipeline ozone contactor installation which was optimized for more rapid, uniform mixing and mass transfer. Results emphasize the sensitivity of mixing quality to nozzle placement, size, orientation and spacing relative to main pipeline diameter and flows. 相似文献
57.
This study investigated the effects that a form fitted, moisture-wicking fabric shirt, promoted to have improved evaporative and ventilation properties, has on the physiological and perceptual responses during exercise in the heat. Ten healthy male participants completed two heat stress tests consisting of 45 min of exercise (50% VO2peak) in a hot environment (33 °C, 60% RH). One heat stress test was conducted with the participant wearing a 100% cotton short sleeved t-shirt and the other heat stress test was conducted with the participant wearing a short sleeved synthetic shirt (81% polyester and 19% elastane). Rectal temperature was significantly lower (P < 0.05) in the synthetic condition during the last 15 min of exercise. Furthermore, the synthetic polyester shirt retained less sweat (P < 0.05). As exercise duration increases, the ventilation and evaporation properties of the synthetic garment may prove beneficial in the preservation of body temperature during exercise in the heat. 相似文献
58.
59.
Kar Tean Tan Christopher C. White Donald Hunston Justin M. Gorham Michael J. Imburgia Aaron M. Forster Bryan D. Vogt 《Polymer Engineering and Science》2016,56(1):18-26
Joints held by polymeric adhesives are commonplace in many engineered products, but normal service can require exposure to environmental conditions that present a significant challenge for maintaining the structural integrity of the interface. In particular, aqueous environments can wreak havoc on the joint strength. Here, a mechanistic approach is used to understand the difference in the debonding behavior of an epoxy/aluminum (oxide) interface when exposed to deionized (DI) water and aqueous sodium chloride by correlating macroscopic failure with the sorption of salt and water into the adhesive and its nanoscale distribution. For the epoxy‐aluminum system examined here, the presence of sodium chloride increases the resistance to crack growth in comparison to DI water. The debonding appears to be controlled by water near the buried interface. Salt water decreases the solubility of water in the epoxy and decreases the concentration of water near the buried interface, but the concentration of salt that enters the epoxy is below the detection limit. Thus, even if ions cannot penetrate or sorb into the adhesive, the presence of salt can significantly alter the water distribution within the adhesive and ultimately the strength of the joint. POLYM. ENG. SCI., 56:18–26, 2016. © 2015 Society of Plastics Engineers 相似文献
60.
Deborah?S.?JacobsEmail author Sin-Ru?Huang Yu-Lun?Cheng Savelas?A.?Rabb Justin?M.?Gorham Peter?J.?Krommenhoek Lee?L.?Yu Tinh?Nguyen Lipiin?Sung 《Journal of Coatings Technology and Research》2016,13(5):735-751
Many coating properties such as mechanical, electrical, and ultraviolet (UV) resistance are greatly enhanced by the addition of nanoparticles, which can potentially increase the use of nanocoatings for many outdoor applications. However, because polymers used in all coatings are susceptible to degradation by weathering, nanoparticles in a coating may be brought to the surface and released into the environment during the life cycle of a nanocoating. Therefore, the goal of this study is to investigate the process and mechanism of surface degradation and potential particle release from a commercial nanosilica/polyurethane coating under accelerated UV exposure. Recent research at the National Institute of Standards and Technology (NIST) has shown that the matrix in an epoxy nanocomposite undergoes photodegradation during exposure to UV radiation, resulting in surface accumulation of nanoparticles and subsequent release from the composite. In this study, specimens of a commercial polyurethane (PU) coating, to which a 5 mass% surface-treated silica nanoparticle solution was added, were exposed to well-controlled, accelerated UV environments. The nanocoating surface morphological changes and surface accumulation of nanoparticles as a function of UV exposure were measured, along with chemical change and mass loss using a variety of techniques. Particles from the surface of the coating were collected using a simulated rain process developed at NIST, and the collected runoff specimens were measured using inductively coupled plasma optical emission spectroscopy to determine the amount of silicon released from the nanocoatings. The results demonstrated that the added silica nanoparticle solution decreased the photodegradation rate (i.e., stabilization) of the commercial PU nanocoating. Although the degradation was slower than the previous nanosilica epoxy model system, the degradation of the PU matrix resulted in accumulation of silica nanoparticles on the nanocoating surface and release to the environment by simulated rain. These experimental data are valuable for developing models to predict the long-term release of nanosilica from commercial PU nanocoatings used outdoors and, therefore, are essential for assessing the health and environmental risks during the service life of exterior PU nanocoatings. 相似文献