全文获取类型
收费全文 | 2658篇 |
免费 | 127篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 22篇 |
化学工业 | 653篇 |
金属工艺 | 36篇 |
机械仪表 | 47篇 |
建筑科学 | 157篇 |
矿业工程 | 4篇 |
能源动力 | 37篇 |
轻工业 | 263篇 |
水利工程 | 34篇 |
石油天然气 | 13篇 |
无线电 | 159篇 |
一般工业技术 | 396篇 |
冶金工业 | 629篇 |
原子能技术 | 7篇 |
自动化技术 | 330篇 |
出版年
2023年 | 27篇 |
2022年 | 49篇 |
2021年 | 82篇 |
2020年 | 40篇 |
2019年 | 68篇 |
2018年 | 53篇 |
2017年 | 66篇 |
2016年 | 86篇 |
2015年 | 58篇 |
2014年 | 84篇 |
2013年 | 152篇 |
2012年 | 108篇 |
2011年 | 170篇 |
2010年 | 138篇 |
2009年 | 136篇 |
2008年 | 174篇 |
2007年 | 113篇 |
2006年 | 118篇 |
2005年 | 102篇 |
2004年 | 82篇 |
2003年 | 72篇 |
2002年 | 72篇 |
2001年 | 58篇 |
2000年 | 47篇 |
1999年 | 33篇 |
1998年 | 58篇 |
1997年 | 49篇 |
1996年 | 42篇 |
1995年 | 30篇 |
1994年 | 38篇 |
1993年 | 38篇 |
1992年 | 17篇 |
1991年 | 18篇 |
1990年 | 20篇 |
1989年 | 20篇 |
1988年 | 16篇 |
1987年 | 13篇 |
1986年 | 19篇 |
1985年 | 13篇 |
1984年 | 20篇 |
1983年 | 19篇 |
1982年 | 11篇 |
1981年 | 16篇 |
1980年 | 19篇 |
1979年 | 11篇 |
1978年 | 13篇 |
1977年 | 13篇 |
1976年 | 16篇 |
1975年 | 18篇 |
1974年 | 11篇 |
排序方式: 共有2787条查询结果,搜索用时 15 毫秒
71.
Sisi Zhang Rachel W.S. Chan Ernest H.Y. Ng William S.B. Yeung 《International journal of molecular sciences》2022,23(9)
Human endometrium is an incredibly dynamic tissue undergoing cyclic regeneration and shedding during a woman’s reproductive life. Endometrial mesenchymal stromal/stem-like cells (eMSC) contribute to this process. A hypoxic niche with low oxygen levels has been reported in multiple somatic stem cell types. However, the knowledge of hypoxia on eMSC remains limited. In mice, stromal stem/progenitor cells can be identified by the label-retaining technique. We examined the relationship between the label-retaining stromal cells (LRSC) and hypoxia during tissue breakdown in a mouse model of simulated menses. Our results demonstrated that LRSC resided in a hypoxic microenvironment during endometrial breakdown and early repair. Immunofluorescence staining revealed that the hypoxic-located LRSC underwent proliferation and was highly colocalized with Notch1. In vitro studies illustrated that hypoxia activated Notch signaling in eMSC, leading to enhanced self-renewal, clonogenicity and proliferation of cells. More importantly, HIF-1α played an essential role in the hypoxia-mediated maintenance of eMSC through the activation of Notch signaling. In conclusion, our findings show that some endometrial stem/progenitor cells reside in a hypoxic niche during menstruation, and hypoxia can regulate the self-renewal activity of eMSC via Notch signaling. 相似文献
72.
Daniel M. Marincel Huairuo Zhang Stephen Jesse Alex Belianinov Mahmut B. Okatan Sergei V. Kalinin W. Mark Rainforth Ian M. Reaney Clive A. Randall Susan Trolier‐McKinstry 《Journal of the American Ceramic Society》2015,98(6):1848-1857
Domain wall movement at and near engineered 10°, 15°, and 24° tilt and 10° and 30° twist grain boundaries was measured by band excitation piezoresponse force microscopy for Pb(Zr,Ti)O3 films with Zr/Ti ratio of 45/55 and 52/48. A minimum in nonlinear response was observed at the grain boundary for the highest angle twist and tilt grain boundaries, while a maximum in nonlinear response was observed at the 10° tilt grain boundaries. The observed nonlinear response was correlated with the domain configurations imaged in cross section by transmission electron microscopy. 相似文献
73.
Rebecca Lace Celia Murray-Dunning Rachel Williams 《Journal of Materials Science》2015,50(4):1523-1534
Synthetic materials have played a significant role in ophthalmic applications to improve vision for many years. This has been in four main areas in ophthalmology: ocular surface reconstruction, lens replacement, vitreous replacement and structural support and cell transplantation in the retina. Corneal replacement therapies have been developed using both synthetic acrylic-based materials and more recently naturally derived materials such as amniotic membrane. Intraocular lenses as a replacement for the natural lens post cataract surgery has been used for many years. Newer developments include the opportunity to use gels so that the lenses can accommodate but these need improving in terms of the cross-linking chemistry. Silicone oils have been used as long-term tamponade agents as vitreous replacements but recent developments in their properties has enhanced the clinical outcomes and further research into their use as drug delivery vehicles will be a major advancement. Regenerative medicine therapies to repopulate the retina to repair and replace specific cell layers require the optimisation of synthetic scaffolds and this is a major area for development. Recent developments in biomaterials have emphasised the importance of the physical, chemical and mechanical properties specific to a particular ophthalmic application. Materials science has a critical role in developing strategies to overcome vision loss. 相似文献
74.
The Scottish model of national parks reflects wider changes in the management of special or protected landscapes. This paper uses Ingold's dwelling conceptualisation of landscape to reflect on how material and cultural processes affect stakeholders' perceptions of the Cairngorms National Park in Scotland, UK. Important to understanding different views, is the separation, unique to the Cairngorms, of ‘the park’ from its management organisation. The paper argues that this separation creates a conceptual space for the negotiation of contested claims regarding the park. Such claims reflect not only the relationship between people and place, or as Ingold (2000) puts it, the landscape as it is known to those who dwell in it; they also represent vested interests and regimes of power concerning what happens in specific places. These claims do not reproduce simple splits between, for example, public/private or conservation/development but show a more complex picture. 相似文献
75.
Rachel Bogardus Drew 《Housing Studies》2013,28(4):616-631
This paper offers a new perspective to explain how and why the U.S. federal government pursued a policy agenda that from the early-1990s promoted homeownership as the preferred housing tenure of choice for low-income households. Using policy design theory (Schneider &; Ingram 1997), this paper argues that the social constructions of homeownership, low-income households, and the private mortgage industry were instrumental in the development of policies to increase low-income homeownership. The benefits associated with homeownership, based on long-standing norms around success, stability, and the American Dream, justified government interventions to increase access to private mortgage markets for low-income households. This policy stance, however, did nothing to assist households with maintaining homeownership for the long term. The social constructions embedded in the rationales and implementation of these policies contributed to their failure to sustain homeownership and realize its benefits for low-income homeowners. 相似文献
76.
77.
Helen Hejin Park Rachel Heasley Leizhi Sun Vera Steinmann Rafael Jaramillo Katy Hartman Rupak Chakraborty Prasert Sinsermsuksakul Danny Chua Tonio Buonassisi Roy G. Gordon 《Progress in Photovoltaics: Research and Applications》2015,23(7):901-908
Thin‐film solar cells consisting of earth‐abundant and non‐toxic materials were made from pulsed chemical vapor deposition (pulsed‐CVD) of SnS as the p‐type absorber layer and atomic layer deposition (ALD) of Zn(O,S) as the n‐type buffer layer. The effects of deposition temperature and annealing conditions of the SnS absorber layer were studied for solar cells with a structure of Mo/SnS/Zn(O,S)/ZnO/ITO. Solar cells were further optimized by varying the stoichiometry of Zn(O,S) and the annealing conditions of SnS. Post‐deposition annealing in pure hydrogen sulfide improved crystallinity and increased the carrier mobility by one order of magnitude, and a power conversion efficiency up to 2.9% was achieved. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
78.
79.
Rachel Passos de Oliveira Santos Daniele Oliveira Castro Adhemar Coll Ruvolo‐Filho Elisabete Frollini 《应用聚合物科学杂志》2014,131(12)
This investigation focuses on the preparation of bio‐based composites from recycled poly (ethylene terephthalate) (PET) and sisal fibers (3 cm, 15 wt %), via thermopressing process. Plasticizers derived from renewable raw materials are used, namely, glycerol, tributyl citrate (TBC) and castor oil (CO), to decrease the melting point of the recycled PET (Tm ∼ 265°C), which is sufficiently high to initiate the thermal decomposition of the lignocellulosic fiber. All used materials are characterized by thermogravimetric analysis and differential scanning calorimetry, and the composites are also characterized via dynamic mechanical thermal analysis. The storage modulus (30°C) and the tan δ peak values of CT [PET/sisal/TBC] indicate that TBC also acts as a compatibilizing agent at the interface fiber/PET, as well as a plasticizer. To compare different processing methods, rheometry/thermopressing and compression molding are used to prepare the recycled PET/sisal/glycerol/CO composites. These two different methods of processing show no significant influence on the thermal properties of these composites. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40386. 相似文献
80.
Advanced Monte Carlo simulations of the adsorption of chiral alcohols in a homochiral metal‐organic framework 下载免费PDF全文
Zhiwei Qiao Ariana Torres‐Knoop David Dubbeldam David Fairen‐Jimenez Jian Zhou Randall Q. Snurr 《American Institute of Chemical Engineers》2014,60(6):2324-2334
Grand canonical Monte Carlo (GCMC) simulations with configurational biasing were used to study the enantioselective adsorption of four alkanols in a homochiral metal‐organic framework, known as hybrid organic‐inorganic zeolite analogue HOIZA‐1. Conventional GCMC simulations are not able to converge satisfactorily for this system due to the tight fit of the chiral alcohols in the narrow pores. However, parallel tempering and parallel mole‐fraction GCMC simulations overcome this problem. The simulations show that the enantioselective adsorption of the different (R,S)‐alkanols is due to the specific geometry of the chiral molecules relative to the pore size and shape. © 2014 American Institute of Chemical Engineers AIChE J, 60: 2324–2334, 2014 相似文献