首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   179341篇
  免费   2206篇
  国内免费   703篇
电工技术   3456篇
综合类   106篇
化学工业   28397篇
金属工艺   7852篇
机械仪表   5143篇
建筑科学   4443篇
矿业工程   878篇
能源动力   4749篇
轻工业   16539篇
水利工程   1703篇
石油天然气   3128篇
武器工业   2篇
无线电   20083篇
一般工业技术   33651篇
冶金工业   33821篇
原子能技术   4347篇
自动化技术   13952篇
  2021年   1347篇
  2019年   1254篇
  2018年   2119篇
  2017年   2105篇
  2016年   2233篇
  2015年   1590篇
  2014年   2763篇
  2013年   7866篇
  2012年   4608篇
  2011年   6447篇
  2010年   5089篇
  2009年   5969篇
  2008年   5946篇
  2007年   5904篇
  2006年   5079篇
  2005年   4743篇
  2004年   4526篇
  2003年   4200篇
  2002年   4164篇
  2001年   4168篇
  2000年   3962篇
  1999年   4121篇
  1998年   10668篇
  1997年   7575篇
  1996年   5776篇
  1995年   4344篇
  1994年   3683篇
  1993年   3643篇
  1992年   2644篇
  1991年   2574篇
  1990年   2443篇
  1989年   2464篇
  1988年   2399篇
  1987年   2148篇
  1986年   2084篇
  1985年   2393篇
  1984年   2201篇
  1983年   2033篇
  1982年   1895篇
  1981年   1959篇
  1980年   1812篇
  1979年   1829篇
  1978年   1793篇
  1977年   2127篇
  1976年   2723篇
  1975年   1563篇
  1974年   1557篇
  1973年   1614篇
  1972年   1354篇
  1971年   1264篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Davyhulme sewage-treatment works, which serves the Manchester drainage area, is one of the lagest in the UK. The dry-weather flow is 300 000 m3/d, and the plant receives a wide range of industrial effluents. The works has been identified as a major source of pollution in the Mersey estuary, with an average discharge of 6500 kg ammonia/day. As part of its initiative to improve the Mersey estuary, North West Water intends to reduce the daily ammonia load from Davyhulme to about 1000 kg/d by 1995. In order to assess the capabilities of both conventional and novel processes to achieve this degree of ammonia removal, a number of on-site pilot plants were established. This paper reports on the pilot-plant studies and the selection of process options. Recommendations with regard to design parameters and final process selection are given.  相似文献   
62.
Fibre Chemistry - Modification of polycaproamide by 1H,1H,13H-trihydroperfluorotridecan-1-ol immobilized on montmorillonite produced an F-containing polymer composite. The structure of the...  相似文献   
63.
Theoretical Foundations of Chemical Engineering - A new approach to the processing of the dump waste product stored in the tailings dumps of the nickel production enterprise Punda Gourda (Cuba) has...  相似文献   
64.
Russian Engineering Research - Polymer samples based on polydicyclopentadiene produced from Russian dicyclopentadiene are investigated by thermogravimetric analysis and differential scanning...  相似文献   
65.
We analyze a simple laser reflectivity measurement as a tool to monitor the drying kinetics of transparent polymer films. The reflectivity signal of a laser beam at normal incidence shows oscillations due to interference arising from multiple reflection of the laser light within the drying film. We develop a model to interpret the reflectivity curves in terms of time evolving refractive indices at the top and bottom of the film. We present results of the drying kinetics of transparent alkyd films on a glass substrate of high refractive index. Data shows a clear hallmark indicating the evolution of the crosslinking process. From the reflectivity curves, the time evolution of the refractive indices at the top and bottom is obtained. Assuming a linear-gradient of the refractive index along the depth of the film the average refractive index and consequently the film thickness as a function of time are estimated. Clear features in the time evolution of the refractive indices and thickness, correlate well with qualitative “dust”, “touch” and “fingerprint” drying times. Additionally, we present some preliminary results for water based latex binders, where scattering of light is present, showing that this simple optical technique could be extended for studying latex film formation.  相似文献   
66.
This study presents a Laser Zone Melting method with potential for producing planar waveguides at large scale, based on the surface coupling of two chemically compatible glass layers which exhibit distinct indices of refraction. The method is based on a recent patent, particularly applicable to process glass and ceramics with low thermal shock resistance. Glass coatings containing 76.24% by weight PbO are thus here reported, as obtained by this method on commercial soda-lime planar glass substrates. Their higher indices of refraction (1.58 vs 1.52 for commercial soda-lime glass) result in attractive waveguiding potential, as demonstrated with measurements using focused light from a He-Ne laser beam. Scanning and transmission electron microscopy studies reveal excellent integration and compatibility between the observed coatings and substrates, where diffusion in the proximity of the interface was studied by EDS analysis. Crystalline phases have not been found within the coating, or within the substrate, as concluded from the absence of Bragg-peaks in XRD experiments.  相似文献   
67.
Vogelsang  David F.  Maleczka  Robert E.  Lee  Andre 《SILICON》2022,14(13):7555-7565
Silicon - Bisfunctional dichlorosilanes were reacted with tetrasilanol of double-decker shaped octaphenylsilsesquioxane (DDSQ) to form fully condensed DDSQ compounds. The crystallographic and...  相似文献   
68.
Phenoxybenzamine (PBZ) is an FDA approved α-1 adrenergic receptor antagonist that is currently used to treat symptoms of pheochromocytoma. However, it has not been studied as a neuroprotective agent for traumatic brain injury (TBI). While screening neuroprotective candidates, we found that phenoxybenzamine reduced neuronal death in rat hippocampal slice cultures following exposure to oxygen glucose deprivation (OGD). Using this system, we found that phenoxybenzamine reduced neuronal death over a broad dose range (0.1 μM–1 mM) and provided efficacy when delivered up to 16 h post-OGD. We further tested phenoxybenzamine in the rat lateral fluid percussion model of TBI. When administered 8 h after TBI, phenoxybenzamine improved neurological severity scoring and foot fault assessments. At 25 days post injury, phenoxybenzamine treated TBI animals also showed a significant improvement in both learning and memory compared to saline treated controls. We further examined gene expression changes within the cortex following TBI. At 32 h post-TBI phenoxybenzamine treated animals had significantly lower expression of pro-inflammatory signaling proteins CCL2, IL1β, and MyD88, suggesting that phenoxybenzamine may exert a neuroprotective effect by reducing neuroinflammation after TBI. These data suggest that phenonxybenzamine may have application in the treatment of TBI.  相似文献   
69.
Metals and Materials International - In the present work, Ni32-x-Ti-Ta18+x (x?=?0, 2, 3, 4, 5, 6, 7, 8) shape memory alloys, produced by arc-melting method. Then, differential scanning...  相似文献   
70.
We previously reported that a novel peptide vaccine platform, based on synthetic melanin nanoaggregates, triggers strong cytotoxic immune responses and significantly suppresses tumor growth in mice. However, the mechanisms underlying such an efficacy remained poorly described. Herein, we investigated the role of dendritic cells (DCs) in presenting the antigen embedded in the vaccine formulation, as well as the potential stimulatory effect of melanin upon these cells, in vitro by coculture experiments and ELISA/flow cytometry analysis. The vaccine efficiency was evaluated in FLT3-L−/− mice constitutively deficient in DC1, DC2, and pDCs, in Zbtb46DTR chimera mice deficient in DC1 and DC2, and in LangerinDTR mice deficient in dermal DC1 and Langerhans cells. We concluded that DCs, and especially migratory conventional type 1 dendritic cells, seem crucial for mounting the immune response after melanin-based vaccination. We also assessed the protective effect of L-DOPA melanin on peptides from enzymatic digestion, as well as the biodistribution of melanin–peptide nanoaggregates, after subcutaneous injection using [18F]MEL050 PET imaging in mice. L-DOPA melanin proved to act as an efficient carrier for peptides by fully protecting them from enzymatic degradation. L-DOPA melanin did not display any direct stimulatory effects on dendritic cells in vitro. Using PET imaging, we detected melanin–peptide nanoaggregates up to three weeks after subcutaneous injections within the secondary lymphoid tissues, which could explain the sustained immune response observed (up to 4 months) with this vaccine technology.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号