全文获取类型
收费全文 | 3032篇 |
免费 | 121篇 |
国内免费 | 23篇 |
专业分类
电工技术 | 66篇 |
综合类 | 2篇 |
化学工业 | 651篇 |
金属工艺 | 104篇 |
机械仪表 | 81篇 |
建筑科学 | 43篇 |
矿业工程 | 4篇 |
能源动力 | 114篇 |
轻工业 | 148篇 |
水利工程 | 26篇 |
石油天然气 | 30篇 |
无线电 | 317篇 |
一般工业技术 | 669篇 |
冶金工业 | 498篇 |
原子能技术 | 38篇 |
自动化技术 | 385篇 |
出版年
2023年 | 44篇 |
2022年 | 57篇 |
2021年 | 89篇 |
2020年 | 103篇 |
2019年 | 73篇 |
2018年 | 89篇 |
2017年 | 105篇 |
2016年 | 97篇 |
2015年 | 71篇 |
2014年 | 105篇 |
2013年 | 242篇 |
2012年 | 109篇 |
2011年 | 158篇 |
2010年 | 134篇 |
2009年 | 127篇 |
2008年 | 134篇 |
2007年 | 130篇 |
2006年 | 99篇 |
2005年 | 69篇 |
2004年 | 65篇 |
2003年 | 56篇 |
2002年 | 58篇 |
2001年 | 44篇 |
2000年 | 48篇 |
1999年 | 44篇 |
1998年 | 110篇 |
1997年 | 83篇 |
1996年 | 54篇 |
1995年 | 60篇 |
1994年 | 68篇 |
1993年 | 30篇 |
1992年 | 27篇 |
1991年 | 26篇 |
1990年 | 32篇 |
1989年 | 23篇 |
1988年 | 28篇 |
1987年 | 20篇 |
1986年 | 22篇 |
1985年 | 27篇 |
1984年 | 19篇 |
1983年 | 18篇 |
1982年 | 14篇 |
1981年 | 12篇 |
1980年 | 17篇 |
1979年 | 15篇 |
1978年 | 15篇 |
1977年 | 18篇 |
1976年 | 29篇 |
1975年 | 13篇 |
1971年 | 9篇 |
排序方式: 共有3176条查询结果,搜索用时 470 毫秒
111.
Swapan Kumar Ghosh Rajib Bhattacharyya Murari Mohan Mondal Tapobrata Sanyal 《Journal of Natural Fibers》2015,12(5):457-480
In the last quarter of the twentieth century, a new class of materials, Geosynthetics, emerged prospectively leading significant innovation in the design of geotechnical and geoenvironmental systems. Geotextiles have proven to be among the most versatile and techno-economically viable ground modification materials playing a significant role in modern pavement design and maintenance techniques. With the growing environmental concern across the globe, technologists, researchers have inclined towards the natural geotextile where Jute Geotextile (JGT) is one of the potential candidates. But, JGT has been restricted mainly as underlay in road construction. Hence, there is an urgent need to design and develop a precise innovative fabric as overlay on existing pavements and other emerging civil works to stay technically and economically competitive in the global market. Such a fabric will not only prove techno-economically viable but will also reduce the carbon foot-print generation to a large extent. This paper delineates the development of Grey Jute Paving Fabric (GJPF) followed by its bituminization with suitable type and grade of bitumen to develop Bituminized Jute Paving Fabric (BJPF). The BJPF will enhance the life of the overlay thereby reducing the cost of maintenance as well as serving as a partial substitute of bitumen mastic. 相似文献
112.
Carbodithioate esters are important functional organosulfur compounds widely used in diverse fields such as pharmaceuticals, agrochemicals and material sciences. Common preparative methods include reaction of alkyl halides, carbon disulfide and bases under both metal-free and metal-catalyzed conditions. However, organyl thiocyanates have not been previously explored, possibly because of their conversion to organyl disulfides under basic conditions. Here, we report an efficient and practical method for the preparation of libraries of carbodithioate esters from organyl thiocyanates by reacting with cyclic amine-based dithiocarbamic acid salts in water. The protocol is found to be applicable in general to various thiocyanates such as benzyl/aroyl methyl/cinnamyl and so on. Other notable features include no by-products such as disulfides, metal- and alkali-free, aqueous conditions, and finally easy and near-quantitative formation of cyclic amine-based dithiocarbamic acid salt as a stable alternative reagent. 相似文献
113.
114.
Debrupa Lahiri Sanat Ghosh Arvind Agarwal 《Materials science & engineering. C, Materials for biological applications》2012,32(7):1727-1758
Application of hydroxyapatite (HA) in orthopedic implants suffers from its low fracture toughness and poor wear resistance. Carbon nanotube (CNT), with its high stiffness and mechanical strength, is an attractive reinforcement for HA to surmount these issues. The last 7–8 years have seen a number of studies to explore the efficiency of CNT reinforcement in strengthening HA, in the form of composites and coatings. Impressive improvement in the fracture toughness and wear resistance of HA with CNT reinforcement and beneficial effects on biocompatibility has sparked further research interests, for possible clinical applications. This review article aims to cover a wide span of this exciting and expanding research arena – from detailed technical discussions on HA–CNT system, their processing techniques and the influence of CNT dispersion in the HA matrix. Role of CNT in the improvement of mechanical properties and tribological behavior of the composite has been discussed in light of different processing techniques. Other important issues related to HA–CNT system, e.g., phase transformation and crystallinity of HA and HA–CNT interfacial bonding has been stressed upon. Biocompatibility of HA–CNT composites, which is extremely important for its intended orthopedic application, has been summarized with an overview of the present status. An in-depth analysis of the information presented in this review facilitates a better understanding of the current state of HA–CNT research and allows framing guidelines toward future research direction for its successful clinical application. 相似文献
115.
116.
117.
Diversity of culturable bacterial populations within the Arsenic (As) contaminated groundwater of North Eastern state (Assam) of India is studied. From nine As contaminated samples 89 bacterial strains are isolated. 16S rRNA gene sequence analysis reveals predominance of Brevundimonas (35%) and Acidovorax (23%) along with Acinetobacter (10%), Pseudomonas (9%) and relatively less abundant (<5%) Undibacterium, Herbaspirillum, Rhodococcus, Staphylococcus, Bosea, Bacillus, Ralstonia, Caulobacter and Rhizobiales members. High As(III) resistance (MTC 10–50 mM) is observed for the isolates obtained from As(III) enrichment, particularly for 3 isolates of genus Brevundimonas (MTC 50 mM). In contrast, high resistance to As(V) (MTC as high as 550 mM) is present as a ubiquitous property, irrespective of isolates' enrichment condition. Bacterial genera affiliated to other groups showed relatively lower degree of As resistance [MTCs of 15–20 mM As(III) and 250–350 mM As(V)]. As(V) reductase activity is detected in strains with high As(V) as well as As(III) resistance. A strong correlation could be established among isolates capable of reductase activity and siderophore production as well as As(III) tolerance. A large number of isolates (nearly 50%) is capable of anaerobic respiration using alternate inorganic electron acceptors [As(V), Se(VI), Fe(III), 3NO2−, 4SO2−, S2O32−]. Ability to utilize different carbon sources ranging from C2–C6 compounds along with some complex sugars is also observed. Particularly, a number of strains is found to possess ability to grow chemolithotrophically using As(III) as the electron donor. The study reports for the first time the identity and metabolic abilities of bacteria in As contaminated ground water of North East India, useful to elucidate the microbial role in influencing mobilization of As in the region. 相似文献
118.
Ghosh Enakshi Sasidharan Aswathi Ode Paul J. Venkatesan Radhika 《Journal of chemical ecology》2022,48(7-8):670-682
Journal of Chemical Ecology - Insect herbivores frequently must balance host plant quality and the risk of attack by their natural enemies when making oviposition decisions. Yet, which factor is... 相似文献
119.
This article presents numerical simulations of the laminar flow of lubricating greases in a channel with rectangular cross section. Three greases with different consistencies (NLGI grades 00, 1, and 2) have been considered in three different configurations composed of a rectangular channel without restrictions, one rectangular step restriction, and one double-lip restriction. The driving pressure drop over the channel spans from 30 to 250 kPa. The grease rheology is described by the Herschel-Bulkley rheology model, and both the numerical code and rheology model have been validated with analytical solutions and flow measurements using micro-particle image velocimetry. 相似文献
120.
Santosh K. Gupta Maya Abdou Partha S. Ghosh Jose P. Zuniga Ezhilarasan Manoharan HyeongJun Kim Yuanbing Mao 《Journal of the American Ceramic Society》2020,103(1):235-248
Unveiling the underlying mechanisms of properties of functional materials, including the luminescence differences among similar pyrochlores A2B2O7, opens new gateways to select proper hosts for various optoelectronic applications by scientists and engineers. For example, although La2Zr2O7 (LZO) and La2Hf2O7 (LHO) pyrochlores have similar chemical compositional and crystallographic structural features, they demonstrate different luminescence properties both before and after doped with Eu3+ ions. Based on our earlier work, LHO-based nanophosphors display higher photo- and radioluminescence intensity, higher quantum efficiency, and longer excited state lifetime compared to LZO-based nanophosphors. Moreover, under electronic O2−→Zr4+/Hf4+ transition excitation at 306 nm, undoped LHO nanoparticles (NPs) have only violet blue emission, whereas LZO NPs show violet blue and red emissions. In this study, we have combined experimental and density functional theory (DFT) based theoretical calculation to explain the observed results. First, we calculated the density of state (DOS) based on DFT and studied the energetics of ionized oxygen vacancies in the band gaps of LZO and LHO theoretically, which explain their underlying luminescence difference. For Eu3+-doped NPs, we performed emission intensity and lifetime calculations and found that the LHOE NPs have higher host to dopant energy transfer efficiency than the LZOE NPs (59.3% vs 24.6%), which accounts for the optical performance superiority of the former over the latter. Moreover, by corroborating our experimental data with the DFT calculations, we suggest that the Eu3+ doping states in LHO present at exact energy position (both in majority and minority spin components) where oxygen defect states are located unlike those in LZO. Lastly, both the NPs show negligible photobleaching highlighting their potential for bioimaging applications. This current report provides a deeper understanding of the advantages of LHO over LZO as an advanced host for phosphors, scintillators, and fluoroimmunoassays. 相似文献