全文获取类型
收费全文 | 2154篇 |
免费 | 76篇 |
国内免费 | 7篇 |
专业分类
电工技术 | 40篇 |
综合类 | 3篇 |
化学工业 | 468篇 |
金属工艺 | 49篇 |
机械仪表 | 52篇 |
建筑科学 | 45篇 |
矿业工程 | 5篇 |
能源动力 | 86篇 |
轻工业 | 155篇 |
水利工程 | 11篇 |
石油天然气 | 6篇 |
无线电 | 264篇 |
一般工业技术 | 416篇 |
冶金工业 | 266篇 |
原子能技术 | 8篇 |
自动化技术 | 363篇 |
出版年
2023年 | 21篇 |
2022年 | 57篇 |
2021年 | 93篇 |
2020年 | 57篇 |
2019年 | 60篇 |
2018年 | 69篇 |
2017年 | 66篇 |
2016年 | 61篇 |
2015年 | 57篇 |
2014年 | 64篇 |
2013年 | 157篇 |
2012年 | 96篇 |
2011年 | 126篇 |
2010年 | 87篇 |
2009年 | 92篇 |
2008年 | 109篇 |
2007年 | 80篇 |
2006年 | 68篇 |
2005年 | 59篇 |
2004年 | 55篇 |
2003年 | 34篇 |
2002年 | 34篇 |
2001年 | 21篇 |
2000年 | 27篇 |
1999年 | 24篇 |
1998年 | 66篇 |
1997年 | 48篇 |
1996年 | 49篇 |
1995年 | 30篇 |
1994年 | 29篇 |
1993年 | 31篇 |
1992年 | 27篇 |
1991年 | 24篇 |
1990年 | 15篇 |
1989年 | 19篇 |
1988年 | 15篇 |
1987年 | 13篇 |
1986年 | 15篇 |
1984年 | 16篇 |
1983年 | 20篇 |
1982年 | 8篇 |
1981年 | 10篇 |
1980年 | 9篇 |
1979年 | 10篇 |
1978年 | 10篇 |
1977年 | 14篇 |
1976年 | 17篇 |
1974年 | 11篇 |
1973年 | 9篇 |
1972年 | 8篇 |
排序方式: 共有2237条查询结果,搜索用时 15 毫秒
71.
Clustering-Based Denoising With Locally Learned Dictionaries 总被引:4,自引:0,他引:4
In this paper, we propose K-LLD: a patch-based, locally adaptive denoising method based on clustering the given noisy image into regions of similar geometric structure. In order to effectively perform such clustering, we employ as features the local weight functions derived from our earlier work on steering kernel regression . These weights are exceedingly informative and robust in conveying reliable local structural information about the image even in the presence of significant amounts of noise. Next, we model each region (or cluster)-which may not be spatially contiguous-by ldquolearningrdquo a best basis describing the patches within that cluster using principal components analysis. This learned basis (or ldquodictionaryrdquo) is then employed to optimally estimate the underlying pixel values using a kernel regression framework. An iterated version of the proposed algorithm is also presented which leads to further performance enhancements. We also introduce a novel mechanism for optimally choosing the local patch size for each cluster using Stein's unbiased risk estimator (SURE). We illustrate the overall algorithm's capabilities with several examples. These indicate that the proposed method appears to be competitive with some of the most recently published state of the art denoising methods. 相似文献
72.
73.
In this paper we evaluate several routing protocols for mobile, wireless, ad hoc networks via packetlevel simulations. The ad hoc networks are multihop wireless networks with dynamically changing network connectivity owing to mobility. The protocol suite includes several routing protocols specifically designed for ad hoc routing, as well as more traditional protocols, such as link state and distance vector, used for dynamic networks. Performance is evaluated with respect to fraction of packets delivered, endtoend delay, and routing load for a given traffic and mobility model. Both small (30 nodes) and medium sized (60 nodes) networks are used. It is observed that the new generation of ondemand routing protocols use much lower routing load, especially with small number of peertopeer conversations. However, the traditional link state and distance vector protocols provide, in general, better packet delivery and endtoend delay performance. 相似文献
74.
Ingudam Shakuntala Samir Das Sandeep Ghatak Rajkumari Sanjukta Kekungu-U Puro 《Food Biotechnology》2019,33(3):237-250
Listeria monocytogenes is a pathogenic microorganism infects man mostly through food. A total of 1615 samples of foods of animal origin and water were collected from retail meat shops of North-Eastern India and processed. Sixty-three (3.9%) samples were positive for L. monocytogenes. Animal origin foods showing the highest prevalence was chevon (9.8%) followed by beef (8.9%), chicken (8.5%), pork (2.8%) and milk (1.8%). The prevalence rate in water from retail meat shops was 10%. Recovered L. monocytogenes were distributed into 3 serogroups, of which 74.6% fit in to 1/2a, 3a serogroup, 17.5% to 1/2b, 3b and 7.9 % to 4b, 4d, 4e serogroups. Thirty-five isolates out of 63 possessed all the tested four virulence genes. RAPD- and ERIC -PCR based analyses jointly revealed a discriminative genetic profile for the L. monocytogenes. On the whole, the occurrence of L. monocytogenes in foods of animal origin of North Eastern India displays public health hazard. 相似文献
75.
Nathaniel A. Riordan Chaturvedi Gogineni Shane R. Johnson Xianfeng Lu Tom Tiedje Ding Ding Yong-Hang Zhang Rafael Fritz Kolja Kolata Sangam Chatterjee Kerstin Volz Stephan W. Koch 《Journal of Materials Science: Materials in Electronics》2012,23(10):1799-1804
Bulk and quantum well GaAs1?xBix/GaAs layers with Bi mole fractions from 0.02 to 0.10 are grown by molecular-beam epitaxy at temperatures ranging from 280 to 320?°C. The samples are characterized using temperature and pump-power dependent photoluminescence measurements covering 8–300?K and 1–250?mW (7–1,800?W/cm2), respectively. The results indicate that there is strong reduction in bandgap energy with the incorporation of small amounts of Bi and that GaAsBi most likely forms a weak type-I band alignment with GaAs. 相似文献
76.
77.
Debjani Ghosh Shruti S. Bandyopadhyay Udipta R. Chatterjee Peter Capek Bimalendu Ray 《Food science and biotechnology》2012,21(2):409-417
Chirata (Swertia chirata) is widely used in Indian folk medicine for the prevention of various disorders. Herein, we analyzed the water-extracted
carbohydrate polymer (WECP) of this herb using chemical, chromatographic, and spectroscopic methods. The anti-oxidant capacity
of this fraction was studied by ferric reducing anti-oxidant power (FRAP) and DPPH radical assays. Effect of WECP on bovine
serum albumin spectrum (BSA) was determined using excitation wavelength of 282 nm. Anion exchange chromatography of WECP yielded
5 fractions (F1–F5) with different chemical compositions. The major fraction (F5) was homogeneous, had an apparent molecular
mass of 4.5 kDa, and contains both carbohydrates (57%) and phenolics (34%). The anti-oxidant capacities of WECP and F5 were
comparable to standard anti-oxidants. Notably, activities of the carbohydrate polymers (F1–F5) correlate with their phenolics
content. Fluorescence quenching measurement suggests that F5 can form complex with BSA and the value of the binding constant
is K=6.28×105/M. 相似文献
78.
Sk. Manirul Islam Kajari Ghosh Anupam Singha Roy Noor Salam Tanmay Chatterjee 《Journal of Inorganic and Organometallic Polymers and Materials》2014,24(2):457-467
A polymer-anchored iron(III) catalyst was synthesized and characterized. Its catalytic activity was evaluated for the oxidation of various alkenes, sulfides, aromatic alcohols and ethylbenzene with 30 % H2O2 as the oxidizing agent. The catalyst was also effective for the oxidative bromination reaction with 80–100 % selectivity of monobrominated products with H2O2/KBr at room temperature. The above reactions require a minimum amount of H2O2 and short reaction time. Most importantly, all the above reactions occur in aqueous medium. The catalyst can be facilely recovered and reused six-atimes without significant decrease in its activity and selectivity. 相似文献
79.
Chatterjee Gaurav Latorre Laurent Mailly Frédérick Nouet Pascal Hachelef Nacim Oudea Coumar 《Microsystem Technologies》2017,23(9):3969-3978
Microsystem Technologies - Inertial measurement units (IMU) are essentially a combination of acceleration and rotation rate sensors, generating position and attitude information. For tactical and... 相似文献
80.