全文获取类型
收费全文 | 137272篇 |
免费 | 3394篇 |
国内免费 | 605篇 |
专业分类
电工技术 | 1610篇 |
综合类 | 2399篇 |
化学工业 | 21541篇 |
金属工艺 | 6535篇 |
机械仪表 | 5675篇 |
建筑科学 | 3355篇 |
矿业工程 | 607篇 |
能源动力 | 3237篇 |
轻工业 | 7456篇 |
水利工程 | 1505篇 |
石油天然气 | 551篇 |
武器工业 | 1篇 |
无线电 | 18921篇 |
一般工业技术 | 27142篇 |
冶金工业 | 8274篇 |
原子能技术 | 880篇 |
自动化技术 | 31582篇 |
出版年
2023年 | 531篇 |
2022年 | 833篇 |
2021年 | 1403篇 |
2020年 | 993篇 |
2019年 | 1012篇 |
2018年 | 15408篇 |
2017年 | 14321篇 |
2016年 | 11305篇 |
2015年 | 1890篇 |
2014年 | 2245篇 |
2013年 | 3656篇 |
2012年 | 6174篇 |
2011年 | 12866篇 |
2010年 | 10848篇 |
2009年 | 8484篇 |
2008年 | 9396篇 |
2007年 | 9943篇 |
2006年 | 2346篇 |
2005年 | 3075篇 |
2004年 | 2927篇 |
2003年 | 2812篇 |
2002年 | 2156篇 |
2001年 | 1382篇 |
2000年 | 1375篇 |
1999年 | 1234篇 |
1998年 | 2242篇 |
1997年 | 1463篇 |
1996年 | 1245篇 |
1995年 | 969篇 |
1994年 | 735篇 |
1993年 | 691篇 |
1992年 | 501篇 |
1991年 | 516篇 |
1990年 | 417篇 |
1989年 | 404篇 |
1988年 | 330篇 |
1987年 | 275篇 |
1986年 | 254篇 |
1985年 | 231篇 |
1984年 | 199篇 |
1983年 | 151篇 |
1982年 | 152篇 |
1981年 | 130篇 |
1980年 | 129篇 |
1979年 | 102篇 |
1978年 | 94篇 |
1977年 | 123篇 |
1976年 | 158篇 |
1975年 | 80篇 |
1974年 | 74篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
Colour is the most widely used attribute in image retrieval and object recognition. A technique known as histogram intersection has been widely studied and is considered to be effective for color‐image indexing. The key issue of this algorithm is the selection of an appropriate color space and optimal quantization of the selected color space. The goal of this article is to measure the model performance in predicting human judgment in similarity measurement for various images, to explore the capability of the model with a wide set of color spaces, and to find the optimal quantization of the selected color spaces. Six color spaces and twelve quantization levels are involved in evaluating the performance of histogram intersection. The categorical judgment and rank order experiments were conducted to measure image similarity. The CIELAB color space was found to perform at least as good as or better than the other color spaces tested, and the ability to predict image similarity increased with the number of bins used in the histograms, for up to 512 bins (8 per channel). With more than 512 bins, further improvement was negligible for the image datasets used in this study. © 2005 Wiley Periodicals, Inc. Col Res Appl, 30, 265–274, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.20122 相似文献
22.
The biological decolorization of two industrial, spent textile reactive dyebaths was investigated using a suspended-growth, halophilic mixed culture fed with glucose. Dyebath I contained mainly Reactive Blue 19 (RB19), an anthraquinone dye, whereas dyebath II contained mainly Reactive Blue 21 (RB21), a phthalocyanine dye. Batch assays under anaerobic conditions with the two neutralized dyebaths resulted in 87 and 37% extent of decolorization for dyebaths I and II, respectively. The rate of glucose utilization and the extent of acetate production were impacted in the presence of each dyebath as compared to the control culture. However, dyebath decolorization occurred despite moderate culture inhibition. Reuse of a biologically renovated RB19-containing dyebath in the dyeing process resulted in reproducible but not identical cotton fabric shades as compared to a standard dyeing (i.e., control) using fresh water. This difference is attributed to a variable degree of RB19 aggregation during the dyeing process and is not related to the efficiency of the biodecolorization process. Further improvement of the redyeing efficiency will lead to the development of an in-plant, closed-loop decolorization system resulting in significant water conservation and minimization of textile pollutants such as salt and dyes. 相似文献
23.
24.
25.
26.
27.
28.
Dongwook Lee Kiseon Kim 《Electronics letters》1998,34(15):1474-1476
The authors suggest a novel virtual circuit connection method based on the reverse traversing technique to minimise the waste of network bandwidth resources, when the Internet protocol multicast is interoperated using the resource reservation protocol over an asynchronous transfer mode network. Simulation results show that, as the number of receivers increases, the bandwidth requirements on all links of the network of the proposed scheme become more advantageous than those of other conventional methods 相似文献
29.
Cheng-Hsiung Lid Shou-Chiung Chen Yung-Chi Lee Theodore D. Sokoloski Ming-Thau Sheu 《Drug development and industrial pharmacy》1994,20(11):1911-1922
Polyvinylpyrrolidone (PVP) in aqueous solution was used as a binding agent in a fluidized-bed system to agglomerate acetaminophen powder into directly compressible granules. It was found that a minimal amount of 5% w/w PVP in a concentration of 7.5% w/v or less was needed to produce granules with an acceptable flow and the corresponding tablets having enough hardness without capping. There was a strong correlation between the time for 80% dissolved (T80) and the logarithm of granule volume-surface mean diameter. A directly compressible acetaminophen composition to manufacture tablets having a T80 value less than 30 min can be prepared simply by adding an appropriate amount of disintegrant (crospovidone, sodium starch glycolate, or pregelatinized starch) to the agglomerated granules. 相似文献
30.
We developed a new in vitro model of neuronal injury using NT2-N cells to examine the effects of hydrodynamic loading rate on intraneuronal calcium dynamics and lactate dehydrogenase (LDH) release. Our apparatus consisted of a parallel disk viscometer which induced fluid shear stress with well-defined magnitudes and loading rates to cultured cells. We found that the deformation response of the cells was dependent on the severity of the insult, with increased cellular strains generated for higher shear stresses at a constant loading rate. Peak intracellular free calcium concentration correlated with strain, suggesting that mechanical deformation may regulate calcium response. Slowly applied fluid shear stress elicited no response, whereas high loading rates resulted in peak calcium increases 2.9 to 3.6 times baseline values as injury severity was increased. LDH release measured within 5 min after the insult correlated with loading rate. In addition, LDH release continued to increase out to 24 h following high loading rate conditions, demonstrating that the application of fluid shear stress led to prolonged cell damage. The acute response in NT2-N cells subjected to an insult with the CSID is dependent on the loading rate, and these results suggest that initial membrane deformation may trigger subsequent events. 相似文献