全文获取类型
收费全文 | 20862篇 |
免费 | 1532篇 |
国内免费 | 676篇 |
专业分类
电工技术 | 1016篇 |
技术理论 | 3篇 |
综合类 | 1250篇 |
化学工业 | 3763篇 |
金属工艺 | 999篇 |
机械仪表 | 1262篇 |
建筑科学 | 1605篇 |
矿业工程 | 436篇 |
能源动力 | 563篇 |
轻工业 | 1482篇 |
水利工程 | 337篇 |
石油天然气 | 1057篇 |
武器工业 | 155篇 |
无线电 | 2177篇 |
一般工业技术 | 3067篇 |
冶金工业 | 1161篇 |
原子能技术 | 249篇 |
自动化技术 | 2488篇 |
出版年
2024年 | 78篇 |
2023年 | 287篇 |
2022年 | 452篇 |
2021年 | 595篇 |
2020年 | 495篇 |
2019年 | 451篇 |
2018年 | 468篇 |
2017年 | 597篇 |
2016年 | 535篇 |
2015年 | 708篇 |
2014年 | 850篇 |
2013年 | 1099篇 |
2012年 | 1165篇 |
2011年 | 1260篇 |
2010年 | 1069篇 |
2009年 | 1032篇 |
2008年 | 1103篇 |
2007年 | 1054篇 |
2006年 | 1133篇 |
2005年 | 1102篇 |
2004年 | 693篇 |
2003年 | 658篇 |
2002年 | 607篇 |
2001年 | 522篇 |
2000年 | 677篇 |
1999年 | 728篇 |
1998年 | 626篇 |
1997年 | 553篇 |
1996年 | 493篇 |
1995年 | 456篇 |
1994年 | 337篇 |
1993年 | 248篇 |
1992年 | 209篇 |
1991年 | 170篇 |
1990年 | 134篇 |
1989年 | 116篇 |
1988年 | 90篇 |
1987年 | 44篇 |
1986年 | 48篇 |
1985年 | 43篇 |
1984年 | 18篇 |
1983年 | 5篇 |
1982年 | 14篇 |
1981年 | 13篇 |
1980年 | 11篇 |
1979年 | 6篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1976年 | 4篇 |
1970年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
The application of deep learning in the field of object detection has
experienced much progress. However, due to the domain shift problem, applying an
off-the-shelf detector to another domain leads to a significant performance drop. A
large number of ground truth labels are required when using another domain to train
models, demanding a large amount of human and financial resources. In order to avoid
excessive resource requirements and performance drop caused by domain shift, this
paper proposes a new domain adaptive approach to cross-domain vehicle detection. Our
approach improves the cross-domain vehicle detection model from image space and
feature space. We employ objectives of the generative adversarial network and cycle
consistency loss for image style transfer in image space. For feature space, we align
feature distributions between the source domain and the target domain to improve the
detection accuracy. Experiments are carried out using the method with two different
datasets, proving that this technique effectively improves the accuracy of vehicle
detection in the target domain. 相似文献
12.
13.
Multimedia Tools and Applications - In recent years, various chaotic maps have been used for image encryption. However, most of these image encryption algorithms entail a lot of floating-point... 相似文献
14.
Li D. You-Song Gu Xiang-Rong Chang Fu-Shen Li Li-Jie Qiao Zhong-Zhuo Tian Fang G.-D. Qing-Shan Song 《IEEE transactions on magnetics》2003,39(6):3554-3558
We deposited Fe-Ti-N magnetic films with a high sputtering power of 7 W/cm/sup 2/. When the composition of the films was in the range of Fe-Ti(3.9 at.%)-N(8.8 at.%) to Fe-Ti(3.3 at.%)-N(13.5 at.%), the films were composed of /spl alpha/' and Ti/sub 2/N precipitates. With the addition of nitrogen, 4/spl pi/M/sub s/ became higher than that of pure iron, reaching a maximum of 23.8 kG. At the same time, H/sub c/ was reduced to a minimum of 1.12 Oe. The best films can meet the needs of the recording head in dual-element giant magnetoresistive/inductive heads, yielding high storage density (10 Gb/in/sup 2/). The incorporation of N in /spl alpha/-Fe brought about the /spl alpha/' phase with its higher saturation magnetization. Ti additions inhibited the equilibrium decomposition /spl alpha/'/spl rarr//spl alpha/+/spl gamma/'. Because H/sub C//sup D//spl prop/D/sup 6/, where D is average grain diameter, grain size control is very important. The nitrogen induces severe distortion of the /spl alpha/' lattice, which can cause the grains to break into pieces and reduce the grain size. High sputtering power also led to the formation of fine grains, with diameter in the order of 14 nm. Probably Ti/sub 2/N is preferentially precipitated on the grain boundary, pinning the grain boundary and stabilizing the grain size during high-temperature heat treatment. The temperature limit for stability of the structure and its associated low coercivity was not less than 520/spl deg/C. 相似文献
15.
本文针对一往复式氢气压缩机管道振动十分强烈的情况,分析了管系的结构自振频率、气柱固有频率和气流脉动,采取了改变管系结构频率和气柱固有频率的减振措施,经实践证明获得了较为理想的减振效果。 相似文献
16.
E Messou SV Sangaré R Josseran C Le Corre J Guélain 《Canadian Metallurgical Quarterly》1997,90(1):44-47
BACKGROUND: Gastric sucrose permeability is a noninvasive marker that reliably increases in association with gastrointestinal injury due to use of nonsteroidal antiinflammatory drugs. Despite the effect of Helicobacter pylori infection on the gastric mucosa, in a previous study we were unable to demonstrate that H. pylori infection was associated with abnormal gastric sucrose permeability. Our goal in this study was to explore further whether H. pylori infection changed gastric permeability; therefore, we evaluated the effect of treatment of H. pylori infection on gastric permeability to sucrose and the relation of sucrose permeability to density of polymorphonuclear leukocytes. MATERIALS AND METHODS: Five hundred milliliters of a solution containing 100 gm of sucrose was ingested by the subject at bedtime. Overnight urine was collected and assayed for sucrose by high-performance liquid chromatography. Sucrose permeability was assessed both before and approximately 4 weeks after anti-H. pylori therapy. RESULTS: Seventeen asymptomatic H. pylori-infected volunteers participated; 8 were cured. Sucrose permeability was in the range commonly found in normal controls both before and after anti-H. pylori therapy (mean excretion, 76.3 mg; range, 13-171 mg). Gastric sucrose permeability correlated with the density of polymorphonulcear cell infiltration of the mucosa. Cure of the H. pylori infection was associated with a small but significant decrease in sucrose permeability (98.8 +/- 18 mg to 51.7 +/- 9.8 mg (p = .01). Sucrose permeability was greater in those with a high density of mucosal polymorphonuclear cells compared to those with lower scores (119.5 +/- 4 vs 71.4 +/- 13 for those with scores > or = 5 compared to scores < or = 4; p = .023). Failed therapy resulted in an increase in the mucosal density of polymorphonuclear infiltration and sucrose permeability (56.4 +/- 13 mg-99.7 +/- 19 mg pretreatment vs posttreatment, respectively; p = .031). CONCLUSION: H. pylori gastritis causes a small but measurable increase in gastric permeability to sucrose that may reflect epithelial transmigration of neutrophils. 相似文献
17.
设计并研制了一种用于压缩式致冷设备的电子式定温域多功能控制装置。它除具有控温范围宽、精度高、控温参数易调等优点外,还实现了低成本的温度显示、半自动除霜控制、加电延时保护、过欠压保护等功能。全部采用无触点控制方式,有良好的性能/价格比。 相似文献
18.
The purpose of this study is to examine the interface between financial strain, informal received economic support, informal anticipated financial support, and psychological distress in later life. Data provided by a large probability sample of older adults in the People's Republic of China reveal that the relationship between financial difficulty and psychological distress is stronger for older adults who receive more economic assistance. However, the results involving anticipated support are in the opposite direction. More specifically, the association between financial problems and psychological distress is lower for older adults who believe that others stand ready to help in the future should the need arise. A detailed theoretical rationale is developed to explain these results. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
19.
20.