全文获取类型
收费全文 | 106614篇 |
免费 | 11726篇 |
国内免费 | 7549篇 |
专业分类
电工技术 | 9162篇 |
技术理论 | 2篇 |
综合类 | 10119篇 |
化学工业 | 14212篇 |
金属工艺 | 7366篇 |
机械仪表 | 7482篇 |
建筑科学 | 7902篇 |
矿业工程 | 3725篇 |
能源动力 | 3265篇 |
轻工业 | 8954篇 |
水利工程 | 3098篇 |
石油天然气 | 4756篇 |
武器工业 | 1552篇 |
无线电 | 12205篇 |
一般工业技术 | 9990篇 |
冶金工业 | 4593篇 |
原子能技术 | 1628篇 |
自动化技术 | 15878篇 |
出版年
2024年 | 435篇 |
2023年 | 1364篇 |
2022年 | 3327篇 |
2021年 | 4562篇 |
2020年 | 3325篇 |
2019年 | 2426篇 |
2018年 | 2711篇 |
2017年 | 3130篇 |
2016年 | 2989篇 |
2015年 | 4537篇 |
2014年 | 5742篇 |
2013年 | 6821篇 |
2012年 | 8686篇 |
2011年 | 9065篇 |
2010年 | 8624篇 |
2009年 | 8276篇 |
2008年 | 8354篇 |
2007年 | 7810篇 |
2006年 | 6868篇 |
2005年 | 5631篇 |
2004年 | 4303篇 |
2003年 | 3588篇 |
2002年 | 3641篇 |
2001年 | 3191篇 |
2000年 | 2086篇 |
1999年 | 1299篇 |
1998年 | 624篇 |
1997年 | 559篇 |
1996年 | 450篇 |
1995年 | 346篇 |
1994年 | 270篇 |
1993年 | 182篇 |
1992年 | 136篇 |
1991年 | 103篇 |
1990年 | 93篇 |
1989年 | 83篇 |
1988年 | 42篇 |
1987年 | 42篇 |
1986年 | 30篇 |
1985年 | 7篇 |
1984年 | 12篇 |
1983年 | 17篇 |
1982年 | 10篇 |
1981年 | 14篇 |
1980年 | 19篇 |
1979年 | 12篇 |
1978年 | 2篇 |
1975年 | 3篇 |
1959年 | 30篇 |
1951年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 171 毫秒
21.
In vivo Kinetic Biodistribution of Nano‐Sized Outer Membrane Vesicles Derived from Bacteria
下载免费PDF全文
![点击此处可从《Small (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Su Chul Jang Sae Rom Kim Yae Jin Yoon Kyong‐Su Park Ji Hyun Kim Jaewook Lee Oh Youn Kim Eun‐Jeong Choi Dae‐Kyum Kim Dong‐Sic Choi Yoon‐Keun Kim Jaesung Park Dolores Di Vizio Yong Song Gho 《Small (Weinheim an der Bergstrasse, Germany)》2015,11(4):456-461
Evaluation of kinetic distribution and behaviors of nanoparticles in vivo provides crucial clues into their roles in living organisms. Extracellular vesicles are evolutionary conserved nanoparticles, known to play important biological functions in intercellular, inter‐species, and inter‐kingdom communication. In this study, the first kinetic analysis of the biodistribution of outer membrane vesicles (OMVs)—bacterial extracellular vesicles—with immune‐modulatory functions is performed. OMVs, injected intraperitoneally, spread to the whole mouse body and accumulate in the liver, lung, spleen, and kidney within 3 h of administration. As an early systemic inflammation response, increased levels of TNF‐α and IL‐6 are observed in serum and bronchoalveolar lavage fluid. In addition, the number of leukocytes and platelets in the blood is decreased. OMVs and cytokine concentrations, as well as body temperature are gradually decreased 6 h after OMV injection, in concomitance with the formation of eye exudates, and of an increase in ICAM‐1 levels in the lung. Following OMV elimination, most of the inflammatory signs are reverted, 12 h post‐injection. However, leukocytes in bronchoalveolar lavage fluid are increased as a late reaction. Taken together, these results suggest that OMVs are effective mediators of long distance communication in vivo. 相似文献
22.
23.
Yong Xu Yun Li Songlin Li Francis Balestra Gerard Ghibaudo Wenwu Li Yen‐Fu Lin Huabin Sun Jing Wan Xinran Wang Yufeng Guo Yi Shi Yong‐Young Noh 《Advanced functional materials》2020,30(20)
Unreliable mobility values, and particularly greatly overestimated values and severely distorted temperature dependences, have recently hampered the development of the organic transistor field. Given that organic field‐effect transistors (OFETs) have been routinely used to evaluate mobility, precise parameter extraction using the electrical properties of OFETs is thus of primary importance. This review examines the origins of the various mobilities that must be determined for OFET applications, the relevant extraction methods, and the data selection limitations, which help in avoiding conceptual errors during mobility extraction. For increased precision, the review also discusses device fabrication considerations, calibration of both the specific gate‐dielectric capacitance and the threshold voltage, the contact effects, and the bias and temperature dependences, which must actually be handled with great care but have mostly been overlooked to date. This review serves as a systematic overview of the OFET mobility extraction process to ensure high precision and will also aid in improving future research. 相似文献
24.
积分中值屈服准则解析厚板轧制椭圆速度场 总被引:1,自引:0,他引:1
为解决非线性Mises比塑性功率积分困难以及由此导致的轧制功率解析式难以获得的问题,本文通过建立并利用线性比塑性功率表达式对提出的椭圆速度场进行能量分析,得到了轧制力能参数的解析解.文中通过对变角度屈服函数求积分中值,构建了一个新的屈服准则,它是主应力分量的线性组合,在π平面上的轨迹是逼近Mises圆的等边非等角的十二边形,其基于Lode参数表达式的理论结果也与实验数据吻合较好.同时,根据厚板轧制时金属流动速度从入口到出口逐渐增大的特点,提出了水平速度分量满足椭圆方程的速度场,该速度场满足运动许可条件.通过相应的轧制能量分析,获得了基于线性屈服准则的内部变形功率以及基于应变矢量内积法上的摩擦功率与剪切功率.在此之上,通过泛函的极值变分导出了轧制力矩、轧制力以及应力状态系数的解析解,并与现场实测数据进行了对比,结果表明利用本文提出的屈服准则与速度场所建立的轧制力矩与轧制力模型与实测值吻合较好,其中轧制力误差小于5.3%,轧制力矩误差在6%左右. 相似文献
25.
26.
27.
28.
In this study, 30 subjects were exposed to different combinations of air temperature (Ta: 24, 27, and 30°C) and CO2 level (8000, 10 000, and 12 000 ppm) in a high-humidity (RH: 85%) underground climate chamber. Subjective assessments, physiological responses, and cognitive performance were investigated. The results showed that as compared with exposure to Ta = 24°C, exposure to 30°C at all CO2 levels caused subjects to feel uncomfortably warm and experience stronger odor intensity, while increased mental effort and greater intensity of acute health symptoms were reported. However, no significant effects of Ta on task performance or physiological responses were found. This indicated that subjects had to exert more effort to maintain their performance in an uncomfortably warm environment. Increasing CO2 from 8000 to 12 000 ppm at all Ta caused subjects to report higher rates of headache, fatigue, agitation, and feeling depressed, although the results were statistically significant only at 24 and 27°C. The text typing performance and systolic blood pressure (SBP) decreased significantly at this exposure, whereas diastolic blood pressure (DBP) and thermal discomfort increased significantly. These effects suggest higher arousal/stress. No significant interaction effect of Ta and CO2 concentration on human responses was identified. 相似文献
29.
田继业 《中国水能及电气化》2021,(5):4-8
随着我国经济的快速发展,基础设施建设中建筑工程日益增多,许多工程建设周期比较长,跨越了春夏秋冬,更有一部分地区,长期处于严寒强风地带,为了缩短施工工期,保证施工的正常进行,需要进行冬期施工.文章针对冬期施工在低温强风条件下的技术措施进行了总结,可为同类工程提供参考. 相似文献
30.
Bin Zhang Xuesong Jiang Fei Shen Xueming He Yong Fang Qiuhui Hu 《International Journal of Food Science & Technology》2021,56(6):2588-2595
This work intends to develop an online experimental system for screening of deoxynivalenol (DON) contamination in whole wheat meals by visible/near-infrared (Vis/NIR) spectroscopy and computer vision coupling technology. Spectral and image information of samples with various DON levels was collected at speed of 0.15 m s−1 on a conveyor belt. The two-type data were then integrated and subjected to chemometric analysis. Discriminant analysis showed that samples could be classified by setting 1000 μg kg−1 as the cut-off value. The best correct classified rate obtained in prediction was 93.55% based on fusion of spectral and image features, with reduced prediction uncertainty as compared to single feature. However, quantification of DON by quantitative analysis was not successful due to poor model performance. These results indicate that, although not accurate enough to provide conclusive result, this coupling technology could be adopted for rapid screening of DON contamination in cereals and feeds during processing. 相似文献