全文获取类型
收费全文 | 300809篇 |
免费 | 27506篇 |
国内免费 | 16202篇 |
专业分类
电工技术 | 20039篇 |
技术理论 | 14篇 |
综合类 | 21950篇 |
化学工业 | 46458篇 |
金属工艺 | 17366篇 |
机械仪表 | 19349篇 |
建筑科学 | 24467篇 |
矿业工程 | 8689篇 |
能源动力 | 8436篇 |
轻工业 | 23247篇 |
水利工程 | 6497篇 |
石油天然气 | 13867篇 |
武器工业 | 2759篇 |
无线电 | 36117篇 |
一般工业技术 | 34739篇 |
冶金工业 | 14245篇 |
原子能技术 | 3937篇 |
自动化技术 | 42341篇 |
出版年
2024年 | 1098篇 |
2023年 | 4514篇 |
2022年 | 8813篇 |
2021年 | 12537篇 |
2020年 | 9131篇 |
2019年 | 7325篇 |
2018年 | 7925篇 |
2017年 | 8979篇 |
2016年 | 8165篇 |
2015年 | 11518篇 |
2014年 | 14859篇 |
2013年 | 18870篇 |
2012年 | 20540篇 |
2011年 | 22071篇 |
2010年 | 19682篇 |
2009年 | 19291篇 |
2008年 | 19138篇 |
2007年 | 18789篇 |
2006年 | 17994篇 |
2005年 | 15588篇 |
2004年 | 10790篇 |
2003年 | 8441篇 |
2002年 | 7750篇 |
2001年 | 6948篇 |
2000年 | 6616篇 |
1999年 | 6262篇 |
1998年 | 5432篇 |
1997年 | 4474篇 |
1996年 | 4029篇 |
1995年 | 3378篇 |
1994年 | 2821篇 |
1993年 | 2238篇 |
1992年 | 1760篇 |
1991年 | 1308篇 |
1990年 | 1069篇 |
1989年 | 933篇 |
1988年 | 702篇 |
1987年 | 533篇 |
1986年 | 402篇 |
1985年 | 334篇 |
1984年 | 213篇 |
1983年 | 202篇 |
1982年 | 158篇 |
1981年 | 159篇 |
1980年 | 153篇 |
1979年 | 112篇 |
1978年 | 63篇 |
1977年 | 63篇 |
1976年 | 77篇 |
1975年 | 38篇 |
排序方式: 共有10000条查询结果,搜索用时 296 毫秒
81.
Wesley P. Chan Hiroto Mizohana Xiangyu Chen Yasuto Shiigi Yoshiyuki Yamanoue Masaki Nagatsuka Masayuki Inaba 《野外机器人技术杂志》2019,36(1):17-33
The use of field robots can greatly decrease the amount of time, effort, and associated risk compared to if human workers were to carryout certain tasks such as disaster response. However, transportability and reliability remain two main issues for most current robot systems. To address the issue of transportability, we have developed a lightweight modularizable platform named AeroArm. To address the issue of reliability, we utilize a multimodal sensing approach, combining the use of multiple sensors and sensor types, and the use of different detection algorithms, as well as active continuous closed‐loop feedback to accurately estimate the state of the robot with respect to the environment. We used Challenge 2 of the 2017 Mohammed Bin Zayed International Robotics Competition as an example outdoor manipulation task, demonstrating the capabilities of our robot system and approach in achieving reliable performance in the fields, and ranked fifth place internationally in the competition. 相似文献
82.
World Wide Web - The wide spread use of positioning and photographing devices gives rise to a deluge of traffic trajectory data (e.g., vehicle passage records and taxi trajectory data), with each... 相似文献
83.
84.
目的:探索炎性疾病患者的乳酸林格氏液(Ringer's lactate,RL)液体动力学特征以及炎性生物标记物是否可以作为协变量影响RL分布和排泄。方法:本研究为前瞻性队列研究。选择40例美国麻醉医师分级(ASA)I-II级,腹腔镜下择期胆囊切除术(胆囊炎组,n=20)或者腹腔镜下急诊阑尾切除术(阑尾炎组,n=20)。所有患者麻醉诱导前开始输注RL,按15 mL/kg,35 min内输毕。采用酶联免疫(enzyme-linked immunosorbent assay,ELISA)方法测定血浆炎症(TNF-α,IL-10和CRP)或者内皮损伤生物标记物(syndecan-1,SDC-1);利用血红蛋白(Hb)稀释-时间曲线和尿量,使用Phoenix软件,采用非线性混合效应模型分析计算RL液体动力学参数和协变量的影响。结果:与胆囊炎组相比,阑尾炎组RL从组织间隙到血浆的转运速率常数(k21)显著降低(14×10-3min-1 versus 35×10-3min-1;P=0.012)。阑尾炎组C反应蛋白(CRP)升高[中位数38.1(1.8-143.6) μg/mL versus 1.3(0.1-159.0) μg/mL;P<0.001];与清醒状态相比,麻醉期间(输液开始后30~45 min),液体从中央室中到外周室的转运速率常数(k12)显著增加(57×10-3min-1 versus 32×10-3min-1;P<0.01)。清除速率常数(k10)降低90%(0.6×10-3min-1 versus 5.3×10-3min-1;P<0.001)。无论在清醒状态还是麻醉状态下低血压均能降低液体清除;炎症或者内膜损伤的生物标记物不能作为显著影响RL液体动力学参数的协变量。结论:阑尾炎或者胆囊炎患者术前输入液体后“炎症反应的生物标记物”不是RL的液体动力学的协变量,但是两组患者中,全身麻醉期间输入液体的清除率下降。 相似文献
85.
86.
Jie-Long He An-Te Chen Jyong-Huei Lee Shih-Kang Fan 《International journal of molecular sciences》2015,16(9):22319-22332
The basic structural and functional unit of a living organism is a single cell. To understand the variability and to improve the biomedical requirement of a single cell, its analysis has become a key technique in biological and biomedical research. With a physical boundary of microchannels and microstructures, single cells are efficiently captured and analyzed, whereas electric forces sort and position single cells. Various microfluidic techniques have been exploited to manipulate single cells through hydrodynamic and electric forces. Digital microfluidics (DMF), the manipulation of individual droplets holding minute reagents and cells of interest by electric forces, has received more attention recently. Because of ease of fabrication, compactness and prospective automation, DMF has become a powerful approach for biological application. We review recent developments of various microfluidic chips for analysis of a single cell and for efficient genetic screening. In addition, perspectives to develop analysis of single cells based on DMF and emerging functionality with high throughput are discussed. 相似文献
87.
88.
A first‐principles‐based effective Hamiltonian is developed and employed to investigate finite‐temperature structural properties of a prototype of perovskite halides, that is CsPbI3. Such simulations, when using first‐principles‐extracted coefficients, successfully reproduce the existence of an orthorhombic Pnma state and its iodine octahedral tilting angles around room temperature. However, they also yield a direct transformation from Pnma to cubic upon heating, unlike measurements that reported the occurrence of an intermediate long‐range‐tilted tetragonal P4/mbm phase in‐between the orthorhombic and cubic phases. Such disagreement, which may cast some doubts about the extent to which first‐principle methods can be trusted to mimic hybrid perovskites, can be resolved by “only” changing one short‐range tilting parameter in the whole set of effective Hamiltonian coefficients. In such a case, some reasonable values of this specific parameter result in the predictions that i) the intermediate P4/mbm state originates from fluctuations over many different tilted states; and ii) the cubic phase is highly locally distorted and develops strong transverse antiphase correlation between first‐nearest neighbor iodine octahedral tiltings, before undergoing a phase transition to P4/mbm under cooling. 相似文献
89.
Lin Haicheng Huang Wantong Zhao Kun Qiao Shuang Liu Zheng Wu Jian Chen Xi Ji Shuai-Hua 《Nano Research》2020,13(1):133-137
Nano Research - The isostructural and isoelectronic transition-metal-dichalcogenides 1T-TaS2 and 1T-TaSe2 are layered materials with intricate electronic structures. Combining the molecular beam... 相似文献