全文获取类型
收费全文 | 77559篇 |
免费 | 9329篇 |
国内免费 | 6576篇 |
专业分类
电工技术 | 7140篇 |
技术理论 | 1篇 |
综合类 | 8664篇 |
化学工业 | 9586篇 |
金属工艺 | 5404篇 |
机械仪表 | 6012篇 |
建筑科学 | 6095篇 |
矿业工程 | 3559篇 |
能源动力 | 2077篇 |
轻工业 | 8832篇 |
水利工程 | 2544篇 |
石油天然气 | 2760篇 |
武器工业 | 1357篇 |
无线电 | 8089篇 |
一般工业技术 | 6215篇 |
冶金工业 | 2960篇 |
原子能技术 | 1224篇 |
自动化技术 | 10945篇 |
出版年
2024年 | 418篇 |
2023年 | 1391篇 |
2022年 | 3383篇 |
2021年 | 4418篇 |
2020年 | 3013篇 |
2019年 | 1981篇 |
2018年 | 2148篇 |
2017年 | 2482篇 |
2016年 | 2182篇 |
2015年 | 3611篇 |
2014年 | 4438篇 |
2013年 | 5190篇 |
2012年 | 6676篇 |
2011年 | 6829篇 |
2010年 | 6437篇 |
2009年 | 6081篇 |
2008年 | 6238篇 |
2007年 | 6089篇 |
2006年 | 5213篇 |
2005年 | 4147篇 |
2004年 | 2960篇 |
2003年 | 1952篇 |
2002年 | 1853篇 |
2001年 | 1654篇 |
2000年 | 1405篇 |
1999年 | 514篇 |
1998年 | 127篇 |
1997年 | 105篇 |
1996年 | 81篇 |
1995年 | 55篇 |
1994年 | 44篇 |
1993年 | 50篇 |
1992年 | 38篇 |
1991年 | 28篇 |
1990年 | 33篇 |
1989年 | 42篇 |
1988年 | 16篇 |
1987年 | 14篇 |
1986年 | 12篇 |
1985年 | 11篇 |
1984年 | 15篇 |
1983年 | 8篇 |
1982年 | 9篇 |
1981年 | 10篇 |
1980年 | 20篇 |
1979年 | 14篇 |
1959年 | 14篇 |
1951年 | 15篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
22.
23.
24.
江河湖海疏浚工程对于拓展和保障航运安全、促进生态恢复、维护/改善远海岛礁环境具有不可或缺的作用.目前,在绞吸和耙吸疏浚船上,多采用射线密度计及电磁流量计对输泥密度、产量等进行在线计量,并作为实现疏浚系统自动控制的重要参量.由于射线密度计潜在的人员健康、公共安全和环保风险,在一些国家和地区已建立了放射源的有序退出机制.电阻层析成像使用安装于管壁的电极阵列获得管道内流体的电导率分布,进而推导出管道内的泥浆密度,具有无辐射、全场测量及实时可视化的优点.电阻层析成像测量系统经过特殊设计,可适应从内陆淡水到海水的巨大电导率变化.初步测试表明,电阻层析成像测量数据与射线密度计具有良好一致性,具备了作为在线泥浆密度测量的可行性.此外,ERT可提供实时的流动成像,对于提高对疏浚管道监测能力和降低堵管概率具有重要意义. 相似文献
25.
26.
针对基于容积脉搏波(PPG)提取运动心率时,传统心率提取算法由于运动噪声干扰使测量结果误差大、实时性不好的问题,提出一种抗运动干扰的实时心率提取方法。该方法通过实时小波去噪,同时结合三轴加速度信号(ACC)对运动进行分类训练,计算各运动状态心率增益,对实时心率值进行补偿。实验结果表明,通过与同时采集的ECG信号计算出的实时心率进行对比,绝对误差率仅为1.2%左右。相比传统心率提取算法,该算法具有抗干扰性强,实时准确的特点。 相似文献
27.
Weigang Liang Beibei Wang Guofeng Shen Suzhen Cao Bertrand Mcswain Ning Qin Liyun Zhao Dongmei Yu Jicheng Gong Shanshan Zhao Yawei Zhang Xiaoli Duan 《Indoor air》2020,30(2):264-274
Stunting adversely affects physical and mental outcomes of children. It has not been examined whether household air pollution from solid fuel combustion is a risk factor for stunting in children. In a total of 41,439 children aged 6-17 across China, height was measured using a unified protocol. Multivariable linear regression models and logistic regression models were used to assess the associations of solid fuel use for cooking/heating with stunting in children. Adjusted for covariates, cooking/heating with solid fuel was significantly associated with a lower z-score for height for age and sex (β = −0.21 [−0.32 to −0.09] and −0.17 [−0.31 to −0.03], respectively) and an increased risk of stunting with an estimated ORs of 1.34 [1.07~1.68] and 1.37 [1.02~1.83], respectively. The risk of stunting associated with solid fuel use was statistically significant in high-age children. And the effect was greater on girls than on boys, though the difference was not statistically significant. Our study suggested that Chinese children living in households using solid fuel had a significantly higher risk of stunting than those living in households using cleaner fuel. 相似文献
28.
Global decrease in crude oil resources and frequent crude oil leaks cause the energy crisis and ecological pollution. The absorption and release of leaked crude oil through absorption materials are a necessary process for environmental protection and recycling. In this article, a CO2-responsive olefin copolymer was obtained by copolymerization of styrene and an amine-containing olefin monomer. The structure of resultant copolymer was characterized by FTIR; thermal properties and CO2-responsive morphology changes were determined by DSC/TGA and SEM, respectively. Copolymers had certain absorption capacity for toluene with absorption rate up to 180.0%. The absorbed toluene could be released upon CO2 stimulation with desorption rate up to 84.6%. The CO2-responsive copolymer could be regenerated through a simple heating process and showed stable absorption–desorption performance even after being recycled for 4 times. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47439. 相似文献
29.
Dr. Yahu A. Liu Dr. Qihui Jin Qiang Ding Dr. Xueshi Hao Tingting Mo Shanshan Yan Dr. Yefen Zou Dr. Zhihong Huang Xiaoyue Zhang Wenqi Gao Dr. Tom Y.-H. Wu Chun Li Dr. Badry Bursalaya Dr. Michael Di Donato Dr. You-Qing Zhang Lisa Deaton Dr. Weijun Shen Dr. Brandon Taylor Anwesh Kamireddy Dr. George Harb Dr. Jing Li Dr. Yong Jia Dr. Andrew M. Schumacher Dr. Bryan Laffitte Dr. Richard Glynne Dr. Shifeng Pan Dr. Peter McNamara Dr. Valentina Molteni Dr. Jon Loren 《ChemMedChem》2020,15(16):1562-1570
Loss of β-cell mass and function can lead to insufficient insulin levels and ultimately to hyperglycemia and diabetes mellitus. The mainstream treatment approach involves regulation of insulin levels; however, approaches intended to increase β-cell mass are less developed. Promoting β-cell proliferation with low-molecular-weight inhibitors of dual-specificity tyrosine-regulated kinase 1A (DYRK1A) offers the potential to treat diabetes with oral therapies by restoring β-cell mass, insulin content and glycemic control. GNF4877, a potent dual inhibitor of DYRK1A and glycogen synthase kinase 3β (GSK3β) was previously reported to induce primary human β-cell proliferation in vitro and in vivo. Herein, we describe the lead optimization that lead to the identification of GNF4877 from an aminopyrazine hit identified in a phenotypic high-throughput screening campaign measuring β-cell proliferation. 相似文献
30.
We propose an analytical model to evaluate the lightpath blocking performance for a single ROADM node with intra-node add/drop contention,in which the number of lightpaths that can be added/dropped with the same wavelength is limited by the add/drop contention factor.Different models of traffic load per nodal degree are considered to validate the effectiveness of the analytical model.The simulation results show that the proposed analytical model is effective in predicting the performance for different values of add/drop contention factor C and for variable offered loads at the node.The add/drop contention factor shows an important impact on the lightpath blocking performance and properly raising the contention factor can significantly improve the lightpath blocking performance.When the add/drop contention factor C exceeds a certain level,the performance of a ROADM with intra-node contention is close to that of a contentionless ROADM. 相似文献