全文获取类型
收费全文 | 37410篇 |
免费 | 4364篇 |
国内免费 | 2294篇 |
专业分类
电工技术 | 8084篇 |
技术理论 | 1篇 |
综合类 | 4150篇 |
化学工业 | 682篇 |
金属工艺 | 1101篇 |
机械仪表 | 3433篇 |
建筑科学 | 1340篇 |
矿业工程 | 918篇 |
能源动力 | 437篇 |
轻工业 | 679篇 |
水利工程 | 714篇 |
石油天然气 | 527篇 |
武器工业 | 482篇 |
无线电 | 9744篇 |
一般工业技术 | 2088篇 |
冶金工业 | 612篇 |
原子能技术 | 274篇 |
自动化技术 | 8802篇 |
出版年
2024年 | 139篇 |
2023年 | 496篇 |
2022年 | 738篇 |
2021年 | 905篇 |
2020年 | 885篇 |
2019年 | 625篇 |
2018年 | 645篇 |
2017年 | 970篇 |
2016年 | 1142篇 |
2015年 | 1487篇 |
2014年 | 2300篇 |
2013年 | 2040篇 |
2012年 | 2872篇 |
2011年 | 3212篇 |
2010年 | 2526篇 |
2009年 | 2656篇 |
2008年 | 2685篇 |
2007年 | 3253篇 |
2006年 | 2874篇 |
2005年 | 2440篇 |
2004年 | 1834篇 |
2003年 | 1587篇 |
2002年 | 1204篇 |
2001年 | 991篇 |
2000年 | 776篇 |
1999年 | 583篇 |
1998年 | 383篇 |
1997年 | 320篇 |
1996年 | 293篇 |
1995年 | 267篇 |
1994年 | 209篇 |
1993年 | 155篇 |
1992年 | 105篇 |
1991年 | 93篇 |
1990年 | 77篇 |
1989年 | 62篇 |
1988年 | 54篇 |
1987年 | 26篇 |
1986年 | 24篇 |
1985年 | 25篇 |
1984年 | 27篇 |
1983年 | 16篇 |
1982年 | 19篇 |
1981年 | 9篇 |
1980年 | 11篇 |
1979年 | 10篇 |
1978年 | 5篇 |
1977年 | 3篇 |
1959年 | 4篇 |
1955年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
基于电信运营商数字化转型,系统性地提出了数据驱动的云网发展规划体系,以及六大关键数字化能力构建,设计和实现了一种云网规划数字化平台,该平台可用于实现目标网络精细规划、边缘计算精准预测等场景,并探讨了数字孪生在规划领域的应用前景,对运营商推进云网融合战略、推进高质量发展具有指导和参考意义。 相似文献
3.
《Ceramics International》2022,48(14):20000-20009
Zinc oxide (ZnO) offers a major disadvantage of asymmetry doping in terms of reliability, stability, and reproducibility of p-type doping, which is the main hindrance in realization of optoelectronic devices. The problem is even more complicated due to formation of various native defects in unintentionally doped n-type ZnO. The realization of p-type conductivity in doped ZnO requires an in-depth understanding of the formation of an effective shallow acceptor, as well as donor-acceptor compensation. Photophysical properties such as photoconductivity along with photoluminescence (PL) studies have unprecedentedly and effectively been utilized in this work to monitor the evolution of various in-gap defects. Phosphorus (P) doped ZnO thin films have been grown by RF magnetron sputtering under various Ar to O2 gas ratios to investigate the effect of O2 on the donor-acceptor compensation by comprehensive photoconductivity measurements supported by the PL studies. Initial elemental analyses indicate presence of abundant zinc vacancies (VZn) in O-rich ambience. The results predict that P sits in the zinc (Zn) site rather than the oxygen (O) site causing the formation of PZn–2VZn acceptor-like defects, which compensates the donor defects in P doped ZnO films. Photocurrent spectra uniquely reveal presence of more oxygen vacancies (VO) defects states in lower O2 flow, which gets compensated with an increase in the O2 flow. Successive photocurrent transients indicate probable presence of more VO in the films grown with lower O2 flow and more VZn in higher O2 flow. Overall the photosensitivity measurements clearly present that O-rich ambience expedites the formation of acceptor defects which are compensated, thereby lowering the dark current and enhancing the ultraviolet photosensitivity. 相似文献
4.
In the past, thinking of carrying electronic devices inside our bodies was only posed by non-real scenarios. The emergence of insertable devices has changed this. Since this technology is still in its initial development stages, few studies have investigated factors that influence its acceptance. This paper analyzes the predictors of the intention to use non-medical insertable devices in two Latin American contexts. We used partial least squares structural equation modeling to examine whether six constructs predicted intention to use insertable devices. A questionnaire was administered to undergraduate students located in Colombia and Chile (n = 672). We also examined whether these predictors influenced intention differently for both of them. Four common constructs significantly and positively influenced both Chilean and Colombian respondents to use insertable devices (hedonic motivation, habit, performance expectancy, and social influence). Also, the habit has a complementary mediating effect on the relationship between social influence and behavioral intention. By contrast, effort expectations were a positive and significant predictor, but only among Chilean respondents. Findings suggest that when technologies are emerging, well-known predictors of intention (e.g., performance and effort expectations) are less influential than predictors related to self-efficacy (e.g., habit and hedonic motivation). The use of insertable devices has a significant impact on society. Thus, a better understanding of what motivates their use has implications for both academia and industry. 相似文献
5.
为推进病历数字化发展,并确保其信息的安全性,将以HIS电子病历系统为基础,采用安信数字签名技术和PKI或PMI系统搭建相信并加以任用的授权服务,经过针对实际的PKC和CA的确认、委托与管控构建整体的数字签名平台,完成电子病历数字签名功能设计,以加强电子文件的完整性、真实性和不可抵赖性。最后以某医院的XML结构化的电子病历系统为基础进行项目实施,完成了医护人员通过HIS的快速身份认证,和准确地数字签名。 相似文献
6.
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
7.
In this paper, a new inverse identification method of constitutive parameters is developed from full kinematic and thermal field measurements. It consists in reconstructing the heat source field from two different approaches by using the heat diffusion equation. The first one requires the temperature field measurement and the value of the thermophysical parameters. The second one is based on the kinematic field measurement and the choice of a thermo-hyperelastic model that contains the parameters to be identified. The identification is carried out at the local scale, ie, at any point of the heat source field, without using the boundary conditions. In the present work, the method is applied to the challenging case of hyperelasticity from a heterogeneous test. Due to large deformations undergone by the rubber specimen tested, a motion compensation technique is developed to plot the kinematic and the thermal fields at the same points before reconstructing the heterogeneous heat source field. In the present case, the constitutive parameter of the Neo-Hookean model has been identified, and its distribution has been characterized with respect to the strain state at the surface of a cross-shaped specimen. 相似文献
8.
现今国内的数字集群网络发展存在局限性、差异性,还远没有达到“网”状分布的程度,因此,共网数字集群发展空间巨大、前景广阔。通过列举共网数字集群系统在龙嘉国际机场和长春雷锋车队的成功应用案例,探讨了我国共网数字集群系统应用的可行性和必要性。 相似文献
9.
The load applied to a machine tool feed drive changes during the machining process as material is removed. This load change alters the Coulomb friction of the feed drive. Because Coulomb friction accounts for a large part of the total friction the friction compensation control accuracy of the feed drives is limited if this nonlinear change in the applied load is not considered. This paper presents a new friction compensation method that estimates the machine tool load in real time and considers its effect on friction characteristics. A friction observer based on a Kalman filter with load estimation is proposed for friction compensation control considering the applied load change. A specially designed feed drive testbed that enables the applied load to be modified easily was constructed for experimental verification. Control performance and friction estimation accuracy are demonstrated experimentally using the testbed. 相似文献
10.