全文获取类型
收费全文 | 99397篇 |
免费 | 9721篇 |
国内免费 | 5712篇 |
专业分类
电工技术 | 7967篇 |
技术理论 | 7篇 |
综合类 | 7680篇 |
化学工业 | 13953篇 |
金属工艺 | 6191篇 |
机械仪表 | 6608篇 |
建筑科学 | 8617篇 |
矿业工程 | 2942篇 |
能源动力 | 3022篇 |
轻工业 | 5990篇 |
水利工程 | 2145篇 |
石油天然气 | 5132篇 |
武器工业 | 1044篇 |
无线电 | 11860篇 |
一般工业技术 | 10996篇 |
冶金工业 | 4384篇 |
原子能技术 | 1268篇 |
自动化技术 | 15024篇 |
出版年
2024年 | 446篇 |
2023年 | 1544篇 |
2022年 | 2784篇 |
2021年 | 4057篇 |
2020年 | 2945篇 |
2019年 | 2344篇 |
2018年 | 2745篇 |
2017年 | 3093篇 |
2016年 | 2744篇 |
2015年 | 3998篇 |
2014年 | 5116篇 |
2013年 | 6092篇 |
2012年 | 6987篇 |
2011年 | 7399篇 |
2010年 | 6775篇 |
2009年 | 6344篇 |
2008年 | 6576篇 |
2007年 | 6363篇 |
2006年 | 6086篇 |
2005年 | 5189篇 |
2004年 | 3754篇 |
2003年 | 3089篇 |
2002年 | 3053篇 |
2001年 | 2657篇 |
2000年 | 2269篇 |
1999年 | 2121篇 |
1998年 | 1483篇 |
1997年 | 1272篇 |
1996年 | 1230篇 |
1995年 | 955篇 |
1994年 | 799篇 |
1993年 | 566篇 |
1992年 | 514篇 |
1991年 | 363篇 |
1990年 | 256篇 |
1989年 | 221篇 |
1988年 | 176篇 |
1987年 | 114篇 |
1986年 | 74篇 |
1985年 | 60篇 |
1984年 | 39篇 |
1983年 | 27篇 |
1982年 | 35篇 |
1981年 | 20篇 |
1980年 | 26篇 |
1979年 | 14篇 |
1978年 | 2篇 |
1959年 | 4篇 |
1951年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
41.
Journal of Porous Materials - In this work, a trifluoromethanesulfonic acid (TFOH) modified clay (TFOH-Clay) was developed for the removal of trace olefins in heavy naphtha. 5%TFOH-Clay can... 相似文献
42.
Gang Zheng Xiaoxuan Yu Haizuo Zhou Xinyu Yang Wei Guo Pengbo Yang 《Geotextiles and Geomembranes》2021,49(1):180-187
Incompressible dipping substrata are commonly encountered in engineering practice. Compared to horizontal underlying strata, the inclined underlying stratum increase the risk of collapse of embankments reinforced with columns because it weakens the restraint of the column base. The objective of this study is to investigate the effectiveness of geosynthetics on improving the embankment stability when the underlying stratum is inclined. The influence of geosynthetic tensile stiffness on the ultimate surcharge and failure mechanism is studied. A deep-seated failure with column tilting occurs when the geosynthetic tensile stiffness is low, whereas a lateral sliding occurs when the geosynthetic tensile stiffness is high. To illustrate the contribution of geosynthetics, the distribution of the lateral pressures acting on the columns is analyzed. 相似文献
43.
Crystallographic characteristics and microwave dielectric properties of Ni-modified MgTa2O6 ceramics
Liang Shi Xueying Wang Rui Peng Gang Wang Cheng Liu Xiaolei Shi Dainan Zhang Huaiwu Zhang 《Ceramics International》2021,47(16):22514-22521
Ni2+ modified MgTa2O6 ceramics with a trirutile phase and space group P42/mnm were obtained. The correlations between crystallographic characteristics and microwave dielectric performance of MgTa2O6 ceramics were systematically studied based on the chemistry bond theory (PVL theory) for the first time. The results indicate that the introduction of Ni2+ causes a change in polarizability and the Mg–O bond ionicity, which contributes to the variation of dielectric constant. Moreover, the lattice energy, and packing fraction, full width at half maximum of the Raman peak of Ta–O bond, as the quantitative characterization of crystallographic parameters, regulate the dielectric loss of MgTa2O6 ceramics in GHz frequency band. In addition, the study of sintering behavior shows that the densification and micromorphology are the crucial factors affecting the microwave dielectric performance. Typically, Ni2+ doping on the A-site of MgTa2O6 can effectively promote the Q × f values to 173,000 GHz (at 7.43 GHz), which ensures its applicability in 5G communication technology. 相似文献
44.
Multibody System Dynamics - This paper represents an explicit analytical solution for attitude dynamics of spacecraft combination during on-orbit refueling. Due to the fuel transfer from the... 相似文献
45.
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
46.
Rachana R. Borkute Sren Woelke Gang Pei Anca Dorhoi 《International journal of molecular sciences》2021,22(9)
Neutrophils readily infiltrate infection foci, phagocytose and usually destroy microbes. In tuberculosis (TB), a chronic pulmonary infection caused by Mycobacterium tuberculosis (Mtb), neutrophils harbor bacilli, are abundant in tissue lesions, and their abundances in blood correlate with poor disease outcomes in patients. The biology of these innate immune cells in TB is complex. Neutrophils have been assigned host-beneficial as well as deleterious roles. The short lifespan of neutrophils purified from blood poses challenges to cell biology studies, leaving intracellular biological processes and the precise consequences of Mtb–neutrophil interactions ill-defined. The phenotypic heterogeneity of neutrophils, and their propensity to engage in cellular cross-talk and to exert various functions during homeostasis and disease, have recently been reported, and such observations are newly emerging in TB. Here, we review the interactions of neutrophils with Mtb, including subcellular events and cell fate upon infection, and summarize the cross-talks between neutrophils and lung-residing and -recruited cells. We highlight the roles of neutrophils in TB pathophysiology, discussing recent findings from distinct models of pulmonary TB, and emphasize technical advances that could facilitate the discovery of novel neutrophil-related disease mechanisms and enrich our knowledge of TB pathogenesis. 相似文献
47.
In this paper, we first re-examine the previous protocol of controlled quantum secure direct communication of Zhang et al.’s scheme, which was found insecure under two kinds of attacks, fake entangled particles attack and disentanglement attack. Then, by changing the party of the preparation of cluster states and using unitary operations, we present an improved protocol which can avoid these two kinds of attacks. Moreover, the protocol is proposed using the three-qubit partially entangled set of states. It is more efficient by only using three particles rather than four or even more to transmit one bit secret information. Given our using state is much easier to prepare for multiqubit states and our protocol needs less measurement resource, it makes this protocol more convenient from an applied point of view. 相似文献
48.
Basins with various mineral resources coexisting and enriching often occupy an important strategic position. The exploration of various mineral resources is repetitive at present due to unshared data and imperfect management mechanism. This situation greatly increases the cost of energy exploitation in the country. Traditional data-sharing mode has several disadvantages, such as high cost, difficulty in confirming the right of data, and lack of incentive mechanism, which make achieving real data sharing difficult. In this paper, we propose a data-sharing mechanism based on blockchain and provide implementation suggestions and technical key points. Compared with traditional data-sharing methods, the proposed data-sharing mechanism can realize data sharing, ensure data quality, and protect intellectual property. Moreover, key points in the construction are stated in the case study section to verify the feasibility of the data-sharing system based on blockchain proposed in this paper. 相似文献
49.
Shensong Wang Zheng Wu Jie Chen Jiangping Ma Jingshi Ying Shouchen Cui Shigang Yu Yongming Hu Jinhe Zhao Yanmin Jia 《Ceramics International》2019,45(9):11703-11708
In this work, the hydrothermally-synthesized sodium niobate nanowires were used to decompose Rhodamine B dye solution through the piezo-catalytic effect. With the sodium niobate catalyst, a high piezo-catalytic degradation ratio of ~80% was achieved under the excitation of vibration for the Rhodamine B dye solution (~5?mg/l). These active species in the catalytic process, hydroxyl radicals and superoxide radicals with the strong oxidation ability, were also observed, which confirmed the key role of piezoelectric effect for piezo-catalysis. The piezo-catalysis of sodium niobate nanowires provides a high-efficiency and reusable tool in application in depredating the dye wastewater. 相似文献
50.
Bin Zhang Meng Zhang Yu Li Huansheng Cheng Jianming Zheng 《Ceramics International》2019,45(3):3081-3087
Proton induced X-ray emission (PIXE) technique and factor analysis were used to study the recovery of making-technology of Chinese Longquan celadon made in the late Southern Song Dynasty (1127–1279 CE). Based on factor analysis, for the raw material for body and the recipe for glaze, there is a close but slightly different relationship between these Longquan celadons unearthed from the core area of Dayao and the non-core area, despite all the Longquan celadons belong to the high-calcium-glaze system. The chemical compositions of most of the tentative body and glaze samples are very close to those of Longquan celadons unearthed from the core area of Dayao and the non-core area. This study can provide a guidance for recovery of making-technology of Longquan celandon. 相似文献