全文获取类型
收费全文 | 52821篇 |
免费 | 2827篇 |
国内免费 | 66篇 |
专业分类
电工技术 | 509篇 |
综合类 | 34篇 |
化学工业 | 10073篇 |
金属工艺 | 1104篇 |
机械仪表 | 1154篇 |
建筑科学 | 1758篇 |
矿业工程 | 135篇 |
能源动力 | 1016篇 |
轻工业 | 7851篇 |
水利工程 | 467篇 |
石油天然气 | 186篇 |
武器工业 | 5篇 |
无线电 | 3062篇 |
一般工业技术 | 8858篇 |
冶金工业 | 11669篇 |
原子能技术 | 365篇 |
自动化技术 | 7468篇 |
出版年
2023年 | 397篇 |
2022年 | 410篇 |
2021年 | 1174篇 |
2020年 | 947篇 |
2019年 | 1100篇 |
2018年 | 1796篇 |
2017年 | 1759篇 |
2016年 | 1910篇 |
2015年 | 1369篇 |
2014年 | 1854篇 |
2013年 | 3755篇 |
2012年 | 2751篇 |
2011年 | 2792篇 |
2010年 | 2247篇 |
2009年 | 2078篇 |
2008年 | 2077篇 |
2007年 | 1946篇 |
2006年 | 1446篇 |
2005年 | 1258篇 |
2004年 | 1140篇 |
2003年 | 1028篇 |
2002年 | 1000篇 |
2001年 | 795篇 |
2000年 | 780篇 |
1999年 | 847篇 |
1998年 | 3506篇 |
1997年 | 2374篇 |
1996年 | 1603篇 |
1995年 | 1040篇 |
1994年 | 829篇 |
1993年 | 923篇 |
1992年 | 421篇 |
1991年 | 389篇 |
1990年 | 341篇 |
1989年 | 351篇 |
1988年 | 322篇 |
1987年 | 286篇 |
1986年 | 279篇 |
1985年 | 357篇 |
1984年 | 289篇 |
1983年 | 239篇 |
1982年 | 250篇 |
1981年 | 282篇 |
1980年 | 283篇 |
1979年 | 211篇 |
1978年 | 149篇 |
1977年 | 423篇 |
1976年 | 831篇 |
1975年 | 140篇 |
1973年 | 163篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
52.
Machine Learning - We propose a data-driven approach to quantify the uncertainty of models constructed by kernel methods. Our approach minimizes the needed distributional assumptions, hence,... 相似文献
53.
54.
Miroslav Kárný Marko Ruman 《International Journal of Adaptive Control and Signal Processing》2021,35(5):660-675
Any knowledge extraction relies (possibly implicitly) on a hypothesis about the modelled-data dependence. The extracted knowledge ultimately serves to a decision-making (DM). DM always faces uncertainty and this makes probabilistic modelling adequate. The inspected black-box modeling deals with “universal” approximators of the relevant probabilistic model. Finite mixtures with components in the exponential family are often exploited. Their attractiveness stems from their flexibility, the cluster interpretability of components and the existence of algorithms for processing high-dimensional data streams. They are even used in dynamic cases with mutually dependent data records while regression and auto-regression mixture components serve to the dependence modeling. These dynamic models, however, mostly assume data-independent component weights, that is, memoryless transitions between dynamic mixture components. Such mixtures are not universal approximators of dynamic probabilistic models. Formally, this follows from the fact that the set of finite probabilistic mixtures is not closed with respect to the conditioning, which is the key estimation and predictive operation. The paper overcomes this drawback by using ratios of finite mixtures as universally approximating dynamic parametric models. The paper motivates them, elaborates their approximate Bayesian recursive estimation and reveals their application potential. 相似文献
55.
Anh Tuan Thanh Pham Oanh Kieu Truong Le Dung Van Hoang Truong Huu Nguyen Trang Huyen Cao Pham Phuong Thanh Ngoc Vo Thang Bach Phan Vinh Cao Tran 《Journal of the European Ceramic Society》2021,41(6):3493-3500
Structure modification has been found to tune significantly the transparent-conducting performance, especially mobility and conductivity of hydrogenated Ga-doped ZnO (HGZO) films. The strong correlation between film thickness and mobility of the films is revealed. The mobility increases quickly with increasing the thickness from 350 to 900 nm, and then tends to be saturated at further thicknesses. A higher mobility than 50 cm2/Vs can be achieved, which is an extra-high value for polycrystalline ZnO films deposited by using the sputtering technique. The thickness-dependent mobility originates from scatterings on grain boundaries and dislocation-induced defects controlled by thin-film growth. Based on the Volmer-Weber model, an expansion model is built up to describe the thickness-dependent crystal growth of the HGZO films, especially at the thick films. As a result, the 800 nm-thick HGZO film obtains the highest performance with high mobility of 51.5 cm2/Vs, low resistivity of 5.3 × 10?4 Ωcm, and good transmittance of 83.3 %. 相似文献
56.
Lorena Rodríguez-López Myriam Rincón-Fontán Xanel Vecino Ana B. Moldes Jose M. Cruz 《Journal of surfactants and detergents》2020,23(1):79-90
Over the last few years, the global biosurfactant market has raised due to the increasing awareness among consumers, for the use of biological or bio-based products. Because of their composition, it can be speculated that these are more biocompatible and more biodegradable than their chemical homologous. However, at the moment, no studies exist in the literature about the biodegradability of biosurfactants. In this work, a biosurfactant contained in a crude extract, obtained from a corn wet-milling industry stream that ferments spontaneously in the presence of lactic acid bacteria, was subjected to a biodegradation study, without addition of external microbial biomass, under different conditions of temperature (5–45 °C), biodegradation time (15–55 days), and pH (5–7). For that, a Box–Behnken factorial design was applied, which allowed to predict the percentage of biodegradation for the biosurfactant contained in the crude extract, between the range of the independent variables selected in the study, obtaining biodegradation values between 3 and 80%. The percentage of biodegradation for the biosurfactant was calculated based on the increase in the surface tension of samples of the crude extract. Furthermore, it was also possible to predict the variation in t1/2 for the biosurfactant (time to achieve the 50% of biodegradation) under different conditions. 相似文献
57.
Bican Osman Bayça Salih Uğur Kuleyin Hamdi Gümrük Recep 《Metal Science and Heat Treatment》2021,63(3-4):156-162
Metal Science and Heat Treatment - The effect of solid boronizing at 950°C for 2 and 4 h on the phase composition, microstructure, hardness and abrasive wear of steel AISI 304L is studied... 相似文献
58.
59.
Martin Michálek Monika Michálková Gurdial Blugan Jakob Kuebler 《Ceramics International》2018,44(3):3255-3260
Up to now, commercially available alumina ceramics were claimed to have strength between 400 and 550 MPa. However, our study shows strength ~ 2 times higher for commercially available alumina than commonly believed. The average and characteristic strength, measured on 31 pure alumina ceramic discs by ball on three balls (B3B) test, were 1205 ± 93 MPa and 1257 MPa, respectively, with a Weibull modulus of m = 11.8. Tested specimens were in form of discs with a diameter of 5 mm and thickness 0.5 mm. The grain size distribution of the alumina is bimodal with an average grain size of ~ 850 nm measured at the surface. The fracture reveals a mixed transgranular / intergranular failure mode. To avoid incorporation of additional flaws, the discs were tested as sintered. The characteristic flexural strength measured in B3B was recalculated according to Weibull theory for standard 4-point bending bars of size 3 × 4 × 45 mm as bend 856 MPa. The measured strength of nearly 900 MPa shows the potential of strength for high purity alumina ceramics. 相似文献
60.