全文获取类型
收费全文 | 102371篇 |
免费 | 12497篇 |
国内免费 | 5690篇 |
专业分类
电工技术 | 13997篇 |
技术理论 | 18篇 |
综合类 | 7794篇 |
化学工业 | 18165篇 |
金属工艺 | 3613篇 |
机械仪表 | 4369篇 |
建筑科学 | 12192篇 |
矿业工程 | 2328篇 |
能源动力 | 17021篇 |
轻工业 | 3144篇 |
水利工程 | 2033篇 |
石油天然气 | 3076篇 |
武器工业 | 818篇 |
无线电 | 7187篇 |
一般工业技术 | 11029篇 |
冶金工业 | 4467篇 |
原子能技术 | 1996篇 |
自动化技术 | 7311篇 |
出版年
2024年 | 548篇 |
2023年 | 2163篇 |
2022年 | 3503篇 |
2021年 | 3965篇 |
2020年 | 4104篇 |
2019年 | 3735篇 |
2018年 | 3206篇 |
2017年 | 3717篇 |
2016年 | 4135篇 |
2015年 | 4151篇 |
2014年 | 6706篇 |
2013年 | 6875篇 |
2012年 | 7178篇 |
2011年 | 8152篇 |
2010年 | 6207篇 |
2009年 | 6307篇 |
2008年 | 5801篇 |
2007年 | 6424篇 |
2006年 | 5341篇 |
2005年 | 4482篇 |
2004年 | 3673篇 |
2003年 | 3268篇 |
2002年 | 2818篇 |
2001年 | 2345篇 |
2000年 | 2036篇 |
1999年 | 1595篇 |
1998年 | 1379篇 |
1997年 | 1115篇 |
1996年 | 985篇 |
1995年 | 785篇 |
1994年 | 654篇 |
1993年 | 549篇 |
1992年 | 474篇 |
1991年 | 372篇 |
1990年 | 329篇 |
1989年 | 271篇 |
1988年 | 214篇 |
1987年 | 159篇 |
1986年 | 127篇 |
1985年 | 141篇 |
1984年 | 143篇 |
1983年 | 89篇 |
1982年 | 92篇 |
1981年 | 43篇 |
1980年 | 49篇 |
1979年 | 28篇 |
1978年 | 15篇 |
1977年 | 13篇 |
1959年 | 20篇 |
1951年 | 35篇 |
排序方式: 共有10000条查询结果,搜索用时 765 毫秒
61.
《Journal of the European Ceramic Society》2022,42(4):1568-1575
Li7La3Zr2O12-based garnet-type solid electrolytes are promising candidates for use in all-solid-state lithium batteries (ASSLBs). However, their potential in large-scale commercial applications is largely hindered by the time/energy-consuming and lithium-wasting synthetic method which typically needs a long-duration high temperature solid state reaction process. Herein we invent a fast preparation route that involves a short-period thermal reaction (1100 °C for 10 min) in laboratory muffle furnaces following by conventional hot pressing technique to get almost fully dense (Al, Ga, Ta, Nb)-doped garnet-type electrolytes with high phase purity (>99.9 %). The large and compact grains, low porosity and high phase purities of garnet ceramic electrolytes synthesized in this study ensure superior electrochemical performance. Particularly, Ga-doped cubic Li7La3Zr2O12 shows extremely low Ea values (0.17?0.18 eV) and record-high lithium ionic conductivities (>2 × 10?3 S cm-1 at 25 °C). 相似文献
62.
Yumio Yato 《Journal of Nuclear Science and Technology》2019,56(4):311-316
When UF6 is handled in leak tight system, the amount of uranium compound formed on the surface of containers, valves, and others in UF6 handling facilities is not so significant for a short term that special attention has not been given to this problem. The present work was done to throw some more light on this problem based on the recent experiment. We discuss the possibility that the intermolecular transfer of a fluorine atom from UF6 to UF5 may participate in the formation of uranium compound. The discussion includes also the unique features contained in the experimental result, the reaction processes assumed in this problem, and the derivation of a rate equation for expressing the deposition of uranium compound. Furthermore, we propose a new method for determining nonlinear parameters included in a governing differential equation having two variables for expressing the deposition of uranium compound from experimental raw data. 相似文献
63.
A microchannel heat exchanger with a triangular wave and symmetrical triangular wave structure was proposed in this paper. In addition, a new N-type microchannel heat exchanger was developed to balance the heat transfer performance and pressure drop. The relationship between different configurations of the N structure of the microchannel and the heat transfer performance was analyzed. The results showed that, at a high inlet flow rate, the symmetrical triangular wave microchannel had the best heat transfer performance, followed by the triangular wave microchannel and the straight channel. At the same flow rate, the degree of disturbance of the fluid was highest in the symmetrical N-structure microchannel, and an excellent heat transfer effect was observed. 相似文献
64.
ABSTRACT Design and implementation of an effective dissemination programme for decentralised renewable energy system necessitate an accurate estimate of its utilisation potential. Hence, in this study, an attempt has been made to develop frameworks to estimate the utilisation potential of decentralised renewable energy systems in the state of Uttarakhand in India. Estimations imply large resource, technical and economic potentials of the domestic solar water heater, solar home system, solar lantern, family size biogas plant and improved biomass cookstove in Uttarakhand. With higher impact on the purchasing power of households, prevailing soft loan scheme has been found to be more appropriate than a capital subsidy for promoting the usage of decentralised renewable energy systems. 相似文献
65.
Abdul Rahman Mohtasebzadeh Longfei Ye Thomas M. Crawford 《International journal of molecular sciences》2015,16(8):19769-19779
We study magnetic-field directed self-assembly of magnetic nanoparticles onto templates recorded on perpendicular magnetic recording media, and quantify feature width and height as a function of assembly time. Feature widths are determined from Scanning Electron Microscope (SEM) images, while heights are obtained with Atomic Force Microscopy (AFM). For short assembly times, widths were ~150 nm, while heights were ~14 nm, a single nanoparticle on average with a 10:1 aspect ratio. For long assembly times, widths approach 550 nm, while the average height grows to 3 nanoparticles, ~35 nm; a 16:1 aspect ratio. We perform magnetometry on these self-assembled structures and observe the slope of the magnetic moment vs. field curve increases with time. This increase suggests magnetic nanoparticle interactions evolve from nanoparticle–nanoparticle interactions to cluster–cluster interactions as opposed to feature–feature interactions. We suggest the aspect ratio increase occurs because the magnetic field gradients are strongest near the transitions between recorded regions in perpendicular media. If these gradients can be optimized for assembly, strong potential exists for using perpendicular recording templates to assemble complex heterogeneous materials. 相似文献
66.
《Current Opinion in Solid State & Materials Science》2020,24(1):100797
This paper reviews recent studies, that not only includes both experiments and modeling components, but celebrates a close coupling between these techniques, in order to provide insights into the plasticity and failure of polycrystalline metals. Examples are provided of studies across multiple-scales, including, but not limited to, density functional theory combined with atom probe tomography, molecular dynamics combined with in situ transmission electron miscopy, discrete dislocation dynamics combined with nanopillars experiments, crystal plasticity combined with digital image correlation, and crystal plasticity combined with in situ high energy X-ray diffraction. The close synergy between in situ experiments and modeling provides new opportunities for model calibration, verification, and validation, by providing direct means of comparison, thus removing aspects of epistemic uncertainty in the approach. Further, data fusion between in situ experimental and model-based data, along with data driven approaches, provides a paradigm shift for determining the emergent behavior of deformation and failure, which is the foundation that underpins the mechanical behavior of polycrystalline materials. 相似文献
67.
In this present work, Ca-alginate-biochar adsorbent has been synthesized, characterized and tested its effectiveness in the removal of aqueous phase Zn2+ metal. The removal efficiency was studied under various physicochemical process parameters. External mass transfer model, intraparticle diffusion model and pseudo-first-order and pseudo-second-order models were used to fit the experimental Zn2+ adoption kinetic results and to identify the mechanism of adsorption. The desorption studies indicate the possibilities of ion-exchange and physical–chemical adsorption of Zn2+. The adsorption was best described by Langmuir isotherm model. Thermodynamic parameters suggested that the adsorption process becomes spontaneous, endothermic and irreversible in nature. 相似文献
68.
《The Electricity Journal》2020,33(7):106816
Using mean value theorem for integrals we show that the well-known LCOE definition is incorrect. 相似文献
69.
Automatic load shedding is the ultimate countermeasure against imbalance in a power system and can effectively help preventing large blackouts. Taking into account a high penetration of renewable energy sources (RES) in the distribution grid, a clear distinction between load and generation at the PCC becomes increasingly more difficult. For that reason an adaptation of frequency relay parameters and their locations of installation are necessary. In Europe this is rest on a multi-step plan based on values such as the yearly peak load. In this paper a novel probabilistic method for automatic load shedding is presented that uses the average values instead of peak values for load shedding. Its applicability is verified by a dynamic power system model that was developed to compare the classical and novel probabilistic load shedding principle. The method is verified using data from a German TSO. 相似文献
70.
Light-emitting field effect transistors (LEFETs) are a class of organic optoelectronic device capable of simultaneously delivering the electrical switching characteristics of a transistor and the light emission of a diode. We report on the temperature dependence of the charge transport and emissive properties in a model organic heterostructure LEFET system from 300 K to 135 K. We study parameters such as carrier mobility, brightness, and external quantum efficiency (EQE), and observe clear thermally activated behaviour for transport and injection. Overall, the EQE increases with decreasing temperature and conversely the brightness decreases. These contrary effects can be explained by a higher recombination efficiency occurring at lower temperatures, and this insight delivers new knowledge concerning the optimisation of both the transport and emissive properties in LEFETs. 相似文献