全文获取类型
收费全文 | 44484篇 |
免费 | 6039篇 |
国内免费 | 3297篇 |
专业分类
电工技术 | 4383篇 |
技术理论 | 1篇 |
综合类 | 3846篇 |
化学工业 | 10834篇 |
金属工艺 | 4536篇 |
机械仪表 | 1733篇 |
建筑科学 | 1383篇 |
矿业工程 | 809篇 |
能源动力 | 1752篇 |
轻工业 | 2472篇 |
水利工程 | 587篇 |
石油天然气 | 2085篇 |
武器工业 | 411篇 |
无线电 | 6737篇 |
一般工业技术 | 5967篇 |
冶金工业 | 2590篇 |
原子能技术 | 552篇 |
自动化技术 | 3142篇 |
出版年
2024年 | 233篇 |
2023年 | 843篇 |
2022年 | 1237篇 |
2021年 | 1507篇 |
2020年 | 1654篇 |
2019年 | 1592篇 |
2018年 | 1469篇 |
2017年 | 1710篇 |
2016年 | 1789篇 |
2015年 | 1764篇 |
2014年 | 2417篇 |
2013年 | 2716篇 |
2012年 | 3009篇 |
2011年 | 2992篇 |
2010年 | 2189篇 |
2009年 | 2440篇 |
2008年 | 2295篇 |
2007年 | 2809篇 |
2006年 | 2627篇 |
2005年 | 2168篇 |
2004年 | 1823篇 |
2003年 | 1768篇 |
2002年 | 1539篇 |
2001年 | 1395篇 |
2000年 | 1232篇 |
1999年 | 1012篇 |
1998年 | 900篇 |
1997年 | 825篇 |
1996年 | 640篇 |
1995年 | 623篇 |
1994年 | 532篇 |
1993年 | 369篇 |
1992年 | 384篇 |
1991年 | 279篇 |
1990年 | 243篇 |
1989年 | 240篇 |
1988年 | 129篇 |
1987年 | 86篇 |
1986年 | 62篇 |
1985年 | 56篇 |
1984年 | 47篇 |
1983年 | 36篇 |
1982年 | 36篇 |
1981年 | 27篇 |
1980年 | 24篇 |
1979年 | 8篇 |
1978年 | 6篇 |
1977年 | 6篇 |
1975年 | 6篇 |
1951年 | 16篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
31.
Fei Li Xin-Gang Wang Xiao Huang Ji-Xuan Liu Weichao Bao Guo-Jun Zhang Hongzhi Wang 《Journal of the European Ceramic Society》2018,38(14):4806-4813
We present a straightforward method via sol-gel process using polyethylene glycol (PEG) as phase separation inducer to prepare zirconium carbide/silicon carbide (ZrC/SiC) porous monoliths. Organic/inorganic hybrid gels are prepared using zirconium oxychloride, furfuryl alcohol, and tetraethyl orthosilicate as major starting materials. In the presence of PEG, crack-free hybrid monoliths are obtained by drying the wet gels under ambient pressure, whereas in the absence of PEG, the wet gels break into pieces as expected. PEG plays a key role in maintaining the macroscopic shape of the monoliths. After ceramization at 1300–1500?°C, ZrC/SiC porous monoliths are obtained. SEM and mercury intrusion porosimetry data show that PEG also has strong influence on the microstructures of the monoliths. The compressive strengths of the ceramic monoliths are in the range of 0.3 to 0.7?MPa. And their compressive behavior starts to differ due to the changes in their microstructures, especially the pore structure. 相似文献
32.
T. Galvin N.C. Hyatt W.M. Rainforth I.M. Reaney D. Shepherd 《Journal of the European Ceramic Society》2018,38(14):4585-4589
The molten salt method was used to synthesise the MAX phase compounds Ti2AlC and Ti3AlC2 from elemental powders. Between 900–1000?°C, Ti2AlC was formed alongside ancillary phases TiC and TiAl, which decreased in abundance with increasing synthesis temperature. Changing the stoichiometry and increasing the synthesis temperature to 1300?°C resulted in formation of Ti3AlC2 alongside Ti2AlC and TiC. The type of salt flux used had little effect on the product formation. The reaction pathway for Ti2AlC was determined to be the initial formation of TiC1-x templating on the graphite and titanium aluminides. 相似文献
33.
34.
A number of worms, named P2P (peer-to-peer) passive worms, have recently surfaced, which propagate in P2P file-sharing networks and have posed heavy threats to these networks. In contrast to the majority of Internet worms, it is by exploiting users’ legitimate activities instead of vulnerabilities of networks in which P2P passive worms propagate. This feature evidently slows down their propagation, which results in them not attracting an adequate amount of attention in literature. Meanwhile, this feature visibly increases the difficulty of detecting them, which makes it very possible for them to become epidemic. In this paper, we propose an analytical model for P2P passive worm propagation by adopting epidemiological approaches so as to identify their behaviors and predict the tendency of their propagation accurately. Compared with a few existing models, dynamic characteristics of P2P networks are taken into account. Based on this proposed model, the sufficient condition for the global stability of the worm free equilibrium is derived by applying epidemiological theories. Large scale simulation experiments have validated both the proposed model and the condition. 相似文献
35.
With increasing consumption of natural gas (NG), small NG reservoirs, such as coalbed methane and oil field associated gas, have recently drawn significant attention. Owing to their special characteristics (e.g., scattered distribution and small output), small-scale NG liquefiers are highly required. Similarly, the mixed refrigerant cycle (MRC) is suitable for small-scale liquefaction systems due to its moderate complexity and power consumption. In consideration of the above, this paper reviews the development of mobile miniature NG liquefiers in Technical Institute of Physics and Chemistry (TIPC), China. To effectively liquefy the scattered NG and overcome the drawbacks of existing technologies, three main improvements, i.e., low-pressure MRC process driven by oil-lubricated screw compressor, compact cold box with the new designed heat exchangers, and standardized equipment manufacturing and integrated process technology have been made. The development pattern of “rapid cluster application and flexible liquefaction center” has been eventually proposed. The small-scale NG liquefier developed by TIPC has reached a minimum liquefaction power consumption of about 0.35 kW·h/Nm3. It is suitable to exploit small remote gas reserves which can also be used in boil-off gas reliquefaction and distributed peak-shaving of pipe networks. 相似文献
36.
37.
含动力学抑制剂的天然气水合物相平衡研究对新型低剂量抑制剂的开发具有指导作用。在283.6 ~ 290.9 K和7.51 MPa ~ 15.97 MPa的温压范围内研究了抑制剂Inhibex501及其溶剂2-乙二醇单丁醚对甲烷水合物相平衡条件的影响。实验结果显示,0.5wt%和2.0wt%浓度的Inhibex501对甲烷水合物形成的热力学条件具有促进作用,能使甲烷水合物形成移向更高的温度或者更低的压力,而2-乙二醇单丁醚在浓度0.2wt% ~ 1.0wt%范围几乎不改变甲烷水合物形成的热力学条件,N-乙烯基己内酰胺与N-乙烯基吡咯烷酮的共聚物对水合物形成热力学条件的改变起主要作用。 相似文献
38.
The present study focuses on the sintering of silicon carbide-based ceramics (SiC) by liquid phase sintering (LPS) followed by characterization of the produced ceramics. AlN/Re2O3 mixtures were used as additives in the LPS process. In the first step, the LPS-SiC materials were produced in a graphite resistance furnace in the form of discs at different temperatures. The conditions with the best results regarding real density and relative density were taken as reference for sintering in the form of prismatic bars. In the second step, these samples were evaluated regarding fracture toughness (KIC), by the Single Edge V Notch Beam – SEVNB – method, and flexural strength. KIC behavior was evaluated according to the depth and curvature radius of the notches. Reliable KIC values were presented when the ceramic displayed a small curvature radius at the notch tip. When the radius was large, it did not maintain the square root singularity of the notch tip. Tests were carried out to determine KIC values in atmospheric air and water. KIC results were lower in water than air, with a decrease ranging between 2.56% and 11.26%. The observations indicated a direct grain size correlation between KIC values and fracture strength of the SiC ceramics. 相似文献
39.
In this paper, we study scheduling games under mixed coordination mechanisms on hierarchical machines. The two scheduling policies involved are ‐ and ‐, where ‐ (resp., ‐) policy sequences jobs in nondecreasing order of their hierarchies, and jobs of the same hierarchy in nonincreasing (resp., nondecreasing) order of their processing times. We first show the existence of a Nash equilibrium. Then we present the price of anarchy and the price of stability for the games with social costs of minimizing the makespan and maximizing the minimum machine load. All the bounds given in this paper are tight. 相似文献
40.
《Journal of the European Ceramic Society》2020,40(4):1644-1650
Possibility of formation of quinary and senary equimolar high entropy oxides from the Co-Cr-Fe-Mg-Mn-Ni-O system is presented. Different proposed compositions are synthesized using the solid-state reaction route at high temperatures (900−1100 °C) and quenched to room temperature. Phase composition of the samples is studied, showing tendency toward formation of two main phases: rock salt-structured Fm-3 m and spinel-structured Fd-3 m. It is documented that the annealing temperature has a profound effect on stability of both structures, and at 1100 °C usually the highest content of Fm-3 m phase is usually observed. Three different oxides, namely, (Co,Cr,Fe,Mn,Ni)3O4, (Co,Cr,Fe,Mg,Mn)3O4 and (Cr,Fe,Mg,Mn,Ni)3O4 are obtained as single-phase materials, which structure can be described as the high entropy Fd-3 m spinel one. The latter two compounds have not been previously reported in the literature. Activated character of the electrical conductivity dependence on temperature is observed, with relatively high total conductivity at high temperatures and corresponding high absolute values of Seebeck coefficient. 相似文献