全文获取类型
收费全文 | 148677篇 |
免费 | 10498篇 |
国内免费 | 5342篇 |
专业分类
电工技术 | 9124篇 |
技术理论 | 8篇 |
综合类 | 13832篇 |
化学工业 | 10997篇 |
金属工艺 | 6679篇 |
机械仪表 | 16544篇 |
建筑科学 | 30108篇 |
矿业工程 | 5046篇 |
能源动力 | 3687篇 |
轻工业 | 5895篇 |
水利工程 | 4509篇 |
石油天然气 | 5989篇 |
武器工业 | 1917篇 |
无线电 | 9812篇 |
一般工业技术 | 15133篇 |
冶金工业 | 3630篇 |
原子能技术 | 938篇 |
自动化技术 | 20669篇 |
出版年
2024年 | 250篇 |
2023年 | 1466篇 |
2022年 | 2530篇 |
2021年 | 3284篇 |
2020年 | 3599篇 |
2019年 | 2800篇 |
2018年 | 2736篇 |
2017年 | 3521篇 |
2016年 | 4069篇 |
2015年 | 4382篇 |
2014年 | 10375篇 |
2013年 | 8490篇 |
2012年 | 10527篇 |
2011年 | 11267篇 |
2010年 | 9481篇 |
2009年 | 9878篇 |
2008年 | 8915篇 |
2007年 | 10769篇 |
2006年 | 9169篇 |
2005年 | 8022篇 |
2004年 | 6521篇 |
2003年 | 6016篇 |
2002年 | 4827篇 |
2001年 | 4041篇 |
2000年 | 3336篇 |
1999年 | 2620篇 |
1998年 | 2126篇 |
1997年 | 1796篇 |
1996年 | 1537篇 |
1995年 | 1298篇 |
1994年 | 1065篇 |
1993年 | 726篇 |
1992年 | 615篇 |
1991年 | 514篇 |
1990年 | 356篇 |
1989年 | 320篇 |
1988年 | 245篇 |
1987年 | 171篇 |
1986年 | 105篇 |
1985年 | 107篇 |
1984年 | 154篇 |
1983年 | 97篇 |
1982年 | 114篇 |
1981年 | 55篇 |
1980年 | 52篇 |
1979年 | 44篇 |
1978年 | 26篇 |
1977年 | 22篇 |
1959年 | 16篇 |
1951年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
3.
《Journal of dairy science》2022,105(4):3176-3191
Milk concentrates are used in the manufacturing of dairy products such as yogurt and cheese or are processed into milk powder. Processes for the nonthermal separation of water and valuable milk ingredients are becoming increasingly widespread at farm level. The technical barriers to using farm-manufactured milk concentrate in dairies are minimal, hence the suspicion that the practice of on-farm raw milk concentration is still fairly uncommon for economic reasons. This study, therefore, set out to investigate farmers' potential willingness to adopt a raw milk concentration plant. The empirical analysis was based on discrete choice experiments with 75 German dairy farmers to identify preferences and the possible adoption of on-farm raw milk concentration. The results showed that, in particular, farmers who deemed the current milk price to be insufficient viewed on-farm concentration using membrane technology as an option for diversifying their milk sales. We found no indication that adoption would be impeded by a lack of trustworthy information on milk processing technologies or capital. 相似文献
4.
《Ceramics International》2022,48(20):29862-29872
Thermal shock parameters (R, R''', R'''' and Rst) of MgAlON–MgO composites obtained with additions of spent MgO–C brick were calculated using measured mechanical properties and thermal expansion coefficient, determining their resistance to fracture initiation and crack propagation. The cyclic thermal shock experiments of MgAlON–MgO composites performed from 1398 K to ambient temperature indicate that as number of thermal shock cycle increases, retained strength ratio of MgAlON and MgAlON–4.2 wt%MgO sharply decrease and then keep constant, while that of MgAlON–10.5 wt%MgO and MgAlON–15.7 wt%MgO slowly decrease. The reason for the difference is that MgAlON and MgAlON–4.2 wt%MgO show low value of R''' and R'''', and high value of R and Rst. Moreover, precipitation of impurity containing Fe may play a positive role in improvement of thermal shock resistance of MgAlON–MgO composites. MgAlON?4.2 wt%MgO has the maximum retained strength (55 MPa) even after 5 thermal shock cycles, which is expected to be used in the metallurgical industry. 相似文献
5.
《International Journal of Hydrogen Energy》2022,47(18):10137-10155
In this work, hydrate based separation technique was combined with membrane separation and amine-absorption separation technologies to design hybrid processes for separation of CO2/H2 mixture. Hybrid processes are designed in the presence of different types of hydrate promoters. The conceptual processes have been developed using Aspen HYSYS. Proposed processes were simulated at different flow rates for the feed stream. A comprehensive cost model was developed for economic analysis of novel processes proposed in this study. Based on the results from process simulation and equipment sizing, the amount of total energy consumption, fixed cost, variable cost, and total cost were calculated per unit weight of captured CO2 for various flow rates of feed stream and in the presence of different hydrate promoters. Results showed that combination of hydrate formation separation technique with membrane separation technology results in a CO2 capture process with lowest energy consumption and total cost per unit weight of captured CO2. As split fraction and heat of hydrate formation increases, the share of hydrate formation section in total energy consumption increases. When TBAB is applied as hydrate promoter, due to its higher hydrate separation efficiency, more amount of CO2 is captured in hydrate formation section and consequently the total cost for process decreases considerably. Hybrid hydrate-membrane process in the presence of TBAB as hydrate promoter with 29.47 US$/ton CO2 total cost is the best scheme for hybrid hydrate CO2 capture process. Total cost for this process is lower than total cost for single MDEA-based absorption process as the mature technology for CO2 capture. 相似文献
6.
《Mechatronics》2022
A large-scale high-precision scan stage is important equipment in the industrial productions of micro-fabrication such as flat panel display (FPD) lithography systems. Designing controllers for multi-input multi-output (MIMO) systems is time-consuming and needs experience because of the interaction between each axis and many controller tuning parameters. The aim of this study is to develop a peak filter design method based on frequency response data to reduce repetitive disturbance. This data-based approach does not use the model and only uses the frequency response data of the controlled system and the disturbance spectrum calculated from the scanning error data (Contribution 1). The peak filter is designed by convex optimization and satisfies robust stability conditions for six-degree-of-freedom systems (Contribution 2). The control performance of the designed peak filter is experimentally demonstrated with an industrial MIMO large-scale high-precision scan stage in reducing the scanning error of the main stroke of the translation along the -axis (Contribution 3). 相似文献
7.
Donghai Xu Peng Feng Yang Wang Wanpeng Yang Yu Wang Shaoyan Sun 《American Institute of Chemical Engineers》2022,68(2):e17472
Corrosion and salt deposition problems severely restrict the industrialization of supercritical water oxidation. Transpiring wall reactor can effectively weaken these two problems by a protective water film. In this work, methanol was selected as organic matter, and the influences of vital structural parameters on water film properties and organic matter removal were studied via numerical simulation. The results indicate that higher than 99% of methanol conversion could be obtained and hardly affected by transpiration water layer, transpiring wall porosity and inner diameter. Increasing layer and porosity reduced reactor center temperature, but inner diameter's influence was lower relatively. Water film temperature reduced but coverage rate raised as layer, porosity, and inner diameter increased. Notably, the whole reactor was in supercritical state and coverage rate was only approximately 85% in the case of one layer. Increasing reactor length affected slightly the volume of the upper supercritical zone but enlarged the subcritical zone. 相似文献
8.
《International Journal of Hydrogen Energy》2022,47(73):31202-31222
Dark fermentation of sugarcane vinasse can be used as a “cleaning” step to remove sulfate prior to methanogenesis because sulfidogenic conditions can be successfully established in parallel with biohydrogen production. Using a 22 central composite rotational design (CCRD) and response surface methodology (RSM), this study assessed the impacts of bicarbonate and sulfate availability on the establishment of sulfidogenesis in the thermophilic (55 °C) fermentation of vinasse in batch reactors, equally assessing the impacts on biohydrogen evolution. CCRD-RSM results indicated the favoring of biohydrogen production at the lowest sulfate and bicarbonate concentrations, whilst the opposite was observed for sulfidogenesis. Glycerol, lactate, and hydrogen were the preferential electron donors utilized by sulfate-reducing bacteria (SRB), whilst ethanol was markedly consumed only at high sulfate concentrations. SRB were inhibited by sodium when dosing excess NaHCO3 and Na2SO4. Complementary tests revealed maximum biohydrogen production (2.40 mmol) out of the CCRD, at pH exceeding 7.5 with no interference of sulfidogenesis. Non-efficient biohydrogen production was observed at low pH (<5.0; ~1.90 mmol) because the uptake of lactate was inhibited. Meanwhile, homoacetogenesis was established under intermediate pH range (5.5–6.5), as revealed by the accumulation of acetate (up to 2.5 g L?1). 16S rRNA gene amplicon sequencing further revealed the genera Thermoanaerobacterium/Pseudoclostridium, Desulfotomaculum/Desulfohalotomaculum and Sporomusaceae/Moorella as the main biohydrogen-producing, sulfate-removing and biohydrogen-consuming (homoacetogens) microbial groups, respectively. Hence, using a single inoculum source, vinasse may provide a butyrate-rich (along with biohydrogen-rich biogas) or a sulfate-free and acetate-rich fermented effluent, depending mainly on proper pH control. 相似文献
9.
10.