全文获取类型
收费全文 | 164769篇 |
免费 | 24818篇 |
国内免费 | 6739篇 |
学科分类
工业技术 | 196326篇 |
出版年
2024年 | 326篇 |
2023年 | 1688篇 |
2022年 | 2819篇 |
2021年 | 4522篇 |
2020年 | 4658篇 |
2019年 | 5826篇 |
2018年 | 6060篇 |
2017年 | 6761篇 |
2016年 | 6968篇 |
2015年 | 8427篇 |
2014年 | 9814篇 |
2013年 | 12198篇 |
2012年 | 11055篇 |
2011年 | 11452篇 |
2010年 | 10903篇 |
2009年 | 10543篇 |
2008年 | 10232篇 |
2007年 | 9670篇 |
2006年 | 9386篇 |
2005年 | 7968篇 |
2004年 | 6388篇 |
2003年 | 6043篇 |
2002年 | 6712篇 |
2001年 | 5853篇 |
2000年 | 4630篇 |
1999年 | 3536篇 |
1998年 | 2172篇 |
1997年 | 1875篇 |
1996年 | 1649篇 |
1995年 | 1438篇 |
1994年 | 1105篇 |
1993年 | 851篇 |
1992年 | 655篇 |
1991年 | 494篇 |
1990年 | 409篇 |
1989年 | 280篇 |
1988年 | 242篇 |
1987年 | 168篇 |
1986年 | 98篇 |
1985年 | 88篇 |
1984年 | 63篇 |
1983年 | 60篇 |
1982年 | 47篇 |
1981年 | 39篇 |
1980年 | 35篇 |
1979年 | 20篇 |
1978年 | 12篇 |
1977年 | 17篇 |
1976年 | 16篇 |
1951年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
Su-Il Ri Song-Il Hong Jong-Chol Kim Ju-Hyok Wi 《International Journal of Hydrogen Energy》2021,46(5):3319-3328
We investigated some properties of the hydride Mg2FeH6 substituted with yttrium by a first principles calculation. Some experimental results showed that 4d transition metal, yttrium serves as a good catalyst for magnesium based hydrogen storage alloys, but there are a few theoretical studies about magnesium based hydrides substituted with it. Mg2FeH6 is regarded as a cheaper material than pure MgH2, while it is crystalized into Fm3m structure (space group 225). Although it has high hydrogen storage capacity, many investigations have not been devoted to it due to its extremely high thermodynamic stability. The yttrium substituted Mg2FeH6 exhibits very low energy of formation, and its desorption temperature, 75 °C is very suitable for practical hydrogen storage applications. Our results showed that Mg2FeH6 is destabilized effectively by yttrium substitution and introducing vacancy defects has additive effect to the improvement of dehydrogenation performance. 相似文献
42.
风积沙改性土的热膨胀特性对评价风积沙改性土路基温度稳定性至关重要.通过在风积沙中掺入不同质量的水泥、黏性土或聚丙烯纤维制成不同配比的改性土,测试改性土的热膨胀系数,研究外加材料的掺入量对改性土热膨胀特性的影响.试验结果表明:改性土的平均线膨胀系数随着水泥掺入量的增加总体呈增大趋势,随着聚丙烯纤维掺入量的增加而减小,随着黏性土掺入量的增加而增大.聚丙烯纤维的掺入可有效降低改性土的热膨胀系数.研究成果可为进一步优化改性土提供研究方向,为高温差沙漠地区工程建设中风积沙改性土温度裂缝的控制提供试验依据. 相似文献
43.
Towards a Better Prediction of Cell Settling on Nanostructure Arrays—Simple Means to Complicated Ends 下载免费PDF全文
Nina Buch‐Månson Sara Bonde Jessica Bolinsson Trine Berthing Jesper Nygård Karen L. Martinez 《Advanced functional materials》2015,25(21):3246-3255
Vertical arrays of nanostructures (NSs) are emerging as promising platforms for probing and manipulating live mammalian cells. The broad range of applications requires different types of interfaces, but cell settling on NS arrays is not yet fully controlled and understood. Cells are both seen to deform completely into NS arrays and to stay suspended like tiny fakirs, which have hitherto been explained with differences in NS spacing or density. Here, a better understanding of this phenomenon is provided by using a model that takes into account the extreme membrane deformation needed for a cell to settle into a NS array. It is shown that, in addition to the NS density, cell settling depends strongly on the dimensions of the single NS, and that the settling can be predicted for a given NS array geometry. The predictive power of the model is confirmed by experiments and good agreement with cases from the literature. Furthermore, the influence of cell‐related parameters is evaluated theoretically and a generic method of tuning cell settling through surface coating is demonstrated experimentally. These findings allow a more rational design of NS arrays for the numerous exciting biological applications where the mode of cell settling is crucial. 相似文献
44.
45.
Fundamental Evaluation of Power Supply and Rectifiers for Wireless Power Transfer Using Magnetic Resonant Coupling 下载免费PDF全文
This paper provides a fundamental analysis of a power supply and rectifiers for wireless power transfer using magnetic resonant coupling (MRC). MRC enables efficient wireless power transfer over middle‐range transfer distances. MRC for wireless power transfer should operate at a high frequency in the industry science medical band, such as 13.56 MHz, because the size of the transfer device decreases at higher transfer frequencies. Therefore, the output frequency of the power supply on the transmitting side should be 13.56 MHz. In addition, the rectifier on the receiving side is operated at a high frequency. This paper focuses on the reflected power in the power supply and rectifiers. Thus, the parametric design method is clarified for the power supply, including a low‐pass filter to match the output, the impedance of the power supply with the characteristic impedance of the transmission line. In addition, the effects on the rectifiers of silicon carbide and gallium nitride diodes are confirmed by performing an experiment and a loss analysis. 相似文献
46.
Choi Paul Santos Christian Ariane Kim Min-Kun Jung Hyunsook Hong Do-Young Koo Junemo 《Journal of Mechanical Science and Technology》2021,35(11):5007-5022
Journal of Mechanical Science and Technology - This study delivers equations useful for low-height pleated fibrous filter design: two pressure drop equations and one set of optimum design equations... 相似文献
47.
48.
49.
Nazir Kizzie‐Hayford Doris Jaros Yvonne Schneider Harald Rohm 《International Journal of Food Science & Technology》2015,50(2):381-388
A standard method for the extraction of tiger nut milk has been introduced. It has been shown that, although milling duration improves the yield of tiger nut milk solids and its nutrient composition, there is a quantifiable loss of nutrient in the pressing residue during milk extraction. Milling duration improved the colloidal stability of the milk against creaming during 16 h of storage. A higher milling intensity resulted in the aggregation of biological polymers which resulted in colloidal destabilisation. Milling improved the lightness and stability and reduced browning rate of the tiger nut milk during storage. This report is important for the production of tiger nut milk of consistent and comparable characteristics. Milling has been introduced as a processing method for the qualitative and quantitative modulation of the properties of tiger nut milk. It is recommended to develop further strategies to improve the colloidal stability of tiger nut milk as a beverage. 相似文献
50.