全文获取类型
收费全文 | 4585篇 |
免费 | 408篇 |
国内免费 | 245篇 |
专业分类
电工技术 | 396篇 |
综合类 | 479篇 |
化学工业 | 970篇 |
金属工艺 | 216篇 |
机械仪表 | 77篇 |
建筑科学 | 303篇 |
矿业工程 | 165篇 |
能源动力 | 129篇 |
轻工业 | 882篇 |
水利工程 | 90篇 |
石油天然气 | 205篇 |
武器工业 | 9篇 |
无线电 | 176篇 |
一般工业技术 | 312篇 |
冶金工业 | 407篇 |
原子能技术 | 46篇 |
自动化技术 | 376篇 |
出版年
2024年 | 16篇 |
2023年 | 81篇 |
2022年 | 120篇 |
2021年 | 125篇 |
2020年 | 134篇 |
2019年 | 125篇 |
2018年 | 118篇 |
2017年 | 144篇 |
2016年 | 175篇 |
2015年 | 182篇 |
2014年 | 253篇 |
2013年 | 310篇 |
2012年 | 308篇 |
2011年 | 308篇 |
2010年 | 225篇 |
2009年 | 259篇 |
2008年 | 226篇 |
2007年 | 266篇 |
2006年 | 263篇 |
2005年 | 243篇 |
2004年 | 202篇 |
2003年 | 172篇 |
2002年 | 131篇 |
2001年 | 146篇 |
2000年 | 105篇 |
1999年 | 86篇 |
1998年 | 79篇 |
1997年 | 68篇 |
1996年 | 55篇 |
1995年 | 39篇 |
1994年 | 40篇 |
1993年 | 39篇 |
1992年 | 33篇 |
1991年 | 16篇 |
1990年 | 33篇 |
1989年 | 15篇 |
1988年 | 14篇 |
1987年 | 12篇 |
1986年 | 6篇 |
1985年 | 11篇 |
1984年 | 7篇 |
1981年 | 4篇 |
1969年 | 3篇 |
1965年 | 3篇 |
1964年 | 4篇 |
1961年 | 3篇 |
1958年 | 5篇 |
1956年 | 3篇 |
1955年 | 3篇 |
1954年 | 2篇 |
排序方式: 共有5238条查询结果,搜索用时 15 毫秒
1.
Shingo Urata Hiroyuki Hijiya Kazuhiko Niwano Jun Matsui 《Journal of the American Ceramic Society》2022,105(6):4200-4207
To theoretically explore amorphous materials with a sufficiently low dielectric loss, which are essential for next-generation communication devices, the applicability of a nonequilibrium molecular dynamics simulation employing an external alternating electric field was examined using alkaline silicate glass models. In this method, the dielectric loss is directly evaluated as the phase shift of the dipole moment from the applied electric field. This method enabled us to evaluate the dielectric loss in a wide frequency range from 1 GHz to 10 THz. It was observed that the dielectric loss reaches its maximum at a few THz. The simulation method was found to qualitatively reproduce the effects of alkaline content and alkaline type on the dielectric loss. Furthermore, it reasonably reproduced the effect of mixed alkalines on the dielectric loss, which was observed in our experiments on sodium and/or potassium silicate glasses. Alkaline mixing was thus found to reduce the dielectric loss. 相似文献
2.
Wenshu Chen Jiajun Gu Yongping Du Fang Song Fanxing Bu Jinghan Li Yang Yuan Ruichun Luo Qinglei Liu Di Zhang 《Advanced functional materials》2020,30(25)
Large‐scale production of hydrogen from water‐alkali electrolyzers is impeded by the sluggish kinetics of hydrogen evolution reaction (HER) electrocatalysts. The hybridization of an acid‐active HER catalyst with a cocatalyst at the nanoscale helps boost HER kinetics in alkaline media. Here, it is demonstrated that 1T–MoS2 nanosheet edges (instead of basal planes) decorated by metal hydroxides form highly active / heterostructures, which significantly enhance HER performance in alkaline media. Featured with rich / sites, the fabricated 1T–MoS2 QS/Ni(OH)2 hybrid (quantum sized 1T–MoS2 sheets decorated with Ni(OH)2 via interface engineering) only requires overpotentials of 57 and 112 mV to drive HER current densities of 10 and 100 mA cm?2, respectively, and has a low Tafel slope of 30 mV dec?1 in 1 m KOH. So far, this is the best performance for MoS2‐based electrocatalysts and the 1T–MoS2 QS/Ni(OH)2 hybrid is among the best‐performing non‐Pt alkaline HER electrocatalysts known. The HER process is durable for 100 h at current densities up to 500 mA cm?2. This work not only provides an active, cost‐effective, and robust alkaline HER electrocatalyst, but also demonstrates a design strategy for preparing high‐performance catalysts based on edge‐rich 2D quantum sheets for other catalytic reactions. 相似文献
3.
Bioremediation by alkaline protease (AkP) from edible mushroom Termitomyces clypeatus: optimization approach based on statistical design and characterization for diverse applications
下载免费PDF全文
![点击此处可从《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
4.
5.
6.
Li Yu-cheng He Ming Dept.of Civil Engineering Dalian Univ.of Technology Dalian P.R.China 《水动力学研究与进展(B辑)》1993,(4)
Based on model test,the statistical distribution of extreme values of wave-current in-line forces acting on vertical circular cylinder is analyzed in this paper.It is shownthat the results calculated by the simplified method,proposed by authors,agree well with the testdata;Weibull distribution is also adoptable in the region of high KC number, and the shapeparameter a and scale parameter β are related well with KC number respectively. 相似文献
7.
In this paper the optimal H∞, general distance problem, for continuous-time systems, with a prescribed degree on the solution is studied. The approach is based on designing the Hankel singular values using an imbedding idea. The problem is first imbedded into another problem with desirable characteristics on the Hankel singular values, then the solution to the original problem is retracted via a compression. The result is applicable to both the one-block and the four-block problems. A special case is given for illustration. 相似文献
8.
Robben J.; der Schueren J.Van; Verhasselt P.; Aert R.; Volckaert G. 《Protein engineering, design & selection : PEDS》1995,8(2):159-165
The deletion of nine residues from the C-terminus of the bacterialchloramphenicol acetyltransferase (CAT) results in depositionof the mutant protein in cytoplasmic inclusion bodies and lossof chloramphenicol resistance in Escherichia coli. This foldingdefect is relieved by C-terminal fusion of the polypeptide withas few as two residues. Based on these observations, efficientpositive selection for the cloning of DNA fragments has beendemonstrated. The cloning vector encodes a C-terminally truncatedCAT protein. Restriction sites in front of the stop codon allowthe insertion of target DNA, resulting in the production ofproperly folded CAT fusion proteins and regained chloramphenicolresistance. The positive selection of recombinants is accomplishedby growth of transformants on chloramphenicol-containing agarplates. The method appears particularly convenient for the cloningof DNA fragments amplified by the PCR because minimal informationto restore CAT folding can be included in the primers. The cloningof random sequences shows that the folding defect can be relievedby fusion to a wide variety of peptides, providing great flexibilityto the positive selection system. This vector may also contributeto the determination of the role of the C-terminus in CAT folding. 相似文献
9.
温克勤 《徐州建筑职业技术学院学报》2005,5(1):1-6
对儒家伦理的基本价值与基本特点以及局限性进行了疏理和分析,对于国内外学者对儒家伦理的肯定性评价和提出的有关儒学研究的理论方法作出了评介,在此基础上提出了研究儒家伦理的几点认识和启示. 相似文献
10.
When Teachers' and Parents' Values Differ: Teachers' Ratings of Academic Competence in Children From Low-Income Families. 总被引:1,自引:0,他引:1
The authors examined predictors of teachers' ratings of academic competence of 105 kindergarten children from low-income families. Teachers rated target children's expected competence in literacy and math and completed questions about their perceptions of congruence-dissonance between themselves and the child's parents regarding education-related values. Independent examiners assessed children's literacy and math skills. Teachers' instructional styles were observed and rated along dimensions of curriculum-centered and student-centered practices. Controlling for children's skills and socioeconomic status, teachers rated children as less competent when they perceived value differences with parents. These patterns were stronger for teachers who exhibited curriculum-centered, rather than student-centered, practices. The findings suggest a mechanism by which some children from low-income families enter a path of diminished expectations. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献