全文获取类型
收费全文 | 3720篇 |
免费 | 65篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 32篇 |
综合类 | 14篇 |
化学工业 | 520篇 |
金属工艺 | 77篇 |
机械仪表 | 59篇 |
建筑科学 | 51篇 |
能源动力 | 90篇 |
轻工业 | 139篇 |
水利工程 | 5篇 |
石油天然气 | 4篇 |
无线电 | 439篇 |
一般工业技术 | 440篇 |
冶金工业 | 1506篇 |
原子能技术 | 16篇 |
自动化技术 | 397篇 |
出版年
2023年 | 13篇 |
2022年 | 55篇 |
2021年 | 55篇 |
2020年 | 20篇 |
2019年 | 23篇 |
2018年 | 33篇 |
2017年 | 32篇 |
2016年 | 49篇 |
2015年 | 57篇 |
2014年 | 83篇 |
2013年 | 178篇 |
2012年 | 116篇 |
2011年 | 145篇 |
2010年 | 141篇 |
2009年 | 166篇 |
2008年 | 138篇 |
2007年 | 144篇 |
2006年 | 108篇 |
2005年 | 79篇 |
2004年 | 81篇 |
2003年 | 63篇 |
2002年 | 72篇 |
2001年 | 48篇 |
2000年 | 44篇 |
1999年 | 68篇 |
1998年 | 513篇 |
1997年 | 273篇 |
1996年 | 207篇 |
1995年 | 99篇 |
1994年 | 98篇 |
1993年 | 98篇 |
1992年 | 31篇 |
1991年 | 49篇 |
1990年 | 31篇 |
1989年 | 40篇 |
1988年 | 23篇 |
1987年 | 19篇 |
1986年 | 22篇 |
1985年 | 23篇 |
1984年 | 17篇 |
1983年 | 8篇 |
1982年 | 18篇 |
1981年 | 20篇 |
1980年 | 15篇 |
1979年 | 8篇 |
1978年 | 7篇 |
1977年 | 43篇 |
1976年 | 83篇 |
1975年 | 6篇 |
1973年 | 5篇 |
排序方式: 共有3789条查询结果,搜索用时 0 毫秒
1.
2.
Multifunctional 3D Patternable Drug‐Embedded Nanocarrier‐Based Interfaces to Enhance Signal Recording and Reduce Neuron Degeneration in Neural Implantation
下载免费PDF全文
![点击此处可从《Advanced materials (Deerfield Beach, Fla.)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
3.
4.
Scientometrics - The expanding presence of multinational research teams highlights the importance of characterizing the outcomes of international collaboration. Herein, we characterize the... 相似文献
5.
Hsieh-Hung Hsieh Liang-Hung Lu 《Microwave and Wireless Components Letters, IEEE》2006,16(10):552-554
A novel circuit topology for low-phase-noise voltage controlled oscillators (VCOs) is presented in this letter. By employing a PMOS cross-coupled pair with a capacitive feedback, superior circuit performance can be achieved especially at higher frequencies. Based on the proposed architecture, a prototype VCO implemented in a 0.18-/spl mu/m CMOS process is demonstrated for K-band applications. From the measurement results, the VCO exhibits a 510-MHz frequency tuning range at 20GHz. The output power and the phase noise at 1-MHz offset are -3dBm and -111dBc/Hz, respectively. The fabricated circuit consumes a dc power of 32mW from a 1.8-V supply voltage. 相似文献
6.
Using AuGeNiCr multilayered metals as the wafer bonding medium, long-wavelength GaInAsP/InP vertical cavity surface emitting lasers employing Al-oxide/Si as the upper and lower distributed Bragg reflectors were fabricated on Si substrate with the bonding interface formed outside the vertical cavity surface emitting laser cavity. Laser emission at 1.545 μm was measured under pulsed operations near room temperature. The low-temperature metallic bonding process demonstrates a great potential in device fabrication 相似文献
7.
Pax genes are expressed in specific patterns in the nervous system during development and in the adult. Recent findings suggest a link between the expression of Pax-2 and axonal guidance. Mice with a targeted deletion of Pax-2 are an excellent tool for studying axonal pathfinding at the molecular level, especially with respect to the optic chiasm. The date reviewed here suggest that Pax-2 regulates the expression of surface molecules involved in contact attraction and that the mutual regulation of the expression of Pax-2 and the Sonic hedgehog gene is of importance in the formation of the chiasm region. 相似文献
8.
LL McCabe 《Canadian Metallurgical Quarterly》1998,152(9):839-842
Agrobacterium tumefaciens transfers part of its Ti plasmid, the T-DNA, to plant cells during tumorigenesis. It is routinely used for the genetic modification of a wide range of plant species. We report that A. tumefaciens can also transfer its T-DNA efficiently to the filamentous fungus Aspergillus awamori, demonstrating DNA transfer between a prokaryote and a filamentous fungus. We transformed both protoplasts and conidia with frequencies that were improved up to 600-fold as compared with conventional techniques for transformation of A. awamori protoplasts. The majority of the A. awamori transformants contained a single T-DNA copy randomly integrated at a chromosomal locus. The T-DNA integrated into the A. awamori genome in a manner similar to that described for plants. We also transformed a variety of other filamentous fungi, including Aspergillus niger, Fusarium venenatum, Trichoderma reesei, Colletotrichum gloeosporioides, Neurospora crassa, and the mushroom Agaricus bisporus, demonstrating that transformation using A. tumefaciens is generally applicable to filamentous fungi. 相似文献
9.
We have shown that normal and human papillomavirus (HPV) type 16 immortalized human foreskin keratinocytes are growth inhibited by tumor necrosis factor alpha (TNF-alpha), whereas HPV-18- and SV40-immortalized keratinocytes are resistant to this cytokine (1). In this report, we investigated the expression of mitotic regulatory proteins, such as cyclin A, cyclin B, and p34cdc2. After exposure to TNF-alpha, normal and HPV-16-immortalized cells exhibited a dramatic decrease in the expression of these proteins. In contrast, no alteration in the levels of these proteins was observed after treatment of the resistant cell lines, as well as two HPV-positive cervical carcinoma cell lines. Expression of cyclin E does not seem to be modulated by TNF-alpha in any of the cells tested. On the other hand, cyclin D1, expression is slightly increased in normal keratinocytes and in the HPV-16-immortalized cells, whereas no alteration was observed in the HPV-18-transfected cells. The phosphorylation state of pRb correlated with cell growth; sensitive cells, which accumulate in G0-G1, after exposure to TNF-alpha, exhibited an accumulation of hypophosphorylated pRb, whereas no effect on pRb phosphorylation was observed for HPV-18-immortalized cells. These results clearly correlate with TNF-alpha-induced growth arrest in G0-G1. 相似文献
10.
Enhancement of islanding-detection of distributed generation systems via wavelet transform-based approaches 总被引:1,自引:1,他引:0
Cheng-Tao Hsieh Jeu-Min Lin Shyh-Jier Huang 《International Journal of Electrical Power & Energy Systems》2008,30(10):575-580
In this paper, a wavelet transform-based approach is proposed to detect the occurrence of islanding events in distributed generation systems. Thanks to time–frequency localization capabilities exhibited by wavelet transform, the approach embedded with this transform technique has grasped the appearance of the islanding event in a highly effective manner. Moreover, for those regions which are in need of a better visualization, the proposed approach would serve as an efficient aid such that the mains power disconnection can be better distinguished. To validate the feasibility of this approach, the method has been validated through several scenarios. Test results supported the effectiveness of the method for the application considered. 相似文献