全文获取类型
收费全文 | 4156篇 |
免费 | 102篇 |
国内免费 | 14篇 |
专业分类
电工技术 | 174篇 |
综合类 | 4篇 |
化学工业 | 1066篇 |
金属工艺 | 167篇 |
机械仪表 | 75篇 |
建筑科学 | 65篇 |
矿业工程 | 3篇 |
能源动力 | 159篇 |
轻工业 | 338篇 |
水利工程 | 9篇 |
石油天然气 | 4篇 |
无线电 | 301篇 |
一般工业技术 | 746篇 |
冶金工业 | 705篇 |
原子能技术 | 114篇 |
自动化技术 | 342篇 |
出版年
2023年 | 11篇 |
2022年 | 41篇 |
2021年 | 67篇 |
2020年 | 44篇 |
2019年 | 54篇 |
2018年 | 58篇 |
2017年 | 53篇 |
2016年 | 88篇 |
2015年 | 62篇 |
2014年 | 93篇 |
2013年 | 171篇 |
2012年 | 174篇 |
2011年 | 207篇 |
2010年 | 173篇 |
2009年 | 186篇 |
2008年 | 197篇 |
2007年 | 187篇 |
2006年 | 158篇 |
2005年 | 135篇 |
2004年 | 141篇 |
2003年 | 132篇 |
2002年 | 100篇 |
2001年 | 82篇 |
2000年 | 74篇 |
1999年 | 87篇 |
1998年 | 322篇 |
1997年 | 176篇 |
1996年 | 119篇 |
1995年 | 81篇 |
1994年 | 90篇 |
1993年 | 88篇 |
1992年 | 72篇 |
1991年 | 50篇 |
1990年 | 39篇 |
1989年 | 41篇 |
1988年 | 26篇 |
1987年 | 43篇 |
1986年 | 27篇 |
1985年 | 40篇 |
1984年 | 28篇 |
1983年 | 21篇 |
1982年 | 38篇 |
1981年 | 32篇 |
1980年 | 21篇 |
1979年 | 25篇 |
1978年 | 14篇 |
1977年 | 22篇 |
1976年 | 37篇 |
1975年 | 7篇 |
1974年 | 8篇 |
排序方式: 共有4272条查询结果,搜索用时 15 毫秒
1.
Masahiro Sato Miyu Koriyama Satoshi Watanabe Masato Ohtsuka Takayuki Sakurai Emi Inada Issei Saitoh Shingo Nakamura Kazuchika Miyoshi 《International journal of molecular sciences》2015,16(8):17838-17856
Some reports demonstrated successful genome editing in pigs by one-step zygote microinjection of mRNA of CRISPR/Cas9-related components. Given the relatively long gestation periods and the high cost of housing, the establishment of a single blastocyst-based assay for rapid optimization of the above system is required. As a proof-of-concept, we attempted to disrupt a gene (GGTA1) encoding the α-1,3-galactosyltransferase that synthesizes the α-Gal epitope using parthenogenetically activated porcine oocytes. The lack of α-Gal epitope expression can be monitored by staining with fluorescently labeled isolectin BS-I-B4 (IB4), which binds specifically to the α-Gal epitope. When oocytes were injected with guide RNA specific to GGTA1 together with enhanced green fluorescent protein (EGFP) and human Cas9 mRNAs, 65% (24/37) of the developing blastocysts exhibited green fluorescence, although almost all (96%, 23/24) showed a mosaic fluorescent pattern. Staining with IB4 revealed that the green fluorescent area often had a reduced binding activity to IB4. Of the 16 samples tested, six (five fluorescent and one non-fluorescent blastocysts) had indel mutations, suggesting a correlation between EGFP expression and mutation induction. Furthermore, it is suggested that zygote microinjection of mRNAs might lead to the production of piglets with cells harboring various mutation types. 相似文献
2.
Tomoya Suzuki Kento Shiota Yu-ichiro Izato Masahiro Komori Koichi Sato Yasuyuki Takai Takayuki Ninomiya Atsumi Miyake 《International Journal of Hydrogen Energy》2021,46(11):8329-8343
Although hydrogen refueling stations (HRSs) are becoming widespread across Japan and are essential for the operation of fuel cell vehicles, they present potential hazards. A large number of accidents such as explosions or fires have been reported, rendering it necessary to conduct a number of qualitative and quantitative risk assessments for HRSs. Current safety codes and technical standards related to Japanese HRSs have been established based on the results of a qualitative risk assessment and quantitative effectiveness validation of safety measures over ten years ago. In the last decade, there has been much development in the technologies of the components or facilities used in domestic HRSs and much operational experience as well as knowledge to use hydrogen in HRSs safely have been gained through years of commercial operation. The purpose of the present study is to conduct a quantitative risk assessment (QRA) of the latest HRS model representing Japanese HRSs with the most current information and to identify the most significant scenarios that pose the greatest risks to the physical surroundings in the HRS model. The results of the QRA show that the risk contours of 10?3 and 10?4 per year were confined within the HRS boundaries, whereas the risk contours of 10?5 and 10?6 per year are still present outside the HRS. Comparing the breakdown of the individual risks (IRs) at the risk ranking points, we conclude that the risk of jet fire demonstrates the highest contribution to the risks at all of the risk ranking points and outside the station. To reduce these risks and confine the risk contour of 10?6 per year within the HRS boundaries, it is necessary to consider risk mitigation measures for jet fires. 相似文献
3.
4.
5.
A comparative study of DPSK and OOK WDM transmission over transoceanic distances and their performance degradations due to nonlinear phase noise 总被引:1,自引:0,他引:1
Mizuochi T. Ishida K. Kobayashi T. Abe J. Kinjo K. Motoshima K. Kasahara K. 《Lightwave Technology, Journal of》2003,21(9):1933-1943
We have compared experimentally the transmission performance of return-to-zero differential phase-shift keying (RZ-DPSK) with RZ-ON-OFF keying (OOK), nonreturn-to-zero differential phase-shift keying (NRZ-DPSK), and NRZ-OOK for 100/spl times/10-Gb/s transmission with a spectral efficiency of 0.22 b/s/Hz over transoceanic distances. The Q degradation of the RZ-DPSK after transmission over 9180 km was 3 dB greater than that of RZ-OOK. The experimental results clearly showed the major cause of degradation for DPSK is not cross-phase modulation but self-phase modulation. The calculated nonlinear phase noise, i.e., the Gordon-Mollenauer effect, agreed with the experimental results. A distributed-Raman-amplifier assisted erbium-doped-fiber-amplified transmission line acted well in reducing the nonlinear phase noise. 相似文献
6.
A novel super-multi-fibre planar lightwave circuit (PLC) connector, designed to connect tens of optical fibres and a PLC for super-multichannel PLC-based optical modules with a receptacle interface, is proposed. This connector employs an angled connection instead of a PC connection. A 0.127 mm pitch 32-fibre connector is also demonstrated, which exhibits low connection and high return losses. 相似文献
7.
Peter V. Sushko Alexander L. ShlugerKatsuro Hayashi Masahiro HiranoHideo Hosono 《Thin solid films》2003,445(2):161-167
Recently it has been discovered that a nano-porous main group oxide 12CaO·7Al2O3 (C12A7) can be converted from a wide-gap insulator to a good transparent conductor. Using ab initio modelling we explain good conductivity of this material by very small barriers for hopping of localised electrons between neighbouring positive cages. We show that optical absorption of C12A7 in infrared region and at energies higher than 2.7 eV is due to inter-cage and intra-cage electron transitions, respectively. The proposed mechanisms can be useful in further search for conducting transparent media. 相似文献
8.
9.
1-GHz-spaced 16-channel arrayed-waveguide grating for a wavelength reference standard in DWDM network systems 总被引:3,自引:0,他引:3
We fabricated a 1-GHz-spaced 16-channel arrayed-waveguide grating (AWG) by using a new AWG configuration where the path of each arrayed waveguide winds backward and forward across a 4-in diameter wafer without crossing any other waveguides. The ultra-narrow (< 1 GHz) and stable transmission bands of this AWG can be used to construct a wavelength reference standard covering the S, C, and L bands in the dense wavelength-division-multiplexing network systems whose frequency deviation is /spl plusmn/160 MHz. 相似文献
10.
Takeshi Shiofuku Norihiro Abe Yoshihiro Tabuchi Hirokazu Taki Shoujie He 《Artificial Life and Robotics》2008,13(1):290-293
This paper presents an approach of measuring in real-time the vector of finger that is pointing to an object. DSP is used
in the operation processing unit in order to do the real-time processing. The steps include the extraction of flesh-colored
regions from an image, the labeling of the flesh-colored regions, and the detection of two characteristic positions on the
finger so that the direction that the finger is pointing at will be calculated. The entire process takes about 29 msec, which
makes it possible to have the frame rate of 34 fps. With this frame rate, this measurement approach is considered real-time
and promising to be merged into other application systems.
This work was presented in part at the 13th International Symposium on Artificial Life and Robotics, Oita, Japan, January
31–February 2, 2008 相似文献