全文获取类型
收费全文 | 2493篇 |
免费 | 68篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 115篇 |
综合类 | 5篇 |
化学工业 | 648篇 |
金属工艺 | 48篇 |
机械仪表 | 65篇 |
建筑科学 | 40篇 |
能源动力 | 75篇 |
轻工业 | 154篇 |
水利工程 | 3篇 |
无线电 | 224篇 |
一般工业技术 | 445篇 |
冶金工业 | 418篇 |
原子能技术 | 126篇 |
自动化技术 | 199篇 |
出版年
2023年 | 10篇 |
2022年 | 40篇 |
2021年 | 48篇 |
2020年 | 25篇 |
2019年 | 38篇 |
2018年 | 39篇 |
2017年 | 46篇 |
2016年 | 50篇 |
2015年 | 47篇 |
2014年 | 51篇 |
2013年 | 122篇 |
2012年 | 80篇 |
2011年 | 133篇 |
2010年 | 99篇 |
2009年 | 97篇 |
2008年 | 113篇 |
2007年 | 101篇 |
2006年 | 91篇 |
2005年 | 84篇 |
2004年 | 76篇 |
2003年 | 67篇 |
2002年 | 67篇 |
2001年 | 58篇 |
2000年 | 40篇 |
1999年 | 49篇 |
1998年 | 181篇 |
1997年 | 103篇 |
1996年 | 81篇 |
1995年 | 70篇 |
1994年 | 57篇 |
1993年 | 38篇 |
1992年 | 28篇 |
1991年 | 28篇 |
1990年 | 35篇 |
1989年 | 33篇 |
1988年 | 20篇 |
1987年 | 17篇 |
1986年 | 14篇 |
1985年 | 19篇 |
1984年 | 16篇 |
1983年 | 15篇 |
1982年 | 15篇 |
1981年 | 23篇 |
1980年 | 18篇 |
1979年 | 17篇 |
1978年 | 14篇 |
1977年 | 14篇 |
1976年 | 13篇 |
1975年 | 6篇 |
1973年 | 4篇 |
排序方式: 共有2565条查询结果,搜索用时 15 毫秒
11.
Tatsuhide Hayashi Masaki Asakura Mayu Kawase Masakazu Matsubara Yasuaki Uematsu Akimichi Mieki Tatsushi Kawai 《International journal of molecular sciences》2022,23(13)
This study aimed to induce bone-like tissue from immature muscular tissue (IMT) in vitro using commercially available recombinant human bone morphogenetic protein (rhBMP)-2, rhBMP-4, and rhBMP-7, and then implanting this tissue into a calvarial defect in rats to assess healing. IMTs were extracted from 20-day-old Sprague-Dawley (SD) fetal rats, placed on expanded polytetrafluoroethylene (ePTFE) with 10 ng/μL each of rhBMP-2, BMP-4, and BMP-7, and cultured for two weeks. The specimens were implanted into calvarial defects in 3-week-old SD rats for up to three weeks. Relatively strong radiopacity was observed on micro-CT two weeks after culture, and bone-like tissue, comprising osteoblastic cells and osteoids, was partially observed by H&E staining. Calcium, phosphorus, and oxygen were detected in the extracellular matrix using an electron probe micro analyzer, and X-ray diffraction patterns and Fourier transform infrared spectroscopy spectra of the specimen were found to have typical apatite crystal peaks and spectra, respectively. Furthermore, partial strong radiopacity and ossification were confirmed one week after implantation, and a dominant novel bone was observed after two weeks in the defect site. Thus, rhBMP-2, BMP-4, and BMP-7 differentiated IMT into bone-like tissue in vitro, and this induced bone-like tissue has ossification potential and promotes the healing of calvarial defects. Our results suggest that IMT is an effective tissue source for bone tissue engineering. 相似文献
12.
Minami Yamauchi Toshihiro Sato Ayana Otake Masaki Kumondai Yu Sato Masafumi Kikuchi Masamitsu Maekawa Hiroaki Yamaguchi Takaaki Abe Nariyasu Mano 《International journal of molecular sciences》2022,23(15)
Patients with liver diseases not only experience the adverse effects of liver-metabolized drugs, but also the unexpected adverse effects of renally excreted drugs. Bile acids alter the expression of renal drug transporters, however, the direct effects of bile acids on drug transport remain unknown. Renal drug transporter organic anion-transporting polypeptide 4C1 (OATP4C1) was reported to be inhibited by chenodeoxycholic acid. Therefore, we predicted that the inhibition of OATP4C1-mediated transport by bile acids might be a potential mechanism for the altered pharmacokinetics of renally excreted drugs. We screened 45 types of bile acids and calculated the IC50, Ki values, and bile acid–drug interaction (BDI) indices of bile acids whose inhibitory effect on OATP4C1 was >50%. From the screening results, lithocholic acid (LCA), glycine-conjugated lithocholic acid (GLCA), and taurine-conjugated lithocholic acid (TLCA) were newly identified as inhibitors of OATP4C1. Since the BDI index of LCA was 0.278, LCA is likely to inhibit OATP4C1-mediated transport in clinical settings. Our findings suggest that dose adjustment of renally excreted drugs may be required in patients with renal failure as well as in patients with hepatic failure. We believe that our findings provide essential information for drug development and safe drug treatment in clinics. 相似文献
13.
K. Kainosho M. Ohta M. Uchida M. Nakamura O. Oda 《Journal of Electronic Materials》1996,25(3):353-356
Recently, it was found that undoped semi-insulating InP can be obtained by highpressure annealing of high purity materials.
The reproducibility and the uniformity was, however, not satisfactory. In the present work, we found that not only Fe concentrations
but also Cr and Ni concentrations in annealed wafers were slightly increased during annealing. Since it seems that the origin
of the contamination was due to the vapor source of red phosphorus, conductive InP with a trace amount of Fe was annealed
under low phosphorus vapor pressure in order to reduce the contamination. By preventing the contamination of Cr and Ni, preparation
of semi-insulating InP became highly reproducible. The minimum Fe concentration for realizing semi-insulating InP was found
to be 1 x 1015cm−3. It was also found that the better resistivity uniformity can be obtained at higher annealing temperatures. 相似文献
14.
Hashimoto A Mitsuishi K Shimojo M Zhu Y Takeguchi M 《Journal of electron microscopy》2011,60(3):227-234
We experimentally examined the characteristics of bright-field (BF) scanning confocal electron microscopy (SCEM) images by changing the observation conditions and comparing the images with those obtained by BF transmission electron microscopy (TEM) and BF scanning TEM (STEM) modes. The observation of 5-nm-diameter Au nanoparticles demonstrated that BF-SCEM produces object elongation of more than 2000?nm along the optical axis, as do BF-TEM and BF-STEM. We demonstrated the relationship between elongation length and geometric effects such as convergence and collection angles of a probe and the lateral size of an object; the relationship is consistent with previous theoretical prediction. Further, we observed interesting features that are seen only in the BF-SCEM images; the film contrast was strongly enhanced, compared with that of BF-STEM. In addition, a bright contrast appeared around the object position in the elongated images. Using this characteristic, we could determine the object position and structure. 相似文献
15.
Krishnamohan T. Krivokapic Z. Uchida K. Nishi Y. Saraswat K.C. 《Electron Devices, IEEE Transactions on》2006,53(5):990-999
For the first time, the tradeoffs between higher mobility (smaller bandgap) channel and lower band-to-band tunneling (BTBT) leakage have been investigated. In particular, through detailed experiments and simulations, the transport and leakage in ultrathin (UT) strained germanium (Ge) MOSFETs on bulk and silicon-on-insulator (SOI) have been examined. In the case of strained Ge MOSFETs on bulk Si, the resulting optimal structure obtained was a UT low-defect 2-nm fully strained Ge epi channel on relaxed Si, with a 4-nm Si cap layer. The fabricated device shows very high mobility enhancements >3.5/spl times/ over bulk Si devices, 2/spl times/ mobility enhancement and >10/spl times/ BTBT reduction over 4-nm strained Ge, and surface channel 50% strained SiGe devices. Strained SiGe MOSFETs having UT (T/sub Ge/<3 nm) very high Ge fraction (/spl sim/ 80%) channel and Si cap (T/sub Si cap/<3 nm) have also been successfully fabricated on thin relaxed SOI substrates (T/sub SOI/=9 nm). The tradeoffs in obtaining a high-mobility (smaller bandgap) channel with low tunneling leakage on UT-SOI have been investigated in detail. The fabricated device shows very high mobility enhancements of >4/spl times/ over bulk Si devices, >2.5/spl times/ over strained silicon directly on insulator (SSDOI; strained to 20% relaxed SiGe) devices, and >1.5/spl times/ over 60% strained SiGe (on relaxed bulk Si) devices. 相似文献
16.
Yoshihiro Konishi Masaki Ishibashi Naoya Baba Eiji Hiraki Mutsuo Nakaoka 《International Journal of Electronics》2013,100(10):1295-1310
This paper presents a novel prototype of three-phase current-fed PWM converter with a switched capacitor type resonant dc link snubber circuit, which can basically operate under a principle of zero current soft switching commutation. The optimum PWM pattern-based control scheme proposed by the authors is effectively applied for this active converter. In this paper, the steady-state operating principle of a new converter circuit treated here is described. The practical design procedure of this converter is discussed from a theoretical point of view. The feasible experiment to confirm zero current soft switching commutation of this converter is concretely implemented and evaluated herein. 相似文献
17.
Nakamura K. Takeda K. Toyoshima H. Noda K. Ohkubo H. Uchida T. Shimizu T. Itani T. Tokashiki K. Kishimoto K. 《Solid-State Circuits, IEEE Journal of》1997,32(11):1758-1765
A 32-b 500-MHz 4-1-1-1 operation 4-Mb pipeline burst cache SRAM has been developed. In order to achieve both high bandwidth operation and short latency operation, we developed the following technologies: 1) a prefetched pipeline-burst scheme with double late-write buffers, 2) gate size reduction and a bit-line equalization by source resetting, 3) point-to-point bidirectional coding I/O's to reduce bus noise and power consumption, and 4) a three-level metal 0.25-μm CMOS process technology with six transistor memory cells 相似文献
18.
Keishi Sakamoto Atsushi Kasugai Masaki Tsuneoka Koji Takahashi Yukiharu Ikeda Tsuyoshi Imai Takashi Nagashima Mitsuru Ohta Tsuyoshi Kariya Kenichi Hayashi Yoshika Mitsunaka Yosuke Hirata Yasuyuki Itoh Yukio Okazaki 《Journal of Infrared, Millimeter and Terahertz Waves》1997,18(9):1637-1654
A development of 170GHz/500kW level gyrotron was carried out as R&D work of ITER. The oscillation mode is TE31,8. In a short pulse experiment, the maximum power of 750kW was achieved at 85kV/40A. The efficiency was 22%. In the depressed collector operation, 500kW/36%/50ms was obtained. The maximum efficiency of 40% was obtained at PRF=470kW whereas the power decrease by the electron trapping was observed. Pulse extension was done up to 10s at PRF=170kW with the depressed collector operation. The power was limited by the temperature increase of the output window. 相似文献
19.
Noda K. Tatsumi T. Uchida T. Nakajima K. Miyamoto H. Chenming Hu 《Electron Devices, IEEE Transactions on》1998,45(4):809-814
A simple fabrication technology for delta-doped MOSFETs, named post-low-energy implanting selective epitaxy (PLISE) is presented. The PLISE technology needs no additional photo-lithography mask, deposition step or etching step even for CMOS devices. The only additional step is growing undoped epitaxial channel layers by UHV-CVD after the channel implantation. With this technology, delta-doped NMOSFETs with 0.1-μm gate length were successfully fabricated. By optimizing the epi-layer thickness and the channel doping level, short-channel effects are suppressed enough to achieve 0.1-μm gate length. Moreover, the junction capacitance at zero bias is reduced by 50% 相似文献
20.
Uniformity of deep levels in semi-insulating InP obtained by multiple-step wafer annealing 总被引:1,自引:0,他引:1
K. Kuriyama K. Ushiyama T. Tsunoda M. Uchida K. Yokoyama 《Journal of Electronic Materials》1998,27(5):462-465
The uniformity of deep levels in semi-insulating InP wafers, which have been obtained by multiple-step wafer annealing under
phosphorus vapor pressure, was studied using the thermally stimulated current (TSC) and photoluminescence (PL) methods. Only
three traps related to Fe, T0 (ionization energy Ei=0.19 eV), T1 (0.25 eV), and T2 (0.33 eV), probably forming complex defects, were observed in the wafer and they exhibited a relatively uniform distribution.
PL spectra relating to phosphorus vacancies observed in some regions of the wafer are correlated with a small TSC signal having
an ionization energy of 0.43 eV. 相似文献