全文获取类型
收费全文 | 5386篇 |
免费 | 110篇 |
国内免费 | 8篇 |
专业分类
电工技术 | 276篇 |
综合类 | 10篇 |
化学工业 | 1032篇 |
金属工艺 | 126篇 |
机械仪表 | 103篇 |
建筑科学 | 89篇 |
能源动力 | 156篇 |
轻工业 | 376篇 |
水利工程 | 15篇 |
石油天然气 | 4篇 |
无线电 | 553篇 |
一般工业技术 | 878篇 |
冶金工业 | 1407篇 |
原子能技术 | 137篇 |
自动化技术 | 342篇 |
出版年
2023年 | 30篇 |
2022年 | 57篇 |
2021年 | 89篇 |
2020年 | 37篇 |
2019年 | 67篇 |
2018年 | 66篇 |
2017年 | 38篇 |
2016年 | 75篇 |
2015年 | 75篇 |
2014年 | 88篇 |
2013年 | 202篇 |
2012年 | 173篇 |
2011年 | 220篇 |
2010年 | 174篇 |
2009年 | 168篇 |
2008年 | 187篇 |
2007年 | 163篇 |
2006年 | 167篇 |
2005年 | 124篇 |
2004年 | 127篇 |
2003年 | 150篇 |
2002年 | 106篇 |
2001年 | 124篇 |
2000年 | 102篇 |
1999年 | 156篇 |
1998年 | 544篇 |
1997年 | 365篇 |
1996年 | 262篇 |
1995年 | 152篇 |
1994年 | 142篇 |
1993年 | 139篇 |
1992年 | 76篇 |
1991年 | 69篇 |
1990年 | 71篇 |
1989年 | 66篇 |
1988年 | 64篇 |
1987年 | 44篇 |
1986年 | 62篇 |
1985年 | 47篇 |
1984年 | 54篇 |
1983年 | 36篇 |
1982年 | 46篇 |
1981年 | 36篇 |
1980年 | 38篇 |
1979年 | 34篇 |
1978年 | 24篇 |
1977年 | 35篇 |
1976年 | 44篇 |
1975年 | 16篇 |
1973年 | 22篇 |
排序方式: 共有5504条查询结果,搜索用时 15 毫秒
91.
Liang Y Nakamura S Cui L Johkura K Ogiwara N Sasaki K 《Journal of electron microscopy》2004,53(1):93-97
Three-dimensional microlocalization of adhesion molecules, i.e. ICAM-1 (intercellular adhesion molecule), VCAM-1 (vascular adhesion molecule), LFA-1 (lymphocyte function-associated antigen), Mac-1 (macrophage differentiation antigen) and VLA-4 (very late activation antigen), expressed on type-A synoviocyte (macrophage-like cell) and type-B synoviocyte (fibroblast-like cell), were detected by immuno-scanning electron microscopy (SEM) to investigate the immunoreactive microenvironment of the superficial synovial intima in lipopolysaccharide (LPS)-induced arthritis of the mouse knee. Type-B synoviocytes extended rich slender processes from the periphery and constructed a cytoplasmic network, to which ICAM-1 was restricted. VCAM-1 was expressed only in the LPS-stimulated group and was relatively limited to the microvilli of type-B synoviocytes. Type-A synoviocytes were located randomly among the network with a smoother surface and expressed Mac-1 and LFA-1, which were counter-receptors for ICAM-1, and VLA-4 for VCAM-1 on the microvilli or lamellipodia. Three-dimensional microlocalization of adhesion molecules suggests that the network constructed by cytoplasmic processes and microvilli of type-B synoviocytes forms the pathway for the migration or the foothold for the fixation of type-A synoviocytes and takes part in forming an immunoreactive environment in the articular cavity. 相似文献
92.
Fujiyoshi T. Shiratake S. Nomura S. Nishikawa T. Kitasho Y. Arakida H. Okuda Y. Tsuboi Y. Hamada M. Hara H. Fujita T. Hatori F. Shimazawa T. Yahagi K. Takeda H. Murakata M. Minami F. Kawabe N. Kitahara T. Seta K. Takahashi M. Oowaki Y. Furuyama T. 《Solid-State Circuits, IEEE Journal of》2006,41(1):54-62
A single-chip H.264 and MPEG-4 audio-visual LSI for mobile applications including terrestrial digital broadcasting system (ISDB-T / DVB-H) with a module-wise, dynamic voltage/frequency scaling architecture is presented for the first time. This LSI can keep operating even during the voltage/frequency transition, so there is no performance overhead. It is realized through a dynamic deskewing system and an on-chip voltage regulator with slew rate control. By the combination with traditional low power techniques such as embedded DRAM and clock gating, it consumes only 63 mW in decoding QVGA H.264 video at 15 frames/sec and MPEG-4 AAC LC audio simultaneously. 相似文献
93.
3D Micromolding of Arrayed Waveguide Gratings on Upconversion Luminescent Layers for Flexible Transparent Displays without Mirrors,Electrodes, and Electric Circuits 下载免费PDF全文
Satoshi Watanabe Takeo Asanuma Takafumi Sasahara Hiroshi Hyodo Mutsuyoshi Matsumoto Kohei Soga 《Advanced functional materials》2015,25(28):4390-4396
A new technique for the fabrication of arrayed waveguide gratings on upconversion luminescent layers for flexible transparent displays is reported. Ho3+‐ and Yb3+‐codoped NaYF4 nanoparticles are synthesized by hydrothermal techniques. Transparent films consisting of two transparent polymers on the NaYF4 nanoparticle films exhibit mechanical flexibility and high transparence in visible region. Patterned NaYF4 nanoparticle films are fabricated by calcination‐free micromolding in capillaries. Arrayed waveguide gratings consisting of the two transparent polymers are formed on the patterned NaYF4 nanoparticle films by micromolding in capillaries. Green and red luminescence is observed from the upconversion luminescent layers of the NaYF4 nanoparticle films in the arrayed waveguide gratings under excitation at 980 nm laser light. Arrayed waveguide gratings on the upconversion luminescent layers are fabricated with Er3+‐doped NaYF4 nanoparticles which can convert two photons at 850 and 1500 nm into single photon at 550 nm. These results demonstrate that flexible transparent displays can be fabricated by constructing arrayed waveguide gratings on upconversion luminescent layers, which can operate in nonprojection mode without mirrors, transparent electrodes, and electric circuits. 相似文献
94.
Flexible Electronics: 3D Micromolding of Arrayed Waveguide Gratings on Upconversion Luminescent Layers for Flexible Transparent Displays without Mirrors,Electrodes, and Electric Circuits (Adv. Funct. Mater. 28/2015) 下载免费PDF全文
95.
J. Kannisto T. Takahashi J. Harju S. Heikkinen M. Helenius S. Matsuo B. Silverajan 《International Journal of Communication Systems》2015,28(15):2067-2081
Security service level agreements (SSLAs) provide a systematic way for end users at home or in the office to guarantee sufficient security level when doing business or exchanging sensitive personal or organizational data with an online service. In this paper, we propose an SSLA negotiation protocol that implements non‐repudiation with cryptographic identities and digital signatures and includes features that make it resistant to denial of service attacks. The basic version of the protocol does not rely on the use of a trusted third party, and it can be used for all kinds of simple negotiations. For the negotiation about SSLAs, the protocol provides an option to use an external knowledge base that may help the user in the selection of suitable security measures. We have implemented a prototype of the system, which uses JSON Web Signature for the message exchange and made some performance tests with it. The results show that the computational effort required by the cryptographic operations of the negotiation protocol remains at a reasonable level. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
96.
Atsushi Nakanishi Takashi Yasuda Kazuki Horita Hironori Takahashi 《Journal of Infrared, Millimeter and Terahertz Waves》2018,39(1):36-44
We measured the thermal dependencies of the refractive index and the absorption coefficient of high-resistivity silicon. We found that the refractive index varied slightly with temperature, and the absorption coefficient was very low and remained approximately constant as the temperature was changed. As a result, the conditions for terahertz propagation in silicon could be controlled by changing the refractive index without any absorption loss. As one application of this effect, we developed a terahertz time delay generator that can generate a terahertz time delay by changing the temperature of the medium through which the terahertz beam passes, without the need for any mechanical delay. We demonstrated generation of a terahertz time delay of approximately 6.6 ps. 相似文献
97.
Kawano M. Takahashi N. Kurita Y. Soejima K. Komuro M. Matsui S. 《Electron Devices, IEEE Transactions on》2008,55(7):1614-1620
A 3-D packaging technology is developed for stacked dynamic random access memory (DRAM) with through-silicon vias (TSVs). Eight different dry etchers were evaluated for deep Si etching. Highly doped poly-Si TSVs were used for vertical traces inside silicon and interconnection between DRAM chips to realize a DRAM-compatible process. Through optimization of process conditions and layout design, a fast poly-Si filling has been obtained. The entire packaging was carried out at the wafer level by using smart chip connection with feedthrough interposer (FTI) technology. A new bump and wiring structure for the FTI has also been developed for fine-pitch and low-cost bonding. Normal operation during DRAM read/write was confirmed on a 512-Mb DRAM with TSVs, with an I/F chip as a memory controller. Simulation and measurement of the transfer function of the FTI wiring showed a 3-Gb/s/pin data transfer capability. 相似文献
98.
As the density and operating speed of complementary metal oxide semiconductor (CMOS) circuits increases, dynamic power dissipation has become a critical concern in the design and development—of personal information systems and large computers. The reduction of supply voltage, node capacitance, and switching activity are common approaches used in conventional CMOS. In adiabatic switching circuits, the current flow through transistors can be significantly reduced by ensuring uniform charge transfer over the entire available time. This paper presents the simulation of this current in two-phase clocked adiabatic static CMOS logic (2PASCL) and conventional CMOS. From the SPICE simulations, at transition frequencies from 1 to 12 MHz, a 4×4-bit array 2PASCL multiplier shows a maximum reduction in power dissipation of 77% relative to that of a static CMOS. The measurement results of a 4×4-bit array 2PASCL multiplier demonstrate a 57% reduction compared to a 4×4-bit array two-phase clocked adiabatic dynamic CMOS logic (2PADCL). These results indicate that 2PASCL technology can be advantageous when applied to low-power digital devices operated at low frequencies, such as radio-frequency identification (RFID) tags, smart cards, and sensors. 相似文献
99.
Shuich Fujii Yuko Fukawa Hiroaki Takahashi Yosuke Inomata Kenichi Okada Kenji Fukui Katsuhiko Shirasawa 《Solar Energy Materials & Solar Cells》2001,65(1-4)
In 1996 a conversion efficiency of 17.1% had been obtained on 15 cm×15 cm mc-Si solar cell. In this paper, large-scale production technology of the high-efficiency processing will be discussed. Enlarging reactive ion etching (RIE) equipment size, technology of passivation, and fine contact grid with low resistance by screenprinted metallization, which is firing through PECVD SiN, have been investigated. 相似文献
100.
Chinone N. Kuroda T. Ohtoshi T. Takahashi T. Kajimura T. 《Quantum Electronics, IEEE Journal of》1985,21(8):1264-1270
Mode-hopping noise in index-guided semiconductor lasers is investigated. It is found that random switching between lasing modes and output power differences in those modes cause mode-hopping noise. An effective method to suppress such mode-hopping noise is proposed. High Te doping to an n-type GaAlAs cladding layer completely suppresses the noise. Te in GaAlAs forms a DX center that acts as a saturable absorber. This property stabilizes the laser mode and prevents mode competition. The minimum loss difference between lasing and nonlasing modes to suppress mode-hopping noise is also discussed. 相似文献