全文获取类型
收费全文 | 936篇 |
免费 | 24篇 |
国内免费 | 1篇 |
学科分类
工业技术 | 961篇 |
出版年
2023年 | 4篇 |
2022年 | 12篇 |
2021年 | 20篇 |
2020年 | 10篇 |
2019年 | 8篇 |
2018年 | 10篇 |
2017年 | 15篇 |
2016年 | 18篇 |
2015年 | 19篇 |
2014年 | 32篇 |
2013年 | 39篇 |
2012年 | 32篇 |
2011年 | 43篇 |
2010年 | 31篇 |
2009年 | 32篇 |
2008年 | 31篇 |
2007年 | 41篇 |
2006年 | 31篇 |
2005年 | 29篇 |
2004年 | 25篇 |
2003年 | 30篇 |
2002年 | 29篇 |
2001年 | 25篇 |
2000年 | 18篇 |
1999年 | 26篇 |
1998年 | 44篇 |
1997年 | 32篇 |
1996年 | 28篇 |
1995年 | 24篇 |
1994年 | 29篇 |
1993年 | 23篇 |
1992年 | 10篇 |
1991年 | 13篇 |
1990年 | 13篇 |
1989年 | 17篇 |
1988年 | 13篇 |
1987年 | 6篇 |
1986年 | 7篇 |
1985年 | 13篇 |
1984年 | 10篇 |
1983年 | 3篇 |
1982年 | 10篇 |
1981年 | 9篇 |
1980年 | 7篇 |
1979年 | 7篇 |
1978年 | 6篇 |
1977年 | 7篇 |
1976年 | 7篇 |
1975年 | 3篇 |
1974年 | 4篇 |
排序方式: 共有961条查询结果,搜索用时 15 毫秒
1.
2.
Manabu Iguchi Tsuneo Kondoh Keiji Nakajima 《Metallurgical and Materials Transactions B》1997,28(4):605-612
The establishment time of gas-liquid two-phase flows in a cylindrical bath agitated by bottom gas injection through a central
single-hole bottom nozzle was investigated. Because the turbulence intensity in the bath was comparable to or larger than
the unity, the conventional definition of the flow establishment time based on the history of mean velocity was not suitable
for the present case. In fact, it was difficult to determine the flow establishment time based on the well-known 90 or 99
pct criterion for the mean velocity. Accordingly, two methods of determining the flow establishment time by focusing on the
turbulence components instead of the mean velocity components were proposed. Velocity measurements were made with a two-channel
laser Doppler velocimeter. The flow establishment time was correlated as a function of gas flow rate. Close agreement was
obtained by the two methods. 相似文献
3.
K. Tsuzuki T. Banno A. Kinbara Y. Nakagawa T. Tsukada 《Journal of Nuclear Materials》1993,200(3):291-295
The self-bias potential (Vdc) induced on an RF-powdered electrode (153 mm Ø) in a plasma is measured using electrical probes which are buried in, de-insulated from, and RF-connected to the electrode. The configuration of the probes allows to study the distribution of Vdc discretely on the electrode. The potential is homogeneous in the absence of external magnetic field. In the presence of a homogeneous magnetic field parallel to the electrode, it is reduced and a monotonous gradient takes place in its distribution due to the plasma shift induced by E × B drift. When the magnetic field is rotated along the axis of the RF-electrode at a frequency less than 50 Hz, the distribution, which is almost identical to the one in a static field, rotates with the magnetic field. On the coordinate system rotating with the magnetic field, the probes are regarded to be rotating. The potential distribution is obtained as a continuous function of the azimuthal angle. Thus the rotation of the field provides information for the experimental interpolation. 相似文献
4.
5.
Toru Ikegami Hideyuki Negishi Dai Kitamoto Keiji Sakaki Tomohiro Imura Masayoshi Okamoto Yasushi Idemoto Nobuyuki Koura Tsuneji Sano Kenji Haraya Hiroshi Yanagishita 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2005,80(4):381-387
In order to produce highly concentrated bioethanol by pervaporation using an ethanol‐permselective silicalite membrane, techniques to suppress adsorption of succinic acid, which is a chief by‐product of ethanol fermentation and causes the deterioration in pervaporation performance, onto the silicalite crystals was investigated. The amount adsorbed increased as the pH of the aqueous succinic acid solution decreased. The pervaporation performance also decreased with decreasing pH when the ternary mixtures of ethanol/water/succinic acid were separated. Using silicalite membranes individually coated with two types of silicone rubber, pervaporation performance was significantly improved in the pH range of 5 to 7, when compared with that of non‐coated silicalite membranes in ternary mixtures of ethanol/water/succinic acid. Moreover, when using a silicalite membrane double‐coated with the two types of silicone rubber, pervaporation performance was stabilized at lower pH values. In the separation of bioethanol by pervaporation using the double‐coated silicalite membrane, removal of accumulated substances having an ultraviolet absorption maximum at approximately 260 nm from the fermentation broth proved to be vital for efficient pervaporation. Copyright © 2005 Society of Chemical Industry 相似文献
6.
Hida H. Tsukada Y. Ogawa Y. Toyoshima H. Fujii M. Shibahara K. Kohno M. Nozaki T. 《Electron Devices, IEEE Transactions on》1989,36(10):2223-2230
The authors describe a novel design concept for enhancement (E) and depletion (D) mode FET formation using i-AlGaAs/n-GaAs doped-channel hetero-MISFET (DMT) and a novel self-aligned gate process technology for submicrometer-gate DMT-LSIs based on E/D logic gates. 0.5-μm gate E-DMTs (D-DMTs) with a lightly doped drain (LDD) structure show an average V t of 0.18 (-0.46) V, a V t standard deviation of 22.6 (24.9) mV, and a maximum transconductance of 450 (300) mS/mm. The V t shift is less than 50 mV with a decrease in gate length down to 0.5 μm. The gate forward turn-on voltage V f is more than 0.9 V, i.e. about 1.6 times that for MESFETs. This superiority in V f, preserved in the high-temperature range, leads to an improvement in noise margin tolerance by a factor of three. In addition, 31-stage ring oscillators operate with a power consumption of 20 (1.0) mW/gate and a propagation delay of 4.8 (14.5) ps/gate. Circuit simulation based on the experimental data predicts 140 ps/gate and 1 mW/gate for DMT direct-coupled FET logic circuits under standard loading conditions. DMTs and the technology developed here are very attractive for realizing low-power and/or high speed LSIs 相似文献
7.
Keiji Itabashi Takuji Ikeda Akihiko Matsumoto Kunikazu Kamioka Masanao Kato Kazuo Tsutsumi 《Microporous and mesoporous materials》2008,114(1-3):495-506
Four types of Rb-aluminosilicate zeolites were hydrothermally synthesized in pure phase for the first time from Rb-aluminosilicate gels without using any organic structure-directing agent (SDA) under stirring conditions. The crystal structure of each zeolite was refined by Rietveld analysis of the X-ray diffraction (XRD) data. These crystal structures were confirmed to be Rb-mordenite, Rb-merlinoite, a new aluminosilicate zeolite with an ATT framework topology, and Rb-offretite denoted by RMA-1, RMA-2, RMA-3, and RMA-4, respectively. The Si/Al ratio of RMA-1 with an MOR topology varied from 5.3 to 8.0; however, the variation of the Si/Al ratios of the other zeolites was rather small. The crystal system of RMA-2 was tetragonal with space group I4/mmm, where two Rb sites were distributed at the center of an 8-membered ring (MR). On the other hand, two Rb sites in RMA-3 were located at the center of the 8-MR in small two cages. The structure of RMA-4 was identified as the OFF type with a local disorder or defect, which included a small amount of an intergrown ERI phase. 相似文献
8.
9.
Sean R. Tachibana Longteng Tang Liangdong Zhu Yuka Takeda Keiji Fushimi Yoshibumi Ueda Takahiro Nakajima Yuto Kuwasaki Moritoshi Sato Rei Narikawa Chong Fang 《International journal of molecular sciences》2021,22(10)
Cyanobacteriochromes (CBCRs) are promising optogenetic tools for their diverse absorption properties with a single compact cofactor-binding domain. We previously uncovered the ultrafast reversible photoswitching dynamics of a red/green photoreceptor AnPixJg2, which binds phycocyanobilin (PCB) that is unavailable in mammalian cells. Biliverdin (BV) is a mammalian cofactor with a similar structure to PCB but exhibits redder absorption. To improve the AnPixJg2 feasibility in mammalian applications, AnPixJg2_BV4 with only four mutations has been engineered to incorporate BV. Herein, we implemented femtosecond transient absorption (fs-TA) and ground state femtosecond stimulated Raman spectroscopy (GS-FSRS) to uncover transient electronic dynamics on molecular time scales and key structural motions responsible for the photoconversion of AnPixJg2_BV4 with PCB (Bpcb) and BV (Bbv) cofactors in comparison with the parent AnPixJg2 (Apcb). Bpcb adopts the same photoconversion scheme as Apcb, while BV4 mutations create a less bulky environment around the cofactor D ring that promotes a faster twist. The engineered Bbv employs a reversible clockwise/counterclockwise photoswitching that requires a two-step twist on ~5 and 35 picosecond (ps) time scales. The primary forward Pfr → Po transition displays equal amplitude weights between the two processes before reaching a conical intersection. In contrast, the primary reverse Po → Pfr transition shows a 2:1 weight ratio of the ~35 ps over 5 ps component, implying notable changes to the D-ring-twisting pathway. Moreover, we performed pre-resonance GS-FSRS and quantum calculations to identify the Bbv vibrational marker bands at ~659,797, and 1225 cm−1. These modes reveal a stronger H-bonding network around the BV cofactor A ring with BV4 mutations, corroborating the D-ring-dominant reversible photoswitching pathway in the excited state. Implementation of BV4 mutations in other PCB-binding GAF domains like AnPixJg4, AM1_1870g3, and NpF2164g5 could promote similar efficient reversible photoswitching for more directional bioimaging and optogenetic applications, and inspire other bioengineering advances. 相似文献
10.
Silk fibers and membranes were acylated with octadecenylsuccinic anhydride (ODSA) at 75°C for different times. Swelling [N,N‐dimethylformamide (DMF) and dimethyl sulfoxide (DMSO)] and nonswelling (xylene) solvent media were used for the reaction. Silk membranes that reacted in DMF or DMSO displayed faster reaction kinetics and attained higher weight‐gain values than fibers. The effect of the solvent on the reaction yield was in the following order: DMSO > DMF ? xylene. The Fourier transform infrared spectra of acylated silk samples showed the characteristic absorption bands of the anhydride at 2990, 2852, 1780–1700, and 1170 cm?1. The intensity of the latter band, which increased linearly with the weight gain, was used as a marker for evaluating the reaction kinetics of the samples acylated in the nonswelling medium. The moisture regain and water retention of silk fibers acylated with ODSA decreased significantly, regardless of the solvent system used. Accordingly, the water repellency increased. Acylation induced an increase in the thermal stability of the silk fibers and membranes. Fine particles adhering to the surfaces of the silk fibers acylated in xylene were detected by scanning electron microscopy. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 324–332, 2003 相似文献