首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   1329篇
  免费   14篇
  国内免费   1篇
电工技术   63篇
综合类   4篇
化学工业   294篇
金属工艺   29篇
机械仪表   21篇
建筑科学   14篇
矿业工程   2篇
能源动力   38篇
轻工业   116篇
水利工程   11篇
石油天然气   3篇
无线电   91篇
一般工业技术   212篇
冶金工业   287篇
原子能技术   40篇
自动化技术   119篇
  2023年   8篇
  2022年   15篇
  2021年   20篇
  2020年   10篇
  2019年   17篇
  2018年   16篇
  2017年   19篇
  2016年   20篇
  2015年   12篇
  2014年   25篇
  2013年   65篇
  2012年   53篇
  2011年   57篇
  2010年   44篇
  2009年   43篇
  2008年   61篇
  2007年   43篇
  2006年   58篇
  2005年   45篇
  2004年   36篇
  2003年   44篇
  2002年   38篇
  2001年   27篇
  2000年   32篇
  1999年   34篇
  1998年   114篇
  1997年   63篇
  1996年   54篇
  1995年   39篇
  1994年   37篇
  1993年   31篇
  1992年   8篇
  1991年   12篇
  1990年   11篇
  1989年   6篇
  1988年   8篇
  1987年   10篇
  1986年   7篇
  1985年   8篇
  1984年   7篇
  1983年   13篇
  1982年   5篇
  1981年   7篇
  1980年   7篇
  1979年   8篇
  1978年   8篇
  1977年   8篇
  1976年   12篇
  1973年   3篇
  1970年   3篇
排序方式: 共有1344条查询结果,搜索用时 15 毫秒
121.
The possibility of near infrared (NIR) spectroscopy to measure the amount of bacterial contamination in shredded cabbage was investigated. NIR measurements in the short wavelength region from 700 to 1100 nm were done using two types of saline solutions: one was used to stomach with the samples as the conventional method and the other was used to wash the outer surface of the sample to examine the possibility of a non‐destructive method. Partial least squares regression (PLS) was used to develop the equations for bacterial amount. Spectra from the stomacher solution and the washing solution produced similar results. Sufficiently accurate results could be obtained with the bias‐corrected standard error of prediction (SEPs) of 0.46 log CFU g?1 for the stomacher solution and 0.44 log CFU g?1 for the washing solution. NIR spectroscopy was clarified to be a rapid and non‐destructive method for prediction of bacterial contamination in shredded cabbage.  相似文献   
122.
Under stress conditions, transfer RNAs (tRNAs) are cleaved by stress-responsive RNases such as angiogenin, generating tRNA-derived RNAs called tiRNAs. As tiRNAs contribute to cytoprotection through inhibition of translation and prevention of apoptosis, the regulation of tiRNA production is critical for cellular stress response. Here, we show that RTCB ligase complex (RTCB-LC), an RNA ligase complex involved in endoplasmic reticulum (ER) stress response and precursor tRNA splicing, negatively regulates stress-induced tiRNA production. Knockdown of RTCB significantly increased stress-induced tiRNA production, suggesting that RTCB-LC negatively regulates tiRNA production. Gel-purified tiRNAs were repaired to full-length tRNAs by RtcB in vitro, suggesting that RTCB-LC can generate full length tRNAs from tiRNAs. As RTCB-LC is inhibited under oxidative stress, we further investigated whether tiRNA production is promoted through the inhibition of RTCB-LC under oxidative stress. Although hydrogen peroxide (H2O2) itself did not induce tiRNA production, it rapidly boosted tiRNA production under the condition where stress-responsive RNases are activated. We propose a model of stress-induced tiRNA production consisting of two factors, a trigger and booster. This RTCB-LC-mediated boosting mechanism may contribute to the effective stress response in the cell.  相似文献   
123.
Membrane proteins play important roles in biological functions, with accompanying allosteric structure changes. Understanding intramolecular dynamics helps elucidate catalytic mechanisms and develop new drugs. In contrast to the various technologies for structural analysis, methods for analyzing intramolecular dynamics are limited. Single-molecule measurements using optical microscopy have been widely used for kinetic analysis. Recently, improvements in detectors and image analysis technology have made it possible to use single-molecule determination methods using X-rays and electron beams, such as diffracted X-ray tracking (DXT), X-ray free electron laser (XFEL) imaging, and cryo-electron microscopy (cryo-EM). High-speed atomic force microscopy (HS-AFM) is a scanning probe microscope that can capture the structural dynamics of biomolecules in real time at the single-molecule level. Time-resolved techniques also facilitate an understanding of real-time intramolecular processes during chemical reactions. In this review, recent advances in membrane protein dynamics visualization techniques were presented.  相似文献   
124.
Mitochonic Acid 5 (MA-5) enhances mitochondrial ATP production, restores fibroblasts from mitochondrial disease patients and extends the lifespan of the disease model “Mitomouse”. Additionally, MA-5 interacts with mitofilin and modulates the mitochondrial inner membrane organizing system (MINOS) in mammalian cultured cells. Here, we used the nematode Caenorhabditis elegans to investigate whether MA-5 improves the Duchenne muscular dystrophy (DMD) model. Firstly, we confirmed the efficient penetration of MA-5 in the mitochondria of C. elegans. MA-5 also alleviated symptoms such as movement decline, muscular tone, mitochondrial fragmentation and Ca2+ accumulation of the DMD model. To assess the effect of MA-5 on mitochondria perturbation, we employed a low concentration of rotenone with or without MA-5. MA-5 significantly suppressed rotenone-induced mitochondria reactive oxygen species (ROS) increase, mitochondrial network fragmentation and nuclear destruction in body wall muscles as well as endogenous ATP levels decline. In addition, MA-5 suppressed rotenone-induced degeneration of dopaminergic cephalic (CEP) neurons seen in the Parkinson’s disease (PD) model. Furthermore, the application of MA-5 reduced mitochondrial swelling due to the immt-1 null mutation. These results indicate that MA-5 has broad mitochondrial homing and MINOS stabilizing activity in metazoans and may be a therapeutic agent for these by ameliorating mitochondrial dysfunction in DMD and PD.  相似文献   
125.
The objective of this study is to produce and test the hybrid valve-regulated Ultrabattery designed specifically for hybrid-electric vehicle duty, i.e., high-rate partial-state-of-charge operation. The Ultrabattery developed by CSIRO Energy Technology is a hybrid energy-storage device, which combines an asymmetric supercapacitor, and a lead-acid battery in one unit cells, taking the best from both technologies without the need for extra, expensive electronic controls. The capacitor will enhance the power and lifespan of the lead-acid battery as it acts as a buffer during high-rate discharging and charging. Consequently, this hybrid technology is able to provide and absorb charge rapidly during vehicle acceleration and braking. The work programme of this study is divided into two main parts, namely, field trial of prototype Ultrabatteries in a Honda Insight HEV and laboratory tests of prototype batteries. In this paper, the performance of prototype Ultrabatteries under different laboratory tests is reported.  相似文献   
126.
This authors present the effect of Al inclusion in HfO/sub 2/ on the crystallization temperature, leakage current, band gap, dielectric constant, and border traps. It has been found that the crystallization temperature is significantly increased by adding Al into the HfO/sub 2/ film. With an addition of 31.7% Al, the crystallization temperature is about 400-500/spl deg/C higher than that without Al. This additional Al also results an increase of the band gap of the dielectric from 5.8 eV for HfO/sub 2/ without Al to 6.5 eV for HfAlO with 45.5% Al and a reduced dielectric constant from 19.6 for HfO/sub 2/ without Al to 7.4 for Al/sub 2/O/sub 3/ without Hf. Considering the tradeoff among the crystallization temperature, band gap, and dielectric constant, we have concluded that the optimum Al concentration is about 30% for conventional self-aligned CMOS gate processing technology.  相似文献   
127.
We calculate the thermal conductivity of solid 3 He in U2D2 phase. In this system, magnons are the dominant heat carriers. The experiment by Feng et al. shows that scattering magnon by some kind of magnetic defects becomes important at low temperature. We suppose the defects are the magnetic plane defects (MPD) which are originated by lattice dislocation and calculate the thermal conductivity with Kapitza Resistance Model (KRM).  相似文献   
128.
Development of morphological structures during phase separation induced by radical polymerization of 2-chlorostyrene in the presence of polystyrene was studied with an electron microscope. No stirring of the mixture was made. Domain structure changed significantly with initial monomer composition within a narrow range. Salami domains similar to those observed in high-impact polystyrene (HIPS) formed at certain initial compositions, notwithstanding that production of graft polymers, which was known to play an essential role of the salami structure formation in HIPS, was negligible in this system. An explanation for the mechanism of salami pattern formation was proposed.  相似文献   
129.
An optimized single-pole double-throw (SPDT) transmit/receive (T/R) switch has been fabricated using depletion-layer-extended transistors (DETs) in a 0.18 /spl mu/m CMOS process. The switch features the highest performance to date of any switch using a CMOS process, of a 0.8 dB insertion-loss, 23 dB isolation and 17.4 dBm power-handling capability at 5 GHz. The low insertion-loss has been achieved with the effects of junction capacitance decrease and substrate resistance increase in the DET, the adoption of low-loss shielded-pads, and several layout optimizations. The high power-handling capability is owing to the combined effect of the adoption of the source/drain dc biasing scheme and the high substrate resistance in the DET.  相似文献   
130.
The present report describes the improved transformation of the 17-oxo group in 3 beta-acetoxy-5 alpha-androstan-17-one to a 17 alpha-hydroxy group. A mixture of 17 alpha-acetoxy and 16-ene compounds, which are usually produced by the standard synthetic route, were treated with peracetic acid (epoxidation of the 16-ene compound) and then sodium borohydride-sodium hydroxide (reduction-hydrolysis) to give the desired 17 alpha-hydroxy compound in much better yield than that in previous reports. Recrystallization of the crude product with cyclohexane-methanol gave the pure compound in 54% yield (total yield from starting ketone).  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号