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   2273篇
  免费   116篇
  国内免费   32篇
电工技术   40篇
综合类   8篇
化学工业   609篇
金属工艺   67篇
机械仪表   90篇
建筑科学   91篇
矿业工程   17篇
能源动力   149篇
轻工业   165篇
水利工程   29篇
石油天然气   68篇
无线电   198篇
一般工业技术   445篇
冶金工业   83篇
原子能技术   16篇
自动化技术   346篇
  2024年   4篇
  2023年   39篇
  2022年   91篇
  2021年   136篇
  2020年   101篇
  2019年   138篇
  2018年   203篇
  2017年   139篇
  2016年   147篇
  2015年   87篇
  2014年   120篇
  2013年   262篇
  2012年   144篇
  2011年   150篇
  2010年   117篇
  2009年   108篇
  2008年   58篇
  2007年   42篇
  2006年   42篇
  2005年   25篇
  2004年   21篇
  2003年   18篇
  2002年   24篇
  2001年   13篇
  2000年   6篇
  1999年   7篇
  1998年   16篇
  1997年   10篇
  1996年   3篇
  1995年   17篇
  1994年   7篇
  1993年   9篇
  1992年   12篇
  1991年   12篇
  1990年   8篇
  1989年   4篇
  1988年   6篇
  1987年   4篇
  1986年   3篇
  1985年   9篇
  1983年   6篇
  1982年   3篇
  1981年   7篇
  1980年   3篇
  1979年   7篇
  1978年   3篇
  1976年   7篇
  1975年   7篇
  1974年   8篇
  1973年   4篇
排序方式: 共有2421条查询结果,搜索用时 15 毫秒
1.
The stoichiometric association constants, K, the thermodynamic association constant, KA, and the other thermodynamic parameters such as ΔS°, ΔH° and ΔG° for the association between each of the Ca and Mg ions with benzoate, o-toloate, o-chlorobenzoate and salycylate have been determined at 25°C, 35°C and 45°C in aqueous media. Ion-selective electrode technique has been used in the measurements of Ca and Mg ion activitiesThe trend of association behavior of both Ca and Mg aromatic salts could not be explained on the basis of pKa of the mother organic acids but could be explained based on the trend of Hammet function σ of these salts themselves relative to the corresponding benzoate salt.  相似文献   
2.
Pattern Analysis and Applications - Coronavirus (COVID-19) is one of the most serious problems that has caused stopping the wheel of life all over the world. It is widely spread to the extent that...  相似文献   
3.
4.
The Journal of Supercomputing - On the battlefield, early detection of armored vehicles can have a positive effect. Because according to this issue, timely and appropriate reactions can be done....  相似文献   
5.
Real-world data collected for computer-based applications are frequently impure. Differentiation of outliers and noisy data from normal ones is a major task in data mining applications. On the other hand, elimination of noisy and outlier data from training samples of a dataset may lead to over-fitting or information loss. A fuzzy support vector machine (FSVM) provides an effective means to deal with this problem. It reduces the effect of the noisy data and outliers by using a fuzzy membership functions. In this paper, a new formation for SVMs is introduced that considers importance degrees for training samples. The constraints of the SVM are converted to fuzzy inequalities. The proposed method, RSVM, shows better efficiency in the classification of data in different domains. Especially, using the proposed RSVM for multi-class classification of arrhythmia disease is presented at the end of this paper as a practical case study to show the effectiveness of the proposed system.  相似文献   
6.
Plants have various self-defense mechanisms against biotic attacks, involving both physical and chemical barriers. Physical barriers include spines, trichomes, and cuticle layers, whereas chemical barriers include secondary metabolites (SMs) and volatile organic compounds (VOCs). Complex interactions between plants and herbivores occur. Plant responses to insect herbivory begin with the perception of physical stimuli, chemical compounds (orally secreted by insects and herbivore-induced VOCs) during feeding. Plant cell membranes then generate ion fluxes that create differences in plasma membrane potential (Vm), which provokes the initiation of signal transduction, the activation of various hormones (e.g., jasmonic acid, salicylic acid, and ethylene), and the release of VOCs and SMs. This review of recent studies of plant–herbivore–infection interactions focuses on early and late plant responses, including physical barriers, signal transduction, SM production as well as epigenetic regulation, and phytohormone responses.  相似文献   
7.
AIM: Mild heat stress can improve mitochondrial respiratory capacity in skeletal muscle. However, long-term heat interventions are scarce, and the effects of heat therapy need to be understood in the context of the adaptations which follow the more complex combination of stimuli from exercise training. The purpose of this work was to compare the effects of 6 weeks of localized heat therapy on human skeletal muscle mitochondria to single-leg interval training. METHODS: Thirty-five subjects were assigned to receive sham therapy, short-wave diathermy heat therapy, or single-leg interval exercise training, localized to the quadriceps muscles of the right leg. All interventions took place 3 times per week. Muscle biopsies were performed at baseline, and after 3 and 6 weeks of intervention. Mitochondrial respiratory capacity was assessed on permeabilized muscle fibers via high-resolution respirometry. RESULTS: The primary finding of this work was that heat therapy and exercise training significantly improved mitochondrial respiratory capacity by 24.8 ± 6.2% and 27.9 ± 8.7%, respectively (p < 0.05). Fatty acid oxidation and citrate synthase activity were also increased following exercise training by 29.5 ± 6.8% and 19.0 ± 7.4%, respectively (p < 0.05). However, contrary to our hypothesis, heat therapy did not increase fatty acid oxidation or citrate synthase activity. CONCLUSION: Six weeks of muscle-localized heat therapy significantly improves mitochondrial respiratory capacity, comparable to exercise training. However, unlike exercise, heat does not improve fatty acid oxidation capacity.  相似文献   
8.
As a new field of oxidative stress-based therapy, cold physical plasma is a promising tool for several biomedical applications due to its potential to create a broad diversity of reactive oxygen and nitrogen species (RONS). Although proposed, the impact of plasma-derived RONS on the cell membrane lipids and properties is not fully understood. For this purpose, the changes in the lipid bilayer functionality under oxidative stress generated by an argon plasma jet (kINPen) were investigated by electrochemical techniques. In addition, liquid chromatography-tandem mass spectrometry was employed to analyze the plasma-induced modifications on the model lipids. Various asymmetric bilayers mimicking the structure and properties of the erythrocyte cell membrane were transferred onto a gold electrode surface by Langmuir-Blodgett/Langmuir-Schaefer deposition techniques. A strong impact of cholesterol on membrane permeabilization by plasma-derived species was revealed. Moreover, the maintenance of the barrier properties is influenced by the chemical composition of the head group. Mainly the head group size and its hydrogen bonding capacities are relevant, and phosphatidylcholines are significantly more susceptible than phosphatidylserines and other lipid classes, underlining the high relevance of this lipid class in membrane dynamics and cell physiology.  相似文献   
9.
5-Aryl-3-carboxymethylthio-1,2,4-triazoles 2 are cyclised to 6-arylthiazolo[3,2-b]-s-triazol-3(2H)-ones 3 . This structural assignment has been based on IR and NMR spectra. 2-Arylmethylene-6-arylthiazolo[3,2-b]-s-triazol-3(2H)-ones 7 were prepared by several methods. Compounds 3 coupled with diazotised anilines to give 2,3-dihydro-6-arylthiazolo[3,2-b]-s-triazole-2,3-dione 2-arylhydrazones 8 . The action of amines on 3a opens the thiazolone ring with the formation of substituted (5-phenyltriazol-3-ylthio)-acetamides 9 .  相似文献   
10.
A new time-based high-speed data-link architecture, which we call Differential time Signaling (DTS) is presented. A clock pulse is embedded in the transmitted signal and is used as a time reference against which the rising and falling data pulse edge timings are compared. Using the DTS approach, data encoding is achieved by spacing the time between the embedded clock edges and the data pulse edges using a hierarchical time-delay resolution assignment to each bit in the data sequence. The proposed link is shown to concentrate the signal energy in a low bandwidth while reducing clock jitter effect. A simulated 3 Gb/s 90 nm CMOS DTS link using a 500 MHz clock signal is also described to provide a flavor for a monolithic realization. As a proof of concept, 700 Mb/s and 1.6 Gb/s DTS-based links have been designed using a commercial FPGA board. The measured eye diagrams for the transmitted and received signals over a 40-inch FR4 channel are presented.  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