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   6478篇
  免费   365篇
  国内免费   9篇
电工技术   54篇
综合类   13篇
化学工业   1690篇
金属工艺   193篇
机械仪表   145篇
建筑科学   264篇
矿业工程   13篇
能源动力   250篇
轻工业   919篇
水利工程   44篇
石油天然气   35篇
武器工业   2篇
无线电   360篇
一般工业技术   1085篇
冶金工业   687篇
原子能技术   69篇
自动化技术   1029篇
  2024年   16篇
  2023年   61篇
  2022年   140篇
  2021年   228篇
  2020年   147篇
  2019年   157篇
  2018年   238篇
  2017年   233篇
  2016年   252篇
  2015年   193篇
  2014年   267篇
  2013年   463篇
  2012年   401篇
  2011年   505篇
  2010年   364篇
  2009年   341篇
  2008年   331篇
  2007年   240篇
  2006年   245篇
  2005年   210篇
  2004年   153篇
  2003年   164篇
  2002年   150篇
  2001年   90篇
  2000年   84篇
  1999年   64篇
  1998年   195篇
  1997年   152篇
  1996年   93篇
  1995年   70篇
  1994年   64篇
  1993年   68篇
  1992年   28篇
  1991年   24篇
  1990年   24篇
  1989年   25篇
  1988年   22篇
  1987年   25篇
  1986年   20篇
  1985年   29篇
  1984年   18篇
  1983年   20篇
  1982年   19篇
  1981年   25篇
  1980年   18篇
  1979年   23篇
  1978年   16篇
  1977年   14篇
  1976年   34篇
  1971年   11篇
排序方式: 共有6852条查询结果,搜索用时 15 毫秒
991.
We studied the textural and rheological (viscoelastic) properties of fresh lafun dough, a fermented cassava product, and their changes during storage at 45 °C for 5 and 24 h, in order to determine after-cooking storability. Lafun flours were produced from three types of cassava varieties: seven improved white-fleshed varieties, seven improved provitamin A carotenoids (pVAC) varieties and two local white-fleshed varieties; and processed into lafun doughs. Pasting properties of the flours were assessed. Flours from local varieties had pasting profiles with highest viscosities, while pVAC flours had the lowest. The three types of cassava varieties varied significantly in most of their pasting properties. Four promising improved varieties were identified, based on high peak viscosity (55.8–61.5 P) and stiffer texture than local varieties during storage. Undesirable varieties were also found, which softened during storage instead of hardening. Optimum texture of lafun dough was obtained after 5 h of storage.  相似文献   
992.
A previous study showed that classical building-related symptoms (BRS) were related to indoor dust and microbial toxicity via boar sperm motility assay, a sensitive method for measuring mitochondrial toxicity. In this cross-sectional study, we analyzed whether teachers’ most common work-related non-literature-known BRS (nBRS) were also associated with dust or microbial toxicity. Teachers from 15 schools in Finland completed a questionnaire evaluating 20 nBRS including general, eye, respiratory, hearing, sleep, and mental symptoms. Boar sperm motility assay was used to measure the toxicity of extracts from wiped dust and microbial fallout samples collected from teachers’ classrooms. 231 teachers answered a questionnaire and their classroom toxicity data were recorded. A negative binomial mixed model showed that teachers’ work-related nBRS were 2.9-fold (95% CI: 1.2-7.3) higher in classrooms with highly toxic dust samples compared to classrooms with non-toxic dust samples (p = 0.024). The RR of work-related nBRS was 1.8 (95% CI: 1.1-2.9) for toxic microbial samples (p = 0.022). Teachers’ BRS appeared to be broader than reported in the literature, and the work-related nBRS were associated with toxic dusts and microbes in classrooms.  相似文献   
993.
994.
995.
In this study, the colorimetric parameters (L*, a*, b*) and mass loss of heat‐treated bamboo were investigated, and the obtained results were modeled by using two methods: multiple linear regression (MLR) and artificial neural network (ANN). First, bamboo samples were exposed to heat treatment at different temperatures (110°C, 140°C, 170°C, and 200°C) and durations (15, 30, 45, 60, 75, 90, and 115 minutes) in a laboratory oven. Then, the colorimetric parameters (L*, a*, b*) and mass loss of each sample were measured after each period of heat treatment. All data were modeled by using two methods separately for each parameter and the performances of these proposed methods were compared. It was found that color change and mass loss increased with increasing temperature and duration of heat treatment. Mean absolute percentage error (MAPE) values of all obtained MLR ranged from 0.64% to 10.63%, while the all MAPE values of ANN were found to be lower than 1.5%. Based on these results, it can be said that MLR and ANN could be used to evaluate the changes on the selected properties of heat‐treated bamboo samples. On the other hand, it should be emphasized that the ANN gave more accurate results than the MLR method because of its learning capability.  相似文献   
996.
Methyl-tri-n-butylammonium methylsulfate (BIL) was incorporated into acrylic resin to improve antistatic property of acrylic polymer (AP). In order to avoid reduction in the mechanical properties of acrylic film and to reach higher electrical conductivity values, the combination of graphite nanoplates (Gr) and BIL was used. The effects of incorporation of BIL and Gr into AP on UV-blocking properties and UV transmittance data of acrylic films were measured. After 120 days, AP containing 5 wt% BIL and 0.01 wt% Gr, and AP+15 wt% BIL exhibited antistatic property. While BIL incorporation into acrylic resin deteriorated the mechanical properties, 0.01 wt% Gr incorporation increased the tensile strength by 83%.  相似文献   
997.
Machine Learning - Dimensionality reduction and manifold learning methods such as t-distributed stochastic neighbor embedding (t-SNE) are frequently used to map high-dimensional data into a...  相似文献   
998.
The Journal of Supercomputing - As the distributed computing systems have been widely used in many research and industrial areas, the problem of allocating tasks to available processors in the...  相似文献   
999.
Calcium oxalate (CaOx) is the major phase in kidney stones and the primary calcium storage medium in plants. CaOx can form crystals with different lattice types, water contents, and crystal structures. However, the conditions and mechanisms leading to nucleation of particular CaOx crystals are unclear. Here, liquid-cell transmission electron microscopy and atomistic molecular dynamics simulations are used to study in situ CaOx nucleation at different conditions. The observations reveal that rhombohedral CaOx monohydrate (COM) can nucleate via a classical pathway, while square COM can nucleate via a non-classical multiphase pathway. Citrate, a kidney stone inhibitor, increases the solubility of calcium by forming calcium-citrate complexes and blocks oxalate ions from approaching calcium. The presence of multiple hydrated ionic species draws additional water molecules into nucleating CaOx dihydrate crystals. These findings reveal that by controlling the nucleation pathways one can determine the macroscale crystal structure, hydration state, and morphology of CaOx.  相似文献   
1000.
Electron emission characteristic, electrical conductivity of polycrystalline mayenite (12CaO·7Al2O3) electride, formation of [Ca24Al28O64]4+(e)4 framework as a function of phase content, and microstructure have been investigated. The mayenite microstructure was investigated using high-resolution transmission microscopy which revealed the type cage structure of 12CaO·7Al2O3 partially filled by extra-framework oxygen ions. Incorporation of electrons by means of carbon ion template 12CaO·7Al2O3 produces complex structure, and an incomplete ion template 12CaO·7Al2O3 structure consisting of mixture of a [Ca24Al28O64]4+(e)4 and [Ca24Al28O64]4+(O2−)2 framework had a direct effect on the electron emission. Surface chemistry and stability of the 12CaO·7Al2O3 electride have been studied using x-ray photoelectron spectroscopy. The work function of phase pure 12CaO·7Al2O3 electride was determined from direct thermionic emission data and compared to the measurement from ultraviolet photoelectron spectroscopy (UPS). Depending on the extent of ion template of 12CaO·7Al2O3 structure, a work function of 0.9–1.2 eV and 2.1–2.4 eV has been measured and thermionic emission initiating at 600°C.  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