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   5040篇
  免费   280篇
  国内免费   25篇
电工技术   59篇
综合类   5篇
化学工业   1221篇
金属工艺   149篇
机械仪表   168篇
建筑科学   188篇
矿业工程   14篇
能源动力   579篇
轻工业   633篇
水利工程   23篇
石油天然气   79篇
无线电   337篇
一般工业技术   943篇
冶金工业   187篇
原子能技术   27篇
自动化技术   733篇
  2024年   20篇
  2023年   86篇
  2022年   189篇
  2021年   265篇
  2020年   196篇
  2019年   168篇
  2018年   313篇
  2017年   241篇
  2016年   270篇
  2015年   174篇
  2014年   259篇
  2013年   563篇
  2012年   246篇
  2011年   313篇
  2010年   272篇
  2009年   247篇
  2008年   201篇
  2007年   192篇
  2006年   132篇
  2005年   74篇
  2004年   88篇
  2003年   78篇
  2002年   64篇
  2001年   39篇
  2000年   40篇
  1999年   39篇
  1998年   60篇
  1997年   38篇
  1996年   38篇
  1995年   44篇
  1994年   21篇
  1993年   31篇
  1992年   24篇
  1991年   21篇
  1990年   19篇
  1989年   22篇
  1988年   12篇
  1987年   15篇
  1986年   13篇
  1985年   33篇
  1984年   25篇
  1983年   12篇
  1982年   19篇
  1981年   24篇
  1980年   19篇
  1979年   10篇
  1976年   10篇
  1975年   9篇
  1974年   10篇
  1973年   15篇
排序方式: 共有5345条查询结果,搜索用时 8 毫秒
1.
The viability and β‐galactosidase activity of four Lactobacillus strains in milk drink containing gums during 28 days of refrigerated storage at 4 °C were assessed. The population of Lactobacillus rhamnosus GGB101 and Lactobacillus rhamnosus GGB103 were maintained, whereas the population of Lactobacillus reuteri DSM20016 and Lactobacillus reuteri SD2112 significantly decreased. The recommended level of 6 log CFU g?1 was exceeded for all tested trains throughout storage. The highest viable number of Lactobacillus rhamnosus GGB103 (8.76 ± 0.03 log CFU mL?1) was obtained in the product containing carrageenan–maltodextrin. The addition of guar–locust bean–carrageenan led to 20‐fold increase in the level of β‐galactosidase activity for L. rhamnosus GGB101 (1208 ± 2.12 Miller units mL?1) compared to the control (61 ± 2.83 Miller units mL?1). Our results suggested that gums could be added to milk to improve viability and enhance β‐galactosidase activity of Lactobacillus.  相似文献   
2.
3.
4.
One of the frequently discussed applications of artificial intelligence in motion control is the replacement of a standard proportional plus integral (PI) speed controller with a fuzzy logic (FL) speed controller. Regardless of all the work, it appears that a thorough comparison of the drive behavior under PI and FL speed control is still missing. This paper attempts to fill in this gap, by providing an in-depth comparison of operation of a vector-controlled permanent-magnet synchronous motor, using at first an experimental rig. Speed responses, obtained under PI and FL speed control, are recorded and compared for a variety of operating conditions. The transients studied include response to a large step speed command from standstill with nominal inertia and an increased inertia, response to small step speed reference change, and response to step load torque application. The transient behavior is examined for various initial speed settings, so that a thorough comparison is enabled. Experimental results are further supplemented with a set of simulation results, obtained using a different permanent-magnet machine and a different FL controller. Better generalization of the results is enabled in this way. It is shown that superiority of the FL speed control is less pronounced than it is often portrayed in the literature on the basis of limited comparisons. Indeed, in a number of cases, PI speed control provides a superior speed response.  相似文献   
5.
Bismuth is a semimetal that has a relatively low lattice thermal conductivity. A positive energy gap can be created by alloying with antimony, leading to useful alloys for thermoelectric energy conversion. This paper gives an insight into the basic properties of BiSb alloys for thermoelectric applications.  相似文献   
6.
Physically based simulation of human hair is a well studied and well known problem. But the “pure” physically based representation of hair (and other animation elements) is not the only concern of the animators, who want to “control” the creation and animation phases of the content. This paper describes a sketch-based tool, with which a user can both create hair models with different styling parameters and produce animations of these created hair models using physically and key frame-based techniques. The model creation and animation production tasks are all performed with direct manipulation techniques in real-time.  相似文献   
7.
This study investigates the relationship between the critical surface tension of wetting of celestite and agglomeration recovery as well as the zeta potential in dependence of pH and amount of collector (Na‐Oleate). For this purpose, effects of pH and collector amount on the agglomeration recovery are investigated and zeta potential measurements and Fourier Transform Infrared Spectrophotometer (FTIR) analyses are carried out to determine the adsorption type of Na‐Oleate on celestite surface. The sessile drop technique is used for the measurement of contact angle and determination of the critical surface tension of wetting (YC) of celestite. The maximum agglomeration recovery is obtained at pH 7. The critical surface tension of wetting of celestite is very close to the surface tension of kerosene, which is 25.95 mN/m. Furthermore, at the optimum Na‐Oleate amount of 10 kg/ton, the critical surface tension of wetting of celestite is approximately equal to the surface tension of kerosene.  相似文献   
8.
Asphaltenes obtained by precipitation from crude Kuwaiti oils have been analyzed by proton magnetic resonance (1H-NMR), carbon-13 nuclear magnetic resonance (13C-NMR) and Infrared (IR) spectral techniques. The molecular weight and elemental analysis were also determined. These combined analytical data were used for the characterization of these Kuwaiti oils. The asphaltenes molecular weights range from approximately 4200-6500 with an H/C ratio of 0.91-1.1 with an average 45-71% aromatic carbons. The average side chain length was of 4-6 carbons. It can also be concluded that the asphaltenes under investigation contain 5-9 sets of condensed aromatic rings joined together by bridges of alkyl chains or other hetero atoms and the average number of each of these sets of condensed aromatic rings is nearly 7. There are a number of alicyclic rings and condensed alicyclic rings in asphaltene. The IR spectra showed main molecular groups including OH, NH, SH, C=O and aliphatic and aromatic C-H's.  相似文献   
9.
In this study forecast of Turkey's net electricity energy consumption on sectoral basis until 2020 is explored. Artificial neural networks (ANN) is preferred as forecasting tool. The reasons behind choosing ANN are the ability of ANN to forecast future values of more than one variable at the same time and to model the nonlinear relation in the data structure. Founded forecast results by ANN are compared with official forecasts.  相似文献   
10.
Five labdane diterpenoids, austroinulin, iso-austroinulin, sterebin E, sterebin E acetate, and sterebin A acetate, along with hydrocarbons, aliphatic alcohols, β-amyrin, β-sitosterol and stigmasterol were isolated from the chloroform soluble fraction of the methanol extract of Stevia rebaudiana leaves. Chlorogenic and caffeic acids were isolated from the EtOAc fraction. All the isolated compounds were identified using spectral tools. The chloroform and methanol extracts proved significant anti-inflammatory effect and caused marked inhibition of carrageenan-induced paw oedema in rats.  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