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   550篇
  免费   14篇
电工技术   6篇
综合类   2篇
化学工业   107篇
金属工艺   11篇
机械仪表   25篇
建筑科学   8篇
能源动力   83篇
轻工业   110篇
水利工程   1篇
石油天然气   5篇
无线电   29篇
一般工业技术   72篇
冶金工业   53篇
原子能技术   3篇
自动化技术   49篇
  2024年   8篇
  2023年   5篇
  2022年   4篇
  2021年   14篇
  2020年   26篇
  2019年   18篇
  2018年   24篇
  2017年   23篇
  2016年   26篇
  2015年   3篇
  2014年   21篇
  2013年   49篇
  2012年   34篇
  2011年   34篇
  2010年   36篇
  2009年   34篇
  2008年   27篇
  2007年   31篇
  2006年   8篇
  2005年   12篇
  2004年   14篇
  2003年   11篇
  2002年   5篇
  2001年   11篇
  2000年   7篇
  1999年   7篇
  1998年   25篇
  1997年   15篇
  1996年   11篇
  1995年   2篇
  1994年   5篇
  1993年   5篇
  1992年   2篇
  1991年   2篇
  1990年   1篇
  1988年   1篇
  1987年   1篇
  1981年   1篇
  1979年   1篇
排序方式: 共有564条查询结果,搜索用时 46 毫秒
61.
The behavioral effects were studied of monoclonal antibodies (MA) against A3G7 protein, which is known to be associated with the processes of nervous cell differentiation. Elaboration, storage, and retention of acoustic startle (ASR) habituation and freezing behavior were tested in adult rats. The MA applied in a dose of 50 ng on cerebellar vermis selectively impaired only the ASR long-term habituation storage whereas its dose of 5 mcg impaired both long-term habituation storage and fear-conditioned freezing. Application of 10 mcg of MA disrupted the elaboration and storage of the ASR short- and long-term habituation as well as fear-conditioned freezing. The results are considered as experimental verification of systemogenesis theory and hypothesis about a common molecular basis of learning and development.  相似文献   
62.
Optimum insulation thickness of a circular duct subjected to external radiative heat transfer is studied for a given amount of insulation material. A circular duct through which fluid is transported from one end to the other is considered. The thickness of the insulation is assumed to be linearly varying since this is easy to implement in practice. Thus the slope of the insulation thickness is considered as the parameter for optimum insulation. Variations of the bulk temperature of the fluid as well as the temperature of the outer surface of the insulation are evaluated. It is shown that linearly decreasing insulation thickness with minimum slope provides the best insulation under the radiation heat transfer condition. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   
63.
In this study we have investigated the distribution of dermatophyte species clinically and microbiologically on 110 patients with dermatophytosis. The distribution of the dermatophytes according to the localization sites are: Tinea Capitis 13 (11.8%), T. Corporis 12 (10.9%), T. Inguinalis 22 (20%), T. Pedis et Manum 47 (42.7%), T. Unguinum 16 (14.5%). The species of dermatophytes which have been cultured were, Trichophyton rubrum 32 (29%), T. mentagrophytes 32 (29%), T. schoenleini 4 (3.6%), T. tonsurans 1 (0.9%), Epidermophyton floccosum 16 (14.5%), Microsporum canis 1 (0.9%), M. audouini 1 (0.9%), various molds 3 (2.7%) and also number of negative cultures obtained were 20 (18.1%).  相似文献   
64.
The authors study two types of replacement policies, following the expiration of warranty, for a unit with an IFR failure-time distribution: (1) the user applies minimal repair for a fixed length of time and replaces the unit by a new one at the end of this period; and (2) the unit is replaced by the user at first failure following the minimal repair period. In addition to stationary strategies that minimize the long-run mean cost to the user, the authors also consider nonstationary strategies that arise following the expiration of a nonrenewing warranty. Following renewing warranties, they prove that the cost rate function is pseudo-convex under a fixed maintenance period policy. The same result holds under nonrenewing repair warranties, and nonrenewing replacement warranties when the optimal maintenance period of each cycle is determined as a function of the age of the item in use at the end of the warranty period  相似文献   
65.
A 61-day short-term prospective study comparing the efficacy of Chemiron capsules (Ferrous Fumarate 300 mg, Folic Acid 5 mg, Vitamin B12 10 ug, Vitamin C 25 mg, Magnesium sulphate, 0.3 mg and Zinc Sulphate 0.3 mg) with conventional ferrous gluconate and folic acid administration has shown that both haematinic regimens improve haematological indices in normal pregnant women. A significant rise in haemoglobin was seen in the Chemiron group on days 5 and 19 whereas a significant increase in packed cell volume was observed on days 5, 19 and 61. There were no significant differences between the mean value of platelets during the therapy period in either group. A significant rise in the mean reticulocyte values could be demonstrated in the Chemiron group throughout the study period. This study further shows that Chemiron has a better haematological effect than Ferrous Gluconate at the dosage used.  相似文献   
66.
Friction welding of Al-Al,Al-steel,and steel-steel samples   总被引:2,自引:0,他引:2  
Friction welding of Al- Al, Al- steel, and steel- steel studs is compared. Transient heat generation and temperature rise during the welding process were modeled. Tensile tests and microhardness measurements across the weld zone were carried out. The metallurgical changes in the heat- affected zone were examined by SEM. Temperature rise at the interface plane was computed and related to weld properties. The affecting parameters on weld quality were identified by statistical analysis. Results show that interaction of weld parameters significantly affect yield, tensile, and breaking strength, and the heat- affected zone on the Al side is wider for Al-steel welds.  相似文献   
67.
There is a paucity of data in respect of the nutritional quality of complementary foods for infants and young children aged between 6 and 12 months. In this study, we developed and validated an analytical method for determination of the endocrine-disrupting organochlorine pesticides (OCPs) and elements (As, Cd, and Pb) in infant formula and baby foods. Therefore, it found out the contamination level of the both OCPs and some trace metals (As, Cd, and Pb) in widely consumed infant formula and baby food in Turkey. Metal concentrations in baby foods and infant formula were determined by inductively coupled plasma mass spectrometry. Samples were digested with nitric acid and hydrogen peroxide in a microwave oven. Determination of 24 organochlorine pesticide residues in baby foods and infant formula was completed by using gas chromatography double mass spectrometry. QuEChERS extraction method was carried out in the sample preparation part. The analytical performance of the entire procedure, such as linearity, the detection of limit, limit of quantification, specificity/selectivity, recovery (%), and precision, were assessed. The recoveries ranged from 93% (As) to 100% (Pb) for elements 78–98% for organochlorine pesticide residues (OCPs) at 100 ng mL?1. According to the results, lead, cadmium, and pesticides were not detected in any of the samples, while arsenic was detected in 16 samples.  相似文献   
68.
PCR assay for the identification of animal species in cooked sausages   总被引:1,自引:0,他引:1  
Kesmen Z  Sahin F  Yetim H 《Meat science》2007,77(4):649-653
A species-specific PCR assay was developed for the detection of low levels of pork, horse and donkey meat in cooked sausages. Oligonucleotid primers were designed for amplification of species-specific mitochondrial DNA sequences of each species and detected the presence of 0.01 ng of template DNA in water. When applying the assay to DNA extracts from sausages samples that were prepared from binary meat mixtures, it was possible to detect each species when spiked in any other species at the 0.1% level. In conclusion, it can be suggested that this assay can be used to determine mislabelled and/or fraudulent species substitution in comminuted meat products.  相似文献   
69.
The effects of fat content and emulsifier type on the rheological properties of cake batter have been investigated by using a parallel-plate rheometer. The apparent viscosity of cake batter with five different fat concentrations (0, 12.5, 25, 37.5, and 50%) and two types of emulsifier, namely Purawave and Lecigran, was studied as a function of the shear rate. In addition, the time dependency of different cake formulations was investigated. It was found that cake batter with different fat concentrations and emulsifier types exhibited shear thinning and time-independent behavior. Experimental data provided a good fit for the power law model. The increase in fat content and addition of emulsifier caused a decrease in the apparent viscosity. The flow behavior index was not found to be dependent on the composition of cake batter.  相似文献   
70.
Microwave heating can be combined with other means of heating to yield a unique heating profile. In the study, microwave frying, a combination of convective and microwave heating, was compared with conventional frying. Frying experiments were performed by inserting a single food sample (chicken breast meat) in the hot oil at 180?±?1°C for both frying methods. Center temperature of the sample and the oil temperature were recorded during both frying methods. Simulations were performed to predict heat transfer coefficients. Processing time was shorter with microwave frying. Simulations revealed a varying convective heat transfer coefficient, which was in the range of 160–490 W/m2 K, during conventional frying. Higher convective heat transfer coefficient, 500 W/m2 K, compared to conventional frying was observed during microwave frying with the simulations. This is suggested to be due to higher turbulence in microwave frying.  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