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   1418篇
  免费   11篇
电工技术   5篇
化学工业   20篇
金属工艺   10篇
机械仪表   18篇
建筑科学   12篇
矿业工程   1篇
能源动力   9篇
轻工业   62篇
水利工程   3篇
无线电   15篇
一般工业技术   39篇
冶金工业   1193篇
原子能技术   1篇
自动化技术   41篇
  2023年   3篇
  2022年   4篇
  2021年   5篇
  2020年   5篇
  2019年   8篇
  2018年   9篇
  2017年   5篇
  2016年   5篇
  2015年   3篇
  2014年   9篇
  2013年   36篇
  2012年   15篇
  2011年   10篇
  2010年   14篇
  2009年   9篇
  2008年   15篇
  2007年   5篇
  2005年   8篇
  2004年   4篇
  2003年   7篇
  2002年   5篇
  2000年   2篇
  1999年   30篇
  1998年   387篇
  1997年   174篇
  1996年   139篇
  1995年   80篇
  1994年   51篇
  1993年   72篇
  1992年   8篇
  1991年   17篇
  1990年   10篇
  1989年   10篇
  1988年   15篇
  1987年   13篇
  1986年   13篇
  1985年   18篇
  1983年   4篇
  1982年   6篇
  1981年   7篇
  1980年   15篇
  1979年   5篇
  1978年   7篇
  1977年   47篇
  1976年   103篇
  1975年   3篇
  1972年   1篇
  1971年   1篇
  1965年   3篇
  1955年   1篇
排序方式: 共有1429条查询结果,搜索用时 93 毫秒
91.
Huntington's disease (HD) is an inherited neurodegenerative disease caused by expansion of a polyglutamine repeat in the HD protein huntingtin. Huntingtin's localization within the cell includes an association with cytoskeletal elements and vesicles. We previously identified a protein (HAP1) which binds to huntingtin in a glutamine repeat length-dependent manner. We now report that HAP1 interacts with cytoskeletal proteins, namely the p150 Glued subunit of dynactin and the pericentriolar protein PCM-1. Structural predictions indicate that both HAP1 and the interacting proteins have a high probability of forming coiled coils. We examined the interaction of HAP1 with p150 Glued . Binding of HAP1 to p150 Glued (amino acids 879-1150) was confirmed in vitro by binding of p150 Glued to a HAP1-GST fusion protein immobilized on glutathione-Sepharose beads. Also, HAP1 co-immunoprecipitated with p150 Glued from brain extracts, indicating that the interaction occurs in vivo . Like HAP1, p150 Glued is highly expressed in neurons in brain and both proteins are enriched in a nerve terminal vesicle-rich fraction. Double label immunofluorescence experiments in NGF-treated PC12 cells using confocal microscopy revealed that HAP1 and p150 Glued partially co-localize. These results suggest that HAP1 might function as an adaptor protein using coiled coils to mediate interactions among cytoskeletal, vesicular and motor proteins. Thus, HAP1 and huntingtin may play a role in vesicle trafficking within the cell and disruption of this function could contribute to the neuronal dysfunction and death seen in HD.  相似文献   
92.
INTRODUCTION: The most common fat-suppressed sequence used to study skeletal conditions is the STIR sequence which has shown high sensitivity in the detection of skeletal lesions and whose main drawback is its long acquisition time. Currently, Turbo-STIR (T-STIR) sequences can shorten the acquisition time. The purpose of this study was therefore to compare the conventional STIR sequence with the new T-STIR sequence in the study of skeletal conditions to compare their diagnostic yield. MATERIAL AND METHODS: Twenty patients with different types of skeletal lesions were examined. MR examinations were performed with a Philips Gyroscan S15/ACS II unit (1.5 T). All the patients underwent a STIR sequence (TR/TE = 1500/20, TI = 180 ms, matrix = 204 x 256, NEX = 2, slice thickness = 5 mm, acquisition time = 9 min 24 s) and a T-STIR sequence (TR/TE = 1500/20, TI = 180 ms, matrix = 204 x 256, NEX = 2, slice thickness = 5 mm, TFL = 3, acquisition time = 3 min 33 s). The images were evaluated by measuring both quantitative parameters--percent contrast (%C), contrast to noise ratio (C/N), signal to noise ratio (S/N)--and qualitative parameters--lesion conspicuity, margins and extension, motion artifacts, image quality. RESULTS: The only statistically significant difference between the two sequences was image quality, which was superior in the conventional STIR sequence (p < .05). No statistically significant difference was demonstrated with the quantitative evaluation. DISCUSSION: In this study, T-STIR sequences were performed with low-high acquisition profile to acquire an actual echo time of 20 ms which permits to obtain optimal S/N with good spatial resolution. Therefore, T-STIR sequences with low-high acquisition profile provides better results than T-STIR sequences with linear acquisition profile which permits to obtain an actual echo time of 40 ms. CONCLUSION: This work shows that T-STIR sequences can replace conventional STIR sequences in the study of skeletal conditions reducing the acquisition time by 60%. This result can be obtained only by an accurate optimization of acquisition parameters.  相似文献   
93.
The aril of the plant Myristica fragrans is one of the most broadly used spices in Moroccan gastronomy. This research demonstrated its antimicrobial activity against both gram-positive and gram-negative bacterial species. Likewise, its toxicity was investigated on Swiss albino mice. Mice were treated orally with 0.003 and 0.3 mg/day during 7 days. Plasmatic markers and antioxidant defense systems were assessed and histological alterations evaluated. Our results showed a significant increase in creatine phosphokinase level. The microscopic evaluation showed that mace induces morphological perturbation in mice's liver. The results also showed an inhibitory effect of glyceraldehyde 3-phosphate dehydrogenase and an important increase in the level of thiobarbituric acid reactive substances, succinate dehydrogenase activities and no change in catalase activities. All of these results show that M. fragrans at 0.3 mg/g in mice affects energy metabolism and oxidative stress.

PRACTICAL APPLICATIONS


Mace can be used as a natural antioxidant and preservative in the food industry to increase the shelf life of foodstuffs.  相似文献   
94.
95.
96.
In this paper, we suggest a modification to the conventional variable wavelength interferometry. This modification allowed us to calculate the dispersion curve of each point inside polymeric fibres instead of calculating the mean dispersion of these fibres. This modified mathematical treatment was used to calculate the three‐dimensional dispersion profile of isotactic polypropylene fibres suffering from necking deformation. The different steps of calculating the three‐dimensional dispersion profile of the fibre were demonstrated. The application of this modified method revealed the variation of the fibre material dispersion before, inside and after the necking region. In addition, the birefringence profile of the necked isotactic polypropylene was determined using the proposed mathematical treatment. This allowed us to diagnose the interaction of the incident waves with necked polypropylene fibres, which gives extensive information on the orientation of the molecular chains during the formation of the necking phenomenon.  相似文献   
97.
Deposition of yeast inside brewery process plant is a serious industrial problem. Investigation of the cleaning of beer fermenter deposits revealed two types of fouling; yeast foam (type A) and yeast film (type B). Rheological characterisation indicated both deposits could be mimicked in lab scale fouling experiments using yeast slurry aged for different times. Water and chemical rinsing of these deposits on a lab scale flow cell revealed three distinct cleaning phases: (i) hydration and swelling, (ii) removal in the flow by dissolution and in patches and (iii) no further removal. At 30 and 50 °C water rinsing at the flow velocities investigated could remove up to 85% of the deposit. At a water rinsing temperature of 70 °C, less deposit could be removed overall. Rheological studies indicated that increasing the temperature of the deposit generated a more elastic deposit which may decrease cleanability. Chemical cleaning using 2 wt% Advantis 210 (a NaOH base cleaning agent) eventually gave a visually clean surface at all flow velocities and temperatures. Chemical cleaning at 70 °C gave the shortest cleaning times for all flow velocities, but comparable cleaning times were observed when rinsing at 30 and 50 °C, suggesting that an increase in temperature from 30 to 50 °C might not decrease the cleaning time.  相似文献   
98.
Stuffed grape vine leaves, dolma is a well-liked Turkish dish, common to Mediterranean diets. Moisture, ash, energy, protein, fat, carbohydrate, calcium, sodium, iron, β-carotene (vitamin A), vitamin C analyses were conducted to determine the nutritional value of dolma. β-carotene level per 100 g serving of dolma (1041 IU) supplies 20.82% of the USRDA (5000 IU) and an INQ (Index of Nutritional Quality) for vitamin A of 2.54. Although the fat content and INQ for fat were found to be high in dolma, it can still be considered a healthy choice due to the type of oil used, namely olive oil, which has been shown to have beneficial effects on health.  相似文献   
99.
This paper introduces a double‐image multiple‐beam Fizeau fringes system. The introduced system can dynamically determine the variations of the refractive indices for both parallel and perpendicular polarization simultaneously. This is achieved by the simultaneous capturing of two multiple‐beam interference patterns during the mechanical processing of isotactic polypropylene fibre. This parallel determination of the refractive indices of both polarization directions allowed us to determine the full‐field distribution of the stress vector, S . To accomplish this, a mathematical model was deduced to calculate the components of the stress vector, S , i.e. parallel stress component, S1, and perpendicular stress component, S2. Double‐image Fizeau fringes system and the deduced mathematical model were used to investigate the variation of the refractive index and stress components of the fibre during the stretching process and propagation of necked regions.  相似文献   
100.
We examine the problem of uniqueness in the relationship between the remote-sensing reflectance (Rrs) and the inherent optical properties (IOPs) of ocean water. The results point to the fact that diffuse reflectance of plane irradiance from ocean water is inherently ambiguous. Furthermore, in the 400 < lambda < 750 nm region of the spectrum, Rrs(lambda) also suffers from ambiguity caused by the similarity in wavelength dependence of the coefficients of absorption by particulate matter and of absorption by colored dissolved organic matter. The absorption coefficients have overlapping exponential responses, which lead to the fact that more than one combination of IOPs can produce nearly the same Rrs spectrum. This ambiguity in absorption parameters demands that we identify the regions of the Rrs spectrum where we can isolate the effects that are due only to scattering by particulates and to absorption by pure water. The results indicate that the spectral shape of the absorption coefficient of phytoplankton, a(ph)(lambda), cannot be derived from a multiparameter fit to Rrs(lambda). However, the magnitude and the spectral dependence of the absorption coefficient can be estimated from the difference between the measured Rrs(lambda) and the best fit to Rrs(lambda) in terms of IOPs that exclude a(ph)(lambda).  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