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   201篇
  免费   18篇
电工技术   1篇
化学工业   36篇
金属工艺   1篇
机械仪表   2篇
建筑科学   9篇
能源动力   3篇
轻工业   39篇
无线电   13篇
一般工业技术   40篇
冶金工业   25篇
原子能技术   1篇
自动化技术   49篇
  2023年   2篇
  2022年   3篇
  2021年   6篇
  2020年   9篇
  2019年   5篇
  2018年   9篇
  2017年   8篇
  2016年   5篇
  2015年   5篇
  2014年   7篇
  2013年   10篇
  2012年   19篇
  2011年   14篇
  2010年   11篇
  2009年   17篇
  2008年   14篇
  2007年   15篇
  2006年   10篇
  2005年   4篇
  2004年   3篇
  2003年   6篇
  2002年   4篇
  2001年   4篇
  2000年   4篇
  1999年   3篇
  1998年   4篇
  1997年   1篇
  1996年   2篇
  1995年   2篇
  1993年   1篇
  1990年   1篇
  1988年   2篇
  1986年   1篇
  1985年   1篇
  1984年   1篇
  1981年   1篇
  1980年   1篇
  1978年   1篇
  1974年   1篇
  1968年   1篇
  1967年   1篇
排序方式: 共有219条查询结果,搜索用时 390 毫秒
61.
The associations between marital discord and multiple measures of well-being (depression, anxiety, life satisfaction, and self-esteem) were evaluated in a population-based sample of 416 couples in which the husband was 65 years or older. Results indicated that greater marital discord was associated with greater depression and lower life satisfaction and self-esteem. Furthermore, the associations between marital discord and well-being remained significant when statistically controlling for the rival explanation of the Big Five personality traits. Finally, there was little evidence for gender differences in the magnitude of the associations between marital discord and well-being. Findings suggest that marital discord is an important correlate of multiple measures of well-being in older individuals and that this association is not confounded by the Big Five personality traits. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
62.
A three-dimensional statistical evaluation framework for performance measurement of robotic systems has been developed. A specific experimental setup has been designed, implemented, and evaluated for different robot characteristics (velocities and target location) and for a specific task. A statistical analysis method to evaluate performance is demonstrated. Results indicate the significance of this methodology since the capabilities and performance of a particular robot depend on actual operating conditions.  相似文献   
63.
Ninety 4- to 13-year-old alleged victims of sexual abuse were interviewed by police officers using the National Institute of Child Health and Human Development (NICHD) investigative interview protocol, following which they were shown a human figure drawing and asked a series of questions. The drawing and associated questions elicited an average of 86 new forensically relevant details. They were especially productive with 4- to 7-year-olds, who provided an average of 95 additional details (27% of their total) after the drawing was introduced despite having previously "exhausted" their memories. Information elicited using the drawing may be less accurate, however, because recognition memory prompts predominated, so such drawings should only be introduced late in investigative interviews. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
64.
Diffusion MRI studies revealed specific morphological and physiological properties of MCF7 tumors implanted in the mammary gland of immunodeficient mice. These tumors mimic the histological and pathophysiological properties of human breast cancer in patients. The experiments were conducted by (1) applying varying diffusion gradient strengths, Gd, from 0 to 20 G/cm and a short diffusion time (td = 16 ms) in order to minimize the effect of restriction and exchange of water between the intra- and extracellular compartments, and (2) applying a strong constant gradient and diffusion times up to 96 ms, revealing water restriction and exchange. The normalized signal intensity was plotted against the diffusion weighting factor b , taking into account interaction with the imaging gradients. The curves were analyzed by applying a bi-exponential decay function assuming two exchanging water compartments, with fast and slow diffusion coefficients. The amplitudes and decay constants of the two exponents, a fast and a slow one, were related to the fraction and apparent diffusion coefficients of the extra- and intracellular water, respectively, considering contributions of restriction and exchange. During tumor progression the distribution of the diffusion parameters for the same experimental protocol varied and became less homogeneous. This was predominantly due to variations in the cellularity and increased necrosis. Upon treatment of the tumors with a new anti-estrogenic drug, tamoxifen methiodide, the changes in the diffusion parameters indicated increased cell swelling. Hence, this cytostatic response to treatment was detected before actual cell death was apparent. The potential capacity of diffusion MRI is of high clinical relevance and may help improve the noninvasive diagnosis and followup of treatment of this devastating disease.  相似文献   
65.
Experimental thermal analysis and mass spectrometric results indicate that, when heated, monomethylamine nitrate dissociates to form monomethylamine anMonomethylamine, one of the dissociation products, is a flammable gas. In dry air, at room temperature, its lower limit of flammability is 4.9%. Its auPreventing acid build-up and rust formation is important for the safe handling and transport of monomethylamine nitrate.  相似文献   
66.
A systematic study was carried out to evaluate the effect of up to 2.5% yttrium additions on the properties of Mg–3%Nd alloy designated for high-temperature gravity casting applications. All the tested alloys were grain-refined by zirconium. The results show that additions of yttrium significantly improved the tensile yield strength, fatigue strength, and creep resistance while reducing the ductility. However, other properties such as the ultimate tensile strength and corrosion resistance in 5% NaCl solution were nearly not affected. The strengthening effect obtained by the yttrium additions is explained in terms of solid-solution strengthening and due to formation of a ternary phase of Mg–Nd–Y. The improved creep resistance was due to the large solubility of yttrium in solid-solution magnesium matrix and to the effective creep deformation barriers created by the ternary phase. The casting performance of the tested alloys in terms of fluidity was similar and no significant effect of the yttrium was evident  相似文献   
67.
Gilboa Y  Friedler E 《Water research》2008,42(4-5):1043-1050
The microbial quality of raw greywater was found to be much better than that of municipal wastewater, with 1.6 x 10(7)cfu ml(-1) heterotrophic plate count (HPC), and 3.8 x 10(4), 9.9 x 10(3), 3.3 x 10(3) and 4.6 x 10(0)cfu 100 ml(-1) faecal coliforms (FC), Staphylococcus aureus sp., Pseudomonas aeruginosa sp. and Clostridium perfringes sp., respectively. Further, three viral indicators monitored (somatic phage, host: Escherichia coli CN(13) and F-RNA phages, hosts: E. coli F+(amp), E. coli K12) were not present in raw greywater. The greywater was treated by an RBC followed by sedimentation. The treatment removed two orders of magnitude of all bacteria. UV disinfection kinetics, survival and regrowth of HPC, FC, P. aeruginosa sp. and S. aureus sp. were examined. At doses up to 69 mW s cm(-2) FC were found to be the most resistant bacteria, followed by HPC, P. aeruginosa sp. and S. aureus sp. (inactivation rate coefficients: 0.0687, 0.113, 0.129 and 0.201 cm2 mW(-1)s(-1), respectively). At higher doses (69-439 mW s cm(-2)) all but HPC (which exhibited a tailing curve) were completely eliminated. Microscopic examination showed that FC self-aggregate in the greywater effluent. This provides FC an advantage at low doses, since the concentration of suspended matter (that can provide shelter from UV radiation) in the effluent was very low. FC, P. aeruginosa sp. and S. aureus sp. did not exhibit regrowth up to 6h after exposure to increasing UV doses (19-439 mW s cm(-2)). HPC regrowth was proven to be statistically significant in un-disinfected effluent and after irradiation with high UV doses (147 and 439 mW s cm(-2)). At these doses regrowth resulted from growth of UV-resistant bacteria due to decreased competition with other bacteria eliminated by the irradiation.  相似文献   
68.
The human eye is affected by large chromatic aberration. This may limit vision and makes it difficult to see fine retinal details in ophthalmoscopy. We designed and built a two-triplet system for correcting the average longitudinal chromatic aberration of the eye while keeping a reasonably wide field of view. Measurements in real eyes were conducted to examine the level and optical quality of the correction. We also performed some tests to evaluate the effect of the corrector on visual performance.  相似文献   
69.
Peritoneal dialysis (PD) is commonly performed by using preprepared dialysis solutions containing glucose, which are thermally treated to achieve commercial sterilization. A series of glucose degradation products (GDPs) are being formed, which react with the tissue during the dialysis procedure, thus baring a negative effect on the patient and the dialysis process. The present study tested the efficacy of ohmic heating as an alternative thermal treatment for continuous sterilization of PD solutions. The process was compared to conventional retort treatment, and GDPs accumulation was measured. Thermal treatments using the ohmic heating system were performed at three temperatures (105, 125, and 150 degrees C) with residence time at each temperature ranging from 0.84 to 12.0 s. The resulting concentrations of glyoxal (GO), methylglyoxal (MGO), and 3-deoxyglucosone (3-DG) in the PD solutions were measured. None of these GDPs were found in PD fluids treated by ohmic heating at 105 degrees C. The concentration of 3-DG, after a standard sterilization treatment (121 degrees C, 20 or 40 min) was one order of magnitude higher (approximately 140 and 242 microM) than after ohmic heating treatment at 125 degrees C. The results of the present study suggest that this technique can be used to produce solutions with much lower content of GDPs. It also demonstrates the advantage of using the ohmic heating technology as a tool for high temperature short time treatment of PD fluids.  相似文献   
70.

Background

We examined the effect of four weeks of ??-alanine supplementation on isometric endurance of the knee extensors at 45% maximal voluntary isometric contraction (MVIC).

Methods

Thirteen males (age 23?±?6 y; height 1.80?±?0.05?m; body mass 81.0?±?10.5?kg), matched for pre-supplementation isometric endurance, were allocated to either a placebo (n?=?6) or ??-alanine (n?=?7; 6.4?g·d-1 over 4?weeks) supplementation group. Participants completed an isometric knee extension test (IKET) to fatigue, at an intensity of 45% MVIC, before and after supplementation. In addition, two habituation tests were completed in the week prior to the pre-supplementation test and a further practice test was completed in the week prior to the post-supplementation test. MVIC force, IKET hold-time, and impulse generated were recorded.

Results

IKET hold-time increased by 9.7?±?9.4?s (13.2%) and impulse by 3.7?±?1.3 kN·s-1 (13.9%) following ??-alanine supplementation. These changes were significantly greater than those in the placebo group (IKET: t (11)?=?2.9, p ??0.05; impulse: t (11)?=?3.1, p????0.05). There were no significant changes in MVIC force in either group.

Conclusion

Four weeks of ??-alanine supplementation at 6.4?g·d-1 improved endurance capacity of the knee extensors at 45% MVIC, which most likely results from improved pH regulation within the muscle cell as a result of elevated muscle carnosine levels.  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