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   144篇
  免费   7篇
化学工业   47篇
金属工艺   3篇
机械仪表   4篇
建筑科学   7篇
能源动力   1篇
轻工业   15篇
水利工程   1篇
无线电   2篇
一般工业技术   20篇
冶金工业   17篇
自动化技术   34篇
  2023年   2篇
  2022年   7篇
  2021年   14篇
  2020年   2篇
  2019年   3篇
  2018年   6篇
  2017年   7篇
  2016年   2篇
  2015年   4篇
  2014年   1篇
  2013年   8篇
  2012年   10篇
  2011年   13篇
  2010年   7篇
  2009年   7篇
  2008年   7篇
  2007年   9篇
  2006年   3篇
  2005年   3篇
  2004年   3篇
  2002年   2篇
  2001年   1篇
  1999年   2篇
  1998年   8篇
  1997年   5篇
  1996年   3篇
  1995年   6篇
  1993年   1篇
  1992年   2篇
  1982年   2篇
  1974年   1篇
排序方式: 共有151条查询结果,搜索用时 15 毫秒
21.
22.
To compare the compliance with and tolerance of mefloquine (MQ) and chloroquine + proguanil (CQ-PRO) chemoprophylaxis, we conducted a study using a self-reported questionnaire in 2 groups of native French adult visitors to Senegal or Kenya. CQ (100 mg daily) + PRO (200 mg daily) prophylaxis was prescribed for all patients travelling to Senegal and for those going to Kenya when MQ was contraindicated; MQ (250 mg weekly) was prescribed for the other subjects. There were no significant differences in age, sex, exposition and measures of protection against mosquito bites, concomitant drug use or mean duration of chemoprophylaxis between the 2 groups, and compliance during travel was excellent in both. Chemoprophylaxis was more frequently interrupted prematurely in the MQ group. The rates of overall side-effects attributed to malaria chemoprophylaxis were 16% for MQ against 12% CQ-PRO (not significant). However, nonserious neuropsychiatric adverse events are more frequent with MQ: 11.5% compared to 2% with CQ-PRO. MQ should be used with caution.  相似文献   
23.
24.
The objective is to describe injuries of road traffic deaths in Barcelona and identify injury profiles by road user type, through a cross-sectional study including road traffic deaths for the period 1997-2004. The data source was the Institut de Medicina Legal de Catalunya. Diagnoses were coded using the International Classification of Diseases, 9th revision, Clinical Modification, and classified using the Barell Matrix. Of the 719 deaths studied, 45% were pedestrians, 32% two wheel motor vehicle users, and 23% car occupants. The injury profile of the road traffic deaths in Barcelona is internal injuries and fractures to the torso and to the head/neck. This profile is repeated in all the road user groups, although pedestrians present higher frequencies of fractures and contusions to extremities and contusions to the head/neck, and fewer internal torso injuries than car occupants or two wheel motor vehicle users.  相似文献   
25.
The CXCR4 receptor has been shown to interact with the human immunodeficiency virus (HIV) envelope glycoprotein gp120, leading to fusion of viral and cell membranes. Therefore, ligands that can attach to this receptor represent an important class of therapeutic agents against HIV, thus inhibiting the first step in the cycle of viral infection: the virus–cell entry/fusion. Herein we describe the in silico design, synthesis, and biological evaluation of novel monocyclam derivatives as HIV entry inhibitors. In vitro activity testing of these compounds in cell cultures against HIV strains revealed EC50 values in the low micromolar range without cytotoxicity at the concentrations tested. Docking and molecular dynamics simulations were performed to predict the binding interactions between CXCR4 and the novel monocyclam derivatives. A binding mode of these compounds is proposed which is consistent with the main existing site‐directed mutagenesis data on the CXCR4 co‐receptor. Moreover, molecular modeling comparisons were performed between these novel monocyclams, previously reported non‐cyclam compounds from which the monocyclams are derived, and the well‐known AMD3100 bicyclam CXCR4 inhibitors. Our results suggest that these three structurally diverse CXCR4 inhibitors bind to overlapping but not identical amino acid residues in the transmembrane regions of the receptor.  相似文献   
26.
There is an increasing demand of multifunctional materials for a wide variety of technological developments. Bipolar plates for proton exchange membrane fuel cells are an example of complex functionality components that must show among other properties high mechanical strength, electrical, and thermal conductivity. The present research explored the possibility of using alumina–carbon nanofibers (CNFs) nanocomposites for this purpose. In this study, it was studied for the first time the whole range of powder compositions in this system. Homogeneous powders mixtures were prepared and subsequently sintered by spark plasma sintering. The materials obtained were thoroughly characterized and compared in terms of properties required to be used as bipolar plates. The control on material microstructure and composition allows designing materials where mechanical or electrical performances are enhanced. A 50/50 vol.% alumina–CNFs composite appears to be a very promising material for this kind of application.  相似文献   
27.
Alumina-carbon nanofibres (CNFs) and silicon carbide–CNFs nanocomposites with different volume fraction of CNFs (0–100 vol.%) were obtained by spark plasma sintering. The effect of CNFs content on the tribological behaviour in dry sliding conditions on the ceramic–carbon nanocomposites has been investigated using the ball-on-disk technique against alumina balls. The wear rate of ceramic–CNFs nanocomposites decreases with CNFs increasing content. The friction coefficient of the Al2O3/CNFs and SiC/CNFs nanocomposites with high CNFs content was found to be significantly lower compared to monolithic Al2O3 and SiC due to the effect of CNFs and unexpectedly slightly lower than CNFs material. The main wear mechanism in the nanocomposite was abrasion of the ceramic and carbon components which act in the interface as a sort of lubricating media. The experimental results demonstrate that the addition of CNFs to the ceramic composites significantly reduces friction coefficient and wear rate, resulting in suitable materials for unlubricated tribological applications.  相似文献   
28.
A pentapod is usually defined as a 5-degrees-of-freedom fully-parallel manipulator with an axial spindle as moving platform. This kind of manipulators has revealed as an interesting alternative to serial robots handling axisymmetric tools. Their particular geometry permits that, in one tool axis, high inclination angles could be attained, thus overcoming the orientation limits of the classical Stewart-Gough platform. This paper deals with pentapods with coplanar base attachments.In previous works changes in the location of the leg attachments that do not modify the singularity locus of the pentapod were studied. Such leg rearrangements reveal here as a powerful tool to shed light on the geometric structure of the singularity locus and, in particular, on architectural singularities.Indeed, a complete analysis of such singularities is carried out, providing both algebraic conditions, which complete previous results found in literature, and a geometrical interpretation that permits defining a measure of distance to architectural singularities. Such measure can be used as an index in the design process to obtain manipulators as far as possible from architectural singularities, leading to a better global behavior.  相似文献   
29.

Background

There is evidence that geographic variability of social health inequalities continues to exist even after individual risk factors have been taken into account. However, relatively few studies have examined the contribution of exposure to air pollutants to those inequalities.

Objectives

To study the geographic variability of inequalities in mortality and their associations with socioeconomic and environmental inequalities in small areas of the metropolitan of Barcelona during the period 1994 to 2003.

Methods

As in the MEDEA Project, the small area unit was the census tract. Study population consisted of the residents of the metropolitan area of Barcelona. Response variables were all-cause and specific-cause standardized mortality ratio (SMR). Explanatory variables were deprivation index, summarizing socioeconomic variables of the census tracts, and estimates of air pollutant exposures. Bayesian hierarchical models were used in order to reduce the extra variability when using SMR and to assess associations between mortality and deprivation and air pollution.

Results

Statistically significant associations with deprivation were found for the causes of death related to consumption of tobacco and alcohol for men and, besides lung cancer, diet-related causes for women. Statistically significant pollution coefficients were only found in the metropolitan area of Barcelona and in men. A positive interaction between pollutants and the deprivation index was statistically significant for respiratory mortality and PM10, and ischemic disease mortality and NO2, both for men.

Conclusions

We found deprivation to be associated in a statistically significant way with the geographical variation in mortality in the census tracts of the metropolitan area of Barcelona, in the period 1994 to 2003. Those air pollutants more directly related with traffic modify some of these associations.  相似文献   
30.
Blubber from Mediterranean monk seals (Monachus monachus) from the Western Sahara coast (Atlantic), sampled during 1996-1999, and from the Greek coast (Mediterranean), sampled during 1995-1999, was analyzed for organochlorine pollutants (OCs). In both populations, no significant difference was found between sexes. In the Atlantic population, mature females presented greater percentages of higher chlorinated PCB (polychlorinated biphenyl) congeners in relation to total PCBs (sum of 25 congeners) than pups, indicating a differential transfer of PCB congeners through lactation. In the Mediterranean, the reduced sample size of adult individuals precluded proper statistical investigation of age-related variation. Significant differences in concentrations and pollutant patterns were found between populations. Thus, Mediterranean individuals presented significantly higher levels of HCB (hexachlorobenzene), tPCB, and DDTs (dichlorodiphenyltrichloroethane) concentrations and DDE/tDDT and tDDT/tPCB ratios than their counterparts from the Atlantic. Moreover, the relative proportion of different congeners in relation to the total PCB load (congener/tPCB) was also different between the two areas. The 100*tDDT/tPCB ratio in Atlantic seals was 38.46, which indicates a predominance of industrial inputs over those associated with agriculture. Conversely, in the Mediterranean seal population, the 100*tDDT/tPCB ratio was 177.1, denoting a proportionally higher contribution of pollutants of agricultural origin.  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