全文获取类型
收费全文 | 1124篇 |
免费 | 33篇 |
专业分类
电工技术 | 5篇 |
化学工业 | 152篇 |
金属工艺 | 4篇 |
机械仪表 | 17篇 |
建筑科学 | 62篇 |
矿业工程 | 3篇 |
能源动力 | 30篇 |
轻工业 | 115篇 |
水利工程 | 19篇 |
石油天然气 | 3篇 |
无线电 | 68篇 |
一般工业技术 | 118篇 |
冶金工业 | 436篇 |
原子能技术 | 1篇 |
自动化技术 | 124篇 |
出版年
2023年 | 8篇 |
2022年 | 6篇 |
2021年 | 15篇 |
2020年 | 18篇 |
2019年 | 12篇 |
2018年 | 14篇 |
2017年 | 16篇 |
2016年 | 21篇 |
2015年 | 19篇 |
2014年 | 37篇 |
2013年 | 60篇 |
2012年 | 47篇 |
2011年 | 63篇 |
2010年 | 43篇 |
2009年 | 28篇 |
2008年 | 61篇 |
2007年 | 49篇 |
2006年 | 47篇 |
2005年 | 42篇 |
2004年 | 47篇 |
2003年 | 40篇 |
2002年 | 28篇 |
2001年 | 19篇 |
2000年 | 24篇 |
1999年 | 19篇 |
1998年 | 37篇 |
1997年 | 29篇 |
1996年 | 23篇 |
1995年 | 18篇 |
1994年 | 26篇 |
1993年 | 17篇 |
1992年 | 23篇 |
1990年 | 18篇 |
1989年 | 17篇 |
1988年 | 9篇 |
1987年 | 10篇 |
1986年 | 10篇 |
1985年 | 15篇 |
1984年 | 8篇 |
1983年 | 14篇 |
1982年 | 12篇 |
1981年 | 11篇 |
1980年 | 7篇 |
1979年 | 11篇 |
1978年 | 9篇 |
1977年 | 8篇 |
1976年 | 10篇 |
1975年 | 6篇 |
1974年 | 4篇 |
1970年 | 7篇 |
排序方式: 共有1157条查询结果,搜索用时 15 毫秒
1.
Fernanda Montenegro Barbosa Camila Valdejane Silva de Souza Ellane Sabryna Ribeiro Paulo Roberto Medeiros de Azevedo Karla Suzanne Florentino da Silva Chaves Damasceno Larissa Mont'Alverne Juc Seabra 《Journal of Food Safety》2021,41(1):e12869
The aim of the study was to evaluate the overall hygienic–sanitary conditions of university hospitals foodservices and assess food safety knowledge and self‐reported practices of food handlers. A self‐administered questionnaire based on sanitary standards for foodservices was given to 123 food handlers from three public hospitals. Microbiological analysis of food handling surfaces and food hygiene inspections were also performed. Food handlers' self‐reported knowledge and practices reached satisfactory levels (77.2% and 78.1%, respectively), and showed a significant positive intercorrelation (p < .05). Food hygiene inspections in the hospitals foodservices presented a 60.9% average of adequacy and microbiological analysis results showed that 66.7% of the evaluated surfaces presented significant contamination by mesophilic bacteria. The presence of coliforms at 45°C above the safety limit was identified in 47.9% of the surfaces. The results showed a need for motivating hospital food handlers to practice the safe handling knowledge that they have demonstrated in theory. 相似文献
2.
Dr. N. Amy Yewdall Bastiaan C. Buddingh Wiggert J. Altenburg Suzanne B. P. E. Timmermans Daan F. M. Vervoort Prof. Loai K. E. A. Abdelmohsen Dr. Alexander F. Mason Prof. Jan C. M. van Hest 《Chembiochem : a European journal of chemical biology》2019,20(20):2643-2652
The bottom-up construction of cell mimics has produced a range of membrane-bound protocells that have been endowed with functionality and biochemical processes reminiscent of living systems. The contents of these compartments, however, experience semidilute conditions, whereas macromolecules in the cytosol exist in protein-rich, crowded environments that affect their physicochemical properties, such as diffusion and catalytic activity. Recently, complex coacervates have emerged as attractive protocellular models because their condensed interiors would be expected to mimic this crowding better. Here we explore some relevant physicochemical properties of a recently developed polymer-stabilized coacervate system, such as the diffusion of macromolecules in the condensed coacervate phase, relative to in dilute solutions, the buffering capacity of the core, the molecular organization of the polymer membrane, the permeability characteristics of this membrane towards a wide range of compounds, and the behavior of a simple enzymatic reaction. In addition, either the coacervate charge or the cargo charge is engineered to allow the selective loading of protein cargo into the coacervate protocells. Our in-depth characterization has revealed that these polymer-stabilized coacervate protocells have many desirable properties, thus making them attractive candidates for the investigation of biochemical processes in stable, controlled, tunable, and increasingly cell-like environments. 相似文献
3.
4.
5.
6.
AbstractThe use of ‘social control’ interventions in housing and welfare policy often courts intense controversy, and never more so than when attempts are made to bring about change in the conduct of street homeless people. To date, academic scrutiny has focused on the so-called ‘regulation’ or ‘criminalisation’ of rough sleepers occupying public space, but a range of ‘softer’ control mechanisms are also now in evidence within homelessness support services. This paper explicates the relationship between the distinct forms of social control that have been used in this field – force, coercion, bargaining, influence and tolerance – and compares the perspectives of policy makers, frontline practitioners and homeless people regarding the appropriateness of their deployment in England. It emphasizes that the use of every one of these modes of social control, and indeed the absence of such controls, raises moral and practical dilemmas, the nuance of which is often unacknowledged in academic accounts. 相似文献
7.
A series of acrylamide‐based water‐soluble (co)polymers was synthesized and they were investigated as flocculants of model kaolin suspensions and mature fine tailings of oil sands. The effects of molar mass, charge density, and polymer concentration on flocculation efficiency were studied by monitoring the initial settling rate during sedimentation. Hydrolyzed polyacrylamide (HPAM) with high molar mass and intermediate acrylic acid contents (0.14–0.41 mol/mol (14–41 mol%)) performed better in flocculation tests on kaolin suspensions requiring lower dose for maximum initial settling rate than native polyacrylamide (PAM). Surface force measurements showed that at low polymer concentrations (1 ppm), the partially‐adsorbed polymer induced a bridging attraction between the mica surfaces. Increasing the polymer concentration to 10 and 50 ppm caused purely repulsive forces. The presence of anionic groups in HPAM led to stronger repulsion, which was also demonstrated by the higher viscosity and larger hydrodynamic radius of the charged polymer. The charge‐induced increase in the viscosity of polymer solutions was suppressed by the screening effect of salts in a buffer solution and reducing the viscosity is desirable in the injection of flocculants in the industrial process. 相似文献
8.
Tributary confluences are dynamic thermal refuges for a juvenile salmonid in a warming river network
Terrance Wang Suzanne J. Kelson George Greer Sally E. Thompson Stephanie M. Carlson 《河流研究与利用》2020,36(7):1076-1086
As rivers warm, cold‐water fish species may alleviate thermal stress by moving into localized thermal refuges such as cold‐water plumes created by cool tributary inflows. We quantified use of two tributary confluence plumes by juvenile steelhead, Oncorhynchus mykiss, throughout the summer, including how trout positioned themselves in relation to temperature within confluence plumes. At two confluences, Cedar and Elder creeks, along the South Fork Eel River, California, USA, we monitored temperatures using in situ logger grids throughout summer 2016. Fish were counted within confluences via snorkel surveys five times a day on 5 days at each site. We found diel and seasonal dependence on confluence use by steelhead, especially at the Cedar Creek confluence, where mainstem temperatures exceeded 28°C. At this site, fish moved into the confluence on the warmest days and warmest times of the day. Fish observed within the Cedar Creek confluence plume were most common in locations between 20–22°C, rather than the coldest locations (14.5°C). At Elder Creek, where mainstem temperatures remained below 24°C, there was little relationship between mainstem temperature and steelhead presence in the confluence plume. At both sites, steelhead distribution within plumes was influenced by spatial variation of temperature and mean temperature in surveyed grid cells. Our results show that cool tributaries flowing into warmer mainstem reaches (over 24°C) likely create important thermal refuges for juvenile steelhead. As mainstem rivers warm with climate change, cool‐water tributary inputs may become more important for sustaining cold‐water salmonids near the southern end of their range. 相似文献
9.
Wendy S. Smith David A. Johnston Harrison J. Wensley Suzanne E. Holmes Sopsamorn U. Flavell David J. Flavell 《International journal of molecular sciences》2020,21(22)
Cholesterol seems to play a central role in the augmentation of saporin-based immunotoxin (IT) cytotoxicity by triterpenoid saponins. Endolysosomal escape has been proposed as one mechanism for the saponin-mediated enhancement of targeted toxins. We investigated the effects of lipid depletion followed by repletion on Saponinum album (SA)-induced endolysosomal escape of Alexa Fluor labelled saporin and the saporin-based immunotoxin OKT10-SAP, directed against CD38, in Daudi lymphoma cells. Lipid deprived cells showed reduced SA-induced endolysosomal escape at two concentrations of SA, as determined by a flow cytometric method. The repletion of membrane cholesterol by low density lipoprotein (LDL) restored SA-induced endolysosomal escape at a concentration of 5 µg/mL SA but not at 1 µg/mL SA. When LDL was used to restore the cholesterol levels in lipid deprived cells, the SA augmentation of OKT10-SAP cytotoxicity was partially restored at 1 µg/mL SA and fully restored at 5 µg/mL SA. These results suggest that different mechanisms of action might be involved for the two different concentrations of SA and that endosomal escape may not be the main mechanism for the augmentation of saporin IT cytotoxicity by SA at the sub-lytic concentration of 1 µg/mL SA. 相似文献
10.
This paper examines the exposure to homelessness of socially marginalised groups to understand better the applicability of, and limits to, welfare regime analysis. A vignette methodology is deployed in six European countries to interrogate and compare responses to marginalised groups at high risk of homelessness, including people with substance misuse problems, ex-offenders, young people excluded from the family home, migrants and women fleeing domestic violence. Evidence suggests that a range of values embedded in national political cultures—including familialism, social cohesion, individuality, personal responsibility and personal liberty, as well as egalitarianism—impact on models of intervention and outcomes for specific marginalised groups in ways which cannot be straightforwardly predicted from conventional welfare regime analysis. 相似文献