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   406篇
  免费   21篇
  国内免费   3篇
电工技术   12篇
化学工业   119篇
金属工艺   4篇
机械仪表   21篇
建筑科学   16篇
能源动力   18篇
轻工业   38篇
水利工程   1篇
石油天然气   9篇
无线电   33篇
一般工业技术   79篇
冶金工业   32篇
原子能技术   1篇
自动化技术   47篇
  2024年   1篇
  2023年   8篇
  2022年   25篇
  2021年   20篇
  2020年   9篇
  2019年   43篇
  2018年   16篇
  2017年   21篇
  2016年   15篇
  2015年   8篇
  2014年   19篇
  2013年   42篇
  2012年   15篇
  2011年   24篇
  2010年   23篇
  2009年   9篇
  2008年   11篇
  2007年   10篇
  2006年   11篇
  2005年   8篇
  2004年   9篇
  2003年   4篇
  2002年   5篇
  2001年   5篇
  2000年   3篇
  1999年   9篇
  1998年   11篇
  1997年   2篇
  1996年   9篇
  1995年   5篇
  1994年   5篇
  1993年   3篇
  1992年   2篇
  1991年   2篇
  1990年   2篇
  1989年   1篇
  1988年   1篇
  1984年   2篇
  1982年   1篇
  1981年   1篇
  1980年   1篇
  1978年   1篇
  1977年   3篇
  1976年   3篇
  1975年   1篇
  1960年   1篇
排序方式: 共有430条查询结果,搜索用时 46 毫秒
131.
A study has been done to consider Malaysian WCO (waste cooking oil) generated in an eco-tourism island, Langkawi, Malaysia as an alternative feedstock for biodiesel production. This paper presents the results of the comprehensive technical feasibility study for production of biodiesel from WCO feedstock. The results have shown feasibility of recycling WCO into biodiesel that is compliant with international fuel standard ASTM D6751. The study has given an indication on the appropriate processing scheme to be developed for recycling WCO into biodiesel as a substitute fuel for diesel vehicles in Langkawi that would enable the promotion of alternative fuel in the energy mix for long term environment sustainability.  相似文献   
132.
Transparent conductive oxide‐less (TCO‐less) dye‐sensitized solar cells (DSSCs) have been fabricated and characterized using nanoporous TiO2‐coated stainless steel metal mesh as flexible photoanode and cobalt bipyridyl complex (Co(bpy))‐based one electron redox shuttle electrolyte. Attempts have been made towards enhancing the efficiency of TCO‐less DSSCs to match with their TCO‐based DSSC counterparts. It has been found that surface protection of metal mesh is highly required for enhancing the efficiency of TCO‐less DSSCs specially using cobalt electrolytes as confirmed by dark current–voltage characteristics. Photocurrent action spectra clearly reveal that TCO‐based DSSCs using (Co(bpy)) electrolyte exhibits photon harvesting (incident photon to current conversion efficiency (IPCE) 52%) in the 370–450 nm wavelength region as compared to photon harvesting at peak absorption of the dye (IPCE 56% at 550 nm), which is almost the same (IPCE 47%) in the 400–610 nm wavelength region for TCO‐less DSSCs. Under similar experimental conditions, replacing indoline dye D‐205 to porphyrin‐based dye YD2‐o‐C8 led to the enhancement in the photoconversion efficiency from 3.33% to 4.84% under simulated solar irradiation. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   
133.
The structure, field-induced strain, polarization and dielectric response of lead-free SrZrO3-modified Bi1/2(Na0.80K0.20)1/2TiO3 (abbreviated as BNKT–SZ100x, with x = 0–0.05) ceramics were investigated. The X-ray diffraction analysis of BNKT–SZ100x ceramics reveals no remarkable change in the crystal structure within the studied composition range. Around critical composition (x = 0.03) at a driving field of 6 kV mm−1, large unipolar strain of 0.37% (Smax/Emax = 617) was obtained at room temperature. The ferroelectric and piezoelectric properties of BNKT ceramics were significantly increased at 2 mol%. At x = 0.02, remnant polarization reached a maximum value of 34 μC cm−2, while the piezoelectric constant (d33) attained maximum value of 190 pC/N. These results indicate that BNKT–SZ100x ceramics can be considered as promising candidate materials for lead-free piezoelectric actuator applications.  相似文献   
134.
A finite element software has been used to determine the temperature history in forming a TV glass panel during hot pressing in a metal mold and the controlled cooling cycle. The temperature history is then used to calculate the stress and strain history in the glass panel. The goal of the simulation model is to predict the resulting stresses and strains due to forming and cooling that takes place during the manufacturing of the TV panel. DEFORM 3D software has been used to carry out the numeric simulation.  相似文献   
135.
The analytical performance and practicability of the Boehringer Mannheim (BM)/Hitachi 911 analysis system have been assessed in a multicentre evaluation, which involved six laboratories from European countries. Analytes commonly used in classical clinical chemistry were tested in a core programme, which mainly followed the ECCLS guidelines. In addition, a satellite programme covered other analytes, such as proteins, drugs and urine analytes. In total, the study comprised more than 100 000 data items collected over a three-month period. The evaluation was supported with ‘Computer Aided Evaluation’ (CAEv) and telecommunications.Acceptance criteria for the results were established at the beginning of the study. Nearly all of the analytes met the imprecision limits: within-run imprecision (as CVs) was 2% for enzyme and substrate assays, 1% for ISE methods and 5% for immunoassays; between-day imprecision was 3l% for enzyme and substrate assays, 2% for ISE methods and 10% for immunoassays.No relevant drift effects (systematic deviation ≥ 3%) were observed over eight hours. The methods were linear over a wide range. Sample-related and reagent-dependent carry-over can be reduced to a negligible amount by integration of a softwarecontrolled wash-step.Endogenous interferences were found for creatinine (Jaffé method) and uric acid assays (caused by bilirubin), for creatine kinase, creatine kinase MB isoform and γ-glutamyltransferase (caused by haemoglobin), and for immunoglobulin A (caused by lipaemia)Accuracy was checked by an interlaboratory survey, recovery studies in control materials and method comparison studies. The survey showed that, with the exception of cholesterol and iron in two laboratories, the recovery of analytes did not deviate by more than 5%. Sixty-six of the 77 method comparisons performed met the acceptance criteria. The deviations of the remaining 11 results could be explained by differences in either calibration, application or by the use of different methods.Practicability was assessed using a questionnaire which covered all of the important aspects of an analysis system in the clinical laboratory. Twelve groups of attributes out of 14 were rater higher for the BM/Hitachi 911 than for the present situation in the laboratories concerned. Especially high scores were given for the versatility group.The acceptance criteria for the analytical performance of the BM/Hitachi 911 analysis system were fulfilled in all laboratory segments with few exceptions. The practicability exceeded the requirements in most of the attributes. The results of the study confirmed the usefulness of the system as a consolidated workstation in small- to medium-sized clinical laboratories and in STAT laboratories, or as an instrument for special analytes like proteins and drugs, or for urinalysis in large laboratories.  相似文献   
136.
We determined the expression of a newly recognized drug resistance gene, the multidrug resistance-associated protein (MRP) gene, [Cole et al., Science (Washington DC), 258: 1650-1654, 1992], in normal human tissues and in >370 human tumor biopsies using a quantitative RNase protection assay and immunohistochemistry. MRP mRNA appeared to be ubiquitously expressed at low levels in all normal tissues, including peripheral blood, the endocrine glands (adrenal and thyroid), striated muscle, the lymphoreticular system (spleen and tonsil), the digestive tract (salivary gland, esophagus, liver, gall bladder, pancreas, and colon), the respiratory tract (lung), and the urogenital tract (kidney, bladder, testis, and ovary). The human cancers analyzed could be divided into three groups with regard to MRP expression. Group 1 consists of tumors that often exhibit high to very high MRP mRNA levels (e.g., chronic lymphocytic leukemia). Group 2 comprises the tumors that often exhibit low, but occasionally exhibit high MRP mRNA expression (e.g., esophagus squamous cell carcinoma, non-small cell lung cancer, and acute myelocytic leukemia). Group 3 comprises the tumors with predominantly low levels of MRP mRNA, comparable to the levels found in normal tissues (e.g., other hematological malignancies, soft tissue sarcomas, melanoma, and cancers of the prostate, breast, kidney, bladder, testis, ovary, and colon). Using the MRP-specific mAbs MRPr1 and MRPm6, we confirmed the elevated MRP mRNA levels in tumor tissues by immunohistochemistry. We conclude that hyperexpression of MRP is observed in several human cancers, and that additional studies are needed to assess the clinical relevance of MRP.  相似文献   
137.
138.
An analysis procedure based on the finite element method is presented to solve moving-load problems of rigid pavements. The algorithm presented considers the dynamic pavement-aircraft interaction effects. The pavement-foundation system is modelled by thin-plate, non-conforming finite elements resting on a two-parameter elastic medium. The moving aircraft loads are represented by masses supported by a spring-dashpot system moving at a specified initial horizontal velocity and acceleration. The accuracy of the finite element program developed is verified by comparing the numerical results of a static problem with the available solution. A parametric study is conducted to determine the effects of the various parameters on the dynamic response of pavements. Emphasis is placed on identifying the influence of fictitious edge and corner forces acting on the plate due to the deformation of the soil medium outside the plate.  相似文献   
139.
Giardia lamblia trophozoites attach readily to dextran particles after which they can be conveniently processed for scanning electron microscopy. As the particles are spherical in shape, G. lamblia can be viewed from various directions and their morphology studied.  相似文献   
140.
OBJECTIVE: To investigate the effects of nonsteroidal antiinflammatory drug (NSAID) therapy and water immersion on hypothalamic-pituitary-adrenal (HPA) axis function in rheumatoid arthritis (RA). METHODS: Plasma levels of adrenocorticotropic hormone (ACTH) and serum and urine levels of cortisol were compared in untreated RA patients, NSAID-treated RA patients, and healthy control subjects. RESULTS: ACTH levels were significantly higher in untreated RA patients (mean +/- SEM integrated area 11,377 +/- 5,246 hours ng/liter) than in NSAID-treated RA patients (2,285 +/- 388 hours ng/liter) or healthy controls (1,845 +/- 35.5 hours ng/liter) (P < 0.001). Serum and urine cortisol levels were not significantly different between groups. Two-hour head-out water immersion had no effect. CONCLUSION: Elevated ACTH levels without hypercortisolemia occur in untreated RA. NSAID therapy alters HPA axis response, but immersion has no effect.  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