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   247篇
  免费   21篇
  国内免费   2篇
电工技术   2篇
化学工业   85篇
金属工艺   4篇
机械仪表   4篇
建筑科学   7篇
能源动力   13篇
轻工业   60篇
水利工程   1篇
石油天然气   1篇
无线电   12篇
一般工业技术   43篇
冶金工业   11篇
原子能技术   2篇
自动化技术   25篇
  2024年   4篇
  2023年   6篇
  2022年   8篇
  2021年   13篇
  2020年   11篇
  2019年   9篇
  2018年   15篇
  2017年   14篇
  2016年   11篇
  2015年   10篇
  2014年   7篇
  2013年   30篇
  2012年   23篇
  2011年   25篇
  2010年   14篇
  2009年   7篇
  2008年   7篇
  2007年   9篇
  2006年   14篇
  2005年   6篇
  2004年   7篇
  2003年   1篇
  2002年   3篇
  2000年   1篇
  1999年   1篇
  1998年   4篇
  1996年   2篇
  1995年   1篇
  1994年   3篇
  1990年   1篇
  1989年   1篇
  1976年   1篇
  1975年   1篇
排序方式: 共有270条查询结果,搜索用时 0 毫秒
81.
Perception of universal facial beauty has long been debated amongst psychologists and anthropologists. In this paper, we perform experiments to evaluate the extent of universal beauty by surveying a number of diverse human referees to grade a collection of female facial images. Results obtained show that there exists a strong central tendency in the human grades, thus exhibiting agreement on beauty assessment. We then trained an automated classifier using the average human grades as the ground truth and used it to classify an independent test set of facial images. The high accuracy achieved proves that this classifier can be used as a general, automated tool for objective classification of female facial beauty. Potential applications exist in the entertainment industry, cosmetic industry, virtual media, and plastic surgery.  相似文献   
82.
Introduction Severe nephrotic syndrome is associated with increased morbidity and mortality. Renal artery embolization (RAE) has been used in a number of renal diseases such as renal tumors, arteriovenous fistulas etc. However, data regarding benefits of RAE in patients with symptomatic severe proteinuria is limited. We decided to evaluate role of RAE in the setting of severe symptomatic nephrotic syndrome. Methods Eight patients who had undergone transcatheter renal artery embolization with polyvinyl alcohol (PVA) were included. Clinico‐demographic characteristics as well as baseline laboratory data including level of proteinuria, serum albumin, C‐reactive protein and LDL cholesterol levels were recorded for each patient. After RAE, outpatient clinic control laboratory values were also assessed. Findings All patients except one underwent bilateral RAE (four simultaneous or three sequential). Two patients experienced postembolization syndrome characterized by flank pain, fever, and leukocytosis, which was self‐limited and responded to analgesics in all patients. There was no technical complications associated with RAE procedure. All patients became anuric except one. Serum albumin levels increased and serum LDL‐cholesterol levels decreased considerably in treated patients. Discussion Renal artery embolization with the purpose of amelioration in nephrotic syndrome complications was effective and free of major technical complications in our patients.  相似文献   
83.
Internet contributes to the development of science and facilitates scientific demeanors while it also serves as a ground for academic misdemeanors. Recent studies indicate that Internet facilitates and spreads academic dishonesty. The purpose of the current study is to investigate the extent of involvement of Turkish university students in academic dishonesty practices facilitated through Internet (i.e. e-dishonesty) and to question the conditions which lead to e-dishonesty. Three hundred and forty nine education faculty students from the most populated state university in Turkey were administered two Likert-Scale questionnaires developed by the researchers. After the reliability and validity conditions were met, two exploratory factor analyses were conducted. The first one revealed the factors constituting common types of e-dishonesty among undergraduate students which were fraudulence, plagiarism, falsification, delinquency, and unauthorized help. The second factor analysis exhibited individual and contextual factors triggering e-dishonesty which were named as individual factors, institutional policies and peer pressure. Results of both analyses are discussed and suggestions for further research are provided.  相似文献   
84.
Polychelates were synthesized by the addition of aqueous solutions of copper(II), cadmium(II), and nickel(II) chlorides to aqueous solutions of poly(maleic anhydride‐alt‐acrylic acid) [poly(MA‐alt‐AA)] in different pH media. The thermal properties of poly(MA‐alt‐AA) and its metal complexes were investigated with thermogravimetry and differential scanning calorimetry (DSC) measurements. The polychelates showed higher thermal stability than poly(MA‐alt‐AA). The thermogravimetry of the polymer–metal complexes revealed variations of the thermal stability by complexation with metal ions. The relative thermal stabilities of the systems under investigation were as follows: poly(MA‐alt‐AA)–Cd(II) > poly(MA‐alt‐AA)–Cu(II) > poly(MA‐alt‐AA)–Ni(II) > poly(MA‐alt‐AA). The effects of pH on the complexation and gravimetric analysis of the polychelates were also studied. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3926–3930, 2006  相似文献   
85.
Poly(N‐isopropylacrylamide)s (PNIPAAM)s were synthesized via free‐radical polymerization using a ceric ammonium nitrate, Ce(IV)–α‐ω‐dihydroxy(polydimethylsiloxane) (Tegomer H‐Si 2111, PDMS) redox pair in hexane at 30°C in a nitrogen atmosphere. The dependence of the initiation and termination steps on the [NIPAAM]/[Ce(IV)] and [NIPAAM]/[PDMS] ratios were studied using gravimetry and FTIR, 1H‐NMR, UV‐vis, and GFAA spectroscopy techniques. Gravimetric results indicated that, in the case of high concentrations of PDMS, the percentage of the solid portions of the products decreased while the amount of the oligomeric NIPAAM chains increased, that is, as the amount of PDMS in hexane was increased, the number of the short NIPAAM chains having PDMS segments at the two ends, also increased. UV‐vis results showed that the LCST of PNIPAAM initiated with Ce(IV) alone was higher than those of the ones that were synthesized using common initiator systems such as an ammonium persulfate–N,N,N′,N′‐tetramethylethylenediamine redox pair and azobis(isobutyronitrile). Further, it was observed that both siloxane blocks and ? NH? groups forming coordination bonds with free Ce(IV) ions and/or metal–ligand complexes had an important effect on the aggregation process of the chains. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1248–1254, 2003  相似文献   
86.
In this study, first the pure polystyrenes (PS) with different molecular weights (350 × 103 and 500 × 103) have been modified by the chemical modification with succinic anhydride (SA), maleic anhydride (MA), and phthalic anhydride (PhA) and then the polystyrene based composites (CPS) prepared by addition of modified polystyrenes (MPS) into pure PS (with the molecular weight of 230 × 103) in weight % ratios of 90 : 10, 80 : 20, and 70 : 30. Ultrasonic measurements were performed on PS/MPS blends of different weight percent of MPSs by use of pulse echo method with 5-MHz frequency at room temperature. Elastic properties namely; longitudinal modulus (L), Young's modulus (E), bulk modulus (K) and shear modulus (G), Poisson's ratio (μ), and acoustic impedance (Z) were calculated from the ultrasonic velocities values measured and densities values obtained experimentally. Atomic force microscopy (AFM) has been used for determining the microstructure of composites. The variations of these parameters with increasing MPSs weight percentage content in PS/MPS from 10 to 30 have been discussed. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012  相似文献   
87.
The effects of combination of freezing and the use of antioxidant technology on the quality of frozen sardine fillets were investigated in terms of sensory, biochemical [thiobarbituric acid (TBA), total volatile basic nitrogen (TVB‐N), peroxide value (PV) and free fatty acids (FFA)] and microbiological analyses [total viable count (TVC)]. Fish were filleted and divided into three groups. The first group was used as the control (C) without rosemary extract, the second group was treated with 1% rosemary extracts for 2 min (R1) and the third was treated with 2% rosemary extracts for 2 min (R2). All groups were frozen at ?18 °C over the storage period of 6 months. The results obtained from this study showed that the combination of antioxidant and frozen storage resulted in significant reduction of bacterial growth and stabilised the biochemical characteristics, especially for R2. However, the use of antioxidant at the level of 2% (R2) gave a bitter taste according to sensory assessment whereas the panellists mostly preferred R1.  相似文献   
88.
Tamoxifen induces apoptosis (programmed cell death) in human erythroleukemia K562 cells. Nitric oxide synthase activity and expression increased in apoptotic cells by 315% and 280%, respectively, compared to controls. The specific inhibitor of nitric oxide synthase, L-NAME, protected K562 cells from tamoxifen-induced apoptosis, whereas the nitric oxide donor, sodium nitroprusside (SNP), potentiated the apoptotic effect of the drug. In addition, 5-lipoxygenase was activated by tamoxifen and the specific enzyme inhibitor, MK886, protected K562 cells against the drug. Conversely, the 5-lipoxygenase product, 5-hydroperoxyeicosatetraenoic acid, enhanced the tamoxifen-induced apoptosis. Finally, tamoxifen altered also membrane properties of K562 cells.  相似文献   
89.
Scheduling problems are becoming more and more complex everyday. This makes the current rules and algorithms difficult to comply with the requirements. New machines with the capabilities of processing more than one jobs is being developed. Sometimes one job is divided into parts and processed by more than one machine at the same time. These make the current algorithms insufficient. Artificial intelligence technologies, especially expert systems are proven to deal with such dynamic complex problems in several domains. In this study, an example of such a complex problem is introduced and knowledge-based scheduling for these kind of problems is elaborated with a real life industrial example.  相似文献   
90.
Adsorption of proteins on solid surfaces is widely studied because of its importance in various biotechnological, medical, and technical applications, e.g., biosensors, cardiovascular implants, and chromatography. Adsorption thermodynamics has been studied on the microbeads of N,N′‐diethylaminoethyl (DEAE) Dextran anion exchanger for the human serum albumin (HSA) at 25, 30, 35, 40, and 45°C. As a result, some thermodynamic parameters like Freundlich constants, thermodynamic equilibrium constant (KD), standard free energy changes (ΔGassoc), standard entropy changes (ΔSassoc), and standard enthalpy change (ΔHassoc) have been evaluated. Using the linear Van't Hoff plot, ΔHassoc value of the system for the interaction of bovine serum albumin (BSA)‐adsorbed crosslinked DEAE dextran microbeads was determined as 20.650 kJ/mol. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3942–3947, 2006  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