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   136篇
  免费   6篇
  国内免费   1篇
电工技术   1篇
化学工业   60篇
金属工艺   3篇
机械仪表   2篇
建筑科学   7篇
能源动力   1篇
轻工业   19篇
水利工程   1篇
无线电   6篇
一般工业技术   29篇
冶金工业   4篇
自动化技术   10篇
  2023年   3篇
  2022年   17篇
  2021年   11篇
  2020年   5篇
  2019年   3篇
  2018年   4篇
  2017年   1篇
  2016年   1篇
  2015年   4篇
  2014年   4篇
  2013年   10篇
  2012年   14篇
  2011年   11篇
  2010年   4篇
  2009年   9篇
  2008年   9篇
  2007年   10篇
  2006年   3篇
  2005年   3篇
  2004年   2篇
  2003年   2篇
  2002年   1篇
  2001年   2篇
  2000年   2篇
  1998年   1篇
  1997年   2篇
  1996年   1篇
  1976年   2篇
  1967年   2篇
排序方式: 共有143条查询结果,搜索用时 15 毫秒
31.
Lanthanide‐induced enhancement of the longitudinal relaxation of nitroxide radicals in combination with orthogonal site‐directed spin labeling is presented as a systematic distance measurement method intended for studies of bio‐macromolecules and bio‐macromolecular complexes. The approach is tested on a water‐soluble protein (T4‐lysozyme) for two different commercially available lanthanide labels, and complemented by previously reported data on a membrane‐inserted polypeptide. Single temperature measurements are shown to be sufficient for reliable distance determination, with an upper measurable distance limit of about 5–6 nm. The extracted averaged distances represent the closest approach in LnIII–nitroxide distance distributions. Studies of conformational changes and of bio‐macromolecule association‐dissociation are proposed as possible application area of the relaxation‐enhancement‐based distance measurements.  相似文献   
32.
Hypertensive disorders of pregnancy are a major cause of poor outcome, including placental abruption, organ failure, cerebrovascular accident and disseminated intravascular coagulation. These disorders are associated with increased fetal risk of intrauterine growth restriction, intrauterine death and prematurity. Electrocardiography (ECG) recently emerged as a useful tool to evaluate cardiovascular complications during pregnancy. Specifically, left atrial abnormalities detected by standard ECG are associated with a fourfold increased risk of developing hypertensive disorders during pregnancy. The mechanisms linking left atrial abnormality on ECG with hypertensive disorders are still elusive. Several mechanisms, possibly reflected by abnormal left atrial activation on ECG, has been suggested. These include increased reactivity to angiotensin II and up-regulation of angiotensin type 1 receptors, with activation of autoantibodies targeting these receptors.  相似文献   
33.
Despite ongoing clinical trials, the efficacy of anti-angiogenic drugs for the treatment of brain metastases (BM) is still questionable. The lower response rate to anti-angiogenic therapy in the presence of BM than in metastatic disease involving other sites suggests that BM may be insensitive to these drugs, although the biological reasons underlining this phenomenon are still to be clarified. With the aim of assessing whether the targets of anti-angiogenic therapies are actually present in BM, in the present study, we analyzed the microvessel density (MVD), a measure of neo-angiogenesis, and the vascular phenotype (mature vs. immature) in the tumor tissue of a series of BM derived from different primary tumors. By using immunohistochemistry against endoglin, a specific marker for newly formed vessels, we found that neo-angiogenesis widely varies in BM depending on the site of the primary tumor, as well as on its histotype. According to our results, BM from lung cancer displayed the highest MVD counts, while those from renal carcinoma had the lowest. Then, among BM from lung cancer, those from large cell and adenocarcinoma histotypes had significantly higher MVD counts than those originating from squamous cell carcinoma (p = 0.0043; p = 0.0063). Of note, MVD counts were inversely correlated with the maturation index of the endoglin-stained vessels, reflected by the coverage of smooth muscle actin (SMA) positive pericytes (r = −0.693; p < 0.0001). Accordingly, all the endoglin-positive vessels in BM from pulmonary squamous cell carcinoma and renal carcinoma, displayed a mature phenotype, while vessels with an immature phenotype were found in highly vascularized BM from pulmonary large cell and adenocarcinoma. The low MVD and mature phenotype observed in BM from some primary tumors may account for their low sensitivity to anti-angiogenic therapies. Although our findings need to be validated in correlative studies with a clinical response, this should be taken into account in therapeutic protocols in order to avoid the adverse effects of useless therapies.  相似文献   
34.
35.
Obesity is a chronic, complex pathology associated with a risk of developing secondary pathologies, including cardiovascular diseases, cancer, type 2 diabetes (T2DM) and musculoskeletal disorders. Since skeletal muscle accounts for more than 70% of total glucose disposal, metabolic alterations are strictly associated with the onset of insulin resistance and T2DM. The present study relies on the proteomic analysis of gastrocnemius muscle from 15 male and 15 female C56BL/J mice fed for 14 weeks with standard, 45% or 60% high-fat diets (HFD) adopting a label-free LC–MS/MS approach followed by bioinformatic pathway analysis. Results indicate changes in males due to HFD, with increased muscular stiffness (Col1a1, Col1a2, Actb), fiber-type switch from slow/oxidative to fast/glycolytic (decreased Myh7, Myl2, Myl3 and increased Myh2, Mylpf, Mybpc2, Myl1), increased oxidative stress and mitochondrial dysfunction (decreased respiratory chain complex I and V and increased complex III subunits). At variance, females show few alterations and activation of compensatory mechanisms to counteract the increase of fatty acids. Bioinformatics analysis allows identifying upstream molecules involved in regulating pathways identified at variance in our analysis (Ppargc1a, Pparg, Cpt1b, Clpp, Tp53, Kdm5a, Hif1a). These findings underline the presence of a gender-specific response to be considered when approaching obesity and related comorbidities.  相似文献   
36.
The aim of this work was the nutritional evaluation of reformulated dairy products (caciotta-type cheese) and manufactured either with a low-sodium chloride content (different salting time and/or composition of the brine) or low-fat content (different partially skimmed milks). These cheeses were intended for people on low-energy or low-sodium diets. A comparison was made between these new products and three typical Italian cheeses (Provolone, Taleggio and Pecorino Romano). The nutrient content of the products was determined. Amino acids by chromatographic methods, protein digestibility by an enzymatic method and lysine availability determined spectrophotometrically were shown not to be influenced by the salt reduction. The salt reduction also did not affect vitamin contents (riboflavin, retinols, carotenes and tocopherols) measured by HPLC methods, while the reduced fat contents (310 g kg-1, 160 g kg-1 and 87 g kg-1) led to significant decreases in concentrations of fat-soluble vitamins (38% for tocopherols and 7% for total retinols) and a decrease in riboflavin (13%) due to the loss of riboflavin enzymes located on the fat globules (ie xanthine oxidase). Both the typical cheeses and the new formulations represent good sources of calcium and protein. Protein digestibility was affected by the ripening time; in fact, in Pecorino Romano, ripened for 6–9 months it reached 62% in 6 h, whereas in Taleggio and in all caciotta–cheeses it reached only 32–37%. The nutritional profiles of the reformulated caciotta cheese showed that these products could represent a good choice in low-energy and low-sodium diets, but an enrichment of fat-soluble vitamins is advisable in the low-fat products. © 1997 SCI.  相似文献   
37.
Heterogeneous Photooxidation of Phenol by Catalytic Membranes   总被引:1,自引:0,他引:1  
In this work the heterogenization in polymeric membranes of decatungstate, a photocatalyst for oxidation reactions, was reported. Solid state characterization techniques confirmed that the catalyst structure was preserved within the polymeric membranes. The catalytic membranes were successfully applied in the aerobic photo-oxidation of phenol, one of the main organic pollutants in wastewater, providing stable and recyclable photocatalytic systems. The dependence of the phenol degradation rate by the catalyst loading and transmembrane pressure was shown. By comparison with homogeneous reaction, the catalyst heterogenised in membrane appears to be more efficient concerning the rate of phenol photodegradation and mineralization.  相似文献   
38.
In recent years, planet exploration has received an increasing interest due to the possibility of exploiting planet resources and assuring a human–robotic colonized presence on suitable planetary surfaces. These goals can be reached through the development of smart robots, which are able to work on their own and without requiring a constant human supervision but, at the same time, assuring a great level of safety and reliability. To this aim, the development of effective architectures, concerning both software and hardware issues, could represent a great improvement toward this ambitious objective. This paper presents a novel modular architecture called Test Bench for Robotics and Autonomy (TBRA), the main objective of which is to create a test bench for rover autonomy missions where different implementations of a particular subsystem can be easily tested, while keeping the rest of the system unchanged. Thus, it allows the developers to be able to compare the results of tests and understand which version works better. Such architecture has been built on top of the Workframe, a generic middleware for real-time robotics. This two-layered approach allows the final user to deal only with the TBRA interface, which is designed to be extremely simple to use and takes care of most real-time programming problems, while allowing flexibility in the development, maintenance and future extension of the TBRA itself.  相似文献   
39.
The aim of this study is to evaluate a new neural network classifier using spectrally sampled image data to map mixed halophytic vegetation in tidal environments. The work is based on the concept of vegetation communities, mixtures of several species, characteristic of salt marshes. The study site is the Venice lagoon, and the material available is a spectrally sampled Compact Airborne Spectral Imager (CASI) image, in conjunction with ground truth for precise characterization of vegetation communities. Detailed observations of vegetation species and of their fractional abundance were collected for 36 Regions Of Interest (ROI): such field polygons are used for classification training and accuracy assessment. To select the most significant spectral channels, the Spectral Reconstruction method was applied to the image data: a set of 6 bands was selected as optimal for classification, out of the 15 available. The spatial heterogeneity of salt-marsh vegetation is significant and even at the spatial resolution of the airborne CASI image data, mixed pixels are observed. The Vegetation Community based Neural Network Classifier (VCNNC) is introduced to cope with a situation where no pure pixels exist, and was applied to the set of 6 selected bands. Both quantitative and qualitative comparisons of classification results of VCNNC with those of conventional Neural Network Classifier (NNC), trained and assessed on exactly the same data sets, shows that VCNNC's accuracy is substantially higher (≈ 91%) than that of NNC (≈ 84%), while the Kappa coefficient is 0.87 for VCNNC and 0.75 for the NNC method.  相似文献   
40.
Bioactivity of degradable polymer sutures coated with bioactive glass   总被引:1,自引:0,他引:1  
Novel bioactive materials have been prepared by coating violet resorbable Vicryl sutures with a bioactive glass powder derived from a co-precipitation method. Two techniques have been chosen for the composite preparation: pressing the sutures in a bed of glass powder and slurry-dipping of sutures in liquid suspensions of bioactive glass powders. The uniformity and thickness of the coatings obtained by the two methods were compared. The bioactivity of the sutures with and without bioactive glass coating was tested by soaking in an inorganic acellular simulated body fluid (SBF). The composite sutures were characterised by XRD, SEM and FTIR analyses before and after soaking in SBF solution to assess the formation of hydroxyapatite on their surfaces, which is a qualitative measure of their bioactivity. The possible use of bioactive sutures to produce tissue engineering scaffolds and as reinforcement of resorbable calcium phosphates is discussed.  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