首页 | 官方网站   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   161篇
  免费   6篇
  国内免费   9篇
工业技术   176篇
  2023年   1篇
  2022年   4篇
  2021年   5篇
  2020年   3篇
  2019年   3篇
  2018年   5篇
  2017年   6篇
  2016年   3篇
  2015年   3篇
  2014年   4篇
  2013年   9篇
  2012年   8篇
  2011年   15篇
  2010年   8篇
  2009年   13篇
  2008年   10篇
  2007年   9篇
  2006年   6篇
  2005年   5篇
  2004年   3篇
  2003年   4篇
  2002年   4篇
  2001年   6篇
  2000年   4篇
  1999年   2篇
  1998年   14篇
  1997年   3篇
  1996年   2篇
  1995年   3篇
  1994年   3篇
  1993年   2篇
  1990年   1篇
  1989年   1篇
  1985年   1篇
  1976年   2篇
  1973年   1篇
排序方式: 共有176条查询结果,搜索用时 17 毫秒
91.
Estimation of Peak Flow Rates for Small Drainage Areas   总被引:1,自引:0,他引:1  
Runoff plots are important for soil loss measurements, and increasing numbers of plots use automatic equipment. To choose equipment with appropriate capacities, the peak flow rate must be known. The peak flow rate is also an important parameter in the modified universal soil loss equation (MUSLE) which calculate the soil loss from upland slope. The available peak flow rate equations are primarily for the watershed scale, not for small drainage areas like runoff plot. This study’s purpose was to derive an equation suitable for the small drainage areas. A total of 149 runoff events on 5 runoff plots were used to develop a peak flow rate equation for the hillslope scale. All plots are located in the Tuanshangou catchment, Zizhou county, Shaanxi province, China. Dimensionless analyses were used to determine the equation form of linear regression analyses. The results revealed that the peak flow rate was significantly correlated with plot area, slope steepness, runoff depth, rainfall depth and the maximum 30-min rainfall intensity. Two equations were developed to estimate peak flow. The model efficiencies of both equations exceeded 0.9. The equations developed in this study represent an important complement to existing peak flow rate equations. These new equations will facilitate the design of soil conservation practices and/or the selection of flow-observation equipment for small drainage areas.  相似文献   
92.
An experimental demonstration is given of a data-based multi-input multi-output (MIMO) feed-forward control design applied to the motion systems of a wafer scanner. Atop a nominal single-input single-output (SISO) feed-forward controller, a MIMO controller is designed having a finite impulse response (FIR) filter structure. The coefficients in this structure are obtained from a gradient approximation-based algorithm. The aid of the FIR filter structure is mostly through its efficient (and limited) set of perturbed-parameter experiments needed to obtain the FIR coefficients. The effectiveness of the optimized feed-forward design in achieving improved servo tracking performances is demonstrated on a high-speed and nano-accurate MIMO wafer stage of an industrial wafer scanner.  相似文献   
93.
In the past 30 years, staging and treatment of Hodgkin's disease have changed dramatically, and prolonged remission can now be induced in the majority of patients. Our purpose was to assess improvement in long-term survival, previously reported for specific patient groups, among unselected patients diagnosed and treated between 1972 and 1993 in general hospitals in South-East Netherlands. Data on all 345 Hodgkin's patients were derived from the population-based Eindhoven Cancer Registry; histopathology and clinical records were reviewed. Follow-up was attained up to 1994. Relative survival rates, i.e. the ratio of observed to expected rates, were 80% after 5, 70% after 10 and 67% after 15 years. Independent prognostic factors for lower overall survival were (in decreasing order of significance): advanced age, histology (lymphocyte depletion), advanced stage and earlier period of diagnosis. Distribution of age and stage did not change over the study period, but there was a modest increase in the incidence of the nodular sclerosis histological subtype. Crude 5-year survival rates improved from 60% in the period 1972-1976 to 81% in the period of 1987-1992 (P < 0.005). The largest improvement occurred in the 1970s and was most prominent among those aged over 50 years. As previously reported, cured Hodgkin's patients exhibit a higher mortality rate, which can be explained by treatment-related long-term complications such as second malignancies and cardiovascular diseases. The relatively high survival rates compared to other population-based studies may be attributable to the existence of a regional network within the framework of a comprehensive cancer centre. Better staging, new combinations of chemotherapy, improved radiation technology, advances in supportive care as well as more frequent intensive treatment of the elderly could explain the improvement in prognosis.  相似文献   
94.
Since prolonged remission can be induced in the majority of patients with Hodgkin's disease (HD), treatment-related mortality and morbidity have emerged. We investigated whether awareness of toxicity diminished treatment-related mortality for unselected patients treated between 1972 and 1993 in general hospitals in the southeastern Netherlands. We also estimated the prevalence of treatment-related morbidity among patients treated in the 1980s. Data were collected on all 345 HD patients registered in the Eindhoven Cancer Registry between 1972 and 1993. Medical records and histology were reviewed; follow-up ended in 1994. Administration of MOPP chemotherapy decreased, and there was a shift from total nodal irradiation to less extended low-dose radiotherapy. For cured patients the 10-year relative survival improved from 84% in the 1970s to 90% in the 1980s, which is reflected by a decline in excess mortality from 16% to 10%. The 10-year relative mortality risk due to secondary malignancies decreased from 4.3 (95% CI, 1.2-7.4) to 3.0 (CI 0.2-5.8), which is also reflected by a decline in the 10-year cumulative incidence for all cancers from 10% to 5%. However, the relative risk of late cardiovascular death, which is closely related to previous irradiation, barely changed, as shown by a decrease from 2.4 (CI 0.4-4.5) to 2.2 (CI.0-4.7). HD survivors profited less from the sharp decline in cardiovascular mortality observed for the general population. Among patients, the prevalence of serious treatment-related morbidity 5 years or more after initial diagnosis was 34%. In conclusion, modest decline in excess mortality among cured HD patients was observed in the 1980s, as reflected by a decrease in mortality due to second malignancies. However, late mortality, especially due to radiation-related cardiovascular disease, is still substantial. About one third of HD survivors suffer radiation-induced sequelae. Clinical trials to find ways to minimize iatrogenic complications are important.  相似文献   
95.
OBJECTIVE: To assess the effect of oestrogen (ER) and progesterone (PgR) receptors on the prognosis of patients with operable breast cancer and the decision to treat these patients with adjuvant tamoxifen. DESIGN: Retrospective. SETTING: Eight community hospitals in the Southeast Netherlands. METHOD: Using the registry of the Comprehensive Cancer Centre South, 2862 breast cancer patients were identified with stage I, II or IIIA tumours, treated during the period 1984-1992. RESULTS: ER and PgR status were known for 2393 (84%) and 1761 (62%) patients respectively. From 1991, over 80% of the postmenopausal, lymph node positive patients had received tamoxifen, irrespective of the steroid receptor status. Of all lymph node negative patients fewer than 3% received adjuvant systemic treatment. Among the lymph node negative patients the steroid receptor status was not a significant predictor of survival. Among the lymph node positive patients whose tumours were both ER-negative and PgR-negative, a 2.8-fold increased risk of death was found during the first four years after primary treatment. The risk of death was not increased if only the ER or only the PgR status was negative. CONCLUSION: This study shows that ER and PgR receptors are significant prognostic factors for survival in breast cancer patients with involved axillary lymph nodes. The prognostic effect appeared to be restricted to the first four years after primary treatment. Selection of patients for endocrine treatment should be based on the steroid receptor status, considering the importance of the steroid receptors for predicting the response to endocrine treatment.  相似文献   
96.
A sequentially coupled mathematical thermal-stress model, based on the commercial finite-element code ABAQUS, has been developed to rationalize crack defect formation in fused cast αβ-alumina refractories used in the glass industry. The thermal model was validated against thermocouple and pyrometer measurements obtained in an industrial setting. The temperature predictions obtained from the thermal model were employed as input to the elastic strain-rate-independent plastic stress model. The constitutive behavior of αβ-alumina has been determined over a range of temperatures for input to the stress model. The distribution of β-alumina that forms in the center of the casting due to rejection of Na2O during solidifcation was introduced in the stress model through a user-defined subroutine in order to account for the effect of differences in the thermal contraction behavior and elastic modulus of the αβ- and β-alumina phases. The stress analysis indicates that temperature gradients as well as the different dilatational behavior of the αβ- and β-alumina phases are the main drivers of stress and strain evolution during solidification and subsequent cooling. The β-alumina core, in particular, plays an important role in the generation of tensile stresses and likely gives rise to the generation of the internal cracks observed in industrial castings.  相似文献   
97.
The provisioning of wireless data services in the railway environment will become increasingly important for train operators and train constructors in the upcoming years. In this paper, we present models to predict train-to-wayside wireless data communications characteristics in terms of throughput, jitter, and packet loss predictions for 2G/3G networks. To this end, an extensive measurement campaign is carried out along a Belgian Intercity railway track. Based on these measurements, we apply a multiple regression, window mean, and autoregressive model. We find that the window mean model is recommended for the prediction of throughput and jitter, while the multiple regression model is more favorable for the prediction of packet loss. The implementation of these predictions in train-to-wayside communication systems can enhance the provisioning of seamless network connection necessary for a wide variety of data services.  相似文献   
98.
99.
In this study, a method was developed for the efficient entrapment of active tissue-type Plasminogen Activator (t-PA) into liposomes. Experimental conditions were varied to optimize t-PA entrapment: different buffer solutions were used (pH 4 and 7.5), the effect of the incubation concentrations of phospholipid (PL) and t-PA was monitored and the influence of liposome-size was examined. Furthermore, the effect of ultracentrifugation on t-PA containing liposomes was determined in the presence and absence of Tween 80. t-PA entrapment strongly depended on experimental conditions and ranged from 30 up to 90%. Almost quantitative+ (90%) entrapment (entrapment percentage defined as absolute entrapment (IU t-PA/mumol PL) divided by total incubation ratio (IU t-PA/mumol PL), times 100%) was obtained in Hepes buffer pH 7.5, devoid of arginine, with low ionic strength. Ultracentrifugation, used for removal of non-entrapped t-PA, was shown to have a damaging effect on the liposomes (especially in the presence of 0.05% Tween 80), leading to t-PA loss. However, because acceptable alternatives were not available, ultracentrifugation was used during this study. Therefore, the encapsulation-percentage values shown in this study are in fact underestimates for the true entrapment of t-PA. In conclusion: almost quantitative t-PA entrapment in liposomes can be achieved by selecting the proper milieu and inducing a strong interaction between t-PA and bilayer.  相似文献   
100.
Photosensitizers used normally in treating cancers have considerable potential for treatment of other diseases. One such photosensitizer is the endogenously synthesized photosensitizer protoporphyrin IX (PpIX). To better understand how protoporphyrin might be used in transplantation or in treating autoimmune diseases, information must be obtained on how the photosensitizer affects all immune cells. We used a combination of flow cytometry and in vitro activation assays (recall assays and mixed-lymphocyte reactions) to examine the effects of PpIX on the antigen specific component, lymphocytes and the non-antigen specific component, the macrophages/monocytes and dendritic cells of the immune system. Whereas, lymphocytes accumulate PpIX only when activated, both macrophages and dendritic cells accumulated PpIX immediately, without in vitro activation, as measured by flow cytometry. ALA-PDT (aminolevulenic acid-photodynamic therapy) treated adherent cells in the recall assay had a decreased capability to activate lymphocytes. By increasing the light dose in the recall assay, antigen primed lymphocytes were selectively eliminated from a population of cells. Stimulator cells in an MLR had a decreased stimulatory capacity following ALA-PDT treatment. Functional alterations are seen in both the antigen specific  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

京公网安备 11010802026262号