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   309篇
  免费   4篇
电工技术   4篇
综合类   4篇
化学工业   104篇
金属工艺   3篇
机械仪表   7篇
建筑科学   25篇
能源动力   8篇
轻工业   45篇
水利工程   1篇
无线电   15篇
一般工业技术   44篇
冶金工业   17篇
原子能技术   5篇
自动化技术   31篇
  2025年   1篇
  2024年   6篇
  2023年   9篇
  2022年   23篇
  2021年   23篇
  2020年   16篇
  2019年   9篇
  2018年   2篇
  2017年   15篇
  2016年   9篇
  2015年   14篇
  2014年   8篇
  2013年   22篇
  2012年   11篇
  2011年   17篇
  2010年   10篇
  2009年   9篇
  2008年   14篇
  2007年   8篇
  2006年   11篇
  2005年   7篇
  2004年   7篇
  2003年   9篇
  2002年   12篇
  2001年   5篇
  2000年   4篇
  1999年   3篇
  1998年   4篇
  1997年   1篇
  1996年   3篇
  1995年   1篇
  1994年   1篇
  1993年   3篇
  1992年   1篇
  1990年   3篇
  1989年   1篇
  1987年   3篇
  1986年   2篇
  1985年   1篇
  1981年   2篇
  1978年   1篇
  1976年   2篇
排序方式: 共有313条查询结果,搜索用时 0 毫秒
61.
62.
A strain approach for the design of coated contacts is described, allowing a simple evaluation of the risk of coating failure, once the elastic modulus of the coating and the substrate and the coating thickness are known. Examples are provided for hard and soft coatings. The approach is shown to be particularly useful for hard coatings, where failure is mainly related to tensile longitudinal stresses at the interface. Results from the proposed strain approach compare well with data from a standard stress analysis. Finally, the level of approximation introduced by evaluating the strain field for the reference Hertzian case is discussed, showing that the error introduced is not acceptable.  相似文献   
63.
In temperate regions, legume-based green manures are a key element of organic rotations. However, specialized farms lack sufficient mobile organic fertilizers. To gain a better understanding of the N flows and the nitrogen (N) and phosphorus (P) fertilizer value of different clover-grass-based fertilizers (biogas digestate, compost, silage and fresh clover-grass obtained from clover-grass ley biomass), we assessed their fertilizer value. Nitrogen and P offtake by the ryegrass was used to assess the short-term effects. The data were completed using model calculations to assess the field-to-field N-transfer efficiencies and the overall N-transfer efficiencies. The greatest plant N offtake was achieved with digestates (64%) and the lowest from the compost (6%) and solid farmyard manure (14%). The mineralization rate was positively related to the NH4 +–N/total N ratio (P < 0.01, r2 = 0.82). The model calculations indicate that the overall short-term N-transfer efficiencies are driven by the field-to-field N-transfer efficiency and the field-to-crop transfer efficiency. However, in the long term, model calculations indicate that a high field-to-field N-transfer efficiency is the key strategic approach when aiming to achieve cropping systems with a high overall long-term N-transfer efficiency. Consequently, the results showed that aerobic decomposition (composting) significantly lowered field-to-field as well as field-to-crop N-transfer rates. The relative P use efficiency strongly differed among the fertilizers. In particular, freshly cut clover-grass and solid manure increased P availability and led to an increase of plant P offtake that was higher than the amount of P supplied.  相似文献   
64.
Little is known on both the composition and mechanism(s) of proteinuria associated with the use of mTOR inhibitors, in particular of Everolimus (E). We characterized urinary proteins utilizing an integrated proteomics approach (quantitative essays, 2‐DE, MALDI‐TOF, Western blot) in 48 renal transplant recipients who were alternatively treated with E (n = 31) or with enteric coated mycophenolic acid (EC‐MPA) (n = 17). Twelve E patients (39%) developed high (>3 g/day) or intermediate proteinuria (1–3 g) compared to four (23%) of the EC‐MPA group. Urinary proteins (p<0.001), β2 microglobulin (p<0.001) and α1microglobulin (p<0.025) were higher in E than in EC‐MPA, appeared more rapidly and were inversely correlated with the day of treatment. Proteomics showed a marked increase of all urinary components in E and EC‐MPA patients, major changes involving typical components of glomerular damage (albumin, α1‐Zn glycoprotein, α2HS glycoprotein, leucin‐richα2‐glycoprotein) and specific bio‐markers for E (clusters of α1‐antitrypsin fragments and monoclonal λ chains). Finally, inter‐α‐trypsin‐inhibitor heavy chain H4 precursor was decreased in E and EC‐MPA urine compared to normal urine. In conclusion, E induced massive and generalized proteinuria of mixed glomerular and tubular origin that was correlated with the start of treatment and reached a nephrotic range in few cases. Specific urinary markers reflect renal alterations related to the transplant or specific alterations associated with the drug.  相似文献   
65.
66.
The paper addresses the optimal design of the last supply chain branch, i.e., the Distribution Network (DN), starting from manufacturers till the retailers. It considers a distributed system composed of different stages connected by material links labeled with suitable performance indices. A hierarchical procedure employing direct graph (digraph) modeling, mixed integer linear programming, and the Analytic Hierarchy Process (AHP) is presented to select the optimal DN configuration. More in detail, a first-level DN optimization problem taking into account the definition and evaluation of the distribution chain performance provides a set of Pareto optimal solutions defined by digraph modeling. A second level DN optimization using the AHP method selects, on the basis of further criteria, the DN configuration from the Pareto face alternatives. To show the method effectiveness, the optimization model is applied to a case study describing an Italian regional healthcare drug DN. The problem solution by the proposed design method allows improving the DN flexibility and performance.  相似文献   
67.
Oat bran fermentation (OBF) is used to produce non-dairy yogurt-type products. Such products may be designed being rich in probiotic bacteria and/or dietary-fibre. Oat bran is, however, also rich in proteins, especially 12 S globulins. Understanding the behaviour of globulins in OBF would thus offer a basis for further exploitation of proteins in the product design. The behaviour of oat globulins was monitored during a model OBF in order to study changes in protein solubility and possible protein hydrolysis. Proteins were extracted from OBF samples with a buffered and a non-buffered extraction procedure. The extracts were analyzed with SDS-PAGE and a Lowry assay. Combined effect of pH and NaCl-concentration on the solubility of oat globulin isolate was studied. The solubility of oat globulins decreased during OBF; this appeared as their shift from the salt-soluble fraction to the residual protein fraction. The shift in oat globulin solubility was due to the acidifying conditions present in OBF, which lead to the unfolding of globulins and also apparently induced protein aggregation. No major protein hydrolysis was observed during OBF.  相似文献   
68.
69.
70.
We have analyzed the filamentous cyanobacterium Anabaena PCC 7120 (wildtype) containing one nitrogenase, one uptake hydrogenase and one bidirectional hydrogenase and its hydrogen uptake deficient mutant AMC 414 for their H2 production capacities. Anabaena PCC 7120 and AMC 414 had similar growth rates in turbidostat mode with increased growth rates at higher light intensity. Rates of C2H2 reduction were similar for both strains. In contrast to the wildtype, AMC 414 produced H2 in a PhotoBioReactor (PhBR) using air as the lifting gas. The rate of H2 production increased with light intensity and was not even saturated at 456 μEm−2 s−1. H2 production increased significantly when replacing the air with argon. The maximal H2 production during outdoor conditions was recorded using AMC 414 with a peak at 14.9 ml H2 h−1 l−1. Despite the relatively high production, maximal efficiency of solar energy to H2 conversion was only 0.042%. A molecular method was developed to analyze the relative abundancies of weight and mutant in competition experiments in the PhBR.  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