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   582篇
  免费   40篇
电工技术   7篇
化学工业   116篇
金属工艺   8篇
机械仪表   4篇
建筑科学   17篇
矿业工程   4篇
能源动力   6篇
轻工业   86篇
水利工程   7篇
无线电   39篇
一般工业技术   97篇
冶金工业   139篇
原子能技术   1篇
自动化技术   91篇
  2023年   1篇
  2022年   6篇
  2021年   20篇
  2020年   9篇
  2019年   7篇
  2018年   14篇
  2017年   15篇
  2016年   13篇
  2015年   17篇
  2014年   17篇
  2013年   21篇
  2012年   16篇
  2011年   18篇
  2010年   24篇
  2009年   22篇
  2008年   20篇
  2007年   26篇
  2006年   21篇
  2005年   24篇
  2004年   14篇
  2003年   17篇
  2002年   17篇
  2001年   12篇
  2000年   12篇
  1999年   18篇
  1998年   49篇
  1997年   17篇
  1996年   19篇
  1995年   20篇
  1994年   11篇
  1993年   21篇
  1992年   10篇
  1991年   9篇
  1990年   6篇
  1989年   8篇
  1988年   8篇
  1987年   11篇
  1986年   7篇
  1985年   1篇
  1983年   1篇
  1982年   2篇
  1979年   4篇
  1977年   2篇
  1976年   6篇
  1974年   2篇
  1972年   1篇
  1971年   1篇
  1970年   2篇
  1967年   2篇
  1966年   1篇
排序方式: 共有622条查询结果,搜索用时 15 毫秒
11.
The muscular dystrophies are a large and heterogeneous group of neuromuscular disorders that can be classified according to the mode of inheritance, the clinical phenotype and the molecular defect. To better understand the pathological mechanisms of dysferlin myopathy we compared the protein-expression pattern in the muscle biopsies of six patients with this disease with six patients with limb girdle muscular dystrophy 2A, five with facioscapulohumeral dystrophy and six normal control subjects. To investigate differences in the expression levels of skeletal muscle proteins we used 2-DE and MS. Western blot or immunohistochemistry confirmed relevant results. The study showed specific increase expression of proteins involved in fast-to-slow fiber type conversion (ankyrin repeat protein 2), type I predominance (phosphorylated forms of slow troponin T), sarcomere stabilization (actinin-associated LIM protein), protein ubiquitination (TRIM 72) and skeletal muscle differentiation (Rho-GDP-dissociation inhibitor ly-GDI) in dysferlin myopathy. As anticipated, we also found differential expression of proteins common to all the muscular dystrophies studied. This comparative proteomic analysis suggests that in dysferlin myopathy (i) the type I fiber predominance is an active process of fiber type conversion rather than a selective loss of type II fibers and (ii) the dysregulation of proteins involved in muscle differentiation further confirms the role of dysferlin in this process.  相似文献   
12.
Over the last decade 3D face models have been extensively used in many applications such as face recognition, facial animation and facial expression analysis. 3D Morphable Models (MMs) have become a popular tool to build and fit 3D face models to images. Critical to the success of MMs is the ability to build a generic 3D face model. Major limitations in the MMs building process are: (1) collecting 3D data usually involves the use of expensive laser scans and complex capture setups, (2) the number of available 3D databases is limited, and typically there is a lack of expression variability and (3) finding correspondences and registering the 3D model is a labor intensive and error prone process.  相似文献   
13.
In an organisational setting such as an online marketplace, an entity called the ‘organisation’ or ‘institution’ defines interaction protocols, monitors agent interaction, and intervenes to enforce the interaction protocols. The organisation might be a software system that thus regulates the marketplace, for example. In this article we abstract over application-specific protocols and consider commitment lifecycles as generic interaction protocols. We model interaction protocols by explicitly-represented norms, such that we can operationalise the enforcement of protocols by means of norm enforcement, and we can analyse the protocols by a logical analysis of the norms. We adopt insights and methods from commitment-based approaches to agent interaction as well as from norm-based approaches to agent behaviour governance. First, we show how to use explicitly-represented norms to model commitment dynamics (lifecycles). Second, we introduce an operational semantics to operationalise norm enforcement. Third, we show how to logically analyse interaction protocols by means of commitment dynamics and norm enforcement. The model, semantics, and analysis are illustrated by a running example from a vehicle insurance domain.  相似文献   
14.
15.
Although lexicographic (lex) variants of greedy algorithms are often P -complete, NC -algorithms are known for the following lex-search problems: lexicographic depth-first search (lex-dfs) for dags [12], [17], lexicographic breadth-first search (lex-bfs) for digraphs [12], [17], and lexicographic topological-first search (lex-tfs) for dags [12]. For the all-sources version of the problem for dense digraphs, the lex-dfs (lex-bfs, lex-tfs) in [12] is (within a log factor of) work-optimal with respect to the all-sources sequential solution that performs a dfs (bfs, tfs) from every vertex. By contrast, to solve the single-source lexicographic version on inputs of size n , all known NC -algorithms perform work that is at least an n factor away from the work performed by their sequential counterparts. We present parallel algorithms that solve the single-source version of these lex-search problems in O(log  2 n) time using M(n) processors on the EREW PRAM. (M(n) denotes the number of processors required to multiply two n\times n integer matrices in O(log  n) time and has O(n 2.376 ) as tightest currently known bound.) They all offer a polynomial improvement in work-efficiency over that of their corresponding best previously known and close the gap between the requirements of the best known parallel algorithms for the lex and the nonlex versions of the problems. Key to the efficiency of these algorithms is the novel idea of a lex-splitting tree and lex-conquer subgraphs of a dag G from source s . These structures provide a divide-and-conquer skeleton from which NC -algorithms for several lexicographic search problems emerge, in particular, an algorithm that places in the class NC the lex-dfs for reducible flow graphs—an interesting class of graphs which arise naturally in connection with code optimization and data flow analysis [4], [19]. A notable aspect of these algorithms is that they solve the lex-search problem instance at hand by efficiently transforming solutions of appropriate instances of (nonlex) path problems. This renders them potentially capable of transferring significant algorithmic advances—such as Driscoll et al.'s [14] single-source shortest paths algorithm and Ullman and Yannakakis' [34] transitive closure algorithm—from fundamental (nonlex) path problems to lex-search problems. Received January 9, 1994, and in revised form November 1997. Online publication July 20, 2001.  相似文献   
16.
Results of a room temperature magnetic refrigeration test bed and an analysis using a computational model are presented. A detailed demonstration of the four sequential processes in the transient magnetocaloric regeneration process of a magnetic material is presented. The temperature profile during the transient approach to steady state operation was measured in detail. A 5 °C evolution of the difference of temperature between the hot end and the cold end of the magnetocaloric bed due to regeneration is reported. A model is developed for the heat transfer and fluid mechanics of the four sequential processes in each cycle of thermal wave propagation in the regenerative bed combined with the magnetocaloric effect. The basic equations that can be used in simulation of magnetic refrigeration systems are derived and the design parameters are discussed.  相似文献   
17.
SmartBone® (SB) is a biohybrid bone substitute advantageously proposed as a class III medical device for bone regeneration in reconstructive surgeries (oral, maxillofacial, orthopedic, and oncology). In the present study, a new strategy to improve SB osteoinductivity was developed. SB scaffolds were loaded with lyosecretome, a freeze-dried formulation of mesenchymal stem cell (MSC)-secretome, containing proteins and extracellular vesicles (EVs). Lyosecretome-loaded SB scaffolds (SBlyo) were prepared using an absorption method. A burst release of proteins and EVs (38% and 50% after 30 min, respectively) was observed, and then proteins were released more slowly with respect to EVs, most likely because they more strongly adsorbed onto the SB surface. In vitro tests were conducted using adipose tissue-derived stromal vascular fraction (SVF) plated on SB or SBlyo. After 14 days, significant cell proliferation improvement was observed on SBlyo with respect to SB, where cells filled the cavities between the native trabeculae. On SB, on the other hand, the process was still present, but tissue formation was less organized at 60 days. On both scaffolds, cells differentiated into osteoblasts and were able to mineralize after 60 days. Nonetheless, SBlyo showed a higher expression of osteoblast markers and a higher quantity of newly formed trabeculae than SB alone. The quantification analysis of the newly formed mineralized tissue and the immunohistochemical studies demonstrated that SBlyo induces bone formation more effectively. This osteoinductive effect is likely due to the osteogenic factors present in the lyosecretome, such as fibronectin, alpha-2-macroglobulin, apolipoprotein A, and TGF-β.  相似文献   
18.
The El Sancho reservoir is located in the Odiel River basin, which crosses the Iberian Pyrite Belt. The reservoir receives acid mine drainage (AMD) from the Meca River, a tributary of the Odiel River. Two multi-parameter probes, one placed at the tail (up-gradient) end of the reservoir, where the contaminants enter, and another close to the reservoir dam were used to characterize acidity migration through the Sancho reservoir. The probes both measured pH and conductivity every 30 min. Two different levels of contamination were found, due to dilution that takes place within the reservoir and changes in the AMD composition. The cross-correlation function allowed quantification of the migration process from tail to dam. For both pH and conductivity, the maximum correlation occurred 17 days after sampling, indicating a mean transit time of 17 days. Since the distance between the two sampling points was 14,500 m, the contaminant transit speed was 0.0098 m/s.  相似文献   
19.
Spices are parts of plants that due to their properties are used as colorants, preservatives, or medicine. The uses of spices have been known since long time, and the interest in the potential of spices is remarkable due to the chemical compounds contained in spices, such as phenylpropanoids, terpenes, flavonoids, and anthocyanins. Spices, such as cumin (cuminaldehyde), clove (eugenol), and cinnamon (cinnamaldehyde) among others, are known and studied for their antimicrobial and antioxidant properties due to their main chemical compounds. These spices have the potential to be used as preservatives in many foods namely in processed meat to replace chemical preservatives. Main chemical compounds in spices also confer other properties providing a variety of applications to spices, such as insecticidal, medicines, colorants, and natural flavoring. Spices provide beneficial effects, such as antioxidant activity levels that are comparable to regular chemical antioxidants used so they can be used as a natural alternative to synthetic preservatives. In this review, the main characteristics of spices will be described as well as their chemical properties, different applications of these spices, and the advantages and disadvantages of their use.  相似文献   
20.
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