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   786篇
  免费   57篇
  国内免费   4篇
  847篇
  2022年   7篇
  2021年   10篇
  2020年   3篇
  2019年   14篇
  2018年   7篇
  2017年   12篇
  2016年   17篇
  2015年   29篇
  2014年   47篇
  2013年   50篇
  2012年   56篇
  2011年   51篇
  2010年   29篇
  2009年   38篇
  2008年   40篇
  2007年   40篇
  2006年   44篇
  2005年   45篇
  2004年   47篇
  2003年   56篇
  2002年   51篇
  2001年   13篇
  2000年   14篇
  1999年   11篇
  1998年   10篇
  1997年   9篇
  1996年   11篇
  1995年   7篇
  1994年   9篇
  1993年   2篇
  1992年   5篇
  1991年   3篇
  1990年   2篇
  1988年   5篇
  1987年   3篇
  1985年   1篇
  1984年   1篇
  1983年   7篇
  1982年   5篇
  1981年   2篇
  1980年   7篇
  1979年   4篇
  1978年   4篇
  1977年   5篇
  1975年   1篇
  1974年   4篇
  1972年   1篇
  1969年   2篇
  1967年   1篇
  1966年   2篇
排序方式: 共有847条查询结果,搜索用时 0 毫秒
1.
Aint was originally identified on the basis of its interaction in vitro with the aryl hydrocarbon nuclear receptor translocator (Arnt). Arnt is a common heterodimerization partner in the basic helix-loop-helix (bHLH)-PER-ARNT-SIM (PAS) protein family and is involved in diverse biological functions. These include xenobiotic metabolism, hypoxic response, and circadian rhythm. In addition, Arnt has a crucial role during development. Aint is a member of a growing family of transforming acidic coiled-coil (TACC) proteins and is the murine homologue of human TACC3. Here we report the spatiotemporal expression of Tacc3 mRNA and protein in embryonic, postnatally developing, and adult mouse tissues using in situ hybridization and immunocytochemistry. Tacc3 mRNA was highly expressed in proliferating cells of several organs during murine development. However, the only adult tissues expressing high levels were testis and ovary. Immunocytochemistry revealed that Tacc3 is a nuclear protein. Our results suggest that Tacc3 has an important role in murine development, spermatogenesis, and oogenesis.  相似文献   
2.
How Can the Eco‐efficiency of a Region be Measured and Monitored?   总被引:2,自引:0,他引:2  
The concept of eco-efficiency is commonly referred to as a business link to sustainable development. In this article, ecoefficiency is examined at a regional level as an approach to promoting the competitiveness of economic activities in the Finnish Kymenlaakso region and mitigating their harmful impacts on the environment. The aim is to develop appropriate indicators for monitoring changes in the eco-efficiency of the region. A starting point is to produce indicators for the environmental and economic dimensions of regional development and use them for measuring regional eco-efficiency. The environmental impact indicators are based on a life-cycle assessment method, producing different types of environmental impact indicators: pressure indicators (e.g., emissions of CO2), impact category indicators (e.g., CO2 equivalents in the case of climate change), and a total impact indicator (aggregating different impact category indicator results into a single value). Environmental impact indicators based on direct material input, total material input, and total material requirement of the Kymenlaakso region are also assessed. The economic indicators used are the gross domestic product, the value added, and the output of the main economic sectors of Kymenlaakso. In the eco-efficiency assessment, the economic and environmental impact indicators are monitored in the same graph. In a few cases eco-efficiency ratios can also be calculated (the economic indicators are divided by the environmental indicators). Output (= value added + intermediate consumption) is used as an economic indicator related to the environmental impact indicators, which also cover the upstream processes of the region's activities. In the article, we also discuss the strengths and weaknesses of using the different environmental impact indicators.  相似文献   
3.
4.
5.
Practical identifiability of growth and substrate consumption models   总被引:1,自引:0,他引:1  
The estimation of parameters in several dynamic models, which describe growth and substrate consumption, has been carried out using a modified Gauss-Newton-type method. The four models considered are Monod, Contois, linear specific growth rate, and an enzyme kinetic model. The initial values of the differential equations are included in the parameter vector which will be estimated. The efficiency of the method and the confidence limits of the parameters were studied using simulated measurement noise. The experimental results describe Trichoderma viride growing on glucose as the main carbon source.  相似文献   
6.
7.
The rates of keratinocyte proliferation and synthesis of Hyaluronan (HA) were studied in human whole-skin organ culture by labeling with [6-3H]glucosamine and [3H]thymidine, respectively, to reveal possible correlations between the two functions of the cell. HA distribution in epidermis was examined by staining with a specific probe prepared front cartilage proteoglycan. The keratinocyte proliferation rate was low on the first 2 culture days, but showed a tenfold increase on the third and fourth days while the synthesis of HA proceeded at a relatively stable level throughout the same period. The most intensive staining of HA occurred in the uppermost spinous cell layer, whereas mitotic cells resided in the basal and suprabasal layers. The keratinocytes under various stages of mitosis were surrounded by a HA staining not more intense than that around nondividing basal cells, but a thick pad of HA appeared rapidly between the daughter cells. These findings suggest that newly synthesized HA is associated with the separation of keratinocytes following mitosis but the majority of the synthesis and content of HA in epidermis is involved in other keratinocyte activities such as maintenance of the extracellular space and cell-cell interactions during migration and differentiation.  相似文献   
8.
Summary Calbindin D-28k-immunoreactivity has been demonstrated in some of the intrafusal muscle fibres and in the capsule of adult rat muscle spindles. In this study, the immunocytochemical localization of calbindin D-28k in the muscle spindles of triceps surae muscle was studied during postnatal maturation and after denervation. In young rats calbindin D-28k-immunoreactivity was seen in a few intrafusal fibres, first at the age of 4 days. At the 7th day, three calbindin D-28k-immunoreactive fibres and one unlabelled fibre were seen in most muscle spindles, as in adult rats. The spindle capsule and perineurial sheath of nerves were first seen to exhibit calbindin D-28k immunoreactivity at the age of 14 days, and thereafter the localization of calbinding D-28k-like immunoreactivity was similar to that in adult rats. After denervation, calbindin D-28k-immunoreactivity remained in intrafusal muscle fibres and the spindle capsule for a long period. After two months of denervation, calbindin D-28k immunoreactivity could still be seen in the spindle capsule, but the intrafusal fibres were not labelled.The innervation is known to have trophic effects on the intrafusal fibres. The present findings suggest that the expression of calbindin D-28k-immunoreactivity in maturating muscle spindles may be induced by the developing innervation. The decrease of calbindin D-28k-immunoreactivity in intrafusal fibres after denervation may be due to the loss of trophic factors released by the nerves.  相似文献   
9.
Thirteen severely retarded patients with Salla disease, a new type of lysosomal storage disorder, have been studied biochemically. All patients excreted approximately ten times more free sialic acid than normal individuals. The isolated sialic acid was characterized by paper chromatography, thin-layer chromatography, optical rotation, 13C and 1H nuclear magnetic resonance spectroscopy, and mass spectrometry of its permethylated derivative. The results clearly indicated that the excreted sialic acid was identical to N-acetylneuraminic acid. The main sialylated trisaccharide present in the urine of the patients was identified as 3'-sialyllactose by sugar and methylation analysis. The excreted amounts were found to be within normal range.  相似文献   
10.
A comprehensive community programme to control cardiovascular diseases (CVD) in North Karelia, Finland, was carried out during 1972-7. The central intermediate objective of the programme was to reduce the prevalence of smoking, the serum cholesterol concentration, and raised blood-pressure values among the population of the area. The effect was evaluated by examining independent representative population samples in 1972 and 1977 in both the county of North Karelia and a matched control county. Over 10 000 subjects were studied each time, the participation rate being around 90%. The decrease that occurred in the risk factors, especially in men, was in general greater in North Karelia compared with the control county. When a multiple logistic function was used for the three risk factors an overall mean net reduction of 17% among men and 12% among women was observed in the estimated risk for coronary heart disease in North Karelia. This community programme effectively reduced the levels of the three main risk factors for CVD in the population, and thus mortality and morbidity from CVD should fall. This is assessed in further studies.  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