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   638篇
  免费   42篇
  2023年   6篇
  2022年   9篇
  2021年   26篇
  2020年   14篇
  2019年   11篇
  2018年   22篇
  2017年   11篇
  2016年   16篇
  2015年   30篇
  2014年   37篇
  2013年   46篇
  2012年   58篇
  2011年   63篇
  2010年   33篇
  2009年   20篇
  2008年   26篇
  2007年   28篇
  2006年   24篇
  2005年   17篇
  2004年   14篇
  2003年   11篇
  2002年   10篇
  2001年   8篇
  2000年   7篇
  1999年   5篇
  1998年   7篇
  1997年   3篇
  1996年   3篇
  1995年   6篇
  1992年   11篇
  1991年   9篇
  1990年   11篇
  1989年   6篇
  1988年   3篇
  1987年   5篇
  1985年   4篇
  1984年   2篇
  1983年   6篇
  1982年   3篇
  1981年   2篇
  1980年   6篇
  1979年   8篇
  1978年   4篇
  1977年   2篇
  1976年   4篇
  1975年   2篇
  1974年   3篇
  1970年   2篇
  1967年   4篇
  1966年   2篇
排序方式: 共有680条查询结果,搜索用时 31 毫秒
671.
672.
A probability proportional to size (PPS) method of sample selection, based on the transformed auxiliary information as the measure of size, has been suggested. It has been observed that the PPS estimator under the suggested method is always better than the simple random sampling with replacement (SRSWR) and the usual PPSWR estimator. The efficiency of the proposed estimator with respect to the estimators under reference has also been empirically compared.  相似文献   
673.
Environmental adaptive response of fishes to the nutritional deficiencies of two important vitamins of the B-group viz . cyanocobalamin and folacin has been investigated using growth, haematology and haemopoiesis as physiological indices. Extended studies lasting 105 days revealed a consistent decrease in growth or even loss of weight when cyanocobalamin and folacin were absent from the diet. The combined deficiency of these two vitamins had an additive rather than synergistic effect on growth. The feed conversion values of all the deficient groups were significantly low as compared to the control. Haematologically the occurrence of anaemia and leucocytosis were recorded in all the deficient groups, the former mainly of megaloblastic type. Differential WBC counts revealed that leucocytosis was mainly due to an increase in thrombocyte population and cosinophils. On the other hand, there was an relative decrease of other nongranulocytes and granulocytes. Erythro-poietic investigations revealed a decreased proliferation rate of the reticuloendothelial cells and an increased number of young and mature reticulocytes and immature erythrocytes into the peripheral blood.  相似文献   
674.
675.
Among the wide variety of clinicopathological manifestations of intestinal amebiasis, amebomas occur rarely and their pathogenesis is not well understood. When cholesterol-fed, 2- to 4-week-old guinea pigs were infected intracecally with a virulent, monoaxenic strain of Entamoeba histolytica, gross and histologically characteristic amebomas developed in 85% of the animals by the 3rd day, in 94% by the 9th day, and in 96% by the 12th day postinfection, by which time most of them had died. Amebomas were confirmed by histopathology. Thus, a model of consistent production of amebomas was documented.  相似文献   
676.
Pseudomonas putida CSV86, a soil bacterium, grows on 1- and 2-methylnaphthalene as the sole source of carbon and energy. In order to deduce the pathways for the biodegradation of 1- and 2-methylnaphthalene, metabolites were isolated from the spent medium and purified by thin layer chromatography. Emphasis has been placed on the structural characterisation of isolated intermediates by GC-MS, demonstration of enzyme activities in the cell free extracts and measurement of oxygen uptake by whole cells in the presence of various probable metabolic intermediates. The data obtained from such a study suggest the possibility of occurrence of multiple pathways in the degradation of 1- and 2-methylnaphthalene. We propose that, in one of the pathways, the aromatic ring adjacent to the one bearing the methyl moiety is oxidized leading to the formation of methylsalicylates and methylcatechols. In another pathway the methyl side chain is hydroxylated to-CH2OH which is further converted to-CHO and-COOH resulting in the formation of naphthoic acid as the end product. In addition to this, 2-hydroxymethylnaphthalene formed by the hydroxylation of the methyl group of 2-methylnaphthalene undergoes aromatic ring hydroxylation. The resultant dihydrodiol is further oxidised by a series of enzyme catalysed reactions to form 4-hydroxymethyl catechol as the end product of the pathway.  相似文献   
677.
Probiotics and Antimicrobial Proteins - The growing consumer awareness towards healthy and safe food has reformed food processing strategies. Nowadays, food processors are aiming at natural,...  相似文献   
678.
679.
With the aim to discover orally active small molecules that stimulate glucose uptake, high throughput screening of a library of 5000 drug-like compounds was conducted in differentiated skeletal muscle cells in presence of insulin. N-Substituted phthalazinone acetamide was identified as a potential glucose uptake modulator. Several novel derivatives were synthesized to establish structure activity relationships. Identified lead thiazolyl-phthalazinone acetamide (7114863) increased glucose uptake (EC50 of 0.07 ± 0.02 μM) in differentiated skeletal muscle cells in presence of insulin. Furthermore, 7114863 was superior to rosiglitazone under similar experimental conditions without inducing PPAR-γ agonist activity thus making it a very interesting scaffold.  相似文献   
680.
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