全文获取类型
收费全文 | 62441篇 |
免费 | 4024篇 |
国内免费 | 5篇 |
出版年
2023年 | 448篇 |
2022年 | 386篇 |
2021年 | 839篇 |
2020年 | 761篇 |
2019年 | 753篇 |
2018年 | 1966篇 |
2017年 | 1830篇 |
2016年 | 2390篇 |
2015年 | 3137篇 |
2014年 | 3087篇 |
2013年 | 4147篇 |
2012年 | 5007篇 |
2011年 | 4463篇 |
2010年 | 2785篇 |
2009年 | 2134篇 |
2008年 | 3455篇 |
2007年 | 3255篇 |
2006年 | 3054篇 |
2005年 | 2618篇 |
2004年 | 2538篇 |
2003年 | 2266篇 |
2002年 | 2087篇 |
2001年 | 1415篇 |
2000年 | 1391篇 |
1999年 | 1066篇 |
1998年 | 446篇 |
1997年 | 323篇 |
1996年 | 333篇 |
1995年 | 312篇 |
1994年 | 238篇 |
1993年 | 227篇 |
1992年 | 537篇 |
1991年 | 464篇 |
1990年 | 417篇 |
1989年 | 412篇 |
1988年 | 409篇 |
1987年 | 355篇 |
1986年 | 345篇 |
1985年 | 346篇 |
1984年 | 352篇 |
1983年 | 236篇 |
1982年 | 216篇 |
1980年 | 178篇 |
1979年 | 219篇 |
1978年 | 208篇 |
1975年 | 197篇 |
1974年 | 221篇 |
1973年 | 224篇 |
1972年 | 185篇 |
1969年 | 172篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
M Pospísil J Sandula I Pipalová M Hofer S Viklická 《Physiological research / Academia Scientiarum Bohemoslovaca》1991,40(4):377-380
Carboxymethylglucan, a novel soluble derivative of beta-1,3-glucan, was found to enhance hemopoietic recovery in sublethally gamma-irradiated mice and to increase survival in lethally irradiated animals when given 24 hours prior to irradiation. Postirradiation treatment with carboxymethylglucan also induced favourable effects in terms of survival when used in combination with preirradiation cystamine administration. 相似文献
992.
H Nádvorníková O Schück V Teplan D Tomková V Reitschl?gerová 《Physiological research / Academia Scientiarum Bohemoslovaca》1991,40(1):87-94
The urinary excretion and serum concentration of amino acids were studied in 62 healthy individuals aged 15 to 70 years. In elderly subjects (61-70 years), it was found that renal amino acid clearance per 100 ml GFR (fractional excretion, FE) rose significantly in the following amino acids: CYS, VAL, MET, ILE and LEU. Since the serum concentrations of these amino acids showed no significant changes, but the GFR was reduced, it can be concluded that the raised FE of these amino acids was due to a decrease in their effective tubular reabsorption. A significant correlation was found between FENa and FE of most amino acids including those mentioned above. The findings support the assumption that changes in tubular Na+ transport probably participate in the changes of tubular amino acid transport in elderly individuals. 相似文献
993.
The effect of experimental hyperthyroidism on renal and adrenal weight increase in mice. 总被引:1,自引:0,他引:1
P D Broulík J Marek V Schreiber 《Physiological research / Academia Scientiarum Bohemoslovaca》1991,40(5):527-532
The mouse kidneys are enlarged after the administration of thyroxine and this influence is not mediated through androgens. The administration of thyroxine increased the weight of the adrenals and the level of plasma corticosterone. Besides the direct effect of the thyroid hormones on the kidney, our findings indicate that the excess of triiodothyronine and thyroxine stimulates the activity of adrenals indirectly and evokes hyperadrenocorticism which could be related to the action of adrenal steroids on kidney function and kidney growth. In accordance with the above mentioned hypothesis it has been shown that aminoglutethimide, a potent blocker of adrenal steroidogenesis, decreases the level of plasma corticosterone and inhibits the enlargement of the kidney in hyperthyroid mice in spite of the high serum thyroxine values. 相似文献
994.
Manuel Mari-Beffa José F. de Celis Antonio García-Bellido 《Development genes and evolution》1991,200(3):132-142
Summary The role of the achaete-scute complex and extramacrochaetae, Notch, Delta, Enhancer of split and Hairless genes in chaeta patterning in Drosophila tergites was studied in genetic mosaics and in mutant combinations. The mutant phenotypes of different alleles of each gene can be ordered in characteristic topographical seriations. These seriations are related to the pattern of proliferation of histoblasts and the time of singularization of sensory organ mother cells from surrounding epidermal cells. Genetic mosaics of lethal alleles show that these genes are fundamentally involved in this singularization and subsequent differentiation. The study of mutant combinations of alleles of these genes reveals specific relationships of epistasis and synergism between them. The results suggest that spatial and temporal variations in achaete-scute complex functional products in cells, modulated by the activity of other genes involved in signal transduction, define the patterned differentiation of sensory organs in tergites.
Offprint requests to: A. García-Bellido 相似文献
995.
The paper summarizes data concerning the biology and ecology ofOenanthe aquatica. The species is commonly distributed all over Czechoslovakia, from lowlands to the submontane belt, especially in fishpond and river basins.O. aquatica shows no special relationship to the chemical and physical soil properties, and is well adapted to habitats with a changing water level. The reproduction ofO. aquatica depends on emerging of the bottom. The most developed populations are formed by biennial plants and arise in the year following summer or autumn drainage. 相似文献
996.
The impact of domestic and wild Caprini browsing on Quercus ilex has been examined in an area of the Sierra de Cazorla. Vegetation as a herbivore food supply, herbivore feeding regime and density in the study area during six sampling periods throughout two years, has been quantified. Wild Caprini show diets similar to the available vegetation, whereas domestic Caprini tend more towards the trophic specialities (browsing or grazing) of their genus. Nevertheless, this tendency was more pronounced in domestic goats than in sheep. A hypothetical estimate of Q. ilex intake by each species under the study conditions was carried out. It was found that domestic Caprini have a greater impact on the holm oak than wild Caprini, density and feeding-niche deviations being the main factors responsible for this situation.Abbreviations DM=
dry matter 相似文献
997.
998.
Members of the alpha-amylase inhibitors family from wheat endosperm are major allergens associated with baker's asthma 总被引:5,自引:0,他引:5
L Gómez E Martín D Hernández R Sánchez-Monge D Barber V del Pozo B de Andrés A Armentia C Lahoz G Salcedo 《FEBS letters》1990,261(1):85-88
We have identified the major antigens or IgE binding components from wheat flour. Thirty-five sera from patients with baker's asthma were used to analyze the reaction with wheat salt-soluble proteins. We found a 15 kDa SDS-PAGE band which reacted with all sera tested. Purified members of the alpha-amylase inhibitor family, which are the main components of the 15 kDa band, were recognized by specific IgE when tested with a pool of reactive sera. Immunodetection after two-dimensional electrophoretic fractionation of crude inhibitor preparations from wheat endosperms also detected several inhibitor subunits as major low-molecular-weight allergens. 相似文献
999.
Ouabain-insensitive, Na-ATPase activity in pure suspensions of rat kidney proximal tubules 总被引:1,自引:0,他引:1
The present work was undertaken to evaluate the distribution of the Na-ATPase activity in the different components of the rat kidney cortex. Suspensions of glomeruli, proximal and distal tubules were prepared following a collagenase digestion of outermost kidney cortex slices and a separation on a Percoll gradient. It was found that the Na-ATPase activity is higher in the fraction enriched in proximal tubules. The fraction enriched in glomeruli and in distal tubules show also a Na-ATPase activity, but it is lower. 相似文献
1000.
In ten infants divided into two groups (up to one month of age and at 2–7 months of age) the dynamics and formation of different
antibody isotypes produced locally in the intenstine and in serum after orally administered inactivated enteropathogenicE. coli strains O111 and O55 was followed during 30 d after the first and booster dose by using an indirect immunofluorescence method.
Infants up to one month of age produced antibodies of IgM isotype in stool together with the IgA isotype after the first and
booster dose of the vaccine against both antigens. Serum IgG antibody increased after 2 d following the first and second dose
of antigens and remained higher during 5 d. The infants aged 2–7 months expressed predominantly the IgA isotype response in
stool after the first and booster dose of antigens. The serum immunoglobulin levels did not change after oral antigen administration. 相似文献