全文获取类型
收费全文 | 12013篇 |
免费 | 1499篇 |
国内免费 | 3篇 |
出版年
2021年 | 177篇 |
2019年 | 122篇 |
2018年 | 137篇 |
2017年 | 130篇 |
2016年 | 227篇 |
2015年 | 353篇 |
2014年 | 355篇 |
2013年 | 468篇 |
2012年 | 584篇 |
2011年 | 542篇 |
2010年 | 363篇 |
2009年 | 331篇 |
2008年 | 446篇 |
2007年 | 426篇 |
2006年 | 426篇 |
2005年 | 413篇 |
2004年 | 388篇 |
2003年 | 393篇 |
2002年 | 374篇 |
2001年 | 362篇 |
2000年 | 380篇 |
1999年 | 328篇 |
1998年 | 165篇 |
1997年 | 179篇 |
1996年 | 178篇 |
1995年 | 126篇 |
1994年 | 139篇 |
1993年 | 139篇 |
1992年 | 265篇 |
1991年 | 241篇 |
1990年 | 247篇 |
1989年 | 231篇 |
1988年 | 220篇 |
1987年 | 219篇 |
1986年 | 176篇 |
1985年 | 224篇 |
1984年 | 175篇 |
1983年 | 149篇 |
1982年 | 154篇 |
1981年 | 140篇 |
1980年 | 117篇 |
1979年 | 171篇 |
1978年 | 137篇 |
1977年 | 128篇 |
1976年 | 116篇 |
1975年 | 108篇 |
1974年 | 134篇 |
1973年 | 135篇 |
1972年 | 111篇 |
1971年 | 119篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Taylor PM Batten P Brand NJ Thomas PS Yacoub MH 《The international journal of biochemistry & cell biology》2003,35(2):113-118
Cardiac valve interstitial cells (ICs) are a heterogeneous and dynamic population of specific cell types that have many unique characteristics. They are responsible for maintaining the extracellular scaffold that provides the mechanical characteristics vital for sustaining the unique dynamic behaviour of the valve. A number of cellular phenotypes can be distinguished: some are sparsely arranged throughout the valve leaflets, whilst others are arranged in thin bundles. These cells express molecular markers similar to those of skeletal, cardiac and smooth muscle cells (SMCs) and in particular, many ICs express smooth muscle (SM) alpha-actin, a marker of myofibroblasts. In this respect, these cells exhibit a profile unlike skin fibroblasts, which may allude to their role in valve function. 相似文献
992.
Comparison of enterococcal populations related to urban and hospital wastewater in various climatic and geographic European regions 总被引:1,自引:0,他引:1
Blanch AR Caplin JL Iversen A Kühn I Manero A Taylor HD Vilanova X 《Journal of applied microbiology》2003,94(6):994-1002
AIMS: Scarce knowledge about the distribution of enterococci species in wastewaters limits any statement on their reliability as faecal indicators or the implications of antibiotic resistance transmission by these organisms through the water cycle. Enterococci have been involved in nosocomial infections and the spreading of antibiotic resistance through the food chain. The species distribution of enterococci and the presence of resistant strains to vancomycin and erythromycin were analysed in more than 400 raw and treated urban wastewaters, surface waters receiving these treated wastewaters and hospital wastewaters from three European countries. METHODS AND RESULTS: A total of 9296 strains were isolated and biochemically phenotyped. The species identification was based on the comparison of biochemical profiles with those of more than 20000 enterococci isolates from an international study. The prevalence of enterococcal isolates resistant to erythromycin (ERE) and vancomycin (VRE) was also analysed. ERE strains were present in a high proportion in all the studied samples. VRE strains were also isolated in all studied countries despite the time elapsed since the use of antimicrobial glycopeptides in animal production was banned in the European Union. CONCLUSIONS: Enterococcus faecalis and Ent. faecium were the most abundant species in all the studied wastewaters. All the studied wastewaters demonstrated high diversity and similar population structure and composition. ERE and VRE isolates were detected in most of the wastewaters. SIGNIFICANCE AND IMPACT OF THE STUDY: Urban and hospital wastewaters are useful targets for the evaluation of the prevalence of ERE and VRE isolates in the environment. It appears that these bacteria could pass through wastewater treatment plants and be transferred to surface waters. 相似文献
993.
Brinen LS Canaves JM Dai X Deacon AM Elsliger MA Eshaghi S Floyd R Godzik A Grittini C Grzechnik SK Guda C Jaroszewski L Karlak C Klock HE Koesema E Kovarik JS Kreusch A Kuhn P Lesley SA McMullan D McPhillips TM Miller MA Miller MD Morse A Moy K Ouyang J Robb A Rodrigues K Selby TL Spraggon G Stevens RC van den Bedem H Velasquez J Vincent J Wang X West B Wolf G Taylor SS Hodgson KO Wooley J Wilson IA 《Proteins》2003,50(2):371-374
994.
Taylor G Tricker PJ Zhang FZ Alston VJ Miglietta F Kuzminsky E 《Plant physiology》2003,131(1):177-185
Leaf expansion in the fast-growing tree, Populus x euramericana was stimulated by elevated [CO(2)] in a closed-canopy forest plantation, exposed using a free air CO(2) enrichment technique enabling long-term experimentation in field conditions. The effects of elevated [CO(2)] over time were characterized and related to the leaf plastochron index (LPI), and showed that leaf expansion was stimulated at very early (LPI, 0-3) and late (LPI, 6-8) stages in development. Early and late effects of elevated [CO(2)] were largely the result of increased cell expansion and increased cell production, respectively. Spatial effects of elevated [CO(2)] were also marked and increased final leaf size resulted from an effect on leaf area, but not leaf length, demonstrating changed leaf shape in response to [CO(2)]. Leaves exhibited a basipetal gradient of leaf development, investigated by defining seven interveinal areas, with growth ceasing first at the leaf tip. Interestingly, and in contrast to other reports, no spatial differences in epidermal cell size were apparent across the lamina, whereas a clear basipetal gradient in cell production rate was found. These data suggest that the rate and timing of cell production was more important in determining leaf shape, given the constant cell size across the leaf lamina. The effect of elevated [CO(2)] imposed on this developmental gradient suggested that leaf cell production continued longer in elevated [CO(2)] and that basal increases in cell production rate were also more important than altered cell expansion for increased final leaf size and altered leaf shape in elevated [CO(2)]. 相似文献
995.
996.
Survival of Mycobacterium bovis after ingestion by protozoa would provide an environmental reservoir for infection of cattle. We have shown that M. bovis survived ingestion by Acanthamoeba castellanii. In contrast, two strains of M. bovis BCG did not survive well within Acanthamoeba. 相似文献
997.
The purpose of this study was to evaluate the effects of isolated alterations in mineral content on mouse bone torsional properties. The femora and tibiae from 25 eight-week-old male A/J strain mice were divided into five groups and selectively decalcified from 5% to 20%. The right femora were then tested to failure in torsion while the tibiae were ashed to determine final mineral content of the decalcified bones. Contralateral femora were serially cross-sectioned to determine geometric properties, and effective material properties were then calculated from the geometric and structural properties of each femoral pair. We found that the relationship between ash content and effective shear modulus or maximum effective shear stress could best be characterized through a power law, with an exponential factor of 6.79 (R2 = 0.85) and 4.04 (R2 = 0.67), respectively. This indicates that in a murine model, as with other species, small changes in ash content significantly influence effective material properties. Furthermore, it appears that (in adolescent A/J strain mice) effective shear modulus is more heavily affected by changes in mineralization than is maximum effective shear stress when these properties are derived from whole bone torsional tests to failure. 相似文献
998.
Global organellar proteomics 总被引:21,自引:0,他引:21
Cataloging the proteomes of single-celled microorganisms, cells, biological fluids, tissue and whole organisms is being undertaken at a rapid pace as advances are made in protein and peptide separation, detection and identification. For metazoans, subcellular organelles represent attractive targets for global proteome analysis because they represent discrete functional units, their complexity in protein composition is reduced relative to whole cells and, when abundant cytoskeletal proteins are removed, lower abundance proteins specific to the organelle are revealed. Here, we review recent literature on the global analysis of subcellular organelles and briefly discuss how that information is being used to elucidate basic biological processes that range from cellular signaling pathways through protein-protein interactions to differential expression of proteins in response to external stimuli. We assess the relative merits of the different methods used and discuss issues and future directions in the field. 相似文献
999.
Kawa JM Przybylski R Taylor CG 《Experimental biology and medicine (Maywood, N.J.)》2003,228(8):907-914
Inositol phosphoglycan molecules containing either D-chiro-inositol or myo-inositol have been isolated from various mammalian tissues and are putative mediators of insulin action. Urinary excretion of inositols appears to be altered in diabetes mellitus; however, the relationships with different types of diabetes are unclear. The objective of this study was to determine the urinary excretion of chiro- and myo-inositol in diabetic animal models, including streptozotocin (STZ) rats, db/db mice, and fa/fa Zucker rats. In STZ rats (type 1 diabetes), 12-hr urinary excretion of chiro-inositol was elevated 336-fold and myo-inositol excretion was elevated 47-fold compared with their nondiabetic counterparts. When corrected for creatinine, chiro-inositol excretion was 259-fold higher and myo-inositol excretion was 36-fold higher in STZ rats than in normal rats. The same pattern was observed in db/db mice (type 2 diabetes), where 12-hr urinary chiro-inositol excretion was elevated 247-fold compared with normal mice. When corrected for creatinine, chiro-inositol excretion was 2455-fold higher and urinary myo-inositol excretion was elevated 8.5-fold in db/db mice compared with normal mice. The fa/fa Zucker rats (impaired glucose tolerance) had a pattern of urinary inositol excretion that was similar to the nondiabetic animals (lean Zucker rats, C57BL/6 mice, and Sprague-Dawley rats). In summary, urinary chiro-inositol and myo-inositol excretion was elevated in animal models of type 1 and type 2 diabetes mellitus, concomitant with hyperglycemia and glucosuria. 相似文献
1000.
Two-dimensional gel electrophoresis (2-DE) has become a powerful and widely used technique for proteomic analyses. However, the limited ability of 2-DE to resolve transmembrane and glycosylphosphatidylinositol (GPI)-anchored proteins has slowed the identification of proteins from membrane-rich biological samples. Myelin is an unusually lipid-rich membrane with relatively few major proteins but many quantitatively minor proteins, most of which have an unknown identity and/or function. The goal of this study was to identify the optimal conditions of 2-DE for the separation of myelin proteins. We have identified two detergents, the nonionic n-dodecyl beta-D-maltoside and the zwitterionic amidosulfobetaine ASB-14, that are more effective in solubilizing myelin proteins than the commonly used zwitterionic detergent 3-[(3-cholamidopropyl)- dimethylammonio]-1-propanesulfonate (CHAPS). These detergents significantly enhance the solubility of both transmembrane (e.g., the highly hydrophobic and multiply acylated myelin proteolipid protein) and GPI-anchored (e.g., contactin and neuronal cell adhesion molecule) myelin proteins and enable their resolution by 2-DE. We conclude that these detergents are effective tools for the 2-DE analysis of myelin, and that they may be more generally useful for the analysis of membrane-rich biological samples. 相似文献