全文获取类型
收费全文 | 749篇 |
免费 | 79篇 |
专业分类
828篇 |
出版年
2018年 | 7篇 |
2017年 | 7篇 |
2016年 | 12篇 |
2015年 | 19篇 |
2014年 | 16篇 |
2013年 | 27篇 |
2012年 | 40篇 |
2011年 | 40篇 |
2010年 | 36篇 |
2009年 | 23篇 |
2008年 | 28篇 |
2007年 | 30篇 |
2006年 | 30篇 |
2005年 | 27篇 |
2004年 | 24篇 |
2003年 | 22篇 |
2002年 | 21篇 |
2001年 | 17篇 |
2000年 | 27篇 |
1999年 | 22篇 |
1998年 | 10篇 |
1997年 | 10篇 |
1995年 | 7篇 |
1993年 | 9篇 |
1992年 | 15篇 |
1991年 | 17篇 |
1990年 | 9篇 |
1989年 | 6篇 |
1988年 | 10篇 |
1987年 | 17篇 |
1986年 | 13篇 |
1985年 | 10篇 |
1984年 | 9篇 |
1983年 | 9篇 |
1982年 | 9篇 |
1981年 | 7篇 |
1980年 | 7篇 |
1979年 | 6篇 |
1978年 | 13篇 |
1977年 | 19篇 |
1975年 | 8篇 |
1974年 | 9篇 |
1973年 | 12篇 |
1972年 | 10篇 |
1971年 | 10篇 |
1970年 | 8篇 |
1969年 | 10篇 |
1968年 | 6篇 |
1967年 | 10篇 |
1966年 | 8篇 |
排序方式: 共有828条查询结果,搜索用时 10 毫秒
131.
Suppressive Subtractive Hybridization of and Differences in Gene Expression Content of Calcifying and Noncalcifying Cultures of Emiliania huxleyi Strain 1516 下载免费PDF全文
Binh Nguyen Robert M. Bowers Thomas M. Wahlund Betsy A. Read 《Applied microbiology》2005,71(5):2564-2575
The marine coccolithophorid Emiliania huxleyi is a cosmopolitan alga intensely studied in relation to global carbon cycling, biogeochemistry, marine ecology, and biomineralization processes. The biomineralization capabilities of coccolithophorids have attracted the attention of scientists interested in exploiting this ability for the development of materials science and biomedical and biotechnological applications. Although it has been well documented that biomineralization in E. huxleyi is promoted by growth under phosphate-limited conditions, the genes and proteins that govern the processes of calcification and coccolithogenesis remain unknown. Suppressive subtractive hybridization (SSH) libraries were constructed from cultures grown in phosphate-limited and phosphate-replete media as tester and driver populations for reciprocal SSH procedures. Positive clones from each of the two libraries were randomly selected, and dot blotting was performed for the analysis of expression patterns. A total of 513 clones from the phosphate-replete library and 423 clones from the phosphate-limited library were sequenced, assembled, and compared to sequences in GenBank using BLASTX. Of the 103 differentially expressed gene fragments from the phosphate-replete library, 34% showed significant homology to other known proteins, while only 23% of the 65 differentially expressed gene fragments from the phosphate-limited library showed homology to other proteins. To further assess mRNA expression, real-time RT-PCR analysis was employed and expression profiles were generated over a 14-day time course for three clones from the phosphate-replete library and five clones from the phosphate-limited library. The fragments isolated provide the basis for future cloning of full-length genes and functional analysis. 相似文献
132.
133.
134.
135.
136.
Kindt TJ Said WA Bowers FS Mahana W Zhao TM Simpson RM 《Microbes and infection / Institut Pasteur》2000,2(10):1139-1146
Studies comparing functional differences in human T-cell leukemia virus type 1 (HTLV-1) clones that mediate distinct outcomes in experimentally infected rabbits, resulted in a dermatopathic smoldering adult T-cell leukemia/lymphoma following chronic infection with HTLV-1 strain RH/K34. During the 3.5 years' follow-up, HTLV-1 skin disease progressed to cutaneous T-cell lymphoma. When infection was passed to several naive rabbits, progressive paraparesis due to myelopathic neurodegeneration, analogous to HTLV-associated myelopathy, resulted in one of 4 transfusion recipients. Similar proviral loads were detected in the two diseases, regardless of stage of progression or tissue compartment of infection. Complete proviral sequences obtained from the donor and affected recipient aligned identically with each other and with the inoculated virus clone. Existence of disparate pathogenic outcomes following infectious transmission further extends the analogy of using rabbits to model human infection and disease. Although the experimental outcomes shown are limited by numbers of animals affected, they mimic the infrequency of HTLV-1 disease and authenticate epidemiological evidence of virus sequence stability regardless of disease phenotype. The findings suggest that further investigation of a possible role for HTLV-1 in some forms of cutaneous T-cell lymphoma is warranted. 相似文献
137.
Increased variance in the reproductive success of males relative to females favors mothers that optimally allocate sons and daughters to maximize their fitness return. In altricial songbirds, one influence on the fitness prospects of offspring arises through the order in which nestlings hatch from their eggs, which affects individual mass and size before nest leaving. In house wrens (Troglodytes aedon), the influence of hatching order depends on the degree of hatching synchrony, with greater variation in nestling mass and size within broods hatching asynchronously than in those hatching synchronously. Early-hatching nestlings in asynchronous broods were heavier and larger than their later-hatching siblings and nestlings in synchronous broods. The effect of hatching order was also sex specific, as the mass of males in asynchronous broods was more strongly influenced by hatching order than the mass of females, with increased variation in the mass of males relative to that of females. As predicted, mothers hatching their eggs asynchronously biased first-laid, first-hatching eggs toward sons and late-laid, late-hatching eggs toward daughters, whereas females hatching their eggs synchronously distributed the sexes randomly among the eggs of their clutch. We conclude that females allocate the sex of their offspring among the eggs of their clutch in a manner that maximizes their own fitness. 相似文献
138.
139.
Kominsky DJ Keely S MacManus CF Glover LE Scully M Collins CB Bowers BE Campbell EL Colgan SP 《Journal of immunology (Baltimore, Md. : 1950)》2011,186(11):6505-6514
Tissues of the mucosa are lined by an epithelium that provides barrier and transport functions. It is now appreciated that inflammatory responses in inflammatory bowel diseases are accompanied by striking shifts in tissue metabolism. In this paper, we examined global metabolic consequences of mucosal inflammation using both in vitro and in vivo models of disease. Initial analysis of the metabolic signature elicited by inflammation in epithelial models and in colonic tissue isolated from murine colitis demonstrated that levels of specific metabolites associated with cellular methylation reactions are significantly altered by model inflammatory systems. Furthermore, expression of enzymes central to all cellular methylation, S-adenosylmethionine synthetase and S-adenosylhomocysteine hydrolase, are increased in response to inflammation. Subsequent studies showed that DNA methylation is substantially increased during inflammation and that epithelial NF-κB activity is significantly inhibited following treatment with a reversible S-adenosylhomocysteine hydrolase inhibitor, DZ2002. Finally, these studies demonstrated that inhibition of cellular methylation in a murine model of colitis results in disease exacerbation while folate supplementation to promote methylation partially ameliorates the severity of murine colitis. Taken together, these results identify a global change in methylation, which during inflammation, translates to an overall protective role in mucosal epithelia. 相似文献
140.