全文获取类型
收费全文 | 1087596篇 |
免费 | 116234篇 |
国内免费 | 713篇 |
出版年
2018年 | 9829篇 |
2016年 | 13248篇 |
2015年 | 18132篇 |
2014年 | 21255篇 |
2013年 | 30822篇 |
2012年 | 33973篇 |
2011年 | 34660篇 |
2010年 | 23569篇 |
2009年 | 21598篇 |
2008年 | 30790篇 |
2007年 | 31738篇 |
2006年 | 29980篇 |
2005年 | 28829篇 |
2004年 | 28759篇 |
2003年 | 27705篇 |
2002年 | 26905篇 |
2001年 | 47641篇 |
2000年 | 48006篇 |
1999年 | 38354篇 |
1998年 | 13833篇 |
1997年 | 14429篇 |
1996年 | 13461篇 |
1995年 | 12758篇 |
1994年 | 12448篇 |
1993年 | 12288篇 |
1992年 | 32037篇 |
1991年 | 31205篇 |
1990年 | 30601篇 |
1989年 | 29974篇 |
1988年 | 27906篇 |
1987年 | 26291篇 |
1986年 | 24521篇 |
1985年 | 24723篇 |
1984年 | 20503篇 |
1983年 | 17447篇 |
1982年 | 13414篇 |
1981年 | 11993篇 |
1980年 | 11241篇 |
1979年 | 19157篇 |
1978年 | 14961篇 |
1977年 | 13792篇 |
1976年 | 12715篇 |
1975年 | 14070篇 |
1974年 | 15057篇 |
1973年 | 14921篇 |
1972年 | 13588篇 |
1971年 | 12416篇 |
1970年 | 10711篇 |
1969年 | 10485篇 |
1968年 | 9570篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
921.
A face fly (Musca autumnalis) population near Wetaskiwin, central Alberta, Canada, was sampled 9 times from 26 July to 29 September 1988 for the early larval stages of Thelazia spp. Of 426 female flies examined, 159 (37%) contained Thelazia spp. (almost exclusively T. skrjabini), with an average worm burden of 4.2 larvae per infected fly. Prevalence ranged from 17 to 56% over 9 collections. This is the first report of Thelazia skrjabini in flies from western North America and the highest Thelazia prevalence in face flies yet reported in North America. The face fly population was also parasitized by Heterotylenchus autumnalis, with a prevalence of 5.5%. 相似文献
922.
Biophysics - HMGB1 is one of the key proteins of the cell. HMGB1 performs its main functions predominantly in the cell nucleus, as an essential component of DNA–protein and multiprotein... 相似文献
923.
Silvio Antoniak Erica M. Sparkenbaugh Michael Tencati Mauricio Rojas Nigel Mackman Rafal Pawlinski 《PloS one》2013,8(11)
Heart failure is a major clinical problem worldwide. Previous studies have demonstrated an important role for G protein-coupled receptors, including protease-activated receptors (PARs), in the pathology of heart hypertrophy and failure. Activation of PAR-2 on cardiomyocytes has been shown to induce hypertrophic growth in vitro. PAR-2 also contributes to myocardial infarction and heart remodeling after ischemia/reperfusion injury. In this study, we found that PAR-2 induced hypertrophic growth of cultured rat neonatal cardiomyocytes in a MEK1/2 and p38 dependent manner. In addition, PAR-2 activation on mouse cardiomyocytes increased expression of the pro-fibrotic chemokine MCP-1. Furthermore, cardiomyocyte-specific overexpression of PAR-2 in mice induced heart hypertrophy, cardiac fibrosis, inflammation and heart failure. Finally, in a mouse model of myocardial infarction induced by permanent ligation of the left anterior descending coronary artery, PAR-2 deficiency attenuated heart remodeling and improved heart function independently of its contribution to the size of the initial infarct. Taken together, our data indicate that PAR-2 signaling contributes to the pathogenesis of hypertrophy and heart failure. 相似文献
924.
Dyscalculia, dyslexia, and specific language impairment (SLI) are relatively specific developmental learning disabilities in math, reading, and oral language, respectively, that occur in the context of average intellectual capacity and adequate environmental opportunities. Past research has been dominated by studies focused on single impairments despite the widespread recognition that overlapping and comorbid deficits are common. The present study took an epidemiological approach to study the learning profiles of a large school age sample in language, reading, and math. Both general learning profiles reflecting good or poor performance across measures and specific learning profiles involving either weak language, weak reading, weak math, or weak math and reading were observed. These latter four profiles characterized 70% of children with some evidence of a learning disability. Low scores in phonological short-term memory characterized clusters with a language-based weakness whereas low or variable phonological awareness was associated with the reading (but not language-based) weaknesses. The low math only group did not show these phonological deficits. These findings may suggest different etiologies for language-based deficits in language, reading, and math, reading-related impairments in reading and math, and isolated math disabilities. 相似文献
925.
Biophysics - A technology has been developed for the preparation of novel chloramine compounds related to adenosine derivatives. The optical absorption characteristics of... 相似文献
926.
Glushakova A. M. Lysak L. V. Kachalkin A. V. Ivanova A. E. Umarova A. B. Abramyan I. A. Ezhelev Z. S. Maksimova I. A. 《Microbiology》2021,90(2):176-186
Microbiology - In a model experiment, the transformation of microbial complexes of cultivated saprotrophic bacteria and yeasts during freezing-thawing was studied in various natural substrates that... 相似文献
927.
Kaminsky V. V. Emelyanenko A. M. Aleshkin A. V. Emelyanenko K. A. Boinovich L. B. 《Microbiology》2021,90(5):643-646
Microbiology - The surface of the MA8 magnesium alloy, modified by laser treatment, was found to acquire superhydrophilic properties and high bactericidal activity against Escherichia coli K12... 相似文献
928.
Plant and Soil - Cracks and biopores in compacted soil such as plough pans could aid deep rooting, mitigating constraints to seasonal upland use of paddy fields for rice production. This research... 相似文献
929.
Journal of Evolutionary Biochemistry and Physiology - A study of the effect of a seasonal decrease in ambient temperature on the composition of free amino acids and ninhydrin-positive secondary... 相似文献
930.
Baikenova M. B. Chereshnev V. A. Sokolova K. V. Gette I. F. Emelyanov V. V. Danilova I. G. 《Journal of Evolutionary Biochemistry and Physiology》2021,57(4):772-781
Journal of Evolutionary Biochemistry and Physiology - Due to a high occurrence of diabetes mellitus (DM) and its complications, insulin-positive cells detected in different organs are of great... 相似文献