全文获取类型
收费全文 | 668篇 |
免费 | 53篇 |
国内免费 | 2篇 |
专业分类
723篇 |
出版年
2023年 | 5篇 |
2022年 | 10篇 |
2021年 | 15篇 |
2020年 | 10篇 |
2019年 | 13篇 |
2018年 | 17篇 |
2017年 | 17篇 |
2016年 | 25篇 |
2015年 | 34篇 |
2014年 | 40篇 |
2013年 | 45篇 |
2012年 | 54篇 |
2011年 | 56篇 |
2010年 | 30篇 |
2009年 | 32篇 |
2008年 | 19篇 |
2007年 | 34篇 |
2006年 | 30篇 |
2005年 | 29篇 |
2004年 | 31篇 |
2003年 | 8篇 |
2002年 | 21篇 |
2001年 | 7篇 |
2000年 | 8篇 |
1999年 | 11篇 |
1998年 | 7篇 |
1997年 | 6篇 |
1996年 | 6篇 |
1995年 | 3篇 |
1994年 | 4篇 |
1993年 | 5篇 |
1992年 | 5篇 |
1991年 | 3篇 |
1990年 | 4篇 |
1989年 | 6篇 |
1988年 | 4篇 |
1987年 | 5篇 |
1986年 | 5篇 |
1985年 | 10篇 |
1983年 | 3篇 |
1982年 | 4篇 |
1980年 | 3篇 |
1979年 | 6篇 |
1978年 | 3篇 |
1976年 | 6篇 |
1974年 | 4篇 |
1973年 | 5篇 |
1970年 | 2篇 |
1967年 | 2篇 |
1966年 | 2篇 |
排序方式: 共有723条查询结果,搜索用时 15 毫秒
101.
Liu B Faller LL Klitgord N Mazumdar V Ghodsi M Sommer DD Gibbons TR Treangen TJ Chang YC Li S Stine OC Hasturk H Kasif S Segrè D Pop M Amar S 《PloS one》2012,7(6):e37919
The oral microbiome, the complex ecosystem of microbes inhabiting the human mouth, harbors several thousands of bacterial types. The proliferation of pathogenic bacteria within the mouth gives rise to periodontitis, an inflammatory disease known to also constitute a risk factor for cardiovascular disease. While much is known about individual species associated with pathogenesis, the system-level mechanisms underlying the transition from health to disease are still poorly understood. Through the sequencing of the 16S rRNA gene and of whole community DNA we provide a glimpse at the global genetic, metabolic, and ecological changes associated with periodontitis in 15 subgingival plaque samples, four from each of two periodontitis patients, and the remaining samples from three healthy individuals. We also demonstrate the power of whole-metagenome sequencing approaches in characterizing the genomes of key players in the oral microbiome, including an unculturable TM7 organism. We reveal the disease microbiome to be enriched in virulence factors, and adapted to a parasitic lifestyle that takes advantage of the disrupted host homeostasis. Furthermore, diseased samples share a common structure that was not found in completely healthy samples, suggesting that the disease state may occupy a narrow region within the space of possible configurations of the oral microbiome. Our pilot study demonstrates the power of high-throughput sequencing as a tool for understanding the role of the oral microbiome in periodontal disease. Despite a modest level of sequencing (~2 lanes Illumina 76 bp PE) and high human DNA contamination (up to ~90%) we were able to partially reconstruct several oral microbes and to preliminarily characterize some systems-level differences between the healthy and diseased oral microbiomes. 相似文献
102.
J Al Suwaidi K Al Habib N Asaad R Singh A Hersi H Al Falaeh S Al Saif A Al-Motarreb W Almahmeed K Sulaiman H Amin J Al-Lawati NQ Al-Sagheer AA Alsheikh-Ali AM Salam 《BMC cardiovascular disorders》2012,12(1):64
ABSTRACT: BACKGROUND: Stroke is a potential complication of acute coronary syndrome (ACS). The aim of this study was to identify the prevalence, risk factors predisposing to stroke, in-hospital and 1-year mortality among patients presenting with ACS in the Middle East. METHODS: For a period of 9 months in 2008 to 2009, 7,930 consecutive ACS patients were enrolled from 65 hospitals in 6 Middle East countries. RESULTS: The prevalence of in-hospital stroke following ACS was 0.70%. Most cases were ST segment elevation MI-related (STEMI) and ischemic stroke in nature. Patients with in-hospital stroke were 5 years older than patients without stroke and were more likely to have hypertension (66% vs. 47.6%, P = 0.001). There were no differences between the two groups in regards to gender, other cardiovascular risk factors, or prior cardiovascular disease. Patients with stroke were more likely to present with atypical symptoms, advanced Killip class and less likely to be treated with evidence-based therapies. Independent predictors of stroke were hypertension, advanced killip class, ACS type --STEMI and cardiogenic shock. Stroke was associated with increased risk of in-hospital (39.3% vs. 4.3%) and one-year mortality (52% vs. 12.3%). CONCLUSION: There is low incidence of in-hospital stroke in Middle-Eastern patients presenting with ACS but with very high in-hospital and one-year mortality rates. Stroke patients were less likely to be appropriately treated with evidence-based therapy. Future work should be focused on reducing the risk and improving the outcome of this devastating complication. 相似文献
103.
Amar S Ecke W Becker HC Möllers C 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2008,116(8):1051-1061
Improving oil and protein quality for food and feed purposes is an important goal in rapeseed (Brassica napus L.) breeding programs. Rapeseed contains phytosterols, used to enrich food products, and sinapate esters, which are limiting
the utilization of rapeseed proteins in the feed industry. Increasing the phytosterol content of oil and lowering sinapate
ester content of meal could increase the value of the oilseed rape crop. The objective of the present study was to identify
quantitative trait loci (QTL) for phytosterol and sinapate ester content in a winter rapeseed population of 148 doubled haploid
lines, previously found to have a large variation for these two traits. This population also segregated for the two erucic
acid genes. A close negative correlation was found between erucic acid and phytosterol content (Spearman’s rank correlation,
r
s = −0.80**). For total phytosterol content, three QTL were detected, explaining 60% of the genetic variance. The two QTL with the strongest
additive effects were mapped on linkage groups N8 and N13 within the confidence intervals of the two erucic acid genes. For
sinapate ester content four QTL were detected, explaining 53% of the genetic variance. Again, a close negative correlation
was found between erucic acid and sinapate ester content (r
s = −0.66**) and the QTL with the strongest additive effects mapped on linkage groups N8 and N13 within the confidence intervals of the
two erucic acid genes. The results suggests, that there is a pleiotropic effect of the two erucic acid genes on phytosterol
and sinapate ester content; the effect of the alleles for low erucic acid content is to increase phytosterol and sinapate
ester content. Possible reasons for this are discussed based on known biosynthetic pathways.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
104.
Dwivedi AP Kumar S Varshney V Singh AB Srivastava AK Sahu DP 《Bioorganic & medicinal chemistry letters》2008,18(7):2301-2305
A series of novel N-acyl-2-arylethylamines and N-acyl-3-coumarylamines were synthesized and evaluated for their antihyperglycemic activity. Compounds 3g and 6d exhibited lowering of postprandial plasma glucose by 30.7%, 23.3% in SLM and 25.6%, 25.4% in STZ models respectively which is significant compared to metformin and glybenclamide. Other compounds exhibited moderate to good activity ranging from 19.5% to 32.8% in SLM and 3.26% to 25.4% in STZ models. 相似文献
105.
MOSIX is a cluster management system that supports preemptive process migration. This paper presents the MOSIX Direct File System Access (DFSA), a provision that can improve the performance of cluster file systems by allowing a migrated process to directly access files in its current location. This capability, when combined with an appropriate file system, could substantially increase the I/O performance and reduce the network congestion by migrating an I/O intensive process to a file server rather than the traditional way of bringing the file's data to the process. DFSA is suitable for clusters that manage a pool of shared disks among multiple machines. With DFSA, it is possible to migrate parallel processes from a client node to file servers for parallel access to different files. Any consistent file system can be adjusted to work with DFSA. To test its performance, we developed the MOSIX File-System (MFS) which allows consistent parallel operations on different files. The paper describes DFSA and presents the performance of MFS with and without DFSA. 相似文献
106.
D T Graves N Nooh T Gillen M Davey S Patel D Cottrell S Amar 《Journal of immunology (Baltimore, Md. : 1950)》2001,167(9):5316-5320
Wound healing is a well-orchestrated complex process leading to the repair of injured tissues. After injury, proinflammatory cytokines act as important modulators of the inflammatory process. IL-1 expression has been regarded as necessary for healing; however, its effects have also been implicated in delayed wound repair. Currently, there is no consensus or direct evidence that IL-1 activity plays a central role in the healing process. The present investigation was undertaken to define the role of IL-1R signaling in the healing outcome of an excisional wound in the palate or scalp of mice that had targeted deletions of the IL-1R type 1 (IL-1R1(-/-)) compared with matched wild-type mice. Histomorphometric analysis was undertaken to assess the degree of healing and the recruitment of polymorphonuclear and mononuclear phagocytes. After 14 days, wild-type mice exhibited complete closure of intraoral wounds, while IL-1R1(-/-) animals had only partial closure (50%). In the IL-1R1(-/-) mice, healing tissues exhibited a persistent inflammatory cell infiltrate, which did not occur in wild-type animals. Treatment with antibiotics significantly diminished the persistent inflammatory infiltrate and improved healing in the experimental animals. In contrast to oral wounds, the rate of healing and recruitment of polymorphonuclear cells in scalp wounds was similar in IL-1R1(-/-) and wild-type mice. The present data underscore the importance of IL-1 in wound healing in a challenging environment and identify its principal role in facilitating the healing process by protecting an open wound from bacterial insult. In a less challenging environment, the production of new connective tissue and its coverage by migrating epithelium are minimally affected by the absence of IL-1 activity. 相似文献
107.
Enhanced Levels of the Aroma and Flavor Compound S-Linalool by Metabolic Engineering of the Terpenoid Pathway in Tomato Fruits 总被引:20,自引:0,他引:20
Efraim Lewinsohn Fernond Schalechet Jack Wilkinson Kenji Matsui Yaakov Tadmor Kyoung-Hee Nam Orit Amar Elena Lastochkin Olga Larkov Uzi Ravid William Hiatt Shimon Gepstein Eran Pichersky 《Plant physiology》2001,127(3):1256-1265
The aromas of fruits, vegetables, and flowers are mixtures of volatile metabolites, often present in parts per billion levels or less. We show here that tomato (Lycopersicon esculentum Mill.) plants transgenic for a heterologous Clarkia breweri S-linalool synthase (LIS) gene, under the control of the tomato late-ripening-specific E8 promoter, synthesize and accumulate S-linalool and 8-hydroxylinalool in ripening fruits. Apart from the difference in volatiles, no other phenotypic alterations were noted, including the levels of other terpenoids such as gamma- and alpha-tocopherols, lycopene, beta-carotene, and lutein. Our studies indicate that it is possible to enhance the levels of monoterpenes in ripening fruits by metabolic engineering. 相似文献
108.
109.
110.
Somdev Tyagi Kimio Inoue Amar Nath 《Biochimica et Biophysica Acta (BBA)/General Subjects》1978,539(1):125-134
Subtle changes in Mössbauer parameters are observed while going from methyl- to ethyl- to adenosylcobalamin, and also when the ‘base’ is detached from the cobalt. The observation of these changes demonstrates that the Co-C bond, among others, remains intact after the Auger event, accompanying the electron-capture decay of the cobalt-57.The differences between ethylcobalamin and the other two organocobalamins in the magnitude of the quadrupole splittings have been interpreted on the basis of the σ-donating tendency of the organic moiety and the CoC bond length. The latter is presumably determined by the steric hindrance offered to the group in approaching the cobalt atom.The ethyl- and adenosylcobalamins in their ‘base-off’ form exhibit a larger quadrupole splitting than the corresponding ‘base-on’ form. In the ‘base-off’ form, the cobalt atom is perhaps raised above the mean plane of the four equatorial nitrogen atoms of the corrin ring, which may result in the diminution of the delocalization of the 3dπ electron density. The higher population of dπ orbitals and the enhanced metallic character of the dz2, resulting from shrink-age of the CoC bond length, enhances the magnitude of the quadrupole splitting. 相似文献