全文获取类型
收费全文 | 939篇 |
免费 | 74篇 |
出版年
2023年 | 7篇 |
2022年 | 9篇 |
2021年 | 27篇 |
2020年 | 20篇 |
2019年 | 19篇 |
2018年 | 26篇 |
2017年 | 17篇 |
2016年 | 31篇 |
2015年 | 37篇 |
2014年 | 40篇 |
2013年 | 68篇 |
2012年 | 74篇 |
2011年 | 74篇 |
2010年 | 35篇 |
2009年 | 41篇 |
2008年 | 50篇 |
2007年 | 38篇 |
2006年 | 38篇 |
2005年 | 15篇 |
2004年 | 25篇 |
2003年 | 28篇 |
2002年 | 29篇 |
2001年 | 26篇 |
2000年 | 23篇 |
1999年 | 23篇 |
1998年 | 16篇 |
1997年 | 13篇 |
1996年 | 12篇 |
1995年 | 12篇 |
1994年 | 5篇 |
1993年 | 8篇 |
1992年 | 9篇 |
1991年 | 16篇 |
1990年 | 9篇 |
1989年 | 17篇 |
1988年 | 9篇 |
1987年 | 11篇 |
1986年 | 3篇 |
1985年 | 7篇 |
1984年 | 6篇 |
1983年 | 4篇 |
1982年 | 10篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1974年 | 2篇 |
1972年 | 4篇 |
1971年 | 2篇 |
1970年 | 2篇 |
1966年 | 3篇 |
排序方式: 共有1013条查询结果,搜索用时 187 毫秒
931.
Xiuli Dan Beimeng Yang Ross A. McDevitt Samuel Gray Xixia Chu Quia Claybourne David M. Figueroa Yongqing Zhang Deborah L. Croteau Vilhelm A. Bohr 《Aging cell》2023,22(4):e13793
Olfactory dysfunction is a prevalent symptom and an early marker of age-related neurodegenerative diseases in humans, including Alzheimer's and Parkinson's Diseases. However, as olfactory dysfunction is also a common symptom of normal aging, it is important to identify associated behavioral and mechanistic changes that underlie olfactory dysfunction in nonpathological aging. In the present study, we systematically investigated age-related behavioral changes in four specific domains of olfaction and the molecular basis in C57BL/6J mice. Our results showed that selective loss of odor discrimination was the earliest smelling behavioral change with aging, followed by a decline in odor sensitivity and detection while odor habituation remained in old mice. Compared to behavioral changes related with cognitive and motor functions, smelling loss was among the earliest biomarkers of aging. During aging, metabolites related with oxidative stress, osmolytes, and infection became dysregulated in the olfactory bulb, and G protein coupled receptor-related signaling was significantly down regulated in olfactory bulbs of aged mice. Poly ADP-ribosylation levels, protein expression of DNA damage markers, and inflammation increased significantly in the olfactory bulb of older mice. Lower NAD+ levels were also detected. Supplementation of NAD+ through NR in water improved longevity and partially enhanced olfaction in aged mice. Our studies provide mechanistic and biological insights into the olfaction decline during aging and highlight the role of NAD+ for preserving smelling function and general health. 相似文献
932.
933.
The finding of Corynosoma cetaceum Johnston and Best 1942, as a parasite of Cephalorhynchus eutropia Gray, 1846, is reported. This constitutes the first record of this acanthocephala in a new host, as well a new geographic distribution. 相似文献
934.
Lehrach and his coworkers have isolated a series of DNA probes that specifically hybridize with different regions of mouse chromosome 17 within the t complex. The probes display restriction fragment length polymorphisms, RFLPs, which are specific for the t haplotypes in all laboratory mouse strains tested thus far. Some of these probes have been used to test wild mice populations for these t-associated DNA forms. It is demonstrated that populations from Germany, Switzerland, Italy, Greece, Yugoslavia, Australia, Costa Rica, and Venezuela contain chromosomes in which all the tested DNA loci display the t-specific polymorphisms. The frequency of mice carrying these chromosomes is as high as 31%. Wild mice from Israel and Spain, on the other hand, carry chromosomes displaying t-specific DNA forms only at one or two of the probed loci, while the other loci carry the wild-type (+) forms. These chromosomes thus resemble the partial t haplotypes known from the study of laboratory mice. One possible interpretation of these findings is that these DNA polymorphisms contributed to the assembly of the complete t haplotypes and that these haplotypes may have originated in the Middle East. 相似文献
935.
After somatic fusion between a mitochondrial mutant ofCandida utilis andSaccharomyces cerevisiae respiratory competent strain, the complex III of the respiratory chain seems to be restored. Fusion products, FP, synthesizing normal apocytochromeb were recovered and showed normal-shaped mitochondria along the cytoplasm as in theCandida utilis original, respiratory-competent strain. 相似文献
936.
937.
Juan I. Túnez Humberto L. Cappozzo Maximiliano Nardelli Marcelo H. Cassini 《Genetica》2010,138(8):831-841
The north-central Patagonian coast is the sea lions most abundant area in Argentina. As occurs along the entire Atlantic coast,
the distribution of breeding colonies at this smaller geographical scale is also patchy, showing at least three areas with
breeding activity. We study the genetic structure and historical population dynamics of the species in five colonies in this
area, analysing a 508 base-pair segment of the D-loop control region. Otaria flavescens showed 10 haplotypes with 12 polymorphic sites. The genealogical relationship between haplotypes revealed a shallow pattern
of phylogeographic structure. The analysis of molecular variance showed significant differences between colonies, however,
pairwise comparisons only indicate significant differences between a pair of colonies belonging to different breeding areas.
The pattern of haplotype differentiation and the mismatch distribution analysis suggest a possible bottleneck that would have
occurred 64,000 years ago, followed by a demographic expansion of the three southernmost colonies. Thus, the historical population
dynamics of O. flavescens in north-central Patagonia appears to be closely related with the dynamics of the Late Pleistocene glaciations. 相似文献
938.
Nieto Gastón L. Haro J. Augusto McDonald H. Gregory Miño-Boilini Ángel R. Tauber Adan A. Krapovickas Jerónimo M. Fabianelli Maximiliano N. Rosas Federico M. 《Journal of Mammalian Evolution》2021,28(2):221-243
Journal of Mammalian Evolution - Dental and craniomandibular data have been predominantly used to infer relationships among mylodontid ground sloths. Recent studies indicate the osteology of the... 相似文献
939.
Actinopterygians (ray-finned fishes) are the most diverse group of living fishes, but have a sparse Devonian fossil record restricted to low palaeolatitudes. Here we report a new actinopterygian from the Paraná Basin of Brazil, which occupied a circumpolar position in the Palaeozoic. Available geological evidence supports a Middle Devonian or older age for this taxon, which shares features of the mandibular symphysis with the latest Devonian Tegeolepis. A phylogenetic analysis resolves these two as sister taxa. This new record expands the palaeogeographic distribution of Devonian ray-fins and suggests that gaps in their fossil record might be filled by exploring poorly sampled high-latitude localities within the Malvinokaffric Realm. 相似文献
940.
Julia Spencer Barthold Jobayer Hossain Alicia Olivant‐Fisher Anita Reilly T. Ernesto Figueroa Ahmad BaniHani Jennifer Hagerty Ricardo González Paul H. Noh Jeanne M. Manson 《Birth defects research. Part A, Clinical and molecular teratology》2012,94(11):900-907
BACKGROUND : Genetic and environmental factors likely influence susceptibility to nonsyndromic cryptorchidism, a common disease presenting at birth or in later childhood. We compared cases and controls to define differential risk factors for congenital versus acquired cryptorchidism. METHODS : We compared questionnaire and clinical data from cases of congenital cryptorchidism (n = 230), acquired cryptorchidism (n = 182) and hernia/hydrocele (n = 104) with a group of healthy male controls (n = 358). Potential predictor variables (p < 0.2 in univariable analysis) were included in stepwise multivariable logistic regression models. RESULTS : Temporary (odds ratio [OR], 0.5; 95% confidence interval [CI], 0.4–0.8) or exclusive (OR, 0.6; 95% CI, 0.4–0.9) breastfeeding was reduced and soy formula feeding increased (OR, 1.8; 95% CI, 1.2–2.9) in acquired but not congenital or hernia/hydrocele groups. The highest risk estimates were observed for primary soy formula feeding with limited or no breastfeeding (OR 2.5; 95% CI, 1.4–4.3; adjusted OR, 2.7; 95% CI, 1.4–5.4) in the acquired group. Primary feeding risk estimates were equivalent or strengthened when multivariable models were limited to age greater than 2 years, full‐term or not small for gestational age, or Caucasian subjects. Pregnancy complications and increased maternal exposure to cosmetic or household chemicals were not consistently associated with either form of cryptorchidism in these models. CONCLUSIONS : Our data support reduced breastfeeding and soy formula feeding as potential risk factors for acquired cryptorchidism. Although additional studies are needed, hormonally active components of breast milk and soy formula could influence the establishment of normal testis position in the first months of life, leading to apparent ascent of testes in childhood. Birth Defects Research (Part A), 2012. © 2012 Wiley Periodicals, Inc. 相似文献