全文获取类型
收费全文 | 2903篇 |
免费 | 263篇 |
出版年
2023年 | 12篇 |
2022年 | 27篇 |
2021年 | 63篇 |
2020年 | 38篇 |
2019年 | 57篇 |
2018年 | 75篇 |
2017年 | 46篇 |
2016年 | 109篇 |
2015年 | 159篇 |
2014年 | 139篇 |
2013年 | 216篇 |
2012年 | 239篇 |
2011年 | 240篇 |
2010年 | 136篇 |
2009年 | 139篇 |
2008年 | 165篇 |
2007年 | 172篇 |
2006年 | 152篇 |
2005年 | 158篇 |
2004年 | 137篇 |
2003年 | 106篇 |
2002年 | 127篇 |
2001年 | 20篇 |
2000年 | 24篇 |
1999年 | 25篇 |
1998年 | 30篇 |
1997年 | 13篇 |
1996年 | 16篇 |
1995年 | 16篇 |
1994年 | 21篇 |
1993年 | 13篇 |
1992年 | 11篇 |
1991年 | 10篇 |
1990年 | 10篇 |
1989年 | 10篇 |
1988年 | 10篇 |
1987年 | 8篇 |
1986年 | 11篇 |
1985年 | 13篇 |
1983年 | 14篇 |
1982年 | 9篇 |
1981年 | 14篇 |
1980年 | 12篇 |
1979年 | 9篇 |
1976年 | 9篇 |
1975年 | 11篇 |
1974年 | 11篇 |
1973年 | 11篇 |
1969年 | 8篇 |
1967年 | 11篇 |
排序方式: 共有3166条查询结果,搜索用时 31 毫秒
981.
Balseiro P Falcó A Romero A Dios S Martínez-López A Figueras A Estepa A Novoa B 《PloS one》2011,6(8):e23140
Previous research has shown that an antimicrobial peptide (AMP) of the myticin class C (Myt C) is the most abundantly expressed gene in cDNA and suppressive subtractive hybridization (SSH) libraries after immune stimulation of mussel Mytilus galloprovincialis. However, to date, the expression pattern, the antimicrobial activities and the immunomodulatory properties of the Myt C peptide have not been determined. In contrast, it is known that Myt C mRNA presents an unusual and high level of polymorphism of unidentified biological significance. Therefore, to provide a better understanding of the features of this interesting molecule, we have investigated its function using four different cloned and expressed variants of Myt C cDNA and polyclonal anti-Myt C sera. The in vivo results suggest that this AMP, mainly present in hemocytes, could be acting as an immune system modulator molecule because its overexpression was able to alter the expression of mussel immune-related genes (as the antimicrobial peptides Myticin B and Mytilin B, the C1q domain-containing protein MgC1q, and lysozyme). Moreover, the in vitro results indicate that Myt C peptides have antimicrobial and chemotactic properties. Their recombinant expression in a fish cell line conferred protection against two different fish viruses (enveloped and non-enveloped). Cell extracts from Myt C expressing fish cells were also able to attract hemocytes. All together, these results suggest that Myt C should be considered not only as an AMP but also as the first chemokine/cytokine-like molecule identified in bivalves and one of the few examples in all of the invertebrates. 相似文献
982.
Fischer H Scherz J Szabo S Mildner M Benarafa C Torriglia A Tschachler E Eckhart L 《PloS one》2011,6(3):e17581
The cornified layer, the stratum corneum, of the epidermis is an efficient barrier to the passage of genetic material, i.e. nucleic acids. It contains enzymes that degrade RNA and DNA which originate from either the living part of the epidermis or from infectious agents of the environment. However, the molecular identities of these nucleases are only incompletely known at present. Here we performed biochemical and genetic experiments to determine the main DNase activity of the stratum corneum. DNA degradation assays and zymographic analyses identified the acid endonucleases L-DNase II, which is derived from serpinB1, and DNase 2 as candidate DNases of the cornified layer of the epidermis. siRNA-mediated knockdown of serpinB1 in human in vitro skin models and the investigation of mice deficient in serpinB1a demonstrated that serpinB1-derived L-DNase II is dispensable for epidermal DNase activity. By contrast, knockdown of DNase 2, also known as DNase 2a, reduced DNase activity in human in vitro skin models. Moreover, the genetic ablation of DNase 2a in the mouse was associated with the lack of acid DNase activity in the stratum corneum in vivo. The degradation of endogenous DNA in the course of cornification of keratinocytes was not impaired by the absence of DNase 2. Taken together, these data identify DNase 2 as the predominant DNase on the mammalian skin surface and indicate that its activity is primarily targeted to exogenous DNA. 相似文献
983.
984.
Alicia R. Pérez de Rosas Elsa L. Segura Octavio Fusco Adolfo L. Bareiro Guiñazú Beatriz A. García 《Genetica》2013,141(1-3):107-117
Fine scale patterns of genetic structure and dispersal in Triatoma infestans populations from Argentina was analysed. A total of 314 insects from 22 domestic and peridomestic sites from the locality of San Martín (Capayán department, Catamarca province) were typed for 10 polymorphic microsatellite loci. The results confirm subdivision of T. infestans populations with restricted dispersal among sampling sites and suggest inbreeding and/or stratification within the different domestic and peridomestic structures. Spatial correlation analysis showed that the scale of structuring is approximately of 400 m, indicating that active dispersal would occur within this distance range. It was detected difference in scale of structuring among sexes, with females dispersing over greater distances than males. This study suggests that insecticide treatment and surveillance should be extended within a radius of 400 m around the infested area, which would help to reduce the probability of reinfestation by covering an area of active dispersal. The inferences made from fine-scale spatial genetic structure analyses of T. infestans populations has demonstrated to be important for community-wide control programs, providing a complementary approach to help improve vector control strategies. 相似文献
985.
Very close similarities between the fossil genera Callimothallus Dilcher, 1965 and Microthallites Dilcher, 1965 and recent representatives of the green algae Ulvella P. L. &; H. M. Crouan, 1859, seem to rule out the assumption that fossil, disciform and radiate palynomorph microfossils are representatives of microthyrioaceous fungi. On the basis of the morphology of fossil Ulvella, a model of the general morpohlogy of encrusting, palynomorph algae is constructed. The model includes 5 morphological characters that may only be applied to encrusting life-forms and in particular not to planktonic algae. These characters, therefore, in future palynological research may serve to distinguish benthic algae from planktonic algae. A new fossil alga, Ulvella nannae sp. nov. is described. 相似文献
986.
Laura Espin Mercedes Almela Vanesa Hidalgo Carolina Villada Alicia Salvador Jesus Gomez-Amor 《Hormones and behavior》2013,63(5):759-765
This study explores the influence of pre-learning stress on performance on declarative memory tasks in healthy young adults in relation to sex and menstrual cycle phase. The sample was composed of 119 students (32 men and 87 women) from 18 to 25 years of age. The women were tested in different hormonal stages (30 in follicular phase, 34 in luteal phase, and 23 using oral contraceptives). The participants were exposed to the Trier Social Stress Test (TSST) or a control condition. Afterwards, their memory performance was measured using a standardized memory test (Rey's Auditory Verbal Learning Test). In the control condition, all groups of women recalled more words than men, but these differences disappeared in the group exposed to TSST because men's performance on the memory test improved, but only to the level of women. In addition, our data suggest that in women the relationship between cortisol and memory can be modulated by sex hormone levels, since in luteal women a negative relationship was found between memory performance and peak cortisol level. These results confirm that sex differences need to be considered in the relationship between pre-learning stress and memory performance. 相似文献
987.
988.
Alicia Álvarez S. Ivan Perez Diego H. Verzi 《Biological journal of the Linnean Society. Linnean Society of London》2013,110(4):898-913
Caviomorph rodents represent an excellent model to explore morphological diversification on a macroevolutionary scale, as they are ecologically and morphologically diverse. We analysed cranial shape variation using geometric morphometrics and phylogenetic comparative methods. Most variation involved the shape of the rostrum, basicranium, and cranial vault, and clearly matched the phylogenetic structure. At the same time, a strong allometric pattern was associated with the length of the rostrum and cranial vault, size of the auditory bulla, and depth of the zygomatic arch. After accounting for size influence, and taking phylogenetic structure into account, shape variation was significantly associated with habitat. Our results highlight the presence of complex relationships between morphological, phylogenetic, and ecological dimensions in the diversification of the caviomorph cranium. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2013, 110 , 898–913. 相似文献
989.
990.
Marina Stein Laura Zalazar Juana Alicia Willener Francisco Ludue?a Almeida Walter Ricardo Almirón 《Memórias do Instituto Oswaldo Cruz》2013,108(5):563-571
Studies were conducted to determine the selection of humans, chickens
and rabbits by Culicidae in three different environments in the province of
Chaco, Argentina. Mosquitoes were collected fortnightly using cylindrical metal
traps containing animal bait (chickens and rabbits). The mosquitoes were
collected between June 2001-May 2002. During the same period and with the same
frequency, mosquitoes biting the human operators of the traps were collected
during the first 15 min of exposure within different time intervals: from 09:00
am-11:00 am, 01:00 pm-03:00 pm, 05:00 pm-07:00 pm and 09:00 pm-10:00 pm. A total
of 19,430 mosquitoes of 49 species belonging to 10 genera were collected.
Culex species mainly selected chicken bait and
Wyeomyia species selected rabbit bait.
Ochlerotatus and Psorophora species were
more abundant in rabbit-baited traps. Anopheles triannulatus,
Coquillettidia nigricans, Ochlerotatus
scapularis, Mansonia titillans and
Psorophora albigenu showed a strong attraction for human
bait. The Anopheles, Coquillettidia,
Culex and Mansonia species were more
active between 05:00 pm-09:00 pm, while Ochlerotatus,
Psorophora, Haemagogus and
Wyeomyia were most active from 09:00 am-07:00 pm. This
study provides additional information about the biology and ecology of arbovirus
vectors in Chaco. 相似文献