全文获取类型
收费全文 | 2878篇 |
免费 | 210篇 |
国内免费 | 1篇 |
出版年
2023年 | 29篇 |
2022年 | 21篇 |
2021年 | 81篇 |
2020年 | 72篇 |
2019年 | 67篇 |
2018年 | 129篇 |
2017年 | 126篇 |
2016年 | 141篇 |
2015年 | 196篇 |
2014年 | 198篇 |
2013年 | 249篇 |
2012年 | 286篇 |
2011年 | 256篇 |
2010年 | 128篇 |
2009年 | 107篇 |
2008年 | 186篇 |
2007年 | 131篇 |
2006年 | 134篇 |
2005年 | 111篇 |
2004年 | 90篇 |
2003年 | 79篇 |
2002年 | 67篇 |
2001年 | 25篇 |
2000年 | 28篇 |
1999年 | 23篇 |
1998年 | 7篇 |
1997年 | 7篇 |
1996年 | 10篇 |
1995年 | 9篇 |
1994年 | 5篇 |
1993年 | 3篇 |
1992年 | 6篇 |
1991年 | 9篇 |
1990年 | 5篇 |
1989年 | 6篇 |
1988年 | 3篇 |
1987年 | 7篇 |
1986年 | 4篇 |
1985年 | 3篇 |
1984年 | 7篇 |
1981年 | 5篇 |
1977年 | 4篇 |
1975年 | 5篇 |
1974年 | 3篇 |
1973年 | 3篇 |
1969年 | 2篇 |
1968年 | 2篇 |
1967年 | 3篇 |
1965年 | 2篇 |
1957年 | 1篇 |
排序方式: 共有3089条查询结果,搜索用时 15 毫秒
81.
Keller Ricardo Ferreira Sobrinho Ana Carolina Monteiro Santini Carlos Leonardo Sacomani Marques Maicon Gonçalves Gabriel Eduardo de Moura Neto Luciane Aparecida Pascucci Sande de Souza 《Somatosensory & motor research》2013,30(3-4):199-203
AbstractBackground: Unilateral spatial neglect (USN) is the prevalent feature in patients with right-sided stroke. It is diagnosed through the behavior inattention test (BIT) and has a negative impact on patients affecting both their functional capacity and quality of life.Objective: Here, we aimed to evaluate the impact of USN on the quality of life of patients in the chronic phase of stroke.Methods: This is a cross-sectional study with stroke patients with USN. After confirming the presence of stroke through neuroimaging examinations and of USN through the BIT, patients’ quality of life was evaluated by using the EUROQOL scale. Spearman’s correlation was used to validate the correlation between patients’ USN and quality of life, with a p?<?.05 representing significant results.Results: Eighteen individuals were included. When correlating the value of each domain of the EUROQOL scale with the results of the BIT, we observed a negative correlation between mobility (r?=?–0.97; p?=?.000), self-care (r?=?–0.82; p?=?.013), usual activities (r?=?–0.87; p?=?.005); pain or discomfort (r?=?–0.88; p?=?.004), anxiety or depression (r?=?–0.97; p?=?.000), and EUROQOL total score (r?=?–0.97, p?=?.000).Conclusion: After a correlation between the overall EUROQOL and BIT scores, we suggest that the higher the USN degree is in stroke patients, the worse their perceived quality of life tends to be. 相似文献
82.
Nathalia Torres Dutra Vanildo Silveira Inga Gonçalves de Azevedo Lupis Ribeiro Gomes‐Neto Arnoldo Rocha Façanha Neusa Steiner Miguel Pedro Guerra Eny Iochevet Segal Floh Claudete Santa‐Catarina 《Physiologia plantarum》2013,148(1):121-132
Polyamines (PAs) are abundant polycationic compounds involved in many physiological processes in plants, including somatic embryogenesis. This study investigates the role of PAs on cellular growth and structure of pro‐embryogenic masses (PEMs), endogenous PA and proton pump activities in embryogenic suspension cultures of Araucaria angustifolia. The embryogenic suspension cultures were incubated with putrescine (Put), spermidine (Spd), spermine (Spm) and the inhibitor methylglyoxal‐bis(guanylhydrazone) (MGBG), respectively (1 mM). After 24 h and 21 days, the cellular growth and structure of PEMs, endogenous PA contents and proton pump activities were analyzed. The addition of Spm reduced the cellular growth and promoted the development of PEMs in embryogenic cultures, which could be associated with a reduction in the activities of proton pumps, such as H+‐ATPase P‐ and V‐types and H+‐PPases, and alterations in the endogenous PA contents. Spm significantly affected the physiology of the A. angustifolia somatic embryogenesis suspension, as it potentially affects cellular growth and structure of PEMs through the modulation of proton pump activities. This work demonstrates the involvement of exogenous PAs in the modulation of cellular growth and structure of PEMs, endogenous PA levels and proton pump activities during somatic embryogenesis. To our knowledge, this study is the first to report a relationship between PAs and proton pump activities in these processes. The results obtained in this study offer new perspectives for studies addressing the role of PAs and proton pump on somatic embryogenesis in this species. 相似文献
83.
Eliana M. Cancello 《法国昆虫学会纪事》2013,49(2):187-193
A new genus Paraconvexitermes is described, comprising Paraconvexitermes acangapua, new species, P. nigricornis (Holmgren) and P. junceus (Emerson), both previously in Convexitermes Holmgren. Now, Convexitermes comprises C. manni Emerson and C. convexifrons (Holmgren). The worker’s digestive tube of both genera along with those of Atlantitermes species allowed to get a better definition of these three genera. Illustrations on the digestive tube and mandibles of workers, soldier’s head, alate’s head and secondary reproductive female of the new genus and species are provided. The phylogenetic relationships with the other nasute genera are discussed along with the “soil feeding” concept. 相似文献
84.
Hoffmannseggella viridiflora Verola & Semir (Laeliinae, Orchidaceae) is a recently discovered species in the campos rupestres vegetation of the Espinhaço Range, MG, Brazil, in synchronopatry with H. bradei (Pabst) V. P. Castro & Chiron. Both morphological and phenological studies indicate that these species are closely related. To substantiate the differentiation of these two species we examined their chromosome numbers and morphologies. The two species had different chromosome numbers, with H. bradei having 2n = 40 and H. viridiflora having 2n = 44 chromosomes, an aneuploid number not previously documented in the genus. Meiotic behavioral studies undertaken with H. bradei revealed many abnormalities related to bivalent numbers and chromosome migration, suggesting that meiotic abnormalities could generate aneuploid gametes and perhaps aneuploid zygotes. Karyotype formulas and chromosome morphologies are quite different between the species, so H. viridiflora was not directly derived from H. bradei through simple chromosome additions. Complementary analyses are necessary to understand the process and species involved in the origin of H. viridiflora. 相似文献
85.
Georgina Gonçalves Mansur José Willibaldo Thomé 《Studies on Neotropical Fauna and Environment》2013,48(1):77-84
Exospermastix robustus Verhoeff, 1951 (Mato Grosso, nr Cuiaba) is regarded as a species of Urostreptus; the gonopods of the type specimen are illustrated and their structure discussed. The species is in many ways similar to U. camerani and U. paxillatus, but is much larger than either. The status of the generic and specific names Stenostreptus hassleri Carl is reviewed after a study of the type material, and the previous estimate of hassleri as a species of Urostreptus is reaffirmed. New drawings made from the lectotype of hassleri are given. The gonopods of a species identified as U. borelli by F. Silvestri, the author of that name, are illustrated, and the suggestion made that borelli may be found to be a senior synonym of hassleri. 相似文献
86.
87.
Adriana Fernanda Vizuete Daniela Fraga de Souza Maria Cristina Guerra Cristiane Batassini Márcio Ferreira Dutra Caren Bernardi Ana Paula Costa Carlos-Alberto Gonçalves 《Life sciences》2013,92(17-19):923-928
AimsWe investigated the effects of ketogenic diet (KD) on levels of tumor necrosis factor alpha (TNF-α, a classical pro-inflammatory cytokine), BDNF (brain-derived neurotrophic factor, commonly associated with synaptic plasticity), and S100B, an astrocyte neurotrophic cytokine involved in metabolism regulation.Main methodsYoung Wistar rats were fed during 8 weeks with control diet or two KD, containing different proportions of omega 6 and omega 3 polyunsaturated fatty acids. Contents of TNF-α, BDNF and S100B were measured by ELISA in two brain regions (hippocampus and striatum) as well as blood serum and cerebrospinal fluid.Key findingsOur data suggest that KD was able to reduce the levels of BDNF in the striatum (but not in hippocampus) and S100B in the cerebrospinal fluid of rats. These alterations were not affected by the proportion of polyunsaturated fatty acids offered. No changes in S100B content were observed in serum or analyzed brain regions. Basal TNF-α content was not affected by KD.SignificanceThese findings reinforce the importance of this diet as an inductor of alterations in the brain, and such changes might contribute to the understanding of the effects (and side effects) of KD in brain disorders. 相似文献
88.
Fábio Takenori Higa Lucila Okuyama Fukasawa Maria Gisele Gon?alves Maristela Marques Salgado Ana Paula Silva de Lemos Lee H Harrison Priscilla Lima de Oliveira Carla Naufal da Silva Claudio Tavares Sacchi 《Memórias do Instituto Oswaldo Cruz》2013,108(2):246-247
We evaluated the use of a newly described sodC-based real-time-polymerase chain reaction (RT-PCR) assay for detecting Neisseria meningitidis in normally sterile sites, such as cerebrospinal fluid and serum. The sodC-based RT-PCR assay has an advantage over ctrA for detecting nongroupable N. meningitidis isolates, which are commonly present in asymptomatic pharyngeal carriage. However, in our study, sodC-based RT-PCR was 7.5% less sensitive than ctrA. Given the public health impact of possible false-negative results due to the use of the sodC target gene alone, sodC-based RT-PCR for the diagnosis of meningococcal meningitis should be used with caution. 相似文献
89.
Luiz Claudio Pereira Ribeiro Cassia Cristina Alves Gon?alves Carla Maria Sena Andrade Slater Silvia Maia Farias de Carvalho Marzia Puccioni-Sohler 《Memórias do Instituto Oswaldo Cruz》2013,108(6):730-734
Intrathecal synthesis of human T-lymphotropic virus type 1 (HTLV-1) antibodies
(Abs) represents conclusive evidence of a specific immune response in the
central nervous system of HTLV-1 associated myelopathy/tropical spastic
paraparesis (HAM/TSP) patients. Western blotting (WB) for HTLV Abs in serum is a
confirmatory test for HTLV-1 infection. The aim of this study was to standardise
the Western blot to demonstrate the intrathecal pattern of Abs against HTLV-1
proteins in HAM/TSP patients. Paired cerebrospinal fluid (CSF) and serum samples
were selected from 20 patients with definite HAM/TSP, 19 HTLV-1 seronegative
patients and two HTLV-1 patients without definite HAM/TSP. The presence of
reactive bands of greater intensity in the CSF compared to serum (or bands in
only the CSF) indicated the intrathecal synthesis of anti-HTLV-1 Abs. All
definite HAM/TSP patients presented with an intrathecal synthesis of anti-HTLV-1
Abs; these Abs were not detected in the control patients. The most frequent
intrathecal targets of anti-HTLV-1 Abs were GD21, rgp46-I and p24 and, to a
lesser extent, p19, p26, p28, p32, p36, p53 gp21 and gp46. The intrathecal
immune response against env (GD21 and rgp46-I) and
gag (p24) proteins represents the most important humoral
pattern in HAM/TSP. This response may be used as a diagnostic marker,
considering the frequent association of intrathecal anti-HTLV-1 Ab synthesis
with HAM/TSP and the pathogenesis of this neurological disease. 相似文献
90.
Marcelo Manzi Marinho Maria Betânia Gonçalves Souza Miquel Lürling 《Microbial ecology》2013,66(3):479-488
The hypothesis that outcomes of phosphorus and light competition between Cylindrospermopsis raciborskii and Microcystis aeruginosa are strain dependent was tested experimentally. Critical requirements of phosphorus (P*) and of light (I*) of two strains of each species were determined through monoculture experiments, which indicated a trade-off between species and also between Microcystis strains. Competition experiments between species were performed using the weakest predicted competitors (with the highest values of P* and of I*) and with the strongest predicted competitors (with the lowest values of P* and of I*). Under light limitation, competition between the weakest competitors led C. raciborskii to dominate. Between the strongest competitors, the opposite was observed, M. aeruginosa displaced C. raciborskii, but both strains co-existed in equilibrium. Under phosphate limitation, competition between the weakest competitors led C. raciborskii to exclude M. aeruginosa, and between the strongest competitors, the opposite was observed, M. aeruginosa displaced C. raciborskii, but the system did not reach an equilibrium and both strains were washed out. Hence, outcomes of the competition depended on the pair of competing strains and not only on species or on type of limitation. We concluded that existence of different trade-offs among strains and between species underlie our results showing that C. raciborskii can either dominate or be displaced by M. aeruginosa when exposed to different conditions of light or phosphate limitation. 相似文献