全文获取类型
收费全文 | 8356篇 |
免费 | 501篇 |
国内免费 | 58篇 |
专业分类
耳鼻咽喉 | 125篇 |
儿科学 | 281篇 |
妇产科学 | 102篇 |
基础医学 | 1144篇 |
口腔科学 | 821篇 |
临床医学 | 623篇 |
内科学 | 1971篇 |
皮肤病学 | 137篇 |
神经病学 | 536篇 |
特种医学 | 351篇 |
外国民族医学 | 2篇 |
外科学 | 746篇 |
综合类 | 62篇 |
一般理论 | 3篇 |
预防医学 | 846篇 |
眼科学 | 128篇 |
药学 | 582篇 |
中国医学 | 43篇 |
肿瘤学 | 412篇 |
出版年
2023年 | 68篇 |
2022年 | 144篇 |
2021年 | 271篇 |
2020年 | 172篇 |
2019年 | 228篇 |
2018年 | 284篇 |
2017年 | 198篇 |
2016年 | 239篇 |
2015年 | 275篇 |
2014年 | 341篇 |
2013年 | 433篇 |
2012年 | 663篇 |
2011年 | 648篇 |
2010年 | 398篇 |
2009年 | 332篇 |
2008年 | 479篇 |
2007年 | 487篇 |
2006年 | 420篇 |
2005年 | 373篇 |
2004年 | 301篇 |
2003年 | 245篇 |
2002年 | 234篇 |
2001年 | 142篇 |
2000年 | 159篇 |
1999年 | 150篇 |
1998年 | 93篇 |
1997年 | 89篇 |
1996年 | 77篇 |
1995年 | 49篇 |
1994年 | 62篇 |
1993年 | 50篇 |
1992年 | 73篇 |
1991年 | 65篇 |
1990年 | 54篇 |
1989年 | 70篇 |
1988年 | 86篇 |
1987年 | 51篇 |
1986年 | 49篇 |
1985年 | 72篇 |
1984年 | 39篇 |
1983年 | 23篇 |
1982年 | 17篇 |
1981年 | 23篇 |
1980年 | 24篇 |
1979年 | 15篇 |
1978年 | 18篇 |
1977年 | 16篇 |
1976年 | 24篇 |
1975年 | 19篇 |
1968年 | 12篇 |
排序方式: 共有8915条查询结果,搜索用时 515 毫秒
51.
Sputum Cytokine Levels in Patients with Pulmonary Tuberculosis as Early Markers of Mycobacterial Clearance
下载免费PDF全文
![点击此处可从《Clinical and Vaccine Immunology : CVI》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Rodrigo Ribeiro-Rodrigues Tatiana Resende Co John L. Johnson Fabiola Ribeiro Moises Palaci Ricardo T. S Ethel L. Maciel Fausto E. Pereira Lima Valderio Dettoni Zahra Toossi W. Henry Boom Reynaldo Dietze Jerrold J. Ellner Christina S. Hirsch 《Clinical and Vaccine Immunology : CVI》2002,9(4):818-823
Sputum and serum from patients with active pulmonary tuberculosis (TB), healthy purified protein derivative-positive adults, and patients with bacterial pneumonia were collected to simultaneously assess local immunity in the lungs and peripheral blood. To determine whether cytokine profiles in sputum from TB patients and control subjects were a reflection of its cellular composition, cytospin slides were prepared in parallel and assessed for the presence of relative proportions of epithelial cells, neutrophils, macrophages, and T cells. Gamma interferon (IFN-γ) in sputum from TB patients was markedly elevated over levels for both control groups. With anti-TB therapy, IFN-γ levels in sputum from TB patients decreased rapidly and by week 4 of treatment were comparable to those in sputum from controls. Further, IFN-γ levels in sputum closely followed mycobacterial clearance. Although detected at fourfold-lower levels, IFN-γ immunoreactivities in serum followed kinetics in sputum. TNF-α, interleukin 8 (IL-8) and IL-6 also were readily detected in sputum from TB patients at baseline and responded to anti-TB therapy. In contrast to IFN-γ, however, TNF-α and IL-8 levels also were elevated in sputum from pneumonia controls. These data indicate that sputum cytokines correlate with disease activity during active TB of the lung and may serve as potential early markers for sputum conversion and response to anti-TB therapy. 相似文献
52.
53.
AIMS: The present study aimed to evaluate the relationship between intestinal inflammation, interferon-gamma (IFN-gamma) levels and intestinal levels of dopamine, its precursor l-3,4-dihydroxyphenylalanine (L-DOPA), and the activity of aromatic L-amino acid decarboxylase (AADC) activity along the digestive tract in a rat experimental model of colitis. METHODS: Colitis was induced by rectal administration of 2,4,6-trinitrobenzene sulphonic acid (TNBS). Catechol derivatives were assayed by means of HPLC-EC. RESULTS: It is shown that dopamine and noradrenaline levels in the distal colon (inflamed mucosa), but not in the ileum (non-inflamed mucosa), of TNBS-treated rats were markedly lower than in control animals. A slight decrease in L-DOPA tissue levels, no changes in AADC activity and an increase in plasma IFN-gamma levels accompanied this decrease in dopamine levels. Exposure of Caco-2 cells, a human intestinal epithelial cell line, to human IFN-gamma resulted in a concentration-dependent and long-lasting inhibition of L-DOPA uptake, which most likely explains the decrease in dopamine levels in the inflamed mucosa. CONCLUSION: Changes in tissue levels of noradrenaline and dopamine in experimental colitis in the rat follow a similar pattern to that observed in patients with Crohn's disease and ulcerative colitis. In this model of experimental colitis, the decrease in dopamine levels is most likely explained by the inhibitory effect of IFN-gamma on L-DOPA uptake by intestinal epithelial cells. 相似文献
54.
Multiclonal Leishmania braziliensis population structure and its clinical implication in a region of endemicity for American tegumentary leishmaniasis
下载免费PDF全文
![点击此处可从《Infection and immunity》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Schriefer A Schriefer AL Góes-Neto A Guimarães LH Carvalho LP Almeida RP Machado PR Lessa HA de Jesus AR Riley LW Carvalho EM 《Infection and immunity》2004,72(1):508-514
In Corte de Pedra (CP), northeastern Brazil, Leishmania braziliensis causes three distinct forms of American tegumentary leishmaniasis (ATL). To test the hypothesis that strain polymorphism may be involved in this disease spectrum and accurately characterize the parasite population structure in CP, we compared one L. major, two non-CP L. braziliensis, one CP L. amazonensis, and 45 CP L. braziliensis isolates, obtained over a 10-year period from localized cutaneous, mucosal, and disseminated leishmaniasis patients, with randomly amplified polymorphic DNA (RAPD). Electrophoretic profiles were mostly unique across species. All typing protocols revealed polymorphism among the 45 CP L. braziliensis isolates, which displayed eight different RAPD patterns and greater than 80% overall fingerprint identity, attesting to the adequacy of the tools to assess strain variability in CP's geographically limited population of parasites. The dendrogram based on the sum of RAPD profiles of each isolate unveiled nine discrete typing units clustered into five clades. Global positioning showed extensive overlap of these clades in CP, precluding geographic sequestration as the mechanism of the observed structuralization. Finally, all forms of ATL presented a statistically significant difference in their frequencies among the clades, suggesting that L. braziliensis genotypes may be accompanied by specific disease manifestation after infection. 相似文献
55.
The development of Babesia equi in salivary glands of adult female Boophilus microplus was observed under a light microscope using semithin sections stained with toluidine blue. Engorged nymphs were obtained
from splenectomized foals experimentally infected with B. equi. As adults, they were then fed on rabbits for 5 days and the salivary glands of manually collected individuals were removed
at intervals of 24 h. Sporozoites were found in type III granular acini cells between the 2nd and 5th days following feeding
on the rabbits. Sporoblasts and sporozoites were observed in the same or adjacent acini cells in all the glands examined.
The formation of the sporozoites occurred following the multiple division of the sporoblasts through a process of radial budding
from the periphery of bodies resulting from multiple fission. Sporozoites were detected in smears of adult males stained with
Giemsa, between the 2nd and 5th days following feeding by the ticks. Adults of B. microplus, fed during the nymphal phase on foals with patent parasitemia, transmitted sporozoites of B. equi to a splenectomized foal. The role of B. microplus in the transmission and epidemiology of B. equi is discussed.
Received: 16 June 1997 / Accepted: 2 September 1997 相似文献
56.
57.
Bruna Velasques Sergio Machado Cláudio Elidio Portella Julio Guilherme Silva Luis F.H. Basile Mauricio Cagy Roberto Piedade Pedro Ribeiro 《Neuroscience letters》2007
The present experiment aimed at investigating electrophysiologic changes observed as beta band asymmetry, by Quantitative Electroencephalography (qEEG), when individuals performed a reaching motor task (catching a ball in free fall). The sample was composed of 23 healthy individuals, of both sexes, with ages varying between 25 and 40 years old. All the subjects were right handed. A two-way ANOVA was applied for the statistical analysis, to verify the interaction between task moment (i.e., 2 s before and 2 s after ball's fall) and electrode (i.e., frontal, central and temporal regions). The first analysis compared electrodes placed over the somatosensory cortex. Central sites (C3–C4) were compared with temporal regions (T3–T4). The results showed a main effect for moment and position. The second analysis was focused over the premotor cortex, which was represented by the electrodes placed on the frontal sites (F3–F4 versus F7–F8), and a main effect was observed for position. Taken together, these results show a pattern of asymmetry in the somatosensory cortex, associated with a preparatory mechanism when individuals have to catch an object during free fall. With respect to task moment, after the ball's fall, the asymmetry was reduced. Moreover, the difference in asymmetry between the observed regions were related to a supposed specialization of areas (i.e., temporal and central). The temporal region was associated with cognitive processes involved in the motor action (i.e., explicit knowledge). On the other hand, the central sites were related to the motor control mechanisms per se (i.e., implicit knowledge). The premotor cortex, represented by two frontal regions (i.e., F3–F4 versus F7–F8), showed a decrease on neural activity in the contralateral hemisphere (i.e., to the right hand). This result is in agreement with other experiments suggesting a participation of the frontal cortex in the planning of the apprehension task. This sensorimotor paradigm may contribute to the repertoire of tasks used to study clinical conditions such as depression, alzheimer and Parkinson diseases. 相似文献
58.
Silva ML Ornellas de Souza MH Ribeiro RC Land MG Boulhosa de Azevedo AM Vasconcelos F Otero L Vasconcelos Z Bouzas LF Abdelhay E 《Cancer Genetics and Cytogenetics》2002,137(2):85-90
We report the cytogenetic analysis of newly diagnosed Brazilian children with acute lymphocytic leukemia (ALL). We investigated 100 ALL cases from four different institutions in Rio de Janeiro. The frequency of chromosomal abnormalities was 92.3%. The karyotype profile and recurrent abnormalities found in this study do not differ essentially from those described by other groups. Although the Brazilian population is usually the product of different ethnic groups, our results show that the frequency of each recurrent abnormality is similar to that found in populations without our degree of diverse ethnic composition. Hence, our results suggest that childhood ALL in Brazil has the same biological features as that in developed countries, supporting the use of similar treatment protocols. We can therefore expect to reach the same survival rates in the coming years, depending possibly on the efficacy of the support therapy and extent of social assistance. 相似文献
59.
Missense mutation in a von Willebrand factor type A domain of the alpha 3(VI) collagen gene (COL6A3) in a family with Bethlem myopathy 总被引:2,自引:0,他引:2
Pan TC; Zhang RZ; Pericak-Vance MA; Tandan R; Fries T; Stajich JM; Viles K; Vance JM; Chu ML; Speer MC 《Human molecular genetics》1998,7(5):807-812
The Bethlem myopathy is a rare autosomal dominant proximal myopathy
characterized by early childhood onset and joint contractures. Evidence for
linkage and genetic heterogeneity has been established, with the majority
of families linked to 21q22.3 and one large family linked to 2q37,
implicating the three type VI collagen subunit genes, COL6A1 (chromosome
21), COL6A2 (chromosome 21) and COL6A3 (chromosome 2) as candidate genes.
Mutations of the invariant glycine residues in the triple-helical
domain-coding region of COL6A1 and COL6A2 have been reported previously in
the chromosome 21-linked families. We report here the identification of a
G-->A mutation in the N-terminal globular domain-coding region of COL6A3
in a large American pedigree (19 affected, 12 unaffected), leading to the
substitution of glycine by glutamic acid in the N2 motif, which is
homologous to the type A domains of the von Willebrand factor. This
mutation segregated to all affected family members, to no unaffected family
members, and was not identified in 338 unrelated Caucasian control
chromosomes. Thus mutations in either the triple-helical domain or the
globular domain of type VI collagen appear to cause Bethlem myopathy.
相似文献
60.
doublecortin is the major gene causing X-linked subcortical laminar heterotopia (SCLH) 总被引:12,自引:0,他引:12
des Portes V; Francis F; Pinard JM; Desguerre I; Moutard ML; Snoeck I; Meiners LC; Capron F; Cusmai R; Ricci S; Motte J; Echenne B; Ponsot G; Dulac O; Chelly J; Beldjord C 《Human molecular genetics》1998,7(7):1063-1070
Subcortical laminar heterotopia (SCLH), or 'double cortex', is a cortical
dysgenesis disorder associated with a defect in neuronal migration.
Clinical manifestations are epilepsy and mental retardation. This disorder,
which mainly affects females, can be inherited in a single pedigree with
lissencephaly, a more severe disease which affects the male individuals.
This clinical entity has been described as X- SCLH/LIS syndrome. Recently
we have demonstrated that the doublecortin gene, which is localized on the
X chromosome, is implicated in this disorder. We have now performed a
systematic mutation analysis of doublecortin in 11 unrelated females with
SCLH (one familial and 10 sporadic cases) and have identified mutations in
10/11 cases. The sequence differences include nonsense, splice site and
missense mutations and these were found throughout the gene. These results
provide strong evidence that loss of function of doublecortin is the major
cause of SCLH. The absence of phenotype-genotype correlations suggests that
X-inactivation patterns of neuronal precursor cells are likely to
contribute to the variable clinical severity of this disorder in females.
相似文献