全文获取类型
收费全文 | 1493篇 |
免费 | 91篇 |
国内免费 | 13篇 |
专业分类
耳鼻咽喉 | 1篇 |
儿科学 | 33篇 |
妇产科学 | 30篇 |
基础医学 | 173篇 |
口腔科学 | 39篇 |
临床医学 | 112篇 |
内科学 | 373篇 |
皮肤病学 | 35篇 |
神经病学 | 65篇 |
特种医学 | 130篇 |
外科学 | 230篇 |
综合类 | 20篇 |
预防医学 | 162篇 |
眼科学 | 17篇 |
药学 | 71篇 |
中国医学 | 5篇 |
肿瘤学 | 101篇 |
出版年
2023年 | 10篇 |
2022年 | 26篇 |
2021年 | 30篇 |
2020年 | 28篇 |
2019年 | 46篇 |
2018年 | 52篇 |
2017年 | 36篇 |
2016年 | 29篇 |
2015年 | 39篇 |
2014年 | 42篇 |
2013年 | 48篇 |
2012年 | 60篇 |
2011年 | 67篇 |
2010年 | 60篇 |
2009年 | 46篇 |
2008年 | 66篇 |
2007年 | 86篇 |
2006年 | 93篇 |
2005年 | 71篇 |
2004年 | 61篇 |
2003年 | 54篇 |
2002年 | 55篇 |
2001年 | 48篇 |
2000年 | 40篇 |
1999年 | 41篇 |
1998年 | 24篇 |
1997年 | 24篇 |
1996年 | 21篇 |
1995年 | 13篇 |
1994年 | 14篇 |
1993年 | 18篇 |
1992年 | 11篇 |
1991年 | 16篇 |
1990年 | 19篇 |
1989年 | 20篇 |
1988年 | 16篇 |
1987年 | 11篇 |
1986年 | 32篇 |
1985年 | 11篇 |
1984年 | 8篇 |
1983年 | 10篇 |
1982年 | 10篇 |
1981年 | 6篇 |
1980年 | 8篇 |
1979年 | 6篇 |
1978年 | 7篇 |
1977年 | 11篇 |
1976年 | 7篇 |
1975年 | 12篇 |
1970年 | 6篇 |
排序方式: 共有1597条查询结果,搜索用时 15 毫秒
51.
de Oliveira MA de Leon AC Freire EC de Oliveira HC 《Acta obstetricia et gynecologica Scandinavica》2007,86(1):73-80
OBJECTIVE: To identify risk factors that are associated with the development of scar endometriosis after obstetric hysterotomies. The hypothesis is that early hysterotomy in pregnancy (before 22nd week) is the main risk factor for the development of scar endometriosis. METHODS: The authors conducted a case-control study between April 2000 and June 2003. A total of 117 women were selected, including 39 cases and 78 controls. Exposure and confounding variables were measured by a standardized questionnaire, which included sociodemographic characteristics, reproductive/physiologic history, past pathological history, history of obstetric surgeries, family history, and social history. The odds ratio (OR) and its 95% confidence interval (CI) were calculated using bivariate analysis for each possible risk factor. These estimates were obtained by multivariate analysis using unconditional logistic regression. Tests were made to assess the fit of the final model. RESULTS: In the multivariate analysis, positive associations were observed between scar endometriosis and hysterotomy type (early versus late: OR = 42.99; CI 8.77-210.81), amount of the menstrual blood flow (heavy versus light/normal: OR = 11.97; CI 2.35-60.82), and alcoholic consumption (yes versus no: OR = 5.31; CI 1.22-23.11). Negative association was observed between scar endometriosis and parity (OR = 0.61; CI 0.31-1.23), however it was not statistically significant (p>0.05). CONCLUSIONS: Early hysterotomy in pregnancy is the main risk factor for scar endometriosis. Increased menstrual flow and alcohol consumption are also risk factors, while high parity may be a protecting factor. 相似文献
52.
Marcos Vinicius Naves Bedo Davi Pereira dos Santos Marcelo Ponciano-Silva Paulo Mazzoncini de Azevedo-Marques André Ponce de León Ferreira de Carvalho Caetano TrainaJr 《Journal of digital imaging》2016,29(1):22-37
Content-based medical image retrieval (CBMIR) is a powerful resource to improve differential computer-aided diagnosis. The major problem with CBMIR applications is the semantic gap, a situation in which the system does not follow the users’ sense of similarity. This gap can be bridged by the adequate modeling of similarity queries, which ultimately depends on the combination of feature extractor methods and distance functions. In this study, such combinations are referred to as perceptual parameters, as they impact on how images are compared. In a CBMIR, the perceptual parameters must be manually set by the users, which imposes a heavy burden on the specialists; otherwise, the system will follow a predefined sense of similarity. This paper presents a novel approach to endow a CBMIR with a proper sense of similarity, in which the system defines the perceptual parameter depending on the query element. The method employs ensemble strategy, where an extreme learning machine acts as a meta-learner and identifies the most suitable perceptual parameter according to a given query image. This parameter defines the search space for the similarity query that retrieves the most similar images. An instance-based learning classifier labels the query image following the query result set. As the concept implementation, we integrated the approach into a mammogram CBMIR. For each query image, the resulting tool provided a complete second opinion, including lesion class, system certainty degree, and set of most similar images. Extensive experiments on a large mammogram dataset showed that our proposal achieved a hit ratio up to 10% higher than the traditional CBMIR approach without requiring external parameters from the users. Our database-driven solution was also up to 25% faster than content retrieval traditional approaches. 相似文献
53.
Qi X Kondoh K Yin H Wang M Ponce E Sun Y Grabowski GA 《Molecular genetics and metabolism》2002,76(3):189-200
Saposin C is a biological activator of acid beta-glucosidase (GCase), the lysosomal hydrolase with activity towards glucosylceramide (GC). In addition, saposin C possesses a functional domain that determines the in vitro and ex vivo neuritogenic effects of prosaposin, the precursor of saposins A, B, C, and D. The domains for enzymatic activation and neuritogenic function segregate in vitro, respectively, to the carboxyl- and amino-terminal halves of human and mouse saposin C. A chimeric mouse saposin C(1-8)B(8-28)C(30-80) was created to obliterate the neuritogenic region by substituting amino acids 9-29 of saposin C with amino acids 8-28 of saposin B. This saposin showed normal in vitro enzymatic activation effects toward GCase, but no neuritogenic activity. An altered prosaposin was made to contain the chimeric saposin C region. Expression of this altered or wild-type prosaposin was driven by the PGK-1 promoter as a transgene in prosaposin knock-out mice. In cultured fibroblasts from such mice, expressed saposins localized to the lysosomal compartments. Metabolic lipid labeling using L-[3-(14)C]serine showed retention or clearance of GC in prosaposin deficient or transgene reconstituted cells, respectively. In addition, sulfatide catabolism, that requires saposin B and arylsulfatase, was also normalized in prosaposin KO cells reconstituted with the transgenes. These data show that the transgenic prosaposins were expressed and processed to functional saposins in fibroblasts. These results also show that the enzymatic activation domain is located at carboxyl-terminal half of saposin C and functions only in the context of the general saposin structure. 相似文献
54.
V. Turinelli T. Marchal F. Ponce C. Bonnefont-Rebeix C. Fournel-Fleury 《Comparative clinical pathology》2005,13(3):109-118
Among 276 canine lymphomas referred to the Haematology–Cytology–Immunology laboratory of the Lyon Veterinary School between 1997 and 2003, there were five aggressive large granular lymphocyte (LGL) malignancies. The five dogs were clinically examined and followed up. Cytological and histological analyses of the liver, spleen, lymph nodes, intestine and bone marrow were performed. The immunophenotype and proliferation index were established. The most significant clinical finding was that of an aggressive clinical course, the presence of hepatomegaly and/or splenomegaly, an abdominal lymphadenopathy, anaemia in four cases and blood and bone-marrow involvement in two cases. The cytological presentation was a diffuse infiltration of atypical, large granular lymphoid cells. Two cases were of the null type (CD3–, CD79a–, CD4–, CD8–), and three were of the T-cell type (CD3+, CD79a–, CD4–, CD8+). The proliferation index was high in all cases, with a median of 54.4%. The histological presentation of the null-type cases was an infiltration of the livers portal triads and the spleens red pulp. The T CD8+ cases showed two different patterns, characterised by infiltration: in the first, of all the intestines layers, the livers portal triads, the spleens red pulp and the lymph nodes and, in the second, infiltration of the livers sinusoids, the spleens red pulp. Although these aggressive LGL lymphomas are still poorly known, they may be compared to three types of human lymphoma: aggressive NK cell lymphoma/leukemia, hepatosplenic T-cell lymphoma and enteropathy-type T-cell lymphoma. 相似文献
55.
56.
Krummenacher C Baribaud F Ponce de Leon M Baribaud I Whitbeck JC Xu R Cohen GH Eisenberg RJ 《Virology》2004,322(2):286-299
The herpesvirus entry mediator A (HVEM/HveA) and nectin-1 (HveC/CD111) are two major receptors for herpes simplex virus (HSV). Although structurally unrelated, both receptors can independently mediate entry of wild-type (wt) HSV-1 and HSV-2 by interacting with the viral envelope glycoprotein D (gD). Laboratory strains with defined mutations in gD (e.g. rid1) do not use HVEM but use nectin-2 (HveB/CD112) for entry. The relative usage of HVEM and nectin-1 during HSV infection in vivo is not known. In the absence of a defined in vivo model, we used in vitro approaches to address this question. First, we screened HSV clinical isolates from various origins for receptor tropism and found that all used both HVEM and nectin-1. Second, we determined the numbers of surface receptors on various susceptible and resistant cell lines as well as on primary fibroblasts derived from an individual with cleft lip/palate ectodermal dysplasia (CLPED1). Although CLPED1 cells can only express a defective form of nectin-1, they allowed entry of wild type and mutant HSV strains by usage of either HVEM or nectin-2. Finally, we compared the ability of HVEM and nectin-1 to mediate entry when expressed at varying cell surface densities. Both receptors showed a direct relationship between the number of receptors and HSV susceptibility. Direct comparison of receptors suggests that nectin-1 is more efficient at promoting entry than HVEM. Overall, our data suggest that both receptors play a role during HSV infection in vivo and that both are highly efficient even at low levels of expression. 相似文献
57.
Sharon LR Kardia Reagan J Kelly Mehdi A Keddache Bruce J Aronow Gregory A Grabowski Harvey S Hahn Karen L Case Lynne E Wagoner Gerald W DornII Stephen B Liggett 《BMC medical genetics》2008,9(1):93
Background
Persistent stimulation of cardiac β1-adrenergic receptors by endogenous norepinephrine promotes heart failure progression. Polymorphisms of this gene are known to alter receptor function or expression, as are polymorphisms of the α2C-adrenergic receptor, which regulates norepinephrine release from cardiac presynaptic nerves. The purpose of this study was to investigate possible synergistic effects of polymorphisms of these two intronless genes (ADRB1 and ADRA2C, respectively) on the risk of death/transplant in heart failure patients. 相似文献58.
Transmission of Pneumocystis carinii DNA from a patient with P. carinii pneumonia to immunocompetent contact health care workers 总被引:1,自引:0,他引:1
Vargas SL Ponce CA Gigliotti F Ulloa AV Prieto S Muñoz MP Hughes WT 《Journal of clinical microbiology》2000,38(4):1536-1538
The transmission of Pneumocystis carinii from person to person was studied by detecting P. carinii-specific DNA in prospectively obtained noninvasive deep-nasal-swab samples from a child with a documented P. carinii pneumonia (PCP), his mother, two contact health care workers, and 30 hospital staff members who did not enter the patient's room (controls). Nested-DNA amplification was done by using oligonucleotide primers designed for the gene encoding the mitochondrial large subunit rRNA of rat P. carinii (P. carinii f. sp. carinii) that amplifies all forms of P. carinii and internal primers specific for human P. carinii (f. sp. hominis). P. carinii f. sp. hominis DNA was detected in samples from the patient and all of his contacts versus none of the 30 hospital staff members. The results, as previously shown in murine models of P. carinii pneumonia, document that person-to-person transmission of P. carinii is possible. This observation suggests that immunocompromised patients not on PCP prophylaxis should not enter the room of a patient with PCP, and it also raises the question as to whether healthy contacts can transmit the disease to immunocompromised patients at risk. 相似文献
59.
Maternal ethanol exposure during lactation induces behavioral alterations in offspring, including disruptions in motor skills and heightened ethanol ingestion during adolescence. These behavioral outcomes appear to partially depend on ethanol-induced disruptions in maternal care. The present study assessed motor skills and ethanol intake in adolescent rats raised by dams that had been repeatedly given ethanol during lactation. Female rats (postpartum days [PDs] 3-13) were administered ethanol (0.5, 1.5, or 2.5 g/kg) or vehicle every other day and allowed to freely interact with their pups. During adolescence, the offspring were evaluated for motor coordination (accelerating rotarod test) and oral ethanol self administration. The lowest maternal ethanol dose (0.5 g/kg) mildly affected motor performance, whereas the higher doses (1.5 and 2.5 g/kg) resulted in motor coordination impairment and greater ethanol intake. Maternal care behavior was affected by ethanol in a dose-dependent fashion. These results indicate that early experience with ethanol during lactation, even when the drug dosage is kept relatively low, leads to long-term consequences in offspring. Dose-response effects on maternal care behavior (i.e., nest building, crouching) may underlie disruptions in motor development and greater ethanol intake resulting from these early ethanol experiences. 相似文献
60.
J. Ponce Lorenzo A. Segura Huerta R. Díaz Beveridge A. Giménez Ortiz F. Aparisi Aparisi T. Fleitas Kanonnikoff P. Richart Aznar H. de la Cueva Sapiña J. Montalar Salcedo 《Clinical & translational oncology》2007,9(7):452-458
Purpose To identify clinical and biologic variables with significant impact on survival in patients with carcinomas of an unknown
primary site (CUP) and to develop a simple prognostic model.
Patients and methods In this retrospective study, univariate and multivariate prognostic factors analyses were conducted in a population of 100
patients with CUP. Patients with features requiring well defined treatments had previously been excluded.
Results Overall survival (OS) was significantly related to the following pretreatment adverse prognostic clinical factors: a poor
performance status (2 or 3), weight loss more than 10% in the last six months, the presence of liver metastases and more than
two metastatic sites. Two biological parameters predicted a significantly shorter survival: elevated serum levels of alkaline
phosphatase and of lactate dehydrogenase. In the multivariate analysis, only two independent adverse prognostic parameters
were retained: a poor performance status and the presence of liver metastases. We developed a prognostic model for OS based
on the following subgroups: good prognosis (PS 0 or 1 and absence of liver metastases), intermediate prognosis (PS≥2 or presence
of liver metastases) and poor prognosis (PS≥2 or presence of liver metastases). Median OS for the three groups was 10.8, 4
and 1.9 months respectively, p<0.0001.
Conclusion A simple prognostic model using performance status and presence of liver metastases was developed. It allowed the assignment
of patients into three subgroups with different outcomes. Treatment strategies could be adapted for each subgroup. We think
that this prognostic model could be useful and should be validated in other patient series. 相似文献