全文获取类型
收费全文 | 25993篇 |
免费 | 1976篇 |
国内免费 | 105篇 |
专业分类
耳鼻咽喉 | 295篇 |
儿科学 | 783篇 |
妇产科学 | 486篇 |
基础医学 | 2913篇 |
口腔科学 | 489篇 |
临床医学 | 2657篇 |
内科学 | 5656篇 |
皮肤病学 | 413篇 |
神经病学 | 2495篇 |
特种医学 | 908篇 |
外国民族医学 | 2篇 |
外科学 | 3995篇 |
综合类 | 589篇 |
一般理论 | 27篇 |
预防医学 | 2185篇 |
眼科学 | 668篇 |
药学 | 1671篇 |
中国医学 | 34篇 |
肿瘤学 | 1808篇 |
出版年
2023年 | 133篇 |
2022年 | 209篇 |
2021年 | 464篇 |
2020年 | 283篇 |
2019年 | 442篇 |
2018年 | 495篇 |
2017年 | 362篇 |
2016年 | 357篇 |
2015年 | 472篇 |
2014年 | 660篇 |
2013年 | 1025篇 |
2012年 | 1506篇 |
2011年 | 1459篇 |
2010年 | 871篇 |
2009年 | 774篇 |
2008年 | 1355篇 |
2007年 | 1480篇 |
2006年 | 1462篇 |
2005年 | 1452篇 |
2004年 | 1400篇 |
2003年 | 1293篇 |
2002年 | 1260篇 |
2001年 | 389篇 |
2000年 | 347篇 |
1999年 | 379篇 |
1998年 | 311篇 |
1997年 | 257篇 |
1996年 | 270篇 |
1995年 | 219篇 |
1994年 | 193篇 |
1993年 | 181篇 |
1992年 | 270篇 |
1991年 | 232篇 |
1990年 | 273篇 |
1989年 | 208篇 |
1988年 | 233篇 |
1987年 | 223篇 |
1986年 | 209篇 |
1985年 | 205篇 |
1984年 | 228篇 |
1983年 | 223篇 |
1982年 | 229篇 |
1981年 | 214篇 |
1980年 | 225篇 |
1979年 | 216篇 |
1978年 | 174篇 |
1977年 | 144篇 |
1976年 | 151篇 |
1974年 | 158篇 |
1973年 | 137篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
David Shveiky Loral Patchen Henry H. Chill Marieta Pehlivanova Helain J. Landy 《Journal of pediatric and adolescent gynecology》2019,32(2):135-138
Study Objective
The objective of this study was to describe prevalence and location of obstetric lacerations in adolescents.Design
Retrospective cohort study.Setting
We performed an analysis of the Consortium on Safe Labor database including tertiary care university-affiliated urban hospitals.Participants
All primiparous women who delivered vaginally were included.Interventions
Vaginal and perineal lacerations were compared between age groups 15 or younger, 16-21, 22-34, 35-39, and older than 40 years.Main Outcome Measures
Outcome measures included vaginal, perineal, labial, and periurethral lacerations. χ2 and Fisher exact tests were used as appropriate, with P < .05 considered significant.Results
A total of 9777 patients were included in the analysis. Young adolescents and adolescents had significantly higher rates of labial and periurethral lacerations compared with individuals aged 22-34 years. The prevalence of third- and fourth-degree perineal tears increased with age.Conclusion
Adolescent primiparous women are less likely to have severe perineal obstetric tears, but have higher rates of labial and periurethral tears. 相似文献992.
993.
Application of diffusional kurtosis imaging to detect occult brain damage in multiple sclerosis and neuromyelitis optica 下载免费PDF全文
Wenshu Qian Koon Ho Chan Edward S. Hui Chi Yan Lee Yong Hu Henry Ka‐Fung Mak 《NMR in biomedicine》2016,29(11):1536-1545
Multiple sclerosis (MS) and neuromyelitis optica (NMO) are two common types of inflammatory demyelinating disease of the central nervous system. Early distinction of NMO from MS is crucial but quite challenging. In this study, 13 NMO spectrum disorder patients (Expanded Disability Status Scale (EDSS) of 3.0 ± 1.7, ranging from 2 to 6.5; disease duration of 5.3 ± 4.7 years), 17 relapsing–remitting MS patients (EDSS of 2.6 ± 1.4, ranging from 1 to 5.5; disease duration of 7.9 ± 7.8 years) and 18 healthy volunteers were recruited. Diffusional kurtosis imaging was employed to discriminate NMO and MS patients at the early or stable stage from each other, and from healthy volunteers. The presence of alterations in diffusion and diffusional kurtosis metrics in normal‐appearing white matter (NAWM) and diffusely increased mean diffusivity (MD) in the cortical normal‐appearing gray matter (NAGM) favors the diagnosis of MS rather than NMO. Meanwhile, normal diffusivities and kurtosis metrics in all NAWM as well as increases in MD in the frontal and temporal NAGM suggest NMO. Our results suggest that diffusion and diffusional kurtosis metrics may well aid in discriminating the two diseases. 相似文献
994.
Malvindar K. Singh‐Bains Henry J. Waldvogel Richard L. M. Faull 《Brain pathology (Zurich, Switzerland)》2016,26(6):741-751
Huntington's disease (HD) is characterized by pronounced pathology of the basal ganglia, with numerous studies documenting the pattern of striatal neurodegeneration in the human brain. However, a principle target of striatal outflow, the globus pallidus (GP), has received limited attention in comparison, despite being a core component of the basal ganglia. The external segment (GPe) is a major output of the dorsal striatum, connecting widely to other basal ganglia nuclei via the indirect motor pathway. The internal segment (GPi) is a final output station of both the direct and indirect motor pathways of the basal ganglia. The ventral pallidum (VP), in contrast, is a primary output of the limbic ventral striatum. Currently, there is a lack of consensus in the literature regarding the extent of GPe and GPi neurodegeneration in HD, with a conflict between pallidal neurons being preserved, and pallidal neurons being lost. In addition, no current evidence considers the fate of the VP in HD, despite it being a key structure involved in reward and motivation. Understanding the involvement of these structures in HD will help to determine their involvement in basal ganglia pathway dysfunction in the disease. A clear understanding of the impact of striatal projection loss on the main neurons that receive striatal input, the pallidal neurons, will aid in the understanding of disease pathogenesis. In addition, a clearer picture of pallidal involvement in HD may contribute to providing a morphological basis to the considerable variability in the types of motor, behavioral, and cognitive symptoms in HD. This review aims to highlight the importance of the globus pallidus, a critical component of the cortical‐basal ganglia circuits, and its role in the pathogenesis of HD. This review also summarizes the current literature relating to human studies of the globus pallidus in HD. 相似文献
995.
Brighton H 《Artificial life》2002,8(1):25-54
A growing body of work demonstrates that syntactic structure can evolve in populations of genetically identical agents. Traditional explanations for the emergence of syntactic structure employ an argument based on genetic evolution: Syntactic structure is specified by an innate language acquisition device (LAD). Knowledge of language is complex, yet the data available to the language learner are sparse. This incongruous situation, termed the "poverty of the stimulus," is accounted for by placing much of the specification of language in the LAD. The assumption is that the characteristic structure of language is somehow coded genetically. The effect of language evolution on the cultural substrate, in the absence of genetic change, is not addressed by this explanation. We show that the poverty of the stimulus introduces a pressure for compositional language structure when we consider language evolution resulting from iterated observational learning. We use a mathematical model to map the space of parameters that result in compositional syntax. Our hypothesis is that compositional syntax cannot be explained by understanding the LAD alone: Compositionality is an emergent property of the dynamics resulting from sparse language exposure. 相似文献
996.
High resolution molecular phototyping of MICA and MICB alleles using sequence specific primers 总被引:6,自引:0,他引:6
Major histocompatibility complex (MHC) class I chain-related genes, MICA and MICB, are located centromeric to human leukocyte antigen B (HLA-B) on chromosome 6. In response to stress stimuli, MIC is expressed on epithelial, endothelial and fibroblast cells, but not lymphocytes and has been demonstrated to ligate the natural killer (NK) cell receptor, NKG2D. Nucleotide sequences of MICA and MICB are highly polymorphic and several methods have been established to identify these polymorphisms, including sequence-based typing and sequence-specific oligonucleotide probing. In this study we have developed a high-resolution polymerase chain reaction-sequence-specific primer (PCR-SSP) phototyping scheme that detects all WHO-recognized MICA alleles and all 12 MICB alleles. Our method will also recognize a MICA deletion haplotype and distinguish between MICA alleles with different binding affinities for NKG2D, encoded by a non-synonymous nucleotide substitution in codon 129. Furthermore, our scheme targets almost 90% of the dimorphic codon positions in exons 2, 3, and 4, which result in non-synonymous amino acid changes. This method can be used to determine MIC allele frequencies within different populations, as well as investigate MIC associations in cohorts of patients with autoimmune and infectious diseases and explore the impact of MIC on the survival of solid organ and stem cell transplants. 相似文献
997.
AIM: To evaluate recent trends in alcohol related deaths in the UK and to consider possible causative factors. DESIGN: Observational retrospective study of the database of the Office for National Statistics, alcohol consumption data reported by the General Household Survey, and other published data. SETTING: England, 1993-9. RESULTS: Deaths for each million of the population from alcohol related illness increased by 59% in men and 40% in women over the years 1993 to 1999. One subgroup of alcohol related deaths, ICD 571.3 (alcoholic liver damage unspecified), showed a 243% increase in men aged 40 to 49 years over the same period. Figures for younger men, and women in all age groups, showed less pronounced increases. There has been no associated rise in alcohol intake. There has been an increase in the incidence of hepatitis C virus (HCV) infection in recent years, and alcohol consumption in HCV positive individuals accelerates the progression to cirrhosis. Circumstantial evidence links the rise in HCV infection to the use of illicit drugs in the 1970s and 1980s, among those currently aged 40 to 59 years. CONCLUSIONS: The recent increase in alcohol related deaths cannot be solely explained by a change in drinking habits. It is suggested that this probably results from the rapid progression of alcoholic cirrhosis in people who have acquired HCV infection through intravenous drug use. Alcohol consumption in HCV positive individuals is firmly linked with a poor outcome. 相似文献
998.
Wagner A van der Klift H Franken P Wijnen J Breukel C Bezrookove V Smits R Kinarsky Y Barrows A Franklin B Lynch J Lynch H Fodde R 《Genes, chromosomes & cancer》2002,35(1):49-57
Genomic deletions of the MSH2 gene are a frequent cause of hereditary nonpolyposis colorectal cancer (HNPCC), a common hereditary predisposition to the development of tumors in several organs including the gastrointestinal and urinary tracts and endometrium. The mutation spectrum at the MSH2 gene is extremely heterogeneous because it includes nonsense and missense point mutations, small insertions and deletions leading to frameshifts, and larger genomic deletions, the latter representing approximately 25% of the total mutation burden. Here, we report the identification and molecular characterization of the first paracentric inversion of the MSH2 locus known to cause HNPCC. Southern blot analysis and inverse PCR showed that the centromeric and telomeric breakpoints of the paracentric inversion map within intron 7 and to a contig 10 Mb 3' of MSH2, respectively. Pathogenicity of the paracentric inversion was demonstrated by conversion analysis. The patient's lymphocytes were employed to generate somatic cell hybrids to analyze the expression of the inverted MSH2 allele in an Msh2-deficient rodent cellular background. The inversion was shown to abolish MSH2 expression by both northern and western analysis. This study confirms that Southern blot analysis still represents a useful and informative tool to screen for and identify complex genomic rearrangements in HNPCC. Moreover, monoallelic expression analysis represents an attractive approach to demonstrate pathogenicity of unusual mutations in autosomal dominant hereditary conditions. 相似文献
999.
1000.
Sputum Cytokine Levels in Patients with Pulmonary Tuberculosis as Early Markers of Mycobacterial Clearance 下载免费PDF全文
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