首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   34155篇
  免费   3344篇
  国内免费   50篇
耳鼻咽喉   415篇
儿科学   1051篇
妇产科学   956篇
基础医学   4685篇
口腔科学   756篇
临床医学   3597篇
内科学   7121篇
皮肤病学   446篇
神经病学   2719篇
特种医学   1166篇
外国民族医学   9篇
外科学   4368篇
综合类   752篇
一般理论   28篇
预防医学   3939篇
眼科学   827篇
药学   2386篇
中国医学   37篇
肿瘤学   2291篇
  2021年   458篇
  2020年   254篇
  2019年   461篇
  2018年   521篇
  2017年   449篇
  2016年   426篇
  2015年   456篇
  2014年   719篇
  2013年   1105篇
  2012年   1559篇
  2011年   1614篇
  2010年   857篇
  2009年   761篇
  2008年   1424篇
  2007年   1566篇
  2006年   1513篇
  2005年   1404篇
  2004年   1282篇
  2003年   1254篇
  2002年   1272篇
  2001年   1129篇
  2000年   1179篇
  1999年   991篇
  1998年   357篇
  1997年   332篇
  1996年   357篇
  1995年   314篇
  1994年   318篇
  1993年   303篇
  1992年   917篇
  1991年   912篇
  1990年   825篇
  1989年   770篇
  1988年   680篇
  1987年   701篇
  1986年   701篇
  1985年   676篇
  1984年   549篇
  1983年   429篇
  1982年   332篇
  1981年   284篇
  1980年   257篇
  1979年   533篇
  1978年   328篇
  1977年   267篇
  1976年   280篇
  1975年   315篇
  1974年   353篇
  1973年   293篇
  1972年   273篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Psoriasis is a common chronic skin disease with a largely unknown pathogenesis. We demonstrate here that transgenic over-expression of interleukin (IL)-22 in mice resulted in neonatal mortality and psoriasis-like skin alterations including acanthosis and hypogranularity. This cutaneous phenotype may be caused by the direct influence of IL-22 on keratinocytes, since this cytokine did not affect skin fibroblasts, endothelial cells, melanocytes, or adipocytes. The comparison of cytokines with hypothesized roles in psoriasis pathogenesis determined that neither interferon (IFN)-γ nor IL-17, but only IL-22 and, with lower potency, IL-20 caused psoriasis-like morphological changes in a three-dimensional human epidermis model. These changes were associated with inhibited keratinocyte terminal differentiation and with STAT3 upregulation. The IL-22 effect on differentiation-regulating genes was STAT3-dependent. In contrast to IL-22 and IL-20, IFN-γ and IL-17 strongly induced T-cell and neutrophilic granulocyte-attracting chemokines, respectively. Tumor necrosis factor-α potently induced diverse chemokines and additionally enhanced the expression of IL-22 receptor pathway elements and amplified some IL-22 effects. This study suggests that different cytokines are players in the psoriasis pathogenesis although only the IL-10 family members IL-22 and IL-20 directly cause the characteristic epidermal alterations. Kerstin Wolk and Harald S. Haugen equally contributed to this work.  相似文献   
992.

Objectives

Gynaecological cancer is common. It is highly amenable to effective treatment, but thrombosis remains a common complication. There is controversy about whether microparticles (MPs), particularly tissue factor (TF) positive MPs, are increased in patients with malignancy and/or thrombosis. We therefore set out to investigate the relationship between MPs of different cellular origins, in patients with gynaecological malignancy. We hypothesised that patients with gynaecological malignancy have increased numbers of MPs. We measured MPs released by different cell types in these patients, and correlated the results with measures of haemostatic activation.

Methods

We measured the number of platelet-derived MPs (PMPs), endothelial cell-derived MPs (EMPs), leucocyte-derived MPs (LMPs), TF+ve MPs and annexin V (AV) binding MPs in fresh plasma by flow cytometry in patients with gynaecological malignancy and a control group. We also measured D-dimers, prothrombin fragments 1 and 2 (PF1&2) and thrombin–antithrombin (TAT) complexes as indirect markers of haemostatic activation.

Results

The number of MPs (from all cell types) was similar in the two patient groups, with no significant differences. The number of circulating TF+ve MPs was also similar between the two groups. D-dimers (p < 0.001) and PF1&2 (p = 0.009) were significantly higher in the malignant group reflecting haemostatic activation, but there was no correlation between the level of D-dimers, PF1&2 and TAT and MP numbers.

Conclusion

Using fresh samples, MPs were not significantly increased in patients with gynaecological malignancy. There was, however, evidence of haemostatic activation in the patients with malignancy, but no correlation between the number of MPs and haemostatic activation.  相似文献   
993.
It has been estimated that roughly 25% of all Deaf women in the United States are victims of intimate partner violence (Abused Deaf Women's Advocacy Services [ADWAS]), a figure similar to annual prevalence rates of 16% to 30% for intimate partners in the general population. One goal of the present study was to ascertain the prevalence of intimate partner violence victimization in a sample of Deaf female college students. When comparing the prevalence of physical assault, psychological aggression, and sexual coercion victimization to hearing female undergraduates, the current sample was approximately two times as likely to have experienced victimization in the past year.  相似文献   
994.
Parenteral opioids for pain relief during labor have been the subject of research for many decades. Commonly used systemic opioids provide limited pain relief during labor yet are used extensively for managing labor pain. These opioids share similar pharmacologic profiles but differ in potency, pharmacokinetics, and side effects. This article reviews the pharmacokinetics, pharmacodynamics, and clinical research related to the commonly used systemic labor pain analgesics morphine, meperidine, fentanyl, remifentanil, butorphanol, and nalbuphine.  相似文献   
995.
996.
Streptococcus pseudopneumoniae is a novel species belonging to the viridans group streptococci (VGS). Accurate species identification is challenging due to significant homology to other VGS. Whole-genome sequencing of S. pseudopneumoniae suggests it most likely originated from Streptococcus pneumoniae, sharing many of its virulence genes. There are several limitations when using traditional phenotypic identification methods to identify this organism. Other identification approaches include genotypic methods, pherotype analysis, and matrix-assisted laser desorption ionization–time of flight mass spectrometry. S. pseudopneumoniae is most commonly isolated from respiratory specimens, and its associations with chronic obstructive pulmonary disease and aspiration pneumonia have been previously described, suggesting that the organism treads the fine line between commensal and pathogen. Recent isolation of S. pseudopneumoniae from blood raises the important question of its clinical relevance. Antimicrobial susceptibility profiles of S. pseudopneumoniae indicate a higher level of resistance than other VGS. However, further information may be required to determine the choice of breakpoints.  相似文献   
997.
Cervical thymus mimics the thoracic thymus in supporting T‐cell development and exists in a subset of mice and humans. Importantly, it remains unknown whether the cervical thymus can generate T cells that are self‐tolerant in the complete absence of signals from the thoracic thymus. Using a fetal liver reconstitution model in thoracic thymectomized RAG?/? mice, we found that T cells could be generated without contribution from the thoracic thymus. However, these mice had decreased T cells, increased proportions of effector memory T cells and Treg phenotype cells, increased serum IgG1/2b, and increased frequency of T cells expressing IFN‐γ, IL‐17 or IL‐10. Half of the mice that received a thoracic thymectomy and fetal liver cells, unlike sham surgery controls, developed substantial morbidity with age. Disease was associated with lymphopenia‐driven activation rather than inherent defects in the cervical thymus, as both thoracic and cervical thymocytes could generate disease in lymphopenic recipients. Administration of the homeostatic cytokine IL‐7 caused a rapid, transient increase in T‐cell numbers and reduced the time to disease onset. Together the data suggests that the cervical thymus can function in the complete absence of the thoracic thymus; however, the T cells generated do not establish homeostasis.  相似文献   
998.
CD4‐mediated T‐cell help in the activation of CD8+ T cells and B cells, through linked‐recognition of antigenic determinants, is a long‐standing concept foundational to our understanding of immunity (presence of help) versus tolerance (lack of help). Surprisingly, this function of CD4+ T cells has not been extensively examined as a means to overcome immune tolerance of the self‐antigens made by tumor cells. Hesitation to employ this powerful mechanism may be due to the potential to cause unwanted autoimmune pathology. In this issue of the European Journal of Immunology, Snook et al. [Eur. J. Immunol. 2014. 44: 1956–1966] identify a state of split tolerance, showing that CD4+ T cells specific for a number of tumor‐associated self‐antigens are robustly tolerant, while their CD8+ T‐cell and B‐cell counterparts are far less tolerant. Furthermore, the authors demonstrate that provision of linked foreign helper epitopes, such as influenza hemagglutinin, substantially enhances both CD8+ T‐cell and B‐cell responses to tumor self‐antigens without causing any overt autoimmune pathology. These findings provide a strong rationale to employ foreign helper epitopes in cancer vaccines and highlight the need to fully explore therapeutic strategies that are based on well‐established immunologic concepts.  相似文献   
999.

Background

Participation in regular physical activity is among the most promising and cost effective strategies to reduce physical and cognitive decline and premature death. However, confusion remains about the amount, frequency, and duration of physical activity that is likely to provide maximum benefit as well as the way in which interventions should be delivered.

Aims

This paper aimed to review research on the impact of leisure-time and general physical activity levels on physical and cognitive decline in postmenopausal women. In a systematic review of the literature, empirical literature from 2009 to 2013 is reviewed to explore the potential impact of either commencing or sustaining physical activity on older women's health.

Results

All studies found that physical activity was associated with lower rates of cognitive and physical decline and a significant reduction in all-cause mortality. In this review we found that exercise interventions (or lifestyle activities) that improved cardiorespiratory exercise capacity showed the most positive impact on physical health.

Conclusions

Findings suggest that programs should facilitate and support women to participate in regular exercise by embedding physical activity programs in public health initiatives, by developing home-based exercise programs that require few resources and by creating interventions that can incorporate physical activity within a healthy lifestyle. The review also suggests that clinicians should consider prescribing exercise in a tailored manner for older women to ensure that it is of a high enough intensity to obtain the positive sustained effects of exercise.  相似文献   
1000.
T cell cytokine release assays are used to diagnose infectious diseases, but not autoimmune or allergic disease. Coeliac disease (CD) is a common T cell-mediated disease diagnosed by the presence of gluten-dependent intestinal inflammation and serology. Many patients cannot be diagnosed with CD because they reduce dietary gluten before medical workup. Oral gluten challenge in CD patients treated with gluten-free diet (GFD) mobilizes gluten-reactive T cells measurable by interferon (IFN)-γ enzyme-linked immunospot (ELISPOT) or major histocompatibility complex (MHC) class II tetramers. Immunodominant peptides are quite consistent in the 90% of patients who possess HLA-DQ2·5. We aimed to develop whole blood assays to detect gluten-specific T cells. Blood was collected before and after gluten challenge from GFD donors confirmed to have CD (n = 27, all HLA-DQ2·5+), GFD donors confirmed not to have CD (n = 6 HLA-DQ2·5+, 11 HLA-DQ2·5) and donors with CD not following GFD (n = 4, all HLA-DQ2·5+). Plasma IFN-γ and IFN-γ inducible protein-10 (IP-10) were measured by enzyme-linked immunosorbent assay (ELISA) after whole blood incubation with peptides or gliadin, and correlated with IFN-γ ELISPOT. No T cell assay could distinguish between CD patients and controls prior to gluten challenge, but after gluten challenge the whole blood IFN-γ ELISA and the ELISPOT were both 85% sensitive and 100% specific for HLA-DQ2·5+ CD patients; the whole blood IP-10 ELISA was 94% sensitive and 100% specific. We conclude that whole blood cytokine release assays are sensitive and specific for detection of gluten-reactive T cells in CD; further clinical studies addressing the utility of these tests in patients with an uncertain diagnosis of CD is warranted.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号