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   3473篇
  免费   215篇
  国内免费   4篇
耳鼻咽喉   16篇
儿科学   86篇
妇产科学   124篇
基础医学   447篇
口腔科学   25篇
临床医学   407篇
内科学   566篇
皮肤病学   63篇
神经病学   375篇
特种医学   46篇
外科学   494篇
综合类   22篇
一般理论   2篇
预防医学   487篇
眼科学   44篇
药学   205篇
中国医学   1篇
肿瘤学   282篇
  2024年   2篇
  2023年   49篇
  2022年   78篇
  2021年   146篇
  2020年   97篇
  2019年   142篇
  2018年   145篇
  2017年   95篇
  2016年   123篇
  2015年   104篇
  2014年   161篇
  2013年   224篇
  2012年   322篇
  2011年   317篇
  2010年   149篇
  2009年   114篇
  2008年   212篇
  2007年   223篇
  2006年   175篇
  2005年   201篇
  2004年   158篇
  2003年   134篇
  2002年   121篇
  2001年   19篇
  2000年   6篇
  1999年   14篇
  1998年   19篇
  1997年   12篇
  1996年   4篇
  1995年   15篇
  1994年   8篇
  1993年   13篇
  1992年   7篇
  1991年   14篇
  1990年   3篇
  1989年   5篇
  1988年   2篇
  1987年   4篇
  1986年   4篇
  1985年   4篇
  1984年   3篇
  1983年   9篇
  1982年   7篇
  1981年   4篇
  1980年   3篇
  1978年   6篇
  1975年   4篇
  1943年   1篇
  1942年   1篇
  1939年   1篇
排序方式: 共有3692条查询结果,搜索用时 15 毫秒
61.
62.
PurposeHaving an emergency plan may reduce negative effects of disaster on the health of postpartum women and their infants. However, little is known about the prevalence of emergency plans among postpartum women. In 2009, Arkansas added a question to the Pregnancy Risk Assessment Monitoring System surveillance system about whether women who gave birth that year had an emergency plan. In this study, we first describe the sociodemographic characteristics, disaster experience, and region of residence of postpartum women in Arkansas who indicated that they had an emergency plan for their families in 2009, and second, examine associations between sociodemographic characteristics and disaster experience and the presence of an emergency plan.MethodsMultivariable logistic regression (n = 1,173) was conducted to examine associations between maternal race/ethnicity, sociodemographic characteristics, region of residence, disaster experience, and having a disaster plan. We adjusted for maternal education, federal poverty level, and family size in our final model.FindingsForty-eight percent (n = 559) of women reported having an emergency plan. Hispanic women were less likely to report having a plan compared with non-Hispanic White women (n = 102 [10%]; adjusted prevalence ratio [aPR], 0.6; 95% confidence interval [CI], 0.4–0.9). Families with five or more members were more likely to have a plan compared with smaller families (n = 123 [11%]; aPR, 1.3; 95% CI, 1.1–1.6).ConclusionsPolicymakers and public health practitioners can use these results to promote emergency planning among postpartum women in Arkansas, with special outreach to postpartum women who are Hispanic or have smaller families.  相似文献   
63.
64.
65.
66.
Coronavirus disease 2019 (COVID-19) continues to impact older adults disproportionately with respect to serious consequences ranging from severe illness and hospitalization to increased mortality risk. Concurrently, concerns about potential shortages of healthcare professionals and health supplies to address these issues have focused attention on how these resources are ultimately allocated and used. Some strategies, for example, misguidedly use age as an arbitrary criterion that disfavors older adults in resource allocation decisions. This is a companion article to the American Geriatrics Society (AGS) position statement, “Resource Allocation Strategies and Age-Related Considerations in the COVID-19 Era and Beyond.” It is intended to inform stakeholders including hospitals, health systems, and policymakers about ethical considerations that should be considered when developing strategies for allocation of scarce resources during an emergency involving older adults. This review presents the legal and ethical background for the position statement and discusses these issues that informed the development of the AGS positions: (1) age as a determining factor, (2) age as a tiebreaker, (3) criteria with a differential impact on older adults, (4) individual choices and advance directives, (5) racial/ethnic disparities and resource allocation, and (6) scoring systems and their impact on older adults. It also considers the role of advance directives as expressions of individual preferences in pandemics. J Am Geriatr Soc 68:1143–1149, 2020.  相似文献   
67.
The Janus kinase 2 (JAK2) V617F mutation is the primary pathogenic mutation in patients with Philadelphia chromosome-negative myeloproliferative neoplasms (MPNs). Although thrombohemorrhagic incidents are the most common causes of morbidity and mortality in patients with MPNs, the events causing these clotting abnormalities remain unclear. To identify the cells responsible for the dysfunctional hemostasis, we used transgenic mice expressing JAK2V617F in specific lineages involved in thrombosis and hemostasis. When JAK2V617F was expressed in both hematopoietic and endothelial cells (ECs), the mice developed a significant MPN, characterized by thrombocytosis, neutrophilia, and splenomegaly. However, despite having significantly higher platelet counts than controls, these mice showed severely attenuated thrombosis following injury. Interestingly, platelet activation and aggregation in response to agonists was unaltered by JAK2V617F expression. Subsequent bone marrow transplants revealed the contribution of both endothelial and hematopoietic compartments to the attenuated thrombosis. Furthermore, we identified a potential mechanism for this phenotype through JAK2V617F-regulated inhibition of von Willebrand factor (VWF) function and/or secretion. JAK2V617F+ mice display a condition similar to acquired von Willebrand syndrome, exhibiting significantly less high molecular weight VWF and reduced agglutination to ristocetin. These findings greatly advance our understanding of thrombohemorrhagic events in MPNs and highlight the critical role of ECs in the pathology of hematopoietic malignancies.Myeloproliferative neoplasms (MPNs) are clonal hematopoietic stem cell disorders, characterized by significant increases in one or more myeloid-cell lineages. Mutations in the Janus kinase 2 (JAK2) and MPL genes are common in the majority of Philadelphia chromosome-negative (Ph) MPNs, which include polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF). By far the most frequent mutation in MPNs is JAK2V617F (14), which occurs in the highly conserved autoinhibitory JAK homology (JH) 2 domain, causing hyperactive kinase activity and hyperproliferation of myeloid progenitor cells, leading to overproduction of red blood cells (RBCs), platelets, and leukocytes. Although ET and PV have a relatively benign clinical course, patients’ life expectancy can be severely reduced by bleeding or thrombosis, the manifestations of which are significantly more common than other MPN-related complications such as myelofibrosis and acute leukemic transformation (5). The frequency and nature of thrombotic and hemorrhagic events vary greatly depending on disease phenotype and patient history. Data taken from a number of previous studies indicate that the probability of major thrombosis ranges between 8–29% (ET) and 11–39% (PV) whereas the incidence of bleeding at initial presentation is less frequent than thrombosis, ranging between 3–18% (ET) and 3–8% (PV) (68).A number of abnormalities that could potentially contribute to this prothrombotic phenotype have been identified in the blood and vascular cells of JAK2V617F+ MPN patients. Much work has focused on defining platelet abnormalities, including increased expression of membrane proteins such as P-selectin and tissue factor (TF), which would prime platelets for activation and increase levels of platelet-activation markers and platelet factor 4 (PF4) in the plasma (912). Interestingly, however, aggregation studies show a decreased response to ADP and epinephrine in platelets isolated from patients with ET and PV compared with controls (10). Furthermore, no correlation has been made between severity of thrombocytosis in ET patients and increased risk of thrombosis (6, 13). In contrast, extreme thrombocytosis (platelets >1,500 × 109/L) is thought to contribute to a hemorrhagic phenotype in ET patients, and is commonly attributed to the development of acquired von Willebrand syndrome (AVWS) (11, 12, 14), where the increased platelets bind to highly prothrombotic, ultralarge von Willebrand factor (VWF) multimers, removing them from the plasma (15).Recent studies suggest that leukocytosis is a potential thrombotic risk factor in young PV and ET patients, possibly through the interactions of leukocytes, especially neutrophils, with platelets and endothelial cells (ECs) (16, 17) or the production of prothrombotic molecules such as TF. Increased basal activation of neutrophils has been shown in PV and ET patients, including elevated expression of CD11b and levels of neutrophil proteases in the plasma, both of which are prothrombotic (9, 18, 19). Studies have also shown increased activation of vascular ECs in JAK2V617F+ MPN patients. Increased P- and E-selectin levels in the plasma, coupled with decreased levels of nitric oxide (NO), could conceivably contribute to a prothrombotic phenotype. Furthermore, JAK2V617F+ ECs have recently been reported in a subpopulation of MPN patients, and EC expression was coupled with an increased risk of thrombosis (20, 21). Taken together, previous studies describe physiological abnormalities in a number of cell types in JAK2V617F+ MPN patients, all of which could contribute toward increased thrombosis and/or bleeding. However, these data are often contradictory and fail to definitively explain the mechanism/s responsible for the development of thrombohemorrhagic disease.Here, we used FF1 transgenic mice (22) to express human JAK2V617F in specific lineages to determine which cells are responsible for the thrombohemorrhagic manifestations seen in patients with MPNs. FF1 mice were crossed with Pf4-Cre or Tie2-Cre mice to express JAK2V617F specifically in platelets alone, or in hematopoietic cells and ECs, respectively (2328). These models have provided us with an unparalleled opportunity to determine the specific role/s of JAK2V617F in pathological thrombosis and hemostasis.  相似文献   
68.
A growing literature attests to deficits in social and romantic life quality in people with elevated social anxiety, but no research to date has explored how intense intimate encounters influence social anxiety symptoms. This study investigated whether the presence and quality of sexual activity on a given day predicted less social anxiety and negative cognitions on a subsequent day. We also explored whether the benefits of sexual activity would be stronger for more socially anxious individuals. Over 21 days, 172 undergraduate students described the presence and quality of sexual activity, social anxiety symptoms, and use of social comparisons on the day in question. Time-lagged analyses determined that being sexually active on one day was related to less social anxiety symptoms and the generation of fewer negative social comparisons the next day. Furthermore, more intense experiences of pleasure and connectedness during sex predicted greater reductions in social anxiety the next day for people high in trait social anxiety, compared to those low in trait social anxiety. These results were similar regardless of whether sex occurred in the context of romantic relationships or on weekdays versus weekends. The results suggest that sexual activity, particularly when pleasurable and intimate, may mitigate some of the social anxiety and negative comparisons frequently experienced by people with high trait social anxiety.  相似文献   
69.
70.
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