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   64665篇
  免费   4800篇
  国内免费   280篇
耳鼻咽喉   613篇
儿科学   2217篇
妇产科学   1671篇
基础医学   9663篇
口腔科学   1045篇
临床医学   6449篇
内科学   14016篇
皮肤病学   1305篇
神经病学   7055篇
特种医学   1495篇
外国民族医学   1篇
外科学   6007篇
综合类   480篇
现状与发展   1篇
一般理论   49篇
预防医学   6217篇
眼科学   1057篇
药学   4815篇
中国医学   151篇
肿瘤学   5438篇
  2023年   724篇
  2022年   1521篇
  2021年   2601篇
  2020年   1489篇
  2019年   1938篇
  2018年   2146篇
  2017年   1746篇
  2016年   1903篇
  2015年   2106篇
  2014年   2745篇
  2013年   3476篇
  2012年   5119篇
  2011年   5084篇
  2010年   2660篇
  2009年   2336篇
  2008年   3953篇
  2007年   3908篇
  2006年   3593篇
  2005年   3320篇
  2004年   3085篇
  2003年   2762篇
  2002年   2496篇
  2001年   593篇
  2000年   568篇
  1999年   583篇
  1998年   453篇
  1997年   402篇
  1996年   300篇
  1995年   275篇
  1994年   282篇
  1993年   225篇
  1992年   353篇
  1991年   310篇
  1990年   315篇
  1989年   325篇
  1988年   295篇
  1987年   277篇
  1986年   264篇
  1985年   275篇
  1984年   250篇
  1983年   203篇
  1982年   194篇
  1981年   161篇
  1980年   148篇
  1979年   173篇
  1978年   155篇
  1977年   129篇
  1976年   118篇
  1974年   121篇
  1973年   126篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
The research was designed to investigate the moderating effect of some personality traits on subjective distress caused by daily hassles. The traits were internal locus of control, repression, ego strength, and barrier (as studied and defined by S. Fisher). The last two variables were negatively correlated both with the somatic and emotional distress indications and with the frequency of hassles reportED; internal locus of control showed an inverse relationship only with frequency of hassles. The hypothesis is formulated that ego strength and barrier are personality factors influencing not only the outcomes of coping (ie the stress response), but also event appraisal.  相似文献   
72.
This study aimed to investigate whether endothelial cells are damaged and to evaluate fibrinolytic system function in patients with type 2 diabetes. For this proposal, plasma levels of von Willebrand factor (an endothelial marker of injury), homocysteine (an inductor of endothelial injury), D-dimer (a marker of coagulation cascade activation) and plasminogen activator inhibitor-1 (a fibrinolysis marker) were measured in individuals with both type 2 diabetes and high blood pressure, with type 2 diabetes, with high blood pressure and in healthy control individuals. No significant differences among groups were observed for von Willebrand factor and homocysteine plasma levels. The type 2 diabetes and high blood pressure group presented a significant difference to the other groups for D-dimer and also presented high values for plasminogen activator inhibitor-1. The high blood pressure group and type 2 diabetes group presented separately higher values of plasminogen activator inhibitor-1 compared with the control group. High levels of D-dimer and plasminogen activator inhibitor-1 in patients with type 2 diabetes and high blood pressure with normoalbuminuria therefore indicate a state of hypercoagulability and hypofibrinolysis, despite no evident microvascular injury supported by normal levels of von Willebrand factor and homocysteine.  相似文献   
73.
PURPOSE: The purpose of the study was to evaluate the incidence of incontinence pad use among patients admitted to medical wards, the reasons why nurses decide to use an incontinence pad, the extent to which the use of pads is avoidable, and the outcome of inappropriate pad use after discharge from the hospital. METHODS: A prospective cohort study was conducted; patients admitted to medical wards were observed during hospitalization and a 7-day follow-up period after discharge. SUBJECTS AND SETTING: The study was conducted in 2 acute-care units in Northern Italy. All new patients admitted to the units were recruited. RESULTS: At the time of admission to the hospital, in addition to the 120 patients who already used incontinence pads, there was a 34% incidence of new cases (98/286). The most frequent reason why nurses decided to use this aid was incontinence caused by space-time disorientation, followed by limited mobility, incontinence, patient request, nursing shortage, and involuntary urine leakage not perceived by patient. Seventy patients out of 208 used incontinence pads unnecessarily for a total of 544 days. CONCLUSIONS: Decisions about the use of the incontinence pads are not always consistent with research-based or literature-based suggestions. Nurses should develop clinical guidelines or protocols for the appropriate use of incontinence pads.  相似文献   
74.
We describe the case of a recipient of an implantable cardioverter defibrillator with multiple syncopal episodes due both to superior vena cava obstruction and electrical instability. These complications occurred in the presence of two transvenous implantable cardioverter defibrillator leads. The patient has been managed conservatively with anticoagulants and new antiarrhythmic drugs with improvement in both his clinical problems.  相似文献   
75.
Melanoma consists 4-5 % of all skin cancers, but it contributes to 71-80 % of skin cancers deaths. UV light affects cell and tissue homeostasis due to its damaging effects on DNA integrity and modification of expression of a plethora of genes. DNA repair systems protect cells from UV-induced lesions. Several animal models of melanoma have been developed (Xiphophorus, Opossum Monodelphis domestica, mouse models and human skin engrafts into other animals). This review discusses possible links between UV and genes significantly related to melanoma but does not discuss melanoma genetics. These include oncogenes, tumor suppressor genes, genes related to melanocyte-keratinocyte and melanocyte-matrix interaction, growth factors and their receptors, CRH, ACTH, α-MSH, glucocorticoids, ID1, NF-kappaB and vitamin D3.  相似文献   
76.
77.
OBJECTIVE: The aim of this study was to identify lymphocyte subpopulations in middle ear effusions, peripheral blood, and adenoids in children suffering from otitis media with effusion. SETTING: Tertiary referral center. PATIENTS: Thirty-three children (55 ears) undergoing myringotomy for otitis media with effusion. METHODS: CD3, CD4, CD8, CD19, and natural killer cell populations were investigated in middle ear effusion, peripheral blood, and adenoids using a three-color monoclonal antibody and flow cytometry method for quantitative estimation. RESULTS: T cells (CD3) are dominating lymphocytes in middle ear effusion. Among T lymphocytes, the majority are those of the helper type (CD4). The dominating isoform among CD4 lymphocytes are memory cells (CD4CD45RO); among CD8 lymphocytes, naive cells (CD8CD45RA). The percentage of CD4 cells, CD8 cells, and the CD4/CD8 ratio was significantly higher in middle ear effusions than in blood. The percentage of memory CD4 lymphocytes and naive CD8 lymphocytes was significantly lower in the middle ear effusion. Lymphocyte subsets were compared between 22 pairs of effusions from each patient. The percentage of each type of cell did not differ significantly. CONCLUSION: The results of this study indicate local regulation of the lymphocyte profile in middle ear effusions and the same phase of immune response in two ears of the same patient.  相似文献   
78.
We tested the hypothesis that astrocytic matrix metalloproteinase-9 (MMP-9) mediates hemorrhagic brain edema. In a clinical case of hemorrhagic stroke, MMP-9 co-localized with astrocytes and neurons in peri-hematoma areas. In a mouse model where blood was injected into striatum, MMP-9 was colocalized with astrocytes surrounding the hemorrhagic lesion. Because MMP-9 is present in blood as well as brain, we compared four groups of wild type (WT) and MMP-9 knockout (KO) mice: WT blood injected into WT brain, KO blood into KO brain, WT blood into KO brain, and KO blood into WT brain. Gel zymography showed that MMP-9 was elevated in WT hemorrhagic brain tissue but absent from KO hemorrhagic brain tissue. Edematous water content was elevated when WT blood was injected into WT brain. However, edema was ameliorated when MMP-9 was absent in either blood or brain or both. To further assess the mechanisms involved in astrocytic induction of MMP-9, we next examined primary mouse astrocyte cultures. Exposure to hemoglobin rapidly upregulated MMP-9 in conditioned media within 1 to 24 h. Hemoglobin-induced MMP-9 was reduced by the free radical scavenger U83836E. Taken together, these data suggest that although there are large amounts of MMP-9 in blood, hemoglobin-induced oxidative stress can trigger MMP-9 in astrocytes and these parenchymal sources of matrix degradation may also be an important factor in the pathogenesis of hemorrhagic brain edema.  相似文献   
79.
Opioid tolerance and opioid-induced hyperalgesia are conditions that negatively affect pain management. Tolerance is defined as a state of adaptation in which exposure to a drug induces changes that result in a decrease of the drug's effects over time. Opioid-induced hyperalgesia occurs when prolonged administration of opioids results in a paradoxic increase in atypical pain that appears to be unrelated to the original nociceptive stimulus. Complex intracellular neural mechanisms, including opioid receptor desensitization and down-regulation, are believed to be major mechanisms underlying opioid tolerance. Pain facilitatory mechanisms in the central nervous system are known to contribute to opioid-induced hyperalgesia. Recent research indicates that there may be overlap in the two conditions. This article reviews known and hypothesized pathophysiologic mechanisms surrounding these phenomena and the clinical implications for pain management nurses.  相似文献   
80.

Background  

Within cluster randomized trials no algorithms exist to generate a full enumeration of a block randomization, balancing for covariates across treatment arms. Furthermore, often for practical reasons multiple blocks are required to fully randomize a study, which may not have been well balanced within blocks.  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