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   3319篇
  免费   277篇
  国内免费   30篇
耳鼻咽喉   6篇
儿科学   176篇
妇产科学   121篇
基础医学   518篇
口腔科学   119篇
临床医学   292篇
内科学   525篇
皮肤病学   65篇
神经病学   247篇
特种医学   228篇
外科学   563篇
综合类   49篇
一般理论   1篇
预防医学   201篇
眼科学   55篇
药学   101篇
中国医学   2篇
肿瘤学   357篇
  2023年   22篇
  2022年   16篇
  2021年   29篇
  2020年   33篇
  2019年   30篇
  2018年   72篇
  2017年   77篇
  2016年   68篇
  2015年   103篇
  2014年   136篇
  2013年   175篇
  2012年   144篇
  2011年   123篇
  2010年   140篇
  2009年   144篇
  2008年   108篇
  2007年   133篇
  2006年   147篇
  2005年   102篇
  2004年   101篇
  2003年   91篇
  2002年   87篇
  2001年   91篇
  2000年   98篇
  1999年   105篇
  1998年   130篇
  1997年   122篇
  1996年   122篇
  1995年   81篇
  1994年   91篇
  1993年   60篇
  1992年   51篇
  1991年   54篇
  1990年   44篇
  1989年   57篇
  1988年   54篇
  1987年   50篇
  1986年   38篇
  1985年   41篇
  1984年   29篇
  1983年   21篇
  1982年   28篇
  1981年   23篇
  1980年   21篇
  1979年   16篇
  1978年   21篇
  1977年   14篇
  1976年   16篇
  1975年   16篇
  1925年   4篇
排序方式: 共有3626条查询结果,搜索用时 11 毫秒
81.
Isolated mitochondrial complex IV (cytochrome c oxidase) deficiency is an important cause of mitochondrial disease in children and adults. It is genetically heterogeneous, given that both mtDNA-encoded and nuclear-encoded gene products contribute to structural components and assembly factors. Pathogenic variants within these proteins are associated with clinical variability ranging from isolated organ involvement to multisystem disease presentations. Defects in more than 10 complex IV assembly factors have been described including a recent Lebanese founder mutation in PET100 in patients presenting with Leigh syndrome. We report the clinical and molecular investigation of a patient with a fatal, neonatal-onset isolated complex IV deficiency associated with multiorgan involvement born to consanguineous, first-cousin British Asian parents. Exome sequencing revealed a homozygous truncating variant (c.142C>T, p.(Gln48*)) in the PET100 gene that results in a complete loss of enzyme activity and assembly of the holocomplex. Our report confirms PET100 mutation as an important cause of isolated complex IV deficiency outside of the Lebanese population, extending the phenotypic spectrum associated with abnormalities within this gene.  相似文献   
82.
Monocytoid B-cell lymphoma (MBCL) is a newly recognized B-cell neoplasm of uncertain histogenesis. The cytologic features of the neoplastic monocytoid B lymphocytes are virtually identical to those of hairy cell leukemia (HCL). As with HCL, progression of MBCL to a higher histologic grade is very unusual. However, whereas circulating leukemic cells are a characteristic feature of HCL, peripheral blood involvement has not been reported in MBCL. We recently studied a patient with MBCL of the spleen and axillary lymph nodes who developed peripheral blood involvement by MBCL cells. Unlike the cells of HCL, the circulating MBCL cells exhibited strong acid phosphatase activity that was tartrate sensitive. The leukemic cells had the antigenic phenotype IgM lambda, CD20+, CD11c+, CD5-, CD25(TAC)-, and PCA-1-. Immunogenetic studies of both lymph node and peripheral blood cells revealed identical immunoglobulin heavy-chain gene rearrangements. When compared with a series of HCL, the immunophenotype was similar except for the absence of PCA-1 and TAC. Progression of the MBCL to a large cell lymphoma, also expressing IgM lambda, was documented in an abdominal lymph node of this patient. Therefore, although rare, peripheral blood involvement by lymphoma cells may occur during the course of MBCL and should be distinguished from HCL with cytochemical and immunophenotypic studies. In addition, comparison of the clinical, pathologic, and immunologic features of MBCL with those of other low-grade B-cell neoplasms suggests that a close lineage relationship exists between MBCL and HCL.  相似文献   
83.
Bhalla  K; Holladay  C; Arlin  Z; Grant  S; Ibrado  AM; Jasiok  M 《Blood》1991,78(10):2674-2679
Hematopoietic growth factors (HGFs) interleukin-3 (IL-3) and granulocyte-macrophage colony-stimulating factor (GM-CSF) individually have been shown to increase the percentage of acute myeloid leukemia (AML) blasts in S phase and enhance the cytotoxic effects of Ara-C against these blasts in culture. We compared in vitro the effects of a combined treatment with GM-CSF (10 ng/mL) plus IL-3 (10 ng/mL) on the metabolism and cytotoxicity of Ara-C in normal bone marrow mononuclear cells (NBMMC) and AML blasts. NBMMC from six healthy volunteers and AML blasts from 10 patients were incubated for 20 hours with or without IL- 3 plus GM-CSF, followed by a concurrent treatment with Ara-C for 4 additional hours. Exposure to the HGFs and Ara-C produced significantly higher intracellular Ara-CTP levels as well as higher Ara-CTP/dCTP pool ratios in AML blasts as compared with NBMMC. Treatment with HGFs resulted in [3H] Ara-C DNA incorporation that was significantly higher in AML blasts versus NBMMC. This selective improvement of Ara-C metabolism in AML blasts was associated with an enhanced Ara-C-mediated leukemia colony-forming unit (CFU) growth inhibition. In contrast, exposure to HGFs resulted in an improved colony growth of normal CFU granulocyte-monocyte and CFU-granulocyte, erythroid, monocyte, megakaryocyte. These in vitro studies indicate that a combined treatment with IL-3 plus GM-CSF may improve the selectivity of Ara-C against AML blasts.  相似文献   
84.

Purpose

Sharing of medical data is crucial for the proper treatment of patients as it could reduce the risk of duplicated medical tests and speed up the care process if all documents are readily available. Despite great technical progress, sharing patient data while maintaining full control over the process in an intersectoral (in Germany, this describes the different actors in the healthcare system consisting of clinic, ambulatory care, etc.) setting remains a particular challenge. This paper focuses on the successful implementation of a privacy compliant, standards-based image-management component of a personal electronic health record.

Methods

Over a 5-year period, a sharing system based on readily available IHE profiles constructed around XDS has been built. It was necessary to create interfaces for the existing hospital sub-systems to become part of the network. Specifically, the imaging workflow had to be adapted to allow for fast and easy access to DICOM images utilizing a flexible web-based image viewer. In addition to the standard XDS workflow, an Imaging Cache was established which combines the Imaging Document Source and Consumer to guarantee fast and streaming-based access to all images in the network observing the high security standards of the hospital network.

Results

The authors of this paper have proven that it is possible to build a fast and reliable sharing system based on IHE profiles using most of the transactions of XDS-I with some adaptions to the clinical workflow. Primary hospital systems were enabled by building adapters to overcome lack of IHE compatibility. The established system embraces the existing security mechanisms in hospital networks while connecting patients and referring physicians from outside in a secure and convenient manner.

Conclusions

A state-of-the-art sharing system that is used in a productive clinical environment has been established and is ready to grow with more partners. The system is the basis for an elaborated interdisciplinary collaboration where data, and in particular images, can now be shared between medical professionals.
  相似文献   
85.
To address shortcomings of purely reaction-time based attention bias modification (ABM) paradigms, a novel eye-tracking based ABM training (ET-ABM) was developed. This training targets the late disengagement from negative stimuli and the lack of attention for positive information, which are characteristics of depression. In the present study, 75 dysphoric students (BDI?≥?9) were randomly assigned to either this positive training (PT), or a sham-training (ST) that did not train any valence-specific gaze pattern (positive and negative pictures had to be disengaged from and attended to equally often). Results showed that the PT induced a positive attentional bias (longer fixations of positive than negative pictures). Although the ST group showed an increase in positive attentional bias as well, this increase was not as strong as in the PT group. Compared to the ST, the PT specifically induced faster disengagement from negative pictures. No differential training effects were found on stress responses or state rumination. These results show that the ET-ABM successfully modifies attentional processes, specifically late disengagement from negative stimuli, in dysphoric students, and hence might be a promising alternative to existing ABM paradigms.  相似文献   
86.

Objective

To evaluate the effect of pulmonary rehabilitation (PR) on exercise performance and quality of life in patients with chronic obstructive pulmonary disease (COPD) with different degrees of static lung hyperinflation (LH).

Design

Retrospective cohort study.

Setting

PR network.

Participants

A cohort of 1981 patients with COPD (55% men; age: 66.8±9.3y; forced expiratory volume in the first second%: 50.7±19.5; residual volume [RV]%: 163.0±49.7).

Intervention

An interdisciplinary PR program for patients with COPD consisting of 40 sessions.

Main Outcome Measures

Participants were stratified into 5 quintiles according to baseline RV and were evaluated on the basis of pre- and post-PR 6-minute walk distance (6MWD), constant work rate test (CWRT), and Saint George’s Respiratory Questionnaire (SGRQ), among other clinical parameters.

Results

With increasing RV quintile, patients were younger, more frequently women, had lower forced expiratory volume in the first second%, lower body mass index and fat-free mass index, shorter 6MWD, shorter CWRT, and worse SGRQ scores (P<.01). All RV strata improved after PR in all 3 outcomes (P<.001). Nevertheless, higher, compared to lower RV categories, had lower ΔCWRT (P<.01) but similar Δ6MWD (P=.948) and ΔSGRQ (P=.086) after PR.

Conclusions

LH in COPD is related to younger age, female sex, lower body weight, worse exercise capacity and health status, but did not prevent patients from benefitting from PR. LH, however, influences walking and cycling response after PR differently.  相似文献   
87.
88.
Hyperresponsiveness of the hypothalamo-pituitary-adrenal (HPA) axis in multiple sclerosis (MS), an autoimmune inflammatory disease of the central nervous system, is presumably due to diminished corticosteroid receptor function. It probably influences the immune response, but its clinical significance is not clear. Similar HPA dysregulation occurs in depression and is reversible with successful antidepressant treatment. We conducted a double blind, placebo-controlled trial to evaluate the neuroendocrine effect of cotreatment with the antidepressant moclobemide as an adjunct to oral corticosteroids in MS. Twenty-one patients with definite relapsing-remitting MS (11 females, aged 33.9 +/- 2.0 yr; Expanded Disability Status Scale score of neurological impairment, 2.0--6.5) in acute relapse were treated with placebo (n = 13) or 300 mg moclobemide (reversible monoamine oxidase A inhibitor; n = 8) for 75 days. All received oral fluocortolone from day 7 on, and the dose was tapered until day 29. Effects were evaluated using the combined dexamethasone-CRH test and clinically on days 1, 30, and 75. At baseline, the HPA axis was mildly activated, comparably for treatment groups [area under the curve for cortisol (AUC-Cort), 213.8 +/- 76.8 arbitrary units in the moclobemide group vs. 225.8 +/- 65.1 in the steroid alone group; mean +/- SEM]. In a group of healthy controls with comparable demographic characteristics, the AUC-Cort was 107.4 +/- 14.1. Moclobemide cotreatment resulted in normalization of the HPA axis response, whereas the HPA system hyperresponse was maintained with steroids alone (AUC-Cort on day 30, 85.9 +/- 22.8 vs.177.1 +/- 68.5; on day 75, 111.0 +/- 46.0 vs. 199.2 +/- 64.6). The change in Expanded Disability Status Scale was comparable for both groups. Although corticosteroids alone had no effect on the HPA response using the dexamethasone-CRH test, treatment with moclobemide combined with corticosteroids favors normalization of the HPA response in relapsing-remitting MS.  相似文献   
89.
Implantable left ventricular assist systems (LVAS) consist of implantable pumps with small control consoles and power sources that can be worn externally. These systems provide far greater patient mobility and independence than external pumps with bulky control consoles. Patients with implantable LVAS can be discharged from hospital and are able to return to work and resume active sports. Most patients have received these systems as a bridge to heart transplantation. Clinical status and quality of life improve dramatically after device implantation and survival on support (60-70% after approx. 100 days of support) is acceptable compared with transplant candidates on medical therapy. Patient selection and adverse events, primarily bleeding, thromboembolism and infection, are important issues with LVAS. In the future, long-term support and bridging to myocardial recovery may become important indications for LVAS.  相似文献   
90.
OBJECTIVE To investigate the basal levels of gonadotrophins and sex steroids, with special reference to the effects of obesity and body fat distribution, In premenopausal women, both those with polycystic ovary syndrome (PCOS) and those with normal ovaries and regular menstrual cycles. DESIGN Cross-sectional study. The separate effects of obesity (and body fat distribution and fasting Insulin levels) and PCOS on endocrine variables were evaluated by means of analysis of covariance. PATIENTS Sixty-seven women with anovulatory menstrual cycles and polycystic ovaries according to ultrasonography and 59 women with normal ovaries and regular cycles, both groups covering a wide range of body mass index (BMI, PCOS, 17·6-37·4, mean 25·7 kg/m2; controls, 18·8-40·9, mean 25·1 kg/m2). MEASUREMENTS Serum levels of gonadotrophins, sex steroid hormones, prolactin and GH obtained in the early follicular phase in the controls, fasting insulin levels, anthropometric measures (BMI, skinfolds, waist hip ratio). RESULTS Mean serum concentrations of LH, andro-stenedione, testosterone, the free androgen index (FAI; all P < 0·0001) and DHEAS (P < 0·01) were higher, and serum FSH (P < 0·01) and serum SHBG levels lower (P < 0·0001), in the PCOS group than in the controls. Women with PCOS had a more pronounced upper body fat distribution and higher fasting insulin levels than the controls. Independent of PCOS, BMI was positlvely associated with serum levels of FSH (P < 0·001) and negatively with levels of LH (P < 0·05), LH/FSH ratio (P < 0·0001), SHBG (P < 0·0001) and androstenedione (P < 0·01), whereas for levels of testosterone, FAI and DHEAS the impact of obesity differed significantly between the groups. Thus, in the PCOS group, testosterone levels (P < 0·05) and the FAI (P < 0·001) were positively associated with BMI, whereas they were constant throughout the entire range of BMI in the controls. DHEAS levels were positively associated with BMI in the PCOS group (P < 0·05) and negatively in the controls (P < 0·01). Measures of upper body fat were related to testosterone and FAI levels, independent of BMI. CONCLUSIONS Lower FSH levels were found in women with PCOS than during the early follicular phase of normally ovulating women, suggesting a role in anovulation in PCOS. Obesity itself exerted effects on endocrine variables, with the net result of a reduced LHIFSH ratio and lower serum levels of androstenedione and SHBG in both groups; obesity was associated with increased levels of DHEAS, testosterone and FAI exclusively in the women with PCOS. The results underline the endocrine impact of obesity and body fat distribution and the necessity of applying reference values of BMI matched subjects when establishing the endocrine profile of women with PCOS.  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