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   10939篇
  免费   568篇
  国内免费   58篇
耳鼻咽喉   137篇
儿科学   276篇
妇产科学   219篇
基础医学   1629篇
口腔科学   348篇
临床医学   1075篇
内科学   2237篇
皮肤病学   176篇
神经病学   1223篇
特种医学   187篇
外科学   943篇
综合类   39篇
一般理论   5篇
预防医学   1168篇
眼科学   107篇
药学   942篇
中国医学   57篇
肿瘤学   797篇
  2024年   12篇
  2023年   94篇
  2022年   248篇
  2021年   424篇
  2020年   263篇
  2019年   359篇
  2018年   388篇
  2017年   278篇
  2016年   276篇
  2015年   331篇
  2014年   498篇
  2013年   603篇
  2012年   933篇
  2011年   984篇
  2010年   489篇
  2009年   443篇
  2008年   700篇
  2007年   752篇
  2006年   622篇
  2005年   614篇
  2004年   568篇
  2003年   481篇
  2002年   445篇
  2001年   52篇
  2000年   35篇
  1999年   55篇
  1998年   87篇
  1997年   75篇
  1996年   50篇
  1995年   49篇
  1994年   49篇
  1993年   38篇
  1992年   30篇
  1991年   27篇
  1990年   24篇
  1989年   15篇
  1988年   13篇
  1987年   11篇
  1986年   8篇
  1985年   15篇
  1984年   14篇
  1983年   11篇
  1982年   19篇
  1981年   14篇
  1980年   11篇
  1979年   10篇
  1978年   7篇
  1976年   8篇
  1973年   4篇
  1968年   5篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Lepidium meyenii ( Maca ) improved semen parameters in adult men   总被引:6,自引:0,他引:6  
Aim: The present study was designed to determine the effect of a 4-month oral treatment with tablets of Lepidium meyenii (Maca) on seminal analysis in nine adult normal men aged 24 - 44 years old. Methods: Nine men received tablets of Maca (1500 or 3000 mg/day) for 4 months. Seminal analysis was performed according to guidelines of the World Health Organization (WHO). Serum luteinizing hormone (LH), follicle stimulating hormone (FSH), prolactin (PRL), testosterone (T) and estradiol (E2) were measured before and after treatment. Results: Treatment with Maca resulted in increased seminal volume, sperm count per ejaculum, motile sperm count, and sperm motility. Serum hormone levels were not modified with Maca treamaent. Increase of sperm count was not related to dose of Maca. Conclusion: Maca improved sperm production and sperm motility by mechanisms not related to LH, FSH, PRL, T and E2.  相似文献   
82.
Mandibulofacial dysostosis (Treacher Collins Syndrome) is an autosomal dominant genetic disorder that probably derives from inhibition of the facial structures from the first and second branchial arches. The facial pattern of the syndrome is a convex facial profile with a prominent nose above a retruded chin. The eyes are deformed by antimongoloid slant of the palpebral fissures and facial bones are hypoplastic. The alterations are caused by mutation in gene 5q32-33.1, which encodes the nucleolar phosphoprotein treacle. Computed tomography images are able to demonstrate craniofacial bones, allowing the morphological analysis of these bones in individuals with complex deformities. The purpose of this paper is to present the results of a clinical and computed tomography investigation of two patients with Treacher Collins syndrome.  相似文献   
83.
Purpose For many years, the status of the axillary lymph nodes has been determined by an axillary lymphadenectomy. However, a sentinel lymph node biopsy has been shown to effectively replace the need for an axillary lymphadenectomy in order to determine the axillary staging. This study presents the preliminary results regarding the efficacy of fine-needle aspiration cytology (FNAC) to identify metastatic axillary lymph nodes in the pre-operative phase. Methods One hundred lymph nodes from 100 patients with histologically and cytologically confirmed breast cancer (cT1–2 cN0) underwent echo-guided FNAC. The diagnostic accuracy (sensitivity, specificity, positive predictive value [PPV], negative predictive value [NPV]) for the axillary metastases was evaluated based on the histological findings of either a sentinel lymph node biopsy or an axillary lymphadenectomy as a reference standard. Results It was possible to avoid a sentinel lymph node biopsy in 30% of the cases; the sensitivity was 68%, specificity 100%, PPV 100%, and NPV 65%. Echo-guided FNAC of the axillary lymph nodes should thus be included among the regular diagnostic procedures of presurgical staging. Conclusion This simple, inexpensive, and minimally invasive technique makes it possible to avoid the additional cost of a sentinel lymph node biopsy while also sparing the patient the stress of undergoing a second surgery.  相似文献   
84.
BACKGROUND: Evidence from animal studies indicate a crucial role for CD25(bright+) regulatory T cells in transplantation tolerance. METHODS: To assess whether peripheral CD25(bright+) T cells control immune responses in immunosuppressed kidney transplant patients, we analyzed the suppressive capacities of these cells using mixed lymphocytes reactions. RESULTS: Allogeneic stimulation of patients peripheral blood mononuclear cells was associated with IL-2 production and T-cell proliferation. Depletion of CD25(bright+) T cells resulted in a 35% (median) higher IL-2 production and a 38% higher proliferative response against third party cells, showing that functional regulatory CD25(bright+) T cells were present (p = 0.03 and 0.02 respectively). In eight out of 11 patients, we also demonstrated regulation activity against donor-activated T cells (p = 0.03). These data were confirmed in coculture experiments with isolated CD25(-/dim) T cells plus CD25(bright+) T cells. At a 1:2 ratio, the CD25(bright+) T cells suppressed the proliferation of CD25(-/dim) donor- and third party-stimulated responder T cells. CONCLUSIONS: CD25(bright+) T cells with immune regulatory activities against anti-donor-responsive T cells are readily detectable in renal allograft recipients during treatment with full dosage immunosuppression. Whether CD25(bright+) T cells indeed play a role in graft acceptance after organ transplantation in patients remains to be elucidated.  相似文献   
85.

Background

In breast conservation surgery (BCS) for breast cancer, the appropriate surgical margin is controversial. Margin index, a mathematical relationship between tumor size and closest margin, has been shown to be predictive of the probability of residual cancer after BCS for early stage breast cancer. We applied this tool to the same population of patients at our institution to evaluate its ability to predict residual disease after BCS.

Methods

We retrospectively reviewed a prospectively maintained database of women undergoing BCS between 1980 and 2010 at the University of Pennsylvania. A total of 246 women underwent re-excision because of close margins. Average margin index between groups with and without residual disease in the re-excision specimen was compared using the Student t-test. A receiver operating curve was created using logistic regression to assess the overall diagnostic ability of the margin index on the presence or absence of residual disease.

Results

Of patients who underwent re-excision, 29% of patients had residual disease. We analyzed several cutoff values for margin index, but none proved to be significant predictors of residual disease. Average margin index was significantly higher for patients without residual disease compared with patients with residual invasive cancer but not for patients with residual ductal carcinoma in situ.

Conclusions

In women undergoing BCS for early stage breast cancer at our institution, margin index was not predictive of the presence of residual cancer on re-excision. We hypothesize that the predictive ability of a margin index is likely limited by several factors including the presence of ductal carcinoma in situ and the location and extent of the close margin.  相似文献   
86.

Introduction

Although most studies report high frequencies of consent to HIV tests, critics argue that clients are subject to pressure, that acceptors later indicate they could not have refused, and that provider-initiated HIV testing raises serious ethical issues. We examine the meaning of consent and why clients think they could not have refused.

Methods

Clients in Burkina Faso, Kenya, Malawi and Uganda were asked about consenting to HIV tests, whether they thought they could have refused and why. Textual responses were analyzed using qualitative and statistical methods.

Results

Among 926 respondents, 77% reported they could not have said no, but in fact, 60% actively consented to test, 24% had no objection and only 7% tested without consent. There were few significant associations between categories of consent and their covariates.

Conclusions

Retrospectively asking clients if they could have refused to test for HIV overestimates coercion. Triangulating qualitative and quantitative data suggests a considerable degree of agency.  相似文献   
87.
This case report assessed quality of life, activities of daily living, motor symptoms, functional ability, neuromuscular parameters and mRNA expression of selected genes related to muscle protein synthesis and degradation in a patient with Multiple System Atrophy (MSA). The patient underwent resistance training with instability devices (i.e., bosu, dyna disk, balance disk, Swiss ball) for six months twice a week. After the six months training, the patient’s left and right quadriceps muscle cross-sectional area and leg press one-repetition maximum increased 6.4%, 6.8%, and 40%, respectively; the patient’s timed up and go, sit to stand, dynamic balance, and activities of daily living improved 33.3%, 28.6%, 42.3%, and 40.1%, respectively; the patient’s severity of motor symptoms and risk of falls decreased 32% and 128.1%, respectively. Most of the subscales of quality of life demonstrated improvements as well, varying from 13.0% to 100.0%. mRNA expression of mechanogrowth factor and mammalian target of rapamycin increased 12.7-fold and 1.5-fold, respectively. This case report describes likely the first nonpharmacological therapeutic tool that might be able to decrease the severity of motor symptoms and risk of falls, and to improve functional ability, neuromuscular parameters, and quality of the life in a patient with MSA.

Key points

  • Six months of resistance training with instability alleviate the MSA-related effects and improve the quality of life in a patient with MSA.
  • High complexity exercise intervention (i.e., resistance training with instability) may be very beneficial to individuals with impaired motor control and function as MSA patients.
  • Caution should be exercised when interpreting our findings as they cannot be generalized to the entire MSA population and they do not allow establishing causal conclusions on the effects of this mode of exercise on MSA.
Key words: Exercise training, risk of falls, motor symptoms, cross-sectional area  相似文献   
88.
The purpose of this study was to sequentially monitor anti‐HLA antibodies and correlate the results with antibody‐mediated rejection (AMR), graft survival (GS), and graft function (GF). We collected sera from 111 kidney transplant recipients on transplant days 0, 7, 14, 30, 60, 90, 180, and 360 and analyzed PRA levels by ELISA. DSAs were analyzed by single‐antigen beads in rejecting kidneys. At pre‐transplant, 79.3% of the patients were non‐sensitized (PRA = 0%) and 20.7% were sensitized (PRA > 1%). After transplant, patients were grouped by PRA profile: no anti‐HLA antibodies pre‐ or post‐transplant (group HLApre?/post?; n = 80); de novo anti‐HLA antibodies post‐transplant (group HLApre?/post+; n = 8); sensitized pre‐transplant/increased PRA post‐transplant (group HLApre+/post↑; n = 9); and sensitized pre‐transplant/decreased PRA post‐transplant (group HLApre+/post↓; n = 14). De novo anti‐HLA antibodies were detected at 7–180 d. In sensitized patients, PRA levels changed within the first 30 d post‐transplant. Incidence of AMR was higher in HLApre?/post+ and HLApre+/post↑ than in HLApre?/post?, and HLApre+/post↓ (p < 0.001) groups. One‐yr death‐censored GS was 36% in group HLApre+/post↑, compared with 98%, 88% and 100% in groups HLApre?/post?, HLApre?/post+, and HLApre+/post↓, respectively (p < 0.001). Excluding first‐year graft losses, GF and GS were similar among the groups. In conclusion, post‐transplant antibody monitoring can identify recipients at higher risk of AMR.  相似文献   
89.
The ability of the anterior cruciate ligament (ACL) to heal after injury declines within the first 2 weeks after ACL rupture. To begin to explore the mechanism behind this finding, we quantified the expression of genes for collagen I and III, decorin, tenascin‐C, and alpha smooth muscle actin, as well as matrix metalloproteinase (MMP)‐1 and ‐13 gene expression within multiple tissues of the knee joint after ACL injury in a large animal model over a 2‐week postinjury period. Gene expression of collagen I and III, decorin, and MMP‐1 was highest in the synovium, whereas the highest MMP‐13 gene expression levels were found in the ACL. The gene expression for collagen and decorin increased over the 2 weeks to levels approaching that in the ligament and synovium; however, no significant increase in either of the MMPs was found in the provisional scaffold. This suggests that although the ACL and synovium up‐regulate both anabolic and catabolic factors, the provisional scaffold is primarily anabolic in function. The relative lack of provisional scaffold formation within the joint environment may thus be one of the key reasons for ACL degradation after injury.  相似文献   
90.

Purpose

Scaphoid fractures are commonly fixed with headless cannulated screws positioned centrally in the scaphoid. Judgement of central placement of the screw may be difficult. We generated a central zone using computer analysis of 3D reconstructions of computed tomography (CT) images. As long as the screw axis is completely contained within this central zone, the screw would be considered as centrally placed.

Methods

Thirty cases of 3D CT reconstructions of normal scaphoids in a computerised operation planning and simulation system (Vxwork software) were obtained. The central zone was established after some distance shrinkage of the original scaphoid surface reconstruction model using the function “erode” in the software. The shape of the central zone was evaluated, and the width of the central zone in the proximal pole, waist portion and distal pole was measured. We also established the long axis of the scaphoid to see whether it stays in the central zone.

Results

All central zones could be divided into distal, waist and proximal portions according to the corresponding irregular shape of the scaphoid. As the geometry of the central zone was so irregular and its width very narrow, it was possible to completely contain the screw axis either in the proximal portion alone, waist alone or distal central zone alone.

Conclusions

Establishing the central zone of scaphoid 3D CT images provided a baseline for discussion of central placement of a scaphoid screw. The geometry of the scaphoid central zone determined that the screw could hardly be inserted through entire scaphoid central area during surgery.  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