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   7272篇
  免费   577篇
  国内免费   33篇
耳鼻咽喉   69篇
儿科学   107篇
妇产科学   173篇
基础医学   940篇
口腔科学   222篇
临床医学   786篇
内科学   1583篇
皮肤病学   145篇
神经病学   637篇
特种医学   673篇
外科学   1359篇
综合类   35篇
预防医学   226篇
眼科学   153篇
药学   318篇
中国医学   2篇
肿瘤学   454篇
  2023年   92篇
  2022年   157篇
  2021年   332篇
  2020年   197篇
  2019年   292篇
  2018年   321篇
  2017年   234篇
  2016年   261篇
  2015年   311篇
  2014年   406篇
  2013年   403篇
  2012年   611篇
  2011年   608篇
  2010年   364篇
  2009年   356篇
  2008年   428篇
  2007年   414篇
  2006年   327篇
  2005年   296篇
  2004年   240篇
  2003年   234篇
  2002年   165篇
  2001年   84篇
  2000年   62篇
  1999年   78篇
  1998年   27篇
  1997年   36篇
  1996年   23篇
  1995年   11篇
  1994年   11篇
  1993年   12篇
  1992年   24篇
  1991年   24篇
  1990年   15篇
  1989年   17篇
  1988年   24篇
  1987年   23篇
  1986年   24篇
  1985年   22篇
  1984年   13篇
  1983年   12篇
  1982年   10篇
  1981年   12篇
  1979年   24篇
  1975年   12篇
  1932年   13篇
  1931年   8篇
  1929年   7篇
  1924年   12篇
  1922年   8篇
排序方式: 共有7882条查询结果,搜索用时 46 毫秒
51.
BackgroundAddition of vitamin E to polyethylene is theorized to reduce the potential for oxidative wear in acetabular components. This paper presents a multicenter prospective cohort study that reports on outcomes from use of a Vitamin E–infused highly cross-linked polyethylene acetabular cup.MethodsPatients were recruited across nine medical institutions. Clinical outcome measures recorded were the Harris Hip Score, visual analogue score for pain and satisfaction. Evidence of implant loosening or osteolysis was collected radiologically. Cup survival and reasons for revision in relevant cases were also recorded. Data collection was undertaken preoperatively, at 6-12 weeks, 6 months, 1 year, 2 years, and 5 years. A total of 675 patients were recruited, with 450 cases available at final review. Data regarding cup survival was available to 8 years and 9 months postoperatively.ResultsImprovements in both the Harris Hip Score and visual analogue score for pain and satisfaction were recorded at all time points, with these being maintained through the length of follow-up. In total, 89% of cups were implanted within the Lewinnek safe zone. A lucent line was identified in one case, with no evidence of acetabular osteolysis observed throughout the follow-up period. Cup survival was 98.9% at 8 years and 9 months. No revisions for aseptic loosening were observed.ConclusionsThe use of a vitamin E–infused polyethylene acetabular cup demonstrates reassuring patient-reported outcomes, radiological measures, and cup survival at medium to long-term follow-up.  相似文献   
52.
53.
It is unknown if solid organ transplant recipients are at higher risk for severe COVID-19. The management of a lung transplantation (LTx) program and the therapeutic strategies to adapt the immunosuppressive regimen and antiviral measures is a major issue in the COVID-19 era, but little is known about worldwide practice. We sent out to 180 LTx centers worldwide in June 2020 a survey with 63 questions, both regarding the management of a LTx program in the COVID-19 era and the therapeutic strategies to treat COVID-19 LTx recipients. We received a total of 78 responses from 15 countries. Among participants, 81% declared a reduction of the activity and 47% restricted LTx for urgent cases only. Sixteen centers observed deaths on waiting listed patients and eight centers performed LTx for COVID-19 disease. In 62% of the centers, COVID-19 was diagnosed in LTx recipients, most of them not severe cases. The most common immunosuppressive management included a decreased dose or pausing of the cell cycle inhibitors. Remdesivir, hydroxychloroquine, and azithromycin were the most proposed antiviral strategies. Most of the centers have been affected by the COVID-19 pandemic and proposed an active therapeutic strategy to treat LTx recipients with COVID-19.  相似文献   
54.
To date, little is known about the duration and effectiveness of immunity as well as possible adverse late effects after an infection with SARS-CoV-2. Thus it is unclear, when and if liver transplantation can be safely offered to patients who suffered from COVID-19. Here, we report on a successful liver transplantation shortly after convalescence from COVID-19 with subsequent partial seroreversion as well as recurrence and prolonged shedding of viral RNA.  相似文献   
55.
Scavenger receptor class B type I (SR-BI), a CD36 family member, plays a key role in high-density lipoprotein (HDL) metabolism, reverse cholesterol transport, and whole body cholesterol homeostasis, and is shown to be involved in the development of atherosclerosis in mice. In this report, we describe the effects of the adenoviral overexpression of human SR-BI (hSR-BI) in New Zealand White (NZW) rabbits, a wild-type animal model that expresses cholesteryl ester transfer protein (CETP) in plasma, displays a manlike lipoprotein profile, and is susceptible to atherosclerosis. A total of 1×1012 adenoviral particles containing either hSR-BI or lacZ complementary deoxyribonucleic acid (control) were infused into the ear vein of NZW rabbits. Transgene expression was ascertained by TaqMan Real Time polymerase chain reaction measurements. Rabbits infected with Ad/hSR-BI (adenoviral plasmids containing hSR-BI) showed a faster clearance of administered [3H]HDL cholesterol and significantly decreased apolipoprotein (apo) A-I levels when compared to control rabbits, respectively. Interestingly, we found markedly increased levels of low-density lipoprotein (LDL) cholesterol exclusively in SR-BI-overexpressing rabbits. These changes were not accompanied by alterations in LDL receptor expression but by increased levels of CE transfer in these animals. By lowering HDL cholesterol and increasing plasma apoB-containing lipoprotein levels, the overexpression of SR-BI leads to a lipoprotein pattern, which is believed to enhance the development of atherosclerosis. The role of SR-BI in lipoprotein metabolism and atherogenesis in rabbits—a CETP-expressing animal model displaying a manlike lipoprotein profile—may therefore be different from the one found in rodents.  相似文献   
56.
Imaging with technetium-99m sestamibi offers a non-invasive approach to detect the presence of functional P-glycoprotein (Pgp), one of the major causes of multidrug resistance, in human malignancies. A clinical role for Pgp has been suggested in the subpopulation of primary neuroblastoma without amplification of the proto-oncogene MYCN. We wanted to evaluate the usefulness of 99mTc-sestamibi scintigraphy in the screening of neural crest tumours for the presence of Pgp. In ten children suffering from MYCN-negative neuroblastoma, ganglioneuroblastoma or ganglioneuroma, 99mTc-sestamibi imaging was performed at initial diagnosis. All patients underwent planar imaging 20-30 min and 3.5-4 h after intravenous injection of 740 MBq/1.73 m2 99mTc-sestamibi. Tumour to normal tissue ratios, as well as washout rates, were determined and compared with in vitro flow cytometric analysis of Pgp expression and function. Pgp expression was analysed flow cytometrically with the monoclonal antibodies 4E3 and MRK16, and Pgp function was evaluated by means of rhodamine 123 uptake and efflux either in the absence or in the presence of the Pgp inhibitor verapamil. In nine of ten patients, we found that the intratumoral 99mTc-sestamibi activity was comparable to the background activity, which might be suggestive of Pgp presence. This was confirmed flow cytometrically in all but one patient. 99mTc-sestamibi enhancement was seen in the primary tumour and the bone marrow metastases of one of the ten patients, and this result was concordant with a negative Pgp status. The findings presented suggest that 99mTc-sestamibi imaging results might correlate with the presence of functional Pgp in neural crest tumours without MYCN amplification.  相似文献   
57.
The improvement of quality of life is one of the major goals in the treatment of patients after renal transplantation. While immunosuppressive therapy is present in almost all of these patients, little is known about the effects of newer immunosuppressive agents. We therefore investigated the impact of tacrolimus on life quality. From November 1997 to January 1998, a questionnaire was handed out which focussed on physical and mental problems as well as sexual capacity and the attitudes towards graft, donor and transplant related side effects. 50 kidney graft recipients treated with tacrolimus were matched to 50 patients with a cyclosporine-based immunosuppression (= controls). Values are given as mean +/- standard deviation. Tacrolimus treated patients had a mean creatinine of 1.8 +/- 0.8 mg/dl, as compared to 1.6 +/- 0.7 mg/dl in controls. The overall status of health was assessed to be good in 82% of the tacrolimus group (controls: 80%). 38% were working full-time (controls: 20%). Only 14% of patients described their physical condition as poor (16% in controls). Sexual function was good in 66% (controls: 74%) and poor in 10% (controls: 12%). Mental function was assessed to be good in 92% (controls: 82%). The majority of patients felt comfortable with their physical, sexual and mental capabilities. This was independent from the immunosuppressive regimen.  相似文献   
58.
BACKGROUND: Renal hemodynamics and immune responses differ between males and females. Thus, sex hormones and genetically determined gender differences may determine the process of chronic rejection to some extent. METHODS: Female (F) or male (M) F344 kidneys were orthotopically transplanted into ovariectomized female Lewis recipients and were treated for 16 weeks with either estradiol, testosterone, or vehicle. RESULTS: Testosterone treatment resulted in increased urinary protein excretion independently of the donor gender, as well as extended glomerular sclerosis, interstitial fibrosis, and severe vascular lesions. Additionally, mononuclear cell infiltration was most pronounced in these animals, in parallel to an increased expression of intercellular adhesion molecule-1 (ICAM-1), fibronectin, laminin, and transforming growth factor-beta (TGF-beta) in the grafts. Estradiol treatment resulted in an improved graft function, reduced glomerular sclerosis, and a diminished cellular infiltration, in parallel to a reduced ICAM-1, fibronectin, laminin, and TGF-beta expression. In animals treated with vehicle, the gender of the donor influenced the outcome. Grafts of male origin had good graft function and histology, whereas grafts from female donors developed severe proteinuria and glomerular, interstitial, and vascular damage. CONCLUSIONS: These results suggest that a protective effect of estradiol on the progression of chronic rejection exists that is independent of donor gender. Additionally, a male kidney may benefit from the absence of testosterone, whereas the function of a female kidney deteriorates in the absence of estradiol.  相似文献   
59.
The aetiology of malignant melanoma is not wholly explained by exposure to sunshine. The present of arsenic in the soil has been suggested as a possible causative factor. Geographical clustering of malignant melanoma cases in the South Western Region is demonstrated for males and this clustering is associated with the distribution of arsenic in the soil. No evidence of geographical clustering is however found for females. This suggests possible sex-specific differences in the aetiology of malignant melanoma and indicates the need for further study of the association with arsenic.

Full text

Full text is available as a scanned copy of the original print version. Get a printable copy (PDF file) of the complete article (2.5M), or click on a page image below to browse page by page.
 165166167168169  相似文献   
60.
The concept of major depression   总被引:1,自引:0,他引:1  
Six operational definitions of the concept of major depression were submitted to empirical evaluation in 600 psychiatric inpatients. Special attention was given to the comparison of major depression in DSM-III-R and ICD-10. The data base created by a polydiagnostic interview revealed relevant classificatory differences between the six definitions under study. Sources of different diagnostic base rates were: inclusion or omission of anhedonia as an obligatory mood criterion; minimal number of syndrome criteria required for the syndrome diagnosis; different width and reference points of time criteria; exclusion rules for co-existing schizophrenic symptoms and for previous nonaffective and manic episodes. The empirically evaluated overlap between pairs of diagnostic definitions was less than excellent in most of the diagnostic definitions under study; only the DSM-III and DSM-III-R definitions agreed with each other to a highly comparable degree. The relatively good agreement of the 1989 draft definition of ICD-10 for major depression ("mild depression") with the other five operational definitions (kappa = 0.69) led us to expect that this definition should receive sufficient international acceptance.  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