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   3796篇
  免费   205篇
  国内免费   9篇
耳鼻咽喉   60篇
儿科学   123篇
妇产科学   81篇
基础医学   504篇
口腔科学   73篇
临床医学   350篇
内科学   758篇
皮肤病学   50篇
神经病学   509篇
特种医学   212篇
外科学   457篇
综合类   17篇
一般理论   3篇
预防医学   236篇
眼科学   40篇
药学   320篇
中国医学   5篇
肿瘤学   212篇
  2023年   20篇
  2022年   34篇
  2021年   86篇
  2020年   56篇
  2019年   93篇
  2018年   82篇
  2017年   64篇
  2016年   92篇
  2015年   112篇
  2014年   130篇
  2013年   159篇
  2012年   272篇
  2011年   305篇
  2010年   201篇
  2009年   164篇
  2008年   275篇
  2007年   296篇
  2006年   282篇
  2005年   288篇
  2004年   216篇
  2003年   195篇
  2002年   218篇
  2001年   33篇
  2000年   29篇
  1999年   41篇
  1998年   36篇
  1997年   36篇
  1996年   26篇
  1995年   21篇
  1994年   23篇
  1993年   16篇
  1992年   9篇
  1991年   7篇
  1990年   6篇
  1989年   8篇
  1988年   3篇
  1987年   3篇
  1985年   4篇
  1984年   6篇
  1983年   3篇
  1982年   7篇
  1981年   6篇
  1979年   3篇
  1974年   3篇
  1970年   3篇
  1967年   2篇
  1961年   3篇
  1960年   3篇
  1914年   2篇
  1908年   3篇
排序方式: 共有4010条查询结果,搜索用时 15 毫秒
101.
102.
Iso‐α‐acids (IAAs) can be used as markers for the consumption of beer. Postmortem specimens from a range of coronial cases were analyzed for IAAs in order to determine the prevalence of beer consumption and any correlation to blood alcohol concentrations (BAC). A total of 130 cases were included in this study including those where beer was mentioned in the case circumstances, cases where beer was not mentioned specifically but alcohol was detected, and cases where neither beer was mentioned nor a positive BAC was present. Available blood, serum, vitreous humour and urine specimens were analyzed. Of the 50 cases where beer was mentioned, 86% had one or more IAAs detected. In cases that only had a positive BAC (n = 60), 57% of these cases also showed the presence of these beer markers. IAAs were detected in specimens obtained from traumatized, burnt, and decomposed cases with a mention of beer consumption or where BAC was positive in blood. No IAAs were detected in cases where BAC was negative. There was little or no correlation between blood IAA concentrations and BAC. This study demonstrates the possible detection of IAAs as a marker for beer consumption. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   
103.
104.
PURPOSE: This article describes the potential of dynamic contrast- enhanced magnetic resonance tomography (DCE-MRT) for the visualization and quantification of blood flow of lower leg muscles at rest and after individually adjusted muscular exercise. PATIENTS AND METHODS: Five cases were chosen to exemplify the qualitative and semi-quantitative blood flow evaluation in the lower leg muscles. The crural muscle state was determined with an isometric maximal strength measurement from a female patient with peripheral arterial occlusive disease (pAVK), a male patient with coronary heart disease (KHK) without clinical signs of a pAVK, a volunteer with sufficient physical activity in accordance with the Freiburg Questionnaire of Physical Activity and two professional athletes. After calibration of the plantarflexion ergometer MR-PEDALO (Figures 2a and 2b) for the execution of auxotonic muscle work a 1- minute alternating foot extension and flexion exercise on MRPEDALO was performed in the MR machine. Instead of the lower leg splint shown in Figures 2a and 2b the MR coil fits exactly in MR-PEDALO used for DCE-MRT. Mechanical work performed during the 1-minute exercise ranged from 52 watt seconds (Ws) to 244 Ws (0.65 W to 4.07 W), indicating similar interindividual work loads in relation to the individual maximum isometric strength. DCE-MRT was performed at rest and immediately after auxotonic exercise test (T1w 2DFLASH- GE sequence with TR/TE/alpha: 100 ms/6 ms/70 degrees; field of view: 400; matrix: 81 x 256; slice thickness: 10 mm; acquisitions: 73 at 8.3 s each; total examination time: 9.24 min; bolus application of Magnevist, Schering, 0.02 ml/kg kg, 20 ml bolus NaCl, flow 2 ml/s, 22G cannula in a cubital vein). Signal intensity (SI) curves were analyzed with DynaVision (MeVis gGmbH, Bremen, Germany). RESULTS: Measuring peripheral blood flow needs appropriate muscular stress tests. The SI-curves of the region of interest (ROI) representing the peroneus, tibialis anterior and gastrocnemius muscle run almost parallel at rest. Workloads between 52 Ws and 244 Ws (0.65 W and 4.07 W), similar in relation to the individual maximum isometric strength, induce distinctive changes of the upslope, wash-in, peak and washout of SI-curves preferably for the peroneus muscle and less predominant also for the tibialis anterior muscle and gastrocnemius muscle respectively. The first case, a 55-year-old female patient with peripheral arterial occlusive disease (pAVK) stage Fontaine IIb before (Figure 3a) and after (Figure 3b) percutaneous transluminal angioplasty (PTA) of a right femoral artery stenosis shows after interventional treatment a rapid post-exercise SI-increase in the peroneus muscle. The steeper SI-curve indicates a better contrast medium inflow due to an improved perfusion. The second case, a 65-year-old man suffering from coronary heart disease without clinical signs of pAVK (Figure 4) exercised with a workload of 92 Ws. After stress test the ROI for the peroneus muscle shows a clear intensity increase. After exercise the SI-curve for the tibialis anterior muscle shows a similar, but less predominant change while the shape of the SI-curve of the gastrocnemius muscle remains mainly identical. A 23-year-old male person with average physical activity (Figure 5) performed DCE-MRT of the left lower leg after stress test with 172 Ws demonstrating a rapid signal increase in the peroneus muscle while the synergistic tibialis anterior muscle and antagonistic gastrocnemius muscle show a comparatively slow contrast-medium wash-in. A 26-year-old male athlete (Figure 6) exercised with 196 Ws showing a rapid contrast medium inflow in the peroneus muscle and initially also in the synergistic tibialis anterior muscle. A contrast-medium wash-out appears in both muscles, while the shape of the gastrocnemius muscle SI-curve remains substantially unchanged. A 26-year-old female athlete (Figure 7) exercised with 244 Ws. Post exercise SI-curves show a distinctive and rapid increase of contrast medium wash-in with a sharp peak particularly in the peroneus muscle and similarly in the tibialis anterior and gastrocnemius muscle. After exercise all SI-curves show a wash-out phase. CONCLUSION: SI-curves show relative increase in correlation with Time-to-Peak (TTP) decrease and Mean-Intensity to Time Ratio (MITR) increase indicating blood flow reserve mobilization after exercise. Individual muscle state seems to be linked to muscle recruitment and muscle coordination reflected by post-exercise SI-curves. The gastrocnemius muscle shows comparatively low SI-curve changes after muscular load test. Further methodological standardization and optimization of the stress test is mandatory to assure intra- and interindividual comparisons. Due to direct visualization and quantitative evaluation of the peripheral microcirculation DCE-MRT has a diagnostic potential for monitoring therapeutic response in peripheral circulation disorders and sports medicine.  相似文献   
105.
OBJECTIVES: The goal of this study was to detect transplant arteriopathy (Tx-CHD) by a reduced myocardial perfusion reserve (MPR) and resting endomyocardial/epimyocardial perfusion ratio (Endo/Epi ratio). BACKGROUND: Transplant arteriopathy often lacks clinical symptoms and is the reason for frequent surveillance angiography in heart transplant (Tx) recipients. Magnetic resonance perfusion imaging (MRPI) allows noninvasive assessment of transmural and selective endomyocardial and epimyocardial perfusion. METHODS: Fifteen healthy volunteers (controls) and three groups (A, B, C) of Tx recipients were included. In controls and patients, MPR (hyperemic/resting perfusion) and Endo/Epi ratio were determined with MRPI after injection of gadolinium-diethylenetriamine pentaacetic acid at rest and during hyperemia (intravenous adenosine). Group A (n = 10) had no left ventricular (LV) hypertrophy and/or prior rejection, while patients in group B (n = 10) had at least one of these characteristics. Patients in group A and B had a normal coronary angiogram and a coronary flow reserve (CFR) of > or =2.5 (CFR = hyperemic/resting blood flow). Group C (n = 7) had Tx-CHD diagnosed by angiography and a reduced CFR (<2.5). RESULTS: In group C, MPR (1.7 +/- 0.5) and Endo/Epi ratio (1.1 +/- 0.2) were significantly reduced compared with controls (4.2 +/- 0.7 and 1.6 +/- 0.3; both p < 0.0001), group A (3.6 +/- 0.7 and 1.6 +/- 0.2; both p < 0.0001) and B (2.7 +/- 0.9, p < 0.01 and 1.4 +/- 0.1, p < 0.04). Transplant arteriopathy can be excluded by an MPR of >2.3 with sensitivity and specificity of 100% and 85%. If LV hypertrophy and prior rejection are excluded, Tx-CHD can be excluded by an Endo/Epi ratio of >1.3 with 100% and 80%. CONCLUSIONS: Magnetic resonance perfusion imaging detects Tx-CHD by a decreased MPR. After exclusion of LV hypertrophy and prior rejection, resting Endo/Epi ratio alone might be sufficient to indicate Tx-CHD.  相似文献   
106.
Early identification of peritonitis by peritoneal cytokine measurement   总被引:2,自引:2,他引:2  
PURPOSE: The assessment of plasma cytokine levels adds a useful tool to the diagnostic measures in severe inflammatory diseases. Proinflammatory cytokine levels in abdominal fluid after abdominal surgery have been shown to far exceed plasma cytokine levels. Thus, we investigated the local release of interleukin 1, interleukin 6, and tumor necrosis factor- in patients after colorectal surgery during the early postoperative period to evaluate whether it may serve as an indicator of evolving peritonitis. METHOD: In a prospective, observational pilot study, the first 12 consecutive patients who did not develop any postoperative complications (Group I), and the first 12 patients with secondary peritonitis caused by an anastomotic leakage (Group II), were included in the study. Interleukin 6, interleukin 1, and tumor necrosis factor- levels were determined in the abdominal exudate and compared between the groups within the first four days after colorectal surgery. RESULTS: Abdominal fluid interleukin 6 levels in Group II patients were higher (162,500 ± 105,800 pg/ml) as early as the first postoperative day compared with Group I (27,940 ± 13,860 pg/ml; P < 0.0001); this lasted for the whole observation period. The same applies to tumor necrosis factor- levels (461.4 ± 167.8 pg/ml vs. 175.8 ± 178.6 pg/ml on day 1; P = 0.0007). The difference in interleukin 1 cytokine levels became statistically significant on the third postoperative day. Moreover, abdominal fluid cytokine levels rose in Group II, whereas they remained virtually unchanged or even tended to decrease over time in Group I. CONCLUSION: We suggest that the estimation of the peritoneal cytokine levels might be an additional diagnostic tool that can support the early recognition of peritonitic complications in colorectal surgery.  相似文献   
107.

Purpose

While their negative impact on bone health is well established, the effects of aromatase inhibition (AI) on Wnt inhibitors and osteoprotegerin (OPG) are unknown. The aim of the study was to investigate the effects of AI on serum levels of sclerostin, DKK-1 and OPG, as well as their associations with PINP and CTX as markers of bone turnover and bone mineral density (BMD) assessed by DXA.

Methods

We conducted a prospective longitudinal analysis of 70 postmenopausal women with hormone receptor-positive early breast cancer (BC) treated with anastrozole. All measurements were performed at baseline, 12 and 24 months of treatment. We measured the association of the investigated variables with circulating bone turnover markers, as well as with the BMD.

Results

After 24 months of AI therapy, sclerostin and OPG concentrations increased from 29.5 pmol/l (SD = 15.1) and 6.8 pmol/l (SD = 2.2) at baseline to 43.2 pmol/l (SD = 20.6) (p < 0.001) and 7.4 pmol/l (SD = 2.2) (p = 0.028), respectively. DKK-1 levels decreased from 34.3 pmol/l (SD = 13.5) at baseline to 29.7 pmol/l (SD = 12.3) at the 24-month visit (p = 0.005). Sclerostin levels significantly correlated with PTH, OPG and BMD of the lumbar spine, while DKK-1 correlated with the BMD of the femoral neck and of the total hip.

Conclusions

The observed increase in sclerostin levels indicates a central role of osteocytes in bone turnover in women with BC.  相似文献   
108.
Journal of Neuroimmune Pharmacology - We evaluated the relationship between blood levels of inflammatory and neurotrophic proteins during the first postnatal month in 692 children born before the...  相似文献   
109.
110.

BACKGROUND

Disorders of sex development (DSD) are a heterogeneous group of rare genetic disorders of sex determination or differentiation. Evidence-based guidelines concerning gender assignment and surgical and hormonal treatment are limited for many DSD entities, and health care is highly fragmented across various sub-specialties and settings. A lack of informed consent, secrecy about the condition, shame, and impaired sexual and psychosocial functioning may affect satisfaction with care.

OBJECTIVES

The main goal of this study was to describe satisfaction with care in individuals with DSD and to identify factors associated with low satisfaction with care.

METHODS / MAIN MEASURES

Using both biological (chromosomes) and social categories (sex of rearing), we classified participants according to the nomenclature of the European Society for Pediatric Endocrinology/Lawson Wilkins Pediatric Endocrine Society (ESPE/LWPES) consensus statement. We used standardized measures to assess satisfaction with care (CSQ-8), health-related quality of life (SF-36), psychological symptoms (BSI), and gender identity (FGI), in addition to self-constructed questionnaires probing experiences with health care and access to self-help groups.

PARTICIPANTS

A total of 110 adults were recruited between January 2005 and December 2007 in four study centers in Germany, Austria, and German-speaking Switzerland.

RESULTS

Reports of half the participants scored below the cut-off indicating low quality of care. Women with XX DSD conditions and virilization (i.e., congenital adrenal hyperplasia) reported the highest scores for satisfaction with care, and women with XY DSD conditions and complete lack of androgen effects reported the lowest scores. Satisfaction with care was positively associated with indicators of psychological well-being.

CONCLUSIONS

Satisfaction with care is lowest among participants with the rarest conditions, highlighting the lack of evidence-based recommendations and the lack of coordination of care. Associations of satisfaction and well-being indicate the need to ensure access to mental health services.
  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