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   2471篇
  免费   113篇
  国内免费   22篇
耳鼻咽喉   4篇
儿科学   59篇
妇产科学   25篇
基础医学   241篇
口腔科学   21篇
临床医学   265篇
内科学   630篇
皮肤病学   165篇
神经病学   142篇
特种医学   530篇
外科学   207篇
综合类   13篇
预防医学   90篇
眼科学   14篇
药学   106篇
中国医学   2篇
肿瘤学   92篇
  2022年   9篇
  2021年   27篇
  2020年   18篇
  2019年   28篇
  2018年   41篇
  2017年   36篇
  2016年   38篇
  2015年   61篇
  2014年   65篇
  2013年   92篇
  2012年   107篇
  2011年   118篇
  2010年   80篇
  2009年   70篇
  2008年   116篇
  2007年   124篇
  2006年   121篇
  2005年   111篇
  2004年   103篇
  2003年   89篇
  2002年   75篇
  2001年   82篇
  2000年   98篇
  1999年   67篇
  1998年   56篇
  1997年   69篇
  1996年   45篇
  1995年   35篇
  1994年   36篇
  1993年   22篇
  1992年   40篇
  1991年   48篇
  1990年   32篇
  1989年   39篇
  1988年   60篇
  1987年   43篇
  1986年   43篇
  1985年   39篇
  1984年   21篇
  1983年   15篇
  1982年   26篇
  1981年   12篇
  1980年   19篇
  1979年   17篇
  1978年   9篇
  1977年   9篇
  1976年   16篇
  1975年   11篇
  1970年   7篇
  1966年   7篇
排序方式: 共有2606条查询结果,搜索用时 0 毫秒
91.
Aims  In the present study, we investigated the efficacy and safety of candesartan cilexetil (candesartan) as “add-on” treatment in congestive heart failure (CHF) in daily practice. Methods and results  In this open-label, multicenter study 414 CHF outpatients (NYHA II/III) with left ventricular ejection fraction (LVEF) ≤ 40% and plasma brain natriuretic peptide (BNP) levels > 200 pg/ml at baseline were enrolled. Patients were treated with standard therapy including at least one angiotensin converting enzyme inhibitor in addition to another CHF drug; 91% of the patients received beta-blockers. Candesartan was uptitrated to 32 mg/day (target dose if tolerated) during 6 weeks followed by constant dosing over 16 weeks. The primary endpoint plasma BNP was significantly reduced by 25% at week 22 (from 394 to 295 pg/ml, P < 0.0001 vs. baseline). Candesartan produced early and sustained improvements of plasma BNP/NT-pro-BNP, LVEF, and quality of life (SF-36) compared to baseline. Of patients on beta-blockers, 37% improved towards NYHA II/I at week 22 (P < 0.0001) and 53.5% of the patients in NYHA III at baseline improved into NYHA II/I at week 22 (n = 232, P < 0.0001). Candesartan was well tolerated; no unexpected findings were reported besides known adverse reactions including hypotension, hyperkalemia, and serum creatinine elevations. Conclusion  Candesartan “add-on” treatment provides a good benefit/risk ratio in CHF outpatients in daily practice, although high-risk patients should be managed with frequent monitoring of BP, serum potassium, and renal function.  相似文献   
92.
93.
94.
Research has documented the existence of multiple, endogenous systems that modulate nociception. Based on the effects of opioid antagonists and endocrine lesions, endogenous analgesia systems have been organized into four classes: neural-opioid, neural-nonopioid; hormonal-opioid; hormonal-nonopioid. Developmental research on the ontogeny of endogenous analgesic function has revealed differential rates of maturation. Front-paw shock, a stimulus that activates a neural-opioid analgesic response, has been shown to be functionally mature by 28 days of age in the rat. Similarly, hind-paw shock, a stimulus that elicits a neural-nonopioid analgesic response, reaches maturity after two months of age. However, the hormonal-opioid analgesic system activated by cold-water immersion reaches adult levels by 10 days of age. Food deprivation produces a hormonal-opioid analgesic response in adult rats, and food deprivation/isolation of rat pups has been found to elicit an analgesic response in 6-day-old rats. From these data it seems that the rate of development of the different endogenous analgesic systems is related to the activation of neural or hormonal components. Whether the differential rates of development and the neural-hormonal distinction are related to the ecological validity of the activating stimulus remains to be determined.  相似文献   
95.
96.

Objectives

Evaluation of enhancement characteristics of histopathologically confirmed focal nodular hyperplasias (FNHs) and hepatocellular adenomas (HCAs) with gadoxetic acid-enhanced MRI.

Methods

Sixty-eight patients with 115 histopathologically proven lesions (FNHs, n?=?44; HCAs, n?=?71) examined with gadoxetic acid-enhanced MRI were retrospectively enrolled (standard of reference: surgical resection, n?=?53 patients (lesions: FNHs, n?=?37; HCAs, n?=?53); biopsy, n?=?15 (lesions: FNHs, n?=?7; HCAs, n?=?18)). Two radiologists evaluated all MR images regarding morphological features as well as the vascular and hepatocyte-specific enhancement in consensus.

Results

For the hepatobiliary phase, relative enhancement of the lesions and lesion to liver enhancement were significantly lower for HCAs (mean, 48.7 (±48.4) % and 49.4 (±33.9) %) compared to FNHs (159.3 (±92.5) %; and 151.7 (±79) %; accuracy of 89 % and 90 %, respectively; P?<?0.001). Visual strong uptake of FNHs vs. hypointensity of HCAs in the hepatobiliary phase resulted in an accuracy of 92 %. This parameter was superior to all other morphological and dynamic vascular criteria alone and in combination (accuracy, 54–85 %).

Conclusions

For differentiation of FNHs and HCAs by means of MRI, gadoxetic acid uptake in the hepatobiliary phase was found to be superior to all other criteria alone and in combination.

Key Points

? EOB-MRI is well suited to differentiate FNHs and hepatocellular adenomas. ? For this purpose hepatobiliary phase is superior to unenhanced and dynamic imaging. ? Hepatobiliary phase (peripheral) hyper- or isointensity is typical for FNH. ? Hepatobiliary phase hypointensity is typical for hepatocellular adenomas. ? EOB-MRI helps to avoid misinterpretations of benign hepatocellular lesions.  相似文献   
97.
98.
Linear and whorled nevoid hypermelanosis (LWNH) is characterized by hyperpigmented reticulate macules in a Blaschko linear arrangement without atrophy or preceding inflammation. Underlying chromosomal mosaicism was often assumed, but has been verified in only a few published cases. We report a 7-year-old boy with LWNH associated with congenital ventricular septal defect and psychomotor retardation. Prenatal chromosomal analysis of amniocytes revealed trisomy 20 mosaicism, which was not confirmed in peripheral blood lymphocytes after birth. Histologic sections of skin biopsy specimens taken at age 6 years showed hyperpigmentation of the basal epidermal layer with prominent melanocytes and isolated melanophages in the upper dermis. Cytogenetic analysis of cultured skin fibroblasts revealed an extra chromosome 20 in 5 of the 30 metaphases studied (17%). Mosaic trisomy 20 is one of the most common autosomal mosaicisms identified in amniocytes and is, as a rule, compatible with normal pregnancy outcome. In postnatal analysis of peripheral blood lymphocytes, an extra chromosome 20 could never be detected. However, when confirmed in skin fibroblasts, trisomy 20 mosaicism may be associated with systemic anomalies. The present case shows for the first time an association of LWNH with trisomy 20 mosaicism and emphasizes the importance of analyzing skin fibroblasts in cases of prenatally diagnosed trisomy 20.  相似文献   
99.
Forty-six infants in a neonatal intensive care unit and 138 health care workers were exposed to a pediatric medical resident during the prodromal period and the early days of unrecognized varicella. An attempt was made to prevent an outbreak of additional cases by the institution of emergency control measures. These measures included rapid identification of varicella antibody status in exposed neonates, varicella antibody testing of health care workers with unknown or uncertain history of varicella, prompt administration of varicella zoster immune globulin to potentially susceptible persons, and cohorting neonates on the basis of exposure and antibody status. Passive maternal antibody was detected in 44 of the neonates. Of 27 health care workers who reported either a negative or an uncertain history of varicella, 26 had detectable antibody. No overt cases of varicella occurred in exposed patients or personnel.  相似文献   
100.
The differentiation of the urinogenital system and the appendicular skeleton in vertebrates is under the control of Hox genes. The common control of digit and gonad differentiation raises the possibility that patterns of digit formation may relate to spermatogenesis and hormonal concentrations. This work was concerned with the ratio between the length of the 2nd and 4th digit (2D:4D) in humans. We showed that (i) 2D:4D in right and left hands has a sexually dimorphic pattern; in males mean 2D:4D = 0.98, i.e. the 4th digit tended to be longer than the 2nd and in females mean 2D:4D = 1.00, i.e. the 2nd and 4th digits tended to be of equal length. The dimorphism is present from at least age 2 years and 2D:4D is probably established in utero; (ii) high 2D:4D ratio in right hands was associated with germ cell failure in men (P = 0.04); (iii) sperm number was negatively related to 2D:4D in the right hand (P = 0.004); (iv) in men testosterone concentrations were negatively related to right hand 2D:4D and in women and men LH (right hand), oestrogen (right and left hands) and prolactin (right hand) concentrations were positively correlated with 2D:4D ratio and (v) 2D:4D ratio in right hands remained positively related to luteinizing hormone and oestrogen after controlling for sex, age, height and weight.   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