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   1276篇
  免费   106篇
  国内免费   4篇
耳鼻咽喉   18篇
儿科学   31篇
妇产科学   23篇
基础医学   249篇
口腔科学   5篇
临床医学   131篇
内科学   282篇
皮肤病学   19篇
神经病学   145篇
特种医学   32篇
外科学   120篇
综合类   2篇
一般理论   2篇
预防医学   141篇
眼科学   3篇
药学   62篇
中国医学   2篇
肿瘤学   119篇
  2024年   1篇
  2023年   8篇
  2022年   29篇
  2021年   64篇
  2020年   34篇
  2019年   38篇
  2018年   49篇
  2017年   37篇
  2016年   54篇
  2015年   43篇
  2014年   60篇
  2013年   60篇
  2012年   104篇
  2011年   128篇
  2010年   64篇
  2009年   50篇
  2008年   81篇
  2007年   82篇
  2006年   74篇
  2005年   62篇
  2004年   69篇
  2003年   75篇
  2002年   35篇
  2001年   11篇
  2000年   7篇
  1999年   11篇
  1998年   8篇
  1997年   8篇
  1996年   5篇
  1995年   7篇
  1994年   2篇
  1993年   3篇
  1992年   1篇
  1991年   3篇
  1990年   1篇
  1989年   7篇
  1988年   3篇
  1987年   2篇
  1984年   1篇
  1979年   2篇
  1977年   1篇
  1976年   1篇
  1969年   1篇
排序方式: 共有1386条查询结果,搜索用时 15 毫秒
1.
2.
3.
OBJECTIVE: Depression after hip fracture surgery is prevalent and associated with increased mortality rates and impaired functional recovery. The incidence of new-onset depressive symptoms in patients initially not depressed after hip fracture surgery and their relationship with functional recovery is unknown. METHODS: A cohort of 139 nondepressed elderly patients (>60 years) hospitalized for hip fracture surgery were followed up for six months. Clinically significant depressive symptoms were defined as a score of 7 or more on the 15-item Geriatric Depression Scale. RESULTS: The authors found a cumulative incidence rate of 20.5% adjusted for dropouts. Multiple Cox-regression analyses yielded the presence of subthreshold symptoms of depression, anxiety, pain, and cognitive impairment at baseline, the premorbid level of mobility, and a history of (treated) depression as risk factors for incident depression (p <0.05). A forward, conditional procedure identified postoperative pain (hazard ratio [HR] = 1.32, 95% confidence interval [CI]: 1.14-1.53, Wald chi(2) = 13.57, df = 1, p <0.001) and baseline anxiety (HR = 1.25, 95% CI: 1.08-1.44, Wald chi(2) = 8.86, df = 1, p = 0.003) as the strongest independent risk factors. Incident depression was associated with a less favorable outcome at 3 months follow-up. CONCLUSION: This exploratory study identified two treatable baseline characteristics that predicted incident depression in nondepressed patients after hip-fracture surgery.  相似文献   
4.
Summary Recently, a mutant rat strain was described with a genetic defect for the biliary excretion of organic anions (TR rats). To determine the possible heterogeneity of the transport systems in liver, intestine and kidney we investigated the transport of the anion 1-naphthol--d-glucuronide (1-NG) in isolated vascularly perfused organ preparations of the rat liver, intestine and kidney of both Wistar rats and TR rats. 1-NG was administered as such (liver and kidney experiments) or formed intracellularly from 1-naphthol (1-N) (liver and gut experiments). Independent of the type of exposure to 1-NG, the biliary excretion was considerably impaired in TR rats. In the intestine the total appearance and the vascular/luminal distribution pattern of 1-NG were not significantly different from the values in control rats. Furthermore, no significant disturbance was found with respect to the renal clearance of 1-NG in the TR rat when compared with the Wistar rat. Thus, the genetic defect in the TR rat is restricted to an impaired hepatobiliary excretion of 1-NG and does not affect the excretory systems of the intestine and kidney. These results suggest that the excretion of 1-NG by the liver, intestine and kidney involves distinct organ-specific transport systems.  相似文献   
5.
NK cells developing in vitro from fetal progenitors in the presence of IL-2 are phenotypically and functionally indistinguishable from mature adult NK cells, with the exception that they generally lack surface expression of any of the Ly49 molecules that have previously been examined. Using two recently developed anti-Ly49 mAb, we show here that most of these NK cells in fact express high levels of at least one previously uncharacterized member of the Ly49 family, most likely Ly49E. Detailed kinetic and clonal analysis revealed that these Ly49 molecules were acquired in a progressive and stochastic manner independently of CD94 and NKG2. CD94 and NKG2 were both expressed early in NK cell development, sometimes in the absence of NK1.1, with CD94 invariably being expressed at two different levels. IL-4 differentially inhibited the expression of CD94 and Ly49 receptors, but had little or no effect on the expression of NKRP1 molecules.  相似文献   
6.
Due to the sharp increase in liver transplant candidates and the subsequent shortage of suitable donor livers, an extension of the current donor criteria is necessary. Simple cold storage, the current standard in organ preservation has proven to be insufficient to preserve extended criteria donor livers. Therefore a renewed interest grew toward alternative methods for liver preservation, such as hypothermic machine perfusion and normothermic machine perfusion. These “new” preservation methods were primarily assessed in rat models, and only a few clinically relevant large animal models have been described so far. This review will elaborate on these alternative preservation methods. Anat Rec, 291:735–740, 2008. © 2008 Wiley‐Liss, Inc.  相似文献   
7.
The association between bone mass, body structure, and body composition was explored in 156 men, 40 years of AGE . Bone mineral density (total body, lumbar spine, left arm, and left leg) was obtained by dual‐energy X‐ray absorptiometry (DXA; Hologic QDR 4500A). Body structure was determined from a battery of anthropometric dimensions with a principal components analysis. Body composition was estimated with DXA. From the 24 anthropometric dimensions, three components were extracted and identified as muscle, fat, and skeletal length. Significant correlations between the muscle component and all BMD measurements (r = 0.28–0.44) were obtained. Except for BMD of the left arm, which correlated significantly, but negatively, with the fat component (r = ?0.16), no significant relations were found between the fat component and BMD. There were significant correlations between lean mass, fat mass, and BMD measurements. The correlations were higher between lean mass and BMD (r = 0.22–0.44) than between fat mass and BMD (r = 0.08–0.24). The multiple regression analysis revealed that except for BMD of the left arm only lean mass or the muscle component, and not fat mass or the fat component, were independent predictors of BMD. It is concluded that the principal anthropometric determinant of BMD in middle‐aged men is lean mass or muscle. Am. J. Hum. Biol. 14:735–742, 2002. © 2002 Wiley‐Liss, Inc.  相似文献   
8.
Summary A case of ovarian Sertoli-Leydig cell tumour with a raised serum alpha fetoprotein in reported. The patient first presented at the age of 27 years with a history of 6 years' amenorrhoea followed by 3 months irregular vaginal bleeding. A ovarian tumour was found and excised and shown microscopically to be a spindle cell malignant tumour. The patient was treated with chemotherapy and had a complete response. Thirty months after first presentation there was a recurrence in the pelvis which microscopically showed the typical features of a Sertoli-Leydig cell tumour. Six months later a second recurrence had the microscopic appearance of a lipid cell tumour. A raised serum alpha fetoprotein was found at the time of the second recurrence and immunohistochemistry showed this protein in the Leydig and luteinized cells of the recurrent tumours but not in the spindle cells of the original ovarian neoplasm.  相似文献   
9.
Using a new antibody, we found previously that contrary to adult natural killer (NK) cells, fetal NK cells have a unique phenotype, as they exclusively express Ly49E. This can be explained by an intrinsic different NK differentiation potential of fetal versus adult lymphoid progenitors, by immaturity of fetal NK cells or by instability of Ly49E expression. Here, we show that adult progenitor cells were still capable of differentiating into Ly49E-expressing NK cells but at a much lower frequency. Surprisingly, Ly49E expression in vitro did not require stromal cells. Kinetic analysis in vivo showed that Ly49E was expressed early, together with CD94/NKG2 and Ly49G2, followed by Ly49C, and finally Ly49D. Transfer of sorted Ly49E-positive fetal NK cells showed stable Ly49E expression, and later, part of these cells up-regulated other Ly49 members. These data indicate that although there are intrinsic differences, there is no strict fetal and adult wave of NK cell differentiation.  相似文献   
10.
Increased amino acid availability acutely stimulates protein synthesis partially via activation of mechanistic target of rapamycin complex 1 (mTORC1). Plant-and insect-based protein sources matched for total protein and/or leucine to animal proteins induce a lower postprandial rise in amino acids, but their effects on mTOR activation in muscle are unknown. C57BL/6J mice were gavaged with different protein solutions: whey, a pea–rice protein mix matched for total protein or leucine content to whey, worm protein matched for total protein, or saline. Blood was drawn 30, 60, 105 and 150 min after gavage and muscle samples were harvested 60 min and 150 min after gavage to measure key components of the mTORC1 pathway. Ingestion of plant-based proteins induced a lower rise in blood leucine compared to whey, which coincided with a dampened mTORC1 activation, both acutely and 150 min after administration. Matching total leucine content to whey did not rescue the reduced rise in plasma amino acids, nor the lower increase in mTORC1 compared to whey. Insect protein elicits a similar activation of downstream mTORC1 kinases as plant-based proteins, despite lower postprandial aminoacidemia. The mTORC1 response following ingestion of high-quality plant-based and insect proteins is dampened compared to whey in mouse skeletal muscle.  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