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   5593篇
  免费   869篇
  国内免费   317篇
  2024年   19篇
  2023年   162篇
  2022年   138篇
  2021年   361篇
  2020年   382篇
  2019年   590篇
  2018年   336篇
  2017年   219篇
  2016年   231篇
  2015年   257篇
  2014年   480篇
  2013年   452篇
  2012年   328篇
  2011年   366篇
  2010年   209篇
  2009年   229篇
  2008年   221篇
  2007年   236篇
  2006年   201篇
  2005年   170篇
  2004年   143篇
  2003年   118篇
  2002年   112篇
  2001年   89篇
  2000年   78篇
  1999年   65篇
  1998年   48篇
  1997年   43篇
  1996年   48篇
  1995年   53篇
  1994年   48篇
  1993年   46篇
  1992年   49篇
  1991年   35篇
  1990年   38篇
  1989年   14篇
  1988年   20篇
  1987年   16篇
  1986年   13篇
  1985年   23篇
  1984年   21篇
  1983年   12篇
  1982年   9篇
  1981年   7篇
  1980年   7篇
  1979年   13篇
  1978年   6篇
  1977年   9篇
  1975年   3篇
  1973年   2篇
排序方式: 共有6779条查询结果,搜索用时 32 毫秒
71.
ZUZANA DEANS 《Bioethics》2013,27(1):48-57
Pharmacists who refuse to provide certain services or treatment for reasons of conscience have been criticized for failing to fulfil their professional obligations. Currently, individual pharmacists in Great Britain can withhold services or treatment for moral or religious reasons, provided they refer the patient to an alternative source. The most high‐profile cases have concerned the refusal to supply emergency hormonal contraception, which will serve as an example in this article. I propose that the pharmacy profession's policy on conscientious objections should be altered slightly. Building on the work of Brock and Wicclair, I argue that conscientious refusals should be acceptable provided that the patient is informed of the service, the patient is redirected to an alternative source, the refusal does not cause an unreasonable burden to the patient, and the reasons for the refusal are based on the core values of the profession. Finally, I argue that a principled categorical refusal by an individual pharmacist is not morally permissible. I claim that, contrary to current practice, a pharmacist cannot legitimately claim universal exemption from providing a standard service, even if that service is available elsewhere.  相似文献   
72.
Microcystic adnexal carcinoma (MAC) is an infiltrative rare cutaneous neoplasm for which there are no consensus management guidelines because of the paucity of evidence-based practice; hence, the utility of their management is based only on previously published case reports. We report a case of a scalp lesion that was successfully treated using a combination of surgical resection, chemotherapy, and radiotherapy.  相似文献   
73.
In this study, we investigated the ability of curcumin alone or in combination with GLUT1 siRNA to radiosensitize laryngeal carcinoma (LC) through the induction of autophagy. Protein levels in tumour tissues and LC cells were measured by immunohistochemistry and Western blotting. In vitro, cell proliferation, colony formation assays, cell death and autophagy were detected. A nude mouse xenograft model was established through the injection of Tu212 cells. We found that GLUT1 was highly expressed and negatively associated with autophagy-related proteins in LC and that curcumin suppressed radiation-mediated GLUT1 overexpression in Tu212 cells. Treatment with curcumin, GLUT1 siRNA, or the combination of the two promoted autophagy. Inhibition of autophagy using 6-amino-3-methypourine (3-MA) promoted apoptosis after irradiation or treatment of cells with curcumin and GLUT1 siRNA. 3-MA inhibited curcumin and GLUT1 siRNA-mediated non-apoptotic programmed cell death. The combination of curcumin, GLUT1 siRNA and 3-MA provided the strongest sensitization in vivo. We also found that autophagy induction after curcumin or GLUT1 siRNA treatment implicated in the AMP-activated protein kinase-mTOR-serine/threonine-protein kinase-Beclin1 signalling pathway. Irradiation primarily caused apoptosis, and when combined with curcumin and GLUT1 siRNA treatment, the increased radiosensitivity of LC occurred through the concurrent induction of apoptosis and autophagy.  相似文献   
74.
The pro-inflammatory and pro-fibrotic liver microenvironment facilitates hepatocarcinogenesis. However, the effects and mechanisms by which the hepatic fibroinflammatory microenvironment modulates intrahepatic hepatocellular carcinoma (HCC) progression and its response to systematic therapy remain largely unexplored. We established a syngeneic orthotopic HCC mouse model with a series of persistent liver injury induced by CCl4 gavage, which mimic the dynamic effect of hepatic pathology microenvironment on intrahepatic HCC growth and metastasis. Non-invasive bioluminescence imaging was applied to follow tumour progression over time. The effect of the liver microenvironment modulated by hepatic injury on sorafenib resistance was investigated in vivo and in vitro. We found that the persistent liver injury facilitated HCC growth and metastasis, which was positively correlated with the degree of liver inflammation rather than the extent of liver fibrosis. The inflammatory cytokines in liver tissue were clearly increased after liver injury. The two indicated cytokines, tumour necrosis factor-α (TNF-α) and interleukin-6 (IL-6), both promoted intrahepatic HCC progression via STAT3 activation. In addition, the hepatic inflammatory microenvironment contributed to sorafenib resistance through the anti-apoptotic protein mediated by STAT3, and STAT3 inhibitor S3I-201 significantly improved sorafenib efficacy impaired by liver inflammation. Clinically, the increased inflammation of liver tissues was accompanied with the up-regulated STAT3 activation in HCC. Above all, we concluded that the hepatic inflammatory microenvironment promotes intrahepatic HCC growth, metastasis and sorafenib resistance through activation of STAT3.  相似文献   
75.
《Biomarkers》2013,18(3):259-265
Postoperative atrial fibrillation (AF) is a well-known complication occurring after thoracic surgery. B-type natriuretic peptide has recently been investigated as a predictive marker of postoperative AF after cardiac surgery. The aim of this study was to evaluate a definite cut-off for N-terminal pro-B type natriuretic peptide (NT-proBNP) in predicting postoperative AF in lung cancer patients. NT-proBNP was determined before and after surgery in 400 patients. Cardiac function was monitored by continuous postoperative ECG and clinical cardiological evaluation. AF occurred in 18% of the patients. Receiver operating characteristic curve analyses identified a cut-off of 182.3?ng l?1 as the one with the highest sensitivity and specificity. Perioperative increased levels of NT-proBNP seem to predict postoperative AF in patients undergoing thoracic surgery, and a single cut-off of 182.3?ng l?1 can be used to select high-risk patients who could receive preventive therapy, leading to a considerable decrease in the total costs associated with the management of this complication.  相似文献   
76.
77.
I. Sternberg, R. Rona, S. Olsfanger, S. Lew and I. Leibovitch The clinical significance of class III (suspicious) urine cytology Background: Urine cytology, combined with cystoscopy, is the mainstay of the diagnosis and surveillance of urothelial carcinoma (UC). While classes I and II urine cytology are considered benign and classes IV and V are considered malignant the clinical significance of class III urine cytology is unclear. We evaluated the positive predictive value of class III urine cytology for concurrent and subsequent UC. Methods: The records of all class III urine cytology cases during a 3‐year period were retrospectively reviewed for the presence of concurrent and subsequent UC, determined by cystoscopy and histological confirmation. Results: Of 111 cases, 54 (48.7%) were associated with concurrent UC and 14 (12.6%) with subsequent UC after an initial evaluation negative for malignancy, with a mean time to diagnosis of 10.8 months. Of 27 cases of class III urine cytology with no prior history of UC, 13 (48.1%) had concomitant UC and none had subsequent UC. Of 84 cases of class III urine cytology with a prior history of UC, 41 (48.8%) had a concomitant diagnosis of UC and 14 (16.7%) developed UC during their follow‐up, leading to a total of 55 (65.5%) cases of UC. Conclusions: Patients with class III urine cytology and a prior history of UC should undergo a full initial evaluation of their urinary tract, and should be followed vigorously if this evaluation is negative for malignancy. Patients without a prior diagnosis of UC and class III urine cytology should also undergo a full initial evaluation, while further larger studies are needed to elucidate the need for further follow‐up in such patients.  相似文献   
78.
79.
Two blood group B active glycosphingolipids (B-I and B-II) previously isolated and highly purified from human B erythrocytes [21] were analysed first by degradation with α-D-galactosidase from coffee beans, α-L-fucosidase from bovine kidney and with 0,1 N trichloracetic acid; the native B-glycolipids as well as their degradation products were then investigated by methylation analysis with combined gas chromatography-mass spectrometry, by thin layer chromatography, twodimensional immunodiffusion and by the hemagglutination inhibition technique. Together with the results obtained by mass spectrometry of permethylated glycolipids [26] the following structures were elucidated: α-D-galactopyranosyl-(1 → 3)-[α-L-fucopyranosyl-(1 → 2)]-D-galactopyranosyl-(1 → 4)-N-acetyl-D-glucosaminosyl-(1 → 3)-D-galactopyranosyl-(1 → 4)-D-glucopyranosyl-(1 → 1)-ceramide for the B-I glycosphingolipid and α-D-galactopyranosyl-(1 → 3)-[α-L-fucopyranosyl-(1 → 2)]-D-galactopyranosyl-(1 → 4)-N-acetyl-D-glucosaminosyl-(1 → 3)-D-galactopyranosyl-(1 → 4)-N-acetyl-D-glucosaminosyl-(1 → 3)-D-galactopyranosyl-(1 → 4)-D-glucopyranosyl-(1 → 1)-ceramide for the B-II glycosphingolipid. A H active glycolipid fraction from B erythrocytes further purified by thin layer chromatography was also investigated by methylation analysis. The pattern of its partially methylated alditol acetates was essentially the same as that of the α-galactosidase treated and permethylated B-I glycolipid. It also exhibited strongly precipitating and hemagglutination inhibiting H properties as well as the two α-galactosidase treated B-I and B-II glycosphingolipids. Based upon these data the following tentative structure was proposed: α-L-fucopyranosyl-(1 → 2)-D-galactopyranosyl-(1 → 4)-N-acetyl-D-glucosaminosyl-(1 → 3)-D-galactopyranosyl-(1 → 4)-D-glucopyranosyl-(1 → 1)-ceramide. Gas chromatographic analysis revealed sphingosine and lignoceric, nervonic and behenic acids to be the main components of the ceramide residues of the three glycosphingolipids. From the data presented the H active substance very probably can be regarded as the immediate precursor of the B-I glycosphingolipid from human B erythrocyte membranes.  相似文献   
80.
  1. Download : Download high-res image (236KB)
  2. Download : Download full-size image
Highlights
  • •Using ExCYT, genomics, and Mass Spectrometry, we were able to uncover immune cell marker alterations that provide new insight into the biology of early stage ccRCC.
  • •Among the CD45+ population, we observed a high level of myeloid cell infiltration in treatment-naïve ccRCC tissues.
  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