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   7137篇
  免费   322篇
  国内免费   56篇
耳鼻咽喉   108篇
儿科学   100篇
妇产科学   88篇
基础医学   944篇
口腔科学   202篇
临床医学   418篇
内科学   1936篇
皮肤病学   127篇
神经病学   488篇
特种医学   164篇
外科学   1257篇
综合类   22篇
预防医学   216篇
眼科学   208篇
药学   506篇
中国医学   4篇
肿瘤学   727篇
  2023年   29篇
  2022年   63篇
  2021年   127篇
  2020年   67篇
  2019年   90篇
  2018年   147篇
  2017年   109篇
  2016年   138篇
  2015年   155篇
  2014年   153篇
  2013年   236篇
  2012年   378篇
  2011年   425篇
  2010年   238篇
  2009年   210篇
  2008年   367篇
  2007年   405篇
  2006年   401篇
  2005年   419篇
  2004年   395篇
  2003年   406篇
  2002年   393篇
  2001年   160篇
  2000年   189篇
  1999年   149篇
  1998年   132篇
  1997年   91篇
  1996年   75篇
  1995年   50篇
  1994年   70篇
  1993年   55篇
  1992年   127篇
  1991年   113篇
  1990年   105篇
  1989年   95篇
  1988年   102篇
  1987年   88篇
  1986年   64篇
  1985年   79篇
  1984年   39篇
  1983年   35篇
  1982年   27篇
  1979年   24篇
  1978年   25篇
  1975年   20篇
  1974年   19篇
  1971年   22篇
  1970年   22篇
  1969年   23篇
  1967年   23篇
排序方式: 共有7515条查询结果,搜索用时 31 毫秒
161.
162.
Calcium ions (Ca2+) are indispensable for the physiology of organisms and the molecular regulation of cells. We observed that CGK733, a synthetic chemical substance, induced non-apoptotic cell death and stimulated reversible calcium sequestration by vesicles in pancreatic cancer cells. The endoplasmic reticulum (ER) stress eukaryotic translation initiation factor 2-alpha kinase 3/C/EBP homologous protein (PERK/CHOP) signaling pathway was shown to be activated by treatment with CGK733. Ionomycin, an ER stress drug and calcium ionophore, can activate PERK/CHOP signaling and accelerate CGK733-induced calcium sequestration. Knockdown of CHOP diminished CGK733-induced vesicular calcium sequestration, but had no effects on the cell death. Proteomic analysis demonstrated that the ER-located calcium-binding proteins, calumenin and protein S100-A11, were altered in CGK733-treated cells compared to non-treated controls. Our study reveals that CGK733-induced intracellular calcium sequestration is correlated with the PERK/CHOP signaling pathway and may also be involved in the dysregulations of calcium-binding proteins.  相似文献   
163.
The purpose of our study was to evaluate the diagnostic accuracy of the ultrasound-guided attenuation parameter (UGAP) for the detection of hepatic steatosis in comparison with the controlled attenuation parameter (CAP), using histopathology as the reference standard. We prospectively analyzed 163 consecutive chronic liver disease patients who underwent UGAP, CAP, computed tomography and a liver biopsy on the same day between April 2016 and July 2017. Radiofrequency signals corresponding to the images were compensated by the reference signal previously measured from the uniform phantom with known attenuation (0.44 dB/cm/MHz). The attenuation coefficient was calculated from the signals’ decay slope. The median attenuation coefficient values in patients with S0 (n?=?62), S1 (n?=?63), S2 (n?=?23) and S3 grade (n?=?15) were 0.485, 0.560, 0.660 and 0.720, respectively. Significant correlations were found between attenuation coefficient and percentage steatosis, CAP values and liver-to-spleen computed tomography attenuation ratio (p < 0.001). The areas under the receiver operating characteristic curve of UGAP for identifying ≥S1, ≥S2 and ≥S3 were 0.900, 0.953 and 0.959, respectively, which were significantly better than the results obtained with CAP for identifying ≥S2 and ≥S3. In conclusion, UGAP had high diagnostic accuracy for detecting hepatic steatosis in patients with chronic liver disease  相似文献   
164.
165.
1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) induces damage to the nigrostriatal system and subventricular zone (SVZ) of mice. While there have been many researches on the neurotoxicity of MPTP in adult mice, there have been few reports concerning that in embryonic and newborn mice. Very recently, we revealed that such neurotoxicity of MPTP and 1-methyl-4-phenylpyridinium (MPP+), a metabolite of MPTP, is observed not only in adult mice but also in embryonic and newborn mice; however, the mechanism of acute toxicity is not well elucidated. In the present study, we attempted to reveal the involvement of monoamine oxidase B (MAO-B) in the metabolism of MPTP to MPP+ and dopamine transporter (DAT) in the neuronal cellular uptake of MPP+ during the acute toxicity of MPTP in both embryonic and newborn mice. Immunohistochemistry and double-labeling immunofluorescent staining demonstrated an increase of MAO-B-positive glial cells in the brain only in MPTP-treated mice, indicating the involvement of MAO-B in the metabolism of MPTP to MPP+ during the acute neurotoxicity of MPTP in both embryonic and newborn mice. The expression of DAT was not observed in the nigrostriatal zone of embryonic mice and in the zone and SVZ of newborn mice. The mechanism of how MPP+ is taken up into those neuronal cells remains unknown. In conclusion, MAO-B is involved in the acute neurotoxicity of MPTP in embryonic and newborn mice.  相似文献   
166.
Purpose: We investigated the influence of intraoperative continuous tranexamic acid (TA) infusion on the amount of blood transfusion required in emergency surgery for type A acute aortic dissection.Methods: The study was based on the data of 55 consecutive patients who underwent surgery for type A acute aortic dissection. The patients were divided into 2 groups for comparison: Group T, consisting of 26 patients who received intraoperative continuous infusion of TA, and Group N, consisting of 29 patients who did not receive TA infusion during the surgery.Results: The mean amounts of blood transfusion required during and after surgery were compared between the 2 groups: they were 10.5 ± 8.7 and 16.2 ± 10.0 units of mannitol-adenine-phosphate-added red cell concentrate, 9.3 ± 8.6 and 17.1 ± 10.0 units of fresh frozen plasma, and 20.4 ± 12.2 and 29.7 ± 14.9 units of platelet concentrate, respectively, in Groups T and N. Thus, the amount of each of these blood products required was significantly reduced in Group T.Conclusions: During emergency surgery for type A acute aortic dissection, continuous infusion of TA resulted in a significant reduction in the amount of blood transfusion required.  相似文献   
167.
Rickettsia diseases, including Japanese spotted fever (JSF), are serious infections. Delayed diagnosis occasionally results in life‐threatening liver disorders and disseminated intravascular coagulation (DIC). Because of the shortness of the latent period, serological diagnosis is not preferable for early diagnosis of JSF. Until now, a polymerase chain reaction (PCR)‐based diagnosis method has been used for early diagnosis, and the sensitivity reaches as high as 90% using skin biopsy samples as we previously reported. On the other hand, the sensitivity of the same PCR method using blood samples is limited at less than 50%. In the present study, using peripheral blood samples, we developed a novel diagnostic method for JSF using a Rick PCR system with original PCR primers, showing improved sensitivity compared with the conventional nested PCR. It may constitute a preferable diagnostic tool for early and sensitive diagnosis of Rickettsia infection.  相似文献   
168.
BackgroundAlthough acetabular dysplasia is a common etiology of osteoarthritis of the hip regardless of the history of developmental dysplasia of the hip (DDH), whether or not corrective surgeries are beneficial for the childhood asymptomatic acetabular dysplasia remains controversial due to a lack of evidence. We conducted a longitudinal study to compare the cartilaginous morphology on childhood magnetic resonance imaging (MRI) and the mature hip morphology of the same patient and to assess the predictive indicators for future acetabular dysplasia.MethodsA total of 92 unaffected hips (47 unilateral DDH and 45 unilateral Legg-Calvé-Perthes disease) were reviewed for X-ray and MRI findings on childhood (mean age: 6.0 years) and X-ray findings from a skeletally mature age with a mean follow-up period of 15.1 years. The following parameters were measured and compared: the immature-acetabular index (AI) and center edge angle (CE) on immature X-ray; the cartilage- and bone- AI, CE, Sharp and acetabular head index (AHI) on childhood MRI; and the mature-acetabular roof obliquity (ARO), CE, Sharp and AHI on skeletally mature X-ray. The prognostic factors on childhood MRI for acetabular dysplasia, defined by a CE of <20° on skeletally mature X-ray were also assessed.ResultsPositive correlations were shown between the cartilage-AI and mature-ARO (7.6°/6.3°; r = 0.44), the cartilage-CE and mature-CE (27.8°/28.0°; r = 0.62), the cartilage-Sharp and mature-Sharp (44.4°/41.8°; r = 0.52) and the cartilage-AHI and mature-AHI (78.7%/80.3%; r = 0.46). A multivariate analysis indicated cartilage-CE to be an independent predictor for acetabular dysplasia with a cut-off value of 22°. Children with a cartilage-CE <22° developed more frequently acetabular dysplasia compared to the others (52.4% vs. 1.4%).ConclusionsChildhood MRI findings are useful for the prediction of acetabular dysplasia without a DDH history. Children with a cartilage-CE ≥23° are likely to achieve a non-dysplastic hip without the need for surgical intervention.  相似文献   
169.
Intraperitoneal 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) administration induces apoptosis of subventricular zone (SVZ) doublecortin (Dcx)-positive neural progenitor cells (migrating neuroblasts, A cells). Actually, a metabolite of MPTP, 1-methy-4-phenylpiridinium (MPP+), is responsible for neural progenitor cell toxicity. In the present study, to examine whether the MPTP-induced SVZ cell apoptosis is caused directly by MPP+ metabolized through monoamine oxidase B (MAO-B), MPTP or MPP+ was intracerebroventricularly (icv) injected into C57BL/6 mice. At Day 1 postinjection, many terminal deoxynucleotidyl transferase-mediated dUTP endlabeling (TUNEL)-positive cells were observed in the SVZ of both low (36 μg) and high (162 μg) dose MPTP- and MPP+-injected mice. The number of Dcx-positive A cells showed a significant decrease following high dose of MPTP- or MPP+-injection on Days 1 and 3, respectively, whereas that of EGFR-positive C cells showed no change in mice with any treatment. In addition, prior icv injection of a MAO-B inhibitor, R(?)-deprenyl (deprenyl), inhibited MPTP-induced apoptosis, but not MPP+-induced apoptosis. MAO-B- and GFAP-double positive cells were detected in the ependyma and SVZ in all mice. It is revealed from these results that icv injection of MPTP induces apoptosis of neural progenitor cells (A cells) in the SVZ via MPP+ toxicity. In addition, it is suggested that the conversion from MPTP to MPP+ is caused mainly by MAO-B located in ependymal cells and GFAP-positive cells in the SVZ.  相似文献   
170.
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