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   61519篇
  免费   5506篇
  国内免费   4085篇
耳鼻咽喉   529篇
儿科学   817篇
妇产科学   1069篇
基础医学   7827篇
口腔科学   975篇
临床医学   7903篇
内科学   9653篇
皮肤病学   703篇
神经病学   3674篇
特种医学   2286篇
外国民族医学   52篇
外科学   6278篇
综合类   8191篇
现状与发展   19篇
一般理论   3篇
预防医学   4107篇
眼科学   1758篇
药学   6468篇
  63篇
中国医学   3089篇
肿瘤学   5646篇
  2024年   670篇
  2023年   959篇
  2022年   2406篇
  2021年   3145篇
  2020年   2322篇
  2019年   2163篇
  2018年   2263篇
  2017年   1905篇
  2016年   1904篇
  2015年   2711篇
  2014年   3360篇
  2013年   2837篇
  2012年   4490篇
  2011年   4959篇
  2010年   2975篇
  2009年   2282篇
  2008年   3150篇
  2007年   3176篇
  2006年   3175篇
  2005年   3136篇
  2004年   2145篇
  2003年   2074篇
  2002年   1791篇
  2001年   1253篇
  2000年   1315篇
  1999年   1412篇
  1998年   936篇
  1997年   882篇
  1996年   675篇
  1995年   618篇
  1994年   510篇
  1993年   334篇
  1992年   419篇
  1991年   370篇
  1990年   328篇
  1989年   284篇
  1988年   294篇
  1987年   241篇
  1986年   232篇
  1985年   182篇
  1984年   127篇
  1983年   98篇
  1982年   54篇
  1981年   52篇
  1980年   40篇
  1979年   97篇
  1978年   41篇
  1975年   40篇
  1974年   52篇
  1973年   30篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.

Background

Programmed death ligand-1 (PD-L1) is a potential predictive biomarker for immunotherapy in several malignancies. However, the expression level and clinical significance of PD-L1 in von Hippel–Lindau (VHL)-associated hereditary clear-cell renal cell carcinoma (ccRCC) remain unclear.

Patients and Methods

Surgical specimens were recruited from 129 patients with sporadic ccRCC and 26 patients with VHL-associated hereditary ccRCC. The PD-L1 expression level was assessed using immunohistochemistry. Correlations between PD-L1 expression and clinicopathological features were analyzed.

Results

In sporadic ccRCC, the positive expression rate of PD-L1 was 47.3% (61/129). Positive PD-L1 expression was correlated with advanced tumor T stage (P = .011), higher Fuhrman nuclear grade (P = .022), poor disease-free survival (P = .037), and sex (P = .025). In the VHL-associated hereditary ccRCC, positive PD-L1 expression rate was 34.6% (9/26), lower than that in sporadic ccRCC. Positive PD-L1 was correlated with higher Fuhrman nuclear grade (P = .008), but not with sex, age, tumor stage, or the onset age of VHL-associated tumors.

Conclusion

Positive PD-L1 expression was correlated with the aggressive clinicopathological features in sporadic and VHL-associated hereditary ccRCC. Whether PD-L1 expression level in ccRCC is related to the effectiveness of programmed death-1/PD-L1 checkpoint inhibitor immunotherapy needs to be further investigated.  相似文献   
2.
Objective To analyze the pathological characteristics and prognostic factors of antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV). Methods A retrospective analysis of AAV patients with renal biopsy results admitted to Kidney Disease Center of the First Affiliated Hospital from January 2004 to February 2017 was performed. The patients were divided into 4 types according to Berden classification, and their clinical, pathological characteristics and prognosis were compared. The survival curves of each type of patients were plotted by Kaplan-Meier method, and the difference of survival curves was compared using Log-rank test. With entering the maintenance dialysis as the endpoint, Cox regression was used to analyze the prognostic factors. Results A total of 175 patients with AAV, including 59 cases (33.7%) of focal type, 39 cases (22.3%) of crescent type, 32 cases (18.3%) of sclerosis type, 45 cases (25.7%) of mixed type. The basal serum creatinine levels in crescent type group and sclerosis type group were significantly higher than those in the focal type group or mixed type group (all P<0.05), and loop necrosis rate in sclerosis type group was significantly lower than chat in the focal type group or crescent type group (both P<0.05). The median follow-up period was 11.8 (0.5-86.7) months. The event-free survival rates were 83.1%, 77.8%, 64.1% and 50.0% in the focal type, mixed type, crescent type and sclerotic type groups (Log-rank χ2=11.537, P=0.009). Cox regression analysis showed higher parathyroid hormone (HR=1.013, 95%CI 1.007-1.019, P<0.001), glomerular sclerosis ≥50% (HR=10.532, 95%CI 2.903-38.203, P<0.001) were independent risk factors for AAV patients entering maintenance dialysis, and higher estimated glomerular filtration rate (HR=0.943, 95%CI 0.896-0.993, P=0.025) was protective factor. Conclusion The prognosis of AAV renal damage is worsened according to focal, mixed, crescent and sclerosis types. Lower estimated glomerular filtration rate, higher parathyroid hormone and glomerular sclerosis ≥50% are independent risk factors for AAV patients entering maintenance dialysis.  相似文献   
3.
Axonal regeneration plays an important role in functional recovery after nervous system damage. However, after axonal injury in mammals, regeneration is often poor. The deletion of Krüppel-like factor-4 (Klf4) has been shown to promote axonal regeneration in retinal ganglion cells. However, the effects of Klf4 deletion on the corticospinal tract and peripheral nervous system are unknown. In this study, using a mouse model of sciatic nerve injury, we show that the expression of Klf4 in dorsal root ganglion sensory neurons was significantly reduced after peripheral axotomy, suggesting that the regeneration of the sciatic nerve is associated with Klf4. In vitro, dorsal root ganglion sensory neurons with Klf4 knockout exhibited significantly enhanced axonal regeneration. Furthermore, the regeneration of the sciatic nerve was enhanced in vivo following Klf4 knockout. Finally, AAV-Cre virus was used to knockout the Klf4 gene in the cortex. The deletion of Klf4 enhanced regeneration of the corticospinal tract in mice with spinal cord injury. Together, our findings suggest that regulating KLF4 activity in neurons is a potential strategy for promoting axonal regeneration and functional recovery after nervous system injury. This study was approved by the Animal Ethics Committee at Soochow University, China (approval No. SUDA20200316A01).

Chinese Library Classification No.R456; R741; Q344+.14  相似文献   
4.

Study objectives

The primary objective of this study was to compare Emergency Department patients with first-time versus recurrent acute pancreatitis.

Methods

This study was a retrospective chart review of patients with a diagnosis of acute pancreatitis who presented to a single academic urban emergency department from 2012 to 2016. Criteria for inclusion were clinical symptoms of pancreatitis, age greater than or equal to 18?years, ED diagnosis of acute pancreatitis, and an abdominal CT scan within 24?h of triage. Exclusion criteria were traumatic mechanism and pregnancy. Charts were reviewed by a minimum of two trained abstractors using structured data collection sheets and discrepancies were resolved by a third abstractor. Patients with first time acute pancreatitis versus recurrent acute pancreatitis were compared to determine differences in characteristics, management and disposition.

Results

250 patients were included in the study. Of these, 165 patients had first-time acute pancreatitis and 85 patients had recurrent acute pancreatitis. Demographics, vital signs and initial lab values were the same in both groups. Patients with recurrent acute pancreatitis were more likely to have significant findings on CT (Modified CT Severity Index, 2.09 versus 1.43, p?<?0.05), more likely to require IV opiates (96% versus 75%, p?<?0.001) and less likely to need ICU admission (8% versus 19%, p?=?0.03).

Conclusion

ED patients with recurrent acute pancreatitis demonstrated more significant findings on CT compared to patients with first-time acute pancreatitis but were less likely to require ICU admission.  相似文献   
5.
目的探讨前列腺原发胃肠道外间质瘤诊治要点。 方法回顾性分析我院2017年9月诊治的1例高危原发性前列腺胃肠道外间质瘤临床病理特征资料、随访情况,总结现有文献讨论总结本病诊治心得。 结果65岁男性,因"前列腺电切术后2年,反复血尿3个月余"入院。术前MRI考虑为来源不清的盆腔巨大实性占位(115 mm×105 mm×85 mm),经直肠穿刺诊断为梭形细胞来源的肿瘤。行盆腔肿瘤切除+膀胱前列腺腺切除+盆腔淋巴结清扫术+Bricker术。术后病理提示为前列腺原发胃肠道外间质瘤[CD117(+);Dog1(+);CD34(+);PSA(+);AR(+);P504s(+);Ki-67(2%)]。术后肿瘤组织全外显子测序提示为C-Kit基因(Exon 11 p.Q556-V560del)存在明显临床意义突变,筛选靶向药物甲磺酸伊马替尼+比卡鲁胺(PSA平稳后停用)口服,术后随访18个月无肿瘤复发及不良并发症。 结论前列腺原发胃肠道外间质瘤罕见,需与前列腺其他良恶性肿瘤相鉴别诊断。全外显子测序了解其发病高危基因,同时筛选药物辅助治疗可使患者生存获益。  相似文献   
6.
7.
In clinical therapy, the poor prognosis of hepatocellular carcinoma (HCC) is mainly attributed to the failure of chemotherapeutical agents to accumulate in tumor as well as lack of potency of tumor penetration. In this work, we developed actively tumor-targeting micelles with pH-sensitive linker as a novel nanocarrier for HCC therapy. These micelles comprised biodegradable poly(ethylene glycol)-poly(aspartate) polymers, in which paclitaxel can be covalently conjugated to pAsp via an acid-labile acetal bond to form pH-responsive structures. In vitro drug release studies showed that these structures were stable in physiological condition, whereas collapsed once internalized into cells due to the mildly acidic environment in endo/lysosomes, resulting in facilitated intracellular paclitaxel release. In addition, dehydroascorbic acid and guanidinopropyl methacrylamide polymers were decorated on the surface of micelles to achieve specific tumor accumulation and tumor penetration. Cellular uptake and in vivo imaging studies proved that these micelles had remarkable targeting property toward hepatocarcinoma cells and tumor. Enhanced anti-HCC efficacy of the micelles was also confirmed both in vitro and in vivo. Therefore, this micellar system may be a potential platform of chemotherapeutics delivery for HCC therapy.  相似文献   
8.
Two new saponins, notoginsenosides Ng1 (1) and Ng2 (2), together with seven known compounds (3–9), were isolated from the leaves of Panax notoginseng. Their structures were elucidated by UV, IR, HRESIMS, and NMR experiments. Compounds 6 and 7 showed moderate cytotoxic activities against HCT-116, with IC50 values of 4.98 and 0.64 μmol/L, respectively.  相似文献   
9.
Liu  Yaofu  Li  Huiling  Dong  Jianyi  Ma  Lei  Liao  Aijun  Rong  Zhuona  Zhou  Zhi  Cao  Liang  Wang  Fujin  Wang  Jingyu  Wang  Aiguo 《Clinical and experimental medicine》2019,19(1):121-132
Clinical and Experimental Medicine - Deficiency of γ-glutamyl carboxylation of coagulation factors, as evidenced by the elevated level of Des-γ-carboxyl prothrombin (DCP), is a common...  相似文献   
10.
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