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   7827篇
  免费   932篇
  国内免费   469篇
耳鼻咽喉   42篇
儿科学   91篇
妇产科学   105篇
基础医学   776篇
口腔科学   113篇
临床医学   987篇
内科学   1143篇
皮肤病学   66篇
神经病学   269篇
特种医学   385篇
外国民族医学   1篇
外科学   643篇
综合类   1560篇
一般理论   4篇
预防医学   742篇
眼科学   176篇
药学   842篇
  7篇
中国医学   700篇
肿瘤学   576篇
  2024年   49篇
  2023年   173篇
  2022年   467篇
  2021年   542篇
  2020年   413篇
  2019年   297篇
  2018年   338篇
  2017年   313篇
  2016年   266篇
  2015年   388篇
  2014年   463篇
  2013年   461篇
  2012年   648篇
  2011年   626篇
  2010年   403篇
  2009年   349篇
  2008年   411篇
  2007年   428篇
  2006年   277篇
  2005年   298篇
  2004年   205篇
  2003年   192篇
  2002年   166篇
  2001年   134篇
  2000年   99篇
  1999年   109篇
  1998年   82篇
  1997年   78篇
  1996年   71篇
  1995年   50篇
  1994年   45篇
  1993年   30篇
  1992年   42篇
  1991年   35篇
  1990年   18篇
  1989年   25篇
  1988年   36篇
  1987年   16篇
  1986年   28篇
  1985年   11篇
  1984年   8篇
  1983年   13篇
  1982年   11篇
  1980年   9篇
  1979年   7篇
  1976年   9篇
  1841年   7篇
  1840年   13篇
  1838年   8篇
  1830年   5篇
排序方式: 共有9228条查询结果,搜索用时 15 毫秒
991.

Purpose

To determine characteristic magnetic resonance (MR) imaging features of solitary necrotic nodule of the liver.

Materials and methods

MR images features of thirty-two patients (17 men, 15 women; mean age, 43 years; range, 24–76 years) with pathologically proved solitary necrotic nodule of the liver were retrospectively analyzed for number, size, signal intensity features and enhancement patterns.

Results

A total of 33 lesions were identified. The mean diameter was 2.3 cm (range 1.0–4.5 cm). Thirty lesions (90.9%) were 1.0–3.0 cm in diameter and only 3 lesions (9.1%) were larger than 3.0 cm. On T1-weighted images, solitary necrotic nodule of the liver appeared hypointense in 31 lesions (93.9%) and isointense in 2 lesions (6.1%). On T2-weighted images, 12 (36.4%) lesions were hyperintense, 15 (45.4%) were isointense or invisible and 6 (18.2%) were hypointense. After injection of gadopentetate dimeglumine, all lesions were hypointense and none of them showed enhancement.

Conclusion

Solitary necrotic nodule of the liver is usually small with the size not exceed 3.0 cm in diameter. Absence of enhancement on all dynamic phase after gadopentetate dimeglumine administration may be most characteristic feature of solitary necrotic nodule of the liver on MR images, which may help discriminate this entity from metastatic liver tumors and intrahepatic cholangiocarcinoma.  相似文献   
992.

Purpose

To evaluate the feasibility and therapeutic efficacy of 1.5 T conventional MR-guided percutaneous interstitial implantation of I-125 radioactive seeds in patients with hepatocellular carcinoma (HCC).

Materials and methods

The institutional ethics committee approved this study. After imformed consent was obtained, twenty-three patients suffering from a total of 65 HCC lesions were treated with I-125 seed permanent interstitial implantation under the guidance of a 1.5 T conventional magnetic resonance imaging (MRI) system. The FSE T2WI, T1 FSPGR, FIESTA 2D, 3D Dyn T1WI sequences were used to guide an 18G MR-compatible needle inserted into the lesions to introduce the I-125 seeds. The response evaluation criteria in solid tumors (RECIST) were used to evaluate the curative effect.

Results

The needle and I-125 seed were seen clearly on MRI images. The final dose delivered to total decay was 173.46 ± 32.44 Gy (range, 110–270 Gy) as calculated by postoperative TPS. The complete response (CR) was seen in 22 lesions (33.8%), partial response (PR) in 24 lesions (36.9%), stable disease (SD) in 9 lesions (13.8%), and progressive disease (PD) in 10 lesions (15.4%). The post-operative alpha-fetoprotein (AFP) was decreased (t = 3.117, P = 0.005 < 0.05). Two patients were observed a small area of subcapsular bleeding that did not lead to any symptoms or clinical sequelae.

Conclusion

MR-guided I-125 implantation for HCC is technically feasible and effective.  相似文献   
993.
目的:观察陈旧性膝关节运动损伤股四头肌随意动员能力的变化。方法:60名天津体育学院学生,自愿参加测试,根据其是否有陈旧性膝关节运动损伤分为2组,损伤组(有训练史)30人,对照组(无训练史)30人。应用股四头肌随意动员能力评定系统测定分析股四头肌最大随意等长肌力(MVC)、随意动员能力(MA)和力量上升速率(RFD)。结果:对照组两侧股四头肌MVC、MA和RFD无显著差异(P>0.05),损伤组两侧股四头肌MVC无显著性差异(P>0.05)。对照组右侧股四头肌MVC、RFD值显著低于损伤组未损伤侧(P<0.05,P<0.01),损伤组膝关节损伤侧MA、RFD值显著低于未损伤侧(P<0.05,P<0.01)。结论:即使陈旧性膝关节运动损伤者股四头肌肌肉力量已恢复到未损伤侧水平,其随意动员能力和力量上升速率依然较低,膝关节神经肌肉控制仍较差,这可能是影响陈旧性膝关节运动损伤功能状态的主要因素之一。股四头肌随意动员能力评价系统可检测这一变化。  相似文献   
994.
目的 观察生物人工材料(biological artificial material,BAM)人工骨修复下肢负重骨骨缺损的临床效果. 方法 选择2008年1月- 2010年12月收治的采用BAM人工骨进行手术植入修复骨缺损的32例下肢负重骨骨缺损患者,年龄21 ~ 77岁,平均32.5岁.骨缺损体积为1.0 cm×2.0 cm×2.5 cm~3.0 cm×3.5 cm ×5.0 cm,平均15.4 cm3.骨缺损病因主要为粉碎性骨折、骨囊肿、骨纤维结构不良、慢性骨髓炎等.术后即刻及术后1,2,3,5,7,9,12,18个月进行随访,观察术后全身及切口局部反应、血钙/磷改变情况、骨缺损修复及患肢负重功能恢复情况. 结果 所有患者均得到有效随访9 ~18个月,平均10.5个月.术后至末次随访所有患者均无局部或全身移植物排斥反应.随访X线片示术后3个月BAM人工骨植入区与骨缺损周围的骨组织之间界限模糊,有新生骨形成;术后6个月BAM人工骨植入区明显有新骨长入,人工骨材料与骨组织融为一体,骨缺损已基本修复.术后患肢完全负重时间为术后2.5 ~4个月,平均3.2个月. 结论 BAM人工骨具有良好的生物相容性和骨诱导作用,其内结构可以保持一定的刚度和强度,可用于下肢负重骨骨缺损的修复.  相似文献   
995.
目的观察高功率微波辐射(high power microwave radiation,HPM)对小鼠心肌氧化应激及ATPase活性的影响。方法雄性ICR小鼠32只,随机分为4组(n=8):假照组、微波辐射10 min组、微波辐射20 min组、微波辐射30 min组。采用S波段,平均表面功率为10 mW/cm2微波;照射时间分别为0,10,20,30 min/次,每周2次,共2周。末次辐射完毕,立即处死小鼠,取心脏、冰冷生理盐水冲洗后,加入匀浆液制作匀浆。采用试剂盒测定超氧化物歧化酶(SOD)活性、谷胱甘肽过氧化物酶(GSH-px)活性、总抗氧化能力(T-AOC)、谷胱甘肽(GSH)及丙二醛(MDA)的含量以及Na+K+-ATPase和Ca2+Mg2+-AT-Pase活性。结果微波辐射后,与假照组比,微波辐射20 min组和微波辐射30 min组SOD活性降低(P<0.05)、GSH-px活性增加(P<0.05);而微波辐射20 min组GSH含量明显增加(P<0.01);微波辐射30 min组Ca2+Mg2+-ATPase活性明显降低(P<0.01),其他指标变化无明显统计学差异。结论微波辐射可能引起小鼠心脏氧化应激平衡状态以及Ca2+转运的改变。  相似文献   
996.
Bai J  Li C  Wang S  Liu J  Ye Z  Yu X  Xi Q  Ni M  He D 《BJU international》2012,109(8):1230-1234
Study Type – Therapy (case series) Level of Evidence 4 What's known on the subject? and What does the study add? The literature scarcely reports subcapsular renal haematoma (SRH) after lithotripsy techniques. We reported the incidence, associated risk factors, possible pathogenesis, precautions, and outcomes of SRH after ureteroscopic lithotripsy (URSL).

OBJECTIVE

  • ? To report the incidence, risk factors, and outcomes of subcapsular renal haematoma (SRH) after ureteroscopic lithotripsy (URSL) using holmium:yttrium‐aluminum‐garnet (Ho:YAG) laser to treat ureteric stones.

PATIENTS AND METHODS

  • ? Prospective data from 2848 URSLs performed between January 2003 and September 2010 were retrospectively analysed.
  • ? In all 11 patients were identified as having a SRH after URSL if they had persistent severe ipsilateral flank pain or a palpable mass within a day of surgery, or presented with radiographic evidence of a SRH.
  • ? Risk factors for the development and course of the SRH were reported.

RESULTS

  • ? Of the 2848 consecutive patients treated with URSL using Ho:YAG laser, 11 (0.4%) developed a SRH after surgery.
  • ? Patients who developed a SRH had larger stones (1.4 vs 0.9 cm, P < 0.001), more severe ipsilateral hydronephrosis (P < 0.001), longer operation duration (41 vs 33 min, P < 0.001), and higher perfusion pressure of hydraulic irrigation (176.8 vs 170.2 mmHg, P < 0.001) than patients who did not develop a SRH.
  • ? Patient age, sex, body mass index, presence of diabetes mellitus, history of urolithiasis and hypertension, presence of multiple stones, stone location and flow rate of hydraulic irrigation were not statistically different in patients who did or did not develop a SRH.
  • ? Most patients were managed conservatively, with no further intervention or with a flank drain, until the SRH resolved. Overall, in three patients the SRH resolved with no further intervention, six patients were treated with a drain only, and two patients had open surgery within a day of presenting with SRH.

CONCLUSIONS

  • ? The rate of development of SRH after URSL is very low.
  • ? Most patients who present with a SRH after URSL, can be treated conservatively with no intervention or with a drain only.
  相似文献   
997.
Research questionMultiple morphological abnormalities of the flagella (MMAF) is characterized by excessive immotile spermatozoa with severe flagellar abnormalities in the ejaculate. Previous studies have reported a heterogeneous genetic profile associated with MMAF. What other genetic variants might explain the cause of MMAF?DesignWhole-exome sequencing was conducted in a cohort of 90 Chinese patients with MMAF. The pathogenicity of identified mutations was assessed through electron microscopy and immunofluorescent examinations.ResultsThree unrelated men with bi-allelic DNAH2 variants were identified. Sanger sequencing verified that the six novel variants originated from every parent. All these variants were located at the conserved domains of DNAH2 and predicted to be deleterious by bioinformatic tools. Haematoxylin and eosin staining and scanning electron microscopy revealed that spermatozoa harbouring DNAH2 variants displayed severely aberrant morphology mainly with absent and short flagella (≥78%). Moreover, transmission electron microscopy revealed the obvious absence of a central pair of microtubules and inner dynein arms in the spermatozoa with mutated DNAH2. Immunofluorescence data further validated these findings, showing reduced DNAH2 protein expression in the spermatozoa with DNAH2 variants, compared with normal spermatozoa. Intracytoplasmic sperm injection using spermatozoa from the three men with mutated DNAH2 resulted in blastocyst formation in all cases. Embryo transfer was carried out in two couples, both resulting in clinical pregnancy.ConclusionsThese experimental and clinical data suggest that bi-allelic DNAH2 variants might induce MMAF-associated asthenoteratozoospermia, which can be overcome through intracytoplasmic sperm injection. These findings contribute to the knowledge of the genetic landscape of asthenoteratozoospermia and clinical counselling of male infertility.  相似文献   
998.
目的 观察X射线照射后小鼠胸腺细胞中CD4+ CD25+ NRP1+ Treg细胞数量及TGF-β1分泌量的变化,并探索PLC/ PIP2信号通路在其中的作用机制.方法 36只ICR小鼠按随机数字表法分为假照组、0.5、1.0、2.0、4.0和6.0 Gy的不同剂量组,X射线深部治疗机进行全身照射,于照射后16 h应用流式细胞仪分析小鼠胸腺细胞中CD4+ CD25+ NRP1+ Treg细胞的变化,ELISA法检测胸腺细胞TGF-β1含量的变化.EL-4细胞株经PKC激动剂(PMA)、Ca2+阻断剂(TMB-8)作用2h后并经4 GyX射线照射,于照射后48 h应用流式细胞术及ELISA法分别检测CD4+CD25+ NRP1+ Treg细胞及TGF-β1含量的变化.结果 小鼠胸腺细胞中NRP1+ Treg在0.5 GyX射线作用后稍有下降,于1.0 Gy降至最低(t=6.96,P<0.01),而后呈剂量依赖性升高,于6.0 Gy升至最高(t =6.70,P<0.01);胸腺细胞TGF-β1在0.5 GyX射线照射后显著下降(t=12.53,P<0.01),而1.0~4.0 Gy照射后则呈剂量依赖性升高,于6.0 Gy仍保持高水平(t=10.40 ~ 15.30,P<0.01).PMA作用后,与假照组相比,单独PMA组NRP1+ Treg细胞表达显著降低(t=3.06,P<0.01),而联合照射后表达则明显上调(t=8.27,P<0.01),TGF-β1无论受照与否,其含量均明显降低(t=10.46 ~39.69,P<0.01);而TMB-8作用后,无论受照与否CD4+ CD25+ NRP1+ Treg的表达及TGF-β1的分泌量均显著上调(t=5.53~44.26,P<0.01).结论 高剂量电离辐射可以诱导小鼠胸腺细胞中NRP1+ Treg细胞表达并增加TGF-β1的含量,此现象可能与启动PLC/PIP2信号通路有关.  相似文献   
999.
1000.
The phylum Apicomplexa comprises intracellular protozoa that include many human pathogens. Their nearest relatives are chromerids and colpodellids. We report a case of a Babesia spp.-like relapsing infection caused by a newly described microorganism related to the Apicomplexa. This case is highly suggestive of a previously undescribed type of colpodellid that infects vertebrates.  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