全文获取类型
收费全文 | 37372篇 |
免费 | 4323篇 |
国内免费 | 2928篇 |
学科分类
医药卫生 | 44623篇 |
出版年
2024年 | 139篇 |
2023年 | 766篇 |
2022年 | 1373篇 |
2021年 | 2386篇 |
2020年 | 1898篇 |
2019年 | 1421篇 |
2018年 | 1459篇 |
2017年 | 1438篇 |
2016年 | 1276篇 |
2015年 | 1955篇 |
2014年 | 2316篇 |
2013年 | 2408篇 |
2012年 | 3208篇 |
2011年 | 3487篇 |
2010年 | 2521篇 |
2009年 | 2043篇 |
2008年 | 2246篇 |
2007年 | 2201篇 |
2006年 | 1936篇 |
2005年 | 1784篇 |
2004年 | 1165篇 |
2003年 | 964篇 |
2002年 | 819篇 |
2001年 | 626篇 |
2000年 | 564篇 |
1999年 | 526篇 |
1998年 | 256篇 |
1997年 | 260篇 |
1996年 | 214篇 |
1995年 | 187篇 |
1994年 | 158篇 |
1993年 | 81篇 |
1992年 | 94篇 |
1991年 | 86篇 |
1990年 | 83篇 |
1989年 | 58篇 |
1988年 | 54篇 |
1987年 | 35篇 |
1986年 | 27篇 |
1985年 | 11篇 |
1984年 | 17篇 |
1982年 | 11篇 |
1981年 | 10篇 |
1979年 | 6篇 |
1978年 | 11篇 |
1977年 | 5篇 |
1975年 | 4篇 |
1974年 | 4篇 |
1973年 | 4篇 |
1972年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
61.
目的:根据流体动力学平衡控释原理(HBS)研制了马来酸罗列酮胃漂浮型缓释片。方法;以体外释放度和漂浮情况为筛选指标,采用单因素考察和正交试验设计相结合, 对胃漂浮缓释片的处方、制备工艺及体外释放条件进行优化筛选;采用γ闪烁照相技术对优化处方的内漂浮情况进行胃内动态观察。结果:马来酸罗格列酮胃漂浮缓释片在释放介质中迅速起漂,持漂时间超过12h,12h达最大累积释放;初步确定在胃内滞留时间达3h以上。结论:优化处方的释放过程符合Higuchi方程,释放机制为异常扩散;胃漂浮片在胃滞时间明显长于普通片。 相似文献
62.
63.
目的:研究治疗前列腺增生的α1-受体拮抗剂SL-89.0519-08的合成路线。方法:以5-氯-2-甲氧基苯胺为原料,经环合,烃化,脱保护基和亲核取代等步骤,合成了目标化合物,同时对原料合成工艺进行了摸索。结果:合成的目标化合物经IR,^1HMNR,EI-MS和HRMS得以确证。结论:该合成工艺和路线适宜工业化生产。 相似文献
64.
目的 观察尼卡地平对脑缺血后海马CA1锥体神经元的影响。方法 30只沙土鼠随机分成假手术组 (Ⅰ组 ,n =10 )、缺血组 (Ⅱ组 ,n =10 )和尼卡地平处理组 (Ⅲ组 ,n =10 )。Ⅰ组只进行手术操作 ,不行脑缺血 ;Ⅱ组阻断双侧颈总动脉 15min造成前脑缺血模型 ;Ⅲ组在脑缺血前 30min腹腔注射尼卡地平 2mg/kg体重。 3d后取出动物脑组织 ,HE染色计数海马CA1区 1mm长度内正常锥体细胞数。结果 与Ⅰ组相比 ,Ⅱ组和Ⅲ组正常锥体细胞数明显减少 (P <0 .0 1) ;Ⅱ组的正常锥体细胞数少于Ⅲ组 (P <0 .0 1)。结论 尼卡地平能减轻脑缺血后脑细胞损伤。 相似文献
65.
目的:探讨腹腔镜在腹股沟疝修补手术中的优缺点,方法:31例腹股沟疝行腹腔镜疝修补术,其中斜疝25例,直疝6例,复发疝4例,均行腹腔内术式(TAPP)。结果:手术全部完成,平均手术时间61min(40-95min),无中转手术,4例同时行胆囊切除术,平均住院7.5d,术后近期随访无复发,结论:腹腔镜疝修补术是一种安全的手术,术后恢复时间短,复发率低。 相似文献
66.
目的探讨NO合成底物左旋-精氨酸(L-Arg)对兔局灶脑缺血后血管再生和脑细胞凋亡的影响。方法兔局灶脑缺血后应用L-Arg,流式细胞仪定量分析细胞凋亡率的变化,CD34免疫组织化学测脑组织微血管密度(MVD),脑组织含水率评价脑水肿。结果与对照组比较,L-Arg组脑细胞凋亡率明显减少(8.72±2.62 vs 16.62±2.82,P<0.01),同时脑组织MVD却明显增加(1.21±0.43 vs 0.69±0.22,P<0.01)。结论外源性L-Arg可减少缺血后脑细胞凋亡并促进缺血后血管再生,对局灶脑缺血具有重要的神经保护作用。 相似文献
67.
BACKGROUND: As a non-invasive technique which can provide comprehensive biological information, 1H-magnetic resonance spectroscopy (1H-MRS) may provide valuable reference data for irreversible recovery or reversible changes in ischemic tissue after stroke.
OBJECTIVE: To monitor and evaluate the effect of the urokinase thrombolytic therapy after experimental acute cerebral ischemia by 1H-MRS technology and investigate its adaptability.
DESIGN: Randomly controlled animal study.
SETTINGS: Shenzhen Hospital of Peking University and National Key Laboratory of Pattern and Atom & Molecular Physics, Wuhan Physics and Mathematics Institute, Chinese Academy of Science.
MATERIALS: Eleven healthy adult Sprague-Dawley (SD) rats, weighing 260–300 g and of both genders, were supplied by Experimental Animal Center of Tongji Medical Collage, Huazhong University of Science and Technology [SCXK (e) 2004-007]. 4.7T superconducting nuclear magnetic resonance meter was provided by Brucker Company.
METHODS: The experiment was carried out in Shenzhen Hospital of Peking University and National Key Laboratory of Pattern and Atom & Molecular Physics, Wuhan Physics and Mathematics Institute, Chinese Academy of Science from August 2003 to December 2005. ① The rats were randomly divided into 30-minute self-thrombo-embolism group (n =6) and 60-minute self-thrombo-embolism group (n =5). Six rats in 30-minute self-thrombo-embolism group were occluded with clot embolus for 30 minutes and 5 rats in 60-minute self-thrombo-embolism group were occluded for 60 minutes. 10 000 U/kg urokinase was dissolved in 2 mL saline and the operation lasted for 5 minutes. ② 1H-MRS was performed before thrombolysis and at 3 hours and 24 hours after successful embolization. The metabolic changes of N-acetyl-L-aspartic acid (NAA)/phosphocreatine (PCr) + creatine (Cr), choline phosphate (Cho)/PCr+Cr and lactic acid (Lac)/PCr+Cr in the region of interests were analyzed. ③ The T2W image was conducted 24 hours after the thrombolytic therapy with TR=500 ms and TE=25 ms. ④ The subjects were sacrificed immediately after 1H-MRS and the brain tissues were cut into pieces and stained with HE method; in addition, pathological changes were observed under optic microscope.
MAIN OUTCOME MEASURES: ① Metabolic changes of NAA/PCr+Cr, Cho/PCr+Cr and Lac/PCr+Cr in the region of interests; ② T2W image at 24 hours after the thrombolysis; ③ pathological observation of brain tissue.
RESULTS: Eleven rats were all involved in the final analysis. ① Metabolic changes in the region of interests : In 30-minute self-thrombo-embolism group, the Lac peak emerged immediately after the embolism, but the ischemic zone decreased 3 hours after the thrombolytic therapy (0.252±0.01, 0.603±0.01, P < 0.01). Lac/(PCr+Cr) ratio was 0.290±0.01 at 24 hours after thrombolysis, which was higher than that at 3 hours after thrombolysis (P < 0.01). The NAA/ (PCr+Cr) ratio decreased significantly at 3 hours after the thrombolysis as compared with that before thrombolysis (0.922±0.16, 1.196±0.01, P < 0.05). In 60-minute self-thrombo-embolism group, the Lac/(PCr+Cr) ratio was higher at 3 hours after thrombolysis than that before thrombolysis (0.846±0.12, 0.601±0.11, P < 0.05) and the NAA/(PCr+Cr) decreased at 3 hours after the embolism. Fluctuation of NAA/ (PCr+Cr) ranged from 0.68 to 0.75 before thrombolysis and from 0.71 to 0.75 at 3 hours after thrombolysis. ② T2W image: T2W image showed that 2 subjects in 30-minute self-thrombo-embolism group whose Lac/NAA was higher than 0.7 suffered from intracranial hemorrhage. This meant that the subjects with Lac/NAA > 0.7 were more likely to suffer from intracranial hemorrhage. ③ Histological and morphological examinations: Optic microscope demonstrated that interspace surrounding nerve cells was widened at ischemic center; neurons were swelling; nucleus was stained lightly; pyknosis and mesenchymal edema were mainly observed in lateral cortex of brow and vertex and in lateral part of corpus striatum.
CONCLUSION: ①Compound parameters in ischemic area before thrombolysis should be regarded as an important predicting marker for thrombolytic therapy, effect evaluation and termination. ② 1H-MRS combining with other imaging technique is a detecting way for screening cases who are suitable for thrombolytic therapy. 相似文献
68.
桂林市传染病网络直报工作第一年效果分析 总被引:4,自引:2,他引:2
目的观察传染病网络直报系统启动一年来的传染病监测质量,探讨网络直报评价方法.方法描述研究网络直报工作效果.结果实行网络直报后,传染病从临床医生发现到疾病预防控制机构接到报告的平均时间由5.48 d缩短至1.67 d,报卡数量增加20.84%,21.03%的报告卡得到校正,网络直报覆盖率县辖区医院为96.55%,市城区为69.23%,79.21%的直报单位有专用电脑.结论网络直报的启用及其系统的建立,提高了桂林市传染病疫情报告的质量和水平,同时应尽快建立与之相应的疫情报告管理方法和标准. 相似文献
69.
108例支气管哮喘患者舌脉象特征分析 总被引:1,自引:0,他引:1
目的:探讨对支气管哮喘临床辨证有意义的舌脉象客观指标,以辅助临床诊断。方法:应用TP—I型中医舌脉象数字化分析仪检测108例患者舌脉象参数,分析支气管哮喘发作期与缓解期的舌脉象特征。结果:108例支气管哮喘患者的舌象中,舌色以淡红舌、淡紫舌多见,舌苔以白苔、黄苔、薄苔为多见;脉象以弦脉、滑脉、弦滑脉为多见;舌脉象参数中舌色指数、苔色指数、厚苔指数、胖瘦指数在哮喘发作期各证型中有显著性差异(P〈0.05);RPSR1、RPSR3、RPSR4、RBF、RLMS2、PLMP2、RLMS3、RLMP3在哮喘发作期与缓解期有显著性差异(P〈0.05)。结论:支气管哮喘患者的脉象参数、舌色指数、苔色指数、厚苔指数、胖瘦指数、RPSR1、RPSR3、RPSR4、RBF、RLMS2、PLMP2、RLMS3、RLMP3对其辨证分型有重要参考价值。 相似文献
70.
目的:制备银杏内酯B(GB)柔性纳米脂质体,并对其体外透皮规律进行研究。方法:采用薄膜分散法制备银杏内酯B柔性纳米脂质体,并对其形态及粒径大小进行分析;采用改良的 Franz 扩散池进行体外透皮吸收试验,比较银杏内酯B醇溶液、银杏内酯B柔性纳米脂质体及普通银杏内酯B纳米脂质体的经皮累积渗透量及渗透速率。结果:此方法制得的脂质体平均包封率为(89.52±1.76)%,平均粒径为(208.3±25.49) nm,Zata电位为-49.2 mV。柔性纳米脂质体8 h的累积透过量为189.97 μg·cm-2,8 h的渗透速率为23.75 μg·cm-2·h-1。结论:柔性纳米脂质体包封率较高,稳定性良好,可显著促进银杏内酯B的透皮吸收。 相似文献