全文获取类型
收费全文 | 238547篇 |
免费 | 20702篇 |
国内免费 | 14179篇 |
学科分类
医药卫生 | 273428篇 |
出版年
2024年 | 452篇 |
2023年 | 3086篇 |
2022年 | 5470篇 |
2021年 | 11249篇 |
2020年 | 8305篇 |
2019年 | 7536篇 |
2018年 | 7981篇 |
2017年 | 6965篇 |
2016年 | 6651篇 |
2015年 | 10081篇 |
2014年 | 12694篇 |
2013年 | 11886篇 |
2012年 | 17544篇 |
2011年 | 19220篇 |
2010年 | 11732篇 |
2009年 | 9410篇 |
2008年 | 12771篇 |
2007年 | 12800篇 |
2006年 | 12364篇 |
2005年 | 12446篇 |
2004年 | 8604篇 |
2003年 | 7648篇 |
2002年 | 6615篇 |
2001年 | 5995篇 |
2000年 | 6111篇 |
1999年 | 6412篇 |
1998年 | 3712篇 |
1997年 | 3731篇 |
1996年 | 2874篇 |
1995年 | 2638篇 |
1994年 | 2281篇 |
1993年 | 1540篇 |
1992年 | 2309篇 |
1991年 | 2016篇 |
1990年 | 1673篇 |
1989年 | 1490篇 |
1988年 | 1292篇 |
1987年 | 1188篇 |
1986年 | 951篇 |
1985年 | 778篇 |
1984年 | 512篇 |
1983年 | 399篇 |
1982年 | 240篇 |
1981年 | 218篇 |
1980年 | 200篇 |
1979年 | 247篇 |
1978年 | 147篇 |
1977年 | 120篇 |
1976年 | 106篇 |
1974年 | 116篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
用20个成人尸体心脏,从右心耳上缘平面向下作1.0cm厚的连续横断断层切片。对心脏每一断层下断面,进行各项观测,同时还观察了心脏各断层与胸壁的对应关系。 相似文献
992.
Effect of Salvia miltiorrhiza on the left ventricular diastolic function in coronary artery stenosis
In 24 open-chest mongrel dogs, coronary artery critical stenosis were produced by a micrometer constriction on left circumflex coronary artery. It was reduction about 87% in lumen area. CBF, -Vce, -dp/dt max were decreased, T was increased (P less than 0.01). 15 minutes after stenosis, the Salvia miltiorrhiza injection was injected into left atrium. CBF, -dp/dt max, -Vce were increased and T was decreased after the injection of Salvia miltiorrhiza. Moreover, the change of CBF was the earliest. The results proved that the Salvia miltiorrhiza could improve the left ventricular diastolic function in coronary artery stenosis. 相似文献
993.
The effect of rapamycin (RAPA) on both host-versus-graft (HVG) and graft-versus-host (GVH) immune responses was examined in small bowel transplant models using strongly histoincompatible donor-recipient combinations. Normal Wistar Furth (WFu; RT-1u) recipients rejected Buffalo (BUF; RT-1b) small bowel allografts within a mean survival time (MST) of 10.5 +/- 0.5 days. Administration of RAPA (0.8 mg/kg) by continuous intravenous infusion for 14 days via an osmotic pump prolonged graft survival to 25.0 +/- 4.6 days (P = 0.01). In a second strain combination, the 12.5 +/- 2.2 day survival of Brown Norway (BN; RT-1n) small bowel allografts in Lewis (RT-1l) recipients was prolonged to 21.6 +/- 2.0 and 28.5 +/- 2.8 days by 14 days of i.v. RAPA at doses of 0.8 and 1.6 mg/kg, respectively. In this model RAPA is five times more effective than cyclosporine, which at 4.0 mg/kg prolongs BN small bowel allografts in Lewis recipients to 21.6 +/- 6.3. To isolate HVG and GVH immune responses, (BN x Lewis)F1 hybrid rats served as the graft donor or host, respectively. In the HVG model, (BN x Lewis)F1 small bowel allografts, which were rejected by normal Lewis recipients at 12.2 +/- 3.6 days, were prolonged to 40.8 +/- 5.8 days (P = 0.001) by RAPA (0.8 mg/kg x 14 days). In the GVH model, the ability of Lewis small bowel allografts to produce severe GVH disease in untreated (BN x Lewis)F1 recipients at 12.3 +/- 2.8 days was delayed to 21.3 +/- 5.2 days by 0.8 mg/kg RAPA (P = 0.025). Thus, RAPA protects small bowel allografts more effectively against HVG than GVH immune responses. 相似文献
994.
乙型肝炎甲胎蛋白检测与重型肝炎预后指数评估的意义 总被引:1,自引:0,他引:1
给慢性活动肝炎患者输注人胎肝细胞悬液引起血清甲胎蛋白增高反应的初浓度为202±38.3μg/L,其半衰期为1.7天;分布池为6.9一10.2升。重型肝炎生存组血清甲胎蛋白显著高于死亡组,生存组甲胎蛋白与血清总胆红素呈非常显著相关,而死亡组两者无相关性。重型肝炎患者输注胎肝悬液后其血清甲胎蛋白进一步升高者,预后较好。取重型肝炎预后指数0.1为重型肝炎生死的截断点,判断预后的灵敏度、特异度、准确度和阳性预告值分别为79.5%、89.6%、84.8%和87.5%。重型肝炎预后指数的计算可作为判断预后与新疗法疗效的指标。 相似文献
995.
The relationship among the dosages of aminophylline, plasma levels of theophylline and variations of mean pulmonary arterial pressure (mPAP) in 72 patients with COPD was investigated. The results showed that after a different loading dosage of aminophylline (6 mg/kg, 5 mg/kg and 4 mg/kg) was administered by intravenous injection, mPAP in the 6 mg/kg group was decreased more significantly (P less than 0.01) than that in the 4 mg/kg group. In the 6 mg/kg group, the decreased mPAP period sustained for 120 min, which was longer than that in the other 2 groups. The plasma levels of theophylline in the 6 mg/kg group of patients 30 to 120 min after loading dose injected were 115.54-79.04 mumol/L, which were higher than that in the others. Within the 120 min period of observation after the drug was administered no patients in any of these groups showed severe untoward effects. According to the results of this experiment, we suggest that the 6 mg/kg as a loading dose should be advised for the treatment of pulmonary hypertension in COPD. The optimum time to give the maintenance dosage should be set within 2 h after the loading dose. It is necessary to monitor the plasma levels of theophylline while aminophylline is administered, so that optimal therapeutic effects could be achieved without side effects. 相似文献
996.
应用X衍射方法测定雷公藤两个化合物的晶体结构,并对影响固体熔点的结构因素进行分析。晶型(或空间对称群)、结晶溶剂、分子间作用力及分子构象的精细变化均可导致晶态物质的熔点变化。 相似文献
997.
乙酰胆碱参与皮层下行调制疼痛的作用 总被引:2,自引:2,他引:0
<正> 我们实验室的工作曾报导,刺激猫的皮层SⅡ区、SⅠ区或十字沟前区可抑制丘脑髓板内核群神经元的伤害性反应及针刺镇痛效应。相继刺激大鼠的皮层SmⅠ区也获 相似文献
998.
不同饮水类型的若干癌症发病率研究 总被引:8,自引:1,他引:7
应用回顾前瞻性方法,在海宁市随机选择了8个乡(镇)作为研究区。1977至1988年间,研究区共有癌症病例1988人。研究结果示,饮用池塘水的肝、肺、胃、食道及结直肠的癌症平均发病率男女均为最高;而饮用井水的上述5种癌症的平均发病率最低。在各饮水类型问对各种癌症的平均发病率作了Poisson检验,结果差异有统计学意义。将饮用井水作为非暴露,作相对危险度分析。表明饮用河水的RR值高达7.79~14.25;饮用池塘水的RR则更高(2.55~36.99)。本文揭示了不同饮水类型癌症发病率的差异及其联系。 相似文献
999.
以液体稀释法比较了自制与进口十六烷基吡啶作用于4种口腔常见微生物的最低抑菌浓度和最低杀菌浓度的实验结果,经t检验证明两者间无显著差异,提示自制氯化十六烷基吡啶的药效质量可靠。并就控制接种菌量及杀菌机理等问题作了初步探讨。 相似文献
1000.