收费全文 | 184822篇 |
免费 | 40828篇 |
国内免费 | 2476篇 |
耳鼻咽喉 | 5310篇 |
儿科学 | 5707篇 |
妇产科学 | 3912篇 |
基础医学 | 3752篇 |
口腔科学 | 6115篇 |
临床医学 | 41671篇 |
内科学 | 51342篇 |
皮肤病学 | 7846篇 |
神经病学 | 16998篇 |
特种医学 | 7155篇 |
外科学 | 43496篇 |
综合类 | 278篇 |
现状与发展 | 79篇 |
预防医学 | 15774篇 |
眼科学 | 4399篇 |
药学 | 1294篇 |
中国医学 | 10篇 |
肿瘤学 | 12988篇 |
2024年 | 977篇 |
2023年 | 6664篇 |
2022年 | 1368篇 |
2021年 | 3609篇 |
2020年 | 7392篇 |
2019年 | 2584篇 |
2018年 | 9587篇 |
2017年 | 9987篇 |
2016年 | 11027篇 |
2015年 | 11227篇 |
2014年 | 18628篇 |
2013年 | 20411篇 |
2012年 | 6422篇 |
2011年 | 6489篇 |
2010年 | 12204篇 |
2009年 | 16733篇 |
2008年 | 6774篇 |
2007年 | 4847篇 |
2006年 | 7593篇 |
2005年 | 4484篇 |
2004年 | 3554篇 |
2003年 | 2454篇 |
2002年 | 2489篇 |
2001年 | 4491篇 |
2000年 | 3395篇 |
1999年 | 3871篇 |
1998年 | 4505篇 |
1997年 | 4299篇 |
1996年 | 4252篇 |
1995年 | 3922篇 |
1994年 | 2529篇 |
1993年 | 2082篇 |
1992年 | 1795篇 |
1991年 | 1729篇 |
1990年 | 1382篇 |
1989年 | 1465篇 |
1988年 | 1285篇 |
1987年 | 1067篇 |
1986年 | 1077篇 |
1985年 | 886篇 |
1984年 | 702篇 |
1983年 | 690篇 |
1982年 | 634篇 |
1981年 | 516篇 |
1980年 | 420篇 |
1979年 | 336篇 |
1978年 | 381篇 |
1977年 | 457篇 |
1975年 | 316篇 |
1972年 | 344篇 |
Methods: Male Sprague Dawley rats were chronically implanted with lumbar intrathecal catheters. The tail-flick test was used to assess the thermal nociceptive threshold. The ability of intrathecal tizanidine, clonidine, lidocaine, or the combinations of alpha2 -adrenergic agonist and lidocaine to alter the tail-flick latency was examined. To characterize the antinociceptive interaction, the isobolographic analysis was applied. Additionally, the motor function, blood pressure and heart rate after intrathecal administration of drugs and combinations were also monitored.
Results: Intrathecal tizanidine, clonidine, or the combinations increased the tail-flick latency in dose- and time-dependent fashion without affecting motor function. The order potencies (dose producing a 50% of peak effect, in micro gram) of tizanidine and clonidine were 1.8 and 0.75, respectively. With isobolographic analysis, tizanidine with lidocaine and clonidine with lidocaine showed significantly synergistic antinociceptive interaction. Potency ratio analysis and fractional analysis also confirmed the synergistic interaction. At the doses in the combinations showing comparable antinociception, tizanidine with lidocaine, unlike clonidine with lidocaine, did not affect motor function or blood pressure. 相似文献
Methods: Six healthy volunteers were anesthetized with desflurane and nitrous oxide. The cooling methods were 1) circulating water (5 [degree sign] Celsius, full-length mattress and cover), 2) forced air (10 [degree sign] Celsius, full-length cover), 3) gastric lavage (500 ml iced water every 10 min), 4) bladder lavage (300 ml iced Ringer's solution every 10 min), and 5) ice-water immersion. Each method was applied for 40 min or until the volunteers' core temperatures approached 34 [degree sign] Celsius. The volunteers were rewarmed to normothermia between treatments. Core cooling rates were evaluated using linear regression.
Results: The first volunteer developed abdominal cramping and diarrhea after gastric lavage. Consequently, the technique was not again attempted. Bladder lavage increased heat loss 10 [nearly =] 10 W and decreased core temperature 0.8 +/- 0.3 [degree sign] Celsius/h (r2 = 0.99 +/- 0.002; means +/- SD). Forced-air and circulating-water cooling comparably increased heat flux, [nearly =] 170 W. Consequently, core cooling rates were similar during the two treatments at 1.7 +/- 0.5 [degree sign] Celsius/h (r2 = 0.99 +/- 0.001) and 1.6 +/- 1.1 [degree sign] Celsius/h (r2 = 0.98 +/- 0.02), respectively. Immersion in an ice water slurry increased heat loss [nearly =] 600-800 W and decreased core temperature 9.7 +/- 4.4 [degree sign] Celsius/h (r sup 2 = 0.98 +/- 0.01). Immersion cooling was associated with an afterdrop of [nearly =] 2 [degree sign] Celsius. 相似文献
Methods: The INa was recorded using the whole-cell configuration of the patch-clamp technique. Currents were generated from resting VH s of -110, -80, or -65 mV. State-dependent block was characterized by monitoring frequency dependence, tonic block, and removal of inactivation by veratridine.
Results: Halothane produced significant (P < 0.05) VH -dependent depressions of peak INa (mean +/- SEM): 24.4 +/- 4.1% (VH = -110 mV), 42.1 +/- 3.4% (VH = -80 mV), and 75.2 +/- 1.5% (VH = -65 mV). Recovery from inactivation was significantly increased when cells were held at -80 mV (control, tau = 6.0 +/- 0.3 ms; halothane, tau = 7.1 +/- 0.4 ms), but not at -110 mV. When using a VH of -80 mV, halothane exhibited a use-dependent block, with block of INa increasing from 8.6 +/- 1.4% to 30.7 +/- 3.5% at test pulse rates of 2 and 11 Hz, respectively. Use-dependent inhibition was not apparent at VH of -110 mV. When inactivation of INa was removed by exposure to 100 micro Meter veratridine, no significant difference was observed in the depressant effect of halothane at both VH s: 26.6 +/- 4.5% (VH = -80 mV) and 26.4 +/- 5.6% (VH = -110 mV). 相似文献