收费全文 | 10149篇 |
免费 | 1057篇 |
国内免费 | 66篇 |
耳鼻咽喉 | 122篇 |
儿科学 | 354篇 |
妇产科学 | 195篇 |
基础医学 | 1081篇 |
口腔科学 | 228篇 |
临床医学 | 1066篇 |
内科学 | 1989篇 |
皮肤病学 | 144篇 |
神经病学 | 814篇 |
特种医学 | 568篇 |
外科学 | 2292篇 |
综合类 | 171篇 |
一般理论 | 1篇 |
预防医学 | 718篇 |
眼科学 | 136篇 |
药学 | 547篇 |
1篇 | |
中国医学 | 12篇 |
肿瘤学 | 833篇 |
2023年 | 59篇 |
2022年 | 70篇 |
2021年 | 224篇 |
2020年 | 121篇 |
2019年 | 130篇 |
2018年 | 214篇 |
2017年 | 204篇 |
2016年 | 227篇 |
2015年 | 381篇 |
2014年 | 660篇 |
2013年 | 747篇 |
2012年 | 425篇 |
2011年 | 375篇 |
2010年 | 524篇 |
2009年 | 549篇 |
2008年 | 392篇 |
2007年 | 333篇 |
2006年 | 355篇 |
2005年 | 305篇 |
2004年 | 279篇 |
2003年 | 300篇 |
2002年 | 287篇 |
2001年 | 304篇 |
2000年 | 258篇 |
1999年 | 256篇 |
1998年 | 217篇 |
1997年 | 198篇 |
1996年 | 168篇 |
1995年 | 159篇 |
1994年 | 119篇 |
1993年 | 102篇 |
1992年 | 180篇 |
1991年 | 159篇 |
1990年 | 160篇 |
1989年 | 150篇 |
1988年 | 129篇 |
1987年 | 135篇 |
1986年 | 134篇 |
1985年 | 117篇 |
1984年 | 105篇 |
1983年 | 118篇 |
1982年 | 81篇 |
1981年 | 77篇 |
1980年 | 59篇 |
1979年 | 74篇 |
1978年 | 60篇 |
1977年 | 56篇 |
1976年 | 45篇 |
1974年 | 53篇 |
1973年 | 44篇 |
Methods: We investigated the actions of halothane on 50-200 micro Meter branches of the rat mesenteric artery that were cannulated and studied in vitro. The vessels were pressurized to 60 mmHg, and vascular dimensions were continuously monitored using a computer-based real-time image analysis system. The vessel bath was perfused with HCO3 -buffered saline (37 degrees Celsius) equilibrated with 95% Oxygen2 /5% CO2 (plus/minus halothane). The vascular endothelium was mechanically removed before cannulation in some vessels.
Results: In unstimulated vessels, halothane had a concentration-dependent vasoconstricting action (EC50 = 0.45 mM = 1.5 vol% at 37 degrees Celsius) that was largely transient and was similar to that produced by caffeine. Both halothane and caffeine constrictions were unaffected by bath [Calcium2+], nifedipine (1 micro Meter) or Cadmium2+ (100 micro Meter) and were abolished by ryanodine (10 micro Meter). In addition, caffeine responses were attenuated by halothane in a concentration-dependent manner (EC50 - 1.6 mM). In vessels preconstricted with KCl (40 mM) or phenylephrine (10 sup -6 M), halothane produced transient constriction followed by concentration-dependent vasodilation. Ryanodine, which abolished halothane constrictions, had little effect on the amplitude of KCl- or phenylephrine-induced constrictions or the vasodilating action of halothane. Removal of the endothelium likewise had little effect on the vasoconstricting or the vasodilating actions of halothane in unstimulated, KCl- or phenylephrine-constricted vessels. Halothane completely relaxed KCl and phenylephrine constrictions with EC50 values of 0.36 mM (1.2% at 37 degrees Celsius) and 0.75 mM (2.5%), respectively, in intact vessels before ryanodine; 0.25 mM (0.8%) and 0.59 mM (1.9%) in intact vessels after ryanodine; and 0.52 mM (1.7%) and 0.67 mM (2.2%) in endothelium-denuded vessels. 相似文献
Methods. Between January 1985 and December 1995, 146 patients underwent surgical therapy (repair or replacement) for native mitral valve endocarditis. All patients had documented bacterial endocarditis. Univariate and multivariate analyses were performed to determine predictors of hospital death, long-term event-free survival, and probability of repair. Patients were evaluated in three groups: all patients, patients with acute endocarditis, and patients with chronic endocarditis.
Results. There were ten hospital deaths (6.8%). Patients undergoing repair had a lower hospital mortality rate (p = 0.008) then those having replacement. Event-free survival was improved after mitral valve repair in the overall group (p = 0.02) and in the group with healed (chronic) endocarditis (p = 0.05). Although the acute endocarditis group demonstrated an improved event-free survival rate after mitral valve repair versus replacement (74% versus 20% at 6 years), this did not reach statistical significance.
Conclusions. We conclude that mitral valve repair is preferable to mitral valve replacement when possible, in patients with complications of endocarditis, as repair results in a lower hospital mortality and an improved long-term survival. 相似文献
Methods. Leukocyte depletion was examined in a canine model of regional myocardial ischemia and reperfusion. The extracorporeal circuit and cardioplegia circuits underwent leukocyte depletion by mechanical filtration. Animals were instrumented for baseline global function before 90-minute occlusion of the left anterior descending coronary artery. Global function during ischemia and at 5, 30, 60, and 90 minutes after a 60-minute cardioplegic arrest using continuous blood cardioplegia was assessed in leukocyte-depleted (n = 9) and control (n = 10) groups.
Results. No significant difference between groups was seen for systemic leukocyte counts, global function, or water content. Endothelial function was significantly protected as assessed by response to both calcium ionophore (endothelial-dependent, receptor-independent relaxation: leukocyte-depleted, 72% ± 19% of endothelin-induced constriction versus control, 46% ± 14%; p < 0.05) and acetylcholine (endothelial-dependent, receptor-dependent relaxation: leukocyte-depleted, 83% ± 11% versus control, 44% ± 15%; p < 0.05).
Conclusions. Leukocyte-mediated endothelial reperfusion injury can be attenuated by leukocyte depletion during reperfusion. 相似文献