全文获取类型
收费全文 | 8531篇 |
免费 | 429篇 |
国内免费 | 398篇 |
专业分类
耳鼻咽喉 | 13篇 |
儿科学 | 100篇 |
妇产科学 | 111篇 |
基础医学 | 1143篇 |
口腔科学 | 32篇 |
临床医学 | 534篇 |
内科学 | 1537篇 |
皮肤病学 | 61篇 |
神经病学 | 381篇 |
特种医学 | 144篇 |
外科学 | 493篇 |
综合类 | 1286篇 |
预防医学 | 1038篇 |
眼科学 | 69篇 |
药学 | 1615篇 |
2篇 | |
中国医学 | 642篇 |
肿瘤学 | 157篇 |
出版年
2024年 | 15篇 |
2023年 | 74篇 |
2022年 | 141篇 |
2021年 | 169篇 |
2020年 | 158篇 |
2019年 | 124篇 |
2018年 | 150篇 |
2017年 | 155篇 |
2016年 | 228篇 |
2015年 | 156篇 |
2014年 | 372篇 |
2013年 | 565篇 |
2012年 | 342篇 |
2011年 | 468篇 |
2010年 | 370篇 |
2009年 | 366篇 |
2008年 | 450篇 |
2007年 | 458篇 |
2006年 | 388篇 |
2005年 | 371篇 |
2004年 | 373篇 |
2003年 | 381篇 |
2002年 | 280篇 |
2001年 | 256篇 |
2000年 | 257篇 |
1999年 | 240篇 |
1998年 | 226篇 |
1997年 | 182篇 |
1996年 | 204篇 |
1995年 | 183篇 |
1994年 | 159篇 |
1993年 | 137篇 |
1992年 | 141篇 |
1991年 | 134篇 |
1990年 | 92篇 |
1989年 | 84篇 |
1988年 | 67篇 |
1987年 | 64篇 |
1986年 | 36篇 |
1985年 | 64篇 |
1984年 | 49篇 |
1983年 | 33篇 |
1982年 | 36篇 |
1981年 | 29篇 |
1980年 | 23篇 |
1979年 | 21篇 |
1978年 | 15篇 |
1977年 | 15篇 |
1976年 | 18篇 |
1975年 | 13篇 |
排序方式: 共有9358条查询结果,搜索用时 406 毫秒
71.
Summary. Superoxide dismutase-like activity (SOD-like), isoenzyme lactate dehydrogenase-C4 (LDH-C4) and NADH-diaphorase activities in spermatozoa have been investigated from 58 normozoospermic and 27 oligozoospermic men. Significantly higher SOD-like, LDH-C4 and diaphorase activities ( P <0.01, P <0.005 and P <0.0001, respectively) were detected in spermatozoa from oligozoospermic men, compared to the activities found in normozoospermic samples. SOD-like activity (mean±SE) in oligozoospermic samples amounted to 8.3±1.6 U 10−8 spermatozoa, while in spermatozoa in normozoospermic men with a sperm concentration above 20 million of spermatozoa per ml amounted to 4.2±0.5 U 10−8 . There was a close correlation between the SOD-like activity and biochemical indicators of the presence of residual cytoplasm i.e. isoenzyme LDH-C4 and NADH-diaphorase (r = 0.53 and r = 0.66 in normozoospermic and r = 0.63 and r = 0.54 in oligozoospermic men, respectively). A positive relationship between SOD-like activity and experimentally-induced lipid peroxidation was detected in 54 infertile men (r = 0.30; P <0.05). These findings suggest that a higher level of superoxide dismutase-like activity may reflect a defect in the development or maturation of spermatozoa and, thereby, a decreased fertility potential. Hence, determination of SOD-like activity may give information on the state of maturity of human spermatozoa, while its role in the antioxidative protection remains to be determined. 相似文献
72.
我们用药掺食法培养吗啡依赖大鼠模型,研究了吗啡依赖大鼠肝线粒体自由基损伤及其结构与功能的变化。结果发现:超氧化物歧化酶(SOD)活性明显降低、丙二醛(MDA)含量明显升高;细胞色素C氧化酶活性、心磷脂含量和膜流动性都明显降低。这表明吗啡依赖大鼠肝线粒体自由基清除能力降低,导致自由基损伤增加,并进一步影响到线粒体的结构与功能。线粒体结构与功能的这种改变可能在吗啡诱导的肝损伤中有重要作用。 相似文献
73.
膳食纤维与不同蛋白质联用对大鼠胆固醇代谢的影响 总被引:6,自引:0,他引:6
杨东仁 《中国慢性病预防与控制》1998,6(1):17-19,23
观察4种膳食纤维在两种蛋白来源下,对高脂血症大鼠生长、血脂、肝胆固醇、粪类固醇及胆汁成分的影响。结果表明:①四种膳食纤维均可降低大鼠血清TC水平,尤以豆胶效果显著。②豆胶显著升高HDL-C/LDL-C。膳食蛋白为大豆蛋白时,豆胶、沙棘皮可显著升高血清HDL-C、HDL-C/TC。③豆胶显著减少肝胆固醇累积,两种沙棘皮与大豆蛋白联用降脂强于与酪蛋白共用。④蛋白来源显著影响粪类固醇的排出,纤维类型可影响中性固醇排出并与蛋白质有交互作用。提示:蛋白质与膳食纤维之间的交互作用是探讨营养素与脂质代谢不可忽视的因素。 相似文献
74.
Bharti Razdan Peter J. Marro Outi Tammela Rajiv Goel Om Prakash Mishra Maria Delivoria-Papadopoulos 《Brain research》1993,600(2):308-314
The effect of hypoxia on the structure and function of the synaptosomal membranes and myelin fraction (glial cells, neuronal cell bodies and axonal membranes) was investigated by measuring Na+,K+-ATPase activity and levels of lipid peroxidation products in cerebral cortical synaptosomal membranes and myelin fractions obtained from newborn piglets. Hypoxic hypoxia was induced and cerebral hypoxia was documented as a decrease in the ratio of phosphocreatine to inorganic phosphate (PCr/Oi) using31P-NMR spectroscopy. PCr/Pi decreased from baseline of2.93 ± 0.76to0.61 ± 0.36 during hypoxia. The synaptosomal membrane Na+,K+-ATPase activity decreased from a control value of56.6 ± 3.7to40.4 ± 6.0 μgmol Pi/mg protein/h during hypoxia. The level of conjugated dienes increased from zero (reference value) to4.5 ± 2.7 nmol/mg lipid and the level of fluorescent compounds increased from23.5 ± 2.2to92.6 ± 46.4 ng quinine sulfate/mg lipid in the synaptosomal membranes during hypoxia. No change in myelin fraction Na+,K+-ATPase activity or levels of lipid peroxidation products were noted. These data indicate that sunaptosomal membranes, rich in polyunsaturated fatty acids, are more susceptible to oxygen free radical mediated lipid peroxidative damage during hypoxia. 相似文献
75.
Aitken R.John; Buckingham Donna W.; Brindle James; Gomez Emelio; Baker H.W.Gordon; Irvine D.Stewart 《Human reproduction (Oxford, England)》1995,10(8):2061-2071
The addition of luminol to unprocessed semen samples resultedin the generation of chemiluminescent signals, the intensityof which was highly correlated with the level of leukocyte contamination.Despite the spontaneous oxidant-generating capacity of seminalleukocytes, no correlations were observed between leukocytecontamination and the fertility status of the subjects or anyaspect of the semen profile, including the motility of the spermatozoaor their performance in a hyaluronate penetration assay. Luminol-dependentchemiluminescence and leukocyte contamination were also correlatedin washed sperm suspensions prepared either by repeated centrifugationor on discontinuous Percoll gradients. However, in such spermsuspensions, the spontaneous generation of oxidants by contaminatingleukocytes (>2x104 leukocytes/ml) was invariably associatedwith a decreased capacity for movement. Moreover, causativeassociations between leukocyte contamination, reactive oxygenspecies generation, lipid peroxidation and impaired sperm motilitywere revealed by experiments involving the selective additionor removal of activated leukocytes. From these observationswe can conclude that low concentrations of leukocytes are acommon feature of the human ejaculate and can impair sperm function,particularly in the absence of seminal plasma. These findingshave implications for our understanding of the importance ofleukocytospermia in defining the fertility of human spermatozoain vivo and in vitro. 相似文献
76.
维生素E对培养心肌细胞脂质过氧化损伤的保护 总被引:3,自引:0,他引:3
应用氢过氧化枯烯引发体外培养的乳鼠心肌细胞脂质过氧化损伤过程,观察了添加维生素E(200mg/L的α-生育酚)的影响。结果显示:维生素E能明显减轻细胞脂质过氧化物的蓄积、细胞内肌酸激酶漏出和DNA断裂,保护细胞膜流动性、肌球蛋白轻链肌酸激酶和头部ATP酶的活性;但对 ̄3H-TdR掺入的影响不显著。表明维生素E具有抵抗脂质过氧化所致心肌细胞损伤的作用。 相似文献
77.
Salahudeen Abdulla K.; Wang Chunyou; Bigler Steven A.; Dai Zhongyi; Tachikawa Hiroyasu 《Nephrology, dialysis, transplantation》1996,11(4):635-642
BACKGROUND AND PURPOSE.: Heme-proteins, besides causing renal tubular obstruction, maycontribute to rhabdomyolysis-induced renal injury through aheme-iron-mediated lipid peroxidation process. In the presentstudy, we compared the combined therapy of a lipid peroxidationinhibitor, 21-aminosteroid (21-AS) and fluid-alkaline-mannitol(FAM) diuresis with either of them alone to determine the efficacyof the combination therapy and to delineate the roles of lipidperoxidation and cast formation. METHODS AND RESULTS.: Employing Raman spectroscopy, we confirmed in vitro the abilityof 21-AS to inhibit iron-induced fatty acid peroxidation. 21-ASwas then administered to rats developing renal failure fromglycerol-induced rhabdomyolysis. Although 21-AS inhibited rhabdomyolysis-inducedplasma and renal lipid peroxidation, renal protection was incomplete.Administration of FAM to inhibit cast formation afforded a betterrenal protection. However, when these therapies were combinedto inhibit both lipid peroxidation and cast formation, therewas a synergistic renal functional protection. This was accompaniedby a maximum inhibition of renal and plasma lipid peroxidation,as well as, renal tubular necrosis and cast formation. Comparedto combination therapy, FAM therapy alone, despite identicalvolume, was accompanied by a higher tubular necrosis and castformation. CONCLUSIONS.: That combining a lipid peroxidation inhibitor with fluid-alkalinediuresis in rhabdomyolysis further lowers renal lipid peroxidation,tubular necrosis and cast formation and synergistically limitsrenal dysfunction (i) supports a role for lipid peroxidationin the pathophysiology of rhabdomyolysis ARF, (ii) underscoresthe role of intratubular heme retention, a cause for tubularobstruction as well a source for prodigious amount of iron,likely involved in the lipid peroxidation, and (iii) raisesthe possibility of interactions between non-oxidant and oxidantmechanisms. 相似文献
78.
EffectofShengmaisan(生脉散)onLipidPeroxidationDamageinAcuteMyocardialinfarctionPatientsLUBao-jing(吕宝经);RONGYe-zhi(荣烨之);ZHAOMei-h... 相似文献
79.
The accumulation of oxygen free radicals is reported to occur in the organs subjected to temporary ischemia followed by reperfusion, resulting in the fatal outcome of the animals. The effects of human SOD, a representative scavenger of oxygen free radicals, on the survival rates were investigated in the rats with temporary splanchnic ischemia. The temporary ischemia was induced by the occlusion of anterior mesenteric and celiac arteries for 30min under anesthesia. Prior and after treatment with 2mg/100g of human SOD, iv or sc, produced significant improvements in survival rates. Human SOD, cloned from human placenta DNA and expressed in microorganisms, has extreme homogeneity. The results suggest the possible introduction of human SOD into clinical field as an effective scavenger of oxygen free radicals.(Ogawa R, Bitoh H, Ohi Y: The effect of human SOD on the survival rate in rats with temporary splanchnic ischemia. J Anesth 2: 41–45, 1988) 相似文献
80.
Henri J. Vial Jean R. Philippot Donald F.H. Wallach 《Molecular and biochemical parasitology》1984,13(1):53-65
The cholesterol synthesis of rhesus monkey erythrocytes parasitized by Plasmodium knowlesi and human erythrocytes infected by P. falciparum, as measured by incorporation of [1-14C]acetate and 3H2O, was almost undetectable, concordant with very low levels of measurable 3-hydroxy-3-methyl glutaryl-CoA reductase activity. In addition, both types of infected cells exchanged cholesterol with the plasma at the same rate as uninfected cells. The data do not exclude the possibility of cholesterol transfer from uninfected to infected cells. 相似文献