全文获取类型
收费全文 | 74266篇 |
免费 | 4817篇 |
国内免费 | 3178篇 |
专业分类
耳鼻咽喉 | 263篇 |
儿科学 | 1294篇 |
妇产科学 | 717篇 |
基础医学 | 7242篇 |
口腔科学 | 1568篇 |
临床医学 | 4343篇 |
内科学 | 8529篇 |
皮肤病学 | 1914篇 |
神经病学 | 6800篇 |
特种医学 | 1345篇 |
外国民族医学 | 5篇 |
外科学 | 4124篇 |
综合类 | 9727篇 |
现状与发展 | 3篇 |
预防医学 | 5961篇 |
眼科学 | 627篇 |
药学 | 18308篇 |
15篇 | |
中国医学 | 6968篇 |
肿瘤学 | 2508篇 |
出版年
2024年 | 251篇 |
2023年 | 1049篇 |
2022年 | 1851篇 |
2021年 | 2401篇 |
2020年 | 2168篇 |
2019年 | 1822篇 |
2018年 | 1768篇 |
2017年 | 2064篇 |
2016年 | 2226篇 |
2015年 | 2378篇 |
2014年 | 4236篇 |
2013年 | 5172篇 |
2012年 | 4216篇 |
2011年 | 4593篇 |
2010年 | 3472篇 |
2009年 | 3353篇 |
2008年 | 3501篇 |
2007年 | 3533篇 |
2006年 | 3112篇 |
2005年 | 2834篇 |
2004年 | 2485篇 |
2003年 | 2137篇 |
2002年 | 1787篇 |
2001年 | 1564篇 |
2000年 | 1381篇 |
1999年 | 1223篇 |
1998年 | 1177篇 |
1997年 | 1112篇 |
1996年 | 1072篇 |
1995年 | 1014篇 |
1994年 | 905篇 |
1993年 | 772篇 |
1992年 | 779篇 |
1991年 | 696篇 |
1990年 | 692篇 |
1989年 | 660篇 |
1988年 | 615篇 |
1987年 | 536篇 |
1986年 | 554篇 |
1985年 | 818篇 |
1984年 | 754篇 |
1983年 | 566篇 |
1982年 | 569篇 |
1981年 | 526篇 |
1980年 | 481篇 |
1979年 | 337篇 |
1978年 | 246篇 |
1977年 | 202篇 |
1976年 | 172篇 |
1975年 | 123篇 |
排序方式: 共有10000条查询结果,搜索用时 14 毫秒
61.
孕妇血清与初乳中分泌型IgA含量的关系 总被引:1,自引:0,他引:1
目的探讨孕妇营养与初乳中分泌型免疫球蛋白A(SIgA)含量的关系。方法对101例孕妇作了膳食营养评价,并对其血液营养学指标与产后第3d初乳SIgA含量进行相关分析。结果孕妇血清IgA与初乳SIgA呈明显的正相关(r=0.498P<0.01);血清甘油三酯与初乳SIgA呈明显的负相关(r=-0.338P<0.005);血清叶酸与初乳SIgA呈明显正相关(孕中期r=0.737P<0.001,孕晚期r=0.362P<0.01)相关呈高度显著性。结论初乳SIgA与孕妇个体免疫状态以及孕期代谢状态有关。 相似文献
62.
Tracy Brightman Jiang-Hong Ye Elizabeth Ortiz-Jimenez Edward J. Flynn Wen-Hsien Wu Joseph J. McArdle 《Brain research》1995,678(1-2)
While adult mice receiving picrotoxin (PTX) alone responded with clonic and tonic-clonic seizures, this response was greatly suppressed for mice simultaneously injected with 2,3-butanedione monoxime (BDM). For example, 60% and 10% of the mice convulsed when injected (i.p.) with 3.0 mg/kg PTX alone or PTX plus 205 mg/kg of BDM, respectively. In contrast, a non-oxime analogue of BDM, 2,3-butanedione (BTD), did not have this anticonvulsant effect. In order to explore the basis for the anticonvulsant effect of BDM, we recorded GABA-activated currents (IGABA) of frontal cortical as well as ventromedial hypothalamic neurons before, during and after exposure to this oxime. BDM had a biphasic effect on concentrations (100 μM-40 mM) decreased and lower concentrations (0.01 μM–0.001 μM) potentiatedIGABA; these effects of BDM reversed upon washout of the oxime. In contrast, BTD had no effect onIGABA. Finally, when 0.001 μM BDM, 10–30 μM PTX and GABA were co-applied the inhibitory effect of the toxin onIGABA was markedly suppressed. These data suggest that the anticonvulsant effect of oximes involves facilitation of the inhibitory action of GABA. 相似文献
63.
两种鼠蚤成熟过程中组织化学研究Ⅰ糖原和PAS物质 总被引:3,自引:0,他引:3
目的:探讨不等单蚤Monopsyllns anisus(Rothchild)和级慢细蚤Leptopsylla segnis(Schoenherr)吸血消化成熟过程中糖原和PAS物质的变化。方法:用高碘酸-希夫反应(Periodic acid-Schiff reaction PAS)法显示未吸血蚤、吸血后不同消化时间蚤体内糖原和PAS物质。结果:2种蚤糖原和PAS物质以脂肪体含量最高。吸血后成蚤消化道各部分PAS反应均有增高,不同消化时间(24、48、72h)不存在显著差异。2种蚤中雌蚤吸血后卵黄细胞发育过程中PAS反应的变化相似,但不等单蚤发育较缓慢细蚤迟缓。结论:吸血将导致2种蚤消化道糖原不同程度的增加。亦能促进雌蚤卵黄细胞的发育。 相似文献
64.
Summary The effect of distension on adrenergic innervation was investigated in the rat urinary bladder. Bladders were distended for 3 h by forced diuresis and ballon obstruction, and specimens were taken from the bladder dome, body and neck for the demonstration of glyoxylic acid-induced fluorescence of catecholamines. Depletion of catecholamines started after 10 h and was almost complete after 2 days. The fluorescence had recovered part way after 5–7 days and was practically normal after 21 days. Small, intensely fluorescent (SIF) cells in the ganglia continued to leak catecholamines throughout the 21-day study period. The primary clinical success of distension therapy for the treatment of unstable bladder may be at least partly due to a reversible disturbance in the function of the adrenergic nerves, which have an excitatory alpha-adrenergic dominance in such cases, but the persistent leakage from SIF cells raises the question of whether distension causes prolonged disturbances in bladder function. 相似文献
65.
R GOKAL 《Nephrology (Carlton, Vic.)》1996,2(S1):s159-s162
Summary: Current peritoneal dialysis solutions are not biocompatible, particularly in respect to low pH, high osmolality and use of lactate. In addition, glucose is not an ideal osmotic agent. Recent advances in the formulation of peritoneal dialysis fluids aim to provide a more physiological environment to preserve membrane integrity. the effects of pH and lactate have been overcome by the use of bicarbonate based solutions whilst icodextrin (glucose polymers) often prolonged ultrafiltration in spite of being isomotic to uraemic plasma. Future formulations will see a combination of osmotic agents (including amino acids) and bicarbonate to achieve a more biocompatible solution whilst still meeting the ultrafiltration needs of the patients. Additives (glycosaminoglycans, procysteine) may protect the peritoneum from free radical injury. 相似文献
66.
1-乙基-6-氟-1,4-二氢-4-氧代-7-(4-芳酰硫代氨甲酰基-1-哌嗪基)-3-喹啉羧酸的合成及抗菌作用 总被引:4,自引:1,他引:3
Thirteen new 1-ethyl-6-fluoro-1,4-dihydro-4-oxo-7-(4-aroyl-thiocarbamoyl- 1 piperazinyl)-3-quinoline carboxylic acids were prepared, Their structures were characterized by elemental analysis, IR, HNMR and MS spectra.Preliminary pharmacological tests indicated that some of compounds Ia~m possess strong inhibiting activity against Escherichia coli, Bacillus subtilis and Proteus at concentration of 100 μg/ml. 相似文献
67.
Introduction – Toxic phytanic acid concentrations in patients with Refsum's disease can be reduced by plasma separation, performed either as plasmapheresis, or as cascade filtration. The latter procedure is as efficient and safe as plasmapheresis, and eliminates the need for albumin replacement. This study investigates the loss of immunoglobulins associated with the procedure. Material and methods — Immunoglobulin- and phytanic acid serum concentrations before and after cascade filtration (n=16) were measured in a patient with Refsum's disease and their removal determined. Filters with sieving coefficients for immunoglobulin G of 70% and 30% were compared with each other and with historical data on plasmapheresis. Results — While differences in immunoglobulin M loss are negligible, the loss of immunoglobulin G in cascade filtration is significantly less than that reported for plasmapheresis and depends upon the pore size of the employed filters. The loss is least with larger pore size, but this advantage becomes statistically insignificant if immunoglobulin G loss is related to the lesser decrease in phytanic acid concentration that was achieved simultaneously in this study. Conclusion — Unless transplantation of a-hydroxylase containing tissue can be established as treatment for Refsum's disease, cascade filtration appears to be the treatment of choice in order to avoid loss of albumin and to reduce the loss of immunoglobulin G. 相似文献
68.
69.
目的:为设计维甲酸治疗神经母细胞瘤可能的有效方案,本文对9-顺式维甲酸(9-cis retinoic acid,9-cisRA)体外诱导分化神经母细胞瘤细胞(SK-N-SH)作用进行了研究。方法:SK-N-SH细胞经9-cisRA处理后,采用相差显微镜,神经纤维银染法,透射电镜观察等手段。观察9-cisRA对细胞生长的影响。结果:9-cisRA作用SK-N-SH细胞7d后,细胞形态发生变化;12d时出现神经原性表型,多个细胞形成“神经节”,节间形成粗而长的类神经纤维;尼氏小体和银染法亦证明细胞产生显著分化,透射电镜观察结果表明,9-cisRA对该细胞有分化作用。却无明显凋亡诱导作用。结论:9-cisRA对神经母细胞瘤细胞体外能产生明显诱导分化作用。 相似文献
70.
Release of cholecystokinin from rat cerebral cortex in vivo: role of GABA and glutamate receptor systems 总被引:1,自引:0,他引:1
Using cortical cups in chloralose-urethanized rats, the in vivo release of cholecystokinin-like immunoreactivity (CCK-LI) from cerebral cortex was examined. Resting levels of cholecystokinin-like immunoreactivity ranged from 20 to 30 pg/20 min sample. The addition of potassium (40 mM) in excess, resulted in a highly significant elevation in the levels of CCK-LI in the cortical superfusate. Deletion of calcium and the substitution of cobalt (10 mM), resulted in a significant reduction in both resting release and the release otherwise evoked by the addition of potassium. Focal electrical stimulation of the cortex (20 Hz), resulted in a significant (1.9 +/- 0.2-fold, n = 8) increase in the levels of CCK-LI. The addition of glutamate (10(-6)-10(-4) M) of kainic acid (10(-8)-10(-6) M), also resulted in significant elevations in the levels of CCK-LI. The co-administration of a putative glutamate receptor antagonist, kynurenic acid (10(-4) M) resulted in a significant reduction in the levels of release otherwise evoked by the addition of glutamate, but not by electrical stimulation. The addition of GABA (10(-5)-10(-3) M) resulted in a dose-dependent decrease in the resting release of CCK-LI, and the release evoked by glutamate. Picrotoxin (10(-6)-10(-4) M), resulted in a highly significant increase in the levels of CCK-LI in the cortical effluent. These results are consistent with a tonic GABAergic inhibition of CCK-releasing neurons. The treatment of the animal with diazepam (30 mg/kg, i.p.) also resulted in a significant reduction in resting release and the release otherwise evoked by focal cortical stimulation. 相似文献