全文获取类型
收费全文 | 71103篇 |
免费 | 4425篇 |
国内免费 | 3066篇 |
专业分类
耳鼻咽喉 | 253篇 |
儿科学 | 1174篇 |
妇产科学 | 699篇 |
基础医学 | 6976篇 |
口腔科学 | 1412篇 |
临床医学 | 4196篇 |
内科学 | 8095篇 |
皮肤病学 | 1808篇 |
神经病学 | 6628篇 |
特种医学 | 1305篇 |
外国民族医学 | 5篇 |
外科学 | 3947篇 |
综合类 | 9235篇 |
现状与发展 | 3篇 |
预防医学 | 5122篇 |
眼科学 | 592篇 |
药学 | 17792篇 |
16篇 | |
中国医学 | 6935篇 |
肿瘤学 | 2401篇 |
出版年
2024年 | 248篇 |
2023年 | 1010篇 |
2022年 | 1719篇 |
2021年 | 2212篇 |
2020年 | 2105篇 |
2019年 | 1785篇 |
2018年 | 1708篇 |
2017年 | 1992篇 |
2016年 | 2166篇 |
2015年 | 2286篇 |
2014年 | 4096篇 |
2013年 | 4948篇 |
2012年 | 4050篇 |
2011年 | 4447篇 |
2010年 | 3358篇 |
2009年 | 3232篇 |
2008年 | 3378篇 |
2007年 | 3429篇 |
2006年 | 3011篇 |
2005年 | 2696篇 |
2004年 | 2383篇 |
2003年 | 2045篇 |
2002年 | 1700篇 |
2001年 | 1472篇 |
2000年 | 1300篇 |
1999年 | 1153篇 |
1998年 | 1097篇 |
1997年 | 1039篇 |
1996年 | 1002篇 |
1995年 | 938篇 |
1994年 | 839篇 |
1993年 | 709篇 |
1992年 | 705篇 |
1991年 | 648篇 |
1990年 | 642篇 |
1989年 | 607篇 |
1988年 | 561篇 |
1987年 | 500篇 |
1986年 | 521篇 |
1985年 | 779篇 |
1984年 | 725篇 |
1983年 | 537篇 |
1982年 | 536篇 |
1981年 | 498篇 |
1980年 | 456篇 |
1979年 | 315篇 |
1978年 | 239篇 |
1977年 | 189篇 |
1976年 | 165篇 |
1975年 | 117篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Primary cultures enriched in neurons dissociated from embryonic rat cerebra were used to demonstrate that platelet activating factor and the structurally related ether glycerolipid, dodecylglycerol, are readily taken up in small amounts by neurons and that they stimulate the differentiation of neurons. The stimulation of neuronal differentiation was observed as a precocious development of axon-like extensions which correlated with a concentration-dependent increase in neuronal-specific enzyme activities. This stimulation of morphological and neurochemical factors by either platelet activating factor or dodecylglycerol was almost completely abolished by triazolam, a known inhibitor of platelet activating factor function. Neither platelet activating factor nor dodecylglycerol at the concentrations used to achieve stimulation of neuronal differentiation compromised the plasma membrane, as indicated by the lack of leakage of cytoplasmic lactic acid dehydrogenase. 相似文献
22.
It is known that low glucose concentrations increase the aspartate and decrease the glutamate content of brain tissue both in vivo and in vitro. To see whether these changes occur in the transmitter compartment or not, the release of aspartate and glutamate evoked by electrical-field stimulation or by high K+ was followed in slices of rat hippocampus superfused with 5 or 0.2 mM glucose. Superfusion with 0.2 mM glucose increased the evoked release of aspartate about ten times and that of glutamate about threefold. This shift in the ratio of aspartate to glutamate released was accompanied by a similar increase in the relative amount of aspartate contained in the slices. The high evoked release of aspartate and glutamate was well maintained, provided 0.5 mM glutamine was added to the medium. Changing the concentration of glucose after the first period of stimulation rapidly altered the relative amounts of aspartate and glutamate released but not the enhanced release of glutamate. The large evoked release of both aspartate and glutamate in 0.2 mM glucose was almost entirely Ca2+-dependent. The relative amounts of aspartate and glutamate released by 50 mM K+ also changed when the glucose concentration was reduced. Results suggest two effects of low glucose concentrations: an increase in the overflow of synaptically released glutamate due to a decreased uptake and an increase in the proportion of aspartate to glutamate formed and released from the transmitter pool. These observations are consistent with the interpretation that these two transmitters can be released in different proportions from the same terminals. 相似文献
23.
《Nutrition reviews》1987,45(10):246-248
Increasing dietary 18:2 n-6/18:3 n-3 causes similar relative changes in fatty acid profiles of phosphatidylethanolamine and phosphatidylcholine from rat neural and erythrocyte membranes. 相似文献
24.
胰岛素样生长因子1对新生大鼠缺氧缺血性脑损伤保护机制的研究 总被引:1,自引:0,他引:1
目的 建立单侧缺氧缺血性脑损伤 (HIBD)动物模型 ,研究胰岛素样生长因子 1(IGF 1)对HIBD的影响和可能机制。 方法 选择健康 7日龄Wistar大鼠 12 0只 ,建立HIBD模型 ,随机分成假手术组、HIBD组、HIBD后 0 .2mg/kg人基因重组IGF 1干预组 (RH IGF 1组 )、0 .0 6 6mg/kg人基因重组IGF 1干预组 (SRH IGF 1组 )及盐水对照组 (对照组 )。各组按观察时段进一步分为 2 4、4 8、72h组 ,每组 8只。各组于规定时刻观测脑形态学改变、谷氨酸 (Glu)含量、凋亡细胞计数、Bcl 2蛋白表达。 结果 (1)HIBD 4 8h组Glu(116 2 .2± 10 8.1)mg/kg ,较假手术组(75 0 .9± 5 3.4 )mg/kg明显升高 (P <0 .0 5 ) ;HIBD组凋亡细胞计数 [2 4h :(7.6± 1.9) % ,4 8h(12 .6±1.2 ) % ,72h :(13.8± 0 .9) % ],较假手术组 [2 4h(2 .0± 0 .2 ) % ,4 8h(2 .0± 0 .3) % ,72h(2 .0±0 .2 ) % ]明显增加 (P均 <0 .0 5 )。 (2 )与对照组相比 ,RH IGF 1组脑组织病变减轻 ;干预 4 8h组Glu[SRH IGF 1组 (781.4± 5 4 .2 )mg/kg ,RH IGF 1组 (74 0 .5± 4 6 .6 )mg/kg],较对照组 (112 6 .6± 4 8.0 )mg/kg明显降低 (P均 <0 .0 5 ) ;RH IGF 1组凋亡细胞计数 [2 4h :(3.6± 0 .9) % ,4 8h(8.2± 2 .2 ) % ,72h(9.4± 1.4 ) % ],较对 相似文献
25.
多发性硬化患者血清尿酸水平变化的研究 总被引:2,自引:0,他引:2
目的 探讨多发性硬化 (MS)患者血清尿酸 (UA)水平的变化及其临床意义。方法 采用酶定量分析法对 4 3例MS患者和 4 5名正常对照者的血清UA水平进行检测。结果 MS组血清UA水平明显低于对照组 (P <0 0 1)。MS组中病程越长 (P <0 0 1)、神经伤残程度越重 (DSS评分越高 ) (P <0 0 5 ) ,血清UA水平越低 ;女性患者UA水平明显低于男性患者 (P <0 0 0 1) ;经过糖皮质激素治疗后血清UA水平明显回升 (P <0 0 0 1) ,但治疗前血清UA水平越低则疗效越差 (P <0 0 1、P <0 0 5 )。结论 MS患者血清UA水平降低 ,且与MS的病程、伤残程度、疗效及性别密切相关。UA水平升高可能为激素治疗MS的一个作用机制 相似文献
26.
经临床鉴定静脉内注射小儿氨基酸对治疗胎儿宫内发育迟缓具有肯定效果。在B超监视下,使用小儿氨基酸的孕妇组于用药期间,胎儿生长参数BPD和HC显著高于使用成人氨基酸的孕妇组。10例足月娩出胎儿体重均达到甚至超过2.5kg。由此得出结论:使用小儿氨基酸注射液对于改善胎儿宫内发育迟缓优于成人氨基酸。 相似文献
27.
为了探讨精神分裂症患者治疗期间多巴胺的变化,我们选择舒必利治疗组20例,非舒必利治疗组10例作为病例组;15例非精神病患者作为对照组;检测脑脊液中多巴胺代谢产物高香草酸的含量;结果显示两组无显著性差异。精神分裂症患者治疗后舒必利组高香草酸含量升高,非舒必利组则降低,进一步分析显示舒必利治疗组非显效者较显效者治疗后高香草酸显著升高。提示机体对药物阻滞多巴胺受体后代偿反应的强弱与疗效有一定关系。 相似文献
28.
为证明癫痫发作早期一氧化氮(NO)抗发作效应,用NO合酶(NOS)抑制剂L-硝基精氨酸甲酯(L-NAME)对大鼠红藻氨酸(KA)诱导性发作进行干预,同时用分光光度法检测海马结构中NOS活性的早期变化。发现KA发作10min、30min组海马结构中NOS活性明显升高,而KA注射前30min给予L-NAME可显著抑制NOS活性的升高,这种抑制效应与大鼠KA发作中湿狗样摇动(WDS)的提早出现和发生次数增多显著相关。结果提示在KA诱导大鼠发作早期内源性NO具有明显的抗发作效用。 相似文献
29.
The database of the Hungarian randomised controlled trial of periconceptional multivitamin supplementation for the prevention of neural-tube defects was used to evaluate the length of the pre- and postovulatory phases of the menstrual cycle before and during multivitamin supplementation. The female cycle was more regular (i.e., the variance was lower) during the multivitamin supplementation. 相似文献
30.
Effect of isoelectric point on biodistribution and inflammation imaging with indium-111-labelled IgG
Caroline I. ten Kate Alan J. Fischman Robert H. Rubin A. J. Fucello D. Riexinger Robert A. Wilkinson Lina Du Ban An Khaw H. William Strauss 《European journal of nuclear medicine and molecular imaging》1990,17(6-8):305-309
Electrostatic effects play an important role in protein interactions and may alter the biodistribution of antibodies. To study the effect of molecular charge on the biodistribution and infection imaging properties of human polyclonal immunoglobulin G (IgG), its iso electric point was varied by changing the level of diethylene triamine penta-acetic acid (DTPA) substitution: 0.8, 0.9, 3.7, 5.1 and 5.9 DTPA/IgG. Biodistributions of the different IgG preparations were determined at 10 min, 1, 6, 24, and 48 h post injection in normal rats, and infection imaging properties were determined in rats withEscherichia coli thigh infections. The biodistribution was significantly affected by pl. The immunoglobulin preparations with 0.9 and 3.7 DTPA/IgG showed faster clearance from the circulation and generally lower accumulation in most organs. The images had a target-to-background ratio of approximately 1.3–2.3:1. These results suggest that even though targeting is not affected by the level of DTPA substitutions, preparations with 0.9 and 3.7 DTPA/IgG may be superior imaging agents because of reduced accumulation by background organs. 相似文献