全文获取类型
收费全文 | 46645篇 |
免费 | 2755篇 |
国内免费 | 482篇 |
专业分类
耳鼻咽喉 | 654篇 |
儿科学 | 1709篇 |
妇产科学 | 765篇 |
基础医学 | 5987篇 |
口腔科学 | 1048篇 |
临床医学 | 3404篇 |
内科学 | 11040篇 |
皮肤病学 | 1477篇 |
神经病学 | 3634篇 |
特种医学 | 1361篇 |
外国民族医学 | 2篇 |
外科学 | 6046篇 |
综合类 | 1280篇 |
一般理论 | 16篇 |
预防医学 | 3937篇 |
眼科学 | 1339篇 |
药学 | 3105篇 |
6篇 | |
中国医学 | 500篇 |
肿瘤学 | 2572篇 |
出版年
2024年 | 36篇 |
2023年 | 352篇 |
2022年 | 331篇 |
2021年 | 1366篇 |
2020年 | 719篇 |
2019年 | 1397篇 |
2018年 | 2039篇 |
2017年 | 1244篇 |
2016年 | 1083篇 |
2015年 | 1083篇 |
2014年 | 1334篇 |
2013年 | 2040篇 |
2012年 | 3433篇 |
2011年 | 3826篇 |
2010年 | 1919篇 |
2009年 | 1235篇 |
2008年 | 2904篇 |
2007年 | 2966篇 |
2006年 | 2689篇 |
2005年 | 2776篇 |
2004年 | 2529篇 |
2003年 | 2440篇 |
2002年 | 2208篇 |
2001年 | 1618篇 |
2000年 | 1978篇 |
1999年 | 1172篇 |
1998年 | 351篇 |
1997年 | 247篇 |
1996年 | 245篇 |
1995年 | 217篇 |
1994年 | 148篇 |
1993年 | 149篇 |
1992年 | 211篇 |
1991年 | 168篇 |
1990年 | 153篇 |
1989年 | 160篇 |
1988年 | 143篇 |
1987年 | 121篇 |
1986年 | 105篇 |
1985年 | 107篇 |
1984年 | 87篇 |
1983年 | 75篇 |
1982年 | 61篇 |
1981年 | 48篇 |
1980年 | 48篇 |
1979年 | 29篇 |
1978年 | 34篇 |
1977年 | 38篇 |
1976年 | 28篇 |
1975年 | 23篇 |
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
81.
吡酮酸类抗菌药物的研究Ⅷ.1-对氟苯基-6-氟-1,4-二氢-4-氧-7-(1-哌嗪)噌啉-3-羧酸及其类似物的合成和构效关系 总被引:1,自引:0,他引:1
为探讨构效关系,合成了1-对氟苯基-6-氟-1,4-二氢-4-氧-7-(1-哌嗪)噌啉-3-羧酸及其喹啉、萘啶、吡啶[2,3-C]哒嗪环系类似物16个。测定了对大肠杆菌的MIC。用Hückel分子轨道理论(HMO)方法计算了四个母体环上电子密度。结果表明:环中氮的位置对药效团——3位羧基和4位羰基氧原子上电子密度的影响较大而影响其抗菌活性。喹啉、萘啶两环系的3位羧基和4位羰基氧原子上的电子密度较高,其体外抗菌活性较高;而噌啉及吡啶[2,3-C]哒嗪两环系的电子密度较低,其体外抗菌活性较低甚至消失。 相似文献
82.
Roberto Rivera-Luna Marta Zapata-Tarrés Aurora Medina-Sansón Enrique López-Aguilar Ana Niembro-Zúñiga J. Amador Zarco Alfonso Marhx-Bracho Fernando Rueda-Franco Leticia Bornstein-Quevedo 《Child's nervous system》2007,23(5):543-547
Objective The purpose of this study is to analyze clinical aspects and disease-free survival (DFS) in children less than 3 years of
age diagnosed with low-grade astrocytoma.
Methods In a period of 24 years (1980–2004), a total of 43 (5.4%) children were registered with these characteristics. Twenty-three
patients had pilocytic astrocytoma, 18 diffused, and 2 mixed. Thirty-one (72.1%) children had incomplete surgical tumor resection
and 12 (27.9%) had a complete tumor resection. Twelve (27.9%) patients had cranial radiotherapy and 17 (39.5%) received chemotherapy.
Overall survival was recorded in 23 (53%). DFS was 50% at 250 months of follow-up for the whole group. DFS for the supratentorial
group was 60% at 250 months, whereas, for the infratentorial, it was 22% at 120 months (p = 0.008).
Conclusion The only favorable prognostic pattern was the supratentorial presentation. Radiotherapy and chemotherapy did not alter the
outcome. 相似文献
83.
目的:分离培养小鼠骨髓间充质干细胞,研究其体外培养的生物特性。方法:获取骨髓间充质干细胞进行培养,倒置相差显微镜观察细胞生长情况。绘制生长曲线,冷冻保存细胞复苏后的生长状况观察。免疫细胞化学法鉴定细胞表面抗原。在地塞米松、β-甘油磷酸钠、抗坏血酸的作用下,进行成骨诱导分化。结果:原代和传代培养的细胞体外培养细胞呈现梭形、多角形外观,具有较强的生长增殖能力,复苏细胞生长状况无明显改变;细胞CD44。CD54抗原有阳性表达,CD34呈阴性表达。分化细胞表现成骨细胞特性,合成碱性磷酸酶(ALP)能力增强,矿化结节逐渐出现。结论:建立稳定可靠的分离培养小鼠骨髓MSCs方法,分离出的MSCs具有干细胞的生物特性,可用于骨组织工程中的种子细胞。 相似文献
84.
A V Ferrer-Montiel M S Montal M Díaz-Mu?oz M Montal 《Proceedings of the National Academy of Sciences of the United States of America》1991,88(22):10213-10217
Protein phosphorylation is a ubiquitous and one of the most effective means of regulating protein activity. Receptor phosphorylation is a key event in signal transduction. The question, therefore, that arises is whether this modulatory mechanism might produce functional changes in a membrane receptor in the absence of its naturally occurring ligand. To examine this issue, single-channel properties of purified acetylcholine receptors (AChRs) from Torpedo californica reconstituted in lipid bilayers were studied in the absence of ACh in both unphosphorylated preparations and after in vitro phosphorylation by a purified catalytic subunit of cyclic AMP-dependent protein kinase (protein kinase A). Notably, the spontaneous open-channel probability of phosphorylated AChRs is significantly higher than that of unphosphorylated AChRs. Channel activation by protein kinase A is correlated with AChR phosphorylation and is abolished by alpha-bungarotoxin. Analysis of probability distributions of the open dwell times indicates that, similar to unphosphorylated AChR has two distinct open states, short- and long-lived. The frequency of occurrence of the long openings over the short and the magnitude of both time constants increase after phosphorylation, as they do with agonist concentration. Thus, phosphorylation of AChR gamma and delta subunits activates AChR channel opening in the absence of ligand binding. This result is compatible with the notion that protein phosphorylation may effectively act as an intracellular ligand with the phosphorylation sites envisioned as cytoplasmic ligand binding sites. 相似文献
85.
目的目前,对中国人抑郁体验的现象学理解很大程度上依赖于西方教科书和国际诊断系统中的描述。而临床经验告诉我们,不同地区、不同文化对情绪痛苦的表达有着各自的特点;但中国在这方面还缺乏研究。为此,我们采用民俗学方法对广州地区就诊人群的抑郁体验进行了研究。方法在广州市精神卫生中心门诊,采用定额取样招募40例有抑郁情绪的患者;问及的合适的病人共43人,只有3人不同意参加。采用开放式深入民俗学访谈了解患者的抑郁体验,即让患者用他们自己的话来讲述患病经历。对访谈进行录音,转录为文字并译成英文。对中英文记录分别进行了内容分析。结果除了西方教科书和诊断系统中描述的抑郁症状外,还发现了六个情感体验的类别:本地情感语汇、具身的情绪体验、隐含的忧伤、难以言状的痛苦、情绪不良造成的人际不和谐,以及专注于失眠。结论精神病学教科书和诊断系统中的描述未能涵盖中国抑郁患者对抑郁症状的全部体验。需要进一步研究抑郁体验与生活事件的关联及其在不同文化下的表现方式,这样才能作出与文化相适应的有效诊断。 相似文献
86.
María de Oña Navarro Santiago Melón Susana Méndez Beatriz Iglesias Ana Palacio María J. Bernardo José L. Rodriguez-Lambert Ernesto Gómez 《Transplant international》2002,15(11):570-573
Ganciclovir (GCV) prophylaxis or pre-emptive therapy significantly reduce the rate of cytomegalovirus (CMV) disease and viremia, but increase the potential for emergence of ganciclovir-resistant CMV strains. The inhibitor concentration at 50% (IC(50)) of GCV from 156 CMV isolates from 59 renal or heart transplant recipients was calculated by means of a rapid phenotypic susceptibility assay. Twenty-seven strains were from 14 patients undergoing GCV therapy. The IC(50) was higher in patients under the prophylaxis regimen. One CMV strain, from a heart transplant recipient, became GCV-resistant after 1 month of therapy (IC(50)=13.7 micromol/l). These data, together with clinical and virological markers, suggested that a switch to foscarnet was necessary, and good evolution was observed. Thus, assay of CMV susceptibility to GCV could be helpful in clinical management. 相似文献
87.
88.
M A Brancós P Peris J M Miró A Monegal J M Gatell J Mallolas J Mensa S García J Mu?oz-Gomez 《Seminars in arthritis and rheumatism》1991,21(2):81-87
Over a 6-year period (1982 to 1988), 36 episodes of septic arthritis were diagnosed in 35 heroin addicts from Barcelona, Spain. Thirty (86%) were men and five (14%) were women, with a mean age of 24 years (range, 14 to 39). Twenty-nine episodes (80%) were monoarticular and seven (20%) were oligoarticular. The sacroiliac (16 cases), sternoclavicular (8), hip (5), and shoulder (4) joints were most frequently infected. Staphylococcus aureus and Pseudomonas aeruginosa were the etiological agents in 75% and 11% of episodes, respectively. Response to antibiotic treatment was good in 32 cases (90%), eight patients needed surgical drainage, and none died. We conclude that septic arthritis in heroin addicts localizes predominantly in axial joints. In our geographic area, infection with S aureus is more frequent than with gram-negative rods such as P aeruginosa or Serratia marcescens, which are most frequently found in reports from the United States. 相似文献
89.
90.