全文获取类型
收费全文 | 463531篇 |
免费 | 42778篇 |
国内免费 | 32561篇 |
专业分类
耳鼻咽喉 | 3562篇 |
儿科学 | 5740篇 |
妇产科学 | 5090篇 |
基础医学 | 51351篇 |
口腔科学 | 7663篇 |
临床医学 | 64630篇 |
内科学 | 63066篇 |
皮肤病学 | 5023篇 |
神经病学 | 22694篇 |
特种医学 | 17013篇 |
外国民族医学 | 275篇 |
外科学 | 42136篇 |
综合类 | 86579篇 |
现状与发展 | 114篇 |
一般理论 | 37篇 |
预防医学 | 33919篇 |
眼科学 | 13189篇 |
药学 | 50068篇 |
501篇 | |
中国医学 | 30181篇 |
肿瘤学 | 36039篇 |
出版年
2024年 | 1579篇 |
2023年 | 6791篇 |
2022年 | 17666篇 |
2021年 | 22564篇 |
2020年 | 17623篇 |
2019年 | 14438篇 |
2018年 | 14998篇 |
2017年 | 14306篇 |
2016年 | 13264篇 |
2015年 | 20544篇 |
2014年 | 25595篇 |
2013年 | 23317篇 |
2012年 | 34531篇 |
2011年 | 38824篇 |
2010年 | 25975篇 |
2009年 | 21175篇 |
2008年 | 26095篇 |
2007年 | 25899篇 |
2006年 | 24788篇 |
2005年 | 23857篇 |
2004年 | 15799篇 |
2003年 | 15074篇 |
2002年 | 12480篇 |
2001年 | 10856篇 |
2000年 | 10703篇 |
1999年 | 10923篇 |
1998年 | 6891篇 |
1997年 | 6810篇 |
1996年 | 5254篇 |
1995年 | 4950篇 |
1994年 | 4207篇 |
1993年 | 2708篇 |
1992年 | 3296篇 |
1991年 | 2817篇 |
1990年 | 2376篇 |
1989年 | 2112篇 |
1988年 | 1749篇 |
1987年 | 1573篇 |
1986年 | 1322篇 |
1985年 | 944篇 |
1984年 | 487篇 |
1983年 | 370篇 |
1982年 | 203篇 |
1981年 | 231篇 |
1980年 | 154篇 |
1979年 | 204篇 |
1978年 | 73篇 |
1977年 | 53篇 |
1974年 | 43篇 |
1972年 | 37篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
42.
本文放弃传统的MSE准则,从信息论观点出发,发展了随机系统的一种最小熵(ME)控制方法,并从ME控制的等价性、控制限度、存在性、唯一性及必要条件等方面,研究了ME控制的合理性和实用性。ME方法是一种全局分析法,它不仅包含了MSE和MAP准则,且由于全文在整个推导中并未假定高斯性、线性和非时变等,因而原则上适用于诸如非高斯、非线性、时变等传统方法难以处理的复杂系统;不仅适用于工程系统,将其推广到决策、社会、经济等领域会更为自然和切合实际。 相似文献
43.
An indirect enzyme-linked immunosorbent assay (ELISA) for the detection of hexoestrol (HES) was developed, optimized and validated for the analysis of HES in pork. Many parameters, such as the volume ratio of solution A and solution B, colour developing time, pH value, incubation time, the volume ratio of the standard solution and diluted antiserum, blocking solution, blocking condition, coating solution and coating condition were studied and optimized in the paper. The regression equation of the final inhibition curve is y = - 0.3345x + 1.4955, R2=0.9913. The linear range is 0.1-8.1 ng/ml, and the IC50 is 0.671 ng/ml. The specificity of the assay was evaluated by the cross-reactivity rates of six compounds, of which two structurally related compounds had a relatively higher cross-reactivity rate of 25% and 6%. HES was added into a pork sample at 5 ng/g level and then the sample was extracted. The recovery is between 49.6% and 79.2%, and the variation coefficient is 0.164. 相似文献
44.
45.
46.
Lei Wang Moyi Sun Yuegui Jiang Lianjia Yang Delin Lei Chao Lu Yinghua Zhao Pu Zhang Yaowu Yang Jianhu Li 《Journal of oral and maxillofacial surgery》2006,64(4):636-641
PURPOSE: Perineural invasion is a frequent occurrence in salivary adenoid cystic carcinoma (ACC) and may prevent complete surgical resection. Studies have indicated that nerve growth factor (NGF) and its high-affinity receptor tyrosine kinase A (TrkA) may play a role in perineural invasion in several malignancies in which perineural invasion is observed. The present study was conducted to investigate the expression of NGF and TrkA in salivary ACC and to examine the effects of NGF on adhesion, migration and invasion capacities of a salivary ACC cell line (SACC-83) in vitro. PATIENTS AND METHODS: Expression of NGF and TrkA was explored using immunohistochemistry in paraffin-embedded tissues of 32 cases of salivary ACC. The effects of NGF on in vitro adhesion, migration, and invasion capacities of the SACC-83 cell line were examined using an MTT assay and a modified Boyden chamber assay respectively. RESULTS: In ACC specimens, 31 (96.9%) and 32 (100%) tumors showed immunoreactivity for NGF and TrkA respectively. Significant correlations were found between NGF/TrkA expression levels and perineural invasion (P < .05). In cell adhesion assay, the percent adherences of SACC-83 cells co-cultured with 25 ng/ml NGF at 1.5 hours and 5, 25 ng/ml NGF at 6 hours were significantly higher than that co-cultured with 0 ng/ml NGF (P < .05). However, high concentration of NGF (500 ng/ml) resulted in a significant inhibition of invasion (P < .05). CONCLUSION: Overexpression of NGF and TrkA in human salivary ACC tissues may constitute a reason for perineural invasion in salivary ACC. 相似文献
47.
四氧嘧啶诱发糖尿病大鼠血管紧张素的变化 总被引:1,自引:0,他引:1
实验观察了四氧嘧啶诱发糖尿病大鼠连续饲养110d后体内肾素一血管紧张素系统的变化。结果表明,血浆和心脏的血管紧张素Ⅱ含量无明显变化,而肾脏的AngⅡ含量却明显低于正常对照组。另外,心脏的心钠素(ANP)含量在糖尿病大鼠与正常对照组之间无差别,血中的糖化血红蛋白含量基本无变化。上述结果表明,糖尿病大鼠早期心脏可能无明显损伤,而肾脏的肾素一血管紧张素系统活性降低。 相似文献
48.
C L Li 《中华整形烧伤外科杂志》1990,6(4):262-4, 317
An analysis of serum free amino acid profiles in 8 patients dying from major burns revealed that free amino acid began to decrease in shock period, decrease 31.12% in infection period and 41.3% before death in comparison with the control group. The amount of BCAA-also decrease 36.27% in infection period and 56.83% before death. If the serum free amino acid in major burn drops steadily, the prognosis will be worse. 相似文献
49.
本文对我院1954-1990年收治的64例颌骨造釉细胞瘤进行了回顾性分析,未发现1例恶性。特别是我们在长期工作实践中发现肿瘤与周围正常骨质有较明显的分界。遂于1963年开始试行颌骨内种瘤出术,至1990年6月已经成功地施了12例,1例因手术时肿物巨大而且合并感染于术后10年复发外,其余11例术后随访年6个月-27年,中位12年10个月均无复发。发种手术损伤小,方法简单,无损美容,预后性,特别是对颌 相似文献
50.
TF Leung WC Tsoi CK Li KW Chik MMK Shing PMP Yuen 《Acta paediatrica (Oslo, Norway : 1992)》1998,87(6):705-777
We describe a 15-y-old girl with Fechtner-like syndrome, who is the first Chinese reported to have this rare syndrome. She presented with left homonymous hemianopia and neuroimaging revealed haemorrhage in both parietal and occipital lobes. Peripheral blood smear showed macrothrombocytopenia and intracytoplasmic inclusion bodies inside leucocytes. Thrombocytopenia and proteinuria responded to intravenous immunoglobulin and pulsed methylprednisolone. This case illustrates that life-threatening haemorrhage can occur in patients with Fechtner syndrome. Although there was no effective treatment reported in the literature, high dose steroid and immunoglobulin seemed to be useful in our patient. Our patient also had nephritic-nephrotic syndrome with renal insufficiency, which is unusual in adolescent female patients. 相似文献