全文获取类型
收费全文 | 25632篇 |
免费 | 2038篇 |
国内免费 | 1755篇 |
专业分类
耳鼻咽喉 | 258篇 |
儿科学 | 380篇 |
妇产科学 | 381篇 |
基础医学 | 3316篇 |
口腔科学 | 506篇 |
临床医学 | 3317篇 |
内科学 | 4276篇 |
皮肤病学 | 322篇 |
神经病学 | 1486篇 |
特种医学 | 793篇 |
外国民族医学 | 15篇 |
外科学 | 2805篇 |
综合类 | 3414篇 |
现状与发展 | 6篇 |
一般理论 | 2篇 |
预防医学 | 1663篇 |
眼科学 | 628篇 |
药学 | 2555篇 |
13篇 | |
中国医学 | 1015篇 |
肿瘤学 | 2274篇 |
出版年
2024年 | 70篇 |
2023年 | 332篇 |
2022年 | 803篇 |
2021年 | 1073篇 |
2020年 | 855篇 |
2019年 | 740篇 |
2018年 | 856篇 |
2017年 | 715篇 |
2016年 | 711篇 |
2015年 | 1028篇 |
2014年 | 1346篇 |
2013年 | 1139篇 |
2012年 | 1825篇 |
2011年 | 1872篇 |
2010年 | 1091篇 |
2009年 | 925篇 |
2008年 | 1334篇 |
2007年 | 1302篇 |
2006年 | 1297篇 |
2005年 | 1408篇 |
2004年 | 855篇 |
2003年 | 852篇 |
2002年 | 740篇 |
2001年 | 598篇 |
2000年 | 725篇 |
1999年 | 725篇 |
1998年 | 457篇 |
1997年 | 461篇 |
1996年 | 355篇 |
1995年 | 344篇 |
1994年 | 268篇 |
1993年 | 196篇 |
1992年 | 315篇 |
1991年 | 257篇 |
1990年 | 247篇 |
1989年 | 242篇 |
1988年 | 199篇 |
1987年 | 174篇 |
1986年 | 151篇 |
1985年 | 155篇 |
1984年 | 58篇 |
1983年 | 61篇 |
1982年 | 24篇 |
1981年 | 36篇 |
1979年 | 25篇 |
1978年 | 14篇 |
1974年 | 21篇 |
1973年 | 17篇 |
1972年 | 18篇 |
1969年 | 16篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
12.
作者利用交流电弧和光栅摄谱仪组装了能够绘制谱线轮廓曲线和准确测定谱线宽度的记录仪,用线宽增量法对生物材料(拟血清)中的主要成分Ca和微量元素Cu进行了测定。与黑度法相比,本实验结果的线性好,误差小,再现性有所提高。这些结果表明,用上述仪器装置和线宽增量法进行生物材料含量分析优于黑度法。 相似文献
13.
OBJECTIVES: Radiopacity is a desirable property for most intra-oral materials. There are established ISO and ANSI/ADA protocols for determining radiopacity using film-based radiography. However, these methods are not always followed by researchers. This study aims to adapt those procedures by using digital radiography, a simplified stepwedge, and examine the effects of target distance and exposure time choice. METHODS: One millimetre thick samples of three dental materials were prepared by placing the materials into a 1.00 mm thick washer sandwiched between two glass slides. The samples were digitally radiographed alongside a stepwedge of aluminum alloy 1100 with an X-ray unit at 70 kVp using five different target distance/exposure time combinations. For each combination, the grey scale values of various thicknesses of the stepwedge were converted into absorbencies and plotted against their thickness. These plots were then linearly regressed in order to correlate absorbance with a thickness of aluminum for each target distance/exposure time combination. The absorbencies of each sample were then converted into radiopacities using these correlations. RESULTS: The correlations between the absorbance of the stepwedge and its thickness were highly linear. This linearity allows the correlation to be accurately deduced from fewer data points than required by the ISO and ANSI/ADA protocols. Varying exposure time did not significantly affect the mean radiopacity measured at a target distance of 30 cm. Varying the target distance did not significantly affect the measured radiopacity as long as the samples were properly exposed. SIGNIFICANCE: A simplified, consistent digital method for determining radiopacity is presented. 相似文献
14.
准分子激光屈光性角膜切削术治疗近视及近视散光临床分析 总被引:2,自引:2,他引:0
目的评价准分子激光屈光性角膜切削术治疗近视及近视散光的临床效果。方法应用准分子激光(NIDEKEC—5000型)治疗24D以下.伴或不件5D以内散光的近视眼。214只治疗眼随诊6个月以上。结果随诊1年以上的病例显示术后3个月屈光度及视力基本稳定。术后6个月时,在等值球镜度低于6D的治疗眼中,裸眼视力≥1.0者占92.04%,≥0.5为100%,80.53%的裸眼视力≥术前最佳矫正视力,99.12%的眼屈光度在预定矫正度数的±1.00D以内。低于10D的高度近视眼也有近似的疗效。214只治疗眼中操眼视力≥1.0者占78.97%,≥0.5为90.65%,72.43%的裸眼视力≥术前最佳矫正视力,88.32%的眼屈光度在预定矫正度数的±1.00D以内。6只眼(2.80%)最佳矫正视力减少2行以上,有Ⅱ级以上Haze的有7眼间(3.27%)。结论准分子激光屈光性角膜切削术治疗近视及近视散光具有很高程度的精确性和安全性,在<10D的近视眼中更显示了良好的预测性和稳定性。 相似文献
15.
拟定了一简单实用的测定人发中铁的催化分光光度法。在实验条件下,人发中常见的数10种微量元素均不干扰铁的测定,回收率达86~106%。 相似文献
16.
17.
18.
中山市各级政府切实加强妇幼卫生工作的领导,卫生部门主动开展工作,有关部门紧密配合,以提高人口素质为宗旨,抓重点、攻难点,始终把妇幼卫生工作的主要目标纳入各级政府社会经济发展目标管理,作为考核干部和政府工作的重要内容,使各项指标如期圆满完成。 相似文献
19.
Six human cytochrome P450s expressed in HepG2 cells using vaccinia virus cDNA-directed expression, were used to study the biotransformation of caffeine and its metabolites. CYP1A2 alone was responsible for caffeine 3-demethylation and paraxanthine 7-demethylation; in addition, 1A2 catalysed virtually all reactions related to caffeine and its metabolites. The metabolic profile of caffeine biotransformation by CYP1A2 averaged 81.5% for paraxanthine, 10.8% for theobromine and 5.4% for theophylline formation. It remained quite uniform when caffeine concentrations were varied. The most striking finding was that CYP2E1 (the ethanol-inducible form) had major influences upon caffeine metabolism: in particular, it catalysed the formation of theophylline and theobromine from caffeine. Thus, the in vivo metabolite profiling of caffeine may reveal CYP2E1 activities in addition to the previously documented activities of CYP1A2, polymorphic N-acetyltransferase and xanthine oxidase. 相似文献
20.
The survival rate and elastic properties of the anterior abdominal skin flap in Sprague-Dawley rats were studied in three groups of animals. In group 1 where the flaps were supplied by a normal artery, arterial flaps (1A) had better survival rate and elastic properties than venous flaps (1B). In group 2, where the flaps were supplied by an artery with diminished perfusion pressure, the arterial flaps (2A) still had slightly better results than venous flaps (2B). However, in group 3 where the flaps were supplied by a vein, venous flaps (3B) had better results than arterial flaps (3A). 相似文献