全文获取类型
收费全文 | 20793篇 |
免费 | 1998篇 |
国内免费 | 497篇 |
专业分类
耳鼻咽喉 | 53篇 |
儿科学 | 392篇 |
妇产科学 | 102篇 |
基础医学 | 1772篇 |
口腔科学 | 534篇 |
临床医学 | 2219篇 |
内科学 | 1787篇 |
皮肤病学 | 528篇 |
神经病学 | 1234篇 |
特种医学 | 950篇 |
外科学 | 812篇 |
综合类 | 3147篇 |
现状与发展 | 1篇 |
一般理论 | 11篇 |
预防医学 | 6128篇 |
眼科学 | 152篇 |
药学 | 1919篇 |
41篇 | |
中国医学 | 1197篇 |
肿瘤学 | 309篇 |
出版年
2024年 | 38篇 |
2023年 | 279篇 |
2022年 | 544篇 |
2021年 | 1021篇 |
2020年 | 886篇 |
2019年 | 720篇 |
2018年 | 661篇 |
2017年 | 743篇 |
2016年 | 778篇 |
2015年 | 803篇 |
2014年 | 1426篇 |
2013年 | 1556篇 |
2012年 | 1436篇 |
2011年 | 1696篇 |
2010年 | 1202篇 |
2009年 | 1001篇 |
2008年 | 974篇 |
2007年 | 991篇 |
2006年 | 863篇 |
2005年 | 728篇 |
2004年 | 616篇 |
2003年 | 539篇 |
2002年 | 438篇 |
2001年 | 422篇 |
2000年 | 310篇 |
1999年 | 262篇 |
1998年 | 259篇 |
1997年 | 218篇 |
1996年 | 195篇 |
1995年 | 171篇 |
1994年 | 179篇 |
1993年 | 131篇 |
1992年 | 136篇 |
1991年 | 131篇 |
1990年 | 96篇 |
1989年 | 110篇 |
1988年 | 86篇 |
1987年 | 79篇 |
1986年 | 59篇 |
1985年 | 93篇 |
1984年 | 67篇 |
1983年 | 57篇 |
1982年 | 60篇 |
1981年 | 46篇 |
1980年 | 33篇 |
1979年 | 40篇 |
1978年 | 21篇 |
1977年 | 21篇 |
1976年 | 17篇 |
1974年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
K. Brocks J. S.Jensen J. F. Schmidt B. Chræmmer Jørgensen 《Acta anaesthesiologica Scandinavica》1987,31(5):448-449
Forty women, aged 26-40 years, were investigated with regard to gastric contents and pH before general anaesthesia. The patients were divided into two groups (20 in each). Group 100 received 0.3 mg kg-1 diazepam orally with 100 ml of water 2 h before surgery. Group 50 received 0.3 mg kg-1 diazepam with 50 ml of water 2 h before surgery. The amount of gastric content was significantly greater in Group 100 than in Group 50 (P less than 0.05). There was no statistical difference in pH values between the groups. The number of patients with both gastric pH less than 2.5 and gastric volume greater than 25 ml was significantly higher in Group 100 compared to Group 50 (P less than 0.05). We cannot recommend the use of oral premedication using these amounts of water, considering the increased risk of aspiration of gastric contents. 相似文献
62.
63.
S. M. Fuchs C. Heinemann S. Schliemann-Willers H. Härtl J. W. Fluhr P. Elsner 《Skin research and technology》2006,12(4):223-227
OBJECTIVE: In the present study, we evaluated the anti-inflammatory activity of Poria cocos (PoCo) on experimentally induced irritant contact dermatitis (ICD) in a repeated sodium lauryl sulphate (SLS) irritation model. METHODS: The anti-irritative effect of PoCo was evaluated with a visual score and quantified by non-invasive bioengineering methods, namely chromametry and transepidermal water loss. Three concentrations of PoCo in base cream DAC (amphiphilic emollient; German pharmacopoeia) were tested in a 4-day repetitive irritation test using SLS. RESULTS: A statistically significant anti-inflammatory activity was observed for PoCo by all three methods when applied in parallel to the induction period of ICD. Application of PoCo after induction of ICD once a day for 5 days, starting just at the end of 4 days, was without any effect. CONCLUSION: An anti-inflammatory efficacy of PoCo on the elicitation phase of the ICD induced by repeated SLS test could be observed and quantified by three independent, non-invasive biophysical assessment parameters. This effect can be explained by its influence on pro-inflammatory enzymes, namely phospholipase A2. 相似文献
64.
Keiichiro Yoshinaga Chietsugu Katoh Kazuyuki Noriyasu Yasuyoshi Iwado Hideto Furuyama Yoshinori Ito Yuji Kuge Tetsuro Kohya Akira Kitabatake Nagara Tamaki 《Journal of nuclear cardiology》2003,10(3):275-283
BACKGROUND: Myocardial perfusion single photon emission computed tomography (SPECT) occasionally fails to detect coronary stenosis in patients with coronary artery disease (CAD). We evaluated coronary flow reserve (CFR) using oxygen 15-labeled water in areas with and without ischemia on technetium 99m tetrofosmin stress perfusion SPECT in patients with angiographically documented CAD. METHODS AND RESULTS: Twenty-seven patients with CAD and eleven age-matched normal subjects were studied. Baseline myocardial blood flow (MBF) and MBF during hyperemia induced by intravenous adenosine triphosphate infusion (0.16 mg. kg(-1). min(-1)) were determined with the use of O-15-labeled water positron emission tomography, and the CFR was calculated. Tc-99m tetrofosmin stress/rest SPECT was performed for comparison. On the basis of the results of coronary angiography and SPECT, coronary segments were divided into 3 types: segments with coronary stenosis and a perfusion abnormality on stress SPECT imaging (group A, n = 16), segments with coronary stenosis without a perfusion abnormality (group B, n = 42), and remote segments with no coronary stenosis or perfusion abnormality (group C, n = 18). Baseline MBF values were similar among the 3 groups. CFR in group A was lower (1.82 +/- 0.54) than in group B (2.22 +/- 0.87, P <.05), in group C (2.92 +/- 1.21, P <.01), and in normal segments (3.86 +/- 1.24, P <.001). CFR in group B was lower than in group C (P <.02) and in normal segments (P <.001). CFR in group C was lower than in normal segments (P <.02). CONCLUSIONS: Areas with a perfusion abnormality on stress SPECT had reduced CFR. In the areas without a perfusion abnormality and with coronary stenosis, lowering of CFR was intermediate between the areas with a perfusion abnormality and remote segments. Moreover, CFR was slightly, but significantly, lower in remote segments in patients with CAD compared with normal segments. 相似文献
65.
目的探讨不同视场角参数对虚拟环境中目标判断的影响规律 ,找出最佳视场角参数。方法利用自行研制基于PC平台的虚拟现实 (VR)实验系统 ,选定 45名年龄在 2 3~ 5 8岁被试者并完成大小与角度判断的实验设计。首先进行 30 0人次的预实验 ,确定引起虚拟环境中目标判断差错的视场角及相应观察任务的差别等级 ,然后开始单因素、4水平的完全随机正式实验。结果方差分析表明 ,不同的虚拟环境视场角对目标判断的真实性有显著性影响 ,当视场角为 60°时 ,目标判断的正确率最大。结论利用VR技术进行载人航天器工效设计、操作训练或其它任务的研究时 ,应考虑视场角的作用 ,适合目标大小判断的视场角参数值宜取 60°,以便获得最大的工效 相似文献
66.
低张结肠水灌肠CT检查诊断结肠癌的价值 总被引:3,自引:0,他引:3
目的 :探讨低张结肠水灌肠CT检查对结肠癌的CT表现及诊断价值。材料和方法 :肌注 65 4 2 2 0mg后 ,结肠灌注微温生理盐水进行CT扫描。分析经手术病理证实的 3 8例结肠癌资料。结果 :CT显示肿瘤部位准确率为 10 0 % ,CT分期与手术分期符合率为 92 % ,低张结肠水灌肠CT可见病变肠壁增厚、突出腔内的肿块、肠腔狭窄及其浆膜面毛糙 ;可见结肠癌侵犯邻近器官、淋巴结肿大及远处转移。结论 :低张结肠水灌肠CT检查对结肠癌的术前诊断有很大的价值。 相似文献
67.
Hanzhang Lu Xavier Golay James J Pekar Peter C M Van Zijl 《Magnetic resonance in medicine》2003,50(2):263-274
During brain activation, local control of oxygen delivery is facilitated through microvascular dilatation and constriction. A new functional MRI (fMRI) methodology is reported that is sensitive to these microvascular adjustments. This contrast is accomplished by eliminating the blood signal in a manner that is independent of blood oxygenation and flow. As a consequence, changes in cerebral blood volume (CBV) can be assessed through changes in the remaining extravascular water signal (i.e., that of parenchymal tissue) without need for exogenous contrast agents or any other invasive procedures. The feasibility of this vascular space occupancy (VASO)-dependent functional MRI (fMRI) approach is demonstrated for visual stimulation, breath-hold (hypercapnia), and hyperventilation (hypocapnia). During visual stimulation and breath-hold, the VASO signal shows an inverse correlation with the stimulus paradigm, consistent with local vasodilatation. This effect is reversed during hyperventilation. Comparison of the hemodynamic responses of VASO-fMRI, cerebral blood flow (CBF)-based fMRI, and blood oxygenation level-dependent (BOLD) fMRI indicates both arteriolar and venular temporal characteristics in VASO. The effect of changes in water exchange rate and partial volume contamination with CSF were calculated to be negligible. At the commonly-used fMRI resolution of 3.75 x 3.75 x 5 mm(3), the contrast-to-noise-ratio (CNR) of VASO-fMRI was comparable to that of CBF-based fMRI, but a factor of 3 lower than for BOLD-fMRI. Arguments supporting a better gray matter localization for the VASO-fMRI approach compared to BOLD are provided. 相似文献
68.
在贵州省安顺市1985年水型伤寒爆发流行后,为调查该市环境中沙门氏菌污染情况,我站于1986~1988年对市区所属医院和贯城河污水及部分食物的沙门氏菌进行了监测,共采集污水及食品619份,沙门氏菌阳性率为41.84%,分属A、B、C、D、E1五个群12个血清型,伤寒沙门氏菌经Vi噬菌体分型为M1型。纸片药敏试验为多重性耐药菌株。阐明了沙门氏菌流行的部分传播媒介途径。 相似文献
69.
An indirect competitive ELISA was developed for the quantitative analysis of aldrin/dieldrin. This has been used to monitor the levels of these pesticides in water samples collected in Egypt. The detection range of the aldrin/dieldrin assay in water was 5–10 ppm without enhancement. River Nile water samples and tap water samples (n = 25) were collected from 25 stations in 16 different governorates in Egypt. Pesticides were detected in 10 of the 25 Nile water samples (40%) at levels from 10 to 110 ppb. In tap water samples, pesticides were not detected at levels greater than the lower limit of the assay. The technique described provides a rapid, economical, highly sensitive and specific method of analysis that is relatively simple to perform and interpret. It will be extremely useful in monitoring levels of pesticides in water used for human consumption. 相似文献
70.