全文获取类型
收费全文 | 141207篇 |
免费 | 9607篇 |
国内免费 | 3087篇 |
专业分类
耳鼻咽喉 | 1729篇 |
儿科学 | 3325篇 |
妇产科学 | 4358篇 |
基础医学 | 21110篇 |
口腔科学 | 3928篇 |
临床医学 | 12383篇 |
内科学 | 25127篇 |
皮肤病学 | 2639篇 |
神经病学 | 9512篇 |
特种医学 | 4995篇 |
外国民族医学 | 23篇 |
外科学 | 18786篇 |
综合类 | 8705篇 |
现状与发展 | 5篇 |
一般理论 | 38篇 |
预防医学 | 10065篇 |
眼科学 | 3609篇 |
药学 | 12653篇 |
33篇 | |
中国医学 | 2214篇 |
肿瘤学 | 8664篇 |
出版年
2022年 | 1550篇 |
2021年 | 2289篇 |
2020年 | 1557篇 |
2019年 | 1898篇 |
2018年 | 2503篇 |
2017年 | 1893篇 |
2016年 | 1908篇 |
2015年 | 2437篇 |
2014年 | 3251篇 |
2013年 | 3548篇 |
2012年 | 5186篇 |
2011年 | 5516篇 |
2010年 | 3345篇 |
2009年 | 2938篇 |
2008年 | 4475篇 |
2007年 | 4692篇 |
2006年 | 4751篇 |
2005年 | 4210篇 |
2004年 | 3644篇 |
2003年 | 3480篇 |
2002年 | 3211篇 |
2001年 | 7167篇 |
2000年 | 7466篇 |
1999年 | 6232篇 |
1998年 | 2178篇 |
1997年 | 1741篇 |
1996年 | 1199篇 |
1995年 | 1111篇 |
1992年 | 3912篇 |
1991年 | 3939篇 |
1990年 | 3666篇 |
1989年 | 3646篇 |
1988年 | 3526篇 |
1987年 | 3362篇 |
1986年 | 3164篇 |
1985年 | 3034篇 |
1984年 | 2079篇 |
1983年 | 1819篇 |
1982年 | 1006篇 |
1979年 | 1939篇 |
1978年 | 1198篇 |
1977年 | 1000篇 |
1975年 | 1211篇 |
1974年 | 1393篇 |
1973年 | 1440篇 |
1972年 | 1377篇 |
1971年 | 1269篇 |
1970年 | 1160篇 |
1969年 | 1152篇 |
1968年 | 1047篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
31.
32.
目的利用红外光谱法测定延安大学附属医院泌尿外科手术获得的泌尿系结石成分,探讨延安地区泌尿系结石成分与年龄、性别等关系,比较上、下尿路结石成分特点,分析延安地区泌尿系结石发生的流行病学情况,为临床制定有效的个体化治疗及预防措施提供参考依据。方法收集2013年1月至2017年1月在延安大学附属医院泌尿外科治疗1984例尿路结石患者的年龄、性别、结石部位等临床资料,对比分析延安地区泌尿系结石在不同年龄、不同性别、不同解剖部位的分布特点。结果在1984例泌尿系结石的患者中,按每10岁年龄大小分组排序,统计各年龄阶段泌尿系结石发病情况,男性患者有1346例,女性患者有638例,男性年龄(50.23±14.48)岁,女性年龄(47.87±14.51)岁,男、女患者比例约2.11∶1。在66~75岁年龄段,尿路结石发病率性别差异具有统计学意义(P<0.05)。结石成分以混合性结石为主,以混合性结石为主,共1582例,占79.76%。其中1665例(83.92%)为上尿路结石,上、下尿路结石的比例为5.22∶1,其余为肾结石合并膀胱结石。上尿路结石中男性1062例,女性603例,男女比例为1.76∶1;下尿路结石中男性284例,女性35例,男女比例为8.11∶1。青壮年(年龄≤45岁)泌尿系结石患者草酸钙为主结石、感染性结石多见;中老年(年龄>45岁)泌尿系结石者草酸钙为主结石、尿酸类结石多见。感染性结石患者性别差异具有统计学意义(P<0.05)。结论在延安地区男性较女性更容易患泌尿系结石。同时,不同年龄段结石构成成分具有差异。对于年龄≤45岁患者,主要以草酸钙为主结石、感染性结石多见,这与结石整体发病率基本一致;而对于年龄>45岁患者,主要以草酸钙为主结石、尿酸性结石多见。表明对于不同年龄段的结石患者,可以根据上述结果在结石的预防和治疗上综合考量,给予明确而更加合理的治疗。 相似文献
33.
34.
35.
36.
J. Yang S. Gohel Z. Zhang V. Hatzoglou A.I. Holodny B.A. Vachha 《AJNR. American journal of neuroradiology》2021,42(3):551
BACKGROUND AND PURPOSE:Cognitive challenges are prevalent in survivors of glioma, but their neurobiology is incompletely understood. The purpose of this study was to investigate the effect of glioma presence and tumor characteristics on resting-state functional connectivity and amplitude of low-frequency fluctuations of the salience network, a key neural network associated with cognition.MATERIALS AND METHODS:Sixty-nine patients with glioma (mean age, 48.74 [SD, 14.32] years) who underwent resting-state fMRI were compared with 31 healthy controls (mean age, 49.68 [SD, 15.54] years). We identified 4 salience network ROIs: left/right dorsal anterior cingulate cortex and left/right anterior insula. Average salience network resting-state functional connectivity and amplitude of low-frequency fluctuations within the 4 salience network ROIs were computed.RESULTS:Patients with gliomas showed decreased overall salience network resting-state functional connectivity (P = .001) and increased amplitude of low-frequency fluctuations in all salience network ROIs (P < .01) except in the left dorsal anterior cingulate cortex. Compared with controls, patients with left-sided gliomas showed increased amplitude of low-frequency fluctuations in the right dorsal anterior cingulate cortex (P = .002) and right anterior insula (P < .001), and patients with right-sided gliomas showed increased amplitude of low-frequency fluctuations in the left anterior insula (P = .002). Anterior tumors were associated with decreased salience network resting-state functional connectivity (P < .001) and increased amplitude of low-frequency fluctuations in the right anterior insula, left anterior insula, and right dorsal anterior cingulate cortex. Patients with high-grade gliomas had decreased salience network resting-state functional connectivity compared with healthy controls (P < .05). The right anterior insula showed increased amplitude of low-frequency fluctuations in patients with grade II and IV gliomas compared with controls (P < .01).CONCLUSIONS:By demonstrating decreased resting-state functional connectivity and an increased amplitude of low-frequency fluctuations related to the salience network in patients with glioma, this study adds to our understanding of the neurobiology underpinning observable cognitive deficits in these patients. In addition to more conventional functional connectivity, amplitude of low-frequency fluctuations is a promising functional-imaging biomarker of tumor-induced vascular and neural pathology.Detrimental effects of cancer on cognitive function and, consequently, on the quality of life are emerging as a key focus of cancer survivorship both in research and clinical practice.1,2 Brain tumors have been shown to affect memory, processing, and attention in patients; however, their underlying neurobiology is incompletely understood.3 Using resting-state functional MR imaging (rsfMRI) to evaluate changes in cognitive resting-state networks may provide a better understanding of the pathology underlying the observable cognitive disruptions in gliomas, the most common primary brain tumor in adults.A “triple network model” of neurocognitive pathology has been proposed, which encompasses the default mode network, involved in mind wandering; the central executive network, involved in decision-making; and the salience network (SN), implicated in modulating activation of the default mode network and central executive network by detecting the presence of salient stimuli.4-8 While previous rsfMRI research has largely focused on tumor-induced changes in the default mode network,9,10 our study examined the less-studied SN, a network rooted in the anterior insula and the dorsal anterior cingulate cortex.6Prior studies evaluating gliomas and SN resting-state functional connectivity (RSFC) provided conflicting results in small patient samples: Maesawa et al10 found no significant differences in the SN in 12 patients, while Liu et al11 more recently found decreased SN connectivity in 13 patients. Gliomas impact the integrity of the neurovascular unit to varying degrees, resulting in neurovascular uncoupling that has been reported to confound fMRI interpretations in patients with brain tumors.12-14 Additionally, research has reported neuronal plasticity manifested by structural reorganization and functional remodeling of neural networks in patients with gliomas with possible alterations in clinically observable cognitive manifestations.15-17 An rsfMRI metric, the amplitude of low-frequency fluctuations (ALFF), has recently shown promise as a biomarker for brain plasticity and hemodynamic characterization, including neurovascular uncoupling in patients with gliomas.15-19The purpose of this study was to investigate the effect of glioma presence and tumor characteristics on overall RSFC and regional normalized ALFF within the SN in a large patient population. We hypothesized that there would be decreased average SN RSFC and altered ALFF in patients with gliomas compared with healthy controls. Recent studies have acknowledged that gliomas have variable effects on network integrity based on lesion location and proximity to network ROIs,20-22 and unilateral gliomas can be associated with plasticity in both the ipsilateral and contralateral hemispheres.11,17 Research also supports differences in resting-state network reorganization in aggressive high-grade gliomas compared with slower-growing low-grade gliomas.20,23 Therefore, we also hypothesized that there would be differences in average SN RSFC and regional ALFF in patients based on the anterior-versus-posterior location, hemispheric side, and grade of glioma. 相似文献
37.
38.
39.
The significance of hepatobiliary scintigraphy (HBS) for hepatic graft function assessment was established mostly on retrospective studies and was not widely recognized due to the lack of quantitative data and variation in accuracy. This prospective study was performed to investigate the effectiveness of quantitative HBS for assessing hepatocyte dysfunction and biliary complication in liver transplant recipients.In 57 recipients who had undergone orthotopic liver transplantation, a total of 67 dynamic 99mTc-EHIDA scans were performed and quantitative parameters including the hepatocyte extraction fraction (HEF), time to maximum hepatic radioactivity (Tmax), and time for peak activity to decrease by 50% (T1/2) were calculated. The scintigraphic results based on the 3 parameters were compared against the final diagnosis. A ROC curve analysis was carried out to identify the cutoff value of Tmax for diagnosis of biliary stricture. Correlation between the parameters of postoperative HBS and conventional biochemical liver function indices were also analyzed.Quantitative 99mTc-EHIDA HBS had an overall sensitivity of 94.12% (16/17), specificity of 93.33% (42/45), and diagnostic accuracy of 93.55% (58/62) for detecting hepatocyte dysfunction and biliary complication in liver transplant recipients. The recommended cutoff value of Tmax for diagnosis of post-transplant biliary stricture was set at 15.75 min with a sensitivity of 100.0% and a specificity of 94.0%. The scintigraphic parameters (HEF, Tmax) were statistically significantly associated with the conventional liver function parameters.Quantitative 99mTc-EHIDA HBS offers a noninvasive imaging modality with high sensitivity and specificity to diagnose hepatocyte dysfunction as well as distinguish between patients with or without biliary stricture following liver transplantation. Furthermore, HEF and Tmax values obtained from dynamic HBS show good correlation with conventional liver function parameters. 相似文献
40.
Primary syphilis in HIV‐negative patients is on the rise in Greece: epidemiological data for the period 2005–2012 from a tertiary referral centre in Athens,Greece
下载免费PDF全文
![点击此处可从《Journal of the European Academy of Dermatology and Venereology》网站下载免费的PDF全文](/ch/ext_images/free.gif)