全文获取类型
收费全文 | 69248篇 |
免费 | 6274篇 |
国内免费 | 5069篇 |
专业分类
耳鼻咽喉 | 400篇 |
儿科学 | 720篇 |
妇产科学 | 876篇 |
基础医学 | 8719篇 |
口腔科学 | 1186篇 |
临床医学 | 9278篇 |
内科学 | 10556篇 |
皮肤病学 | 766篇 |
神经病学 | 3647篇 |
特种医学 | 2409篇 |
外国民族医学 | 41篇 |
外科学 | 7069篇 |
综合类 | 11942篇 |
现状与发展 | 17篇 |
一般理论 | 2篇 |
预防医学 | 4256篇 |
眼科学 | 1825篇 |
药学 | 7356篇 |
74篇 | |
中国医学 | 3678篇 |
肿瘤学 | 5774篇 |
出版年
2024年 | 225篇 |
2023年 | 1196篇 |
2022年 | 2848篇 |
2021年 | 3591篇 |
2020年 | 2597篇 |
2019年 | 2382篇 |
2018年 | 2383篇 |
2017年 | 2045篇 |
2016年 | 2052篇 |
2015年 | 3132篇 |
2014年 | 3935篇 |
2013年 | 3265篇 |
2012年 | 4784篇 |
2011年 | 5665篇 |
2010年 | 3269篇 |
2009年 | 2479篇 |
2008年 | 3432篇 |
2007年 | 3515篇 |
2006年 | 3608篇 |
2005年 | 3444篇 |
2004年 | 2234篇 |
2003年 | 2196篇 |
2002年 | 1831篇 |
2001年 | 1685篇 |
2000年 | 1768篇 |
1999年 | 1966篇 |
1998年 | 1251篇 |
1997年 | 1342篇 |
1996年 | 1007篇 |
1995年 | 888篇 |
1994年 | 768篇 |
1993年 | 488篇 |
1992年 | 602篇 |
1991年 | 520篇 |
1990年 | 446篇 |
1989年 | 393篇 |
1988年 | 324篇 |
1987年 | 283篇 |
1986年 | 249篇 |
1985年 | 173篇 |
1984年 | 102篇 |
1983年 | 71篇 |
1982年 | 38篇 |
1981年 | 52篇 |
1980年 | 28篇 |
1979年 | 38篇 |
1963年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
This paper examines two approaches for the analysis of quantitative traits: (1) association studies and (2) linkage studies. The trait studied was Q1 from simulated Problem 2 data set in Genetic Analysis Workshop 9. Our purpose was to evaluate associations present in the data, to identify nongenetic and genetic predictors of the trait, and to explore the simulated genome for linkage. Through the association study, we found evidence for the primary major gene associated with this trait. The linkage study found evidence of residual genetic effect acting through other traits. Adjustments of Q1 for Q2 and Q3 led to a failure to find significant effects of MG2 and MG3. This supports the suggestion that adjustment for genetically influenced traits for effects of other genetic traits can reduce the power to detect major gene effects. In summary, we detected the major gene directly associated with the trait of interest through association studies. Linkage analysis detected evidence for two other genes associated to a lesser degree with the trait. © 1995 Wiley-Liss, Inc. 相似文献
52.
自身练习护理操作就是以护生作为练习对象,相互间在各自身上完成注射、输液等操作练习项目,以达到教学要求[1]。在基础护理的教学中,自身练习对于调动护生的参与感,增加真实感,满足成就感方面起着十分重要的作用。但是,也必须看到在积极效果背后的种种矛盾以及由这些矛盾可能导 相似文献
53.
On the basis of the common occurrence of high concentration of estrogen and activated macrophages in patients with endometriosis, we postulate that interaction between 17beta-estradiol and macrophage may be an important affair in endometriosis. So our study was focused on the effect of 17beta-estradiol on macrophage. First morphology of macrophages was examined with environmental scanning electron microscopy. Increased size, extension of more microvilli, expression of retraction fibers and elaboration of membrane ruffles were detected in 17beta-estradiol treated macrophages. Then Nitrate and nitrite level in the supernatant was measured by the method of Griess and iNOS expression was analyzed using immunohistochemical staining. It showed that 17beta-estradiol could induce NO release from peritoneal macrophages and expression of iNOS was increased. Also more TNF-alpha in supernatant that was measured by MTT via L929 cell was produced by macrophages under the inducing of 17beta-estradiol. Furthermore, [Ca2+]i, which was viewed by microscope in a laser scanning confocal unit, elevated 39.8% in peritoneal macrophages after 17beta-estradiol 100 nmol/L treated. The results above demonstrated that peritoneal macrophage had been activated in both morphology and cytokine line when interaction with 17beta-estradiol, which indicated that macrophage activated by 17beta-estradiol might play a permission role in development of endometriosis. 相似文献
54.
脑梗塞患者血清叶酸维生素B12浓度与同型半胱氨酸及血脂水平的研究 总被引:1,自引:0,他引:1
目的探讨本地区脑梗塞患者的血清叶酸、维生素B12(VitB12)与同型半胱氨酸(Hcy)水平及血脂水平的关系。方法应用全自动化学发光免疫法测定115例脑梗塞患者血清叶酸、维生素B12水平,采用荧光定量分析法测定血清同型半胱氨酸水平,采用免疫比浊法测定血脂水平。结果脑梗塞患者血清叶酸水平明显低于对照组(P〈0.001),血清Hcy及甘油三酯(TG)水平明显高于对照组(P〈0.01),而维生素B12及其余所测血脂指标与健康对照组无显著差异(P〉0.05)。结论即时监测血清叶酸、Hcy及TG水平,适当补充叶酸,可早期预防和及时治疗脑血管疾病,降低脑梗塞的发生率及复发率。 相似文献
55.
近期一项调查研究显示,出现勃起功能障碍的老年健康男子可能存在隐性心血管疾病。共有8063名55岁以上无心血管疾病的美国男子参加了该项队列研究,试验初始时4247人具有正常勃起功能。 相似文献
56.
Exogenous advanced glycosylation end products induce diabetes-like vascular dysfunction in normal rats: a factor in diabetic retinopathy 总被引:2,自引:0,他引:2
Xun Xu Zhiping Li Dawei Luo Yufeng Huang Jianfeng Zhu Xiaojue Wang Honghui Hu C. Patrick 《Albrecht von Graefes Archiv fur klinische und experimentelle Ophthalmologie》2003,241(1):56-62
BACKGROUND. Diabetic retinopathy has been shown to be directly associated with the degree and duration of hyperglycemia, and advanced glycosylation end products (AGEs) have been implicated in this pathological process. The purpose of the experiments reported here was to study the effect of AGE deposition on retinal vascular damage which leads to diabetic retinopathy. METHODS. Intravenous injection of exogenous AGEs was used to treat wild-type non-diabetic Sprague-Dawley rats. One of the two retinal slides from each animal was treated using immunohistochemical staining to label retinal vascular AGE deposition, the other H&E staining for counting of capillary pericytes. The results were compared with the findings in untreated wild-type and diabetic controls and in rats treated with unmodified rat serum albumin (RSA). RESULTS. After 2 weeks of continuous treatment, AGEs were identified in the retinal vascular tissue of the AGE-RSA-injected group. The average number of retinal capillary pericytes per 10x100 microscope power field was 4.313+/-0.34 (mean +/- SD) in the AGE-RSA-injected group, compared with 5.798+/-0.481 in the control group ( P<0.01). CONCLUSION. These experiments demonstrate that AGEs, independent of other metabolic factors, can induce vascular change resembling that of diabetic retinopathy. 相似文献
57.
Elizabeth R Seaquist Wei Chen Luke E Benedict Kamil Ugurbil Jae-Hwan Kwag Xiao-Hong Zhu Charles A Nelson 《Journal of cerebral blood flow and metabolism》2007,27(1):154-160
Functional magnetic resonance imaging (fMRI) based on blood oxygen level-dependent (BOLD) contrast has become an invaluable tool in the assessment of in vivo neuronal activation. Quantification of the BOLD response is determined by the hemodynamic and metabolic changes that occur in response to brain stimulation. However, these changes may vary by changes in insulin, a hormone known to be vasoactive in some tissues. To determine if insulin has an effect on fMRI, we measured the BOLD response to a visual stimulus in five normal volunteers in which insulin was first suppressed and then brought to a high physiological concentration. In addition, we also examined the effect of insulin on activation of the visual cortex as measured by the visual-evoked potential (VEP). We found that the BOLD response measured in the presence of insulin (serum insulin=236+/-29 pmol/L) was significantly lower (P<0.001) than that measured in its absence (serum insulin=8+/-2 pmol/L). Insulin was without effect on P100 amplitude or latency acquired in the presence or absence of insulin in 28 subjects using the same stimulus as that used for the fMRI experiments. Our observations suggest that insulin may have effects on cerebral blood flow and/or metabolism that affect the BOLD signal that are independent of its effects on neuronal activation identified by event related potentials (ERP). These findings highlight the complexity that must be considered when interpreting differences in fMRI responses between groups of subjects that differ in insulin concentration and/or insulin sensitivity. 相似文献
58.
We present a correspondence-based system for visual object recognition with invariance to position, orientation, scale and deformation. The system is intermediate between high- and low-dimensional representations of correspondences. The essence of the approach is based on higher-order links, called here maplets, which are specific to narrow ranges of mapping parameters (position, scale and orientation), which interact cooperatively with each other, and which are assumed to be formed by learning. While being based on dynamic links, the system overcomes previous problems with that formulation in terms of speed of convergence and range of allowed variation. We perform face recognition experiments, comparing ours to other published systems. We see our work as a step towards a reformulation of neural dynamics that includes rapid network self-organization as essential aspect of brain state organization. 相似文献
59.
以健康Wistar大白鼠为材料,对微波快速内源性过氧化物酶染色与灌注法显示微血管的方法进行了对比研究。结果,过氧化物酶组织化学法具有不用灌注,操作简单,所用时间短,对血管无扩张、破裂等人为改变的特点,保持了微血管真实的自然形态和管径大小,可以定量或半定量地判定组织器官活体时的血液循环状况。可以用于人及动物的大脑、脊髓、皮肤、耳及食管等组织内微血管形态学研究和定量分析。并对过氧化物酶显示微血管的原理和微波辐射促进染色的原理及特点进行了分析、讨论。 相似文献
60.
We determined the serum levels of the creatine kinase B subunit (CK-B) by an enzyme immunoassay method in patients with renal cell carcinoma (RCC) and benign renal diseases. Eighteen of 76 patients with RCC (24%) had elevated serum CK-B levels. The positive rates were 29% in stage I, 13% in stage II, 15% in stage III, and 27% in stage IV. In all 9 patients whose serum CK-B levels were serially measured and had been elevated before operation, the CK-B levels were reduced to the normal range after nephrectomy. These findings indicate that serum CK-B is a useful biomarker for monitoring the clinical course for a limited number of RCC patients, but is not a marker for diagnosis and staging. Concentrations of CK-B in RCC tissues were significantly lower than those of normal kidney. A high rate of cell turnover in tumor tissues might entail the higher level of serum CK-B in patients with RCC. 相似文献