首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   6180篇
  免费   306篇
  国内免费   16篇
耳鼻咽喉   99篇
儿科学   409篇
妇产科学   73篇
基础医学   579篇
口腔科学   101篇
临床医学   419篇
内科学   1388篇
皮肤病学   178篇
神经病学   357篇
特种医学   194篇
外科学   1049篇
综合类   130篇
一般理论   3篇
预防医学   270篇
眼科学   300篇
药学   457篇
中国医学   18篇
肿瘤学   478篇
  2023年   47篇
  2022年   72篇
  2021年   226篇
  2020年   106篇
  2019年   139篇
  2018年   182篇
  2017年   127篇
  2016年   134篇
  2015年   160篇
  2014年   232篇
  2013年   275篇
  2012年   440篇
  2011年   457篇
  2010年   273篇
  2009年   188篇
  2008年   335篇
  2007年   348篇
  2006年   342篇
  2005年   329篇
  2004年   281篇
  2003年   232篇
  2002年   218篇
  2001年   96篇
  2000年   70篇
  1999年   81篇
  1998年   51篇
  1997年   43篇
  1996年   41篇
  1995年   39篇
  1994年   25篇
  1993年   27篇
  1992年   87篇
  1991年   63篇
  1990年   49篇
  1989年   62篇
  1988年   49篇
  1987年   43篇
  1986年   52篇
  1985年   41篇
  1984年   34篇
  1983年   21篇
  1981年   21篇
  1979年   33篇
  1977年   20篇
  1976年   33篇
  1975年   23篇
  1972年   21篇
  1971年   23篇
  1970年   28篇
  1969年   27篇
排序方式: 共有6502条查询结果,搜索用时 31 毫秒
991.
The failure to consider access to food resources in an integrated way may lead to inequalities in nutritional opportunities among populations. Working with community groups and other public agencies, the San Francisco Department of Public Health has led interagency food system planning in San Francisco, California, since 2002. We report on one of the interventions within that initiative-a partnership between a public health agency, a local nonprofit organization, and the local food stamp program to institutionalize improved access to farmers' markets for federal food assistance beneficiaries. We further report on monitoring data collected at farmers' markets that documents significant and sustained increases of utilization by food stamp recipients since the initial intervention.  相似文献   
992.
This study evaluates commercially available rK39 immunochromatographic strips using urine for diagnosis of visceral leishmaniasis (VL). Freshly collected urine and serum samples of 280 parasitologically confirmed VL patients and 66 endemic healthy controls (EHC), 48 nonendemic healthy controls (NEHC) and 45 different diseases were tested with rK39 strips. The sensitivity of rK39 in urine was 96.4% while the specificity was low varying from 66.7% in EHC, 77.08% in NEHC to 62.2% in different diseases. With serum, sensitivity was 100% whereas the specificity was 100%, 92.4% and 95.55% for the respective control groups. In the present format, the immunochromatographic strips cannot be used for the diagnosis of VL using urine samples.  相似文献   
993.

Background:

Anomalous origin of the left coronary artery from the pulmonary artery (ALCAPA) is a rare congenital coronary abnormality associated with early infant mortality and adult sudden death. As it predominantly presents in the first year of life, diagnosis in living adults is extremely rare. Current management is based on limited case series or extrapolated from pediatric cases. Modern advances in noninvasive cardiac imaging have substantially increased the number of diagnoses, uncovering a large adult population that has not been reviewed.

Hypothesis:

The availability of newer diagnostic modalities correlates with an increasing incidence in an older cohort, and true association between sudden death and ALCAPA may be lower, especially among older patients.

Methods:

A comprehensive literature search was performed for all case reports of ALCAPA on MEDLINE and PubMed using the keywords ALCAPA, Bland‐White‐Garland, and coronary anomaly; and augmented by references from published case reports from 1908 to 2008. All adult cases, defined by age 18 years and older, were reviewed for this article.

Results:

One hundred fifty‐one adult cases of ALCAPA are described, in addition to the case of an asymptomatic 53‐year‐old woman. The average reported age was 41 years old with the oldest being 83. Sixty‐six percent of the patients presented with symptoms of angina, dyspnea, palpitations, or fatigue; 17% presented with ventricular arrhythmia, syncope, or sudden death; and 14% were asymptomatic. Twelve percent were diagnosed at autopsy. The majority had some form of surgical correction during their clinical course.

Conclusions:

ALCAPA is a rare and life‐threatening condition in adults. The availability of newer, less invasive diagnostic modalities has resulted in more frequent identification of this condition in an older cohort. © 2011 Wiley Periodicals, Inc. The authors have no funding, financial relationships, or conflicts of interest to disclose.  相似文献   
994.

Aim

To evaluate the role of glycosylated hemoglobin (HbA1c) on the occurrence of sight-threatening diabetic retinopathy (STDR) in urban Chennai, Tamil Nadu, India.

Methods

A total of 5999 individuals were enumerated from the Chennai metropolis. Of these, 1414 subjects with diabetes were included for data analysis in the study. STDR or non-STDR groups were classified based on the fundus photographs. HbA1c was measured (Bio-Rad DiaSTAT™ HbA1c Reagent Kit) by the liquid chromatography technique.

Results

A statistically significant difference (p < 0.05) was noted in the duration of diabetes, gender, body mass index, HbA1c, micro- and macro-albuminuria between both non-STDR and STDR groups as compared to the no-diabetic retinopathy (DR) group. On multivariate analysis, HbA1c (non-STDR: odd's ratio OR = 1.23; 95% confidence interval CI = 1.15-1.32; p < 0.0001; STDR: OR = 1.31 95% CI = 1.14-1.52; p < 0.0001) was found to be significantly associated with non-STDR and STDR when compared with the no-DR group. The Receiver Operating Characteristic analysis showed that the cut-off value of 8.0 had 75.6% sensitivity and 58.2% specificity with 64.9% maximum area under the curve.

Conclusion

HbA1c value >8.0% was significantly related with STDR. In a screening programme, the cut-off value of HbA1c >8.0% provided a maximum yield of STDR.  相似文献   
995.
Six cases of sporotrichosis in Delhi (non-endemic area) were recorded in migrants from Uttarakhand over a period of one year (2008-2009). The clinico-epidemiological and mycological profile of the patients is discussed. These were confirmed by mycological culture, histopathological examination and/or remission of lesion with potassium iodide. Sporotrichosis is endemic in Uttarakhand, a north-western state in the sub-Himalayan region.  相似文献   
996.
997.
998.

Objective

To report our observations regarding fungal infections of the brain over two years from a large tertiary hospital in northern India. To identify fungal infections in immunocompetent and immunocompromised patients and to compare the two groups with respect to their age of occurrence, demographic data, clinical profile, radiological findings, response to treatment and outcome.

Methods

All consecutive cases of central nervous system (CNS) fungal infections admitted to the hospital over two years were included in this study. The patients were categorized as immunocompetent and immunocompromised, the predisposing factors, symptoms and clinical presentation were studied in detail and the outcomes of the two groups were compared.

Results

Of the 50 cases, 25(50%) were that of mucormycosis, 17(34%) were cryptococcosis and 8(16%) cases were that of aspergillosis. 14(28%) cases were immunocompetent and 36(72%) were immunocompromised. The outcome studied was as follows: 28% died of which 4% were HIV positive, 12% were diabetics with severe rhinorbital involvement, 2% had idiopathic thrombocytopenic purpura (ITP), 6% had advanced cancer and 4% had no predisposing illness.

Conclusions

We observed fungal infections of the brain in both immunocompetent and immunocompromised patients. In immunocompetent patients, early diagnosis and appropriate treatment frequently leads to recovery from the illness. The mortality and morbidity of fungal infections are less in the immunocompetent group of patients.  相似文献   
999.
Several homeoproteins can function in a direct cell non-autonomous fashion to control various biological processes. In the developing nervous system, this mode of signaling has been well documented for Engrailed in the guidance of retinal ganglion cell axons and retino-tectal patterning. Engrailed is also a key factor for mesencephalic dopaminergic (mDA) neurons, not only during development but also in the adult. Haplodeficiency for Engrailed1 leads to progressive adult-onset loss of mDA neurons and several phenotypic alterations reminiscent of Parkinson's disease (PD). Thanks to its transduction properties, Engrailed has been shown to confer neuroprotection in several experimental models of PD. Study of the mechanisms underlying these two Engrailed-mediated effects has revealed a key role of the translation regulation by Engrailed and uncovered an unsuspected link between a homeoprotein and mitochondrial activity. These studies highlight the crucial role of cellular energetic metabolism in neuron development, survival and neurodegeneration, and may help to identify novel therapeutic targets.  相似文献   
1000.
Alterations in the lipid composition of endosomal-lysosomal membranes may constitute an early event in Alzheimer's disease (AD) pathogenesis. In this study, we investigated the possibility that GM2 ganglioside accumulation in a mouse model of Sandhoff disease might be associated with the accumulation of intraneuronal and extracellular proteins commonly observed in AD. Our results show intraneuronal accumulation of amyloid-β peptide (Aβ)-like, α-synuclein-like, and phospho-tau-like immunoreactivity in the brains of β-hexosaminidase knock-out (HEXB KO) mice. Biochemical and immunohistochemical analyses confirmed that at least some of the intraneuronal Aβ-like immunoreactivity (iAβ-LIR) represents amyloid precursor protein C-terminal fragments (APP-CTFs) and/or Aβ. In addition, we observed increased levels of Aβ40 and Aβ42 peptides in the lipid-associated fraction of HEXB KO mouse brains, and intraneuronal accumulation of ganglioside-bound Aβ (GAβ) immunoreactivity in a brain region-specific manner. Furthermore, α-synuclein and APP-CTFs and/or Aβ were found to accumulate in different regions of the substantia nigra, indicating different mechanisms of accumulation or turnover pathways. Based on the localization of the accumulated iAβ-LIR to endosomes, lysosomes, and autophagosomes, we conclude that a significant accumulation of iAβ-LIR may be associated with the lysosomal-autophagic turnover of Aβ and fragments of APP-containing Aβ epitopes. Importantly, intraneuronal GAβ immunoreactivity, a proposed prefibrillar aggregate found in AD, was found to accumulate throughout the frontal cortices of postmortem human GM1 gangliosidosis, Sandhoff disease, and Tay-Sachs disease brains. Together, these results establish an association between the accumulation of gangliosides, autophagic vacuoles, and the intraneuronal accumulation of proteins associated with AD.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号