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   3398篇
  免费   190篇
  国内免费   27篇
耳鼻咽喉   15篇
儿科学   122篇
妇产科学   108篇
基础医学   453篇
口腔科学   57篇
临床医学   285篇
内科学   951篇
皮肤病学   55篇
神经病学   319篇
特种医学   85篇
外科学   253篇
综合类   6篇
一般理论   1篇
预防医学   160篇
眼科学   13篇
药学   317篇
中国医学   21篇
肿瘤学   394篇
  2024年   13篇
  2023年   23篇
  2022年   69篇
  2021年   93篇
  2020年   55篇
  2019年   70篇
  2018年   93篇
  2017年   71篇
  2016年   82篇
  2015年   100篇
  2014年   126篇
  2013年   163篇
  2012年   251篇
  2011年   273篇
  2010年   126篇
  2009年   152篇
  2008年   252篇
  2007年   223篇
  2006年   193篇
  2005年   219篇
  2004年   218篇
  2003年   155篇
  2002年   156篇
  2001年   37篇
  2000年   41篇
  1999年   39篇
  1998年   34篇
  1997年   33篇
  1996年   19篇
  1995年   17篇
  1994年   10篇
  1993年   10篇
  1992年   22篇
  1991年   19篇
  1990年   27篇
  1989年   13篇
  1988年   13篇
  1987年   13篇
  1986年   6篇
  1985年   8篇
  1984年   8篇
  1983年   5篇
  1982年   7篇
  1980年   4篇
  1979年   4篇
  1978年   5篇
  1975年   6篇
  1973年   8篇
  1969年   4篇
  1967年   7篇
排序方式: 共有3615条查询结果,搜索用时 0 毫秒
991.
Low birth weight (BWT) may contribute to kidney disease and could explain some of the variance in the development of early diabetic kidney disease. This hypothesis was tested in the multicenter SEARCH study (3,714 youth with diabetes <20 years of age). A morning spot urine sample, laboratory and anthropometric data, and a medical history were obtained. Elevated albumin to creatinine ratio (ACR) was defined as ≥30 mcg albumin/mg creatinine, and BWT was categorized as low (<2,500 g), reference (2,500–4,000 g), or high (>4,000 g). The relationship of BWT to elevated ACR was analyzed using multiple logistic regression. In youth with diabetes, the prevalence of elevated ACR was 12.6% in those with low BWT, 9.7% in those with reference BWT, and 8.9% in those with high BWT. BWT category was not significantly associated with elevated ACR (p = 0.23). Those with diabetes duration >18 months (2,032) had the following association of BWT category with elevated ACR [odds ratio (OR) = 1.64, 95% confidence interval (CI) 1.00–2.69, p = 0.0503] for low BWT compared with reference BWT. Whereas low BWT may be a factor in kidney disease, little evidence was found of a relationship between low BWT and elevated ACR in this study population of youth with diabetes. An erratum to this article can be found at  相似文献   
992.
Host-seeking ticks were collected during monthly dragging sessions from November 2004 through October 2006 in Tuscany, central Italy. Normalized difference vegetation index (NDVI), which was calculated from Landsat ETM+ 7 remote sensing data recorded in August 2001, was significantly correlated with numbers of host-seeking immature Ixodes ricinus L. (Acari: Ixodidae) during periods of relatively low rainfall such as summer 2005 (Spearman's p = 0.78, P < 0.001 for nymphs in July) and to a lower extent in spring-summer 2006. In spring 2005, when rainfall was relatively high, the correlation was weak and not statistically significant. Generalized estimating equations (GEEs), taking into account repeated sampling of the same dragging sites, were used to model the effects of NDVI and season on counts of host-seeking I. ricinus nymphs. Seasonal variations of the effect of NDVI yielded a significant NDVI-by-season interaction in the first year of the study (November 2004-October 2005), but not in the second year (November 2005-October 2006) when there was a 2.5-fold increase of the number of nymphs per 100-m dragging for every 0.1 unit increase in NDVI (95% confidence interval = 1.6, 3.0). Risk maps that were obtained based on GEE results confirmed that the predicted number of I. ricinus nymphs per 100 m was relatively homogeneous through the study area during the 2005 spring peak of activity. Conversely, in 2006, the predicted abundance of nymphs was greater in moist bottomland habitat (characterized by high NDVI) than in dry, typically Mediterranean, upland habitat.  相似文献   
993.
At variance with other organs, where the functional and structural units are repeated, the brain is a composite assembly of groups of cells with different metabolic features and functional units. Deterioration of brain function occurs when the number of neurons or their connections decrease below a critical reserve level and coping with environmental stimulation is seriously hampered. Physiopathological alterations of the synaptic junctional areas are reported to play a central role in the process of brain aging. Current research is documenting an age-related numeric loss of synapses which is paired by a significant enlargement of the persisting contact zones: the final outcome of these balanced changes is a significant reduction of the overall synaptic junctional area per unit volume of neuropil. The progressive decline of the mitochondrial metabolic competence, i.e. the capacity of select pools of organelles to provide adequate amounts of adenosine triphosphate is supposed to represent a key determinant in synaptic aging. Cytochemical estimations of the activity of cytochrome oxidase confirm that mitochondrial dysfunctions play an early role in synaptic deterioration. Zinc ions act as physiological neuromodulators at glutamatergic synapses, however, in order to avoid neurotoxic damage, the intracellular free Zn++ concentration ([Zn++]i) must be tightly controlled by: (i) extrusion (Zn++ transporters); (ii) buffering (metallothioneins) and (iii) sequestration (mitochondria) systems. In physiological aging, if any of these systems is impaired and/or not adequately coordinated with the other two, the resulting significant rise of ([Zn++]i) may inhibit the cellular energy providing systems and affect mitochondria as primary target.  相似文献   
994.
Rats deprived of social contact with other rats at a young age experience a form of prolonged stress that leads to long-lasting alteration in their behavior profile. This chronic stress paradigm is thus thought to be anxiogenic for these normally gregarious animals and their abnormal reactivity to environmental stimuli, when reared under this condition, is thought to be a product of prolonged stress. Neurochemical, molecular, and electrophysiological evidences demonstrate that social isolation is associated with alteration in the structure and function of GABAA receptors and suggest that endogenous content of the progesterone metabolite 3,5-TH PROG may be an important determinant in regulating brain excitability and sensitivity to stimuli and point out its possible role in psychiatric and neurological disorder.  相似文献   
995.
996.
Purpose The aim of this study was to evaluate downstaging as primary end point, and progression-free survival and overall survival as secondary end points, in rectal adenocarcinoma patients treated with preoperative chemoradiation. Methods One hundred and thirty-six extraperitoneal adenocarcinoma patients (33 low rectum T2, 74 T3, 29 T4 [without sacral invasion], 25 with mucinous subtype) were treated with posterior pelvis preoperative radiotherapy (5040 cGy total dose, 180 cGy/fr, 5 fr/w, 10–15 MV linac X-rays) and concomitant 5-fluorouracil-based chemotherapy. After 6 to 8 weeks patients underwent surgery and prechemoradiation clinical stage was compared with pathologic stage to evaluate downstaging in each patient. Seventy-four patients received adjuvant chemotherapy. Median follow-up was 39 months (4–84). Results Forty-four patients had macroscopic complete response, 52 patients had partial response, 37 patients showed no change and 3 patients had progression. At multivariate analysis only histotype showed correlation with downstaging (hazard ratio = 0.350 and 0.138 – 0.885 95 percent confidence interval) because of the evidence for poor downstaging in mucinous subtype. There were no significant differences in overall survival and progression-free survival between adenocarcinoma and mucinous subtype. Conclusions The main finding is that mucinous histology is associated with poor downstaging after preoperative chemoradiation but this poor response was not associated with worse outcome in this small study. The good outcome for mucinous histology is at odds with other reports in the literature and requires further study.  相似文献   
997.
BACKGROUND: Atopic dermatitis often has an allergic component, and immunotherapy may therefore prove beneficial. OBJECTIVE: To assess the effect of sublingual immunotherapy (SLIT) in children with atopic dermatitis. METHODS: Children age 5 to 16 years with atopic dermatitis (Scoring Atopic Dermatitis [SCORAD] > 7) and sensitization to dust mites alone, without food allergy or chronic asthma, were enrolled in a randomized, double-blind, placebo-controlled study and stratified according to disease severity. SLIT or placebo was given for 18 months in addition to standard therapy. SCORAD, visual analog scale, and rescue medication consumption were recorded at 3-month intervals. RESULTS: Fifty-six children were enrolled, and 28 were allocated to SLIT. Forty-eight completed the study, with 2 dropouts in the active and 6 in the placebo group. The difference from baseline in the SCORAD was significant (P = .025) between the 2 groups starting from month 9. Similarly, there was a significant reduction in the use of medications only in the active group. A trend toward significance was seen for the visual analog score only in the active group versus baseline (P = .07). A significant difference in the considered parameters was found only in patients with a mild-moderate disease, whereas severe patients had only a marginal benefit. SLIT had to be discontinued in 2 patients because of exacerbation of dermatitis. CONCLUSION: Sublingual immunotherapy to dust mite improves mild-moderate atopic dermatitis. CLINICAL IMPLICATIONS: Sublingual immunotherapy may represent an additional therapeutic tool for the treatment of extrinsic atopic dermatitis in properly selected children.  相似文献   
998.
999.
Ramaglia G  Romeo A  Viri M  Lodi M  Sacchi S  Cioffi G 《Epilepsia》2007,48(9):1810-1814
The purpose of the study was to examine the impact of idiopathic epilepsy on mothers and fathers in terms of strain, burden of care, worries and perception of vulnerability. Data were collected and analyzed shortly after the diagnosis (T0) and 12 months later (T1). The results indicated that at T0 parents of children with epilepsy showed higher levels of worries and perception of vulnerability than controls; mothers sustained a greater burden of care and exhibited higher levels of strain than fathers. At T1, strain and perception of vulnerability decreased both for mothers and fathers, while burden of care and worries remained stable. At T0 and T1, strain was associated with parents' perception of vulnerability and anxiety for their children's future.  相似文献   
1000.
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