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   1905篇
  免费   113篇
  国内免费   19篇
耳鼻咽喉   3篇
儿科学   44篇
妇产科学   47篇
基础医学   287篇
口腔科学   19篇
临床医学   177篇
内科学   469篇
皮肤病学   53篇
神经病学   213篇
特种医学   57篇
外科学   157篇
综合类   3篇
一般理论   1篇
预防医学   93篇
眼科学   18篇
药学   159篇
中国医学   4篇
肿瘤学   233篇
  2024年   3篇
  2023年   20篇
  2022年   30篇
  2021年   62篇
  2020年   40篇
  2019年   41篇
  2018年   58篇
  2017年   45篇
  2016年   54篇
  2015年   66篇
  2014年   72篇
  2013年   102篇
  2012年   172篇
  2011年   155篇
  2010年   85篇
  2009年   82篇
  2008年   109篇
  2007年   135篇
  2006年   142篇
  2005年   114篇
  2004年   98篇
  2003年   100篇
  2002年   71篇
  2001年   10篇
  2000年   16篇
  1999年   20篇
  1998年   15篇
  1997年   18篇
  1996年   15篇
  1995年   8篇
  1994年   6篇
  1993年   10篇
  1992年   10篇
  1991年   7篇
  1990年   9篇
  1989年   5篇
  1988年   7篇
  1987年   2篇
  1986年   2篇
  1985年   4篇
  1983年   1篇
  1982年   4篇
  1981年   2篇
  1980年   1篇
  1978年   1篇
  1977年   1篇
  1975年   3篇
  1973年   1篇
  1970年   1篇
  1969年   1篇
排序方式: 共有2037条查询结果,搜索用时 31 毫秒
71.
72.
Myelodysplastic syndromes (MDS) are common in elderly patients. Recombinant human erythro-poietin (rHuEPO) has been widely used to treat anemia in lower risk MDS patients, but few data are known about rHuEPO treatment in the very elderly patient group. In order to investigate the role of rHuEPO treatment in terms of response, overall survival (OS), and toxicity in a very elderly MDS patient group, 93 MDS patients treated with rHuEPO when aged ≥80 years were selected among MDS cases enrolled in a retrospective multicenter study by the cooperative group Gruppo Romano Mielodisplasie (GROM) from Jan 2002 to Dec 2010. At baseline, median age was 82.7 (range 80–99.1) with a median hemoglobin (Hb) level of 9 g/dl (range 6–10.8). The initial dose of rHuEPO was standard (epoetin alpha 40,000 IU/week or epoetin beta 30,000 IU/week) in 59 (63.4 %) pa-tients or high in 34 (36.6 %) (epoetin alpha 80,000 IU/week) patients. We observed an erythroid response (ER) in 59 (63.4 %) patients. No thrombotic event was reported. Independent predictive factors for ER were low transfusion requirement before treatment (p?=?0.004), ferritin <200 ng/ml (p?=?0.017), Hb >8 g/dl (p?=?0.034), and a high-dose rHuEPO treatment (p?=?0.032). Median OS from rHuEPO start was 49.3 months (95 % CI 27.5–68.4) in responders versus 30.6 months (95 % CI 7.3–53.8) in resistant patients (p?=?0.185). In conclusion, rHuEPO treatment is safe and effective also in the very elderly MDS patients. However, further larger studies are warranted to evaluate if EPO treatment could be worthwhile in terms of quality of life and cost-efficacy in very old patients.  相似文献   
73.
Adult patients with Niemann-Pick disease type C (NPC) usually develop cognitive impairment progressing to dementia, whose pathophysiology remains still unclear. Noteworthy parallels exist in cognitive impairment and cellular pathology of NPC and Alzheimer’s disease (AD). In particular, alterations of cholinergic system, which represent one of the pathological hallmarks and contribute to cognitive deterioration in AD, have recently been demonstrated in a human brain autopsy and in an experimental model of NPC. This finding raised the issue that central cholinergic circuits dysfunction may contribute to pathophysiology of cognitive impairment in NPC as well, and prompted us to evaluate the cholinergic functional involvement in NPC patients by applying a neurophysiologic technique, named short-latency afferent inhibition (SAI). We describe clinical, biochemical, molecular and neuropsychological features, and SAI findings in three patients affected by NPC. Diagnosis of NPC was assessed by molecular analysis of the NPC1 gene in all patients. In two of them, biochemical analysis of intracellular accumulation of unesterified cholesterol was also performed. The main clinical features were cerebellar ataxia, vertical supranuclear gaze palsy and a variable degree of cognitive impairment ranging from only memory impairment to severe dementia. Electrophysiological evaluation revealed a reduced SAI in all three patients. Our SAI findings provide evidence of cholinergic dysfunction in patients with the adult form of NPC, supporting that cholinergic alterations may play a role in cognitive impairment in NPC, and strengthening the similarities between NPC and AD.  相似文献   
74.
75.
76.
77.
A copper-based metal–organic framework (MOF) was prepared using a new linker, a 5-substituted isophthalic acid bearing a propargyl carbamate group, intended to provide a terminal alkyne function protruding from the material surface to generate supported gold species for potential catalytic applications. The novel material was fully characterized by spectroscopic analyses of different kinds: FTIR, Raman, EDX, and XPS, as well as by thermal and surface area measurements. Synchrotron X-ray diffraction data analysis, in particular, revealed that this MOF, labelled [Cu(1,3-YBDC)]·xH2O (x ∼ 2), where Y stands for the pendant alkYne and BDC for benzene dicarboxylate, contains a complex network of 5-substituted isophthalate anions bound to Cu(ii) centers, arranged in pairs within paddlewheel (or “Chinese lantern”) fragments of Cu2(μ-COO)4(D)2 formulation (D being a neutral Lewis base), with a short Cu⋯Cu distance of 2.633(4) Å. Quite unexpectedly, the apical atom in the paddlewheel structure belongs to the carbamate carbonyl oxygen atom. Such extra coordination by the propargyl carbamate groups drastically reduces the MOF porosity, a feature that was also confirmed by BET measurements. However, the MOF functionality is retained at the external crystal surface where 2% of active terminal alkynes is located.

A copper-based metal–organic framework with a novel 5-substituted isophthalic linker bearing a propargyl carbamate group protruding from the material surface.  相似文献   
78.
79.
Mitochondrial components, including mitochondrial DNA (mtDNA), when released extracellularly, can act as “damage‐associated molecular pattern” (DAMP) agents and cause inflammation. As many elderly people are characterized by a low‐grade, chronic inflammatory status defined “inflamm‐aging,” we evaluated if circulating mtDNA can contribute to this phenomenon. Eight hundred and thirty‐one Caucasian subjects were enrolled in the study, including 429 siblings aged 90–104 (90+ siblings). mtDNA plasma levels increased gradually after the fifth decade of life. In 90+ subjects, mtDNA values of two members of the same sibling relationship were directly correlated, suggesting a role for familiar/genetic background in controlling the levels of circulating mtDNA. The subjects with the highest mtDNA plasma levels had the highest amounts of TNF‐α, IL‐6, RANTES, and IL‐1ra; the subjects with the lowest mtDNA levels had the lowest levels of the same cytokines. In vitro stimulation of monocytes with mtDNA concentrations similar to the highest levels observed in vivo resulted in an increased production of TNF‐α, suggesting that mtDNA can modulate the production of proinflammatory cytokines. Our findings therefore show that circulating mtDNA increases with age, and can significantly contribute to the maintenance of the low‐grade, chronic inflammation observed in elderly people.  相似文献   
80.
The use of microalgae in the skin care market is already established although the scientific rationale for their benefit was not clearly defined. In this work, the biological activities of dermatologic interest of the water extract from the microalga Botryococcus braunii (BBWE) were evaluated by a battery of in vitro assays. At concentrations ranging from 0.1 to 0.001?% (w/v) BBWE promoted adipocytes differentiation by inhibiting hormone-sensitive lipase, thus promoting triglyceride accumulation in the cells. BBWE also induced gene expression of proteins involved in the maintenance of skin cells water balance such as aquaporin-3 (AQP3), filaggrin (FLG) and involucrin (INV). 0.1?% BBWE increased the gene expression of AQP3 of 2.6-folds, that of FLG and INV of 1.5- and 1.9-folds, respectively. Moreover, it induced the biosynthesis of collagen I and collagen III by 80 and 40?%, respectively, compared to the untreated control. BBWE antioxidant activity, evaluated by oxygen radical absorbance capacity (ORAC) assay, was of 43.5?μmol Trolox per gram of extract: a quite high value among those found for other microalgae extracts. BBWE inhibited the inducible nitric oxide synthase (iNOS) gene expression and the consequent nitrite oxide (NO) production under oxidative stress. At a concentration of 0.02?% BBWE reduced by 50?% the expression of iNOS and by about 75?% the NO production. Taken together, the results demonstrated that B. braunii water extract exerted an array of biological activities concurring with the skin health maintenance; therefore, it is a potential bioactive ingredient to be included in cosmetic products.  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