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   247122篇
  免费   7170篇
  国内免费   1028篇
耳鼻咽喉   3719篇
儿科学   8000篇
妇产科学   6643篇
基础医学   34438篇
口腔科学   7060篇
临床医学   19782篇
内科学   44726篇
皮肤病学   6320篇
神经病学   15313篇
特种医学   13432篇
外国民族医学   97篇
外科学   36231篇
综合类   1289篇
现状与发展   1篇
一般理论   18篇
预防医学   18780篇
眼科学   5477篇
药学   18215篇
  2篇
中国医学   763篇
肿瘤学   15014篇
  2022年   1055篇
  2021年   2124篇
  2020年   1102篇
  2019年   1336篇
  2018年   5055篇
  2017年   5001篇
  2016年   4841篇
  2015年   7327篇
  2014年   7232篇
  2013年   6732篇
  2012年   14888篇
  2011年   9287篇
  2010年   4864篇
  2009年   6103篇
  2008年   5287篇
  2007年   5687篇
  2006年   5514篇
  2005年   13310篇
  2004年   14437篇
  2003年   9735篇
  2002年   4739篇
  2001年   5658篇
  2000年   2922篇
  1999年   6710篇
  1992年   7184篇
  1991年   7403篇
  1990年   7611篇
  1989年   7192篇
  1988年   6706篇
  1987年   6474篇
  1986年   6122篇
  1985年   5399篇
  1984年   3704篇
  1983年   3016篇
  1982年   1054篇
  1979年   3908篇
  1978年   2429篇
  1977年   1820篇
  1976年   1604篇
  1975年   2523篇
  1974年   3165篇
  1973年   2789篇
  1972年   2806篇
  1971年   2778篇
  1970年   2604篇
  1969年   2482篇
  1968年   2266篇
  1967年   2181篇
  1966年   1923篇
  1965年   1143篇
排序方式: 共有10000条查询结果,搜索用时 93 毫秒
71.
SETTING: Tuberculosis (TB) cases reported from nine districts of Madrid, where the percentage of immigrant population varied from 1.9% in 1996 to 12.2% in 2003. OBJECTIVE: To describe the trends in TB incidence from 1994 to 2003. DESIGN: Observational study. RESULTS: Between 1994-1995 and 2002-2003, the TB rate decreased from 48.5 (95% CI 45.8-51.1) to 23.3 per 100000 population (95% CI 21.5-25.1) (P < 0.001). The percentage of TB cases co-infected with HIV decreased from 55.9% in 1994 to 14.3% in 2003 (P < 0.001), whereas TB cases in foreigners increased from 2.6% in 1994 to 33.7% in 2003 (P < 0.001). CONCLUSION: Although the TB rates showed a marked decrease in the study period, the increasing impact of immigration contributed to slowing down the trend.  相似文献   
72.
OBJECTIVE: The aim of the current study was to test the impact of dentin powder on the antimicrobial efficacy of bioactive glass S53P4 (BAG). STUDY DESIGN: BAG was suspended (preincubated) in saline at 37 degrees C for different time periods with or without human dentin powder, hydroxylapatite, or decalcified dentin. Subsequently, Enterococcus faecalis ATCC 29212 cells were added to these suspensions and bacterial recovery measured with and without the use of gentle sonication. Furthermore, survival of bacteria in test and control suspensions was assessed over time. Supernatants of suspensions were analyzed for their element contents using atomic absorption spectrophotometry. The effects of pH, silica, and osmolarity on E faecalis viability were assessed using specifically prepared solutions. RESULTS: BAG preincubated with dentin powder caused a significant (P < .05) decrease in viability compared to pure BAG suspensions. This was not based on adherence of bacteria to solid particles or agglutination of the cells, because sonication did not increase bacterial yields. Hydroxylapatite and decalcified dentin did not increase BAG killing efficacy. The additive effect of BAG + dentin powder was dose dependent, occurred only with solids in suspension, and increased with suspension time. An augmented dissolution of glass components, especially silicon, was measured in BAG + dentin powder compared to pure BAG suspensions or counterparts containing hydroxylapatite or decalcified dentin. High osmolarity per se did not affect E faecalis viability, whereas high pH and silica levels did. CONCLUSION: The observed phenomenon was related to an increased BAG dissolution triggered by dentin powder, causing elevated local pH and silica levels.  相似文献   
73.
This article describes a modified suture technique designed for the vertical repair of the anterior horn of the meniscus after arthroscopic decompression of a large meniscal cyst. This procedure comprises of three steps: first, the meniscus was pierced vertically using a suture hook and a No. 0 PDS suture. Second, both ends of the No. 0 PDS on the femoral and tibial surfaces of the meniscus were pulled to the outside of the joint capsule using a spinal needle preloaded with suture material. Finally, a skin incision was made adjacent to the suture materials, and both ends were tied. We recommend this technique not only for the vertical repair of the anterior horn of the meniscus after decompression of large meniscal cyst, but also to repair a longitudinal tear of the meniscus.  相似文献   
74.
Spinocerebellar ataxia (SCA) types 2 and 3 are autosomal-dominant neurodegenerative disorders caused by mutations in two different genes. We identified mutations for SCA2 and SCA3 segregating simultaneously in a single Brazilian family. The index patient had SCA2, whereas her two second-degree cousins had SCA3. Disease was more rapidly progressive in the SCA2 patient, who presented severe brainstem and pancerebellar atrophy, as opposed to the two SCA3 patients, who had only mild cerebellar vermian atrophy. In such situations, molecular confirmation of all patients may avoid misdiagnosis of SCA subtypes and eventual errors in predictive testing of unaffected family members.  相似文献   
75.
Cognitive function after on or off pump coronary artery bypass grafting.   总被引:1,自引:0,他引:1  
OBJECTIVE: To investigate cognitive outcome after on and off pump coronary artery bypass grafting. METHODS: Seventy patients between 50 and 80 years with stable angina pectoris, ejection fraction >30%, serum creatinine <150 micromol/l, and lack of tight main stem stenosis were randomized to on or off pump coronary artery bypass grafting. Standardized neuropsychological tests evaluated attention, verbal and visuo-spatial short-term and working memory, verbal learning, delayed recall, visuo-motor speed, and aspects of executive functions. Levels of anxiety and depression were also investigated. Testing was performed before and at 1 week, 1 and 6 months after surgery. RESULTS: There was no difference in cognitive impairment (defined as a 20% reduction in at least 20% of the tests) between groups. The incidence at 1 week post-operatively was 57% in the on pump group and 58% in the off pump group, after 1 month 30% and 12% and after 6 months 19% and 15%, respectively (p for interaction=0.19). There was no difference between groups in anxiety (p=0.18) or depression (p=0.48). CONCLUSIONS: This prospective, randomized study showed no differences in post-operative cognitive function after on pump compared to off pump coronary artery bypass grafting in low risk patients.  相似文献   
76.
Spray coated pellets as carrier system for mucoadhesive drug nanocrystals.   总被引:1,自引:0,他引:1  
High pressure homogenization can be employed to produce drug nanocrystals with a number of advantages, like improved solubility behaviors, better drug targeting or even increased mucoadhesiveness. To obtain a controlled drug delivery system it is necessary to transform the resulting nanosuspension into a solid dosage form. The present study shows the feasibility to use a mucoadhesive nanosuspension of poorly soluble hydrocortisone acetate produced by high pressure homogenization as layering dispersion in a fluidized bed process, followed by the application of an enteric coating to achieve a controlled drug release. To point out the advantages of drug nanocrystals the new fomulation was compared with a formulation containing micronized drug. Both formulations were characterized with regard to their particle size and crystallinity by using laser diffractometry, photon correlation spectroscopy and X-ray diffraction. The pellet morphology was characterized by using the environmental scanning electron microscopy (ESEM). In the in vitro dissolution tests an accelerated dissolution velocity and an increased drug release could be shown for the pellets containing drug nanocrystals.  相似文献   
77.
BACKGROUND: A primary tubular sodium handling abnormality has been implicated in the edema formation of nephrotic syndrome. Dopamine synthesized by renal proximal tubules behaves as an endogenous natriuretic hormone by activating D(1)-like receptors as a paracrine/autocrine substance. METHODS: We examined the time courses of the urinary excretion of sodium, protein and dopamine in puromycin aminonucleoside (PAN)-treated and control rats. The rats were sacrificed during greatest sodium retention (day 7) as well as during negative sodium balance (day 14) for the evaluation of renal aromatic l-amino acid decarboxylase (AADC) activity, the enzyme responsible for the synthesis of renal dopamine. Also, the influence of volume expansion (VE) and the effects of the D(1)-like agonist fenoldopam (10 microg/kg bw/min) on natriuresis and on proximal tubular Na(+),K(+)-ATPase activity were examined on day 7. RESULTS: The daily urinary excretion of dopamine was decreased in PAN-treated rats, from day 5 and beyond. This was accompanied by a marked decrease in the renal AADC activity, on days 7 and 14. During VE, the fenoldopam-induced decrease in proximal tubular Na(+),K(+)-ATPase activity was more pronounced in PAN-treated rats than in controls. However, the urinary sodium excretion during fenoldopam infusion was markedly increased in control rats but was not altered in PAN-treated animals. CONCLUSION: PAN nephrosis is associated with a blunted renal dopaminergic system activity which may contribute to enhance the proximal tubular Na(+),K(+)-ATPase activity. However, the lack of renal dopamine appears not to be related with the overall renal sodium retention in a state of proteinuria.  相似文献   
78.
Analyzing and shaping human attentional networks.   总被引:12,自引:0,他引:12  
In this paper we outline a conception of attentional networks arising from imaging studies as connections between activated brain areas carrying out localized mental operations. We consider both the areas of functional activation (nodes) and the structural (DTI) and functional connections (DCM) between them in real time (EEG, frequency analysis) as important tools in analyzing the network. The efficiency of network function involves the time course of activation of nodes and their connectivity to other areas of the network. We outline landmarks in the development of brain networks underlying executive attention from infancy and childhood. We use individual differences in network efficiency to examine genetic alleles that are related to performance. We consider how animal studies might be used to determine the genes that influence network development. Finally we indicate how training may aid in enhancing attentional networks. Our goal is to show the wide range of methods that can be used to suggest and analyze models of network function in the study of attention.  相似文献   
79.
Background/purpose: Vitiligo and nevus depigmentosus (ND) present similar hypopigmented macules with significantly different prognoses. Although the distinction between the two diseases is important, differential diagnosis relies on medical history and physical examination, which is far from decisive in some cases. The Mexameter® is an objective skin color-measuring device, and has been reported to provide a reproducible and sensitive means of quantifying small skin color differences. In this study, we investigated the usefulness of a Mexameter® for discriminating these diseases.
Methods: A selection of 202 hypopigmented skin lesions (182 from vitiligo and 20 from ND) were the objects of this study. Using a Mexameter, MIs were obtained from lesions and symmetrically located control skin. RMIs, ratios of the MIs of lesional skins to control skins, were calculated.
Results: The mean MIs and RMIs were significantly different for vitiligo and ND. The mean RMI of ND lesions was 74±13, which was significantly higher than that of vitiligo lesions (50±24). No ND lesion had an RMI of <50%.
Conclusion: This study shows that the Mexameter®, an objective pigment-measuring device, can be used to achieve a more accurate diagnosis of hypopigmentary disorders, and that the relative melanin index (RMI), which represents the relative pigment levels, might be a more effective parameter than the melanin index (MI) itself for comparing pigmentation differences.  相似文献   
80.
The lack of estrogen during menopause is associated with various symptoms including osteoporosis, cardiovascular diseases, and menopausal symptoms. For many years, conventional hormone replacement therapy has been successfully used to treat these conditions. However, in light of recent studies that draw attention to potential hazards of conventional HRT, various attempts were undertaken to search for alternatives of classical HRT. Phytoestrogens are supposed to ameliorate various discomforts associated with menopause. Resveratrol (RES) is present in red wine, grapes and peanuts and has been implicated in cardioprotection and prevention of adverse side effects observed after regular HRT. As the pituitary-thyroid axis is a target of estrogen action, we first assessed the effects of E2 administration on thyroid hormone stimulating hormone releasing hormone (TRH)-induced thyroid stimulating hormone (TSH) secretion from pituitary cell cultures in vitro. Our data reveal that E2 treatment augments the TRH-induced TSH secretion. We furthermore designed a long-term study of three months to assess the effects of subcutaneous and oral administration of 17beta-estradiol (E2), as well as the actions of RES on the pituitary-thyroid axis in ovariectomized (OVX) female rats. Our results demonstrate that serum levels of 1.0 and 8.1 microM RES lead to a significant increase in total serum triiodthyronine (T3) levels. OVX induces TSHbeta mRNA in the adenohypohysis and E2 treatment attenuates this effect. Treatment of rats with subcutaneous implants of E2 does not affect the pituitary-thyroid axis, whereas orally applied E2 benzoate (E2B) increases plasma TSH and total thyroxine (T4) in OVX rats. In all animals, we could not detect changes in thyroid morphology as assessed by hematoxylin-eosin (HE) and Perjod-Acid Schiff's (PAS) staining.  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