全文获取类型
收费全文 | 15841篇 |
免费 | 1219篇 |
国内免费 | 79篇 |
专业分类
耳鼻咽喉 | 137篇 |
儿科学 | 427篇 |
妇产科学 | 269篇 |
基础医学 | 2769篇 |
口腔科学 | 526篇 |
临床医学 | 1334篇 |
内科学 | 3507篇 |
皮肤病学 | 359篇 |
神经病学 | 1778篇 |
特种医学 | 302篇 |
外科学 | 1527篇 |
综合类 | 67篇 |
一般理论 | 10篇 |
预防医学 | 1269篇 |
眼科学 | 320篇 |
药学 | 1161篇 |
中国医学 | 81篇 |
肿瘤学 | 1296篇 |
出版年
2024年 | 16篇 |
2023年 | 148篇 |
2022年 | 286篇 |
2021年 | 701篇 |
2020年 | 409篇 |
2019年 | 527篇 |
2018年 | 594篇 |
2017年 | 464篇 |
2016年 | 516篇 |
2015年 | 549篇 |
2014年 | 705篇 |
2013年 | 821篇 |
2012年 | 1306篇 |
2011年 | 1375篇 |
2010年 | 747篇 |
2009年 | 625篇 |
2008年 | 972篇 |
2007年 | 1042篇 |
2006年 | 904篇 |
2005年 | 883篇 |
2004年 | 835篇 |
2003年 | 674篇 |
2002年 | 640篇 |
2001年 | 161篇 |
2000年 | 139篇 |
1999年 | 119篇 |
1998年 | 121篇 |
1997年 | 113篇 |
1996年 | 78篇 |
1995年 | 75篇 |
1994年 | 56篇 |
1993年 | 44篇 |
1992年 | 77篇 |
1991年 | 53篇 |
1990年 | 50篇 |
1989年 | 35篇 |
1988年 | 33篇 |
1987年 | 26篇 |
1986年 | 21篇 |
1985年 | 34篇 |
1984年 | 21篇 |
1983年 | 21篇 |
1982年 | 18篇 |
1981年 | 15篇 |
1979年 | 8篇 |
1978年 | 10篇 |
1977年 | 7篇 |
1974年 | 7篇 |
1973年 | 8篇 |
1970年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 671 毫秒
21.
Ellen J Schlette L Jeffrey Medeiros Andre Goy Raymond Lai George Z Rassidakis 《Journal of clinical oncology》2004,22(9):1682-1688
PURPOSE: Survivin, a member of the inhibitor of apoptosis (IAP) family, is not detected in normal adult tissues but is overexpressed in various cancers, including some types of lymphoma. The frequency and prognostic significance of survivin expression in anaplastic large-cell lymphoma (ALCL) is unknown. Materials and METHODS: We assessed for survivin expression in 62 ALCL tumors (30 anaplastic lymphoma kinase [ALK]-positive and 32 ALK-negative) obtained before doxorubicin-based chemotherapy. Given that survivin is a target of the STAT3 signaling pathway and STAT3 is activated in ALCL, survivin expression was also correlated with STAT3 activation. RESULTS: Survivin was expressed in 34 tumors (55%) and did not correlate with ALK. A significant association between survivin expression and STAT3 activation was observed (P =.007, Fisher's exact test). For the ALK-positive group, the 5-year failure-free survival (FFS) was 34% for patients with survivin-positive ALCL compared with 100% for patients with survivin-negative ALCL (P =.009, log-rank test). For the ALK-negative group, the 5-year FFS was 46% for patients with survivin-positive tumors compared with 89% for patients with survivin-negative tumors (P =.03, log-rank test). Overall survival was similarly worse for patients with survivin-positive tumors in both the ALK-positive and ALK-negative groups. Furthermore, multivariate analysis confirmed the independent prognostic value of survivin expression, along with age older than 60 years and Ann Arbor stage III or IV. CONCLUSION: Survivin is expressed in approximately half of ALCL tumors and independently predicts unfavorable clinical outcome. Modulation of survivin expression or function may provide a novel target for experimental therapy in patients with ALCL. 相似文献
22.
The complex enterprise of modelling prenatal exposure to cigarettes: what is ‘enough’? 总被引:1,自引:0,他引:1
Kate E. Pickett Paul J. Rathouz Vanja Dukic Kristen Kasza Marina Niessner Rosalind J. Wright Lauren S. Wakschlag 《Paediatric and perinatal epidemiology》2009,23(2):160-170
While there is a burgeoning body of research linking smoking during pregnancy to problem behaviour in offspring, a major criticism of this work has been the crude measurement of exposure in these studies (e.g. retrospective, self-reported only) that could lead to biased estimates. To address this issue, we used a pregnancy cohort with repeated prospective measures of exposure as well as biological assays to generate estimates of exposure patterns using a range of modelling techniques. In this paper we report on the analytical approaches we have developed, including patterns of exposure over time and best-estimate approaches that combine self-report and cotinine measures, and compare their predictive value in relation to different dimensions of fetal growth as a first step towards examining the utility of greater precision of exposure measurement.
Surprisingly, in this sample the more complex assessments of exposure, including biological measures, generally did not perform better than simple indicators of exposure based on repeated self-report measures, with one exception: a combined self-report cotinine 'best estimate' of third trimester exposure was uniquely associated with lower brain : body ratio. Further study is needed using more sophisticated cotinine assays and testing prediction of a range of outcomes to ascertain whether these findings represent true differences or are specific to the sample, methods and outcomes used. Such research will inform the development of guidelines for adequate exposure characterisation in developmental studies. 相似文献
Surprisingly, in this sample the more complex assessments of exposure, including biological measures, generally did not perform better than simple indicators of exposure based on repeated self-report measures, with one exception: a combined self-report cotinine 'best estimate' of third trimester exposure was uniquely associated with lower brain : body ratio. Further study is needed using more sophisticated cotinine assays and testing prediction of a range of outcomes to ascertain whether these findings represent true differences or are specific to the sample, methods and outcomes used. Such research will inform the development of guidelines for adequate exposure characterisation in developmental studies. 相似文献
23.
Aldo Cunha Medeiros Irami Araújo Filho Vítor Brasil Medeiros Laíza Araújo Mohana Pinheiro Flávio Henrique Miranda Araújo Freire Italo Medeiros Azevedo José Brand?o-Neto 《Journal of investigative surgery》2007,20(1):41-48
After total gastrectomy, the ileocecal graft may act as a reservoir and protect against reflux but give rise to transposition of the ileum and cause possible changes in bile acid metabolism and nutrition. This study compared the ileocecal graft and jejunal pouch. Male Wistar rats weighing 265 +/- 22 g were submitted to sham operation (S), ileocecal interposition graft (IIG), and jejunal pouch interposition graft (JP) after total gastrectomy. Eight weeks later, the esophagus was examined for evidence of esophagitis. Nutritional biochemistry and weight profile were documented preoperatively and 8 weeks after surgery. The oral glucose tolerance test was performed. Thirty-three rats were operated on and 30 survived for 8 weeks. Esophagitis occurred in seven JP rats. Body weight was significantly higher in IIG than in JP rats (p < .05). Normal glucose tolerance to intragastric glucose load was observed in sham and operated rats. JP rats had a significant decrease in serum albumin, glucose, transferrin, hemoglobin, iron, folate, and calcium, compared to sham (p < .05). Cobalamine was significantly lower in IIG rats than in JP rats (p < .05). In the IIG and JP groups, serum/hepatic total bile acid did not differ significantly from preoperative and sham values. In conclusion, the IIG interposition graft in rats prevented esophagitis, preserved nutrition, and did not interfere with enterohepatic total bile acid circulation. 相似文献
24.
Patients presented at the emergency room with chest pain, non-characteristicECG changes and negative Troponin represent a very frequentclinical dilemma. These patients are often hospitalized unnecessarilyand frequently undergo non-invasive and even invasive investigationswhich turn out to be negative. Occasionally, they may falselybe discharged from the ER and eventually develop a major cardiacevent. The most common and apparently the cheapest test employedin the evaluation of these patients is standard exercise ECG.Jeetley et al.1 prospectively studied a large group ofsuch patients. The patients 相似文献
25.
Effect of olanzapine treatment on platelet glutamine synthetase-like protein and glutamate dehydrogenase immunoreactivity in schizophrenia. 总被引:1,自引:0,他引:1
Gulnur Sh Burbaeva Irina S Boksha Elena B Tereshkina Olga K Savushkina Marina S Turishcheva Lubov I Starodubtseva Oleg S Brusov Margarita A Morozova 《The world journal of biological psychiatry》2006,7(2):75-81
According to contemporary views, the glutamatergic system is implicated in the pathogenesis of schizophrenia, and atypical neuroleptics exert their effects (at least partially) through the glutamatergic system. Immunoreactive glutamate-metabolising enzymes, such as glutamine synthetase-like protein (GSLP) and two glutamate dehydrogenase isoenzymes (GDH), have been discovered in human platelets. The amount of GSLP in the platelets of 40 chronic patients with schizophrenia was found to be significantly higher than in 33 controls (consistent with our previous finding of increased amounts of GSLP in the prefrontal cortex of chronic schizophrenia patients). Moreover, survival analysis of the group of patients treated with olanzapine for 28 weeks showed that the larger amount of GSLP measured in platelets before treatment, the shorter the treatment time needed to achieve a positive clinical response (defined a priori as > or = 20% reduction in PANSS total score from the initial level before the treatment). Hence, GSLP level may serve as a predictor of the treatment duration to achieve a positive outcome with olanzapine. Both GSLP and GDH were found significantly changed in the course of treatment; hence, treatment with olanzapine influences the amounts of glutamate-metabolising enzymes in the platelets of chronic schizophrenia patients. 相似文献
26.
27.
Margaret J. Tango Evelyn Safaris Margarita Romanella Atousa Aminian Marina Katerelos Christine Somerwille RIek G. Tearle Martin J. Pearse Anthony J.E d'Apice 《Xenotransplantation》1997,4(1):25-33
Abstract: Transgenic expression of the human complement regulatory molecule CD59 in mice and genetic deletion of the major xenoantigen galactose α 1,3 galactose (Gal KO) each resulted in partial protection of spleen cells from lysis by human serum. These protective effects were additive when the two genetic modifications were combined. However, when the effects of these genetic modifications were examined in an ex vivo model in which mouse hearts were perfused with human plasma, it was Gal KO which was the modification which determined protection. CD59 expression alone was not protective and CD59 expression in combination with Gal knockout did not result in a significant additional increase in protection over and above that provided by Gal knockout alone. The likely explanation for this discrepancy between the in vitro and ex vivo data is that the H2-Kb promoter used to drive CD59 expression results I in substantially less expression on endothelium than on spleen cells. 相似文献
28.
Tatjana Pekmezovi? Natasa Ivanovi? Marina Svetel Dragana Nali? Tatjana Smiljkovi? Ranko Raicevi? Vladimir S Kosti? 《Movement disorders》2003,18(11):1389-1392
The aim of this cross-sectional study was to estimate the prevalence of different subtypes of idiopathic focal dystonia in the population of Belgrade (Serbia), Yugoslavia. On December 31, 2001, the crude prevalence of all studied types of dystonia (focal, segmental, and multifocal) in Belgrade was 13.6 per 100,000 population (11.8 per 100,000 for men and 15.2 per 100,000 for women). Type-specific prevalence for focal dystonia was 11.2 per 100,000. The prevalence for cervical dystonia, blepharospasm, writer's cramp and laryngeal dystonia were 5.9 per 100,000, 1.9 per 100,000, 1.9 per 100,000, and 1.1 per 100,000, respectively. 相似文献
29.
Mikhail Strokin Marina Sergeeva Georg Reiser 《International journal of developmental neuroscience》2004,22(7):551-557
Various diseases of the central nervous system are characterized by induction of inflammatory events, which involve formation of prostaglandins. Production of prostaglandins is regulated by activity of phospholipases A(2) and cyclooxygenases. These enzymes release the prostaglandin precursor, the n-6 polyunsaturated fatty acid, arachidonic acid and oxidize it into prostaglandin H(2). Docosahexaenoic acid, which belongs to the n-3 class of polyunsaturated fatty acids, was shown to reduce production of prostaglandins after in vivo and in vitro administration. Nevertheless, the fact that in brain tissue cellular phospholipids naturally have a uniquely high content of docosahexaenoic acid was ignored so far in studies of prostaglandin formation in brain tissue. We consider the following possibilities: docosahexaenoic acid might attenuate production of prostaglandins by direct inhibition of cyclooxygenases. Such inhibition was found with the isolated enzyme. Another possibility, which has been already shown is reduction of expression of inducible cyclooxygenase-2. Additionally, we propose that docosahexaenoic acid could influence intracellular Ca(2+) signaling, which results in changes of activity of Ca(2+)-dependent phospholipase A(2), hence reducing the amount of arachidonic acid available for prostaglandin production. Astrocytes, the main type of glial cells in the brain control the release of arachidonic acid, docosahexaenoic acid and the formation of prostaglandins. Our recently obtained data revealed that the release of arachidonic and docosahexaenoic acids in astrocytes is controlled by different isoforms of phospholipase A(2), i.e. Ca(2+)-dependent phospholipase A(2) and Ca(2+)-independent phospholipase A(2), respectively. Moreover, the release of arachidonic and docosahexaenoic acids is differently regulated through Ca(2+)- and cAMP-dependent signal transduction pathways. Based on analysis of the current literature and our own data we put forward the hypothesis that Ca(2+)-independent phospholipase A(2) and docosahexaenoic acid are promising targets for treatment of inflammatory related disorders in brain. We suggest that Ca(2+)-independent phospholipase A(2) and docosahexaenoic acid might be crucially involved in brain-specific regulation of prostaglandins. 相似文献