全文获取类型
收费全文 | 1704788篇 |
免费 | 139380篇 |
国内免费 | 2662篇 |
专业分类
耳鼻咽喉 | 23572篇 |
儿科学 | 56734篇 |
妇产科学 | 48911篇 |
基础医学 | 242877篇 |
口腔科学 | 51056篇 |
临床医学 | 149824篇 |
内科学 | 332478篇 |
皮肤病学 | 37354篇 |
神经病学 | 140646篇 |
特种医学 | 69458篇 |
外国民族医学 | 474篇 |
外科学 | 260556篇 |
综合类 | 40195篇 |
现状与发展 | 3篇 |
一般理论 | 582篇 |
预防医学 | 128640篇 |
眼科学 | 38932篇 |
药学 | 129003篇 |
2篇 | |
中国医学 | 3040篇 |
肿瘤学 | 92493篇 |
出版年
2018年 | 17311篇 |
2016年 | 15705篇 |
2015年 | 17443篇 |
2014年 | 23291篇 |
2013年 | 36044篇 |
2012年 | 48597篇 |
2011年 | 51608篇 |
2010年 | 30173篇 |
2009年 | 27848篇 |
2008年 | 49842篇 |
2007年 | 52446篇 |
2006年 | 53044篇 |
2005年 | 51563篇 |
2004年 | 50496篇 |
2003年 | 48515篇 |
2002年 | 47526篇 |
2001年 | 79358篇 |
2000年 | 82960篇 |
1999年 | 68680篇 |
1998年 | 17844篇 |
1997年 | 16224篇 |
1996年 | 16018篇 |
1995年 | 16551篇 |
1994年 | 15591篇 |
1993年 | 14731篇 |
1992年 | 55928篇 |
1991年 | 54260篇 |
1990年 | 53011篇 |
1989年 | 51286篇 |
1988年 | 47580篇 |
1987年 | 47000篇 |
1986年 | 44634篇 |
1985年 | 43374篇 |
1984年 | 32515篇 |
1983年 | 27964篇 |
1982年 | 16576篇 |
1981年 | 14814篇 |
1980年 | 13925篇 |
1979年 | 30817篇 |
1978年 | 21383篇 |
1977年 | 18078篇 |
1976年 | 16983篇 |
1975年 | 17850篇 |
1974年 | 21775篇 |
1973年 | 20907篇 |
1972年 | 19060篇 |
1971年 | 17987篇 |
1970年 | 16495篇 |
1969年 | 15453篇 |
1968年 | 14135篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Stephanie R. Morain 《The Hastings Center report》2019,49(4):28-30
In recent years, a robust body of scholarship has emerged that examines ethical challenges facing the learning health organization model. In “Bystander Ethics and Good Samaritanism,” James Sabin and colleagues make a valuable addition to this scholarship, identifying and exploring the important question of what researchers' obligations are to patients receiving “usual care” if “that care is seen as suboptimal.” The central issue that Sabin et al. faced was whether it would be acceptable for researchers to identify patients with untreated atrial fibrillation but then assign them to a control group that would not receive education about the importance of oral anticoagulation. The authors present this challenge as an issue of “bystander ethics.” To avoid being “bystanders” to identified instances of suboptimal care, the research team decided to instead identify a “delayed intervention” group for which they would not determine the members' anticoagulation status, thereby preventing them from knowing that specific patients met the criteria for oral anticoagulants but were not using them. This “workaround” approach strikes me as disingenuous. 相似文献
102.
de Morais Pollyana C. V. Gama Allyne F. Fernandes Gabrielle M. Oliveira Andre H. B. Lima Marcielly F. B. dos Santos Felipe R. Martins Davi A. Nascimento Ronaldo F. Cavalcante Rivelino M. 《Bulletin of environmental contamination and toxicology》2019,102(1):66-76
Bulletin of Environmental Contamination and Toxicology - This work describes the development of an analytical protocol combining cleanup by liquid–solid extraction and GC–MS for the... 相似文献
103.
Objectives
We explored levonorgestrel (LNG) concentrations, bleeding patterns and endometrial thickness in women with epilepsy (WWE) initiating an LNG-intrauterine device (IUD) co-administered with antiepileptic drugs (AEDs).Study design
This pilot study included 20 WWE ages 18 to 45 years with well-controlled seizures and stable AED regimens initiating a 52-mg LNG-IUD (20 mcg/d initial release). We collected blood and measured endometrial thickness before IUD placement and 21 days, 3 months and 6 months thereafter. Participants recorded bleeding/spotting daily. We measured total LNG (radioimmunoassay), serum hormone binding globulin (SHBG, immunoassay) and calculated the free LNG index. We compared total LNG, free LNG index, SHBG and endometrial thickness over time using a linear mixed-effects model.Results
Total LNG, free LNG index and SBHG levels remained stable from day 21 throughout. Endometrial thickness decreased from a median of 5.9 mm [interquartile range (IQR) 4.6–7.5] at day 21 to 3.3mm (2.8–4.9) by month 6 (p=0.02). Bleeding and spotting days decreased from a median of 16 (IQR 13–23) in month 1 to 6.5 (IQR 4–8.5) in month 6 regardless of AED regimen.Conclusion
Like women without epilepsy, WWE initiating the LNG-IUD experience stable total LNG concentrations and decreasing endometrial thickness and bleeding over the first 6 months of use.Implications
Like women without epilepsy, WWE using antiepileptic drugs can expect a stable LNG concentration and decreasing bleeding during the first 6 months of LNG-IUD use. Our data can be useful for guidance of WWE considering use the LNG-IUD. 相似文献104.
105.
106.
Miriam L. Haaksma Debora Rizzuto Inez H.G.B. Ramakers Sara Garcia-Ptacek Alessandra Marengoni Wiesje M. van der Flier Frans R.J. Verhey Marcel G.M. Olde Rikkert René J.F. Melis 《Journal of the American Medical Directors Association》2019,20(2):165-170.e2
Objectives
The predictive value of frailty and comorbidity, in addition to more readily available information, is not widely studied. We determined the incremental predictive value of frailty and comorbidity for mortality and institutionalization across both short and long prediction periods in persons with dementia.Design
Longitudinal clinical cohort study with a follow-up of institutionalization and mortality occurrence across 7 years after baseline.Setting and Participants
331 newly diagnosed dementia patients, originating from 3 Alzheimer centers (Amsterdam, Maastricht, and Nijmegen) in the Netherlands, contributed to the Clinical Course of Cognition and Comorbidity (4C) Study.Measures
We measured comorbidity burden using the Cumulative Illness Rating Scale for Geriatrics (CIRS-G) and constructed a Frailty Index (FI) based on 35 items. Time-to-death and time-to-institutionalization from dementia diagnosis onward were verified through linkage to the Dutch population registry.Results
After 7 years, 131 patients were institutionalized and 160 patients had died. Compared with a previously developed prediction model for survival in dementia, our Cox regression model showed a significant improvement in model concordance (U) after the addition of baseline CIRS-G or FI when examining mortality across 3 years (FI: U = 0.178, P = .005, CIRS-G: U = 0.180, P = .012), but not for mortality across 6 years (FI: U = 0.068, P = .176, CIRS-G: U = 0.084, P = .119). In a competing risk regression model for time-to-institutionalization, baseline CIRS-G and FI did not improve the prediction across any of the periods.Conclusions
Characteristics such as frailty and comorbidity change over time and therefore their predictive value is likely maximized in the short term. These results call for a shift in our approach to prognostic modeling for chronic diseases, focusing on yearly predictions rather than a single prediction across multiple years. Our findings underline the importance of considering possible fluctuations in predictors over time by performing regular longitudinal assessments in future studies as well as in clinical practice. 相似文献107.
Mieke R. Van Bockstal Marie C. Agahozo Linetta B. Koppert Carolien H.M. van Deurzen 《International journal of cancer. Journal international du cancer》2020,146(5):1189-1197
Ductal carcinoma in situ (DCIS) of the breast is a nonobligate precursor of invasive breast cancer, accounting for 20 % of screen-detected breast cancers. Little is known about the natural progression of DCIS because most patients undergo surgery upon diagnosis. Many DCIS patients are likely being overtreated, as it is believed that only around 50 % of DCIS will progress to invasive carcinoma. Robust prognostic markers for progression to invasive carcinoma are lacking. In the past, studies have investigated women who developed a recurrence after breast-conserving surgery (BCS) and compared them with those who did not. However, where there is no recurrence, the patient has probably been adequately treated. The present narrative review advocates a new research strategy, wherein only those patients with a recurrence are studied. Approximately half of the recurrences are invasive cancers, and half are DCIS. So-called “recurrences” are probably most often the result of residual disease. The new approach allows us to ask: why did some residual DCIS evolve to invasive cancers and others not? This novel strategy compares the group of patients that developed in situ recurrence with the group of patients that developed invasive recurrence after BCS. The differences between these groups could then be used to develop a robust risk stratification tool. This tool should estimate the risk of synchronous and metachronous invasive carcinoma when DCIS is diagnosed in a biopsy. Identification of DCIS patients at low risk for developing invasive carcinoma will individualize future therapy and prevent overtreatment. 相似文献
108.
SNAIL1 employs β-Catenin-LEF1 complexes to control colorectal cancer cell invasion and proliferation
109.
Emarene Kalaw Malcolm Lim Jamie R. Kutasovic Anna Sokolova Lucinda Taege Kate Johnstone James Bennett Jodi M. Saunus Colleen Niland Kaltin Ferguson Irma Gresshoff Mark Bettington Nirmala Pathmanathan Gary M. Tse David Papadimos Rajadurai Pathmanathan Gavin Harris Rin Yamaguchi Puay Hoon Tan Stephen Fox Sandra A. O’Toole Peter T. Simpson Sunil R. Lakhani Amy E. McCart Reed 《British journal of cancer》2020,123(11):1665
110.
Ki-Yong An Andria R. Morielli Dong-Woo Kang Christine M. Friedenreich Donald C. McKenzie Karen Gelmon John R. Mackey Robert D. Reid Kerry S. Courneya 《International journal of cancer. Journal international du cancer》2020,146(1):150-160
The Combined Aerobic and Resistance Exercise (CARE) Trial compared different types and doses of exercise performed during breast cancer chemotherapy. Here, we report the longer-term follow-up of patient-reported outcomes, health-related fitness and exercise behavior at 6, 12 and 24 months postintervention. A multicenter trial in Canada randomized 301 breast cancer patients initiating chemotherapy to thrice weekly, supervised exercise consisting of a standard dose of 25–30 min of aerobic exercise (STAN; n = 96), a higher dose of 50–60 min of aerobic exercise (HIGH; n = 101) or a combined dose of 50–60 min of aerobic and resistance exercise (COMB; n = 104) performed for the duration of chemotherapy (median of 17 weeks). Primary outcomes were patient-reported outcomes including quality of life, cancer-related symptoms and psychosocial outcomes. Secondary outcomes were objective health-related fitness (assessed at 12 months only) and self-reported exercise behavior. A total of 269 (89.4%) participants completed patient-reported outcomes at all three follow-up time points and 263 (87.4%) completed the health-related fitness assessment at 12-month follow-up. COMB was significantly superior to (i) STAN for sleep quality at 6-month follow-up (p = 0.027); (ii) HIGH for upper body muscular endurance at 12-month follow-up (p = 0.020); and (iii) HIGH for meeting the resistance exercise guideline at 6-month follow-up (p = 0.006). Moreover, self-reported meeting of the combined exercise guideline during follow-up was significantly associated with better patient-reported outcomes and health-related fitness. Performing combined exercise during and after breast cancer chemotherapy may result in better longer-term patient-reported outcomes and health-related fitness compared to performing aerobic exercise alone. 相似文献