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   1267992篇
  免费   92905篇
  国内免费   1926篇
耳鼻咽喉   18164篇
儿科学   42131篇
妇产科学   37677篇
基础医学   185600篇
口腔科学   35326篇
临床医学   107088篇
内科学   248887篇
皮肤病学   26441篇
神经病学   98452篇
特种医学   49967篇
外国民族医学   366篇
外科学   197019篇
综合类   26468篇
一般理论   300篇
预防医学   91819篇
眼科学   28912篇
药学   97474篇
  1篇
中国医学   2434篇
肿瘤学   68297篇
  2018年   11639篇
  2015年   11489篇
  2014年   15957篇
  2013年   24317篇
  2012年   33554篇
  2011年   35940篇
  2010年   21176篇
  2009年   19981篇
  2008年   34982篇
  2007年   37948篇
  2006年   38501篇
  2005年   37822篇
  2004年   36397篇
  2003年   35320篇
  2002年   34892篇
  2001年   58046篇
  2000年   59460篇
  1999年   50399篇
  1998年   13496篇
  1997年   12041篇
  1996年   12294篇
  1995年   12283篇
  1994年   11710篇
  1993年   10823篇
  1992年   40944篇
  1991年   40353篇
  1990年   39858篇
  1989年   38679篇
  1988年   36089篇
  1987年   35333篇
  1986年   33704篇
  1985年   32128篇
  1984年   23901篇
  1983年   20785篇
  1982年   12324篇
  1981年   10881篇
  1980年   10152篇
  1979年   22614篇
  1978年   15838篇
  1977年   13678篇
  1976年   12905篇
  1975年   14143篇
  1974年   16642篇
  1973年   16024篇
  1972年   15288篇
  1971年   14208篇
  1970年   13192篇
  1969年   12708篇
  1968年   11967篇
  1967年   10454篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
ObjectiveTo determine prognostic factors and survival patterns for different treatment modalities for nasal cavity (NC) and paranasal sinus (PS) mucosal melanoma (MM).MethodsPatients from 1973 to 2013 were analyzed using the Surveillance, Epidemiology, and End Results (SEER) database. Kaplan-Meier method and multivariable cox proportional hazard modeling were used for survival analyses.ResultsOf 928 cases of mucosal melanoma (NC = 632, PS = 302), increasing age (Hazard Ratio [HR]:1.05/year, p < 0.001), T4 tumors (HR: 1.81, p = 0.02), N1 status (HR: 6.61, p < 0.001), and PS disease (HR: 1.50, p < 0.001) were associated with worse survival. Median survival length was lower for PS versus NC (16 versus 26 months, p < 0.001). Surgery and surgery + radiation therapy (RT) improved survival over non-treatment or RT alone (p < 0.001). Adding RT to surgery did not yield a survival difference compared with surgery alone (p = 0.43). Five-year survival rates for surgery and surgery + RT were similar, at 27.7% and 25.1% (p = 0.43).ConclusionSurgery increased survival significantly over RT alone. RT following surgical resection did not improve survival.  相似文献   
2.
3.
Pituitary - Our aim was to investigate the changes in the composition of oral and gut microbiota in patients with newly diagnosed acromegaly and their relationship with IGF-1 levels. Oral and fecal...  相似文献   
4.
Pharmaceutical Research - The quality testing and approval procedure for most pharmaceutical products is a streamlined process with standardized procedures for the determination of critical quality...  相似文献   
5.
Graefe's Archive for Clinical and Experimental Ophthalmology - To investigate comorbidities and medications associated with acute (ASCH) and delayed (DSCH) suprachoroidal hemorrhage (SCH), and...  相似文献   
6.
Background

Vaccination prevents severe morbidity and mortality from COVID-19 in the general population. The immunogenicity and efficacy of SARS-CoV-2 vaccines in patients with antibody deficiency is poorly understood.

Objectives

COVID-19 in patients with antibody deficiency (COV-AD) is a multi-site UK study that aims to determine the immune response to SARS-CoV-2 infection and vaccination in patients with primary or secondary antibody deficiency, a population that suffers from severe and recurrent infection and does not respond well to vaccination.

Methods

Individuals on immunoglobulin replacement therapy or with an IgG less than 4 g/L receiving antibiotic prophylaxis were recruited from April 2021. Serological and cellular responses were determined using ELISA, live-virus neutralisation and interferon gamma release assays. SARS-CoV-2 infection and clearance were determined by PCR from serial nasopharyngeal swabs.

Results

A total of 5.6% (n?=?320) of the cohort reported prior SARS-CoV-2 infection, but only 0.3% remained PCR positive on study entry. Seropositivity, following two doses of SARS-CoV-2 vaccination, was 54.8% (n?=?168) compared with 100% of healthy controls (n?=?205). The magnitude of the antibody response and its neutralising capacity were both significantly reduced compared to controls. Participants vaccinated with the Pfizer/BioNTech vaccine were more likely to be seropositive (65.7% vs. 48.0%, p?=?0.03) and have higher antibody levels compared with the AstraZeneca vaccine (IgGAM ratio 3.73 vs. 2.39, p?=?0.0003). T cell responses post vaccination was demonstrable in 46.2% of participants and were associated with better antibody responses but there was no difference between the two vaccines. Eleven vaccine-breakthrough infections have occurred to date, 10 of them in recipients of the AstraZeneca vaccine.

Conclusion

SARS-CoV-2 vaccines demonstrate reduced immunogenicity in patients with antibody deficiency with evidence of vaccine breakthrough infection.

  相似文献   
7.
Oral squamous cell carcinomas (OSCCs) develop in genetically altered epithelium in the mucosal lining, also coined as fields, which are mostly not visible but occasionally present as white oral leukoplakia (OL) lesions. We developed a noninvasive genetic assay using next-generation sequencing (NGS) on brushed cells to detect the presence of genetically altered fields, including those that are not macroscopically visible. The assay demonstrated high accuracy in OL patients when brush samples were compared with biopsies as gold standard. In a cohort of Fanconi anemia patients, detection of mutations in prospectively collected oral brushes predicted oral cancer also when visible abnormalities were absent. We further provide insight in the molecular landscape of OL with frequent changes of TP53, FAT1 and NOTCH1. NGS analysis of noninvasively collected samples offers a highly accurate method to detect genetically altered fields in the oral cavity, and predicts development of OSCC in high-risk individuals. Noninvasive genetic screening can be employed to screen high-risk populations for cancer and precancer, map the extension of OL lesions beyond what is visible, map the oral cavity for precancerous changes even when visible abnormalities are absent, test accuracy of promising imaging modalities, monitor interventions and determine genetic progression as well as the natural history of the disease in the human patient.  相似文献   
8.
Galactosyl transferase knock-out pig lungs fail rapidly in baboons. Based on previously identified lung xenograft injury mechanisms, additional expression of human complement and coagulation pathway regulatory proteins, anti-inflammatory enzymes and self-recognition receptors, and knock-down of the β4Gal xenoantigen were tested in various combinations. Transient life-supporting GalTKO.hCD46 lung function was consistently observed in association with either hEPCR (n = 15), hTBM (n = 4), or hEPCR.hTFPI (n = 11), but the loss of vascular barrier function in the xenograft and systemic inflammation in the recipient typically occurred within 24 h. Co-expression of hEPCR and hTBM (n = 11) and additionally blocking multiple pro-inflammatory innate and adaptive immune mechanisms was more consistently associated with survival >1 day, with one recipient surviving for 31 days. Combining targeted genetic modifications to the lung xenograft with selective innate and adaptive immune suppression enables prolonged initial life-supporting lung function and extends lung xenograft recipient survival, and illustrates residual barriers and candidate treatment strategies that may enable the clinical application of other organ xenografts.  相似文献   
9.
Jones type fifth metatarsal fractures pose a challenge to the foot and ankle surgeon, given documented high nonunion rates as well as high complication rates including hardware prominence, nerve injury, and screw breakage for existing treatment modalities including screw and plantar plate fixation. We call for the design of innovative Jones-fracture specific implants which contour to the natural curve of the fifth metatarsal. Future research should aim to expand upon existing literature for Jones fracture fixation and evaluate efficacy of novel implants which are designed to address unacceptably high complication rates for existing treatment modalities.  相似文献   
10.
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