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   1331211篇
  免费   94958篇
  国内免费   3224篇
耳鼻咽喉   19716篇
儿科学   40132篇
妇产科学   38657篇
基础医学   186169篇
口腔科学   39845篇
临床医学   111985篇
内科学   259974篇
皮肤病学   30261篇
神经病学   105859篇
特种医学   53860篇
外国民族医学   436篇
外科学   207854篇
综合类   32058篇
一般理论   435篇
预防医学   91743篇
眼科学   31417篇
药学   100201篇
  5篇
中国医学   3297篇
肿瘤学   75489篇
  2018年   11726篇
  2015年   11965篇
  2014年   16933篇
  2013年   25457篇
  2012年   33368篇
  2011年   35222篇
  2010年   20944篇
  2009年   20379篇
  2008年   33804篇
  2007年   37005篇
  2006年   37505篇
  2005年   36219篇
  2004年   35429篇
  2003年   34448篇
  2002年   33897篇
  2001年   63837篇
  2000年   65347篇
  1999年   55117篇
  1998年   13896篇
  1997年   12665篇
  1996年   12147篇
  1995年   12169篇
  1994年   11413篇
  1992年   42714篇
  1991年   41282篇
  1990年   40526篇
  1989年   39523篇
  1988年   36927篇
  1987年   36399篇
  1986年   34877篇
  1985年   33099篇
  1984年   24784篇
  1983年   20986篇
  1982年   12607篇
  1981年   11504篇
  1980年   10707篇
  1979年   23862篇
  1978年   17013篇
  1977年   14752篇
  1976年   13306篇
  1975年   15184篇
  1974年   18016篇
  1973年   17515篇
  1972年   16770篇
  1971年   15673篇
  1970年   14858篇
  1969年   14304篇
  1968年   13431篇
  1967年   11987篇
  1966年   11240篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Tamoxifen prevents recurrence of breast cancer and is suggested for preventive risk-reducing therapy. Tamoxifen reduces mammographic density, a proxy for therapy response, but little is known about its effects in remodelling normal breast tissue. Our study, a substudy within the double-blinded dose-determination trial KARISMA, investigated tamoxifen-specific changes in breast tissue composition and histological markers in healthy women. We included 83 healthy women randomised to 6 months daily intake of 20, 10, 5, 2.5, 1 mg of tamoxifen or placebo. The groups were combined to “no dose” (0-1 mg), “low-dose” (2.5-5 mg) or “high-dose” (10-20 mg) of tamoxifen. Ultrasound-guided biopsies were collected before and after tamoxifen exposure. In each biopsy, epithelial, stromal and adipose tissues was quantified, and expression of epithelial and stromal Ki67, oestrogen receptor (ER) and progesterone receptor (PR) analysed. Mammographic density using STRATUS was measured at baseline and end-of-tamoxifen-exposure. We found that different doses of tamoxifen reduced mammographic density and glandular-epithelial area in premenopausal women and associated with reduced epithelium and increased adipose tissue. High-dose tamoxifen also decreased epithelial ER and PR expressions in premenopausal women. Premenopausal women with the greatest reduction in proliferation also had the greatest epithelial reduction. In postmenopausal women, high-dose tamoxifen decreased the epithelial area with no measurable density decrease. Tamoxifen at both low and high doses influences breast tissue composition and expression of histological markers in the normal breast. Our findings connect epithelial proliferation with tissue remodelling in premenopausal women and provide novel insights to understanding biological mechanisms of primary prevention with tamoxifen.  相似文献   
2.
3.
Graefe's Archive for Clinical and Experimental Ophthalmology - The purpose was to ascertain if any relation exists between the elevated intraocular pressure (IOP) in patients with...  相似文献   
4.

目的:对比观察不同程度屈光参差单眼近视儿童配戴角膜塑形镜1a的双眼近视进展情况。

方法:回顾性病例对照研究。收集2018-06/2019-06于西安市第一医院就诊并验配角膜塑形镜的8~12岁的单眼近视屈光参差患者60例,双眼等效球镜(SE)差值≥2.5D为高度屈光参差组30例,1.0D≤双眼SE差值<2.5D为低度屈光参差组30例。比较两组患者戴镜6mo,1a的双眼眼轴长度(AL)和非戴镜眼SE变化情况。

结果:随访6mo,1a时,高度屈光参差组戴镜眼眼轴增长均少于低度屈光参差组(P<0.001),非戴镜眼眼轴增长量和SE增长均大于低度屈光参差组(均P<0.001),且高度屈光参差组双眼眼轴差缩短幅度均大于低度屈光参差组(P<0.05)。相关性分析显示戴镜前屈光参差度和双眼眼轴差缩短量具有相关性(F=0.293、0.458,均P<0.001)。

结论:单眼近视屈光参差儿童在配戴角膜塑形镜后,高度屈光参差者较低度屈光参差者戴镜眼眼轴增长更慢,而非戴镜眼眼轴和等效球镜度进展更快。配戴角膜塑形镜可有效缩小屈光参差,且戴镜前屈光参差程度越大,双眼轴差缩小越多。  相似文献   

5.
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   
6.
Journal of Developmental and Physical Disabilities - Caregiver support is an important contextual factor in the daily functioning of children with cerebral palsy (CP), but few studies have examined...  相似文献   
7.
Irritable bowel syndrome (IBS) is an important health care concern. Alterations in the microbiota of the gut-brain axis may be linked to the pathophysiology of IBS. Some dietary intake could contribute to produce various metabolites including D-amino acids by the fermentation by the gut microbiota. D-amino acids are the enantiomeric counterparts of L-amino acids, in general, which could play key roles in cellular physiological processes against various oxidative stresses. Therefore, the presence of D-amino acids has been shown to be linked to the protection of several organs in the body. In particular, the gut microbiota could play significant roles in the stability of emotion via the action of D-amino acids. Here, we would like to shed light on the roles of D-amino acids, which could be used for the treatment of IBS.  相似文献   
8.
Graefe's Archive for Clinical and Experimental Ophthalmology - Ferromagnetic foreign bodies (FFB) present during magnetic resonance imaging (MRI) explorations can lead to tissue injury due to...  相似文献   
9.
Bundesgesundheitsblatt - Gesundheitsforschung - Gesundheitsschutz -  相似文献   
10.
Background: Nanotechnology is receiving greater attention these days as a result of its applications in numerous industrial, medical, and environmental fields. Objective: To synthesize silver nanoparticles with a green alga, Cladophora glomerata, and determine their inhibitory activity against tumor cell (MCF-7) and transgenic mouse cell (L20B) lines. Materials and Methods: Methanol extract was prepared from Cladophora glomerata and used as a safe factory for the synthesis of silver nanoparticles (AgNPs). UV-visible spectrophotometer, X-ray diffraction, scanning electron microscopy, and EDX analyses were used to characterize the biosynthesized AgNPs. The anti-tumor activity of the phycosynthesized AgNPs was tested against the MCF-7 and L20B cell lines. Furthermore, the bioactive compounds in the algal extract were determined by gas chromatography-mass spectroscopy (GC-MS). Results: The phycosynthesis produced clusters of spherical and polydispersed cuboidal pure AgNPs with an average size of 32 nm. The phycosynthesized AgNPs possess anti-cancer and anti-tumor activities on the MCF-7 and L20B cell lines, with significant anti-proliferation percentages of 52.8 and 65.8%, respectively, after 48 hours of treatment with 100 μg/ml AgNPs. Both treated cell lines showed a significant change in cellular shape and tissue detachment. The GC-MS analysis revealed the presence of a high proportion of octadecanoic acid (47.59%) and hexadecanoic acid (14.97%). Conclusion: Cladophora glomerata contains chemicals that improve the stabilization and reduction properties of the nanoparticles. It can be used as a safe, local, and natural source for the synthesis of AgNPs and can also be used as a benign factory for many other metal nanoparticles. The phycosynthesized AgNPs have anti-cancer and anti-tumor activities on the test cell lines and provide an insight into the potential for using them as a trend in cancer nanotherapy.  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