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   4639篇
  免费   306篇
  国内免费   16篇
耳鼻咽喉   42篇
儿科学   156篇
妇产科学   133篇
基础医学   513篇
口腔科学   113篇
临床医学   559篇
内科学   821篇
皮肤病学   61篇
神经病学   325篇
特种医学   88篇
外科学   549篇
综合类   37篇
一般理论   5篇
预防医学   524篇
眼科学   72篇
药学   321篇
中国医学   7篇
肿瘤学   635篇
  2023年   26篇
  2022年   41篇
  2021年   101篇
  2020年   88篇
  2019年   100篇
  2018年   126篇
  2017年   108篇
  2016年   97篇
  2015年   130篇
  2014年   178篇
  2013年   261篇
  2012年   311篇
  2011年   340篇
  2010年   218篇
  2009年   162篇
  2008年   319篇
  2007年   309篇
  2006年   321篇
  2005年   270篇
  2004年   261篇
  2003年   248篇
  2002年   236篇
  2001年   55篇
  2000年   29篇
  1999年   45篇
  1998年   59篇
  1997年   56篇
  1996年   46篇
  1995年   45篇
  1994年   31篇
  1993年   34篇
  1992年   31篇
  1991年   36篇
  1990年   27篇
  1989年   17篇
  1988年   14篇
  1987年   18篇
  1986年   9篇
  1985年   14篇
  1984年   24篇
  1983年   17篇
  1982年   18篇
  1981年   12篇
  1980年   17篇
  1979年   6篇
  1978年   8篇
  1977年   6篇
  1976年   5篇
  1975年   5篇
  1968年   5篇
排序方式: 共有4961条查询结果,搜索用时 31 毫秒
71.
Chromosomal aberrations (CAs) in human peripheral blood lymphocytes (PBL) measured with the conventional cytogenetic assay have been used for human biomonitoring of genotoxic exposure for decades. CA frequency in peripheral blood is a marker of cancer susceptibility. Previous studies have shown associations between genetic variants in metabolic pathway, DNA repair and major mitotic checkpoint genes and CAs. We conducted a genome-wide association study on 576 individuals from the Czech Republic and Slovakia followed by a replication in two different sample sets of 482 (replication 1) and 1288 (replication 2) samples. To have a broad look at the genetic susceptibility associated with CA frequency, the sample sets composed of individuals either differentially exposed to smoking, occupational/environmental hazards, or they were untreated cancer patients. Phenotypes were divided into chromosome- and chromatid-type aberrations (CSAs and CTAs, respectively) and total chromosomal aberrations (CAtot). The arbitrary cutoff point between individuals with high and low CA frequency was 2% for CAtot and 1% for CSA and CTA. The data were analyzed using age, sex, occupation/cancer and smoking history as covariates. Altogether 11 loci reached the P-value of 10−5 in the GWAS. Replication 1 supported the association of rs1383997 (8q13.3) and rs2824215 (21q21.1) in CAtot and rs983889 (5p15.1) in CTA analysis. These loci were found to be associated with genes involved in mitosis, response to environmental and chemical factors and genes involved in syndromes linked to chromosomal abnormalities. Identification of new genetic variants for the frequency of CAs offers prediction tools for cancer risk in future. Environ. Mol. Mutagen. 60:17–28, 2019. © 2018 Wiley Periodicals, Inc.  相似文献   
72.
73.
The Young Forum of the German Society for Thoracic and Cardiovascular Surgery (GSTCVS) was founded during the 41st annual meeting of the German Society for Thoracic and Cardiovascular Surgery in Freiburg in 2012. The idea was to establish a stronger representation of the needs and problems of young colleagues within the GSTCVS and to improve the communication between residents, students and representatives of the GSTCVS. The aims are to improve residency programs in Germany in general and in particular, to improve the clinical and scientific exchange of residents in Germany, Europe and foreign countries. Attempts will also be made to find solutions that could lead to a better work-life balance in cardiothoracic surgery and therefore make this field more attractive for young physicians.  相似文献   
74.

Background  

Atrial fibrillation (AF) is the most common sustained dysrhythmia and appears to be an independent predictor of sudden cardiac death. The irregular ventricular rhythm contains both linear and non-linear patterns; however, it remains unclear whether vagally mediated effects are present within these patterns.  相似文献   
75.
Epichloë festucae is an endophytic fungus that infects systemically the aerial tissues of the host grass Festuca rubra. This fungus is transmitted vertically from the mother plant to seeds. Hypothetically, the presence of E. festucae could affect the infection of a plant by other fungal species. This could occur if E. festucae metabolites produced in planta interfere negatively with other fungal infections; or alternatively, if the modulation of plant defenses by the endophyte favour further fungal infections. We have analyzed the presence of culturable non-systemic endophytes in plants of F. rubra infected (E+) and not infected (E?) by E. festucae in two subarctic habitats, meadows and riverbanks in Northern Finland. The observed non-systemic endophyte infection frequencies were similar among E+ and E? plants from riverbanks, and E+ plants from meadows. In contrast to these, the infection frequency was significantly lower in E? plants from meadows. This result suggests that the presence of E. festucae is not a main factor determining the presence of non-systemic endophytes in plants. Instead, plant genetic characteristics related to compatibility with E. festucae and other endophytes in the more stable meadow populations might play a role in these fungus–fungus–plant interactions. As a result of the survey, 18 different taxa of non-systemic endophytes were identified in plants of F. rubra. All were ascomycetes except for one basidiomycete. Three endophytic taxa could not be ascribed to a genus, but sequence data indicated that they were conspecific with other unidentified endophytes that have been isolated in cold biomes at different locations.  相似文献   
76.
77.
78.
The aim of this retrospective observational study was to evaluate age, length of hospital stay and development of complications in children hospitalized with community- or nosocomially- acquired rotavirus gastroenteritis (RV GE). In total, medical records of 984 children with RV GE were analysed retrospectively. The median age was 13.8 months (3 weeks to 99 months) in children with community acquired RV GE (n=723) and 9.0 months (range 3 weeks to 82 months) in children with nosocomially acquired RV GE (n=261). During this 11-y surveillance, only 2 children were admitted twice for a RV GE, suggesting development of subsequent protective immunity against severe rotavirus gastroenteritis after the first episode. Complications occurred in 16.5% of the children with community acquired RV GE and only in 1.9% of the nosocomially acquired RV GE. Identified complications in children with community acquired RV GE were: severe dehydration resulting in intensive care (1.7%), death (0.1%), hypertonic dehydration (9.1%), seizures (4.0%) and encephalitis with abnormal EEG (1.7%). The median age of children in need of intensive care was 9.1 months and in those developing hypertonic dehydration 10.8 months, both significantly lower than in children with no complications (p<0.05). Interestingly, the age of children developing seizures and signs of encephalitis was significantly higher than in children with no complications (p<0.01).  相似文献   
79.
80.
Social exploitation of vitellogenin   总被引:13,自引:0,他引:13       下载免费PDF全文
Vitellogenin is a female-specific glucolipoprotein yolk precursor produced by all oviparous animals. Vitellogenin expression is under hormonal control, and the protein is generally synthesized directly before yolk deposition. In the honeybee (Apis mellifera), vitellogenin is not only synthesized by the reproductive queen, but also by the functionally sterile workers. In summer, the worker population consists of a hive bee group performing a multitude of tasks including nursing inside the nest, and a forager group specialized in collecting nectar, pollen, water, and propolis. Vitellogenin is synthesized in large quantities by hive bees. When hive bees develop into foragers, their juvenile hormone titers increase, and this causes cessation of their vitellogenin production. This inverse relationship between vitellogenin synthesis and juvenile hormone is opposite to the norm in insects, and the underlying proximate processes and life-history reasons are still not understood. Here we document an alternative use of vitellogenin by showing that it is a source for the proteinaceous royal jelly that is produced by the hive bees. Hive bees use the jelly to feed larvae, queen, workers, and drones. This finding suggests that the evolution of a brood-rearing worker class and a specialized forager class in an advanced eusocial insect society has been directed by an alternative utilization of yolk protein.  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