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   179858篇
  免费   1126篇
  国内免费   47篇
耳鼻咽喉   1144篇
儿科学   6771篇
妇产科学   3084篇
基础医学   17041篇
口腔科学   1662篇
临床医学   12612篇
内科学   32033篇
皮肤病学   804篇
神经病学   16627篇
特种医学   9129篇
外科学   29585篇
综合类   2347篇
一般理论   1篇
预防医学   18150篇
眼科学   2760篇
药学   9797篇
中国医学   689篇
肿瘤学   16795篇
  2023年   38篇
  2022年   78篇
  2021年   146篇
  2020年   71篇
  2019年   104篇
  2018年   22007篇
  2017年   17423篇
  2016年   19605篇
  2015年   1001篇
  2014年   926篇
  2013年   920篇
  2012年   7189篇
  2011年   21200篇
  2010年   18950篇
  2009年   11625篇
  2008年   19742篇
  2007年   21941篇
  2006年   815篇
  2005年   2452篇
  2004年   3646篇
  2003年   4661篇
  2002年   2851篇
  2001年   347篇
  2000年   471篇
  1999年   255篇
  1998年   301篇
  1997年   267篇
  1996年   139篇
  1995年   148篇
  1994年   149篇
  1993年   113篇
  1992年   77篇
  1991年   127篇
  1990年   169篇
  1989年   111篇
  1988年   83篇
  1987年   77篇
  1986年   48篇
  1985年   51篇
  1984年   48篇
  1983年   42篇
  1982年   48篇
  1980年   53篇
  1974年   24篇
  1968年   24篇
  1938年   60篇
  1937年   25篇
  1934年   30篇
  1932年   56篇
  1930年   46篇
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
991.
In May 2016, thirteen dogs housed in backyards within a single neighborhood were reported to have developed convulsions and died within a 24 h period. An investigation of the scene by law enforcement resulted in submission of eight dogs for postmortem examination. It was suspected that a rapid acting toxin was the cause of death. A gas chromatography-mass spectrophotometry (GC-MS) protocol combined with thin-layer chromatography that allows screening for common convulsants failed to identify a toxin in either pooled gastric content or liver samples from select cases. After consultation with a veterinary toxicologist, sodium fluoroacetate poisoning was investigated. Sodium fluoroacetate, also known as 1080, is a pesticide that was available in the United States from the 1940’s to the 1970’s, but since 1972 has been banned or under EPA restricted use. When gastric content was re-tested using a GC-MS protocol with selective fluoroacetate ion monitoring and carbon 14 radiolabeling to facilitate quantification, 379 ppb sodium fluoroacetate was detected in a pooled gastric content sample. In spite of its banned status, sodium fluoroacetate remains a rarely reported cause of malicious poisoning in domestic dogs in the United Sates. This compound is highly toxic and is capable of causing death in dogs, humans, other mammals, and insects in ingested quantities as small as a few droplets. Even when geographic or historical proximity to a source is not evident, this intoxication should be considered in dogs exhibiting compatible clinical signs.  相似文献   
992.
Magnesium, which is an essential trace element that plays a key role in several cellular processes, is a major component of bone; however, its relationship with risk of major bone fractures is uncertain. We aimed to investigate the association of baseline serum magnesium concentrations with risk of incident fractures. We analyzed data on 2245 men aged 42–61 years in the Kuopio Ischemic Heart Disease prospective cohort study, with the assessment of serum magnesium measurements and dietary intakes made at baseline. Hazard ratios [95% confidence intervals (CI)] for incident total (femoral, humeral, and forearm) and femoral fractures were assessed. During a median follow-up of 25.6 years, 123 total fractures were recorded. Serum magnesium was non-linearly associated with risk of total fractures. In age-adjusted Cox regression analysis, the hazard ratio (HR) (95% CIs) for total fractures in a comparison of the bottom quartile versus top quartile of magnesium concentrations was 2.10 (1.30–3.41), which persisted on adjustment for several established risk factors 1.99 (1.23–3.24). The association remained consistent on further adjustment for renal function, socioeconomic status, total energy intake, and several trace elements 1.80 (1.10–2.94). The corresponding adjusted HRs for femoral fractures were 2.56 (1.38–4.76), 2.43 (1.30–4.53) and 2.13 (1.13–3.99) respectively. There was no evidence of an association of dietary magnesium intake with risk of any fractures. In middle-aged Caucasian men, low serum magnesium is strongly and independently associated with an increased risk of fractures. Further research is needed to assess the potential relevance of serum magnesium in the prevention of fractures.  相似文献   
993.
We report a case of acquired thrombotic thrombocytopenic purpura (TTP) in a 34-year old patient with a prior diagnosis of systemic lupus erythematosis (SLE) who was recently started on hydroxychloroquine. Presenting symptoms included fevers, sore throat and productive cough with progressive weakness, dyspnea on exertion, hemoptysis and dark urine. Initial laboratory abnormalities were consistent with an acute microangiopathic hemolytic anemia and severe thrombocytopenia. At the time of admission, the patient’s lupus was highly active as evident by his high SLE Disease Activity Index (SLEDAI) score. He was later also found to have severely reduced ADAMTS-13 levels and a positive antibody assay. This case highlights the occasional difficulty in pinpointing the exact etiology of TTP as well as establishes a possible novel drug association between hydroxychloroquine and TTP development.  相似文献   
994.
Working in an interdisciplinary manner at the crossroads of alcohol and HIV research is a challenge. This paper presents six novel approaches that could be applied to activities at the intersection of alcohol and HIV. These approaches are (i) address the fact that the availability of new technology is unevenly distributed around the world, (ii) use technology to move beyond both paper and digital surveys, (iii) introduce a focus on advocacy and partnerships with large technology companies, (iv) harness technological innovation to utilise digital counselling, (v) explore the use of virtual reality in both research and delivering interventions, and (vi) consider alternative funding models to those currently in existence to improve efficiencies and innovations. Aiming to understand the interplay of alcohol and HIV will require creativity. The six approaches outlines in this paper provide possible directions from which new approaches may emerge.  相似文献   
995.
996.
997.
Endothelial cell proliferation is a key process during vascular growth but its kinetics could only be assessed in vitro or ex vivo so far. To enable the monitoring and quantification of cell cycle kinetics in vivo, we have generated transgenic mice expressing an eGFP-anillin construct under control of the endothelial-specific Flt-1 promoter. This construct labels the nuclei of endothelial cells in late G1, S and G2 phase and changes its localization during the different stages of M phase, thereby enabling the monitoring of EC proliferation and cytokinesis. In Flt-1/eGFP-anillin mice, we found eGFP+ signals specifically in Ki67+/PECAM+ endothelial cells during vascular development. Quantification using this cell cycle reporter in embryos revealed a decline in endothelial cell proliferation between E9.5 to E12.5. By time-lapse microscopy, we determined the length of different cell cycle phases in embryonic endothelial cells in vivo and found a M phase duration of about 80 min with 2/3 covering karyokinesis and 1/3 cytokinesis. Thus, we have generated a versatile transgenic system for the accurate assessment of endothelial cell cycle dynamics in vitro and in vivo.  相似文献   
998.
Breast cancer is the most common malignancy among women and the second leading cause of mortality due to cancer worldwide. The complexity of breast cancer resembles an intricate ecosystem comprising various cleverly designed interaction levels of internal and external factors to generate a pliable context in the clonal evolution of breast cancer cells. Principally, the complex entity can become evident toward delineating a number of significant variations in the specific fields of breast cancer analyses, including the molecular, physiological, and morphological characteristics, clinical presentations, risk factors, the histopathological conditions, and response to systemic therapy regarding the maintenance of tumor as a whole. In hindsight, various classification systems developing based on specific inclusion criteria have indisputably changed both our appreciation of the biological demeanor of breast cancer and the main strategies for designing tailored therapy regimens through the proper evaluation of diagnosis and prognostication of given specimens. Here, we endeavor to provide a general overview of different types of breast cancer classification as well as the clinical acceptance of their applications along with the latest findings in this area. Taken together, the major significance of breast cancer management that can be ascertained by operational convergent points of its stratification areas is owing to the fact that the achievement of individualized and targeted therapy may denounce new horizons of surveillance and treatment strategies in which they may function as a rheostat of specific therapy regimens toward reducing the detected distances between experimental data and operating options in clinical practice.  相似文献   
999.
1000.
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