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   4899篇
  免费   275篇
  国内免费   10篇
耳鼻咽喉   44篇
儿科学   75篇
妇产科学   63篇
基础医学   776篇
口腔科学   58篇
临床医学   568篇
内科学   981篇
皮肤病学   36篇
神经病学   663篇
特种医学   121篇
外科学   643篇
综合类   30篇
一般理论   1篇
预防医学   378篇
眼科学   112篇
药学   315篇
中国医学   1篇
肿瘤学   319篇
  2023年   26篇
  2022年   55篇
  2021年   92篇
  2020年   52篇
  2019年   56篇
  2018年   60篇
  2017年   52篇
  2016年   91篇
  2015年   122篇
  2014年   140篇
  2013年   204篇
  2012年   273篇
  2011年   339篇
  2010年   173篇
  2009年   234篇
  2008年   319篇
  2007年   360篇
  2006年   376篇
  2005年   377篇
  2004年   287篇
  2003年   264篇
  2002年   238篇
  2001年   81篇
  2000年   78篇
  1999年   85篇
  1998年   65篇
  1997年   51篇
  1996年   50篇
  1995年   30篇
  1994年   39篇
  1993年   52篇
  1992年   37篇
  1991年   41篇
  1990年   40篇
  1989年   30篇
  1988年   29篇
  1987年   30篇
  1986年   25篇
  1985年   20篇
  1984年   11篇
  1983年   18篇
  1982年   15篇
  1981年   10篇
  1980年   12篇
  1979年   12篇
  1975年   8篇
  1974年   9篇
  1973年   11篇
  1972年   9篇
  1932年   8篇
排序方式: 共有5184条查询结果,搜索用时 46 毫秒
991.
This study explored how contact with gay and lesbian persons affects adolescents' attitudes toward them, and whether this association is mediated or moderated by one's acceptance of gender non-conformity. We analyzed survey responses from 456 Dutch adolescents aged 12-15 who reported having no same-sex attractions. Data were collected in 2008 at 8 schools in Amsterdam, the Netherlands. Preliminary analyses showed that contact with lesbian/gay persons outside of school was positively associated with attitudes toward lesbians and gay men. Multilevel analyses showed that acceptance of gender non-conformity mediated rather than moderated the relationship between intergroup contact and sexual prejudice in males. The effect of intergroup contact on females' attitudes toward lesbian women was no longer significant in multilevel analyses. The findings suggest that attention to both intergroup contact and acceptance of gender non-conformity would enhance our understanding of attitudes toward homosexuality in adolescents.  相似文献   
992.
Phenotypic identification of Gram-negative bacteria from respiratory specimens of patients with cystic fibrosis carries a high risk of misidentification. Molecular identification techniques that use single-gene targets are also susceptible to error, including cross-reaction issues with other Gram-negative organisms. In this study, we have designed a Pseudomonas aeruginosa duplex real-time polymerase chain reaction (PCR) (PAduplex) assay targeting the ecfX and the gyrB genes. The PAduplex was evaluated against a panel of 91 clinical and environmental isolates that were presumptively identified as P. aeruginosa. The results were compared with those obtained using a commercial biochemical identification kit and several other P. aeruginosa PCR assays. The results showed that the PAduplex assay is highly suitable for routine identification of P. aeruginosa isolates from clinical or environmental samples. The 2-target format provides simultaneous confirmation of P. aeruginosa identity where both the ecfX and gyrB PCR reactions are positive and may also reduce the potential for false negatives caused by sequence variation in primer or probe targets.  相似文献   
993.
994.
995.
Purpose: Chronic cardiac transplantation denervation (i.e., global sympathetic denervation with myocardial catecholamine depletion, plus parasympathetic denervation) is known to inhibit myocardial oxidation of glucose. It is not known whether this is due to increased utilization of lactate, lipid or ketone bodies. The purpose of the present study was to test the hypothesis that the extraction and contribution of blood-borne fatty acids (FA) to overall oxidative energy conversion is increased. Methods: In anaesthetised dogs (control n = 6, cardiac denervated n = 6), we investigated fatty acid (FA) utilization. The studies were made at least four weeks after surgical cardiac denervation. Measurements were made of total FAs and with a radio-labelled tracer (U-14C palmitate). Results: The contribution of FA utilisation to overall substrate oxidation rose from 31% (control) to 48% (cardiac denervated). The increase in the ratio (%) of CO2 production from palmitate oxidation to total CO2 production increased from 4.0 ± 1.8 (control) to 10.6 ± 5.8 (denervated, p = 0.04). The time from uptake of FA to release of CO2 product was unaltered. Conclusion: We conclude that the contribution of FA oxidation to overall energy conversion is increased in chronically denervated hearts, which is postulated to result from a decline in the active form of pyruvate dehydrogenase. This would appear to be a result of chronic catecholamine depletion.  相似文献   
996.
Background: Hypoxemia is common in septic acute lung failure. Therapy is mainly supportive, and most trials using specific inhibitors of key inflammatory mediators (i.e., tumor necrosis factor [alpha], interleukin 1) have failed to prove beneficial. The authors investigated if a nonspecific blood purification technique, using zero-balanced high-volume continuous venovenous hemofiltration (CVVH), might improve arterial oxygenation in a fluid-resuscitated porcine model of endotoxin-induced acute lung injury.

Methods: Piglets of both sexes weighing 25-30 kg were anesthetized and mechanically ventilated. After baseline measurements, animals received an intravenous infusion of 0.5 mg/kg endotoxin (Escherichia coli lipopolysaccharide). One hour after endotoxin, animals were randomly assigned to either treatment with CVVH (endotoxin + hemofiltration, n = 6) or spontaneous course (endotoxin, n = 6). At 4 h after randomization, animals were killed. Hemofiltration was performed from femoral vein to femoral vein using a standard circuit with an EF60 polysulphone hemofilter.

Results: Endotoxin challenge induced arterial hypoxemia, an increase in peak inspiratory pressure, pulmonary hypertension, and systemic hypotension. Treatment with CVVH did not improve systemic or pulmonary hemodynamics. However, arterial oxygenation was increased in endotoxin-challenged animals at 5 h after completion of endotoxin infusion, as compared with animals not receiving CVVH (arterial oxygen tension, 268 +/- 33 vs. 176 +/- 67 mmHg, respectively, P < 0.01). In addition, treatment with CVVH attenuated the endotoxin-induced increase in peak inspiratory pressure and increased lung compliance.  相似文献   

997.
998.
Metabolic imaging and early response assessment by positron emission tomography (PET) are gaining importance in guiding treatment of localised and metastatic gastrointestinal tumours. During a workshop organised by the European Organisation of Research and Treatment of Cancer (EORTC) Gastrointestinal Tract Cancer Group the most relevant research questions, methodological aspects and unmet clinical needs in this disease were discussed. Potential future trials were drafted. This paper reviews the lectures and discussions held during this workshop and summarises the action points for the further investigation of metabolic imaging to guide treatment in gastrointestinal tumours.  相似文献   
999.
Immunostimulatory cytidyl guanosyl (CpG) motifs are of great interest as cancer vaccine adjuvants. They act as potent inducers of Th1 responses, including the activation of cytotoxic CD8(+) T lymphocytes (CTL). Whereas animal models have provided clear evidence that CpG enhances antitumor immunity, clinical trials in humans have thus far been less successful. Applying cryosurgery as an instant in situ tumor destruction technique, we now show that timing of CpG administration crucially affects colocalization of antigen and CpG within EEA-1(+) and LAMP-1(+) compartments within dendritic cells in vivo. Moreover, antigen/CpG colocalization is directly correlated with antigen cross-presentation, the presence of CTL, and protective antitumor immunity. Thus, failure or success of CpG as a vaccine adjuvant may depend on colocalization of antigen/CpG inside DCs and hence on the timing of CpG administration. These data might aid in the design of future immunotherapeutic strategies for cancer patients.  相似文献   
1000.
A 20-year-old patient with a chronic fistula located at the left scapular region caused by a deep located subscapular bronchogenic cyst is described.  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