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   5556篇
  免费   379篇
  国内免费   19篇
耳鼻咽喉   49篇
儿科学   92篇
妇产科学   76篇
基础医学   802篇
口腔科学   80篇
临床医学   539篇
内科学   1196篇
皮肤病学   89篇
神经病学   789篇
特种医学   470篇
外科学   693篇
综合类   60篇
一般理论   1篇
预防医学   282篇
眼科学   113篇
药学   326篇
中国医学   3篇
肿瘤学   294篇
  2024年   7篇
  2023年   60篇
  2022年   74篇
  2021年   163篇
  2020年   91篇
  2019年   123篇
  2018年   134篇
  2017年   127篇
  2016年   149篇
  2015年   157篇
  2014年   206篇
  2013年   262篇
  2012年   417篇
  2011年   432篇
  2010年   252篇
  2009年   203篇
  2008年   370篇
  2007年   374篇
  2006年   352篇
  2005年   316篇
  2004年   310篇
  2003年   248篇
  2002年   248篇
  2001年   87篇
  2000年   67篇
  1999年   81篇
  1998年   67篇
  1997年   61篇
  1996年   32篇
  1995年   27篇
  1994年   28篇
  1993年   22篇
  1992年   34篇
  1991年   41篇
  1990年   30篇
  1989年   34篇
  1988年   29篇
  1987年   26篇
  1986年   24篇
  1985年   32篇
  1984年   21篇
  1983年   19篇
  1982年   17篇
  1981年   5篇
  1979年   19篇
  1978年   12篇
  1977年   7篇
  1976年   11篇
  1974年   5篇
  1967年   4篇
排序方式: 共有5954条查询结果,搜索用时 31 毫秒
101.

Objective

We investigated pre-hospital times, clinical characteristics and therapeutic interventions in multisystem trauma patients injured in mountainous areas in comparison to both urban and suburban trauma patient admissions.

Methods

Pre-hospital and in-hospital data collected from trauma patients included in the International Alpine Trauma Register (IATR) hosted in Bolzano, Italy (aged 16–80?yr with an ISS?≥?16), were compared with trauma patient data published from those urban and suburban areas included in the Trauma Register DGU® (TR-DGU) of the German Trauma Society.

Results

A total of 94 patients from the IATR and 11,020 patients from the TR-DGU met the inclusion criteria. Due to longer treatment-free intervals (mean 59.1 vs. 19.7?min), total out-of-hospital time was reportedly longer in individuals injured in mountainous areas, compared to urban/suburban areas (117.4?±?142.9 vs. 68.7?±?28.6?min, p?=?0.002), despite the more frequent helicopter rescue (93% vs. 40%, p?<?0.001). 57% of IATR patients were hypothermic at hospital arrival, mean ISS was higher (38.5?±?15.8 vs. 28.6?±?12.2, p?<?0.001) and patients with a systolic blood pressure (SBP) ≤90?mm?Hg were more frequent (27% vs. 15%, p?=?0.005), yet less patients had received volume therapy (82% vs. 93%, p?=?0.001). However, overall no difference in hospital mortality was observed (11% vs. 17%, p?=?0.159).

Conclusion

Trauma incidents in mountainous areas commonly feature significantly increased out-of-hospital time which is associated with a more severe ISS, higher risk of accidental hypothermia and more frequent hypotension compared to urban/suburban trauma. Nonetheless, the mortality rate of IATR patients is comparable to urban/suburban trauma patients.  相似文献   
102.
In the present work, we describe the preparation of ten amino acid ionic liquids (AAILs) formed from ammonium salts as cations, derivatives of glycerol, and natural amino acids as anions. All of them are viscous oils, colorless or pale yellow, and hygroscopic at room temperature. They have appreciable solubility in many protic and aprotic polar solvents. The AAILs were used as catalysts in a Morita–Baylis–Hillman (MBH) reaction. The ionic liquids derivative from l-proline and l-histidine demonstrated the ability to catalyze the reaction between methyl vinyl ketone and aromatic aldehydes differently substituted in the absence of an additional co-catalyst under organic solvent-free conditions. The AAIL derivatives from l-valine, l-leucine, and l-tyrosine catalyzed the MBH reaction only in the presence of imidazole. The MBH adducts were obtained in moderate to good yields. Although the catalytic site in the ILs was in its enantiomerically pure form, all the MBH adducts were obtained in their racemic form.

In this work, we describe the preparation of ten amino acid ionic liquids (AAILs). The AAILs were used as catalysts in a Morita–Baylis–Hillman (MBH) reaction. The MBH adducts were obtained from moderate to good yields and in their racemic form.  相似文献   
103.
MoS2 is a very attractive material and has been well studied for potential applications in various areas. However, due to the wide variety of factors affecting the molecular and electronic structure of MoS2, several contradictory reports about the adsorptive and photocatalytic properties of such materials have been published. In most of these reports, the effect of the actual phase of the materials on the properties was neglected. Here, different phases of MoS2 nanosheets (1T/2H, 1T/3R and 2H) have been obtained using the hydrothermal method with different Mo : S molar ratios and different autoclave filling ratios. The obtained materials have been thoroughly characterized using Raman, UV-vis, powder XRD, SEM, TEM and XPS measurements in order to accurately identify the existing phases in each material. A comparative study of the photocatalytic organic dye degradation efficiency under white light irradiation has been conducted using methyl orange to correlate the different activity of each material to the respective phase composition. The results indicate a much higher performance of the 1T/2H phase compared to the 2H and 3R phases. Detailed computational studies of the different phases revealed the emergence of mid-gap states upon introducing 1T sites into the 2H lattice. This leads to the improvement of the photocatalytic activity of 1T/2H compared to the other prepared materials.

MoS2 is a very attractive material and has been well studied for potential applications in various areas.  相似文献   
104.
Since 2013, highly virulent porcine epidemic diarrhea virus has caused considerable economic losses in the United States. To determine the relation of US strains to those recently causing disease in Germany, we compared genomes and found that the strain from Germany is closely related to variants in the United States.  相似文献   
105.
106.
Clinical Rheumatology - The prevalence of sarcopenia with osteoporosis results in a higher risk of falling and fractures. It was noted that patients who had completed their planned 5-year denosumab...  相似文献   
107.
108.
We investigated toxicity and efficacy of in vivo T-cell depletion with anti-thymocyte globulin (ATG) as part of an intensified myeloablative conditioning regimen followed by allogeneic stem cell transplantation in patients with advanced multiple myeloma. The conditioning regimen consisted of modified total body irradiation, busulfan and cyclophosphamide (n=15) or in the case of prior dose-limiting radiotherapy of busulfan and cyclophosphamide (n=3). The median age was 44 years (range, 29-53) and the median time from diagnosis to transplant was 12 months (range, 6-144). Grade II-IV acute graft-versus-host disease (GvHD) occurred in six patients (35%). Severe grade III/IV GvHD developed in one patient (6%). Three patients died of therapy-related causes (17%). A complete remission (CR) with negative immunofixation after allogeneic transplantation was seen in eight of the evaluable patients (53%). After a median follow-up of 41 months (range, 8-84), the estimated overall survival at 6 years for all patients is 77% (CI 95%: 58-96%). The estimated progression-free survival at 6 years for all patients is 31% (CI 95%: 2-59%) and 46% (CI 95%: 9-83%) for patients with CR. In vivo T-cell depletion with ATG resulted in a low rate of severe GvHD with low treatment-related mortality, and a substantial number of long-term survivors.  相似文献   
109.
Gugger M  Waser B  Kappeler A  Schonbrunn A  Reubi JC 《Gut》2004,53(10):1431-1436
BACKGROUND AND AIMS: Many neuroendocrine gastrointestinal tumours express receptors for the regulatory peptide somatostatin. Among the five existing somatostatin receptor (sst) subtypes, sst2A is the most frequently expressed in these tumours. However, little information is available about the cellular location of sst2A in corresponding non-neoplastic epithelial tissues. METHODS: We searched for sst2A immunoreactive cells in non-neoplastic gastrointestinal tissues, and evaluated their number and immunohistochemical characteristics with neuroendocrine markers. RESULTS: The gastric antrum showed numerous sst2A cells, situated in the epithelium, corresponding to gastrin containing neuroendocrine cells, while the gastric corpus was largely devoid of sst2A cells, including enterochromaffin-like cells. The remaining foregut, namely the duodenum and proximal jejunum, also contained a large number of sst2A cells, all being neuroendocrine cells and many of them characterised as gastrin cells. Sst2A cells were also detected in the midgut, in low numbers in the epithelium of the distal jejunum and ileum, but not in the appendix vermiformis, the caecum, or the hindgut, despite the large number of neuroendocrine cells present in this area. In addition, sst2A cells were found in the whole gastrointestinal tract in the myenteric and submucosal plexus. CONCLUSIONS: While sst2A receptors on antral gastrin cells presumably mediate somatostatin inhibition of gastrin secretion, the effects of somatostatin on motility and ion transport in the lower gastrointestinal tract may be mediated by sst2A receptors in the neural plexus. These data provide a molecular basis for the physiological actions of somatostatin in human gastrointestinal tissue.  相似文献   
110.
Breathing pattern and eye movement density during REM sleep in humans   总被引:3,自引:0,他引:3  
Changes in the density of eye movement during rapid eye movement (REM) sleep are associated with changes in ventilation and ventilatory response in animals. Recent data in patients with chronic obstructive pulmonary disease suggest that periods of frequent eye movements may be associated with hypoxemia during REM sleep. We have therefore investigated the association between eye movements and ventilation and ventilatory pattern in 10 normal men. Expired ventilation was measured using a pneumotachograph attached to a valved face mask with a dead space of 50 ml and incorporating a peripheral CO2 leak detector. Ventilation was reduced (p less than 0.02) in all stages of sleep compared with that during wakefulness, with no difference between the level of ventilation in each sleep stage (awake, 7.18 +/- 0.43 SEM; Stage 2, 6.47 +/- 0.43; Stage 3/4, 6.45 +/- 0.52; REM sleep, 6.55 +/- 0.47 L/min). During REM sleep, eye movements (EMs) were associated with rapid shallow breathing. Dividing REM into 20-s epochs with or without EMs, EMs were associated with a raised breathing frequency (no EMs, 14.4 +/- 0.4 breaths/min; EMs, 15.8 +/- 0.5 breaths/min; p = 0.01), reduced tidal volume (0.49 +/- 0.03 L; 0.41 +/- 0.03 L; p less than 0.01), and reduced minute ventilation (6.87 +/- 0.45 L; 6.27 +/- 0.51 L; p = 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)  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