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   3305篇
  免费   109篇
  国内免费   13篇
耳鼻咽喉   41篇
儿科学   40篇
妇产科学   41篇
基础医学   512篇
口腔科学   24篇
临床医学   417篇
内科学   693篇
皮肤病学   29篇
神经病学   289篇
特种医学   131篇
外科学   477篇
综合类   4篇
一般理论   1篇
预防医学   184篇
眼科学   32篇
药学   308篇
中国医学   6篇
肿瘤学   198篇
  2024年   2篇
  2023年   10篇
  2022年   29篇
  2021年   94篇
  2020年   24篇
  2019年   52篇
  2018年   74篇
  2017年   53篇
  2016年   43篇
  2015年   72篇
  2014年   75篇
  2013年   118篇
  2012年   255篇
  2011年   258篇
  2010年   129篇
  2009年   128篇
  2008年   246篇
  2007年   251篇
  2006年   272篇
  2005年   253篇
  2004年   236篇
  2003年   200篇
  2002年   211篇
  2001年   23篇
  2000年   15篇
  1999年   14篇
  1998年   44篇
  1997年   40篇
  1996年   24篇
  1995年   34篇
  1994年   20篇
  1993年   24篇
  1992年   18篇
  1991年   3篇
  1990年   9篇
  1989年   10篇
  1988年   15篇
  1987年   4篇
  1986年   7篇
  1985年   4篇
  1984年   6篇
  1983年   6篇
  1982年   4篇
  1981年   4篇
  1980年   3篇
  1979年   1篇
  1978年   1篇
  1977年   6篇
  1974年   2篇
  1966年   1篇
排序方式: 共有3427条查询结果,搜索用时 15 毫秒
31.

Purpose

The soluble receptor for advanced glycation end-products (sRAGE) is a marker of lung epithelial injury and alveolar fluid clearance (AFC), with promising values for assessing prognosis and lung injury severity in acute respiratory distress syndrome (ARDS). Because AFC is impaired in most patients with ARDS and is associated with higher mortality, we hypothesized that baseline plasma sRAGE would predict mortality, independently of two key mediators of ventilator-induced lung injury.

Methods

We conducted a meta-analysis of individual data from 746 patients enrolled in eight prospective randomized and observational studies in which plasma sRAGE was measured in ARDS articles published through March 2016. The primary outcome was 90-day mortality. Using multivariate and mediation analyses, we tested the association between baseline plasma sRAGE and mortality, independently of driving pressure and tidal volume.

Results

Higher baseline plasma sRAGE [odds ratio (OR) for each one-log increment, 1.18; 95% confidence interval (CI) 1.01–1.38; P?=?0.04], driving pressure (OR for each one-point increment, 1.04; 95% CI 1.02–1.07; P?=?0.002), and tidal volume (OR for each one-log increment, 1.98; 95% CI 1.07–3.64; P?=?0.03) were independently associated with higher 90-day mortality in multivariate analysis. Baseline plasma sRAGE mediated a small fraction of the effect of higher ΔP on mortality but not that of higher VT.

Conclusions

Higher baseline plasma sRAGE was associated with higher 90-day mortality in patients with ARDS, independently of driving pressure and tidal volume, thus reinforcing the likely contribution of alveolar epithelial injury as an important prognostic factor in ARDS. Registration: PROSPERO (ID: CRD42018100241).
  相似文献   
32.
We report herein PdxCoy nanoalloys confined in mesoporous carbons (Pdx–Coy@MC) prepared by an eco-friendly one-pot approach consisting in the co-assembly of readily available and non-toxic carbon precursors (phloroglucinol, glyoxal) with a porogen template (pluronic F-127) and metallic salts (H2PdCl4 and Co(NO3)2·6H2O) followed by thermal annealing. Three PdxCoy@MC materials with different alloy compositions were prepared (C1: x/y = 90/10; C2: x/y = 75/25; C3 and C4: x/y = 50/50). The nanoalloys were uniformly distributed in the carbon framework and the particle sizes depended on the alloy composition. These composites were then used for Suzuki–Miyaura reactions using either H2O or a 1 : 1 H2O/EtOH mixture as solvent. The Pd50Co50@MC catalyst C3 proved to be the most efficient catalyst (in terms of efficiency and magnetic recovery) affording the coupling products in good to excellent yields. After reaction, C3 was recovered quantitatively by simple magnetic separation and reused up to six times without loss of efficiency. The amount of palladium lost in the reaction mixture after magnetic separation was very low (ca. 0.1 % wt of the amount initially used).

(Pdx–Coy)@MC were prepared in one-pot via an eco-friendly route and used many times for Suzuki reactions in H2O or H2O/EtOH mixture.  相似文献   
33.
Ischemic mitral regurgitation (MR) is a valvular complication frequently seen in patients with coronary artery disease and is associated with increased mortality and morbidity. Ischemic mitral regurgitation has a complex, heterogeneous, and still incompletely understood pathophysiology involving both the mitral valve and the left ventricle. The occurrence of valve regurgitation in patients with ischemic cardiomyopathy in return accelerates left ventricular remodelling and dysfunction, ultimately leading to irreversible heart failure. Diagnostic evaluation of ischemic MR is unique and different from the other causes of MR. The severity thresholds associated with outcomes are different from primary MR, and specific imaging characteristics are potentially useful to guide therapy. The use of imaging modalities such as 3-dimensional echocardiography and cardiac magnetic resonance imaging can refine the diagnostic evaluation and help in choosing the correct management. Although multiple treatments are available to improve ischemic MR, each therapeutic option is associated with limitations and incomplete success. Therapy has therefore to be individualised for each patient. Current options include optimal medical therapy, cardiac resynchronisation therapy, percutaneous or surgical revascularisation, surgical mitral repair or replacement, and new percutaneous interventions. This review aims to discuss the latest insights regarding the pathophysiology, diagnosis, and treatment of ischemic MR.  相似文献   
34.
OBJECTIVE: Surgery is the treatment of reference for early-stage esophageal cancer, but 5-year survival is only 20% to 25%. After complete resection (R0), survival is significantly longer than after incomplete resection, with microscopic (R1) or macroscopic (R2) penetration. The purpose of this work was to identify retrospectively the factors predictive of complete resection of operable esophageal cancers.PATIENTS AND METHODS: Between January 1982 and March 2001, 746 patients with esophageal cancer underwent curative surgery. R0 resection was performed in 585 patients (78.4%), R1 in 61 (8.2%) and R2 in 100 (13.4%). Univariate and multivariate analysis included 28 preoperative, clinical, tumor and therapeutic parameters.RESULTS: Multivariate analysis showed that factors predictive of complete resection R0 were: absence of any modification of the esophageal axis on the barium swallow (P=0.054), a partial or complete response to preoperative radio-chemotherapy (P=0.042), tumor height<10 cm (P=0.1) and tumor diameter<30 mm (P=0.01). Three groups of patients were identified from the 2 most significant variables. Group 1: no deviation of the axis on the barium swallow (n=501). Group 2: deviation of the axis on the barium swallow and partial or complete response to radiochemotherapy (n=91). Group 3: deviation of the axis on the barium swallow and no response to radiochemotherapy or no preoperative treatment (n=126). For the three groups, rate of R0 resection was 82.6%, 80.1% and 61.1% and 5-year actuarial survival 36%, 27% and 14%, respectively. These rates were significantly different between groups (P<10(- 4)) and two by two (P<0.04).CONCLUSION: Complete resection of esophageal cancer is predictable. After validation with an independent population the findings presented here could be used to establish stratification criteria for future therapeutic trials.  相似文献   
35.
The adhesion of haematopoietic progenitor cells (HPC) to the bone marrow microenvironment is a process regulated by cytokines. In this study, we have shown that flt3-ligand (FL), a growth factor that controls early haematopoiesis, regulated the function and expression of the beta-1 integrins, very late antigen (VLA)-4 and VLA-5 on HPC. The modulation of the adhesiveness of HPC by FL was studied by adhesion assays on umbilical vein endothelial cells (HUVEC). Stimulation by FL induced two peaks of increased adhesiveness of HPC. The first peak was at around 30 min and was mechanistically related to an activation of the beta-1 integrins, mainly VLA-4 and VLA-5. The second peak was at around 12 h and was related to increased expression of VLA-4 and VLA-5. The control of HPC adhesiveness by FL is a previously unreported property of FL that may be important for the homing and the retention of flt3-expressing HPC within the bone marrow microenvironment.  相似文献   
36.
We report on hypophysitis associated with a prominent lymphoid infiltration of salivary and lachrymal glands in a 35-year-old woman with a dramatic response to steroids. Four years later, overt Graves' disease developed. To our knowledge, pseudotumoral lymphocytic infiltration of both lachrymal and salivary glands has never been described in association with hypophysitis. Benign lymphocytic hypophysitis may belong to a spectrum that extends from low-grade lymphoid proliferation to autoimmune disease. Such a process may follow a regional tissue distribution including pituitary, thyroid, lachrymal and salivary glands.  相似文献   
37.
38.
Levels of educational and occupational attainment, as components of cognitive reserve, may modify the relationship between the pathological hallmarks and cognition in Alzheimer's disease (AD). We examined whether exposure of a Tg2576 transgenic mouse model of AD to environmental enrichment (EE) at a specific period during the amyloidogenic process favored the establishment of a cognitive reserve. We found that exposure to EE during early adulthood of Tg2576 mice—before amyloidogenesis has started—reduced the severity of AD-related cognitive deficits more efficiently than exposure later in life, when the pathology is already present. Interestingly, early-life exposure to EE, while slightly reducing forebrain surface covered by amyloid plaques, did not significantly impact aberrant inhibitory remodeling in the hippocampus of Tg2576 mice. Thus, transient early-life exposure to EE exerts long-lasting protection against cognitive impairment during AD pathology. In addition, these data define the existence of a specific life time frame during which stimulatory activity most efficiently builds a cognitive reserve, limiting AD progression and favoring successful aging.  相似文献   
39.
40.
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