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   15916篇
  免费   1353篇
  国内免费   39篇
耳鼻咽喉   214篇
儿科学   564篇
妇产科学   421篇
基础医学   2028篇
口腔科学   176篇
临床医学   1851篇
内科学   2877篇
皮肤病学   280篇
神经病学   1783篇
特种医学   376篇
外科学   1774篇
综合类   129篇
一般理论   21篇
预防医学   2325篇
眼科学   394篇
药学   985篇
  1篇
中国医学   16篇
肿瘤学   1093篇
  2024年   47篇
  2023年   322篇
  2022年   492篇
  2021年   967篇
  2020年   551篇
  2019年   822篇
  2018年   903篇
  2017年   603篇
  2016年   613篇
  2015年   619篇
  2014年   753篇
  2013年   933篇
  2012年   1369篇
  2011年   1314篇
  2010年   649篇
  2009年   554篇
  2008年   881篇
  2007年   801篇
  2006年   631篇
  2005年   592篇
  2004年   508篇
  2003年   415篇
  2002年   327篇
  2001年   122篇
  2000年   104篇
  1999年   100篇
  1998年   74篇
  1997年   58篇
  1996年   45篇
  1995年   56篇
  1994年   36篇
  1993年   37篇
  1992年   70篇
  1991年   76篇
  1990年   64篇
  1989年   75篇
  1988年   52篇
  1987年   42篇
  1986年   55篇
  1985年   53篇
  1984年   45篇
  1983年   49篇
  1982年   41篇
  1980年   28篇
  1979年   36篇
  1978年   32篇
  1976年   21篇
  1975年   28篇
  1973年   27篇
  1969年   21篇
排序方式: 共有10000条查询结果,搜索用时 12 毫秒
51.

The relationship between work rate () and time to exhaustion (t) during intense exercise is commonly described by either a hyperbolic function (NLin), t=W /(? cp), or by its linear equivalent (LinW) W lim =W + cp(t). The parameter <INF cp (critical power) has been described as an inherent characteristic of the aerobic energy system, while W?′ has been shown to be a ralid estimate of anaerobic work capacity. Recent studies have demonstrated that oral supplementation of creatine monohydrate (CrH2O) increases total muscle creatine stores, and have linked these increases to improved performances in intense intermittent exercise. This study was conducted to determine the effect of CrH2O supplementation on estimates of W?′ and <INF cp derived from the NLin and LinW equations, and to determine the effect of CrH2O on t in exhaustive constant power exercise of different intensities. Fifteen active but untrained university students completed three phases of testing on a cycle ergometer: (1) familiarization, three learning trials, (2) baseline determination of W?′ and <INF cp, four bouts performed at a selected to elicit fatigue in 90–600?s, and (3) experimental determination of W?′ and cp, four bouts performed at the same as baseline, but performed after 5 days of ingesting either a placebo (4?×?6?g of glucose/day) or CrH2O (4?×?5?g of CrH2O and 1?g glucose/day). Testing was administered in a double-blind manner. Analyses of covariance revealed a significant effect for CrH2O on both estimates of W?′ (NLin, P=0.04; LinW, P<0.01), but not on estimates of cp (NLin, P=0.37; LinW; P=0.30). Within groups, t was significantly different for only CrH2O at the two highest s (P=0.04). It is concluded that oral ingestion of CrH2O increases estimates of W?′ due to an improved t at the shorter, more intense exercise bouts.

  相似文献   
52.
K L Banks  T C McGuire 《Immunology》1975,28(3):581-588
Surface receptors on peripheral blood neutrophils and monocytes from normal and immunodeficient horses have been studied. Sheep erythrocytes (SRBC) coated with IgG, IgM, and complement but not IgG(T), readily bound to normal equine monocytes and neutrophils. More than 4000 molecules of IgG were required to sensitize each SRBC for adherence to monocytes, and more than 12,000 molecules were required for adherence to neutrophils. Young horses with a severe combined immunodeficiency had an almost total absence of lymphocytes, but normal numbers of monocytes and neutrophils. The number of receptors for immunoglobulin, complement, and phytolectin on monocytes and neutrophils from immunodeficient animals were similar to those on the cells of normal horses. Although the precursor cells of lymphocytes of horses with combined immunodeficiency appear to be defective, no defect in the other cellular products of the bone marrow were apparent.  相似文献   
53.
PROBLEM: Previously we reported on the generation of experimental anti-phospholipid syndrome (APS) in mice. These models were employed to evaluate the efficacy of various novel therapeutic modalities including interleukin-3 (IL-3) and low dose aspirin. The efficacy of the latter was found to be interrelated. Low dose aspirin is capable of inhibiting the activity of the enzyme cyclooxygenase which is responsible for the metabolism of arachidonic acid towards the production of prostaglandins. This shifts the metabolism of arachidonic acid to the other pathway and leads to an overproduction of leukotrienes. The leukotrienes act as stimulators of IL-3 production, a positive cytokine in pregnancy which enhances placental and fetal development. In the current study we evaluated the IL-3 levels in pregnant women with APS and expanded our knowledge on the interrelationships between aspirin, arachidonic acid metabolites and IL-3 in the human system. METHODS: IL-3 levels were recorded in the serum of pregnant women with APS and compared to a control pregnant group. In addition peripheral blood mononuclear cells from healthy subjects were incubated with different concentrations of aspirin or with arachidonic acid metabolites (Leukotriene B4, C4 or PGE2), and IL-3 production in the culture fluids was evaluated. RESULTS: Serum level of IL-3 in pregnant patients with primary APS, APS secondary to SLE and SLE was lower in comparison to the control group. The in vitro studies revealed that only low dose aspirin (10 mg/μl) stimulated IL-3 production while higher doses of the drug failed to induce the cytokine generation. Leukotriene B4 and C4 were stimulatory whereas PGE2 acted as inhibitor of IL-3 production. CONCLUSIONS: The serum level of IL-3 is decreased to pregnant women with primary or secondary APS. Low dose aspirin is capable of stimulating EL-3 production in vitro most probably through an elevation of leukotriene production, which may explain its beneficial activity in preventing the manifestations of APS.  相似文献   
54.
Twelve patients with primary lymphedema of the lower limb were examined with computed tomography (CT). A characteristic "honeycomb" pattern of the subcutaneous compartment was seen in 10 of these patients. CT scans in nine other patients with swollen leg secondary to chronic venous disease or lipedema did not show this characteristic pattern. CT may be helpful in the differential diagnosis of a swollen leg, thus obviating venography or lymphangiography.  相似文献   
55.
Lipids are molecules involved in metabolism and inflammation. This study investigates the plasma lipidome for markers of severity and nutritional status in critically ill children. Children with multi-organ dysfunction syndrome (MODS) (n = 24) are analyzed at three time-points and cross-referenced to sedation controls (n = 4) for a total of N = 28. Eight of the patients with MODS, needed veno-arterial extracorporeal membrane oxygenation (VA ECMO) support to survive. Blood plasma lipid profiles are quantified by nano-electrospray (nESI), direct infusion high resolution/accurate mass spectrometry (MS), and tandem mass spectrometry (MS/MS), and compared to nutritional profiles and pediatric logistic organ dysfunction (PELOD) scores. Our results show that PELOD scores were not significantly different between MODS and ECMO cases across time-points (p = 0.66). Lipid profiling provides stratification between sedation controls and all MODS patients for total lysophosphatidylserine (lysoPS) (p-value = 0.004), total phosphatidylserine (PS) (p-value = 0.015), and total ether-linked phosphatidylethanolamine (ether-PE) (p-value = 0.03) after adjusting for sex and age. Nutrition intake over time did not correlate with changes in lipid profiles, as measured by caloric and protein intake. Lipid measurement in the intensive care environment shows dynamic changes over an 8-day pediatric intensive care unit (PICU) course, suggesting novel metabolic indicators for defining critically ill children.  相似文献   
56.
Weight loss is a major focus of research and public health efforts. Time-restricted eating (TRE) is shown to be effective for weight loss, but the impact on bone is unclear. Short-term TRE studies show no effect on bone mineral density (BMD), but no study has measured bone turnover markers. This secondary analysis examined the effect of 12 weeks of TRE vs. unrestricted eating on bone turnover and BMD. Overweight and obese adults aged 18–65 y (n = 20) were randomized to TRE (ad libitum 8-h eating window) or non-TRE. Serum N-terminal propeptide of type I collagen (P1NP), cross-linked N-telopeptide of type I collagen (NTX), and parathyroid hormone (PTH) levels were measured and dual-energy X-ray absorptiometry (DXA) scans were taken pre- and post-intervention. In both groups, P1NP decreased significantly (p = 0.04) but trended to a greater decrease in the non-TRE group (p = 0.07). The treatment time interaction for bone mineral content (BMC) was significant (p = 0.02), such that BMC increased in the TRE group and decreased in the non-TRE group. Change in P1NP was inversely correlated with change in weight (p = 0.04) overall, but not within each group. These findings suggest that TRE does not adversely affect bone over a moderate timeframe. Further research should examine the long-term effects of TRE on bone.  相似文献   
57.
Food homeostatic states (hunger and satiety) influence the cognitive systems regulating impulsive responses, but the direction and specific mechanisms involved in this effect remain elusive. We examined how fasting, and satiety, affect cognitive mechanisms underpinning disinhibition using a novel framework and a gamified test-battery. Thirty-four participants completed the test-battery measuring three cognitive facets of disinhibition: attentional control, information gathering and monitoring of feedback, across two experimental sessions: one after overnight fasting and another after a standardised meal. Homeostatic state was assessed using subjective self-reports and biological markers (i.e., blood-derived liver-expressed antimicrobial protein 2 (LEAP-2), insulin and leptin). We found that participants who experienced greater subjective hunger during the satiety session were more impulsive in the information gathering task; results were not confounded by changes in mood or anxiety. Homeostatic state did not significantly influence disinhibition mechanisms linked to attentional control or feedback monitoring. However, we found a significant interaction between homeostatic state and LEAP-2 on attentional control, with higher LEAP-2 associated with faster reaction times in the fasted condition only. Our findings indicate lingering hunger after eating increases impulsive behaviour via reduced information gathering. These findings identify a novel mechanism that may underpin the tendency to overeat and/or engage in broader impulsive behaviours.  相似文献   
58.
Maternal and Child Health Journal - Many studies correlate lower health literacy with poorer health outcomes and inferior provider-patient communication. Little is known about how impaired health...  相似文献   
59.
Maternal and Child Health Journal - The purpose of this study was to explore socio-ecological influences affecting the daily lives of urban, pregnant Puerto Rican women and factors negatively...  相似文献   
60.
Maternal and Child Health Journal - To investigate whether adverse childhood experiences are associated with miscarriage. The Gulf Resilience on Women’s Health Consortium recruited from...  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