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   3546篇
  免费   259篇
  国内免费   16篇
耳鼻咽喉   22篇
儿科学   97篇
妇产科学   132篇
基础医学   341篇
口腔科学   79篇
临床医学   399篇
内科学   822篇
皮肤病学   131篇
神经病学   127篇
特种医学   304篇
外科学   466篇
综合类   106篇
一般理论   2篇
预防医学   309篇
眼科学   34篇
药学   271篇
中国医学   9篇
肿瘤学   170篇
  2021年   37篇
  2020年   20篇
  2019年   37篇
  2018年   41篇
  2017年   31篇
  2016年   41篇
  2015年   50篇
  2014年   89篇
  2013年   154篇
  2012年   132篇
  2011年   141篇
  2010年   85篇
  2009年   121篇
  2008年   138篇
  2007年   163篇
  2006年   161篇
  2005年   148篇
  2004年   119篇
  2003年   93篇
  2002年   114篇
  2001年   92篇
  2000年   108篇
  1999年   79篇
  1998年   98篇
  1997年   81篇
  1996年   92篇
  1995年   68篇
  1994年   70篇
  1993年   64篇
  1992年   55篇
  1991年   65篇
  1990年   94篇
  1989年   96篇
  1988年   90篇
  1987年   76篇
  1986年   77篇
  1985年   55篇
  1984年   45篇
  1983年   48篇
  1982年   28篇
  1981年   44篇
  1980年   32篇
  1979年   32篇
  1978年   28篇
  1977年   32篇
  1976年   31篇
  1975年   21篇
  1973年   19篇
  1972年   18篇
  1971年   18篇
排序方式: 共有3821条查询结果,搜索用时 15 毫秒
991.
The effects of atrial natriuretic factor (ANF) were evaluated in rats with chronic aorto-caval (A-V) fistula. In this experimental model of high-output heart failure, the animals display elevated atrial pressure and systemic vasodilation, but avidly retain sodium. Experiments were performed on Munich-Wistar rats, 8 to 14 days after placement of an infrarenal surgical anastomosis (side-to-side, 0.9 +/- 0.2 mm) and on sham operated controls. Infusion of synthetic ANF (3-28) intravenously (5 micrograms/kg prime; 0.17 microgram/kg.min) resulted in increases in urine flow (V) and fractional sodium excretion (FENa) and decreases in blood pressure (BP) that were significantly attenuated in rats with A-V fistula compared to controls. To control for the lower baseline BP that was present in rats with A-V fistula, a second series of studies was performed in which renal perfusion pressure was reduced in normal rats to 110 mm Hg with a servocontrolled pneumatic cuff. ANF infusion to this group led to significant increases in glomerular filtration rate (GFR), V and FENa that were greater than those seen in rats with A-V fistula (FENa = 2.7 +/- 0.3% vs. 0.48 +/- 0.12%, P less than 0.05). Thus, the moderately reduced BP in rats with A-V fistula did not account for the blunted response to ANF. To investigate whether the renal sensitivity to ANF is altered in this model, an additional series of experiments were performed in which ANF was infused over a range of doses (0.08 to 2.5 micrograms/kg.min) to both groups of rats.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
992.
We used a replication-incompetent, single-cycle, alphavirus replicon vector system to produce virus-like replicon particles (VRP) expressing the extracellular domain of human cytomegalovirus (CMV) glycoprotein B or a pp65/IE1 fusion protein. Efficient production methods were scaled to produce pilot lots and clinical lots of each alphavirus replicon vaccine component. The vaccine induced high-titered antibody responses in mice and rabbits, as measured by ELISA and CMV neutralization assays, and robust T-cell responses in mice, as measured by IFN-gamma ELISPOT assay. A toxicity study in rabbits showed no adverse effects in any toxicology parameter. These studies support clinical testing of this novel CMV alphavirus replicon vaccine in humans.  相似文献   
993.
Temporomandibular pain dysfunction syndrome (TMPDS) comprises a variety of signs and symptoms which may be present in any combination, dependent upon the progress and stage of the disorder. The diagnostic criteria are pain on palpation of the temporomandibular joint (TMJ), muscle tenderness on examination, joint sounds, and limitation or deviation of jaw movement on opening. Headache may also be a symptom. Physiotherapy is commonly used to treat this disorder but there is little published material in the field of clinical trials comparing different methods of physiotherapy. Most reports are anecdotal. This paper reports four different physiotherapy modalities in the management of TMPDS when compared with a placebo group. Short-wave diathermy, megapulse, ultrasound and soft laser were tested. There was no statistically significant different in success rate between any of the four methods but each was significantly better than placebo treatment.  相似文献   
994.
目的:不同的基因病具有不同的临床表现,认识基因病的表现特点,为防治和探究基因病提供参考。方法:基因的表达具有时空性,一些基因具有可诱导性,在精神分裂症的研究中将脑基因分为基础性表达基因和反应性表达基因,对应地将基因病分为3个类型。依据以上结果,结合遗传性疾病的流行病学特点,对基因病的表现特点进行分析。结果:基因病的临床表现特点为:①具有遗传的聚集性特征。②具有一定的发病生理阶段性。③具有较固定的临床和病理表现特点。④可有"基础迁延型"、"基础复发型"和"反应调节型"3种临床表现类型。结论:基因病的临床表现特点是由基因的表达特点所决定的。  相似文献   
995.
目的 按讨大肠癌、胃癌患者血清免疫抑制酸性蛋白(IAP)检则的临床意义。方法 采用试剂盒提供的方法测定大肠癌患者32例、胃癌患者24例和正常对照30例血清(IAP)含量。结果 大肠癌患者血清IAP为(690±108)×103μg/L,胃癌患者血清IAP为(642±112)×103μg/L,与对照组血清IAP值(321±128)×103μg/L比有显著性差异(P<O.01);大肠癌组低期与高期、胃癌组低期与高期之间IAP含量亦存在显著性差异(P<0.05)。大肠癌、胃癌患者血清IAP较对照组明显升高,且随病情进展IAP升高更加明显。结论IAP可作为评估肿瘤患者免疫功能和预后的临床指标。  相似文献   
996.
The impact of ambient aeroallergens on morbidity from childhood asthma is largely unknown. To address this issue, we studied the association between daily emergency department visits for asthma to a children's hospital, and daily concentrations of both pollen grains and fungal spores during a 5-yr period between 1993 and 1997. Air pollution and meteorological data accounted for in the analyses included ozone, nitrogen dioxide, sulfur dioxide, sulfates, temperature, barometric pressure, and relative humidity. The daily number of asthma visits ranged from 0 to 36 per day with an average of 7.5. Fungal spores, but not pollen grains, were associated with visits (p < 0.05). The percentage increase associated with each group, independent of the others, was 1.9% (SE 0.9) for deuteromycetes, 4.1% (1.6) for basidiomycetes, 2.8% (1.0) for ascomycetes, and 8.8% for these spores combined. In summary, fungal spores account for a significant proportion of the asthma exacerbations in children that prompt an emergency department visit.  相似文献   
997.
Schiffer  CA 《Blood》1996,88(10):3675-3685
A number of randomized trials have recently been completed evaluating the effect of hematopoietic growth factors (granulocyte-macrophage colony-stimulating factor or granulocyte colony-stimulating factor) as adjuncts to the treatment of patients with acute myeloid leukemia. Most studies used the growth factors to decrease the duration of neutropenia with the hope of reducing infectious morbidity and mortality. The results of these trials are generally quite consistent. Virtually all trials showed a modest reduction in the duration of severe neutropenia with a variable effect on the incidence of severe infections, antibiotic usage, and the duration of hospitalization. There was no consistent benefit in terms of improvements in complete response rate, complete response duration, or overall survival. However, it is important that there does not appear to be an increase in the incidence of drug-resistant leukemia in trials in which the growth factor was begun after completion of the chemotherapy. Other trials administered growth factors either before or simultaneous with the chemotherapy in an attempt to enhance chemosensitivity and decrease drug resistance. None of these trials, whether conducted as part of initial induction therapy or in relapse, showed improvements in response rate or survival. Lastly, some anecdotal reports have suggested that occasional patients who receive growth factors as the only therapy for overt leukemia can achieve remission, possibly through a differentiating effect of the growth factor. However, there are very few such reports, and growth factor use in this situation is potentially dangerous and should be performed only in the context of a clinical trial. In summary, there appears to be no role at this time for priming of leukemia cells by growth factors to enhance the effect of chemotherapy, and more in vitro studies should be performed before further clinical trials of this approach. It is clear that growth factors administered after induction and possibly consolidation chemotherapy can shorten the duration of neutropenia, without a significant effect on treatment outcome. It is as yet unclear whether the use of growth factors in this fashion is cost effective.  相似文献   
998.
Huss  R; Hoy  CA; Deeg  HJ 《Blood》1995,85(9):2414-2421
Cell-cell interactions and the presence of growth factors such as stem cell factor (SCF; or c-kit ligand) or interleukin-6 (IL-6) are involved in the proliferation and differentiation of the canine marrow-derived stromal cell line DO64. In the presence of SCF, stromal cells are induced to differentiate, but not to proliferate. In contrast, in the presence of IL-6, stromal cells are induced to proliferate rather than to differentiate in culture. Both SCF and IL-6 are produced by the stromal cells themselves and, thus, act as autocrine factors. In addition, DO64 cells also interact physically with each other in culture when grown under optimal culture conditions (70% to 90% cell confluence and in the presence of serum), thereby supporting proliferation and maintaining viability. Under conditions of lower cell density or low serum or growth factor concentrations in culture, DO64 cells tend to aggregate and form clusters. This increase in local cell concentration is associated with preservation of viability, presumably because of the accumulation of autocrine factors. If no signal, neither intercellular nor soluble, is provided, and DO64 cells are not able to reach a critical cell density or to produce sufficient factors in an autocrine fashion, the cells cease to proliferate and eventually die.  相似文献   
999.
The degree of concordance between clinicians' and patients' assessment of the patient's physical and mental functioning was examined in 166 consecutive eligible outpatients with rheumatoid arthritis (RA) using 4-category ordinal scales. The weighted kappa statistic was 0.39 for physical functioning and 0.30 for mental functioning, both indicating a fair degree of concordance. This disagreement differed in magnitude and direction depending on the level of disability present. We conclude that clinicians and their patients with RA often disagree in their assessment of the degree of physical and mental impairment that the patient experiences. These disagreements demonstrate the need for formal assessments of outcome and should be recognized and resolved when managing individual patients.  相似文献   
1000.
Horne  MK d; Stein  CA; LaRocca  RV; Myers  CE 《Blood》1988,71(2):273-279
A complex coagulopathy appeared in three women receiving suramin as treatment for metastatic adrenocortical carcinoma. Although hepatocellular dysfunction accounted for some of the abnormality, a unique feature of the coagulopathy was the presence of an inhibitor of the thrombin clotting time. The potency of this circulating anticoagulant increased markedly during exacerbations of hepatic injury. The anticoagulant was removed from plasma samples from two of the patients by passage over a column of diethylaminoethyl (DEAE)- Sephacel. It eluted from the DEAE at salt concentrations that removed "high-charge" glycosaminoglycans. Elimination of the purified anticoagulant activity in vitro required a combination of heparitinase and chondroitinase ABC, suggesting that the activity was mediated by both heparan sulfate and dermatan sulfate. Suramin is hypothesized to inhibit enzymes that normally degrade glycosaminoglycans, resulting in accumulation of these substances, which are released from the liver into the circulation during periods of hepatic injury.  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