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   1278999篇
  免费   92862篇
  国内免费   2001篇
耳鼻咽喉   18204篇
儿科学   42277篇
妇产科学   37831篇
基础医学   187383篇
口腔科学   35472篇
临床医学   108276篇
内科学   252015篇
皮肤病学   26581篇
神经病学   99388篇
特种医学   50015篇
外国民族医学   366篇
外科学   197964篇
综合类   26526篇
现状与发展   1篇
一般理论   300篇
预防医学   92649篇
眼科学   29147篇
药学   98020篇
  1篇
中国医学   2529篇
肿瘤学   68917篇
  2018年   11859篇
  2015年   11656篇
  2014年   16035篇
  2013年   24410篇
  2012年   33643篇
  2011年   36047篇
  2010年   21256篇
  2009年   20057篇
  2008年   35059篇
  2007年   38043篇
  2006年   38603篇
  2005年   37905篇
  2004年   36490篇
  2003年   35485篇
  2002年   35014篇
  2001年   58185篇
  2000年   59693篇
  1999年   50779篇
  1998年   14261篇
  1997年   12827篇
  1996年   13099篇
  1995年   12364篇
  1994年   11784篇
  1993年   10873篇
  1992年   41050篇
  1991年   40421篇
  1990年   39932篇
  1989年   38766篇
  1988年   36159篇
  1987年   35383篇
  1986年   33764篇
  1985年   32173篇
  1984年   23962篇
  1983年   20836篇
  1982年   12397篇
  1981年   10944篇
  1980年   10214篇
  1979年   22663篇
  1978年   15893篇
  1977年   13741篇
  1976年   12985篇
  1975年   14217篇
  1974年   16698篇
  1973年   16094篇
  1972年   15334篇
  1971年   14242篇
  1970年   13229篇
  1969年   12747篇
  1968年   11990篇
  1967年   10498篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
992.
The component of a composite prosthesis, which makes contact with the visceral peritoneum, can be reabsorbable or non-reabsorbable, and laminar or reticular. This study was designed to determine whether the composition of this second, barrier component could improve its behavior at this interface. Abdominal wall defects in rabbits were repaired using a polypropylene prosthesis (PP), or the composites Sepramesh (PP+h) or Vicryl (PP+v). Fourteen days after surgery, the implants were evaluated by light and scanning electron microscopy, and immunohistochemistry. Prosthetic areas occupied by adhesions (PP: 71.08±5.09, PP+h: 18.55±4.96, P+v: 69.69±16.81%), neoperitoneal thickness (PP: 256.17±21.68, PP+h: 83.11±19.63, PP+v:213.72±35.90 μm) and macrophage counts (PP: 8.73±1.16, PP+h: 27.33±4.13, PP+v: 31.24±3.08%) showed significant differences (P<0.05). The tested biomaterials induced an optimal recipient tissue infiltration. Least adhesion formation was observed on the PP+h implants. This suggests that the second component, although reabsorbable, should be smooth in structure.  相似文献   
993.
Clinical Experience with Light-Emitting Diode (LED) Photomodulation   总被引:1,自引:0,他引:1  
Background. Light-emitting diode (LED) photomodulation is a novel nonthermal technology used to modulate cellular activity with light.
Objective:. We describe our experience over the last 2 years using 590 nm LED photomodulation within a dermatologic surgery environment.
Methods. Practical use of nonthermal light energy and emerging applications in 3,500 treatments delivered to 900 patients is detailed.
Results. LED photomodulation has been used alone for skin rejuvenation in over 300 patients but has been effective in augmentation of results in 600 patients receiving concomitant nonablative thermal and vascular treatments such as intense pulsed light, pulsed dye laser, KTP and infrared lasers, radiofrequency energy, and ablative lasers.
Conclusion:. LED photomodulation reverses signs of photoaging using a new nonthermal mechanism. The anti-inflammatory component of LED in combination with the cell regulatory component helps improve the outcome of other thermal-based rejuvenation treatments.  相似文献   
994.
Renal cell carcinomas may extend into the vena cava and the tumor thrombus occasionally involves the right atrium. The operative approach depends upon precise preoperative and intraoperative staging and thrombus localization. We report a case of renal cell carcinoma with complete inferior vena caval and hepatic vein occlusion with tumor extension into the right atrium. Preoperatively, transesophageal echocardiography provided superior images of the tumor and its extension, and intraoperatively allowed continuous monitoring of cardiac function and the removal of tumor from the atrium and inferior vena cava. Its use obviated the need for more costly and invasive preoperative and intraoperative procedures.  相似文献   
995.
This study attempted to evaluate the efficacy of chronic extra-aortic counterpulsation with a latissimus dorsi neuro vascular flap. Five dogs had a preliminary procedure consisting of the creation of a latissimus dorsi flap and a thoracotomy in which the flap was wrapped around the descending aorta just distal to the left subclavian artery. An epicardial lead was placed on the left ventricle and a nerve stimulating lead placed around the thoraco-dorsal nerve. Three weeks later, both leads were connected to a cardiomyostimulator programmed to function in a counterpulsation mode with a 1:2 assist frequency. Hemodynamic measurements were made at 6 and 8 and 10 and 12 weeks and the dogs were sacrificed. Three dogs had all sets of hemodynamic measurements made. Two of the three dogs demonstrated diastolic augmentation at 6 and 8 and 10 and 12 weeks average 20 to 25 mmHg. The third dog failed to demonstrate any change. All dogs were sacrificed at 12 weeks and specimens were submitted for histologic evaluation. The muscle flap was preserved in all animals. The aorta subjacent to the flap showed, (1) normal intima with no evidence of disruption or thrombus in all animals, (2) in the animals in whom counterpulsation was observed, there appeared to be thinning of the media in the aorta subjacent to the muscle flap, and (3) no evidence of distal emboli. This study demonstrated that chronic counterpulsation can be obtained with a latissimus dorsi flap. The actual hemodynamic benefits are not determined from this study. The medial thinning in the aortic wall may limit the long-term benefit of this procedure.  相似文献   
996.
Porencephaly is usually considered to be a prenatal brain lesion due to a circulatory failure. We report a case of bilateral porencephaly with heterotopia and absence of the septum pellucidum in a newborn. The mother had received several injections of benzol during pregnancy with an intent of inducing abortion. The possibility of a causal relationship between the administration of benzol and the occurrence of the defect is supported by the existence of previously reported cases of cerebral malformations following maternal exposure to organic solvents.  相似文献   
997.
Patients with mood depression have been found to have a higher prevalence of seborrheic dermatitis (SD), possibly related to their tendency to live indoors. The prevalence of outpatients with SD has now been found to be directly related to the number of gloomy days in the area. Since UV light might not be the only reason for the well-known improvement in SD in summer, an explanation possibly related to melatonin is envisaged.  相似文献   
998.
Common migraine and cervicogenic headache have many traits in common, so many that they may be mixed up. Both are unilateral headaches with a female preponderance. However, as for a number of variables, they differ. This first and foremost has to do with factors concerning the neck. In cervicogenic headache, the following symptoms and signs are present: a reduced range of motion in the neck; mechanical precipitation of attack, either by neck movements or by external pressure over the greater occipital nerve of the C2 root; ipsilateral shoulder/arm pain; unilaterality without side-shift. Similar findings are usually not made in common migraine. Typical migraine symptoms, such as nausea, vomiting, photophobia, and phonophobia also occur in cervicogenic headache, but less frequently and to a lesser degree. Operative procedures directed to occipital/nuchal structures may afford decisive differentiation between the two disorders. In our estimation, cervicogenic headache and common migraine are two distinct disorders, with their own clinical patterns, pathogenesis, treatment - and, in all probability, also prognosis.  相似文献   
999.
Using liposomes radiolabelled by the 99mTechnetium-stannous chloride technique we have investigated the effect of surface charge on the stability of the isotope in vitro and in vivo. Dialysis of 99mTc-labelled positive, negative and neutral liposomes, which had been incubated in either saline or normal rat serum showed no significant loss of the isotope from the liposome surface with only 2 per cent of the isotope dialysed. A comparison of gel chromatography with dialysis confirmed that most of the isotope remained attached to the liposome surface, but it did reveal greater loss of the isotope, between 15 and 23 per cent. The liposome clearance rates obtained from 125I-egg phosphatidylcholine (EPC) and 99mTc dual-labelled positive or neutral liposomes were significantly different. The 99mTc marker was cleared five times faster from the positive liposomes and twice as fast from the neutral liposomes as the 125I-EPC integral membrane marker. The 99mTc attached to liposomes with a negative surface charge was stable in vivo and had the same clearance rate from the circulation as the 125I-EPC marker. These results indicate that the commonly used in vitro techniques for assessing liposome radiolabel stability are unsuitable for predicting the stability of the 99mTc in vivo.  相似文献   
1000.
alpha 1- and beta-adrenoceptors were studied ex vivo in the brains of rats receiving repeated daily treatment with the standard antidepressant imipramine or the atypical antidepressant S-adenosyl-L-methionine (SAM), which has minimal effects on monoamine reuptake or turnover. Consistent with past studies, a decrease in the density of beta receptors at three weeks and an increase in the affinity of alpha 1 receptors for the agonist phenylephrine at one week of treatment was observed with imipramine. By comparison, an increase in the density of beta receptors and a decrease in the affinity of alpha 1 receptors for phenylephrine was observed at one week of treatment with SAM. These changes were no longer apparent at three weeks of treatment. The results suggest that treatment with SAM does lead to changes in adrenergic neurotransmission, but that down regulation of beta receptors or increased agonist affinity of alpha 1 receptors may not be necessary for the production of antidepressant effects.  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