全文获取类型
收费全文 | 36850篇 |
免费 | 3811篇 |
国内免费 | 69篇 |
专业分类
耳鼻咽喉 | 477篇 |
儿科学 | 1023篇 |
妇产科学 | 747篇 |
基础医学 | 5265篇 |
口腔科学 | 1402篇 |
临床医学 | 4191篇 |
内科学 | 7345篇 |
皮肤病学 | 428篇 |
神经病学 | 2940篇 |
特种医学 | 1456篇 |
外国民族医学 | 2篇 |
外科学 | 4817篇 |
综合类 | 952篇 |
一般理论 | 30篇 |
预防医学 | 3868篇 |
眼科学 | 1008篇 |
药学 | 2808篇 |
1篇 | |
中国医学 | 27篇 |
肿瘤学 | 1943篇 |
出版年
2021年 | 523篇 |
2020年 | 328篇 |
2019年 | 554篇 |
2018年 | 604篇 |
2017年 | 447篇 |
2016年 | 476篇 |
2015年 | 578篇 |
2014年 | 815篇 |
2013年 | 1206篇 |
2012年 | 1664篇 |
2011年 | 1759篇 |
2010年 | 950篇 |
2009年 | 932篇 |
2008年 | 1556篇 |
2007年 | 1649篇 |
2006年 | 1517篇 |
2005年 | 1582篇 |
2004年 | 1441篇 |
2003年 | 1383篇 |
2002年 | 1353篇 |
2001年 | 1100篇 |
2000年 | 1157篇 |
1999年 | 1076篇 |
1998年 | 416篇 |
1997年 | 352篇 |
1996年 | 393篇 |
1995年 | 363篇 |
1994年 | 348篇 |
1993年 | 356篇 |
1992年 | 872篇 |
1991年 | 852篇 |
1990年 | 873篇 |
1989年 | 792篇 |
1988年 | 755篇 |
1987年 | 773篇 |
1986年 | 712篇 |
1985年 | 717篇 |
1984年 | 532篇 |
1983年 | 494篇 |
1982年 | 313篇 |
1981年 | 333篇 |
1980年 | 301篇 |
1979年 | 477篇 |
1978年 | 382篇 |
1977年 | 310篇 |
1976年 | 302篇 |
1974年 | 375篇 |
1973年 | 362篇 |
1972年 | 299篇 |
1971年 | 312篇 |
排序方式: 共有10000条查询结果,搜索用时 21 毫秒
81.
82.
Using a simplified procedure, we have extracted DNA from unstained paraffin sections of needle biopsies of kidney and liver transplants and identified the presence of CMV using the polymerase chain reaction. This method utilizes oligonucleotide primers for two genes shown to be specific for cytomegalovirus (CMV) as well as an internal control gene (hemoglobin) in a single reaction. Utilizing nested PCR amplification with agarose gel electrophoresis, CMV can be detected without radioisotopes to a level of sensitivity equivalent to one one-hundredth of a cytomegalic virocyte per cm2 of a 3-microM paraffin section. This method is applicable to situations where only scarce paraffin-embedded tissue is available. 相似文献
83.
This study was designed to evaluate the routine use of a gum elastic bougie for tracheal intubation. The median time to intubation with the gum elastic bougie while simulating an 'epiglottis only' view was only 10 s longer than the time taken during conventional intubation with an optimum view. Three of the patients required a gum elastic bougie-assisted intubation after attempts at conventional visual intubation had failed. There was no significant difference in the incidence of postoperative sore throat and hoarseness between the two groups. We recommend that anaesthetists should use the gum elastic bougie whenever a good view of the glottis is not immediately obtained. 相似文献
84.
Anti-rat thymocyte antibody-induced injury of glomerular mesangial cells is characterized initially by lysis (1 h) and is followed by proliferation (beginning at 3 to 4 days), with resolution that can include a focal increase in mesangial matrix (by 28 days). Chronic administration (every 12 h) of heparin (anticoagulant or nonanticoagulant) resulted in a decrease in antibody-induced mesangial cell proliferation, which, in turn, was associated with a decrease in the size and number of areas of focal mesangial matrix increase. The effect could not be attributed to the effect of heparin on complement, to alterations in the small numbers of la-positive cells that characterize the lesion, or to binding of antibody to glomeruli. The beneficial effects of heparin in reducing mesangial cell proliferation, with a subsequent reduction in matrix increase, suggest that mesangial cell responses are a major element in the development of at least some forms of glomerulosclerosis. The possible mechanisms by which these effects of heparin may be achieved are discussed. 相似文献
85.
Aspiration cytologic, ultrastructural, and DNA cytometric findings of solid and papillary tumor of the pancreas. 总被引:1,自引:0,他引:1
Solid and papillary epithelial neoplasm of the pancreas (SPENP) is a rare lesion characteristically occurring in young women. By contrast with pancreatic ductal adenocarcinomas, SPENP is a slow-growing tumor that rarely metastasizes or is fatal. The current report describes light and electron microscopic and histochemical findings with DNA flow cytometric analyses of two cases of SPENP. The first patient was a 24-year-old woman; the second, a 72-year-old man. Although SPENP is rare in older men, both patients had characteristic radiographic and light microscopic features of SPENP. Ultrastructural evidence of acinar differentiation was seen in the first patient; the second patient had focal neuroendocrine differentiation. Flow cytometric analysis of the first tumor demonstrated diploid-range DNA content with a 5.8% S-phase fraction (SPF). The DNA cytometric analysis of a biopsy specimen from the second tumor revealed diploid-range DNA content with a 6.1% SPF, although subsequent sampling of the resected tumor showed an aneuploid population with a DNA index of 1.8 and SPF of 2.1%. 相似文献
86.
Cardiomyopathy: a late complication of hemolytic uremic syndrome 总被引:2,自引:0,他引:2
Amanda M. Walker Lee N. Benson Greg J. Wilson Gerald S. Arbus 《Pediatric nephrology (Berlin, Germany)》1997,11(2):221-222
This report describes a child who presented with classic hemolytic uremic syndrome (HUS) and 4 months later developed a life-threatening
but reversible cardiomyopathy with global cardiac dysfunction and a left ventricular ejection fraction of 14%. There was no
evidence of electrolyte abnormalities, anemia, hypertension, severe fluid overload, or viral infection. Endomyocardial biopsies
were consistent with a dilated cardiomyopathy. This paper highlights the importance of considering the diagnosis of associated
cardiomyopathy when presenting with late-onset edema following HUS.
Received February 12, 1996; received in revised form and accepted August 22, 1996 相似文献
87.
Maria-Carmen Wilson Jack . Greenberg Steven Barrer C. P. Shah 《Journal of neuroimaging》1992,2(3):156-158
Spinal cord infarction or ischemia predominates in the thoracic region, less so in the cervical and lumbar regions. Different etiological factors have been implicated in anterior spinal artery syndrome. Magnetic resonance imaging (MRI) allows in vivo imaging of spinal cord disease, including infarction. A 31-yearold, previously healthy man had an acute onset of interscapular pain, followed by rapid development of quadriparesis associated with paresthesias and mild bladder dysfunction. Initial MRI of the cervicothoracic region demonstrated normal findings. A repeat study obtained 6 days later showed marked increase in the cervical cord size, especially at the C6-7 level. On the T2-weighted sagittal series and after gadolinium injection, increased signal in the anterior portions of the cord extending from C-4 to the T2-3 interspace was noted. This was most prominent at the C-6 and C-7 levels. The coronal views revealed abnormal high signal in the region of the anterior horns of the gray matter, a finding that is recognized as an “owl's eyes” pattern. Because the MRI changes of cerebral infarction may succeed a clinical event by hours or days, accurate diagnosis may require delayed or repeated studies. This report suggests that the diagnosis of spinal cord disease requires a similar evaluation. 相似文献
88.
Subcutaneous melatonin implants were administered to castrated hand-reared male red deer (Cervus elaphus) during a 63 d period in spring, after which effects on voluntary feed intake (VFI), rumen pool size, rumen capacity (i.e. volume) and heart rate were measured on four occasions, evenly spread over a 12-month period, with the deer individually fed indoors on a diet of lucerne (Medicago sativa) chaff. Blood samples for hormone determinations were taken at intervals throughout the study. Day-time plasma melatonin concentration was approximately 5 pg/ml in control animals, whereas during melatonin administration it increased to 60-150 pg/ml and declined to 30 pg/ml by 142 d after the last implantation. Melatonin administration markedly depressed plasma prolactin concentration during the period of implantation, but thereafter plasma prolactin concentration rose in the treated animals during autumn and winter, whilst it declined in control animals over this period. VFI, rumen pool size and heart rate in control animals attained highest values in summer and lowest values in winter, showing a pronounced seasonal cycle. Melatonin administration depressed all these values in late spring and summer and increased all the values in autumn and winter, relative to control animals, and appeared to move the cycles by approximately 6 months. Melatonin-treated animals showed maximum values for all these measurements during winter. The castrated male deer showed little seasonal change in live weight, which was not affected by melatonin administration. The findings support the view that melatonin probably mediates the effect of daylength on digestive function in red deer. Rumen capacity remained relatively constant throughout the year, but rumen pool size as a proportion of rumen capacity increased with increasing VFI. 相似文献
89.
Survival from colorectal cancer has not improved over the last four decades despite advances in surgery and anaesthesia. The answer to the question whether adjuvant chemotherapy and radiotherapy will improve survival from the disease can only come from randomised, controlled trails. In the future, immunotherapy and gene therapy may be of benefit but these are still many years from the clinical arena. We believe that current evidence suggests that patients with Dukes B and C colorectal cancer should be entered into trials of adjuvant therapy. This evidence is reviewed below among with estimates of the impact that adjuvant therapy would have on the outcome from this disease in Northern Ireland. 相似文献
90.
Ectoparasites infesting a population of urban gray squirrels (Sciurus carolinensis Gmelin) in northern Florida were collected monthly during 1974. Eleven species were identified: one flea (Orchopeas howardi (Baker], three suckling lice (Enderleinellus longiceps Kellogg & Ferris, Hoplopleura sciuricola Ferris, and Neohaematopinus sciuri Jancke), one tick (Dermacentor variabilis Say), two mesostigmatid (gamasid) mites (Androlaelaps casalis (Berlese) and A. fahrenholzi (Berlese], and four chiggers (Eutrombicula alfreddugesi (Oudemans), E. splendens (Ewing), Leptotrombidium peromysci Vercammen-Grandjean & Langston, and Parasecia gurneyi (Ewing]. The flea and three suckling lice represent core species of ectoparasites for the gray squirrel; the remainder are probably satellite species. Only E. longiceps varied significantly in prevalence or intensity of infestation among host age groups; subadult squirrels had higher intensities than adults. Peak prevalence of O. howardi occurred in January and attained maximum intensity in March, whereas both prevalance and intensity were minimum in August. Prevalence of H. sciuricola was maximum in November and remained at similar levels through June. It then declined significantly to its minimum in September-October. Intensity of infestation, however, was greatest in August, September, and January. Maximum prevalence of N. sciuri occurred from January to March and was minimum in September; intensity of infestation reached maxima in January, June, and August. 相似文献