全文获取类型
收费全文 | 2957篇 |
免费 | 260篇 |
国内免费 | 13篇 |
专业分类
耳鼻咽喉 | 27篇 |
儿科学 | 140篇 |
妇产科学 | 40篇 |
基础医学 | 411篇 |
口腔科学 | 110篇 |
临床医学 | 226篇 |
内科学 | 665篇 |
皮肤病学 | 43篇 |
神经病学 | 342篇 |
特种医学 | 206篇 |
外科学 | 386篇 |
综合类 | 91篇 |
一般理论 | 1篇 |
预防医学 | 187篇 |
眼科学 | 53篇 |
药学 | 129篇 |
中国医学 | 1篇 |
肿瘤学 | 172篇 |
出版年
2022年 | 20篇 |
2021年 | 43篇 |
2020年 | 36篇 |
2019年 | 40篇 |
2018年 | 71篇 |
2017年 | 33篇 |
2016年 | 52篇 |
2015年 | 56篇 |
2014年 | 76篇 |
2013年 | 111篇 |
2012年 | 134篇 |
2011年 | 125篇 |
2010年 | 116篇 |
2009年 | 91篇 |
2008年 | 118篇 |
2007年 | 132篇 |
2006年 | 125篇 |
2005年 | 112篇 |
2004年 | 115篇 |
2003年 | 104篇 |
2002年 | 103篇 |
2001年 | 66篇 |
2000年 | 75篇 |
1999年 | 73篇 |
1998年 | 87篇 |
1997年 | 62篇 |
1996年 | 61篇 |
1995年 | 55篇 |
1994年 | 42篇 |
1993年 | 46篇 |
1992年 | 46篇 |
1991年 | 54篇 |
1990年 | 46篇 |
1989年 | 51篇 |
1988年 | 57篇 |
1987年 | 48篇 |
1986年 | 51篇 |
1985年 | 72篇 |
1984年 | 44篇 |
1983年 | 27篇 |
1982年 | 26篇 |
1981年 | 25篇 |
1980年 | 19篇 |
1979年 | 30篇 |
1977年 | 25篇 |
1976年 | 29篇 |
1975年 | 17篇 |
1974年 | 16篇 |
1973年 | 22篇 |
1972年 | 16篇 |
排序方式: 共有3230条查询结果,搜索用时 231 毫秒
51.
The deltaccr5 mutation conferring protection against HIV-1 in Caucasian populations has a single and recent origin in Northeastern Europe 总被引:6,自引:0,他引:6
Libert F; Cochaux P; Beckman G; Samson M; Aksenova M; Cao A; Czeizel A; Claustres M; de la Rua C; Ferrari M; Ferrec C; Glover G; Grinde B; Guran S; Kucinskas V; Lavinha J; Mercier B; Ogur G; Peltonen L; Rosatelli C; Schwartz M; Spitsyn V; Timar L; Beckman L; Vassart G 《Human molecular genetics》1998,7(3):399-406
The chemokine receptor CCR5 is encoded by the CMKBR5 gene located on the
p21.3 region of human chromosome 3, and constitutes the major co- receptor
for the macrophage-tropic strains of HIV-1. A mutant allele of the CCR5
gene, Delta ccr5 , was shown to provide to homozygotes with a strong
resistance against infection by HIV. The frequency of the Delta ccr5 allele
was investigated in 18 European populations. A North to South gradient was
found, with the highest allele frequencies in Finnish and Mordvinian
populations (16%), and the lowest in Sardinia (4%). Highly polymorphic
microsatellites (IRI3.1, D3S4579 and IRI3.2, D3S4580 ) located respectively
11 kb upstream and 68 kb downstream of the CCR5 gene deletion were used to
determine the haplotype of the chromosomes carrying the Delta ccr5 variant.
A strong linkage disequilibrium was found between Delta ccr5 and specific
alleles of the IRI3.1 and IRI3.2 microsatellites: >95% of the Delta ccr5
chromosomes carried the IRI3.1-0 allele, while 88% carried the IRI3.2-0
allele. These alleles were found respectively in only 2 or 1.5% of the
chromosomes carrying a wild-type CCR5 gene. From these data, it was
inferred that most, if not all Delta ccr5 alleles originate from a single
mutation event, and that this mutation event probably took place a few
thousand years ago in Northeastern Europe. The high frequency of the Delta
ccr5 allele in Caucasian populations cannot be explained easily by random
genetic drift, suggesting that a selection advantage is or has been
associated with homo- or heterozygous carriers of the Delta ccr5 allele.
相似文献
52.
P Sgouropoulos J C Baron Y Samson M G Bousser D Comar P Castaigne 《Revue neurologique》1985,141(11):698-705
Using positron emission tomography and the 15O continuous inhalation technique, we have measured the regional cerebral blood flow (rCBF) oxygen extraction fraction (rOEF) and oxygen consumption (rCMRO2) of non-infarcted tissue in six patients with either tight stenosis (N = 3) or occlusion (N = 3) of the trunk of the middle cerebral artery (MCA); these arterial lesions were shown to be persistent on late and/or repeated angiograms. The patients were studied 1 to 6 months after their last cerebral ischemic event. The data were analyzed in 4 cm2 regions of interest (fig. 1) and were compared to age-matched control values. Regional right/left ratios were tested for significance individually by comparison to 95 p. 100 confidence limits found in control subjects. We found a significant reduction in mean rCBF in the affected MCA territory; concomitantly, there was a lesser decrease in rCMRO2 significant only in the peri-sylvian area; this was associated with a moderate but significant increase in rOEF in the same areas (Table II, fig. 2 and 3). Individually, the reduction in rCBF and the increased rOEF were significant in 5/6 and 2/6 patients, respectively (Table III). These data indicate that rCBF is decreased distal to persistent hemodynamic MCA obstruction in most patients. This hypoperfusion appears due in part to a mild degree of cerebral ischemia (as demonstrated by the occurrence of "misery perfusion"), indicating inadequate perfusion pressure distal to the MCA obstruction. This was associated with a metabolic depression of the cortex possibly resulting from either neuronal loss, or deactivation (diaschisis), or long-standing hemodynamic local failure or any combination of the three.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
53.
Effects of extra-intracranial arterial bypass on cerebral blood flow and oxygen metabolism in humans 总被引:6,自引:0,他引:6
Y Samson J C Baron M G Bousser A Rey J M Derlon P David J Comoy 《Stroke; a journal of cerebral circulation》1985,16(4):609-616
Twelve patients, eleven with a carotid obstruction and one with an occlusion of the middle cerebral artery, were studied before and after a successful unilateral extra-intracranial arterial by-pass, (EIAB) using PET and the 15-0 steady-state technique to measure regional cerebral blood flow (CBF), oxygen extraction fraction and oxygen metabolic rate (CMRO2). In the whole group of patients, both CBF and CMRO2 increased significantly on both cerebral hemispheres after EIAB, returning toward control levels defined in age-matched subjects. Mean oxygen extraction fraction, on the other hand, was not affected. Individually, three different effects of EIAB emerged: 1) Alleviation of a state of long standing unilateral "misery-perfusion", as reported earlier; 2) parallel increase of CBF and CMRO2 bilaterally, which appeared due to improvement of a hemodynamic depression of metabolism, the precise mechanism of which remains obscure; 3) Complex, unexpected changes in the CBF-CMRO2 couple again resulting in increases in CMRO2. This metabolic improvement afforded by EIAB in our patients has not been reported before; it suggests that long-standing hemodynamic failure may induce a metabolic depression that is still potentially reversible by surgical revascularization. 相似文献
54.
Ellen M H Mitchell Olusola Adedeji Adejumo Hussein Abdur-Razzaq Chidubem Ogbudebe Nkem Chukwueme Samson Bamidele Olorunju Mustapha Gidado 《JMIR Public Health and Surveillance》2021,7(3)
BackgroundThe greatest risk of infectious disease undernotification occurs in settings with limited capacity to detect it reliably. World Health Organization guidance on the measurement of misreporting is paradoxical, requiring robust, independent systems to assess surveillance rigor. Methods are needed to estimate undernotification in settings with incomplete, flawed, or weak surveillance systems. This study attempted to design a tuberculosis (TB) inventory study that balanced rigor with feasibility for high-need settings.ObjectiveThis study aims to design a hybrid TB inventory study for contexts without World Health Organization preconditions. We estimated the proportion of TB cases that were not reported to the Ministry of Health in 2015. The study sought to describe TB surveillance coverage and quality at different levels of TB care provision. Finally, we aimed to identify structural-, facility-, and provider-level barriers to notification and reasons for underreporting, nonreporting, and overreporting.MethodsRetrospective partial digitalization of paper-based surveillance and facility records preceded deterministic and probabilistic record linkage; a hybrid of health facilities and laboratory census with a stratified sampling of HFs with no capacity to notify leveraged a priori knowledge. Distinct extrapolation methods were applied to the sampled health facilities to estimate bacteriologically confirmed versus clinical TB. In-depth interviews and focus groups were used to identify causal factors responsible for undernotification and test the acceptability of remedies.ResultsThe hybrid approach proved viable and instructive. High-specificity verification of paper-based records in the field was efficient and had minimal errors. Limiting extrapolation to clinical cases improved precision. Probabilistic record linkage is computationally intensive, and the choice of software influences estimates. Record absence, decay, and overestimation of the private sector TB treatment behavior threaten validity, meriting mitigation. Data management demands were underestimated. Treatment success was modest in all sectors (R=37.9%–72.0%) and did not align with treatment success reported by the state (6665/8770, 75.99%). One-fifth of TB providers (36/178, 20%) were doubtful that the low volume of patients with TB treated in their facility merited mastery of the extensive TB notification forms and procedures.ConclusionsSubnational inventory studies can be rigorous, relevant, and efficient in countries that need them even in the absence of World Health Organization preconditions, if precautions are taken. The use of triangulation techniques, with minimal recourse to sampling and extrapolation, and the privileging of practical information needs of local decision makers yield reasonable misreporting estimates and viable policy recommendations. 相似文献
55.
B Angus J Purvis D Stock B R Westley A C Samson E G Routledge F H Carpenter C H Horne 《The Journal of pathology》1987,153(4):377-384
Production of a new monoclonal antibody designated NCL-5D3 is described. The antibody recognizes several low molecular weight cytokeratins, in particular cytokeratin Moll number 8 as determined by immunoblotting studies, and is highly effective for immunocytochemistry using routinely processed paraffin-embedded material. Staining is enhanced by prior treatment of the sections with trypsin. Assessment using a wide variety of normal and neoplastic tissue indicates reactivity with all tissues of simple or glandular epithelial origin, and in addition with many squamous carcinomas. Thus the antibody should prove of value in diagnostic histopathology. 相似文献
56.
Objective. To undertake the pilot experiments of prevention of disability (POD) in 14 different geographical areas to serve as examples for future development of rehabilitation work in China and in Asia. Mahods. According to the principles mid national criterion, 27 000 people affected by leprosy were selected and assessed using disability record forms at beginning and followed up regularly for observing changes of different indica-tors. Results. A total of 197 neuritis cases were detected and treated with prednisolone out of 1 407 new or active cas-es. Serf-care training of eyes, hands and feet were conducted for 10 500 disabled people affected by leprosy. Compre-hensive therapy was given to 1 804 cases having comphcated ulcers of which 1 055 cases have got their ulcers healed. Out of 706 prostheses, 613 were given to patients with satisfactory results. Surgical treatment was given to 269 cases and 251 have shown good progress. Conclusion. Most of patients have got benefit from the project in function or appearance which is very helpful for their going back to the society and agreed by foreign experts during the final evaluation. The experiences from the pro-ject can be implemented in the whole country. 相似文献
57.
To find out the efficacy of sucralfate in preventing gastrointestinal side effects of non-steroidal anti-inflammatory drugs (NSAIDs) a prospective, randomised single blind study was conducted from 1989 to 1992. Patients with osteoarthritis, rheumatoid arthritis and other long standing painful conditions, who were expected to receive NSAIDs for over three months, were recruited into the study. All medicines were discontinued for a period of 10–15 days prior to initial endoscopic assessment. NSAID therapy was started and the patients were randomised to receive either placebo (group A) or sucralfate (group B) in addition. Patient were reassessed clinically every week and an endoscopic examination was repeated after 6–8 weeks of follow-up. A total of 176 patients were studied in group A (n=91) and group B (n=85). At the end of 8 weeks gastrointestinal symptoms were present in 30.6% and 26.4% patients of group A and B respectively. Endoscopic assessment showed superficial lesions in 36.5% and 18.7% while endoscopic ulcer in 2.4% and 1.1% patients of groups A and B respectively. Thus in patients receiving chronic NSAID therapy, simultaneous administration of sucralfate reduces the incidence of superficial gastric lesions but has no significant effect on symptoms or ulcer formation.KEY WORDS: Gastropathy, Sucralfate, Nonsteroidal anti-inflammatory drugs 相似文献
58.
59.
To evaluate the risk of definitive intracranial microsurgical aneurysm obliteration as a function of the timing of the operative intervention, we retrospectively reviewed 106 consecutive patients in good clinical condition who underwent such surgery. The patients who were operated upon within the first 8 days of their most recent subarachnoid hemorrhage formed the "early" group; the patients operated upon between the 9th and 31st day were considered to have undergone "late" surgery. On the basis of their clinical outcome the patients were allocated to one of four outcome categories ("good," "fair," "death") both at the time of their hospital discharge and at their most recent clinical re-evaluation, a minimum of 6 months after discharge from the hospital. There was no significant difference in the operative mortality in each group (early surgery, 5%; late surgery, 4%); additionally, no significant difference was noted in the incidence of either intraoperative complications or postoperative morbidity. A suggestive but statistically insignificant increase in the incidence of postoperative cerebral ischemic events was seen in the "early" surgery group (8% vs. 4% for the "late" surgery group). The potential significance of these findings for the timing of intracranial aneurysm surgery is discussed. 相似文献
60.
JP Bound PW Harvey BJ Francis F Awwad AC Gatrell 《Archives of disease in childhood》1997,76(2):107-112
OBJECTIVE: To analyse the prevalence of neural tube defects in small geographical areas and seek to explain any spatial variations with reference to environmental lead and deprivation. SETTING: The Fylde of Lancashire in the north west of England. DESIGN: Cases were ascertained as part of a prospective survey of major congenital malformations in babies born in the Fylde to residents there between 1957 and 1981. A matched case-control analysis used infants with cardiovascular system, alimentary tract, and urinary system malformations as controls. Conditional logistic regression was used to assess the effects of more than 10 micrograms/l lead in drinking water and the Townsend deprivation score. RESULTS: The prevalence of neural tube defects in 1957-73 was higher in Blackpool, Fleetwood, and North Fylde, whereas the three control groups showed no significant spatial variation. In 1957-81 mothers living in electoral wards with either a higher proportion of houses with more than 10 micrograms/l lead in the water or a higher deprivation score had a greater risk of having a baby with a neural tube defect. For spina bifida and cranium bifidum alone, this was also true. For anencephaly, deprivation was less important although the effect of lead was still seen. In some neural tube defects, lead may act independently of other possible factors associated with deprivation. It seemed unlikely that lead levels changed significantly during the survey. The percentage of houses with 10 micrograms/l or more of lead in the water in 1984-5 was similar to that found in Great Britain 10 years previously. CONCLUSION: There is evidence to suggest that lead is one cause of neural tube defects, especially anencephaly. This could link the known preventive actions of hard water and folic acid. Calcium is a toxicological antagonist of lead. One cause of a deficiency of folic acid is impaired absorption secondary to zinc deficiency, which may be produced or exacerbated by lead. 相似文献