全文获取类型
收费全文 | 599篇 |
免费 | 40篇 |
国内免费 | 16篇 |
专业分类
儿科学 | 44篇 |
妇产科学 | 13篇 |
基础医学 | 76篇 |
口腔科学 | 15篇 |
临床医学 | 73篇 |
内科学 | 121篇 |
皮肤病学 | 4篇 |
神经病学 | 17篇 |
特种医学 | 103篇 |
外科学 | 35篇 |
综合类 | 38篇 |
一般理论 | 1篇 |
预防医学 | 50篇 |
眼科学 | 2篇 |
药学 | 53篇 |
中国医学 | 1篇 |
肿瘤学 | 9篇 |
出版年
2021年 | 3篇 |
2019年 | 5篇 |
2018年 | 6篇 |
2017年 | 8篇 |
2016年 | 8篇 |
2015年 | 11篇 |
2014年 | 13篇 |
2013年 | 23篇 |
2012年 | 20篇 |
2011年 | 18篇 |
2010年 | 29篇 |
2009年 | 21篇 |
2008年 | 15篇 |
2007年 | 22篇 |
2006年 | 15篇 |
2005年 | 10篇 |
2004年 | 15篇 |
2003年 | 15篇 |
2002年 | 13篇 |
2001年 | 8篇 |
2000年 | 15篇 |
1999年 | 20篇 |
1998年 | 25篇 |
1997年 | 29篇 |
1996年 | 28篇 |
1995年 | 20篇 |
1994年 | 19篇 |
1993年 | 17篇 |
1992年 | 8篇 |
1991年 | 9篇 |
1990年 | 8篇 |
1989年 | 23篇 |
1988年 | 17篇 |
1987年 | 14篇 |
1986年 | 13篇 |
1985年 | 10篇 |
1984年 | 10篇 |
1983年 | 9篇 |
1982年 | 4篇 |
1981年 | 7篇 |
1980年 | 12篇 |
1979年 | 4篇 |
1978年 | 4篇 |
1977年 | 7篇 |
1976年 | 4篇 |
1975年 | 7篇 |
1974年 | 3篇 |
1973年 | 5篇 |
1968年 | 3篇 |
1962年 | 3篇 |
排序方式: 共有655条查询结果,搜索用时 0 毫秒
1.
Sonoelasticity imaging of prostate cancer: in vitro results 总被引:2,自引:0,他引:2
2.
Screening for early ovarian cancer 总被引:5,自引:0,他引:5
3.
Oral hairy leukoplakia: ultrastructural features 总被引:2,自引:0,他引:2
Ten instances of a white plaque of the lateral tongue unique to homosexual males and referred to as oral hairy leukoplakia were analysed ultrastructurally. The surface epithelial layer exhibited extracellular, intracellular and intranuclear penetration by hyphae of Candida albicans, sometimes accompanied by coccobacilli in the extracellular space. The subcorneal epithelial layer included koilocytoid ballooned cells which had a paucity of cytoplasmic organelles and displayed condensation and emargination of the chromatin. Cells that exhibited these nuclear changes were found to be infected by a herpes-type virus which was visualized by electron microscopy in all ten cases. Clusters of nucleocapsids (86-110 nm in diameter) occurred in the nuclei and enveloped virions (111-175 nm in diameter) occurred in the cytoplasm and extracellular spaces. Virions showed budding from the nuclear envelope. Bundles of tubular structures (20 nm diameter) arranged in parallel occurred in the cytoplasm of some koilocytoid cells. There was no evidence by electron microscopy of the presence of papilloma virus within koilocytotic nuclei. 相似文献
4.
The contribution of the flocculus region of the cerebellum to horizontal gaze pursuit was studied in squirrel monkeys. When the head was free to move, the monkeys pursued targets with a combination of smooth eye and head movements; with the majority of the gaze velocity produced by smooth tracking head movements. In the accompanying study we reported that the flocculus region was necessary for cancellation of the vestibuloocular reflex (VOR) evoked by passive whole body rotation. The question addressed in this study was whether the flocculus region of the cerebellum also plays a role in canceling the VOR produced by active head movements during gaze pursuit. The firing behavior of 121 Purkinje (Pk) cells that were sensitive to horizontal smooth pursuit eye movements was studied. The sample included 66 eye velocity Pk cells and 55 gaze velocity Pk cells. All of the cells remained sensitive to smooth pursuit eye movements during combined eye and head tracking. Eye velocity Pk cells were insensitive to smooth pursuit head movements. Gaze velocity Pk cells were nearly as sensitive to active smooth pursuit head movements as they were passive whole body rotation; but they were less than half as sensitive ( approximately 43%) to smooth pursuit head movements as they were to smooth pursuit eye movements. Considered as a whole, the Pk cells in the flocculus region of the cerebellar cortex were <20% as sensitive to smooth pursuit head movements as they were to smooth pursuit eye movements, which suggests that this region does not produce signals sufficient to cancel the VOR during smooth head tracking. The comparative effect of injections of muscimol into the flocculus region on smooth pursuit eye and head movements was studied in two monkeys. Muscimol inactivation of the flocculus region profoundly affected smooth pursuit eye movements but had little effect on smooth pursuit head movements or on smooth tracking of visual targets when the head was free to move. We conclude that the signals produced by flocculus region Pk cells are neither necessary nor sufficient to cancel the VOR during gaze pursuit. 相似文献
5.
Inhibition of terminal axonal sprouting by serum from patients with amyotrophic lateral sclerosis 总被引:5,自引:0,他引:5
To investigate the pathogenesis of amyotrophic lateral sclerosis, we compared the effect of serum from patients with this disease on the regenerative sprouting of terminal axons in botulinum-treated mouse gluteus muscle with the effects of serum from controls and from patients with diabetic peripheral neuropathy. Serum from 9 of 19 patients with the sporadic form of amyotrophic lateral sclerosis and from 2 of 6 patients with the familial form caused a reduction in the proportion of sprouting terminal axons, as compared with that found in muscles treated with serum from controls or diabetic patients. Immunoglobulin from patients with amyotrophic lateral sclerosis, when tested on immunoblots, recognized a 56-kilodalton protein secreted by denervated rat diaphragm muscle; rabbit antiserum raised against this protein also suppressed terminal axonal sprouting. Thus, we have detected an antibody in the serum of patients with amyotrophic lateral sclerosis that inhibits sprouting of neurons and subsequent reinnervation of skeletal muscle. Whether this antibody is of primary pathogenic importance or represents a secondary response to neuromuscular destruction is not known. In either case, serum from patients with amyotrophic lateral sclerosis may provide reagents for studies of the trophic communications between muscle and motor neurons. 相似文献
6.
7.
8.
Pathways to care for alcohol use disorders 总被引:1,自引:0,他引:1
9.
Rea IM McKeown PP McMaster D Young IS Patterson C Savage MJ Belton C Marchegiani F Olivieri F Bonafe M Franceschi C 《Experimental gerontology》2004,39(4):629-635
BACKGROUND: PON1, an arylesterase, associated with high density lipoprotein (HDL), protects low density lipoprotein (LDL) against oxidative modification. Common polymorphisms PON1 55 (L/M) and 192 (Q/R) in the PON1 gene associate with atherosclerosis and heart disease. Because long-lived people seem protected from premature vascular death, we conducted a pooled statistical analysis to assess any association between these polymorphisms and longevity in a large combined group of Italian centenarians and octo/nonagenarians from Northern Ireland (NI). MATERIALS AND METHODS: Separated DNA was available from 1479 subjects from Italy and Northern Ireland (NI). In Italy 308 centenarians (males 67, females 241, mean age 100.8, SD2.1 years) and 579 young controls (males 347, females 232, mean age 40.7, SD 12.7 years) were included in the study. In NI, 296 octo/nonagenarians (males 92, females 204, mean age 89.8, SD 5.7 years) and 296 young sex-matched subjects (mean age 13.0, SD 1.4 years) had available DNA. PON1 55 (L/M) and 192 (Q/R) polymorphisms were studied using a PCR-RFLP approach. RESULTS: There was a significant difference in PON1 192 genotypes in Italian centenarians compared to younger controls (X(2)= 6.8, df = 2 p= 0.03) and a similar but non significant trend between octo/nonagenarian and young subjects in NI (X(2) = 4.0, df=2, p=0.14). Using logistic regression analysis on the combined Italian and Irish datasets, there was a small survival advantage for centenarian and octo/nonagenarian subjects who were heterozygous for PON1 192 R allele, (OR 1.3, CI 1-1.6; p=0.04 with a stepwise increase for RR homozygous subjects (OR 1.7, CI 1.1-2.6; p = 0.02) compared to QQ subjects. Comparing R and Q alleles there was a survival advantage for octo/nonagenarian/centenarian subjects who carried the R allele (OR 1.3, CI 1.1-1.5; p = 0.007) but there was no sex-specific effect p =0.77) LL, LM and MM genotypes of PON 55 polymorphisms showed similar frequencies in Italy (39.9, 47.0, 13.1%) and Ireland (39.5, 48.6, 11.9%) with no age or sex-related differences. The PON1 192R/Q and PON55L/M loci were in strong linkage disequilibrium with a Lewontin's D' coefficient -0.928 (elderly) and -0.965 (young). There was a significant difference in haplotype frequency of these linked loci in older compared to younger subjects (Likelihood Ratio X(2) = 9.60, df = 3, p= 0.02). CONCLUSION: These data suggest a modest association between the 192R allele and longevity in two very elderly populations in two European countries. Being homozygous for 192 RR further enhances survival advantage but this effect was not found to be sex specific. This finding is of interest because the 192R allele has previously been associated with increased risk of coronary heart disease. On the other hand, the 192R allele shows higher enzymatic activity, using paraoxon as substrate, and we postulate that its role in the metabolism of potentially toxic chemicals or other metabolic pathways may be important in survival to very old age. 相似文献
10.
A Hodgkin cell-specific antigen is expressed on a subset of auto- and alloactivated T (helper) lymphoblasts 总被引:21,自引:0,他引:21
A Hodgkin cell-specific antigen detected by the monoclonal antibody Ki- 1 was found on T helper lymphocytes after activation by autologous and allogeneic stimulator cells. About 50% of lymphoblasts generated by auto- and alloactivation reacted with the antibody. In contrast, only less than 6% of lymphoblasts stimulated with Con-A, phytohemagglutinin (PHA), or protein A, and none of lymphoblasts activated by oxidative mitogenesis, expressed this antigen. Among several permanent cell lines tested, the K562, MOLT-4, HL-60, and EBV transformed B lymphoblastoid cells reacted with the Ki-1 antibody. The results may indicate possible relationships between the autoreactive subset of T lymphocytes and the pathogenesis of Hodgkin's disease. 相似文献