全文获取类型
收费全文 | 30113篇 |
免费 | 1854篇 |
国内免费 | 161篇 |
专业分类
耳鼻咽喉 | 305篇 |
儿科学 | 837篇 |
妇产科学 | 640篇 |
基础医学 | 4401篇 |
口腔科学 | 2547篇 |
临床医学 | 2525篇 |
内科学 | 5899篇 |
皮肤病学 | 641篇 |
神经病学 | 2180篇 |
特种医学 | 769篇 |
外国民族医学 | 1篇 |
外科学 | 3261篇 |
综合类 | 660篇 |
一般理论 | 7篇 |
预防医学 | 3395篇 |
眼科学 | 381篇 |
药学 | 2222篇 |
3篇 | |
中国医学 | 380篇 |
肿瘤学 | 1074篇 |
出版年
2023年 | 289篇 |
2022年 | 679篇 |
2021年 | 1100篇 |
2020年 | 771篇 |
2019年 | 942篇 |
2018年 | 1072篇 |
2017年 | 821篇 |
2016年 | 832篇 |
2015年 | 979篇 |
2014年 | 1264篇 |
2013年 | 1509篇 |
2012年 | 2316篇 |
2011年 | 2528篇 |
2010年 | 1364篇 |
2009年 | 1048篇 |
2008年 | 1717篇 |
2007年 | 1618篇 |
2006年 | 1484篇 |
2005年 | 1213篇 |
2004年 | 1037篇 |
2003年 | 919篇 |
2002年 | 822篇 |
2001年 | 598篇 |
2000年 | 644篇 |
1999年 | 510篇 |
1998年 | 208篇 |
1997年 | 159篇 |
1996年 | 165篇 |
1995年 | 146篇 |
1994年 | 130篇 |
1993年 | 104篇 |
1992年 | 222篇 |
1991年 | 221篇 |
1990年 | 213篇 |
1989年 | 206篇 |
1988年 | 200篇 |
1987年 | 153篇 |
1986年 | 130篇 |
1985年 | 147篇 |
1984年 | 123篇 |
1983年 | 92篇 |
1979年 | 87篇 |
1978年 | 78篇 |
1975年 | 62篇 |
1974年 | 62篇 |
1973年 | 63篇 |
1958年 | 67篇 |
1957年 | 77篇 |
1956年 | 75篇 |
1955年 | 84篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
This study investigated the effects of riluzole (Ril), creatine (Cr) and a combination of these treatments on the onset and progression of clinical signs and neuropathology in an animal model of familial amyotrophic lateral sclerosis, the G93A transgenic mouse (n=13-17 per group). The onset of clinical signs was delayed (P<0.05) by about 12 days in all treatment groups compared with control; however, no differences occurred between treatments. All animals were killed at 199 days of age. At the end of the experimental period the severity of clinical signs was less (P<0.05) with all treatments compared with control. Again no differences between treatments were observed. The treatments had no effect on the number of neurons in ventral horns of the lumbar region of the spinal cord. Transgenic mice ingesting Cr displayed elevated (P<0.05) total Cr levels in cerebral hemispheres (5%) and spinal cord (8%), but not skeletal muscles. These data demonstrate that treatment with Ril and Cr were both effective in delaying disease onset and clinical disability. To the age of killing, no additional benefit was conferred by co-administration of Ril and Cr. 相似文献
102.
A case of poorly differentiated Sertoli-Leydig cell tumor with elevated serum alpha-fetoprotein (AFP) levels occurred in a 17-year-old girl. No germ cell component and no heterologous elements were identified, but a retiform pattern was present. Immunohistochemical studies demonstrated immunoreactivity for AFP and testosterone in Leydig's cells only. Secretion of AFP by Sertoli-Leydig cell tumors has rarely been mentioned previously, and its mechanism is difficult to explain. Non-germ cell tumors must be considered in the differential diagnosis of ovarian tumors with elevated serum AFP levels. 相似文献
103.
104.
Quantitative evaluation of the rRNA in Alzheimer's disease 总被引:2,自引:0,他引:2
da Silva AM Payão SL Borsatto B Bertolucci PH Smith MA 《Mechanisms of ageing and development》2000,120(1-3):57-64
105.
The patterns of exochorion ornaments on eggs of seven South American Lutzomyia sand fly species were analyzed by scanning electron microscopy (SEM): Lutzomyia (Lutzomyia) cruzi (Mangabeira 1938), Lutzomyia (Micropygomyia) evandroi (Costa Lima and Antunes 1936), L. (Nyssomyia) intermedia (Lutz and Neiva 1912), L. longipalpis (Lutz and Neiva 1912), L. migonei (Franca 1920), L. (Nyssomyia) neivai (Pinto 1926), and L. renei (Martins, Falcao, and Silva 1957). Different patterns were observed, which showed the distinction between some species. Egg ornaments in L. cruzi and L. longipalpis appear as single, parallel, unconnected ridges, whereas eggs of L. migonei appear as single, parallel, connected ridges. Eggs of L. (Nyssomyia) intermedia and L. (N.) neivai present a new variation of the single, unconnected, parallel ridges pattern: small tubercles are present, distributed between the ridges. Eggs of L. renei present an elliptical pattern, with most structures connected by straight ridges. Eggs of L. (M.) evandroi present a polygonal pattern, with alternate rows of small and large hexagons. Our data emphasize the advantages of the SEM approach in the study of the exochorion patterns of Lutzomyia eggs and in the distinction of the sand fly species. 相似文献
106.
Peruhype-Magalhães V Martins-Filho OA Prata A Silva Lde A Rabello A Teixeira-Carvalho A Figueiredo RM Guimarães-Carvalho SF Ferrari TC Correa-Oliveira R 《Scandinavian journal of immunology》2005,62(5):487-495
We investigated the cytokine profile of cells of the innate immune response and its association with active (ACT), asymptomatic (AS) and cured (CUR) human visceral leishmaniasis (VL), as well as noninfected (NI) subjects. The frequency of cytokine-producing cells was determined after short-term in vitro incubation of whole peripheral blood samples with soluble Leishmania antigen (SLA). Our data demonstrated a predominant type 2 cytokine profile in NI and ACT. In NI, we observed an increase of IL-4+ neutrophils, IL-10+ eosinophils besides a decrease of tumour necrosis factor (TNF)-alpha+ eosinophils/monocytes. Yet in ACT, we observed an increase of IL-4+ neutrophils and natural killer (NK) cells and IL-10+ monocytes, a reduced frequency of IL-12+ and IFN-gamma+ eosinophils and lower levels of TNF-alpha+ and IL-12+ monocytes. AS presented a mixed profile, characterized by an increase of IFN-gamma+ neutrophils/eosinophils and NK cells, of IL-12+ eosinophils/monocytes, as well as increase of IL-4+ neutrophils and NK cells and IL-10+ eosinophils/monocytes. In contrast, CUR was characterized by a type 1 response with an increase of IFN-gamma+ neutrophils/eosinophils and NK cells, associated with an increase in IL-12+ monocytes. In conclusion, we show a correlation between innate immune cytokine patterns and clinical status of VL, suggesting that these cells, in addition to other factors, may contribute to the cytokine microenvironment in which Leishmania-specific T cells are primed and to disease outcome. 相似文献
107.
Gaspar J.; Rodrigues A.; Laires A.; Silva F.; Costa S.; Monteiro M. J.; Monteiro C.; Rueff J. 《Mutagenesis》1994,9(5):445-449
Quercetin has been the subject of numerous studies on its genetictoxicity and carcinogenicity. Despite its well-proven geneticdamaging activity for various genetic end-points (reverse mutations,induction of SOS functions, induction of sister chromatid exchanges,chromosomal aberrations and micronuclei), the mechanisms ofgenetic damage by quercetin remain, by and large, unknown. Thepresent study aims to further extend the observations on thepossible active oxygen species mediated DNA-damaging activityof quercetin and the role of cytochrome P450-dependent metabolismon the genotoxicity of quercetin. The results reported in thiswork show that querceitn can produce the OH radical, as assessedby deoxyribose degradation in the presence of Fe3³/EDTA(ethylenediaminetetraacetic acid), and that it induces strandbreakage in isolated plasmidic DNA (pUC18). The data supportthe hypothesis that the production of OH is mediated by H2O2.The results with genetically engineered V79 cells expressingrat cytochromes 1A1, 1A2 and 2B1 failed to demonstrate metabolismof quercetin, as indicated by the fact that neither an enhancementnor a decrease in the genotoxicity of quercetin was observed.Results obtained on the pH dependence of the induction of chromosomalaberrations by quercetin in V79 cells show that, as the valueof the medium is increased to 8.0, there is a significant increasein the number of aberrant cells, as expected if oxygen radicalsare responsible for the formation of chromosomal aberrations.
3To whom correspondence should be addressed 相似文献
108.
A A Cardoso M Fallon B Mukherji M R Silva M Marusic J Gaffney J L Ascensao 《Clinical immunology and immunopathology》1992,64(2):106-111
We assayed natural killer (NK) cell activity and phenotype from human bone marrow (BM) following "purge" with 4-hydroperoxycyclophosphamide (4HC) at 60 micrograms/ml for 30 min in vitro. In all cases studied, lytic activity against the K562 cell line was either significantly decreased or abolished following 4HC purge. Although NK activity was significantly affected by 4HC treatment, no major differences in the phenotype between the purged and unpurged population were seen. Further, while in vitro culture of BM with IL2 resulted in a significant increment of NK activity, no IL-2 responsive cells were found in the 4HC purged BM after 14 days of culture. This study demonstrates that pharmacological purging of bone marrow results in a persistent functional decline of NK cell activity and may serve as a useful model for the study of the ontogeny of NK cells. 相似文献
109.
R K Rashid B Mackay E G Silva N G Ordó?ez 《Archives of pathology & laboratory medicine》1984,108(2):149-151
Primary small cell (oat cell) carcinoma of the trachea is very rare. We report a case with ultrastructural evidence of endocrine differentiation. Immunoperoxidase staining demonstrated carcinoembryonic antigen and bombesin in the tumor cells. 相似文献
110.
Norihiro Morita W.A. Saad L.A.A. Camargo C.R. Silva Neto J. Antunes-Rodrigues M.R. Covian 《Physiology & behavior》1980,24(2):243-249
Rats bearing lesions in the septal area followed by lesions in the subfornical organ were submitted to various thirst-eliciting procedures. The rats with hyperdipsia induced by lesions of the septal area drank more water than either during the control period or after lesion of the subfornical organ under the same thirst-eliciting or angiotensin-liberating stimuli (polyethyleneglycol, isoproterenol, water deprivation and ligation of the inferior vena cava). The overdrinking elicited by lesions in the septal area was blocked after lesion of the subfornical organ. Neither hypovolemia, nor hypotension or water deprivation could elicit increased water intake in animals whose subfornical organ had been destroyed. Animals with lesions in the subfornical organ showed decreased water intake after cellular dehydration. The results obtained suggest that the subfornical organ acts as a more important structure than the septal area in the regulation of water intake elicited by angiotensin, with two opposite effects: a direct one facilitating water intake, and an indirect one inhibiting the septal area. The septal area has an inhibitory effect on the subfornical organ and on water intake. 相似文献