全文获取类型
收费全文 | 48460篇 |
免费 | 2289篇 |
国内免费 | 387篇 |
专业分类
耳鼻咽喉 | 488篇 |
儿科学 | 939篇 |
妇产科学 | 1375篇 |
基础医学 | 5851篇 |
口腔科学 | 1839篇 |
临床医学 | 3724篇 |
内科学 | 13347篇 |
皮肤病学 | 958篇 |
神经病学 | 4251篇 |
特种医学 | 1313篇 |
外科学 | 7450篇 |
综合类 | 186篇 |
一般理论 | 9篇 |
预防医学 | 2592篇 |
眼科学 | 741篇 |
药学 | 2714篇 |
中国医学 | 130篇 |
肿瘤学 | 3229篇 |
出版年
2024年 | 45篇 |
2023年 | 337篇 |
2022年 | 820篇 |
2021年 | 1539篇 |
2020年 | 834篇 |
2019年 | 1190篇 |
2018年 | 1634篇 |
2017年 | 1084篇 |
2016年 | 1180篇 |
2015年 | 1385篇 |
2014年 | 1899篇 |
2013年 | 2522篇 |
2012年 | 3834篇 |
2011年 | 3791篇 |
2010年 | 2119篇 |
2009年 | 1863篇 |
2008年 | 3210篇 |
2007年 | 3368篇 |
2006年 | 3154篇 |
2005年 | 3060篇 |
2004年 | 2773篇 |
2003年 | 2502篇 |
2002年 | 2213篇 |
2001年 | 391篇 |
2000年 | 310篇 |
1999年 | 376篇 |
1998年 | 398篇 |
1997年 | 352篇 |
1996年 | 305篇 |
1995年 | 301篇 |
1994年 | 234篇 |
1993年 | 172篇 |
1992年 | 177篇 |
1991年 | 145篇 |
1990年 | 150篇 |
1989年 | 120篇 |
1988年 | 100篇 |
1987年 | 96篇 |
1986年 | 97篇 |
1985年 | 98篇 |
1984年 | 95篇 |
1983年 | 87篇 |
1982年 | 102篇 |
1981年 | 76篇 |
1980年 | 81篇 |
1979年 | 56篇 |
1978年 | 57篇 |
1977年 | 50篇 |
1976年 | 46篇 |
1974年 | 41篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Foxl2 disruption causes mouse ovarian failure by pervasive blockage of follicle development 总被引:6,自引:0,他引:6
Uda M Ottolenghi C Crisponi L Garcia JE Deiana M Kimber W Forabosco A Cao A Schlessinger D Pilia G 《Human molecular genetics》2004,13(11):1171-1181
FOXL2 mutations cause gonadal dysgenesis or premature ovarian failure (POF) in women, as well as eyelid/forehead dysmorphology in both sexes (the 'blepharophimosis-ptosis-epicanthus inversus syndrome', BPES). Here we report that mice lacking Foxl2 recapitulate relevant features of human BPES: males and females are small and show distinctive craniofacial morphology with upper eyelids absent. Furthermore, in mice as in humans, sterility is confined to females. Features of Foxl2 null animals point toward a new mechanism of POF, with all major somatic cell lineages failing to develop around growing oocytes from the time of primordial follicle formation. Foxl2 disruption thus provides a model for histogenesis and reproductive competence of the ovary. 相似文献
92.
Rodrigues FC Kawasaki-Oyama RS Fo JF Ukuyama EE Antonio JR Bozola AR Romeiro JG Rahal P Tajara EH 《Cancer Genetics and Cytogenetics》2003,142(2):92-98
The CDKN1A (TP21) gene encodes a 21-kD protein that is a critical downstream mediator of wild-type TP53 and an important regulator of the cell cycle. Failure in the function of this gene would be expected to result in abnormal cell proliferation and transformation. Tumor-associated mutations of the coding region of the TP21 are rare. On the other hand, some TP21 polymorphisms have been identified and characterized by single base substitutions. In the present study, we investigated the potential role of TP21 gene polymorphisms in skin, head, and neck tumorigenesis. A total of 261 samples were examined by polymerase chain reaction single-strand conformational analysis, and one mutation at codon 31 and four polymorphisms in exons 2 (codon 55) and 3 [nucleotide (nt)590] and in promoter region (nt2298) were identified. In conclusion, this investigation confirmed the rarity of mutations in this gene, arguing against a role for TP21 mutations in skin, head, and neck cancers. Also, our results show significant differences in nt2298 allele frequencies between normal individuals and skin malignant tumors (P < 0.05). The results suggest that this polymorphism affects TP21 transactivator binding and may be important during the pathogenesis of skin cancer. 相似文献
93.
The potential for a bioterrorism-induced smallpox outbreak has been much discussed of late. The literature of the late 1960s stressed that the distinction between smallpox and the other viral-induced vesicle-forming diseases, namely varicella zoster and disseminated herpes simplex, was difficult to make. Given that the cutaneous manifestations of smallpox would be among the initial symptoms, we reviewed 2 cases of smallpox diagnosed in South America in the 1970s in conjunction with 9 cases of multiple skin vesicles diagnosed as either disseminated herpes simplex or varicella-zoster. These were examined by routine hematoxylin and eosin stain (H&E) as well as by in situ hybridization. A blind review of the cases demonstrated that each showed striking intraepithelial vesicles containing multinucleated squamous cells exhibiting a ground glass appearance of the nuclear chromatin. Thus, as expected, routine H&E examination could not differentiate the 2 smallpox cases from the other 9 samples. In situ hybridization easily distinguished the 2 cases of smallpox from the other 9 samples, 5 of which contained varicella-zoster (two had been misdiagnosed as herpes) and the other 4 were disseminated herpes simplex. The in situ test, readily accomplished in any histology-based molecular laboratory in 4 hours, allows for the rapid and specific identification of smallpox infection and, importantly, its distinction from its mimics. Formalin fixation, which is optimal for in situ hybridization, guarantees the inactivation of the smallpox virus. 相似文献
94.
Alteration of the LRP1B gene region is associated with high grade of urothelial cancer 总被引:6,自引:0,他引:6
Langbein S Szakacs O Wilhelm M Sukosd F Weber S Jauch A Lopez Beltran A Alken P Kälble T Kovacs G 《Laboratory investigation; a journal of technical methods and pathology》2002,82(5):639-643
We have delineated regions of interest at chromosome 2q21.2, 2q36.3, and 2q37.1 by deletion mapping of 114 urothelial cancers (UC). Altogether, 17%, 18%, and 63% of the G1, G2, and G3 tumors displayed loss of heterozygosity at chromosome 2q, respectively, The region at 2q21.2 was narrowed down to the LRP1B gene (NT_005129.6). Hemi- and homozygous deletion at the LRP1B gene region was seen in 31 of 114 UCs. Only 8% of the UCs with G1 and none with G2 tumors showed loss of heterozygosity at the LRP1B gene, whereas 49% of the G3 UCs had allelic loss at this region. RT-PCR analysis of the LRP1B gene showed the lack of expression of several exons in 2 of 9 cases analyzed. Our analysis suggests that the LRP1B gene is a candidate tumor suppressor gene in UCs. 相似文献
95.
Lorenzo-Morales J Ortega-Rivas A Foronda P Martínez E Valladares B 《Parasitology research》2005,95(4):273-277
A comprehensive survey to document the presence of free-living amoebae of the genus Acanthamoeba was conducted in tap water and sea water sources related to human environments in Tenerife, Canary Islands, Spain. Acanthamoeba identification was based on the morphology of cyst and trophozoite forms and PCR amplification with a genus-specific primer pair. The pathogenic potential of Acanthamoeba isolates was characterized by temperature and osmotolerance assays and PCR reactions with two primer pairs related to Acanthamoeba pathogenesis. The results demonstrate the presence of potentially pathogenic strains in both sources. Thus, some of the amoebae in these aquatic habitats can act as opportunistic pathogens, could play a role in the diseases of aquatic organisms, and may present a risk to human health. 相似文献
96.
Montalto G Giannitrapani L Soresi M Virruso L Martino DD Gambino R Carroccio A Cervello M 《Inflammation》2001,25(2):101-108
E-selectin, an adhesion molecule of the selectin family, is involved in leukocyte adhesion to the endothelium and in the cellular immunological reactions. Expression of this molecule, in fact, is physiologically absent, but it becomes evident on sinusoidal lining cells during inflammatory liver disease. The aim of this study was to evaluate the behavior of E-selectin in chronic hepatitis C (CH-C) patients with persistently normal transaminase in comparison to patients with CH-C and elevated transaminase, and its changes during alpha-interferon therapy. Immunohistochemical localization of E-selectin was also performed on liver tissue specimens of both groups. Fifty-eight subjects were divided into 3 groups: group A included 18 patients with CH-C and persistently normal transaminase; group B 20 patients with CH-C and persistently elevated transaminase levels and group C included 20 healthy subjects, representing the control group. The first two groups were treated with r-IFN at a dose of 6 MU 3 times a week for 3 months and followed-up with 3 MU 3 times a week for another 3 months. Serum baseline values of E-selectin in groups A and B were significantly higher than those in group C (P < 0.04), but there was no difference between groups A and B. Furthermore, there was a trend toward higher E-selectin values as histological severity increased (r = 0.69; P < 0.0001). Post-treatment E-selectin serum values showed a moderate decrease in both groups, but only among responder patients; while E-selectin levels were unchanged in non responders. Immunohistochemical localization showed no staining for E-selectin in normal liver specimens, while there was a quite similar staining for E-selectin in the two groups of patients. In conclusion, this study shows that serum E-selectin levels in patients with CH-C and persistently normal transaminase are higher than in controls and they are associated with severity of liver disease. Liver of these patients express E-selectin molecules, suggesting an activation of the immune system almost identical to that of patients with CH-C and elevated transaminase. In both groups only responder patients showed a moderate decrease below baseline serum values. 相似文献
97.
98.
An unusual variant of composite lymphoma: a short case report and review of the literature 总被引:2,自引:0,他引:2
We recently encountered an unusual case of composite lymphoma arising in a 73-year-old man with a history of follicular small cleaved cell lymphoma. The neoplasm was composed of follicular small cleaved cell lymphoma and nodular sclerosing Hodgkin disease within a single groin lymph node. In addition to morphologic evidence, the immunologic studies performed in this case demonstrated the simultaneous occurrence of 2 separate lymphocytic proliferations. To the best of our knowledge, only one such histologic type has been reported in the literature.1 Hodgkin lymphoma can develop in patients with non-Hodgkin disease and vice versa, especially after treatment. The simultaneous occurrence of Hodgkin disease and non-Hodgkin lymphoma in a single lymph node is extremely rare. In this article, the relationship between Hodgkin disease and non-Hodgkin lymphoma is explored, possible explanations for the occurrence of composite lymphoma are discussed, and the literature is reviewed. 相似文献
99.
John David N. Dionisio Alfonso F. Cárdenas PhD Robert B. Lufkin Antonio DeSalles Keith L. Black Ricky K. Taira Wesley W. Chu 《Journal of digital imaging》1997,10(1):21-26
A prototype multimedia medical database is described for supporting thermal ablation therapy of brain tumors. Its design is motivated by the major need to manage and access multimedia information on the progress and reaction of tumors to various therapy protocols. The database links images to patient data in a way that permits the user to view and query medical information using alphanumeric, temporal, and feature-based predicates. Visualization programs permit the user to view or annotate the query results in various ways. These results support the wide variety of data types and presentation methods required by neuroradiologists to manage thermal ablation therapy data. The database satisfactorily meets the requirements defined by thermal ablation therapy. A similar approach is being undertaken for supporting different therapies of other types of tumors, thus showing the generality of our approach. 相似文献
100.
The yeast Phaffia rhodozyma, a promising microbial producer of the carotenoid astaxanthin, was cultivated in batch and continuous processes in an agitated and aerated fermenter using an acid peat extract - based culture medium. For the accelerated growth phase, the mean specific growth rate and doubling time were found to be 0.038 h?1, and 18.24 hours, respectively. The production of astaxanthin was found to be basically growth associated, the maximum concentrations of the pigment produced in batch culture and continuous cultivation being similar. 相似文献