全文获取类型
收费全文 | 1198篇 |
免费 | 53篇 |
国内免费 | 10篇 |
专业分类
耳鼻咽喉 | 12篇 |
儿科学 | 55篇 |
妇产科学 | 29篇 |
基础医学 | 147篇 |
口腔科学 | 25篇 |
临床医学 | 90篇 |
内科学 | 245篇 |
皮肤病学 | 29篇 |
神经病学 | 61篇 |
特种医学 | 169篇 |
外科学 | 65篇 |
综合类 | 19篇 |
预防医学 | 54篇 |
眼科学 | 48篇 |
药学 | 85篇 |
1篇 | |
中国医学 | 7篇 |
肿瘤学 | 120篇 |
出版年
2021年 | 8篇 |
2019年 | 6篇 |
2018年 | 7篇 |
2017年 | 11篇 |
2016年 | 13篇 |
2015年 | 15篇 |
2014年 | 18篇 |
2013年 | 23篇 |
2012年 | 42篇 |
2011年 | 35篇 |
2010年 | 38篇 |
2009年 | 38篇 |
2008年 | 38篇 |
2007年 | 56篇 |
2006年 | 30篇 |
2005年 | 30篇 |
2004年 | 34篇 |
2003年 | 35篇 |
2002年 | 34篇 |
2001年 | 44篇 |
2000年 | 23篇 |
1999年 | 24篇 |
1998年 | 41篇 |
1997年 | 37篇 |
1996年 | 46篇 |
1995年 | 40篇 |
1994年 | 39篇 |
1993年 | 22篇 |
1992年 | 20篇 |
1991年 | 39篇 |
1990年 | 21篇 |
1989年 | 39篇 |
1988年 | 45篇 |
1987年 | 31篇 |
1986年 | 29篇 |
1985年 | 24篇 |
1984年 | 22篇 |
1983年 | 14篇 |
1982年 | 12篇 |
1981年 | 10篇 |
1980年 | 14篇 |
1979年 | 10篇 |
1978年 | 6篇 |
1977年 | 12篇 |
1976年 | 9篇 |
1975年 | 8篇 |
1973年 | 7篇 |
1970年 | 6篇 |
1968年 | 7篇 |
1967年 | 8篇 |
排序方式: 共有1261条查询结果,搜索用时 15 毫秒
11.
Debelenko LV; Brambilla E; Agarwal SK; Swalwell JI; Kester MB; Lubensky IA; Zhuang Z; Guru SC; Manickam P; Olufemi SE; Chandrasekharappa SC; Crabtree JS; Kim YS; Heppner C; Burns AL; Spiegel AM; Marx SJ; Liotta LA; Collins FS; Travis WD; Emmert-Buck MR 《Human molecular genetics》1997,6(13):2285-2290
Lung carcinoids occur sporadically and rarely in association with multiple
endocrine neoplasia type 1 (MEN1). There are no well defined genetic
abnormalities known to occur in these tumors. We studied 11 sporadic lung
carcinoids for loss of heterozygosity (LOH) at the locus of the MEN1 gene
on chromosome 11q13, and for mutations of the MEN1 gene using dideoxy
fingerprinting. Additionally, a lung carcinoid from a MEN1 patient was
studied. In four of 11 (36%) sporadic tumors, both copies of the MEN1 gene
were inactivated. All four tumors showed the presence of a MEN1 gene
mutation and loss of the other allele. Observed mutations included a 1 bp
insertion, a 1 bp deletion, a 13 bp deletion and a single nucleotide
substitution affecting a donor splice site. Each mutation predicts
truncation or potentially complete loss of menin. The remaining seven
tumors showed neither the presence of a MEN1 gene mutation nor 11q13 LOH.
The tumor from the MEN1 patient showed LOH at chromosome 11q13 and a
complex germline MEN1 gene mutation. The data implicate the MEN1 gene in
the pathogenesis of sporadic lung carcinoids, representing the first
defined genetic alteration in these tumors.
相似文献
12.
1.5-T surface-coil MRI of the knee 总被引:1,自引:0,他引:1
D L Burk E Kanal J A Brunberg G F Johnstone H E Swensen G L Wolf 《AJR. American journal of roentgenology》1986,147(2):293-300
Five normal knees and 20 knees with suspected abnormalities involving the menisci or articular surfaces were examined with high-resolution surface-coil MRI. Surgical correlation was available in 15 cases. Signal-to-noise ratios were optimized using a field strength of 1.5 T and a round 7.6-cm surface coil. Spatial resolution was maximized by using fields of view reduced to as small as 8 cm. Separate examinations of the medial and lateral joint compartments were performed with the surface coil positioned vertically adjacent to the meniscus of interest. Ten meniscal tears were identified using sagittal and coronal images. T1-weighted images were adequate to detect most meniscal tears, and T2-weighted images were useful for providing an "arthrogram effect" in the presence of a joint effusion. Extrameniscal lesions that were examined included osteonecrosis of the femoral condyle, subchondral cysts, rheumatoid arthritis, degenerative arthritis, and anterior cruciate ligament tears. MRI was useful in determining the integrity of articular cartilage overlying defects in the subchondral bone and in detecting gross cartilage lesions in arthritis, but was less sensitive than arthroscopy in evaluating moderate changes in the hyaline cartilage. 相似文献
13.
The consideration for the choice of intracapsular lens-implantation are presented, and the surgical technique of the implantation of the new Binkhorst "all in the bag" lens is described in detail. 相似文献
14.
Burk U Selter H Zwergel T Wullich B Montenarh M Unteregger G 《International journal of oncology》1995,7(6):1355-1360
The growth suppressor protein p53 is abnormally expressed in a variety of different human tumor cells. We have analyzed the expression of p53 in cell cultures derived from tissues of radical prostatectomies and in the permanent prostate carcinoma cell line PC-3 using two different p53 specific monoclonal antibodies. With the wild-type specific monoclonal antibody PAb1620 we found p53 localized in nucleoli whereas only a few cells were positively stained in the nucleus with the mutant specific monoclonal antibody PAb240. Control experiments with p53 from SV80 cells which express wild-type p53 and HT29 cells expressing mutant p53 documented the specificity of the monoclonal antibodies. The specificity of the antibodies in recognizing indeed p53 was demonstrated further by immunoprecipitation analysis of p53 from the same cell cultures. Since p53 is usually localized to the nucleus our results may represent a specific feature of the wild-type phenotype of p53 in prostate carcinoma cells. The localization of p53 in nucleoli may be another mechanism of the inactivation of wild-type p53. 相似文献
15.
Burk RD 《Hospital practice (1995)》1999,34(12):103-11; quiz 112
Human papillomavirus (HPV) is now recognized as the driving force behind the dysregulation of the cell cycle that underlies cervical malignant transformation. Although nearly all cervical cancers contain HPV genomes, the vast majority of HPVs are not oncogenic but merely induce benign lesions. Because progressive abnormalities take at least a decade to develop into invasive cancers, young women with low-grade lesions can often be managed with watchful waiting rather than ablative therapy. 相似文献
16.
Raphael P Viscidi Mark Schiffman Allan Hildesheim Rolando Herrero Philip E Castle Maria C Bratti Ana Cecilia Rodriguez Mark E Sherman Sophia Wang Barbara Clayman Robert D Burk 《Cancer epidemiology, biomarkers & prevention》2004,13(2):324-327
Whether antibodies to human papillomavirus (HPV) capsids, elicited by natural infection, are protective is unknown. This question was addressed in a population-based cohort of 7046 women in Costa Rica by examining the association between baseline seroreactivity to HPV-16, HPV-18, or HPV-31 virus-like particles and the risk of subsequent HPV infection at a follow-up visit 5-7 years after enrollment. Seropositivity to HPV-16, HPV-18, or HPV-31 was not associated with a statistically significant decreased risk of infection with the homologous HPV type [relative risk (RR) and [95% confidence interval (CI)], 0.74 (0.45-1.2), 1.5 (0.83-2.7), and 0.94 (0.48-1.8), respectively]. Seropositivity to HPV-16 or HPV-31 was not associated with a decreased risk of infection with HPV-16 or its genetically related types [RR (95% CI), 0.82 (0.61-1.1) and 0.93 (0.68-1.2), respectively]. Seropositivity to HPV-18 was not associated with a decreased risk of infection with HPV-18 or its genetically related types (RR 1.3; 95% CI 1.0-1.8). Thus, we did not observe immunity, although a protective effect from natural infection cannot be excluded because of the limits of available assays and study designs. 相似文献
17.
Mitchell Maiman M.D. Rachel G. Fruchter Ph.D. Alexander Sedlis M.D. Joseph Feldman Dr.P.H. Patrick Chen M.D. Robert D. Burk M.D. Howard Minkoff M.D. 《Gynecologic oncology》1998,68(3):233-239
Objectives.The objective was to evaluate the sensitivity and specificity of cervical cytology in women infected with the human immunodeficiency virus (HIV), risk factors for abnormal cytology in HIV-infected and uninfected women, and risk factors for histologic diagnosis of cervical intraepithelial neoplasia (CIN) in HIV-infected women.Methods.Methods included a cross-sectional analysis of cervical cytology, colposcopic impression, and histology in 248 HIV-infected women and multivariate analyses of risk factors for abnormal cytology in 253 HIV-infected and 220 uninfected women and risk factors for CIN in 186 HIV-infected women.Results.The sensitivity and specificity of cytology for all CIN grades were 0.60 and 0.80 and, for high-grade CIN, 0.83 and 0.74. The prevalence of abnormal cytology was 32.9% in HIV-infected and 7.6% in HIV-negative women. Independent risk factors for abnormal cytology were immunodeficiency [odds ratio (OR) 8–17,P< 0.001] and human papillomavirus (HPV) infection (OR = 5,P< 0.001). The prevalence of CIN on histology was 32% in HIV-infected women, and the only independent risk factor for CIN was oncogenic HPV type (OR = 5,P= 0.005).Conclusion.Given the high prevalence of abnormal cytology and CIN in HIV-infected women, cytologic screening has significant limitations. Both immunodeficiency and type of HPV infection are important risk factors. 相似文献
18.
A prospective study of methylenetetrahydrofolate reductase and methionine synthase gene polymorphisms, and risk of colorectal adenoma 总被引:8,自引:2,他引:8
Chen J; Giovannucci E; Hankinson SE; Ma J; Willett WC; Spiegelman D; Kelsey KT; Hunter DJ 《Carcinogenesis》1998,19(12):2129-2132
We examined the relationship between a functional polymorphism (667C--
>T, ala-->val) of the methylenetetrahydrofolate reductase gene
(MTHFR) and the risk of colorectal adenomas in the prospective Nurses'
Health Study. Among 257 incident polyp cases and 713 controls, the MTHFR
val/val polymorphism [relative risk (RR) = 1.35, 95% confidence interval
(CI) 0.84-2.17] was not significantly associated with risk of adenomas.
This lack of association was observed for both small (RR = 1.36, 95% CI
0.76-2.45) and large (RR = 1.32, 95% CI 0.66-2.66) adenomas. Furthermore,
there was no significant interaction between this polymorphism and
consumption of either folate, methionine or alcohol. We also examined the
relationship of a newly identified polymorphism (asp919gly) of the
methionine synthase gene (MS) with the risk of colorectal adenomas in the
same population. The MS gly/gly polymorphism was also not significantly
associated with risk of colorectal adenomas (RR = 0.66, 95% CI 0.26-1.70).
These results, which need to be confirmed in other studies, suggest that
the MTHFR val/val polymorphism, which has been previously inversely
associated with risk of colorectal cancer, plays a role only in a late
stage (adenoma-- >carcinoma) of colorectal tumorigenesis, and/or may
protect against malignant transformation in the subset of benign adenomas,
which may progress to malignancy.
相似文献
19.
20.
Transforming growth factor beta (TGF-beta) is a bifunctional regulator of the growth of myeloid progenitors and is here demonstrated to directly inhibit the growth of primitive erythroid progenitors by 95% to 100% regardless of the cytokines stimulating growth. Autocrine TGF- beta production of primitive hematopoietic progenitors has previously been reported. In the present study, a neutralizing TGF-beta antibody (anti-TGF-beta) added to serum-containing cultures, resulted in a 3-, 4- , and 25-fold increase in burst-forming unit erythroid (BFU-E) colony formation in response to interleukin-4 (IL-4) plus erythropoietin (Epo), SCF plus Epo, and IL-11 plus Epo, respectively. The growth of BFU-E progenitors has been suggested to require a burst-promoting activity in addition to Epo. Accordingly, we observed no BFU-E colony formation in serum-containing cultures in response to Epo alone. In contrast, 50 BFU-E colonies were formed when anti-TGF-beta was included in the culture. In serum-free cultures, Epo also stimulated BFU-E colony formation in the absence of other cytokines, whereas anti-TGF- beta had no effect on the number of colonies formed. Quantitation of TGF-beta 1 in serum by an enzyme-linked immunosorbent assay method showed predominantly the presence of precursor (latent) TGF-beta 1, but also showed active TGF-beta 1 at a concentration sufficient to potently inhibit erythroid colony formation. Thus, neutralization of active TGF- beta 1 in serum shows that Epo alone is sufficient to stimulate the growth of murine BFU-E progenitors. 相似文献