全文获取类型
收费全文 | 8799篇 |
免费 | 582篇 |
国内免费 | 28篇 |
专业分类
耳鼻咽喉 | 67篇 |
儿科学 | 354篇 |
妇产科学 | 237篇 |
基础医学 | 1384篇 |
口腔科学 | 126篇 |
临床医学 | 1258篇 |
内科学 | 1594篇 |
皮肤病学 | 158篇 |
神经病学 | 953篇 |
特种医学 | 203篇 |
外科学 | 717篇 |
综合类 | 45篇 |
一般理论 | 8篇 |
预防医学 | 836篇 |
眼科学 | 152篇 |
药学 | 525篇 |
中国医学 | 9篇 |
肿瘤学 | 783篇 |
出版年
2023年 | 78篇 |
2022年 | 81篇 |
2021年 | 201篇 |
2020年 | 150篇 |
2019年 | 219篇 |
2018年 | 264篇 |
2017年 | 182篇 |
2016年 | 232篇 |
2015年 | 233篇 |
2014年 | 315篇 |
2013年 | 467篇 |
2012年 | 663篇 |
2011年 | 654篇 |
2010年 | 360篇 |
2009年 | 316篇 |
2008年 | 640篇 |
2007年 | 608篇 |
2006年 | 566篇 |
2005年 | 593篇 |
2004年 | 513篇 |
2003年 | 456篇 |
2002年 | 436篇 |
2001年 | 77篇 |
2000年 | 42篇 |
1999年 | 63篇 |
1998年 | 98篇 |
1997年 | 82篇 |
1996年 | 67篇 |
1995年 | 70篇 |
1994年 | 52篇 |
1993年 | 50篇 |
1992年 | 23篇 |
1991年 | 32篇 |
1990年 | 28篇 |
1989年 | 27篇 |
1988年 | 23篇 |
1987年 | 16篇 |
1986年 | 30篇 |
1985年 | 29篇 |
1984年 | 30篇 |
1983年 | 26篇 |
1982年 | 21篇 |
1981年 | 37篇 |
1980年 | 25篇 |
1979年 | 15篇 |
1978年 | 19篇 |
1977年 | 12篇 |
1976年 | 17篇 |
1972年 | 10篇 |
1971年 | 11篇 |
排序方式: 共有9409条查询结果,搜索用时 0 毫秒
31.
32.
33.
Extracts of infective larvae and adults of the trichostrongylid Haemonchus contortus were studied for the presence of carbohydrate moieties. Several different lectin-binding sites were demonstrated in both stages using a panel of nine lectins. The carbohydrate specificity of the lectins used strongly suggests that α-D-mannose, α-D-glucose, and D-N-acetylglucosamine are the most important carbohydrate epitopes present on H. contortus proteins. Thus, N-linked oligosaccharides form the major part of the carbohydrate moieties on these glycoproteins. Treatment with sodium periodate was performed to investigate the immunoreactivity towards the carbohydrate moieties. This treatment resulted in a reduction in the immunoreactivity of these antigens as demonstrated by enzyme-linked immunosorbent assay (ELISA) and immunoblotting, suggesting that a substantial part of the host immune response against H. contortus is directed against the carbohydrate epitopes on the parasite antigens. 相似文献
34.
Tumor Vascularity Is Not a Prognostic Factor for Malignant Melanoma of the Skin 总被引:1,自引:4,他引:1
下载免费PDF全文
![点击此处可从《The American journal of pathology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Klaus J. Busam Marianne Berwick Karen Blessing Katrin Fandrey Sewon Kang Themis Karaoli Judy Fine Alistair J. Cochran Wain L. White Jason Rivers David E. Elder Duan-Ren Po Wen Bradley H. Heyman Raymond L. Barnhill 《The American journal of pathology》1995,147(4):1049-1056
Tumor vascularity has been proposed as a prognostic indicator for a number of solid tumors. Although a correlation between microvessel number and metastatic behavior has also been suggested for cutaneous melanoma, the small number of cases studied to date allows one to draw only preliminary conclusions. In this study, we have assessed tumor vascularity in cutaneous melanoma by comparing 60 cases of metastasizing and non-metastasizing tumors matched for tumor thickness, age, sex, and anatomic site. Ulex europaeus agglutinin I appeared to be the most suitable vascular marker for this study. Our results indicate that there was no statistically significant difference between the two groups with regard to tumor vascularity. Even after identifying 15 cases of thin (<1.0 mm thick) melanoma, there was no significant difference in the number of microvessels between metastasizing and non-metastasizing tumors. Comparison of patterns of vascular microarchitecture also failed to discriminate between the two groups. Thus, our results indicate that tumor vascularity may not be an independent prognostic factor for cutaneous melanoma. 相似文献
35.
We have developed a transient expression system for the protist Physarum polycephalum based on firefly luciferase. We demonstrate the utility of this system for comparing the activities of different promoters in Physarum amoebae, and also for detecting genetic elements that affect the level of gene expression. This system is likely to facilitate improvements in the stable transformation of this organism. 相似文献
36.
37.
Spök A Gaugitsch H Laffer S Pauli G Saito H Sampson H Sibanda E Thomas W van Hage M Valenta R 《International archives of allergy and immunology》2005,137(2):167-180
The prevalence of allergic diseases has been increasing continuously and, accordingly, there is a great desire to evaluate the allergenic potential of components in our daily environment (e.g., food). Although there is almost no scientific evidence that genetically modified organisms (GMOs) exhibit increased allergenicity compared with the corresponding wild type significant concerns have been raised regarding this matter. In principle, it is possible that the allergenic potential of GMOs may be increased due to the introduction of potential foreign allergens, to potentially upregulated expression of allergenic components caused by the modification of the wild type organism or to different means of exposure. According to the current practice, the proteins to be introduced into a GMO are evaluated for their physiochemical properties, sequence homology with known allergens and occasionally regarding their allergenic activity. We discuss why these current rules and procedures cannot predict or exclude the allergenicity of a given GMO with certainty. As an alternative we suggest to improve the current evaluation by an experimental comparison of the wild-type organism with the whole GMO regarding their potential to elicit reactions in allergic individuals and to induce de novo sensitizations. We also recommend that the suggested assessment procedures be equally applied to GMOs as well as to natural cultivars in order to establish effective measures for allergy prevention. 相似文献
38.
39.
Marianne Forsgren 《Archives of virology》1972,39(1-3):121-131
Summary Sera from 40 patients infected with poliovirus 1, 2 or 3 were surveyed for antibody activity against antigens of these viruses and echovirus 6 by immunodiffusion. Antibody activity common to the virion (N) antigens of two or three poliovirus types were encountered in a few sera; cross absorption tests confirmed the findings. The same sera also contained antibodies directed to one single type of N antigen, this was, however, not that of the infecting virus. Antibodies to echovirus 6 N was found only in one serum.Antibodies to empty capsid antigens (H) of polioviruses and echovirus 6 were demonstrable in the majority of sera; the occurrence of common antibodies to the H antigens of echovirus 6 and poliovirus H antigens was evident.The antibody patterns of different sera varied. Even early during the course of the disease heterologous anti H activity was associated with 7 S type antibodies, whereas the early homotypic anti N activity was present in the 19 S serum fraction. The data indicate that the heterologous antibody responses seem to represent booster responses from earlier experience with similar antigens.Antibodies of the 19 S and 7 S type showed precipitating activity whereas CF activity was found with certainty only in the 7 S fractions of sera. 相似文献
40.
A real-time PCR assay for detecting thermophilic Campylobacter spp. directly in chicken feces has been developed. DNA was isolated from fecal material by using magnetic beads followed by PCR with a prealiquoted PCR mixture, which had been stored at -18 degrees C. Campylobacter could be detected in less than 4 h, with a detection limit of 100 to 150 CFU/ml, in a fecal suspension. A bacterial internal control was added before DNA extraction to control both DNA isolation and the presence of PCR inhibitors in the samples. The assay was performed on 111 swab samples from a Danish surveillance program and compared to conventional culturing using selective enrichment. There was no statistically significant difference in performance between real-time PCR and culture by selective enrichment, and the diagnostic specificity was 0.96 with an agreement of 0.92. Therefore, the assay should be useful for screening poultry flocks for the presence of Campylobacter. 相似文献