全文获取类型
收费全文 | 1833篇 |
免费 | 175篇 |
国内免费 | 10篇 |
专业分类
耳鼻咽喉 | 8篇 |
儿科学 | 81篇 |
妇产科学 | 42篇 |
基础医学 | 216篇 |
口腔科学 | 30篇 |
临床医学 | 187篇 |
内科学 | 334篇 |
皮肤病学 | 18篇 |
神经病学 | 142篇 |
特种医学 | 193篇 |
外科学 | 293篇 |
综合类 | 29篇 |
预防医学 | 179篇 |
眼科学 | 32篇 |
药学 | 98篇 |
中国医学 | 2篇 |
肿瘤学 | 134篇 |
出版年
2021年 | 24篇 |
2020年 | 14篇 |
2019年 | 20篇 |
2018年 | 23篇 |
2017年 | 20篇 |
2016年 | 23篇 |
2015年 | 34篇 |
2014年 | 45篇 |
2013年 | 46篇 |
2012年 | 72篇 |
2011年 | 62篇 |
2010年 | 49篇 |
2009年 | 40篇 |
2008年 | 72篇 |
2007年 | 82篇 |
2006年 | 66篇 |
2005年 | 78篇 |
2004年 | 62篇 |
2003年 | 43篇 |
2002年 | 48篇 |
2001年 | 43篇 |
2000年 | 41篇 |
1999年 | 46篇 |
1998年 | 53篇 |
1997年 | 75篇 |
1996年 | 54篇 |
1995年 | 43篇 |
1994年 | 47篇 |
1993年 | 34篇 |
1992年 | 38篇 |
1991年 | 45篇 |
1990年 | 28篇 |
1989年 | 49篇 |
1988年 | 41篇 |
1987年 | 32篇 |
1986年 | 41篇 |
1985年 | 39篇 |
1984年 | 28篇 |
1983年 | 21篇 |
1982年 | 19篇 |
1981年 | 20篇 |
1980年 | 19篇 |
1979年 | 20篇 |
1978年 | 19篇 |
1977年 | 19篇 |
1976年 | 18篇 |
1975年 | 15篇 |
1974年 | 21篇 |
1973年 | 19篇 |
1972年 | 16篇 |
排序方式: 共有2018条查询结果,搜索用时 31 毫秒
21.
Optic nerve pseudomeningioma secondary to localized amyloidosis 总被引:1,自引:0,他引:1
A 55-year-old woman presented with a mass of the optic nerve sheath suggestive of a meningioma. On excision, this proved to be amyloid. No systemic involvement could be found. Although amyloid may arise as a solitary lesion of the orbit or extraocular muscle, this "pseudomeningiomatous" pattern has not been previously noted. A magnetic resonance scan was helpful because the amyloid imaged at a density similar to vitreous and cerebral white matter, unlike meningiomas, which appear more like bone. The diagnosis of localized amyloidosis, however, still remains dependent on histopathology and cannot be made on a clinical basis. 相似文献
22.
23.
Lymphotoxin but not tumor necrosis factor functions to maintain splenic architecture and humoral responsiveness in adult mice 总被引:1,自引:0,他引:1
Fabienne Mackay Gerard R. Majeau Pornsri Lawton Paula S. Hochman Jeffrey L. Browning 《European journal of immunology》1997,27(8):2033-2042
To compare the function of the tumor necrosis factor (TNF) and lymphotoxin (LT)α/β systems in the mature immune system, these two pathways were blocked with soluble receptor-immunoglobulin (R-Ig) fusion proteins in normal adult mice. Inhibition of LTα/β signaling using LTβR-Ig or a blocking monoclonal antibody against murine LTβ had profound effects. The spleen lacked discrete B cell follicles and the marginal zone was altered. Less marked changes were detected in lymph nodes. LTα/β inhibition also prevented germinal center formation in the spleen and impaired Ig production in response to sheep red blood cells (SRBC) immunization. These results show that the LTα/β system is required for the maintenance of splenic architecture and normal immune responses, and not simply for the development of peripheral immune organs during ontogeny. In contrast, inhibition of the TNF/LTα pathway with TNF-R55-Ig did not affect the splenic architecture or the anti-SRBC response. Splenic defects and impaired antibody responses are seen in TNF-deficient mice, suggesting that TNF is important during development. Therefore relative to TNF, the LT system has the dominant influence on splenic organization and anti-SRBC Ig formation in the adult mouse. 相似文献
24.
Differential expression of E-cadherin in lobular and ductal neoplasms of the breast and its biologic and diagnostic implications 总被引:7,自引:0,他引:7
Acs G Lawton TJ Rebbeck TR LiVolsi VA Zhang PJ 《American journal of clinical pathology》2001,115(1):85-98
We studied the pattern of E-cadherin expression in 183 invasive carcinomas (100 ductal, 42 lobular, 41 with mixed ductal and lobular features) and 198 in situ carcinomas (131 ductal, 53 lobular, 14 in situ with ductal and lobular features) by immunohistochemistry. We found a highly significant correlation of E-cadherin membrane expression with the histologic phenotype of the tumors. While moderate to strong membrane expression of E-cadherin was seen in all invasive and in situ ductal carcinomas, 41 of 42 invasive and 50 of 53 in situ lobular carcinomas showed complete loss of expression. All in situ carcinomas diagnosed histologically as showing mixed ductal and lobular features demonstrated complete loss of staining. Invasive carcinomas with ductal and lobular features showed 3 staining patterns: (1) complete or almost complete lack of membrane staining similar to that seen in lobular carcinomas, (2) uniform membrane expression throughout the tumor similar to ductal carcinomas, and (3) focal loss of E-cadherin staining, which correlated well with the histologic impression of focal lobular features. In tumors with histologically equivocal features, immunohistochemical detection of E-cadherin expression can be a useful diagnostic tool for the differentiation of ductal and lobular carcinomas of the breast. 相似文献
25.
26.
27.
Aberrant chromatin at genes encoding stem cell regulators in human mixed-lineage leukemia 总被引:1,自引:0,他引:1
Matthew G. Guenther Lee N. Lawton Tatiana Rozovskaia Garrett M. Frampton Stuart S. Levine Thomas L. Volkert Carlo M. Croce Tatsuya Nakamura Eli Canaani Richard A. Young 《Genes & development》2008,22(24):3403-3408
Mixed-lineage leukemia (MLL) fusion proteins are potent inducers of leukemia, but how these proteins generate aberrant gene expression programs is poorly understood. Here we show that the MLL-AF4 fusion protein occupies developmental regulatory genes important for hematopoietic stem cell identity and self-renewal in human leukemia cells. These MLL-AF4-bound regions have grossly altered chromatin structure, with histone modifications catalyzed by trithorax group proteins and DOT1 extending across large domains. Our results define direct targets of the MLL fusion protein, reveal the global role of epigenetic misregulation in leukemia, and identify new targets for therapeutic intervention in cancer. 相似文献
28.
29.
A 63-year-old man with iron loss anaemia and hypercalcaemia was found to have a renal cell carcinoma. Despite the iron-deficient blood and bone marrow picture, the serum ferritin concentration was markedly raised. This was mainly due to a “basic isoferritin”. The serum parathormone concentration was normal. The serum ferritin and calcium concentrations returned to normal after the tumour was removed. We propose that the renal cell carcinoma cells in this patient secreted the basic isoferritin as well as humoral factor(s) responsible for hypercalcaemia. 相似文献
30.
Gene conversion is a likely cause of mutation in PKD1 总被引:3,自引:0,他引:3
Watnick TJ; Gandolph MA; Weber H; Neumann HP; Germino GG 《Human molecular genetics》1998,7(8):1239-1243
Approximately 70% of the gene responsible for the most common form of
autosomal dominant polycystic kidney disease ( PKD1 ) is replicated in
several highly homologous copies located more proximally on chromosome 16.
We recently have described a novel technique for mutation detection in the
duplicated region of PKD1 that circumvents the difficulties posed by these
homologs. We have used this method to identify two patients with a nearly
identical cluster of base pair substitutions in exon 23. Since pseudogenes
are known to be reservoirs for mutation via gene conversion events for a
number of other diseases, we decided to test whether these sequence
differences in PKD1 could have arisen as a result of this mechanism. Using
changes in restriction digest patterns, we were able to show that these
sequence substitutions are also present in N23HA, a rodent-human somatic
cell hybrid that contains only the PKD1 homologs. Moreover, these changes
were also detected in total DNA from several affected and unaffected
individuals that did not harbor this mutation in their PKD1 gene copy. This
is the first example of gene conversion in PKD1 , and our findings
highlight the importance of using gene-specific reagents in defining PKD1
mutations.
相似文献