全文获取类型
收费全文 | 10231篇 |
免费 | 627篇 |
国内免费 | 34篇 |
专业分类
耳鼻咽喉 | 121篇 |
儿科学 | 237篇 |
妇产科学 | 250篇 |
基础医学 | 1472篇 |
口腔科学 | 153篇 |
临床医学 | 935篇 |
内科学 | 2432篇 |
皮肤病学 | 216篇 |
神经病学 | 937篇 |
特种医学 | 231篇 |
外科学 | 1285篇 |
综合类 | 150篇 |
一般理论 | 12篇 |
预防医学 | 689篇 |
眼科学 | 235篇 |
药学 | 888篇 |
中国医学 | 27篇 |
肿瘤学 | 622篇 |
出版年
2023年 | 51篇 |
2022年 | 69篇 |
2021年 | 229篇 |
2020年 | 106篇 |
2019年 | 152篇 |
2018年 | 200篇 |
2017年 | 154篇 |
2016年 | 191篇 |
2015年 | 225篇 |
2014年 | 291篇 |
2013年 | 409篇 |
2012年 | 579篇 |
2011年 | 597篇 |
2010年 | 291篇 |
2009年 | 333篇 |
2008年 | 559篇 |
2007年 | 600篇 |
2006年 | 553篇 |
2005年 | 559篇 |
2004年 | 561篇 |
2003年 | 494篇 |
2002年 | 510篇 |
2001年 | 234篇 |
2000年 | 202篇 |
1999年 | 169篇 |
1998年 | 97篇 |
1997年 | 79篇 |
1996年 | 75篇 |
1995年 | 65篇 |
1994年 | 76篇 |
1993年 | 77篇 |
1992年 | 150篇 |
1991年 | 151篇 |
1990年 | 118篇 |
1989年 | 138篇 |
1988年 | 124篇 |
1987年 | 118篇 |
1986年 | 118篇 |
1985年 | 78篇 |
1984年 | 86篇 |
1983年 | 72篇 |
1982年 | 75篇 |
1981年 | 56篇 |
1980年 | 54篇 |
1979年 | 48篇 |
1978年 | 47篇 |
1977年 | 44篇 |
1976年 | 43篇 |
1975年 | 62篇 |
1971年 | 45篇 |
排序方式: 共有10000条查询结果,搜索用时 218 毫秒
91.
Stein D Kurtsman L Stier S Remnik Y Meged S Weizman A 《Journal of affective disorders》2004,82(3):335-342
BACKGROUND: The knowledge available on electroconvulsive therapy (ECT) in adolescents is largely anecdotal, or based on findings from adults. The aim of the present study is to compare the use of ECT in adolescent and adult inpatients. METHODS: We retrospectively analyzed the files of all 36 adolescent (between the ages of 13 and 19) and 57 randomly selected adult inpatients (above the age of 20) treated with ECT in a university-affiliated mental heath center in Israel between 1991 and 1997. RESULTS: Sixty one percent of the adolescents improved by the end of treatment, and 53% were not hospitalized in the subsequent year. The respective percentages among adults were 83% and 49%. Whereas most adults were treated with ECT because of schizophrenic disorders, almost half of the adolescents received ECT for affective disorders. Significantly more adolescents were treated with ECT because of acute life-endangering conditions (catatonia or severe suicidal risk). No significant adverse effects were found in both groups. LIMITATIONS: Our study is based on a retrospective chart review. The adolescent and adult groups are different in psychiatric morbidity, diagnosis and outcome, have not been assessed in a blind manner, and we have not used standardized psychometric batteries for the evaluation of ECT-related memory disturbances. CONCLUSIONS: ECT may be an effective, well-tolerated and safe procedure in both adult and adolescent inpatients. 相似文献
92.
Purification and characterization of placental heparanase and its expression by cultured cytotrophoblasts 总被引:9,自引:2,他引:9
Goshen Ran; Hochberg Abraham A.; Korner Gill; Levy Ehud; Ishai-Michaeli Rivka; Elkin Michael; de Groot Nathan; Vlodavsky Israel 《Molecular human reproduction》1996,2(9):679-684
The role of different extracellular matrix (ECM)-degrading enzymesin the normal functioning of the placenta is well documented.Heparan sulphate proteoglycan (HSPG) is an integral constituentof the placental and decidual ECM. Because this proteoglycanspecifically interacts with various macromolecules in the ECM,its degradation may disassemble the matrix. Hence, in the caseof the placenta, this may facilitate normal placentation andtrophoblast invasion. Crude placental specimens were collectedfrom first and third trimester placentas. Heparanase (endo-P-glucuronidase)was isolated and purified by ammonium sulphate precipitationfollowed by sequential chromatographies on carboxymethyl-, heparin-and ConA-Sepharose columns. The placental enzyme was furthercharacterized for its molecular weight and specific inhibitionby heparin, and was shown to resemble heparanase expressed byhighly metastatic tumour cells and activated cells of the immunesystem. In order to locate the source of heparanase activityin the placenta, primary cytotrophoblast cultures were established.Intact cells, as well as conditioned medium and cell lysates,were analysed for heparanase activity using metabolically sulphate-labelledECM as a natural substrate. Heparanase was highly active inlysates of cytotrophoblasts. This activity was also expressedby intact cytotrophoblasts seeded on ECM, but no activity couldbe detected in the culture medium. Incubation of the cytotrophoblastsin contact with ECM resulted in release of ECM-bound basic fibroblastgrowth factor (bFGF). We propose that the cytotrophoblasticheparanase facilitates placentation, through cytotrophoblastextravasation and localized neovascularization. cytotrophoblast/extracellular matrix/heparanase/heparan sulphate proteoglycan/placenta 相似文献
93.
A protein kinase A-dependent molecular switch in synapsins regulates neurite outgrowth 总被引:5,自引:0,他引:5
Kao HT Song HJ Porton B Ming GL Hoh J Abraham M Czernik AJ Pieribone VA Poo MM Greengard P 《Nature neuroscience》2002,5(5):431-437
Cyclic AMP (cAMP) promotes neurite outgrowth in a variety of neuronal cell lines through the activation of protein kinase A (PKA). We show here, using both Xenopus laevis embryonic neuronal culture and intact X. laevis embryos, that the nerve growth-promoting action of cAMP/PKA is mediated in part by the phosphorylation of synapsins at a single amino acid residue. Expression of a mutated form of synapsin that prevents phosphorylation at this site, or introduction of phospho-specific antibodies directed against this site, decreased basal and dibutyryl cAMP-stimulated neurite outgrowth. Expression of a mutation mimicking constitutive phosphorylation at this site increased neurite outgrowth, both under basal conditions and in the presence of a PKA inhibitor. These results provide a potential molecular approach for stimulating neuron regeneration, after injury and in neurodegenerative diseases. 相似文献
94.
Olaru A Mori Y Yin J Wang S Kimos MC Perry K Xu Y Sato F Selaru FM Deacu E Sterian A Shibata D Abraham JM Meltzer SJ 《Laboratory investigation; a journal of technical methods and pathology》2003,83(12):1867-1871
The activin type II receptorgene (ACTRII) is mutated in 58.1% of microsatellite-unstable (MSI-H) colorectal cancers and is a close relative of the TGFbeta-1 type II receptor, which is known to be involved in both MSI-H and non-MSI-H colorectal carcinogenesis. We therefore sought to determine whether ACTRII was involved in non-MSI-H colorectal cancers. We evaluated ACTRII inactivation by allelic deletion, loss of mRNA expression, or somatic mutation in 51 non-MSI-H colon cancers. Loss of heterozygosity (LOH) at the ACTRII locus (2q23.1) was found in 9 (17.6%) of 51 primary tumors. Loss of ACTRII mRNA expression was seen in one (14.3%) of the seven LOH-positive primary tumors from which total RNA was available. We also performed DNA sequencing analysis of tumors showing LOH. One LOH-positive primary tumor exhibited a novel germline missense sequence alteration (amino acid substitution, 117 Ile to Phe) that was not found in 23 additional normal individuals, implying that this alteration is not a frequent polymorphism. We conclude that ACTRII is probably involved in both non-MSI-H and MSI-H colorectal carcinogenesis, but more frequently in the latter subgroup. 相似文献
95.
Increased levels of endothelin-1 and differential endothelin type A and B receptor expression in scleroderma-associated fibrotic lung disease. 总被引:10,自引:0,他引:10
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)
D. J. Abraham R. Vancheeswaran M. R. Dashwood V. S. Rajkumar P. Pantelides S. W. Xu R. M. du Bois C. M. Black 《The American journal of pathology》1997,151(3):831-841
In addition to their vasoactive action, endothelins are potent peptides in the regulation of both cell proliferation and the turnover of extracellular matrix. Using immunohistochemical, autoradiographic, and molecular analyses, we have studied the localization and expression of endothelin-1 and endothelin A (ETA) and B (ETB) receptors in scleroderma-associated fibrotic lung disease. Increased ET-1 immunoreactivity was found in sclerotic tissue compared with control and was associated with the vasculature, pulmonary interstitium, and bronchial and alveolar epithelium. Microautoradiographic analysis after 125I-labeled ET-1 binding showed a two- to threefold increase in the expression of total ET-1 receptors in scleroderma lung tissue localized to the alveolar epithelium and the pulmonary interstitium which was composed of mainly fibroblastic cells with macrophages and some microvessels. RNAse protection assay revealed significantly reduced ETA receptor and slightly raised ETB message levels in systemic sclerosis lung. Surface expression of functional ET receptors was examined by targeted receptor blocking using mixed and receptor-subtype-selective ligands. A consistent decrease in ETA receptor binding sites was noted primarily within the interstitium and vasculature, in contrast to a slight increase in ETB receptors. Elevated ET-1 and the cell-specific pattern of endothelin receptor expression suggest that the endothelins may represent important mediators that influence the pathology of scleroderma-associated lung disease and other fibrotic conditions. 相似文献
96.
Reuvit Halperin Arie Herman Abraham Golan Eran Hadas David Schneider Ian Bukovsky Raphael Ron-El 《American journal of reproductive immunology (New York, N.Y. : 1989)》1996,35(2):102-105
PROBLEM: To examine the relationship between the concentration of uterine fluid human decidua-associated protein (hDP) 200, identified as a monoclonal rheumatoid factor, and different phases of the menstrual cycle. METHODS: Sequential measurements of hDP 200 concentration in uterine fluid were performed in 11 normal ovulatory women, aged 22–36 years. The samples were collected in early proliferative phase, late proliferative phase, periovulatory period, early secretory phase, and late secretory phase. RESULTS: Consistent fluctuations of hDP 200 levels in uterine fluid were found throughout the menstrual cycle. High levels were found during early proliferative phase and periovulatory period related to significantly lower levels during late proliferative and early luteal phases. CONCLUSION: There is menstrual phase dependent variation in the uterine fluid levels of hDP 200. 相似文献
97.
98.
99.
100.
The PapG tip adhesin of P fimbriae protects Escherichia coli from neutrophil bactericidal activity.
下载免费PDF全文
![点击此处可从《Infection and immunity》网站下载免费的PDF全文](/ch/ext_images/free.gif)
R Tewari T Ikeda R Malaviya J I MacGregor J R Little S J Hultgren S N Abraham 《Infection and immunity》1994,62(12):5296-5304
Compared with Escherichia coli ORN103, a nonfimbriated K-12 strain, P-fimbriated E. coli ORN103/pPAP5 was found to interact poorly with human neutrophils and resist their bactericidal activity in vitro. PapG, the Gal alpha(1-->4)Gal binding moiety located at the distal end of the P fimbrial filament, appeared to be responsible for this effect because an isogenic PapG- mutant, E. coli ORN103/pPAP24, exhibited binding interactions with neutrophils that were similar to nonfimbriated E. coli ORN103. Although no direct evidence is available, the poor adherence mediated by PapG could be related to its electrostatic properties because the isolated PapG protein had a pI of 5.2, which indicated that in the physiological pH range it possessed a net negative charge. Antibodies against PapG overcame the protective effect of PapG and markedly enhanced the interactions of P-fimbriated E. coli with neutrophils resulting in bacterial killing. When a P-fimbriated clinical E. coli strain or its isogenic PapG- derivative was injected into the peritoneal cavities of mice, a similar number of neutrophils was recruited to the site of injection. After 2 h, the number of P-fimbriated E. coli organisms that survived the neutrophil influx in the mouse peritoneum was approximately four times more than the number of surviving PapG- bacteria. This result demonstrates that the PapG protein, which is strategically located at the distal region of the P-fibrillum structure, protects E. coli from the bactericidal action of neutrophils. 相似文献