全文获取类型
收费全文 | 162600篇 |
免费 | 15303篇 |
国内免费 | 8406篇 |
专业分类
耳鼻咽喉 | 1460篇 |
儿科学 | 2451篇 |
妇产科学 | 2490篇 |
基础医学 | 34419篇 |
口腔科学 | 4421篇 |
临床医学 | 12591篇 |
内科学 | 19444篇 |
皮肤病学 | 2711篇 |
神经病学 | 9909篇 |
特种医学 | 5331篇 |
外国民族医学 | 73篇 |
外科学 | 15907篇 |
综合类 | 25744篇 |
现状与发展 | 37篇 |
一般理论 | 2篇 |
预防医学 | 4595篇 |
眼科学 | 3429篇 |
药学 | 14607篇 |
61篇 | |
中国医学 | 5060篇 |
肿瘤学 | 21567篇 |
出版年
2024年 | 324篇 |
2023年 | 2020篇 |
2022年 | 4134篇 |
2021年 | 5708篇 |
2020年 | 5107篇 |
2019年 | 4448篇 |
2018年 | 4465篇 |
2017年 | 5262篇 |
2016年 | 6054篇 |
2015年 | 6644篇 |
2014年 | 10114篇 |
2013年 | 11758篇 |
2012年 | 9825篇 |
2011年 | 11066篇 |
2010年 | 8974篇 |
2009年 | 8765篇 |
2008年 | 8998篇 |
2007年 | 9123篇 |
2006年 | 8315篇 |
2005年 | 7227篇 |
2004年 | 6146篇 |
2003年 | 5067篇 |
2002年 | 4171篇 |
2001年 | 3615篇 |
2000年 | 3056篇 |
1999年 | 2682篇 |
1998年 | 2447篇 |
1997年 | 2283篇 |
1996年 | 2034篇 |
1995年 | 2000篇 |
1994年 | 1756篇 |
1993年 | 1481篇 |
1992年 | 1212篇 |
1991年 | 1103篇 |
1990年 | 918篇 |
1989年 | 898篇 |
1988年 | 794篇 |
1987年 | 704篇 |
1986年 | 587篇 |
1985年 | 865篇 |
1984年 | 775篇 |
1983年 | 529篇 |
1982年 | 662篇 |
1981年 | 510篇 |
1980年 | 417篇 |
1979年 | 372篇 |
1978年 | 261篇 |
1977年 | 196篇 |
1976年 | 176篇 |
1975年 | 65篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
82.
气管与主支气管肿瘤的影像诊断(附32例报告) 总被引:5,自引:1,他引:4
作者对32例经病理证实的气管与主支气管良、恶性肿瘤的影像学表现进行分析,归纳为3型:腔内型、壁增厚型和腔内外型。后2种类型提示恶性,而无蒂的腔内型表现者不能鉴别良,恶性。作者还评价了常规体层、CT及MRI诊断气管与主支气管肿瘤的优、缺点,讨论了影像诊断的作用。 相似文献
83.
Satoshi Abe 《Journal of orthopaedic science》1997,2(2):75-83
The purpose of this study was to validate the hypothesis of neural histogenesis of Ewing's sarcoma of bone and related tumors
by light microscopic, electron microscopic, and immunohistochemical analysis. We studied 32 round-cell sarcomas (19 cases
of Ewing's sarcoma of bone, 3 extraskeletal Ewing's sarcomas, 5 peripheral primitive neuroectodermal tumors (PNET) and 5 cases
of unclassified small round-cell type of neurogenic sarcoma (NS). Immunoreactivity for MIC2 was observed in all cases of Ewing's
sarcoma and PNET, and in 1 cases of NS. Positive immunoreactivity for neural markers (NSE, synaptophysin, S-100) was found
frequently in some tumors. Ultrastructurally, some specific features of neural differentiation, such as a fragmented basal
lamina and neurosecretory granule-like particles, were found even in typical cases of Ewing's sarcoma of bone, which presented
without a rosette arrangement and were almost negative for neural immuno-markers, but positive for MIC2. These ultrastructural
neural features were observed less frequently in Ewing's sarcoma of bone than in PNET and NS. However, no significant correlation
was demonstrated between the immunoreactivity for neural markers and the ultrastructural and histological neural features.
These results support the hypothesis of a neural origin of Ewing's sarcoma and related neoplasms, and suggest that some overlapping
entity could persist in PNET and Ewing's sarcoma and that this entity could be seen in histological and immunohistochemical
studies of both tumors. 相似文献
84.
G. W. McCAUGHAN C-L. SIAH C. ABBOTT J. WICKSON M. BALLESTEROS G. A. BISHOP 《Journal of gastroenterology and hepatology》1993,8(2):142-145
Dipeptidyl peptidase IV (DPP-IV) is a cell surface ectopeptidase that has been implicated in cell-extracellular matrix interactions, lymphocyte growth and the regulation of biological peptides. Previous studies have shown that immunostaining for DPP-IV and DPP-IV enzyme levels is decreased in hepatoma cells and levels have been correlated with the ability of such cells to adhere in vitro. The aim of this paper was to measure DPP-IV enzyme levels in rat hepatoma cells and to examine whether changes were associated with alterations at the mRNA level. The results indicate a greater than 90% reduction in DPP-IV enzyme levels in two rat hepatoma cell lines, HTC and H35, compared with rat hepatocytes. Enzyme levels of the control enzyme leucine aminopeptidase (LAP) were not decreased. mRNA studies indicated that these changes were associated with similar reductions in rat DPP-IV mRNA. It is concluded that DPP-IV is markedly reduced at the protein, enzyme and mRNA levels in rat hepatoma cells. The significance of these changes is unclear but may lead to decreased extracellular matrix interactions by such cells. 相似文献
85.
C. L. R. BARRATT P. E. HARRISON A. ROBINSON I. D. COOKE 《International journal of andrology》1990,13(1):50-58
The significance of white blood cells in the ejaculate remains a matter of controversy. Several authors have suggested that such cells are important in the modulation of an antisperm antibody response, i.e. a predominance of suppressor/cytotoxic to helper/inducer T cells may prevent the development of antisperm antibodies. In order to examine this relationship further we have documented the white blood cell types, with emphasis on the T-lymphocyte populations, in the ejaculates of men from infertile couples with and without antisperm antibodies; the latter group was divided further into two groups--vasovasostomized men and idiopathic men. All seven of the men without antisperm antibodies had a predominance of suppressor/cytotoxic T cells to helper/inducer T cells in the ejaculate. However, only in some of the men with antibodies was there a predominance of T-helper/inducer cells. It is clear that the relationship between antisperm antibodies and seminal leucocytes is therefore not as straightforward as has been proposed. 相似文献
86.
Katalin Vehmeyer Tibor Hajto Katarina Hostanska Stefan Knemann Holger Lser Reinhard Saller Bernhard Wrmann 《European journal of haematology》1998,60(1):16-20
Abstract: The galactoside-specific plant lectin, Viscum album agglutinin (VAA-I) increases cellular parameters of natural host defence. It also binds to a variety of haematopoietic cells, including progenitors. We investigated whether VAA-I has a stimulatory effect on haematopoietic progenitor cells. Peripheral blood progenitor cells from 7 healthy volunteers were cultured in a colony assay with VAA-I plus erythropoietin (EPO) and stem cell factor (SCF). At 50 pg/ml VAA-I induced a significant increase in the cytokine-dependent clonogenic growth (52% in median, p<0.05). In another set of experiments purified CD34+ cells were isolated from the bone marrow aspirate of 4 patients with non-metastatic breast cancer using fluorescence-activated cell sorting. Binding to CD34+ cells was demonstrated by using directly fluorescence-conjugated VAA-I. Co-incubation with d -galactose significantly abrogated this effect. CD34+ cells were cultured in the presence of EPO, SCF, interleukin-3, granulocyte/monocyte colony-stimulating factor and granulocyte colony-stimulating factor. VAA-I alone had no measurable effect on the clonogenic growth of the isolated cells. However, at concentrations of 100 and 250 pg/ml VAA-I increased the cytokine-dependent proliferation and differentiation of CD34+ cells by a median of 75 and 85%, respectively. The results show that VAA-I binds to haematopoietic progenitor cells and has a co-stimulatory effect on their proliferation. 相似文献
87.
用限制性内切酶EcoRI从pKS(-)HTH_1切下全长为1.9 kb的人酪氨酸羟化酶基因,在T_4DNA连接酶的作用下连接在真核表达载体pCDNA_3的EcoR Ⅰ位点,构建成重组质粒pcD-NA_3HTH_1,该质粒转染COS-7细胞,免疫荧光组织化学染色证实酪氨酸羟化酶在其中的表达。 相似文献
88.
Summary With the use of duplex Doppler ultrasound and color Doppler flow imaging(CDFI), the characteristics of blood supply in neoplasma
were studied in 51 cases of 60 liver tumors, and compared with the results of surgery, pathological examination and hepatic
anerial angiography. The result showed that: 1. Doppler blood flow signals could be detected in all hepatic carcinomas, and
in 10 cases of 18 hemangiomas, significant difference was observed (P<0.001); 2. Doppler blood flow spectra showed pulsatile pattern in 41 of 42 hepatic carcinomas, and in 6 of 10 hemangiomas
(P<0.01); and 3. the peak flow velocity was obviously lower in hemangioma group than in hepatic carcinoma group (20.34±23.93
vs 64.74±30.18 cm,P<0.001). The characteristics of CDFI show that hemangiomas and hepatocellular carcinomas are different. It can, therefore,
be concluded that the blood supply of hepatic carcinomas mainly comes from hepatic arterial system, and is of value in duplex
Doppler ultrasound and CDFI. 相似文献
89.
Klaus Edvardsen Nils Brünner Mogens Spang-Thomsen Frank S. Walsh Elisabeth Bock 《International journal of developmental neuroscience》1993,11(5)
A cDNA encoding a transmembrane 140 kDa isoform of the neural cell adhesion molecule, NCAM, was transfected into the rat glioma cell line BT4Cn. Transfectants with a homogeneously high expression of NCAM-B showed a decreased capacity for penetration of an artificial basement membrane when compared to cells transfected with expression-vector alone or untransfected cells. However, when injected subcutaneously into nude mice, both NCAM expressing cells and control cells produced invasive tumors. Nude mice injected with NCAM positive cells developed tumors with slower growth rates as compared to those induced by NCAM negative cells. This implies that NCAM may not only be involved in adhesive and motile behaviour of glioma cells, but also in their growth regulation. 相似文献
90.
Eileen J. Martin Kiran S. Panickar Michael A. King Malgorzata Deyrup Bruce E. Hunter Geehuan Wang Edwin M. Meyer 《Drug development research》1994,31(2):135-141
The potential cytoprotective actions of a novel nicotinic agent 2,4-dimethoxybenzilidene anabaseine (DMXB) were investigated in differentiated PC12 cells and transected rat septal cholinergic neurons in vivo. In NGF-differentiated PC12 cells, removal of both NGF and serum led to cell loss, a reduced % of cells expressing neurites, the release of lactate dehydrogenase, and a decrease in total cellular protein. Cell loss was apparent within 24 h, and remained constant between 4–8 days post-NGF removal. NGF alone (100 ng/ml), DMXB (10 μM), but not nicotine (10 μM), prevented these cell and neurite losses. DMXB-induced cytoprotection was blocked by 1 μM mecamylamine. DMXB (1 mg/kg, ip) injected twice but not once per day protected cholinesterase-staining septal neurons from retrograde degeneration following unilateral fimbrial transections. The twice per day DMXB injection-protocol also decreased cell roundness among cholinesterase-staining cells in the lesioned septal hemisphere compared to saline-injected animals. These studies suggest that DMXB may exert cytoprotective activity in NGF-sensitive neuronal populations. © 1994 Wiley-Liss, Inc. 相似文献