全文获取类型
收费全文 | 4867篇 |
免费 | 598篇 |
国内免费 | 76篇 |
专业分类
耳鼻咽喉 | 31篇 |
儿科学 | 84篇 |
妇产科学 | 88篇 |
基础医学 | 721篇 |
口腔科学 | 130篇 |
临床医学 | 622篇 |
内科学 | 453篇 |
皮肤病学 | 55篇 |
神经病学 | 238篇 |
特种医学 | 89篇 |
外科学 | 574篇 |
综合类 | 611篇 |
预防医学 | 688篇 |
眼科学 | 39篇 |
药学 | 605篇 |
19篇 | |
中国医学 | 318篇 |
肿瘤学 | 176篇 |
出版年
2024年 | 9篇 |
2023年 | 76篇 |
2022年 | 150篇 |
2021年 | 222篇 |
2020年 | 203篇 |
2019年 | 196篇 |
2018年 | 231篇 |
2017年 | 234篇 |
2016年 | 180篇 |
2015年 | 177篇 |
2014年 | 339篇 |
2013年 | 386篇 |
2012年 | 290篇 |
2011年 | 282篇 |
2010年 | 227篇 |
2009年 | 197篇 |
2008年 | 178篇 |
2007年 | 208篇 |
2006年 | 192篇 |
2005年 | 180篇 |
2004年 | 139篇 |
2003年 | 134篇 |
2002年 | 111篇 |
2001年 | 76篇 |
2000年 | 52篇 |
1999年 | 47篇 |
1998年 | 45篇 |
1997年 | 61篇 |
1996年 | 44篇 |
1995年 | 52篇 |
1994年 | 48篇 |
1993年 | 46篇 |
1992年 | 43篇 |
1991年 | 39篇 |
1990年 | 38篇 |
1989年 | 23篇 |
1988年 | 24篇 |
1987年 | 26篇 |
1986年 | 29篇 |
1985年 | 55篇 |
1984年 | 55篇 |
1983年 | 40篇 |
1982年 | 44篇 |
1981年 | 47篇 |
1980年 | 24篇 |
1979年 | 14篇 |
1978年 | 10篇 |
1977年 | 7篇 |
1976年 | 7篇 |
1975年 | 2篇 |
排序方式: 共有5541条查询结果,搜索用时 187 毫秒
61.
Walid A. Mourad Nour Sneige Ruth L. Katz Nancy P. Caraway Tina V. Fanning 《Diagnostic cytopathology》1994,11(4):328-332
We report the cytological and clinical findings of 16 fine-needle aspirates (FNAs) performed on recurrent (n = 6) and metastatic (n = 10) mixed mesodermal tumors (MMMTs). The median interval between the primary diagnosis and FNA was 16 mo. Primary sites were the endometrium (n = 11), the ovary (n = 3), the cervix (n = 1), and pelvic soft tissue (n = 1). Primary tumors showed carcinoma with homologous mesenchymal components in 13 cases and focal heterologous elements in three (two chondrosarcomas and one rhabdomyosarcoma). The FNAs showed carcinoma in all 16 cases, with adenocarcinoma differentiation in three, Mesenchymal elements were identified in aspirates of three recurrent and two metastatic lesions. They were all homologous. No heterologous mesenchymal elements were identified in the aspirates. We conclude that mesenchymal components in FNAs of MMMTs are less likely to be seen in metastatic lesions, and that heterologous mesenchymal components are rarely seen in these aspirates even in recurrent disease. These findings confirm that the epithelial component is responsible for the malignant behavior of MMMTs, and suggest that these lesions may need to be classified as sarcomatoid carcinomas rather than true carcinosarcomas. Diagn Cytopathol 1994;11:328–332. © 1994 Wiley-Liss, Inc. 相似文献
62.
Malignant mixed Müllerian tumor is a rare neoplasm that occurs most frequently in elderly patients. It is characterized by a mixture of malignant epithelial and sarcomatous components. Little has been published about Papanicolaou smear findings pertaining to malignant mixed Müllerian tumors. We present our experience, with an emphasis on cytologic detail. Nine patients (median age, 65 yr) met our study criteria. All available smears and surgical specimens were reviewed. Four smears were positive for malignancy, with a sensitivity of 44% (3 adenocarcinoma, and 1 squamous-cell carcinoma, small-cell type). The results of our study showed that Papanicolaou smear findings pertaining to malignant mixed Müllerian tumors are seen in patients with advanced-stage disease with involvement of the lower uterine segment or cervix. The usual finding is large numbers of high-grade epithelial malignant cells in a necrotic background. The mesenchymal component rarely sheds cells visible on Papanicolaou smear. 相似文献
63.
Chen J He Q Zhang R Chu Y Wang Y Liu Q Xiong S 《Clinical and experimental immunology》2004,138(2):245-250
The interaction of T cell CD28/CTLA-4 receptors with B7 on antigen-presenting cells (APCs) represents an important co-stimulatory pathway in T cell activation or anergy. Our previous study indicated that recipients immunized with allogenic donor immature dendritic cells (DCs) or resting B cells could induce specific immune tolerance and prolong allograft survival. A possible mechanism for this observation is that the expression of B7 molecules is either at a low level or lacking on these cells. The present study investigates whether blockade of B7 molecules on donor splenocytes with a B7 antisense peptide (B7AP), i.e. a peptide analogue of the CD28-binding region, could induce specific immune tolerance and prolong allograft survival in the recipients. Both the lymphocyte proliferation reaction and the mice pinna cardiac allograft experiment were performed to evaluate the role of B7AP in inducing specific immune tolerance in recipients in vitro and in vivo. The results showed that 56.65% and 20.52% of C57BL/6 splenocytes expressed B7.1 and B7.2 molecules, respectively, on their cell surface. There were no significant changes of the B7 expression on such splenocytes after being treated by the B7AP (53.28% and 19.06%, respectively). B7AP inhibited the mixed lymphocyte reaction by up to 38.4% and a dose-response correlation was observed for inhibition. The recipients (BALB/c) immunized with B7AP-pretreated C57BL/6 splenocytes induced a specific immune hypo-response (43%versus control) and notably prolonged survival of the C57BL/6 cardiac allograft by up to 20.3 days. In contrast to the normal saline group (average: 8.6 days) and FTD(10) control peptide group (<4 days), the cardiac allograft survival of the test group was extended for an additional 11.7 days. These results strongly support the notion that immunization with donor splenocytes, which had been pretreated with B7AP, induced specific immune tolerance and prolonged allograft survival in the recipients. 相似文献
64.
Pavlik LL Bezgina EN Dzeban DA Moshkov DA 《Neuroscience and behavioral physiology》2005,35(5):453-456
The pyroantimonate method was used to study the distribution of calcium ions in the mixed synapses of Mauthner neurons after exposure to substances altering the electrotonic conductivity of these synapses mediated by gap junctions (GJ). Ecdysone, an agent which increases GJ conductivity, produced precipitates of calcium pyroantimonate coating the whole postsynaptic surface of the GJ area, making them strongly asymmetrical. Precipitate granules were also seen to appear in the clefts of desmosome-like contacts (DLC). Chlorpromazine, which decreases GJ conductivity, produced precipitates in GJ clefts and on the pre- and postsynaptic membranes. No precipitate formed in DLC clefts. These results demonstrate that ecdysone acts as an agent selectively increasing GJ conductivity without affecting DLC function. Chlorpromazine had a double action, blocking conduction through both GJ and DLC. Thus, studies of agents altering GJ permeability require consideration of the possibility that they may interact with actin-containing structures also involved in the transport of the electrotonic signal.Translated from Morfologiya, Vol. 125, No. 3, pp. 32–35, May–June, 2004. 相似文献
65.
Paloma E Coco R Martínez-Mir A Vilageliu L Balcells S Gonzàlez-Duarte R 《Human mutation》2002,20(6):476-476
Genotype-phenotype correlations highlighted the function of ABCA4 in retinitis pigmentosa (RP),cone-rod dystrophy (CRD) and Stargardt/Fundus Flavimaculatus disease (STGD/FFM). Initial screening of ABCA4 variants showed a correlation between the type of mutation and the severity of the disease. In the present study we have undertaken mutational and haplotype analysis of ABCA4 in three mixed pedigrees segregating different retinal dystrophies. In family I, we have shown cosegregation of different ABCA4 alleles with CRD (homozygosity for L1940P) and three subtypes of STGD/FFM. The first, a mild form, consisting on fundus flavimaculatus-like distribution of flecks, but good visual acuity and absence of dark choroid, was found to cosegregate with alleles R1097C and F553L; the second, a conventional Stargardt phenotype was associated to alleles L1940P/R1097C and the third, displaying severely reduced visual acuity and dark choroid (named FFM), was associated to L1940P/F553L. In family II, segregating STGD and RP phenotypes, while the involvement of ABCA4 in STGD seems clear this is not the case for RP. Finally, in family III, also segregating STGD and RP, ABCA4 fails to explain either phenotype. Our data highlight the wide allelic heterogeneity involving this gene and support the genetic variability (beyond ABCA4) of mixed STGD/RP pedigrees. 相似文献
66.
Animal or human blood protein is a costly but necessary additive to tissue culture. This supplemental protein is provided by the addition of pooled serum or heparinized plasma to standard tissue culture media. Many blood centers store CPDA-1 anticoagulated plasma, a form that does not provide optimal support of mixed lymphocyte culture (MLC). The optimal amount of CaCl2 (1 ml of 1 M CaCl2/100 g) added to citrate plasma and the use of glass vessels result in a completely clotted product that is comparable in MLC support to commercially available pooled human serum. Laboratories that have access to CPDA-1 plasma can replace the growing demand for serum with recalcified plasma without sacrificing quality. 相似文献
67.
Mixed Epithelial and Stromal Tumor of the Kidney: Preliminary Immunohistochemical and Electron Microscopic Studies of the Epithelial Component 总被引:2,自引:0,他引:2
Mixed epithelial and stromal tumor of the kidney is a rare biphasic tumor composed of cysts and tubules embedded in the spindle cell stroma. Although the histogenesis of this tumor is unknown, it has been proposed that both components of the tumor, i.e., stromal and epithelial, are neoplastic. The authors report preliminary immunohistochemical and electron microscopic studies of the epithelial component from one case of a typical, benign, mixed epithelial, and stromal tumor of the kidney. In this study, some tubules showed positivity for proximal, while others showed positivity for distal, nephron immunomarkers. By electron microscopy, some tubules had features of proximal tubular epithelium, while other tubules had features of the loop of Henle (thin segments). The authors believe that in a benign tumor such morphologic heterogeneity is inconsistent with neoplastic proliferation. Therefore, they postulate that in mixed epithelial and stromal tumor of the kidney the tubules are entrapped rather than neoplastic. Additional studies are needed to address this issue and electron microscopy should play a significant role in this process. 相似文献
68.
Direct estimation of the frequency of human cytotoxic T lymphocytes and their precursors following in vitro allosensitization 总被引:2,自引:0,他引:2
Cell mediated lympholysis (CML) has been proposed as an in vitro model of the rejection process that results from transplantation of allogeneic tissue. To date, the absolute frequencies of cytotoxic T lymphocytes (CTL) and their precursors (CTL.P) have not been directly estimated in man because of technical difficulties. Through optimizing the conditions for radiometric detection of 51Cr release and the attendant improvement in CML sensitivity, direct CTL frequency estimates have been determined in peripheral blood (PBL), spleen (SPL), and lymph nodes (LNC) after in vitro allostimulation using unrelated human cells and limiting dilution assays. The mean frequency of CTL generated from PBL is 1 in 826 cells (0.121% +/- 0.101%) which, from preliminary experiments, is significantly greater than that generated from either LNC or SPL (p less than 0.05). With restimulation of primed cells on day 10, the frequency of CTL generated from PBL was increased 400%. The CTL.P frequency (0.0064% +/- 0.0050%) was approximately 5% of the corresponding CTL frequency. The CTL.P frequencies were found to be minimal estimates as both accessory "filler" cells and T cell growth factors increased the level of detection of CTL.P an average of threefold. The limiting cell dilution assay as detailed in this report should be a powerful tool for defining the cellular requirements and related factors necessary for optimal induction of a CTL response and should provide the means for determination of the immunogenetic requirements and the allospecificity of human cytotoxic lymphocytes. 相似文献
69.
Evidence for the involvement of HLA-DR antigens in restricted cytotoxicity by fetal calf serum-specific human T cells 总被引:1,自引:0,他引:1
Fetal calf serum (FCS) generated at least two distinct populations of human cytotoxic cells in vitro. One population expressed natural killer (NK) cell-like activity and lysed K562 and HSB-2 targets more effectively than autologous or allogeneic lymphoblastoid cell lines (LCLs). The other population contained FCS-specific cytotoxic T cells which preferentially lysed the autologous LCLs and showed minimal lysis of K562. E-rosette separation and cold target competition experiments clearly established that NK cells were not involved in the self-reactive lysis. Moreover, the lytic activity of the E-rosetted T cells was reduced by up to 95% when autologous target cells were grown in human AB serum rather than FCS, showing that FCS-associated determinants on targets were essential in the cytolytic phase. Autologous LCLs grown in FCS were also considerably stronger competitors than human serum-grown LCLs. The consistent self-preferred lysis suggested that HLA antigen-related restriction was involved, but the patterns of lysis did not implicate HLA-A or B antigens, and monoclonal antibody (W6/32) to an A, B, and C monomorphic determinant failed to block FCS-specific lysis. In contrast, monoclonal antibody (DA.2) to a monomorphic determinant of DR effectively blocked FCS-specific lysis. Cytotoxicity tests with a small panel of DR-typed donors indicated that strong cross-reactions were invariably associated with sharing of DR antigens, particularly DR2, and to a lesser but significant extent DR7. Although DR antigen sharing did not always result in lysis of allogeneic targets, the overall evidence strongly suggests that FCS-specific T-cell cytotoxicity in humans is restricted by products encoded by or associated with the DR genes. 相似文献
70.
Gordon B. Strom Richard N. Boswell Robert L. Jacobs 《The Journal of allergy and clinical immunology》1983,72(1):46-53
Thirty-four patients with a history of immediate hypersensitivity to the sting of the imported fire ant were evaluated in a study designed to compare the diagnostic usefulness of fire ant whole body extract (WBE) preparations with that of fire ant venom (IFAV). Ninety-one percent () of the hypersensitive patients skin tested with IFAV at a maximal concentration of 1:5 × 103, , demonstrated a wheat equal to or greater than the histamine control. Fifty-three percent () of the group were skin test positive to a WBE preparation. When the criteria for a positive skin test were relaxed, 82% of the hypersensitive group could be identified with the IFAWBE. A comparison of skin test results in sensitive patients revealed variability in the sensitivity of the WBE preparations utilized in the study. Leukocyte histamine release demonstrated a dose-response release of histamine with both IFAV and SIWBEa preparations. Specific venom antisera produced in rabbits identified a precipitin line of common identity in a gel-diffusion system containing IFAWBE and IFAV. This finding was verified by the competitive inhibition of IFAWBE with IFAV in a solid-phase radioimmunoassay system. Fire ant WBEs contain venom constituents and are effective diagnostic agents in up to 82% of patients with hypersensitivity to the sting of the imported fire ant. Marked variability in the responsiveness of sensitive patients to different WBE preparations mandates standardization of these diagnostic preparations. 相似文献