全文获取类型
收费全文 | 9761篇 |
免费 | 1147篇 |
国内免费 | 42篇 |
专业分类
耳鼻咽喉 | 148篇 |
儿科学 | 333篇 |
妇产科学 | 128篇 |
基础医学 | 1238篇 |
口腔科学 | 342篇 |
临床医学 | 1083篇 |
内科学 | 2154篇 |
皮肤病学 | 206篇 |
神经病学 | 755篇 |
特种医学 | 558篇 |
外科学 | 1263篇 |
综合类 | 205篇 |
一般理论 | 10篇 |
预防医学 | 1155篇 |
眼科学 | 283篇 |
药学 | 600篇 |
中国医学 | 11篇 |
肿瘤学 | 478篇 |
出版年
2023年 | 80篇 |
2021年 | 133篇 |
2020年 | 162篇 |
2019年 | 124篇 |
2018年 | 218篇 |
2017年 | 166篇 |
2016年 | 162篇 |
2015年 | 170篇 |
2014年 | 248篇 |
2013年 | 379篇 |
2012年 | 383篇 |
2011年 | 393篇 |
2010年 | 286篇 |
2009年 | 303篇 |
2008年 | 390篇 |
2007年 | 424篇 |
2006年 | 407篇 |
2005年 | 440篇 |
2004年 | 388篇 |
2003年 | 391篇 |
2002年 | 399篇 |
2001年 | 250篇 |
2000年 | 288篇 |
1999年 | 214篇 |
1998年 | 196篇 |
1997年 | 220篇 |
1996年 | 171篇 |
1995年 | 171篇 |
1994年 | 122篇 |
1993年 | 119篇 |
1992年 | 172篇 |
1991年 | 167篇 |
1990年 | 173篇 |
1989年 | 189篇 |
1988年 | 166篇 |
1987年 | 150篇 |
1986年 | 157篇 |
1985年 | 151篇 |
1984年 | 131篇 |
1983年 | 110篇 |
1982年 | 91篇 |
1981年 | 109篇 |
1980年 | 89篇 |
1979年 | 91篇 |
1978年 | 87篇 |
1976年 | 74篇 |
1975年 | 75篇 |
1974年 | 71篇 |
1973年 | 85篇 |
1972年 | 55篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Fatimah Jaafar Elda Righi Victoria Lindstrom Christine Linton Mahrokh Nohadani Susan Van Noorden Tyler Lloyd Joshua Poznansky Gordon Stamp Roberto Dina Dulcie V. Coleman Mark C. Poznansky 《The American journal of pathology》2009,175(4):1525-1535
Human cervical cancer is an immunogenic tumor with a defined pattern of histopathological and clinical progression. Tumor-infiltrating T cells contribute to immune control of this tumor; however, cervical cancer dysregulates this immune response both through its association with human papillomavirus (HPV) infection and by producing cytokines and chemokines. Animal tumor models have revealed associations between overproduction of the chemokine stromal cell-derived factor-1 (SDF-1 or CXCL12) and dysregulation of tumor-specific immunity. We therefore proposed that CXCL12 expression by cervical precancerous and cancerous lesions correlates with histopathological progression, loss of immune control of the tumor, and HPV infection. We found a significant association between cancer stage and CXCL12 expression for squamous and glandular lesions as well as with the HPV16+ (high-risk) status of the neoplastic lesions. Cancer progression was correlated with increasing levels of FoxP3 T-cell infiltration in the tumor. FoxP3 and CXCL12 expression significantly correlated for squamous and glandular neoplastic lesions. These observations were supported by enzyme-linked immunosorbent assay and Western blotting. In addition, we demonstrated CXCL12 expression by dyskaryotic cells in ThinPrep cervical smears. This study robustly links increased CXCL12 expression and FoxP3+-cell infiltration to HPV infection and progression of cervical cancer. It supports the detection of CXCL12 in cervical smears and biopsies as an additional biomarker for this disease.Human cervical cancer is an immunogenic tumor, and several tumor-specific antigens have been identified in recent years.1,2,3 Persistent infection with high-risk human papillomavirus (HPV) (types 16 and 18) has been shown to be an important risk factor for malignant transformation of the cervical epithelium.4,5 Tumor immunity in this context results from the positive recognition of tumor antigens by immature dendritic cells, which subsequently migrate to draining lymph nodes and interact with and activate both helper CD4+ T cells and effector antigen-specific CD8+ T cells.1 Activated and targeted antigen-specific cytotoxic CD8+ T cells subsequently circulate through the peripheral blood to the tumor and then selectively transmigrate into the cancer itself and kill tumor cells. Immune control of cervical cancer is therefore critically dependent on the activation and migration of tumor-specific cytotoxic T cells into the tumor and the subsequent killing of neoplastic cells. The success of the immune response in destroying cervical cancer is thought to depend on the relationship between the kinetics of tumor growth and the efficacy of tumor-specific cytotoxic T cells (in balance with regulatory T cells) in infiltrating the tumor and killing neoplastic cells over time. It is well established that the magnitude of T-cell infiltration within certain forms of cancer correlates with a favorable prognosis.6Tumors, including cervical cancer, evade immune recognition using a number of different mechanisms, including the down-regulation of major histocompatibility class I antibodies, the immunological ignorance to tumor antigens, the lack of costimulatory molecules and antigen loss, or the expression of inhibitory molecules.7,8 Several studies have also shown that tumors, including cervical cancer, overexpress specific chemokines, such as stromal cell-derived factor 1 (SDF-1 or CXCL12), that are thought to dysregulate the immune response to the tumor.9,10,11 Chemokines are a superfamily of 8- to 11-kDa proteins found in humans that have been shown to be critical in causing directional movement of immune cells in vitro and in determining the localization of leukocytes in models of inflammatory, immune-mediated diseases, and cancer.11,12,13 Chemokines have been shown to act as chemoattractants for leukocyte subpopulations including T cells and dendritic cells. Chemokines signal via Gαi protein-coupled receptors on the cell surface and subsequently induce directed cell movement in response to a gradient of the chemokines.14The chemokine CXCL12 is a known T-cell chemoattractant that selectively binds the receptor CXCR4.9,10,11 Until recently CXCL12 was thought to have chemoattractant activity only for T cells. We recently demonstrated that the chemokine CXCL12 could serve as a bidirectional cue, attracting T cells at low concentrations and repelling at high concentrations in vitro and in vivo.15 Certain murine models of melanoma and ovarian cancer indicate that the effect of CXCL12 on the tumor immune response is dose dependent.16 Low levels of CXCL12 expression result in infiltration of the tumor by T cells, a delay in tumor growth, and the development of a long-lived tumor-specific T cell-mediated immune response. In contrast, high levels of CXCL12 expression result in reduced infiltration of the tumor by tumor antigen-specific T cells17 and the suppression of antitumor immune responses via various mechanisms including the intratumoral accumulation of FoxP3+ suppressor T cells.18,19We hypothesized that secretion of CXCL12 by cervical tumors is correlated with progression of the tumor and loss of immune control. To explore this hypothesis we first examined whether clinicopathological progression of cervical cancer is associated with an increase in CXCL12 expression and a concomitant reduction in immune cell infiltration into the tumor as the tumor progresses from a preinvasive to an invasive state. CXCL12 expression and T-cell infiltration were studied in tissue sections of normal cervix, preinvasive, microinvasive, and invasive squamous cervical cancer, and preinvasive and invasive adenocarcinoma using immunohistochemical (IHC) staining methods in concert with quantitative digital image analysis, Western blotting, and enzyme-linked immunosorbent assay (ELISA). Because HPV is associated with cervical cancer, we also examined the relationship between HPV status and CXCL12 expression in normal, preinvasive, and invasive cervical cancer. In this way we demonstrated that CXCL12 is a robust biomarker for clinical progression that is correlated both with HPV infection and the accumulation of FoxP3+ T cells in the tumor. 相似文献
992.
Background Positive psychology is an area gaining credence within the field of intellectual disability (ID). Hope is one facet of positive psychology that is relatively unstudied in parents of children with ID. In the present study, we explore hope and its relationships with parental well‐being in parents of school‐aged children with ID. Method A total of 138 mothers and 58 fathers of children with ID took part in a questionnaire‐based study. Parents reported on their feelings of hope and positive affect, other dimensions of psychological well‐being (anxiety, depression and stress), and on their child's behaviour. For this study, hope was measured as a goal driven behaviour comprising two components: agency (the perception that one can reach his/her goals) and pathways (the perception that one can find alternative routes to reach these goals should the need arise). Results For mothers, regression analyses revealed that lower levels of hope (agency and pathways) and more child behaviour problems predicted maternal depression. Positive affect was predicted by less problematic child behaviour and by higher levels of hope agency. For fathers, anxiety and depression were predicted by low hope agency and positive affect was predicted by high hope agency. Hope pathways was not a significant predictor of paternal well‐being. Hope agency and pathways interacted in the prediction of maternal depression such that mothers reporting high levels of both hope dimensions reported the lowest levels of depressive symptoms. Conclusions Hope is a construct that merits further investigation within families research, and is potentially a factor that could be utilised in intervention to help increase familial well‐being. 相似文献
993.
Harris V Lloyd K Forsey S Rogers P Roche M Parker C 《Clinical oncology (Royal College of Radiologists (Great Britain))》2011,23(10):706-708
The use of chemotherapy in the treatment of prostate cancer is a relatively recent development, with no published data on the patterns of care in the UK. We carried out a population-based study to assess variation in the use of prostate cancer chemotherapy over time in a UK cancer network. 相似文献
994.
995.
Confounding and interaction effect of Treponema denticola salivary carriage in chronic periodontitis
MC Martínez‐Pabón A Martínez‐Gaviria DM Isaza‐Guzmán CE Muskus‐López SI Tobón‐Arroyave 《Oral diseases》2010,16(3):278-285
Oral Diseases (2010) 16 , 278–285 Aim: To evaluate the salivary carriage of Treponema denticola and its association with demographic variables in the etiopathogenesis of chronic periodontitis. Subjects and methods: Ninety‐seven chronic periodontitis (CP) patients and a control group of 51 healthy subjects (HC) were selected. Periodontal status was assessed by criteria based on probing depth, attachment loss, extent, and severity of periodontal breakdown. A polymerase chain reaction method was used to determine the occurrence of T. denticola in saliva samples. Risk indicators for CP were assessed individually and adjusted for confounding and/or interaction using a logistic regression model. Results: Although univariate analysis revealed a positive association of age ≥30 years, smoking, and salivary carriage of T. denticola with CP, after logistic regression analysis, the association between age ≥30 years/smoking and CP persisted, whereas salivary carriage of T. denticola failed to achieve statistical significance. An interaction effect was significantly detected between these three variables. Conclusion: Although salivary carriage of T. denticola may be a risk indicator for CP, its pathogenicity should not be exclusively endorsed to its detection in saliva, but it might be associated with the synergistic biological interaction of the bacterium with some demographic characteristics of the susceptible host. 相似文献
996.
997.
998.
999.
1000.
Hall LT Hill CD Cole JH Städler B Caruso F Mulvaney P Wrachtrup J Hollenberg LC 《Proceedings of the National Academy of Sciences of the United States of America》2010,107(44):18777-18782
In drug discovery, there is a clear and urgent need for detection of cell-membrane ion-channel operation with wide-field capability. Existing techniques are generally invasive or require specialized nanostructures. We show that quantum nanotechnology could provide a solution. The nitrogen-vacancy (NV) center in nanodiamond is of great interest as a single-atom quantum probe for nanoscale processes. However, until now nothing was known about the quantum behavior of a NV probe in a complex biological environment. We explore the quantum dynamics of a NV probe in proximity to the ion channel, lipid bilayer, and surrounding aqueous environment. Our theoretical results indicate that real-time detection of ion-channel operation at millisecond resolution is possible by directly monitoring the quantum decoherence of the NV probe. With the potential to scan and scale up to an array-based system, this conclusion may have wide-ranging implications for nanoscale biology and drug discovery. 相似文献