首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   9112篇
  免费   662篇
  国内免费   23篇
耳鼻咽喉   67篇
儿科学   297篇
妇产科学   283篇
基础医学   1118篇
口腔科学   150篇
临床医学   1220篇
内科学   1566篇
皮肤病学   141篇
神经病学   774篇
特种医学   249篇
外科学   967篇
综合类   74篇
一般理论   17篇
预防医学   1165篇
眼科学   114篇
药学   633篇
中国医学   13篇
肿瘤学   949篇
  2024年   23篇
  2023年   117篇
  2022年   134篇
  2021年   245篇
  2020年   205篇
  2019年   256篇
  2018年   271篇
  2017年   223篇
  2016年   265篇
  2015年   261篇
  2014年   323篇
  2013年   482篇
  2012年   696篇
  2011年   794篇
  2010年   386篇
  2009年   313篇
  2008年   596篇
  2007年   579篇
  2006年   581篇
  2005年   525篇
  2004年   406篇
  2003年   441篇
  2002年   398篇
  2001年   102篇
  2000年   97篇
  1999年   90篇
  1998年   82篇
  1997年   56篇
  1996年   61篇
  1995年   41篇
  1994年   52篇
  1993年   43篇
  1992年   64篇
  1991年   40篇
  1990年   51篇
  1989年   45篇
  1988年   40篇
  1987年   31篇
  1986年   39篇
  1985年   21篇
  1984年   28篇
  1983年   29篇
  1982年   20篇
  1981年   20篇
  1979年   25篇
  1978年   15篇
  1977年   17篇
  1975年   23篇
  1974年   23篇
  1973年   21篇
排序方式: 共有9797条查询结果,搜索用时 15 毫秒
71.
72.
Despite continued development of effective HIV treatment, expanded access to care and advances in prevention modalities, HIV‐related stigma persists. We examine how, in the context of a universal HIV‐testing and treatment trial in South Africa and Zambia, increased availability of HIV services influenced conceptualisations of HIV. Using qualitative data, we explore people’s stigma‐related experiences of living in ‘intervention’ and ‘control’ study communities. We conducted exploratory data analysis from a qualitative cohort of 150 households in 13 study communities, collected between 2016 and 2018. We found that increased availability of HIV‐testing services influenced conceptualisations of HIV as normative (non‐exceptional) and the visibility of people living with HIV (PLHIV) in household and community spaces impacted opportunities for stigma. There was a shift in community narratives towards individual responsibility to take up (assumingly) widely available service – for PLHIV to take care of their own health and to prevent onward transmission. Based on empirical data, we show that, despite a growing acceptance of HIV‐related testing services, anticipated stigma persists through the mechanism of shifting responsibilisation. To mitigate the responsibilisation of PLHIV, heath implementers need to adapt anti‐stigma messaging and especially focus on anticipated stigma.  相似文献   
73.
The purpose of the study was to determine whether the organ environment can influence the response of colon cancer cells to chemotherapy. The highly metastatic human colon cancer cell line KM12L4, previously selected for production of liver metastases in nude mice, was injected into the cecal wall and into the spleen to produce liver metastases, and into the subcutis of nude mice. Doxorubicin (DOX) at 10 mg/kg or saline (control) was injected intravenously on days 7 and 16 after tumor cell injection. The in vivo response of tumors growing in the cecum, liver, and subcutaneous (s.c.) sites as well as the DOX sensitivity of cell lines established from liver and s.c. tumors were compared. Colon cancers growing s.c. were more sensitive to DOX than tumors growing in the cecal wall or liver of nude mice. The difference in response to DOX between s.c. tumors (sensitive) and liver tumors (resistant) was not due to selection of cell populations with different sensitivity to DOX, or differences in DOX distribution. PKC activity was lower in tumors of the liver and the cecum than in s.c. tumors. The expression of P-glycoprotein as determined by flow cytometric analysis of tumor cells harvested from lesions in different organs correlated inversely with their sensitivity to DOX. Increased levels of P-glycoprotein correlated with mdr-1, mdr-3 mRNA expression as determined by Northern analysis. Collectively, the data show that the organ environment influences the response of human colon carcinoma cells to DOX and recommend that animal models of this disease for experimental therapeutic studies employ orthotopic implantation of tumor cells.  相似文献   
74.
Résumé L'étude porte sur une série de 50 prothèses totales de genou GSB implantées entre 1981 et 1988 au Centre de Traumatologie et d'Orthopédie de Strasbourg. Cette prothèse entre dans la catégorie des prothèses à charnières cimentées, mais son pivot semi rigide diminue efficacement les contraintes exercées sur le ciment. Les résultats sont conformes à ceux retrouvés dans la littérature concernant les prothèses à charnière. L'accent a été mis plus particulièrement sur les complications spécifiques à ce type d'arthroplastie : infections, fractures, complications rotuliennes. Cependant le caractère semi rigide de la GSB a permis la disparition presque totale des descellements qui compliquaient d'ordinaire les prothèses à charnière. La prothèse GSB nous semble donc supérieure aux autres modèles de prothèse à charnière.  相似文献   
75.
The immobilization of vesicles has been conceptualized as a method to functionalize biointerfaces. However, the preservation of their integrity post immobilization remains a considerable challenge. Interfacial interactions can cause vesicle rupture upon close surface contact and non-specific protein adsorption impairing surface functions. To date, immobilization of vesicles has relied solely on either entrapment or prior modification of vesicles, both of which require laborious preparation and limit their applications. This work develops a bioinspired strategy to pin vesicles without prior modification while preserving their intact shape. This work introduces antifouling diblock copolymers and ultrathin surface-attached hydrogels containing a brush-like interface consisting of a bottle brush copolymer of N-(2-hydroxypropyl) methacrylamide (HPMA) and N-(3-methacrylamidopropyl)-N,N-dimethyldodecan-1-aminiumiodide (C12+). The presence of positive charges generates an attractive force that pulls vesicles toward the surface. At the surface, the amphiphilic properties of the combs facilitate their insertion into the membrane, mimicking the harpooning mechanism observed in antimicrobial peptides. Importantly, the antifouling poly(HPMA) backdrop serves to safeguard the vesicles by preventing deformation and breakage. Using a combination of thermodynamic analysis, surface plasmon resonance, and confocal laser scanning microscopy, this work demonstrates the efficiency of this biomimetic system to capture vesicles while maintaining an antifouling interface necessary for bioapplications.  相似文献   
76.
Fidler SJ  Rees AD 《Immunology letters》1999,66(1-3):129-134
Antigen presenting cell (APC) function is central to the activation of anti-viral cytotoxic T-cells and antibody production. In previous studies we have evaluated APC function in HIV-1 infected patients as the capacity to present peptide to a well defined panel of CD4 T-cell clones. We found that APC from HIV-1 infected patients were defective in the capacity to present peptide to CD4 T-cell clones. The APC defect uncovered by this method was present early in infection and worsened with increasing viral load, suggesting that it was an important determinant of progression and anti-viral efficacy. The CD4 T-cell clones were, however, found to vary in their susceptibility to the APC defect. CD4 T-cell clones that failed to respond to peptide presented by HIV + APC were 1000-fold more readily inhibited by anti-CD4 antibody than T-cell clones which consistently responded to APC from patients infected with HIV-1 (HIV + APC). An intermediate group of T-cell clones were also identified that only responded to peptide and HIV + APC from asymptomatic patients. These results suggested that the underlying mechanism for the APC defect was binding of T-cell CD4 by APC-associated gp120. In this paper we discuss the evidence to support this hypothesis.  相似文献   
77.
We studied the holding power during cut-out tests of 4 different screw fixation devices of the femoral head, correlated to head size and bone density, on 48 paired deep frozen proximal femurs of fresh gross specimens. We found no significant effect of the device on the holding power. There was a significantly higher maximal load at failure in large and dense heads. It seems then unnecessary to advocate more sophisticated but also more expensive devices to fix femoral neck fractures.  相似文献   
78.
This review focuses on malformations of the central nervous system that have a genetic etiology. One can view each malformation as giving us unique details on a map entitled "how to make a human brain." The gene(s) that cause each malformation are being identified, allowing discovery of their specific role in neurodevelopment, and defining a "road" on the map. The malformation is then the developmental consequence of "taking a wrong turn." Assimilation of complementary data from other species with human malformation phenotype and genotype is revealing just how wonderful and complex the neurodevelopment map is. Here we highlight recent research on brain malformations and how this is illuminating the map of normal human brain formation.  相似文献   
79.
A variety of resistance phenotypes to cytotoxic agents in bacteria, protozoa parasites and mammalian cells are mediated by evolutionarily conserved proteins of the mdr family. The finding that chloroquine resistance in the malarial parasite, Plasmodium falciparum, that is mediated by an mdr-1 gene product can be circumvented by tricyclic antidepressant drugs has stimulated the present study to assess whether this class of agents might also modulate the multidrug resistance (MDR) phenotype(s) in mammalian tumor cells. The possible chemosensitizing effects of nine antidepressant drugs have been tested against the UV-2237M murine fibrosarcoma line and its MDR variant. At nontoxic concentrations all nine antidepressants markedly enhanced the cytotoxicity of ADR against the parental cells but were much less effective against the MDR cells. The most active antidepressant, trazodone, also enhanced the cytotoxicities of vinblastine and vincristine, but not those of actinomycin D, mitomycin C, or 5-fluorouracil. The parental cells treated with trazodone exhibited an increased accumulation of intracellular ADR, but lacked detectable alterations in the expression and drug-binding activity of plasma membrane P-glycoprotein, and trazodone did not affect the activities of isolated protein kinase C and calmodulin. These data suggest that the antidepressant drug trazodone may be useful in the reversal of the intrinsic drug resistance of tumor cells that express low levels of P-glycoprotein.  相似文献   
80.
Atopic asthma is characterized by excessive T helper 2 (Th2)-like immunity to allergens in the bronchial mucosa. The Th2-cytokine interleukin (IL)-4 induces IgE production, while the Th2-cytokine IL-5 promotes eosinophilic inflammation in the airways of asthmatics. Most asthmatics are atopic, but a subgroup is non-atopic. We hypothesize that allergen-induced Th2, particularly IL-5, responses can be observed in peripheral blood in both atopic and non-atopic asthmatic children but not in healthy control children. The aim of the present study was to determine IL-4, IL-5, IL-9, IL-10, IL-13 and IFN-γ secretion induced from peripheral blood mononuclear cells (PBMC) by a broad panel of inhalant allergens (timothy, cat, birch, dog and house dust mite) in asthmatic children with and without sensitization. The study included 13 atopic asthmatic, 5 non-atopic asthmatic, and 12 non-atopic non-asthmatic children. PBMC were stimulated with allergens and cytokine production was measured with enzyme-linked immunosorbent assay (ELISA). Higher levels of cat and dog antigen-induced IL-5 release were more commonly observed in both atopic and non-atopic asthmatics than in controls. Children with atopic, but not non-atopic, asthma produced higher levels of allergen-induced IL-4 and IL-9 than controls. Non-atopic asthmatics produced more IL-10 than atopic asthmatics after cat stimulation. High levels of eosinophilia-associated IL-5 responses are induced by cat and dog allergen in both atopic and non-atopic asthmatic children. The Th2 cytokines IL-4 and IL-9 were associated only with atopic asthma, probably due to their IgE-inducing properties.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号