全文获取类型
收费全文 | 624篇 |
免费 | 93篇 |
国内免费 | 9篇 |
专业分类
耳鼻咽喉 | 12篇 |
儿科学 | 29篇 |
妇产科学 | 7篇 |
基础医学 | 68篇 |
口腔科学 | 48篇 |
临床医学 | 191篇 |
内科学 | 96篇 |
皮肤病学 | 3篇 |
神经病学 | 30篇 |
特种医学 | 30篇 |
外科学 | 55篇 |
综合类 | 3篇 |
预防医学 | 35篇 |
眼科学 | 1篇 |
药学 | 22篇 |
中国医学 | 1篇 |
肿瘤学 | 95篇 |
出版年
2023年 | 5篇 |
2021年 | 8篇 |
2020年 | 5篇 |
2019年 | 9篇 |
2018年 | 19篇 |
2017年 | 19篇 |
2016年 | 14篇 |
2015年 | 20篇 |
2014年 | 25篇 |
2013年 | 19篇 |
2012年 | 24篇 |
2011年 | 20篇 |
2010年 | 18篇 |
2009年 | 24篇 |
2008年 | 23篇 |
2007年 | 29篇 |
2006年 | 12篇 |
2005年 | 18篇 |
2004年 | 16篇 |
2003年 | 18篇 |
2002年 | 23篇 |
2001年 | 27篇 |
2000年 | 16篇 |
1999年 | 20篇 |
1998年 | 27篇 |
1997年 | 23篇 |
1996年 | 26篇 |
1995年 | 13篇 |
1994年 | 17篇 |
1993年 | 12篇 |
1992年 | 8篇 |
1991年 | 8篇 |
1990年 | 8篇 |
1989年 | 14篇 |
1988年 | 14篇 |
1987年 | 18篇 |
1986年 | 7篇 |
1985年 | 13篇 |
1984年 | 10篇 |
1983年 | 9篇 |
1982年 | 7篇 |
1981年 | 10篇 |
1980年 | 5篇 |
1978年 | 4篇 |
1977年 | 5篇 |
1976年 | 8篇 |
1975年 | 4篇 |
1974年 | 7篇 |
1972年 | 3篇 |
1971年 | 3篇 |
排序方式: 共有726条查询结果,搜索用时 15 毫秒
41.
Effect of standardized orders and provider education on head-of-bed positioning in mechanically ventilated patients 总被引:3,自引:0,他引:3
Helman DL Sherner JH Fitzpatrick TM Callender ME Shorr AF 《Critical care medicine》2003,31(9):2285-2290
OBJECTIVE: Semirecumbent head-of-bed positioning in mechanically ventilated patients decreases the risk of developing ventilator-associated pneumonia (VAP). The purpose of this study was to determine whether the addition of a standardized order followed by the initiation of a provider education program would increase the frequency with which our patients were maintained in the semirecumbent position. DESIGN: Prospective, pre-, and postintervention observational study. SETTING: A tertiary care, U.S. Army teaching hospital. PATIENTS: Mechanically ventilated medical and surgical intensive care unit patients. INTERVENTIONS: The first intervention involved the addition of an order for semirecumbent head-of-bed positioning to our intensive care unit order sets. This was followed 2 months later with a second intervention, which was a nurse and physician education program emphasizing semirecumbent positioning. MEASUREMENTS AND MAIN RESULTS: Data regarding head-of-bed positioning were collected on 100 patient observations at baseline and at 1 and 2 months after each of our interventions. The mean angle of head of bed increased from 24 +/- 9 degrees at baseline to 35 +/- 9 degrees (p <.05) 2 months after the addition of the standard order. The percentage of observations with head of bed >45 degrees increased from 3% to 16% 2 months after the standardized order (p <.05). Two months after our provider education program, the mean angle of the head of bed was 34 +/- 11 degrees and the percentage of patients with head of bed >45 degrees was 29% (p = NS compared with values after the first intervention). Data collected 6 months after completion of our education programs showed that these improvements were maintained. CONCLUSIONS: Standardizing the process of care via the addition of an order specifying head-of-bed position significantly increased the number of patients who were placed in the semirecumbent position. In an era of cost-conscious medicine, interventions that utilize protocols and education programs should be emphasized. 相似文献
42.
Constitutive activation of Akt has been found in many types of human cancer, and is believed to promote proliferation and increased cell survival thereby contributing to cancer progression. In this study, we examined Akt phosphorylation on Ser473 and Thr308 in seven IGF-II-overexpressing rhabdomyosarcomas (RMS) cells. All the RMS cell lines tested had high levels of Akt phosphorylation on Thr308, whereas three cell lines (Rh5, Rh18, and CTR) had a much lower level of Akt phosphorylation on Ser473. To determine whether the difference in Akt phosphorylation on Ser473, but not on Thr308, observed among cell lines is a cell-specific phenomenon or due to other factors, which possibly downregulate Akt phosphorylation, we examined expression of PTEN protein, which acts as a negative regulator of the PI3K/Akt signaling pathway through its ability to dephosphorylate phosphatidylinositol 3,4,5-triphosphate (PIP3). The levels of PTEN expression inversely correlate with Akt phosphorylation on Ser473, but not on Thr308. Consistent with this finding, transfection of wild-type PTEN into RMS and mouse myoblast C2C12 cells resulted in reduced Akt phosphorylation on Ser473, but not on Thr308. Our data suggest that Ser473 may be a key target residue for PTEN to modulate the effects of IGF-II on activating the PI3K/Akt pathway in RMS cells. A better understanding of the pathway in RMS will likely contribute to insights into the biology of the RMS tumorigenesis and hopefully lead to novel therapeutic options. 相似文献
43.
Zhang H Merchant MS Chua KS Khanna C Helman LJ Telford B Ward Y Summers J Toretsky J Thomas EK June CH Mackall CL 《Cancer biology & therapy》2003,2(5):579-586
Inadequate costimulation by solid tumors is generally believed to induce immune tolerance during primary tumor growth. We looked for tumor-specific immunity vs. tolerance in patients with Ewing's sarcoma. Circulating T cells from patients with progressively growing Ewing's tumors displayed MHC restricted tumor-induced proliferation and robust tumor lysis. Tumor-reactive T cells reside within the memory CD3+CD8+ subset and are CD28-/4-1BB+. Autologous Ewing's tumors expressed 4-1BBL, and tumor-induced T cell proliferation and activation required costimulation by 4-1BBL. Stimulation of PBL with anti-CD3/4-1BBL, but not anti-CD3/anti-CD28 induced tumor lytic effectors. Similarly, in a xenograft model, anti-CD3/4-1BBL expanded T cells controlled primary growth and prevented metastasis of autologous tumors while nonactivated and anti-CD3/anti-CD28 activated CD8+ cells did not. These results question prevailing models of tumor induced tolerance accompanying progressive tumor growth; rather, we show coexistence of progressive tumor growth and anti-tumor immunity, with costimulation provided by the tumor itself. They further demonstrate a potential new therapeutic role for 4-1BBL mediated costimulation in expanding tumor reactive CTLs for use in the adoptive immunotherapy of cancer. 相似文献
44.
Metastasis-associated differences in gene expression in a murine model of osteosarcoma 总被引:24,自引:0,他引:24
Khanna C Khan J Nguyen P Prehn J Caylor J Yeung C Trepel J Meltzer P Helman L 《Cancer research》2001,61(9):3750-3759
Despite advances in the management of osteosarcoma (OSA) and other solid tumors, the development of metastasis continues to be the most significant problem and cause of death for cancer patients. To define genetic determinants of pulmonary metastasis, we have applied cDNA microarrays to a recently described murine model of OSA that is characterized by orthotopic tumor growth, a period of minimal residual disease, spontaneous pulmonary metastasis, and cell line variants that differ in metastatic potential. Microarray analysis defined 53 genes (of 3166 unique cDNAs) that were differentially expressed between the primary tumors of the more aggressive (K7M2) and less aggressive (K12) OSA models. By review of the literature, these differentially expressed genes were assigned to six nonmutually exclusive metastasis-associated categories (proliferation and apoptosis, motility and cytoskeleton, invasion, immune surveillance, adherence, and angiogenesis). Functional studies to evaluate K7M2 and K12 for differences in each of these metastasis-associated processes revealed enhanced motility, adherence, and angiogenesis in the more aggressive K7M2 model. For this reason, 10 of the 53 differentially expressed genes that were assigned to the motility and cytoskeleton, adherence, and angiogenesis categories were considered as most likely to define differences in the metastatic behavior of the two models. Ezrin, a gene not described previously in OSA, with functions in motility, invasion, and adherence, was 3-fold overexpressed in K7M2 compared with K12 by microarray. Differential expression for RNA was confirmed by Northern analysis and for protein by immunostaining. Alterations in ezrin protein levels and concomitant cytoskeletal changes in our model confirmed predictions from the arrays. The potential relevance of ezrin in OSA was suggested by its expression in five of five human OSA cell lines. This work represents a rationale approach to the evaluation of microarray data and will be useful to identify genes that may be causally associated with metastasis. 相似文献
45.
Activated peripheral T-lymphocytes are increased in both pre-insulin-dependent diabetes mellitus (IDDM) patients and in recently diagnosed IDDM patients, as well as in various forms of acute stress. We studied the in vivo T-lymphocyte activation in six patients in severe diabetic ketoacidosis (DKA) prior to treatment, after 24 h of treatment and > or =5 days after admission. Five of the six patients showed an increased percentage of activated T-lymphocytes based on the expression of HLA-DR at 24 h of treatment when compared to the admission percentage of activation (P<.05). There was no correlation to the admission serum glucose, osmolality, or electrolytes. Serum pH showed a trend toward an inverse correlation, but was not statistically significant. We speculate that T-lymphocyte activation plays a role in the progression of the acute complications of subclinical brain edema and interstitial pulmonary edema of DKA. This process could also be another factor in the progression of the chronic complications of IDDM in addition to the well-established effects of hyperglycemia and hypertension. 相似文献
46.
Autocrine Transforming Growth Factor-beta Growth Pathway in Murine Osteosarcoma Cell Lines Associated with Inability to Affect Phosphorylation of Retinoblastoma Protein 下载免费PDF全文
Purpose. Production of active transforming growth factor-beta (TGF-beta ) by human osteosarcoma may contribute to malignant progression through mechanisms that include induction of angiogenesis, immune suppression and autocrine growth stimulation of tumor cell growth.To study events associated with induction of cell proliferation by TGF-beta , we have evaluated the TGF-beta pathway in two murine osteosarcoma cell lines, K7 and K12.Results. Northern and immunohistochemical analyses show that each cell line expressesTGF-beta1 and TGF-beta3 mRNA and protein. Both cell lines secrete activeTGF-beta 1 and display a 30-50% reduction in growth when cultured in the presence of a TGF-beta blocking antibody. Expression of TGF-beta receptors TbetaRI, TbetaRII and TbetaRIII is demonstrated by affinity labeling with (125) -TGF-beta 1, and the intermediates, Smads 2, 3 and 4, are uniformly expressed. Smads 2 and 3 are phosphorylated in response toTGF-beta , while pRb phosphorylation in each osteosarcoma cell line is not affected by either exogenousTGF-beta or TGF-beta antibody.Conclusions. The data implicate events downstream of Smad activation, including impaired regulation of pRb, in the lack of a growth inhibitory response toTGF-beta , and indicate that this murine model of osteosarcoma is valid for investigating the roles of autocrineTGF-beta in vivo. 相似文献
47.
AIM: To examine the relationship between cigarette smoking and breastfeeding duration at 2 wk, 6 mo, and longer. METHODS: Design. A 12-mo longitudinal study. Setting. Two public maternity hospitals in the Perth metropolitan area (Western Australia). Subjects. Eligible mothers of healthy newborn infants. Interventions. Participants completed a self-administered baseline questionnaire while in hospital or shortly after discharge. All women regardless of their chosen infant feeding method were followed up by telephone interview at 4, 10, 16, 22, 32, 40 and 52 wk postpartum. Main outcome measures. Prevalence of breastfeeding at 2 wk, 2 wk to 6 mo and >6 mo in women who smoked during pregnancy, and breastfeeding duration. RESULTS: Women who smoked during pregnancy had a lower prevalence and shorter duration of breastfeeding than non-smoking mothers (28 vs 11 wk, 95% CI 8.3-13.7). This effect remained even after adjustment for age, education, income, father's smoking status, mother's country of birth, intended duration of breastfeeding >6 mo and birthweight (risk ratio 1.59, 95% CI 1.22-2.08). CONCLUSION: Women who smoke during pregnancy are at greater risk of not achieving national and international targets for breastfeeding. Encouraging smoking cessation in the antenatal setting is an area for considerable public health gain. 相似文献
48.
49.
Magnetic resonance (MR) imaging was performed on 14 patients with histologically proved osteosarcoma (mean age, 14.4 years). There was excellent correlation of intramedullary tumor extent as determined with MR imaging and pathologic examination (r = 99%). This was facilitated by the presence of a chemical shift artifact at the tumor-marrow interface on the T1-weighted images. The correlation between CT and pathologic findings was not as good (r = 84%). In a single patient, however, a 10-cm length of sclerotic bone was incorrectly interpreted as being tumor. If this case is excluded, the correlation between CT and pathologic findings improves significantly (r = 96%). T2-weighted images were optimal in demonstrating soft-tissue bulk and breach of the epiphysis or cortex. Vascular involvement was also readily defined. The T2 value of the tumor soft-tissue component decreased in patients who were deemed to have responded well to therapy. Two patients with very high T2 values after chemotherapy developed wide-spread metastatic disease and died. Phosphorus-31 MR spectroscopy of five patients with osteosarcoma showed elevated levels of phosphomonoesters (PMEs), inorganic phosphate (Pi), and phosphodiesters (PDEs). PME and PDE peak areas decreased in three patients after chemotherapy, while Pi peak areas increased. 相似文献
50.
While avid accumulation of gallium-67 citrate and technetium-99m methylene diphosphonate (MDP) occurs initially in most cases of primary Ewing sarcoma, uptake after therapy is less well defined. Thirty patients with Ewing sarcoma who underwent Ga-67 and bone scintigraphy at diagnosis, at completion of therapy, and at relapse from 1978 to 1988 were evaluated. All 30 patients showed less primary site Ga-67 activity following therapy. Twenty-three of 28 patients who underwent corresponding bone scintigraphy showed less uptake, but residual activity was usually more intense than with Ga-67. Avid reaccumulation of Ga-67 occurred in four of five patients with primary site relapse, while patients who underwent bone scintigraphy showed less change. It was concluded that a greater decrease in Ga-67 than in Tc-99m MDP uptake often occurs in patients successfully treated for primary Ewing sarcoma. Information obtained at Ga-67 scintigraphy is most likely to be helpful if results of bone scintigraphy remain abnormal or if occult relapse is suspected. 相似文献