全文获取类型
收费全文 | 118963篇 |
免费 | 41488篇 |
国内免费 | 121篇 |
专业分类
耳鼻咽喉 | 1824篇 |
儿科学 | 5185篇 |
妇产科学 | 506篇 |
基础医学 | 24852篇 |
口腔科学 | 6688篇 |
临床医学 | 14698篇 |
内科学 | 26944篇 |
皮肤病学 | 4431篇 |
神经病学 | 18791篇 |
特种医学 | 6036篇 |
外国民族医学 | 4篇 |
外科学 | 15500篇 |
综合类 | 723篇 |
一般理论 | 8篇 |
预防医学 | 8292篇 |
眼科学 | 1415篇 |
药学 | 9906篇 |
12篇 | |
中国医学 | 1829篇 |
肿瘤学 | 12928篇 |
出版年
2024年 | 39篇 |
2023年 | 193篇 |
2022年 | 312篇 |
2021年 | 1918篇 |
2020年 | 6305篇 |
2019年 | 11606篇 |
2018年 | 11169篇 |
2017年 | 12407篇 |
2016年 | 11513篇 |
2015年 | 11396篇 |
2014年 | 11262篇 |
2013年 | 11467篇 |
2012年 | 10549篇 |
2011年 | 10483篇 |
2010年 | 9139篇 |
2009年 | 5589篇 |
2008年 | 6192篇 |
2007年 | 4564篇 |
2006年 | 4328篇 |
2005年 | 4090篇 |
2004年 | 3945篇 |
2003年 | 3621篇 |
2002年 | 3407篇 |
2001年 | 2597篇 |
2000年 | 1426篇 |
1999年 | 288篇 |
1998年 | 78篇 |
1997年 | 68篇 |
1996年 | 67篇 |
1995年 | 69篇 |
1994年 | 51篇 |
1993年 | 47篇 |
1992年 | 54篇 |
1991年 | 48篇 |
1990年 | 44篇 |
1989年 | 30篇 |
1988年 | 24篇 |
1987年 | 19篇 |
1986年 | 14篇 |
1985年 | 29篇 |
1984年 | 20篇 |
1983年 | 9篇 |
1982年 | 19篇 |
1981年 | 12篇 |
1980年 | 16篇 |
1979年 | 8篇 |
1978年 | 7篇 |
1977年 | 9篇 |
1976年 | 8篇 |
1975年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Horiguchi A Nakashima J Horiguchi Y Nakagawa K Oya M Ohigashi T Marumo K Murai M 《The Prostate》2003,56(1):23-29
BACKGROUNDS: The present study was designed to identify the preoperative parameters, including PSA-based parameters, and endorectal MRI, predictive of pathological stage in males who underwent radical prostatectomy. METHODS: We studied 114 patients who underwent radical retropubic prostatectomy and pelvic lymphadenectomy for clinically localized prostate cancer. Clinical stage was assessed by DRE, pelvic CT scan, endorectal MRI, and bone scan. The correlation between the preoperative parameters, including PSA-based parameters, clinical stage, and histological findings of biopsy specimens, and the pathological stage was analyzed. Logistic regression analysis was performed to identify a significant set of independent predictors for local extent of disease. RESULTS: Seventy-six (66.6%) patients had organ confined cancer and 38 (33.4%) patients had extraprostatic cancer. Of the 38 patients with extraprostatic cancer, four had seminal vesicle involvement, while, none had pelvic lymph node involvement. Biopsy Gleason score, PSA, PSA-alpha1-antichymotrypsin (PSA-ACT), PSA-density (PSAD), PSA-transition zone density, PSA-ACT density, and PSA-ACT transition zone (TZ) density were significantly higher and percent free PSA was lower in the patients with organ confined cancer than those with extraprostatic cancer (P < 0.01). PSAD showed the largest area under the ROC curve (AUC) among those parameters (AUC = 0.732). Sixty-eight (74.7%) of 91 patients with T2 on endorectal MRI had organ confined cancer, while 15 (65.2%) of 23 patients with T3 had extraprostatic cancer (P < 0.01). Multivariate logistic regression analysis indicated that Gleason score (> or =7 vs. < or =6), endorectal MRI findings, and PSAD were significant predictors of extraprostatic cancer (P < 0.01). CONCLUSIONS: The present study demonstrated that preoperative PSAD was the most valuable predictor among PSA-based parameters for extraprostatic disease in patients with clinically localized prostate cancer. The combination of PSAD, endorectal MRI findings, and biopsy Gleason score can provide additional information for selecting appropriate candidates for radical prostatectomy. 相似文献
992.
alpha-Tricalcium phosphate bone cement, as formerly designed and developed by Driessens et al., consists of a powder composed by alpha-tricalcium phosphate (alpha-TCP) and hydroxyapatite (HA) seeds, and an aqueous solution of Na2HPO4 as mixing liquid. After mixing powder and liquid, alpha-TCP dissolves into the liquid and calcium deficient hydroxyapatite (CDHA), more insoluble than the former, precipitates as an entanglement of crystals, which causes the setting and hardening of the cement. alpha-TCP bone cement offers several advantages in comparison to calcium phosphate bioceramics and acrylic bone cements as bone graft and repairing material, like perfect adaptability to the defect size and shape, osteotransductibility, and absence of thermal effect during setting. The main handicap is its low mechanical strength. Therefore, approaching its mechanical strength to that of human bone could considerably extend its applications. In the present work, an in situ polymerization system based on acrylamide (AA) and ammonium polyacrylate (PA) as liquid reducer was added to alpha-TCP cement to increase its mechanical strength. The results showed that the addition of 20 wt% of acrylamide and 1 wt% AP to the liquid increased the compressive and tensile strength of alpha-TCP bone cement by 149 and 69% (55 and 21 MPa), respectively. The improvement in mechanical strength seems to be caused by a decrease of porosity and the reinforcing effect of a polyacrylamide network coexisting with the entanglement of CDHA crystals. The studied additives do not affect the nature of the final product of the setting reaction, CDHA, but promote the reduction of its crystal size. 相似文献
993.
Facial rhytides—subsurfacing or resurfacing? A review 总被引:4,自引:0,他引:4
STUDY DESIGN/BACKGROUND AND OBJECTIVES: Currently, ablative laser therapy (with CO2/Er:YAG lasers) is considered an effective and promising method of skin rejuvenation. The induction of collagen synthesis was observed after treatments with the CO2 laser and with the long-pulsed Er:Yag laser. In past years, the undesirable side effects and risks of these methods have led to intensified research efforts in the fields of non-ablative facial rejuvenation as well as subsurfacing by means of non-ablative laser systems and intense pulsed light systems. The objective is to achieve selective, heat-induced denaturalization of dermal collagen that leads to subsequent reactive synthesis of neocollagen but does not damage the epidermis. This article reviews the use of different types of lasers and intense pulsed light sources for the non-ablative treatment of facial rhytides. RESULTS: The results of numerous clinical and histological investigations have recently indicated that these new technologies are successful. Some studies demonstrated remarkable effects with non-ablative systems; others, however, showed only limited cosmetic improvement or none at all. CONCLUSIONS: After critical review and assessment of current literature on the treatment of rhytides, we have found that non-ablative methods do not appear to be a comparable alternative to ablative skin resurfacing in terms of their efficacy and side effects. 相似文献
994.
Cognitive dysfunction after minor surgery in the elderly 总被引:15,自引:0,他引:15
Canet J Raeder J Rasmussen LS Enlund M Kuipers HM Hanning CD Jolles J Korttila K Siersma VD Dodds C Abildstrom H Sneyd JR Vila P Johnson T Muñoz Corsini L Silverstein JH Nielsen IK Moller JT;ISPOCD investigators 《Acta anaesthesiologica Scandinavica》2003,47(10):1204-1210
BACKGROUND: Major surgery is frequently associated with postoperative cognitive dysfunction (POCD) in elderly patients. Type of surgery and hospitalization may be important prognostic factors. The aims of the study were to find the incidence and risk factors for POCD in elderly patients undergoing minor surgery. METHODS: We enrolled 372 patients aged greater than 60 years scheduled for minor surgery under general anesthesia. According to local practice, patients were allocated to either in- (199) or out-patient (173) care. Cognitive function was assessed using neuropsychological testing preoperatively and 7 days and 3 months postoperatively. Postoperative cognitive dysfunction was defined using Z-score analysis. RESULTS: At 7 days, the incidence (confidence interval) of POCD in patients undergoing minor surgery was 6.8% (4.3-10.1). At 3 months the incidence of POCD was 6.6% (4.1-10.0). Logistic regression analysis identified the following significant risk factors: age greater than 70 years (odds ratio [OR]: 3.8 [1.7-8.7], P = 0.01) and in- vs. out-patient surgery (OR: 2.8 [1.2-6.3], P = 0.04). CONCLUSIONS: Our finding of less cognitive dysfunction in the first postoperative week in elderly patients undergoing minor surgery on an out-patient basis supports a strategy of avoiding hospitalization of older patients when possible. 相似文献
995.
Anti-inflammatory cytokine response and the development of multiple organ failure in severe sepsis 总被引:9,自引:0,他引:9
BACKGROUND: The production of proinflammatory cytokines activates the systemic inflammatory response in sepsis. Patients also develop a compensatory anti-inflammatory reaction, which may have an important down-regulatory effect on the overactive inflammation. However, the role of this anti-inflammatory response in sepsis is not completely clarified. In this prospective study, we investigated the relationship between the pro- and anti-inflammatory cytokine profiles in severe sepsis and their role in the development of multiple organ failure (MOF). METHODS: Thirty-eight patients meeting the criteria for severe sepsis were studied. MOF was defined as a maximum SOFA score of 10 or higher. Serial measurements of the proinflammatory IL-6 and IL-1beta and the anti-inflammatory IL-10 and IL-1ra were used. The cytokine samples were taken at the onset of sepsis and on the third and fifth day during the ICU period. RESULTS: The initial IL-10 and IL-1ra responses were identical in patients with or without MOF. The anti-inflammatory cytokine levels remained elevated in the MOF patients, whereas in patients without MOF the levels declined. The IL-6/IL-10 ratio was significantly higher in the MOF patients on days 1 and 3 compared with patients without MOF. CONCLUSIONS: We could not demonstrate overproduction of anti-inflammatory IL-10 in MOF patients. On the contrary, the high IL-6/IL-10 ratio indicates that IL-10 deficiency may contribute to the development of MOF in severe sepsis. 相似文献
996.
Melioli G Semino C Margarino G Mereu P Scala M Cangemi G Crocetti E Machì AM Ferlazzo G 《Head & neck》2003,25(4):297-305
BACKGROUND: In a group of patients with head and neck cancers (H&NC), the expansion of the population of CD3-,CD16+ natural killer (NK) cells in the peripheral blood was studied. METHODS: Cytofluorimetric analysis of the expression of killer Ig-like receptors (KIR, namely p58.1, p58.2, p58.3, p70, and p140) and CD94-NKG2a was performed. Cytolytic activities were studied using 51Cr release assay. T and NK cell cloning was performed using limiting dilution culture conditions. Cytokine production was analyzed using commercial enzyme immunoassays. RESULTS: Phenotypic analysis showed that the expanded populations were heterogeneous. Even in the presence of a large number of circulating NK cells, "nonspecific" cytolytic capacities were heavily reduced, whereas cytolytic capacity related to T cells was virtually normal. Unlike NK cell clones derived from healthy donors, most NK cells derived from H&NC patients expressed surface "activating" NK cell receptors (KAR) for HLA, detected by use of a redirected cytolytic assay. Analysis of the CD4+ subpopulation at the clonal level demonstrated that they had a severe proliferative defect. CONCLUSION: These experimental data indicated that H&NC patients have a polyclonal expansion of functionally deficient NK cells expressing KAR. In addition, the proliferative capacity of patients' "helper" cells was strongly inhibited, thus accounting for a severe impairment of cytolytic activity of the expanded NK cells. 相似文献
997.
Rigas A Karamanolakis D Bogdanos I Stefanidis A Androulakakis PA 《BJU international》2003,92(1):101-103
OBJECTIVE: To present the characteristic clinical and imaging findings of pelvi-ureteric junction (PUJ) obstruction caused by crossing renal vessels (CRV), as it presents particular features within the spectrum of congenital hydronephrosis. PATIENTS AND METHODS: Between April 1982 and December 2000, 384 children underwent surgery for PUJ obstruction. In 71 (18.5%; mean age 8.5 years, range 2 months to 14 years; 49 aged> 5 years), the obstruction was caused by CRV. The data collected from the medical records of these patients were analysed for their clinical presentation and imaging findings, i.e. ultrasonography (US), intravenous urography (IVU) and diuretic renography. RESULTS: The main presenting symptom was recurrent renal colic (pain, nausea, vomiting) in 59%, followed by urinary infection (UTI) in 20%, gross haematuria in 11% and an incidental diagnosis in 10%. By contrast, in the 313 children with intrinsic PUJ obstruction, renal colic was present in only 10.5%. Moreover, from 1991 to 2000, when the use of prenatal US became widespread, hydronephrosis was detected prenatally in 42 of 212 children (20%) with intrinsic PUJ obstruction, but in only two of 31 (6%) with obstruction by CRV. However, in 10 children with CRV operated on during this period, prenatal US had shown mild hydronephrosis (< 15 mm), which during the follow-up decreased until the children became symptomatic after 5-9 years (eight renal colic, two UTI). US during acute symptoms showed significant hydronephrosis (> 25 mm), and colour Doppler US of two patients directly showed the CRV. In all 71 children with CRV obstruction diuretic IVU and renography during the acute symptoms had an obstructive pattern, and in 24 renal colic was reproduced during the examination. The differential kidney function was < 40% in 11 children who presented with UTI; two required nephrectomy and in the remaining 69 an Anderson-Hynes pyeloplasty, after which none had an episode of renal colic or UTI during a mean (range) follow-up of 10.2 (2-20) years. CONCLUSIONS: PUJ obstruction by CRV should be suspected in older children presenting with recurrent renal colic and hydronephrosis. Good kidney function is expected in most of these children, despite their age, because the vascular obstruction is intermittent. Mild prenatal hydronephrosis that could decrease postnatally does not exclude the possibility of vascular obstruction, which may later become symptomatic. Imaging (US, diuretic IVU and renography) during an episode of pain is essential and colour Doppler US could help to establish the diagnosis in these cases. Knowing that a child has a CRV is important for choosing an open surgical approach rather than endoscopic pyelotomy, to avoid potential complications 相似文献
998.
Akbari F Alavi M Esteghamati A Mehrsai A Djaladat H Zohrevand R Pourmand G 《BJU international》2003,92(3):281-283
OBJECTIVE: To assess the effect of successful renal transplantation on semen variables, sexual function and sex hormone profiles in a clinical trial. PATIENTS AND METHODS: Thirty patients on haemodialysis underwent renal transplantation; before and after surgery, their sperm density, motility and morphology were analysed, follicle-stimulating hormone (FSH), luteinizing hormone (LH), prolactin and testosterone levels measured and compared, and sexual function assessed using an abbreviated version of the International Index of Erectile Function (IIEF), with a successful outcome defined as a level of satisfaction of 4 or 5 on a 5-point scale. The paired t-test was used to assess the statistically significance of differences in all analyses. RESULTS: Sperm motility improved significantly (P < 0.001) but there were no significant changes in morphology or density (P = 0.33 and 0.068, respectively). Testosterone levels increased and FSH, LH and prolactin decreased significantly (P < 0.05) after renal transplantation. The IIEF showed that of the 30 patients, 14 were impotent before surgery and only six remained so afterward (P < 0.05). CONCLUSION: Although sperm morphology and density did not improve after renal transplantation, there were highly significant changes in sperm motility. Hormonal levels in patients on haemodialysis improved after transplantation and returned to nearly normal; sexual function was also significantly better. Further studies are needed to confirm these results. 相似文献
999.
Daniel Kim 《Magnetic resonance in medicine》2008,59(1):202-208
The dynamic T(1)-weighted signal in first-pass myocardial perfusion MRI can vary as a function of k-space trajectory. The purpose of this study, therefore, was to compare the relative T(1)-weighted signal produced by the linear, centric, and reverse centric k-space trajectories at 3T. The centric k-space trajectory yielded higher arterial input function (AIF) than the linear and reverse centric k-space trajectories (6.21 +/- 0.84 vs. 4.75 +/- 0.75 vs. 4.39 +/- 0.85 mM, respectively; N = 9; P < 0.01), and the reverse centric k-space trajectory yielded higher myocardial signal contrast (as a fraction of equilibrium magnetization) than the linear and centric k-space trajectories (0.17 +/- 0.02 vs. 0.12 +/- 0.02 vs. 0.05 +/- 0.01, respectively; N = 9; P < 0.001). Compared to the linear k-space trajectory, the centric k-space trajectory is relatively optimal for the quantification of AIF, whereas the reverse centric k-space trajectory is relatively optimal for high contrast of myocardial wall enhancement. 相似文献
1000.
Sanz R Martí-Bonmatí L Rodrigo JL Moratal D 《Journal of magnetic resonance imaging : JMRI》2008,27(1):171-177
PURPOSE: To study the pharmacokinetic parameters derived from dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) of the patellar cartilage under normal and pathological conditions. MATERIALS AND METHODS: DCE-MRI was obtained in 22 cases. There were 17 patients with degenerative patellar conditions (eight with chondromalacia and nine with osteoarthritis) and five normal subjects. The cartilage pharmacokinetic parameters of K(trans) (vascular permeability), k(ep) (extraction ratio), upsilon(e) (extravascular extracellular space [EES] volume fraction), and upsilon(p) (intravascular space volume fraction) were extracted. RESULTS: Statistically significant differences were observed between the different groups (normal cartilage, chondromalacia and osteoarthritis) for K(trans) and upsilon(e). K(trans) values were (mean +/- SD) 1.06 +/- 0.62, 11.97 +/- 8.91, and 21.21 +/- 16.03 mL x minute(-1) x 100 mL(-1) (P < 0.02), respectively; and upsilon(e) values were 0.71 +/- 0.69, 3.59 +/- 2.21, and 10.51 +/- 8.20% (P < 0.002). Reproducibility of the pharmacokinetic calculations was assessed with a second set of analyses of 10 random cases one week after the first analysis, showing a test-retest root mean square (RMS) coefficient of variation of 9.78% for K(trans) and 14.72% for upsilon(e). CONCLUSION: The vascular permeability and EES fraction of cartilage increases with the severity of the degeneration. Pharmacokinetic models allow to study the vascular properties of the cartilage and may have applications as a surrogate index in longitudinal studies to quantify the evolution of drug trials. 相似文献