全文获取类型
收费全文 | 1391359篇 |
免费 | 104075篇 |
国内免费 | 4476篇 |
专业分类
耳鼻咽喉 | 17483篇 |
儿科学 | 44969篇 |
妇产科学 | 37450篇 |
基础医学 | 204970篇 |
口腔科学 | 36908篇 |
临床医学 | 135315篇 |
内科学 | 269572篇 |
皮肤病学 | 27090篇 |
神经病学 | 117088篇 |
特种医学 | 50039篇 |
外国民族医学 | 371篇 |
外科学 | 192977篇 |
综合类 | 29737篇 |
现状与发展 | 2篇 |
一般理论 | 531篇 |
预防医学 | 119768篇 |
眼科学 | 30178篇 |
药学 | 102392篇 |
6篇 | |
中国医学 | 3218篇 |
肿瘤学 | 79846篇 |
出版年
2021年 | 11850篇 |
2019年 | 12532篇 |
2018年 | 17363篇 |
2017年 | 13033篇 |
2016年 | 14057篇 |
2015年 | 16108篇 |
2014年 | 22282篇 |
2013年 | 34353篇 |
2012年 | 47418篇 |
2011年 | 50327篇 |
2010年 | 29052篇 |
2009年 | 26789篇 |
2008年 | 45801篇 |
2007年 | 48367篇 |
2006年 | 48466篇 |
2005年 | 46908篇 |
2004年 | 44850篇 |
2003年 | 42526篇 |
2002年 | 41259篇 |
2001年 | 61520篇 |
2000年 | 63109篇 |
1999年 | 53015篇 |
1998年 | 15328篇 |
1997年 | 13890篇 |
1996年 | 13706篇 |
1995年 | 13015篇 |
1994年 | 12154篇 |
1993年 | 11378篇 |
1992年 | 42119篇 |
1991年 | 41311篇 |
1990年 | 39897篇 |
1989年 | 37783篇 |
1988年 | 35017篇 |
1987年 | 34104篇 |
1986年 | 32545篇 |
1985年 | 31055篇 |
1984年 | 23562篇 |
1983年 | 20054篇 |
1982年 | 12292篇 |
1981年 | 10777篇 |
1979年 | 21142篇 |
1978年 | 15162篇 |
1977年 | 12387篇 |
1976年 | 12168篇 |
1975年 | 12382篇 |
1974年 | 15107篇 |
1973年 | 14754篇 |
1972年 | 13597篇 |
1971年 | 12600篇 |
1970年 | 11645篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
In the first 100 patients operated on for C T-E PH, three were referred with the diagnosis of UPAA having been made elsewhere. We found that many features of these two conditions are so similar that differential diagnosis is very difficult. Shared features may include findings on chest x-ray film, pulmonary angiography, CT scan and MRI studies. Since the two conditions vary substantially with respect to the methods of potential surgical correction, recognition of this possible differential diagnostic dilemma is important. 相似文献
992.
Lidocaine increases the energy required for ventricular defibrillation in dogs. Because sodium channel-blocking agents that are weak bases have pH-dependent electrophysiologic effects, we investigated the pH dependence of lidocaine (pKa, 7.9) on internal defibrillation energy requirements in 28 dogs with atrial spring and left ventricular patch electrodes. Results of defibrillation testing were used to derive 50% and 90% successful energy requirements (ED50 and ED90) using logistic regression and were compared with analysis of variance. Acidosis produced by hydrochloric acid infusion decreased the arterial pH from 7.40 +/- 0.05 (SD) to 7.18 +/- 0.03 (n = 8, p less than 0.01), but no significant change in ED90 was observed (14 +/- 4 to 16 +/- 6 J). Lidocaine infusion to therapeutic levels (4.2 +/- .07 micrograms/ml) at normal pH (7.42 +/- 0.02) increased ED90 from 13 +/- 3 to 17 +/- 3 J (n = 6, p less than 0.05), and subsequent acidosis (pH 7.19 +/- 0.02, p less than 0.01) exacerbated this effect of lidocaine on ED90 (22 +/- 5 J, p less than 0.05). Alkalosis produced by respirator hyperventilation increased the arterial pH from 7.41 +/- 0.03 to 7.60 +/- 0.03 (n = 8, p less than 0.01), with a fall in ED90 from 13 +/- 4 to 8 +/- 3 J (p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
993.
Pascale Jolliet Stéphane Nion Gwena?lle Allain-Veyrac L Tilloy-Fenart Dorothée Vanuxeem Vincent Berezowski Roméo Cecchelli 《Pharmacological research》2007,56(1):11-17
PURPOSE: The objective of the current study was to determine the ability of some antiemetic compounds to cross the blood-brain barrier (BBB) and thereby to determine possible side effects of compounds for the central nervous system (CNS). METHODS: We compared the brain penetration of some antiemetic compounds using an in vitro BBB model consisting in brain capillary endothelial cells co-cultured with primary rat glial cells. RESULTS: This study clearly demonstrated that the metopimazine metabolite, metopimazine acid, has a very low brain penetration, lower than metopimazine and even less than the other antiemetic compounds tested in this study. CONCLUSIONS: The poor brain penetration of metopimazine acid, metopimazine biodisponible form, seems very likely related to the clinically observed difference in therapeutic and safety profile. 相似文献
994.
Bone and joint sepsis 总被引:1,自引:0,他引:1
995.
Preclinical and clinical investigations currently underway are employing novel strategies for combining vaccines with conventional and experimental anticancer therapies. To date, the FDA has not approved a therapeutic cancer vaccine. However, the results of recent investigations suggest an increasing role for vaccines in new models of combination therapy for many types of cancer. This article reviews and discusses therapeutic cancer strategies that employ vaccines in combination with local radiation, chemotherapy, hormone therapy, and anti-CTLA-4 mAb. Preclinical studies have shown that certain anticancer agents have immune modulatory effects that result in up-regulation of surface expression of MHC molecules, tumor-associated antigens, or Fas on malignant cells, rendering them more susceptible to immune destruction. Preliminary results of clinical studies using combination strategies have demonstrated a postvaccination antigen cascade, prolonged time to disease progression, and improved overall survival. Several larger randomized trials are ongoing, and more are required to support these findings. 相似文献
996.
997.
998.
V. E. Kataev O. I. Militsina I. Yu. Strobykina G. I. Kovylyaeva R. Z. Musin O. V. Fedorova G. L. Rusinov M. N. Zueva G. G. Mordovskoi A. G. Tolstikov 《Pharmaceutical Chemistry Journal》2006,40(9):473-475
Diesters based on isosteviol and dicarboxylic acids were synthesized and tested for antituberculous activity. Isosteviol and
some of its derivatives exhibit appreciable tuberculostatic properties in vitro, the activity being dependent on the length of the polymethylene spacer connecting two ent-beyeran fragments. The mechanism of the antituberculous action of isosteviol derivatives are discussed.
__________
Translated from Khimiko-Farmatsevticheskii Zhurnal, Vol. 40, No. 9, pp. 12–13, September, 2006. 相似文献
999.
Paul N Bennett Leo Breugelmans Anthony Meade Dee Parkhurst 《Journal of renal nutrition》2006,16(1):59-62
OBJECTIVE: To assess the reliability of a nurse-performed nutrition screening tool (NST) for hemodialysis (HD) patients to identify nutritionally at-risk patients. DESIGN: Tool reliability assessment. SETTING AND PARTICIPANTS: The setting was nine non-hospital private (n = 3) and public (n = 6) HD units in Australia (two rural and seven metropolitan). Participants were 112 HD patients. RESULTS: A total of 112 HD patients (male = 65, female = 47) from 9 non-hospital HD units in Australia (seven metropolitan and two rural) were screened with the NST and the outcome of dietitian referral compared with Standard Dietitians Assessment. The mean age of patients was 57.6 years. Overall, the NST showed a sensitivity of 0.84 (range, 0.71 to 0.94; P < .05) and a specificity of 0.9 (range, 0.82 to 0.98; P < .05). The NST was more sensitive (sensitivity, 0.93 [range, 0.87 to 0.99; P < .05]) and was more specific for men (specificity, 0.92 [range, 0.85 to 0.99; P < .05]). Specificity was very strong in metropolitan patients (specificity, 0.94 [range, 0.87 to 1.01; P < .05]). CONCLUSIONS: The tool was more sensitive and specific than the NST previously reported by the same investigators. The tool is particularly specific in that it screens those patients not requiring dietitian intervention. The use of this tool may benefit HD units that do not have on-site or regular dietetic support to prioritize patients needing dietitian intervention. 相似文献
1000.
Heiko Sch?der Diane L Carlson Dennis H Kraus Hilda E Stambuk Mithat G?nen Yusuf E Erdi Henry W D Yeung Andrew G Huvos Jatin P Shah Steven M Larson Richard J Wong 《Journal of nuclear medicine》2006,47(5):755-762
(18)F-FDG PET has a high accuracy in staging head and neck cancer, but its role in patients with clinically and radiographically negative necks (N0) is less clear. In particular, the value of combined PET/CT has not been determined in this group of patients. METHODS: In a prospective study, 31 patients with oral cancer and no evidence of lymph node metastases by clinical examination or CT/MRI underwent (18)F-FDG PET/CT before elective neck dissection. PET/CT findings were recorded by neck side (left or right) and lymph node level. PET/CT findings were compared with histopathology of dissected nodes, which was the standard of reference. RESULTS: Elective neck dissections (26 unilateral, 5 bilateral; a total of 36 neck sides), involving 142 nodal levels, were performed. Only 13 of 765 dissected lymph nodes harbored metastases. Histopathology revealed nodal metastases in 9 of 36 neck sides and 9 of 142 nodal levels. PET was TP in 6 nodal levels (6 neck sides), false-negative in 3 levels (3 neck sides), true-negative in 127 levels (23 neck sides), and false-positive in 6 levels (4 neck sides). The 3 false-negative findings occurred in metastases smaller than 3 mm or because of inability to distinguish between primary tumor and adjacent metastasis. TP and false-positive nodes exhibited similar standardized uptakes (4.8 +/- 1.1 vs. 4.2 +/- 1.0; P = not significant). Sensitivity and specificity were 67% and 85% on the basis of neck sides and 67% and 95% on the basis of number of nodal levels, respectively. If a decision regarding the need for neck dissection had been based solely on PET/CT, 3 false-negative necks would have been undertreated, and 4 false-positive necks would have been overtreated. CONCLUSION: (18)F-FDG PET/CT can identify lymph node metastases in a segment of patients with oral cancer and N0 neck. A negative test can exclude metastatic deposits with high specificity. Despite reasonably high overall accuracy, however, the clinical application of PET/CT in the N0 neck may be limited by the combination of limited sensitivity for small metastatic deposits and a relatively high number of false-positive findings. The surgical management of the N0 neck should therefore not be based on PET/CT findings alone. 相似文献