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   77081篇
  免费   6716篇
  国内免费   4803篇
耳鼻咽喉   632篇
儿科学   940篇
妇产科学   1387篇
基础医学   8962篇
口腔科学   1287篇
临床医学   10026篇
内科学   12615篇
皮肤病学   897篇
神经病学   4239篇
特种医学   2603篇
外国民族医学   38篇
外科学   8067篇
综合类   11493篇
现状与发展   16篇
预防医学   4727篇
眼科学   2252篇
药学   7668篇
  99篇
中国医学   3717篇
肿瘤学   6935篇
  2024年   884篇
  2023年   1486篇
  2022年   2894篇
  2021年   3629篇
  2020年   2668篇
  2019年   2453篇
  2018年   2473篇
  2017年   2218篇
  2016年   2098篇
  2015年   3175篇
  2014年   3902篇
  2013年   3696篇
  2012年   5333篇
  2011年   5853篇
  2010年   3577篇
  2009年   2873篇
  2008年   3934篇
  2007年   3965篇
  2006年   3916篇
  2005年   3811篇
  2004年   2665篇
  2003年   2495篇
  2002年   2142篇
  2001年   1900篇
  2000年   1989篇
  1999年   2092篇
  1998年   1378篇
  1997年   1289篇
  1996年   955篇
  1995年   863篇
  1994年   799篇
  1993年   491篇
  1992年   736篇
  1991年   638篇
  1990年   580篇
  1989年   510篇
  1988年   421篇
  1987年   401篇
  1986年   302篇
  1985年   269篇
  1984年   155篇
  1983年   99篇
  1982年   67篇
  1981年   74篇
  1980年   46篇
  1979年   73篇
  1978年   38篇
  1976年   32篇
  1975年   32篇
  1974年   40篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
961.
Long-term impact of hepatitis B, C virus infection on renal transplantation   总被引:8,自引:0,他引:8  
Chronic liver disease and its complications are major problems in renal transplant recipients. Our aim was to elucidate the influence of hepatitis B, C virus infection on the long-term outcome of renal transplantation. Four hundred and seventy-seven patients who received renal transplantation between January 1984 and December 1999, and who were followed up at our hospital were enrolled. HBsAg was detected by the RIA method and anti-HCV Ab was assayed by the second-generation RIA kit. SGOT/ SGPT were checked every 3 months. Hepatoma was diagnosed by dynamic CT scan, elevated alpha-fetoprotein, hypervascularity by angiography and confirmed by pathological examination. The prevalence of HBV, HCV, coinfected HBV/HCV was 9.9% (n = 47), 28.5% ( n = 136), 3.1% (n = 15), respectively. The incidences of hepatoma in the HBV-/HCV-, HBV-/HCV+, HBV+/HCV-, HBV+/HCV+ groups were 1.4% (n = 4), 4.4% (n = 6), 6.4% (n = 3), 6.7% (n = 1), respectively (p = 0.114). The incidences of liver cirrhosis/hepatic failure were 3.2% (n = 9), 6.6% (n = 9), 21.3% (n = 10), 20% (n = 3), respectively (p < 0.001). The frequencies of chronic liver disease were 10.4% (n = 29), 45.6% (n = 62), 66% (n = 31), 80% (n = 12), respectively (p < 0.001). Patient and graft survival rates were lower in the HBV-infected group than in the other groups. Cox regression analysis revealed that HBV infection is likely an independent risk factor for patient mortality although the statistical significance was only borderline. Patients with HBV as well as HCV infection were not at risk of graft loss according to this model of analysis. Patients with HBV infection showed higher incidences of hepatoma, hepatic failure, graft failure and death. Therefore, HBV-infected patients who are candidates for renal transplantation should be carefully evaluated. It seems that HCV infection has little influence on the outcome of renal transplant recipients. A longer period of follow-up is needed to clarify the impact of HCV on renal transplant recipients.  相似文献   
962.
Chen WC  Wu HC  Lin WC  Wu MC  Hsu CD  Tsai FJ 《BJU international》2001,88(4):432-436
OBJECTIVE: To evaluate the association of urolithiasis with polymorphic microsatellite (encoding cytosine, adenine, and guanine, CAG) repeats in the exon 1 region of the androgen receptor (AR) gene and thymine/adenine (TA) repeats in the oestrogen receptor (ER). PATIENTS AND METHODS: Patients with urolithiasis (149) and a group of normal controls (102) were examined and compared. The CAG repeats of the AR gene and TA repeats of the ER gene were detected by polymerase chain reaction. The CAG repeats ranged from 171 bp (10 CAG repeats with 141 bp of amplified flanking sequences) to 270 bp (43 CAG repeats). The TA repeats ranged from 160 bp to 194 bp. Associations between calcium oxalate stone disease and the CAG repeats in AR gene and TA repeats in ER gene were then evaluated. The results were classified according to sex and peaks in allelic frequency distribution. RESULTS: There was a significant difference between the male stone patients and the normal controls in the distribution of CAG repeats in the AR gene. Both groups showed a high percentage of 21-repeats in the allelic distribution, at 17 (16%) and 20 (37%) in stone patients and normal controls, respectively. The results indicate that 21-CAG repeats might be related to a lower risk of stone formation in men (P < 0.05). In the ER gene, the peak allelic distribution of TA repeats was 14, showing a significant difference between male stone patients and the normal control subjects (P < 0.01). There were no statistical differences between female stone patients and the control subjects in either the AR or the ER gene. CONCLUSION: Urolithiasis among men appears to be associated with AR gene CAG repeat and ER gene TA repeat polymorphisms, whereas there was no significant association among female stone patients. These sex hormone receptors seem to be related to the higher incidence of stone formation among men.  相似文献   
963.
OBJECTIVE: To investigate the free radicals (FR) generation after ischaemic preconditioning and cardiopulmonary bypass and during reperfusion in CABG patients, and the role of ischaemic preconditioning. METHODS: Forty-three CABG patients were randomised into an ischaemic preconditioning and a control group. The protocol for ischaemic preconditioning was two cycles of 2-min ischaemia followed by 3-min reperfusion. Free radicals were measured using electron spin resonance spectroscopy. Global and right heart functions were collected. RESULTS: The free radicals generation in coronary sinus blood in the ischaemic preconditioning group was 9.7 and 16.6% after the ischaemic preconditioning protocol and 10 min after declamping, 6.8 and 13.3% in the controls. The free radicals in arterial samples were, respectively, 21, 14, 10 and 9% at 10 min, 1, 2 and 24 h after reperfusion. Cardiac index (CI) and right ventricular ejection fraction (RVEF) were improved by ischaemic preconditioning. CONCLUSION: Both ischaemic preconditioning and cardiopulmonary bypass induced free radicals generation. Although ischaemic preconditioning had no effect on free radicals generation after the operation, it protected against postoperative stunning.  相似文献   
964.
BACKGROUND: Many successful attempts at removing benign mediastinal tumors with the video-assisted thoracoscopic technique have been reported, but no formal report has been published regarding malignant mediastinal tumors treated with this technique. We report our preliminary experience with video-assisted thoracoscopic removal of mediastinal tumors, benign or malignant. METHODS: Seven patients with mediastinal tumors treated with video-assisted thoracoscopic surgery were reviewed from January 1999 to April 2000. Their tumor pathologies included benign or malignant thymoma, neurilemmoma, and teratoma. RESULTS: The mean operation time was 240 minutes. The mean blood loss was 173 mL. The mean insertion time of chest tubes was 3 days. The mean admission time was 6 days. No deaths occurred during the study. Morbidity occurred in 2 patients. No tumor recurrence has been seen during the mean follow-up of 7 months. CONCLUSIONS: The short-term results support the feasibility of VATS in managing technically resectable mediastinal tumors. Yet the long-term prognosis for the malignant lesions is deferred and needs further study.  相似文献   
965.
目的 观察安信医用抗菌贴对慢性难愈合创面(溃疡)的促修复作用并探讨其修复机制。方法 34例共44个慢性难愈合创面,其中创伤性溃疡15例(23个创面),压迫性溃疡9例(11个创面),糖尿病溃疡5例,放射性溃疡5例。所有创面经清创后用安信医用抗菌贴外敷于创面,每2-3天更换一次。结果 所有经安信医用抗菌贴治疗的创面都明显愈合,其中2周内愈合26个创面,3周内愈合7个创面,4周内愈合9个创面,超过4周愈合2个创面。4周内总愈合率炎95.5%。结论 安信医用抗菌贴可以显著地加速慢性难愈合创面的愈合,其机制为广谱速效杀菌,改善局部微循环,有效激活并促进组织细胞生长。  相似文献   
966.
We treated 116 healthy postmenopausal women (age 47–66 years, mean 57 years) in Taiwan with either raloxifene (RLX) 60 mg (n= 92) or 0.625 mg conjugated equine estrogen plus 5 mg medroxyprogesterone acetate (CCEP, n= 24) daily for 12 months in a randomized, double-masked, active-controlled fashion. The results showed that both regimens increased bone mineral density (BMD) at hip sites (means: RLX 2.5–4.9%, CCEP 4.6–7.9%, all p<0.005 compared with baseline), and the difference between the two regimens was not significant. The spinal BMD increased significantly in both groups (1.4% with RLX and 6.0% with CCEP, both p<0.01), and more with CCEP (p<0.003). Osteocalcin levels and urinary type I collagen C-telopeptide/creatinine ratios decreased significantly in both regimens, but the decreases were significantly larger with CCEP. Compared with baseline, both RLX and CCEP decreased the total cholesterol (median 4.9% and 8.6% respectively, p<0.001) and LDL-cholesterol (median 11% and 19% respectively, p<0.001), and increased HDL-cholesterol (median 8.6% and 10.7% respectively, p<0.01). Both regimens increased triglyceride levels (median 3.2% and 18.9% respectively, both p<0.05), although to a lesser extent with RLX than with CCEP (p<0.05). Only 3 subjects (3.3%) reported vaginal bleeding in the RLX group, as compared with 31% (7/22) with CCEP (p<0.05). We conclude that in healthy, postmenopausal Taiwanese women, RLX 60 mg given daily has favorable results in BMD, bone turnover and serum lipids, although the dosage we used showed a potency less than that of conventional CCEP. Received: 22 November 2000 / Accepted: 25 June 2001  相似文献   
967.
BACKGROUND: Sodium hyaluronate has been used intraperitoneally to prevent postoperative adhesions. However, the effect of sodium hyaluronate on tumour growth and metastasis in vitro and in vivo is still unknown. METHODS: Human colorectal tumour cell lines SW480, SW620 and SW707 were treated with sodium hyaluronate (10-500 microg/ml) and carboxymethylcellulose (0.125-1 per cent), and tumour cell proliferation and motility were determined in vitro. For the in vivo experiments male BD IX rats were randomized to a sodium hyaluronate group (n = 11; intraperitoneal administration of 0.5 x 10(6) DHD/K12 tumour cells and 5 ml 0.4 per cent sodium hyaluronate) or a phosphate-buffered saline group (n = 11; 0.5 x 10(6) DHD/K12 tumour cells and 5 ml phosphate-buffered saline intraperitoneally). Four weeks later the intraperitoneal tumour load was visualized directly. RESULTS: In vitro sodium hyaluronate increased tumour cell proliferation and motility significantly. Sodium hyaluronate-induced tumour cell motility appeared to be CD44 receptor dependent, whereas sodium hyaluronate-induced tumour cell proliferation was CD44 receptor independent. In vivo there was a significantly higher total tumour nodule count in the peritoneal cavity of the sodium hyaluronate-treated group compared with the control (P = 0.016). CONCLUSION: Sodium hyaluronate enhances tumour metastatic potential in vitro and in vivo, which suggests that use of sodium hyaluronate to prevent adhesions in colorectal cancer surgery may also potentiate intraperitoneal tumour growth. Presented to the Patey Prize Session of the Surgical Research Society and the annual scientific meeting of the Association of Surgeons of Great Britain and Ireland, Brighton, UK, 4-7 May 1999  相似文献   
968.
Heart transplant patients are reported to have impaired regulation of the microvasculature. The purpose of this study was to investigate the cutaneous blood flow and its reactivity to sodium nitroprusside (vasodilator, Nipride 0.1%) and norepinephrine (vasoconstrictor, Levophed 0.1%) in patients after heart transplantation in comparison to normal healthy individuals. Eighteen patients after heart transplantation and 16 healthy, nonsmoking individuals served as subjects of the study. Sodium nitroprusside and norepinephrine were introduced by iontophoresis to the skin of the right and left forearms, respectively. After measuring cutaneous blood flow reactivity in the pre-exercise state by laser Doppler flowmetry, subjects were then asked to close and open their fists for 2 min. The same measurements were repeated after exercise. Comparisons between the groups were carried out by the Wilcoxan signed rank test. The Mann Whitney U-test was used for comparison between pre-exercise and post-exercise states. The results demonstrated that sodium nitroprusside significantly increased forearm cutaneous perfusion at rest but produced only a mild increase after exercise. This reactivity was significantly lower after exercise with no significant differences between groups. Norepinephrine decreased cutaneous blood flow at rest. The transplant patients were significantly less sensitive to norepinephrine before but not after exercise. The changes in norepinephrine reactivity with exercise were significantly different between groups (p < 0.05).  相似文献   
969.
目的:探讨电视腹腔镜行子宫次全切除术的临床应用。方法:对50例年龄小于50岁患有子宫良性病且有子宫切除手术指征患者行电视腹腔镜子宫次全切除术,子宫经阴道后穹窿取出。结果:改良电视腹腔镜子宫次全切除术兼有剖腹及阴道手术的优点,组织损伤及感染机会少,手术时间缩短,术中失血量减少,术后康复快。结论:应用电视腹腔镜行改良阴式子宫次全切除术经济方便。  相似文献   
970.
To identify risk factors for fractures in multi-ethnic women, we studied 159,579 women enrolled in the Women's Health Initiative. In general, risk factors for fractures were similar across ethnic groups. However, irrespective of their ethnicity, women with multiple risk factors have a high risk of fracture. Targeting these high-risk women for screening and intervention could reduce fractures. INTRODUCTION: Fracture rates tend to be lower in minority women, but consequences may be greater. In addition, the number of fractures is expected to increase in minority women because of current demographic trends. There are limited prospective data on risk factors for fractures in minority women. MATERIALS AND METHODS: We studied 159,579 women 50-79 yr of age enrolled in the Women's Health Initiative. Information on risk factors was obtained by questionnaire or examination. Nonspine fractures that occurred after study entry were identified over an average follow-up of 8 +/- 2.6 (SD) yr. RESULTS: Annualized rates (%) of fracture in whites, blacks, Hispanics, Asians, and American Indians were 2.0, 0.9, 1.3, 1.2, and 2.0, respectively. Significant predictors [HR (95% CI)] of fractures by ethnic group were as follows: blacks: at least a high school education, 1.22 (1.0, 1.5); (+) fracture history, 1.7 (1.4, 2.2); and more than two falls, 1.7 (1.9, 2.0); Hispanics: height (>162 cm), 1.6 (1.1, 2.2); (+) fracture history, 1.9 (1.4, 2.5); more than two falls, 1.8 (1.4, 2.3); arthritis, 1.3 (1.1, 1.6); corticosteroid use, 3.9 (1.9, 8.0); and parental history of fracture, 1.3 (1.0, 1.6); Asians: age (per 5 yr), 1.2 (1.0, 1.3); (+) fracture history, 1.5 (1.1, 2.0); current hormone therapy (HT), 0.7 (0.5, 0.8); parity (at least five), 1.8 (1.1, 3.0); more than two falls, 1.4 (1.1, 1.9); American Indian: (+) fracture history, 2. 9 (1.5, 5.7); current HT, 0.5 (0.3, 0.9). Women with eight or more risk factors had more than a 2-fold higher rate of fracture compared with women with four or fewer risk factors. Two ethnicity x risk factor interactions were identified: age and fall history. CONCLUSIONS: Irrespective of their ethnicity, women with multiple risk factors have a high risk of fracture. Targeting these high-risk women for screening and intervention could reduce fractures.  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