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   1475篇
  免费   56篇
  国内免费   7篇
耳鼻咽喉   23篇
儿科学   6篇
妇产科学   26篇
基础医学   185篇
口腔科学   9篇
临床医学   86篇
内科学   276篇
皮肤病学   33篇
神经病学   90篇
特种医学   46篇
外科学   348篇
综合类   7篇
预防医学   61篇
眼科学   28篇
药学   143篇
中国医学   9篇
肿瘤学   162篇
  2023年   5篇
  2022年   25篇
  2021年   34篇
  2020年   18篇
  2019年   23篇
  2018年   22篇
  2017年   11篇
  2016年   26篇
  2015年   29篇
  2014年   27篇
  2013年   40篇
  2012年   60篇
  2011年   60篇
  2010年   33篇
  2009年   37篇
  2008年   100篇
  2007年   80篇
  2006年   94篇
  2005年   97篇
  2004年   105篇
  2003年   108篇
  2002年   102篇
  2001年   30篇
  2000年   49篇
  1999年   34篇
  1998年   25篇
  1997年   17篇
  1996年   10篇
  1995年   15篇
  1994年   7篇
  1993年   10篇
  1992年   29篇
  1991年   14篇
  1990年   20篇
  1989年   20篇
  1988年   14篇
  1987年   12篇
  1986年   9篇
  1985年   8篇
  1984年   10篇
  1983年   6篇
  1981年   4篇
  1979年   4篇
  1977年   6篇
  1976年   6篇
  1975年   4篇
  1974年   4篇
  1971年   3篇
  1970年   9篇
  1968年   5篇
排序方式: 共有1538条查询结果,搜索用时 15 毫秒
71.
We describe a modified arch-first technique for total arch replacement through median sternotomy. This technique involves a short period of circulatory arrest (less than 30 minutes) and subsequent anterior cerebral perfusion. It does not require cannulation of the carotid vessels, which can cause cerebral thromboembolism, and it enables anterior cerebral perfusion to be resumed after a relatively short period of circulatory arrest. This appears to be a useful technique to reduce cerebral complications in complicated arch reconstruction operation for patients with severely atherosclerotic carotid vessels.  相似文献   
72.
A follow-up study was conducted on 5725 inhabitants (men 2858, women 2867) in and around the Jinzu River basin to determine the influence of environmental Cd exposure on mortality. In the Jinzu River basin, standardized mortality ratios (SMRs) investigated according to urinary findings (protein, glucose, and protein+glucose) were significantly low in the urinary protein-, glucose-, and protein+glucose-negative groups. SMRs calculated after dividing urinary protein- and glucose-positive status into two levels were lowest in the proteinuria- and glycosuria-negative groups and tended to be high in the higher positive groups. In the Jinzu River basin, Cox's hazard ratios were significantly higher for men and women in the urinary protein, glucose and protein+glucose-positive-groups. In the same analysis where the urinary protein- and glucose-positive subjects were divided into two levels, mortality was demonstrated to be higher in the groups with the greater degrees of proteinuria and glycosuria. In the Jinzu River water system almost all SMRs and Cox's hazard ratios showed statistical significance. This was not the case in the other water systems. Mortality of inhabitants with Cd-induced renal injury is increased in the Jinzu River basin.  相似文献   
73.
BACKGROUND: Patients with recurrent soft tissue sarcoma (STS) are seldom curable, with 5-year survival rates of less than 10% in all large series. The role of high-dose chemotherapy (HDC) with hematopoietic stem cell support in this disease has not been established. CASE REPORT: We report on two patients with recurrent STS who were treated with tandem HDC supported by autologous peripheral blood stem cell transplantation (PBSCT). One patient with malignant fibrous histiocytoma recurred with multiple lung metastases. This patient achieved a partial response after two cycles of induction chemotherapy consisting of ifosfamide and epirubicin. During four cycles of induction chemotherapy, peripheral blood stem cells (PBSCs) were harvested. Tandem high-dose ICE regimen (ifosfamide 3 g/m2 on days-7 to -3, carboplatin 400 mg/m2 on days-7, -5 and 3, etoposide 500 mg/m2 on days-7, -5 and 3) supported by autologous PBSCT gave rise to further regression of the tumors. Another patient with malignant hemangiopericytoma was treated by tandem high-dose ICE regimen supported by autologous PBSCT after the 3rd removal of abdominal tumors. Relapse-free intervals until the 1st, 2nd and 3rd relapses were 40, 19 and 22 months, respectively. Tandem high-dose ICE regimen might delay the relapse. CONCLUSION: These observations suggest that a tandem high-dose ICE regimen with autologous PBSCT is feasible with some clinical efficacy in the control of refractory STS.  相似文献   
74.
We have investigated the cell growth inhibitory effects of crude catechin (catechin) containing approximately 53% of epigallocatechin-3-gallate (EGCG) on the human breast cancer cell line T47D, and the mechanism of its action, with emphasis on the cell cycle and mitogen-activated protein kinases (MAPK). A significant dose-dependent growth inhibition was observed after treatment with catechin. At 48 h after the addition of catechin, cells at the G2/M phase were increased by 8.3%, compared with the control. Analysis of the expression of cell cycle-related proteins after the addition of catechin showed that the cyclin-dependent kinase (cdk) 2 and the cdk4 proteins were decreased after administration, the expression of cyclin A protein was increased at 24 h after administration, however, the expression of the cyclin D1 and cyclin E proteins was unchanged. At 24 h after the administration of catechin, the phosphorylation of cell division cycle 2 (cdc2) was inhibited, and the expression of cyclin B1 protein was also decreased. Furthermore, the analysis of the MAPK expression showed that the phosphorylated JNK/SAPK protein began to increase at 3 h after catechin administration, and the expression persisted until 24 h after administration, then decreased. The phosphorylation of p38 protein was increased at 12 h, and began to decrease at 36 h after catechin administration. Based on these results, we speculate that, in the breast cancer cell line T47D, catechin phosphorylated JNK/SAPK and p38, and that the phosphorylated JNK/SAPK and p38 inhibited the phosphorylation of cdc2, and regulated the expression of cyclin A, cyclin B1, and cdk proteins, thereby causing G2 arrest. The results suggested that catechin (EGCG) may be an effective adjuvant therapy after breast cancer surgery.  相似文献   
75.
Various substances have been introduced in relation with cardiac hypertrophy almost always with controversy in their roles in signal transduction. Those controversies may attribute to the diversity of cardiac hypertrophy. We previously showed that calcineurin was activated in physiological left ventricular hypertrophy (LVH) induced by voluntary exercise training, but not in decompensated pressure-overload LVH. In the current study, we advanced our search for the differences between the voluntary exercise-induced LVH and the pressure-overload LVH into several other hypertrophy-related substances including caveolin. Wistar rats were assigned to one of the following three groups: 10 weeks of voluntary exercise (EX), sedentary regimen (SED), and 4 weeks of ascending aortic constriction (AC). The EX rats voluntarily ran 1.6 ± 1.1 km/day in the specially manufactured cages resulting in LVH (24 % increase in left ventricular weight per body weight ratio). Myocardial tissue homogenate of the EX rats revealed different characteristics in signal transduction of hypertrophy from that of the AC. The EX rats had normal sarcoplasmic reticulum (SR) Ca2+ATPase mRNA level and normal myosin heavy chain isozyme pattern assessed by RNA protection assay, while AC rats had decreased SR Ca2+ATPase mRNA level and increased beta myosin heavy chain mRNA level. Myocardial caveolin-3 protein levels assessed by Western blotting increased in the EX rats but decreased in the AC rats. The voluntary exercise-induced LVH differed in signal transduction from the decompensated pressure-overload LVH. Caveolin-3 was induced in the voluntary exercise-induced LVH, while it was decreased in the decompensated pressure-overload LVH.Key Words: Exercise, hypertrophy, signal transduction  相似文献   
76.
Short- and long-term experiments were designed to determine the effects of toremifene (TOR) on estrogen-related endometrial carcinogenesis in mice. In the short-term experiment, a single low dose of TOR (0.2 mg/30 g body weight) decreased expression of c- fos , interleukin (IL)-1α, estrogen receptor (ER)-α mRNAs and corresponding proteins induced by estradiol-l7β (E2), in the uteri of the ovariectomized mice. Expression of ER-β mRNA was increased by the TOR treatment, compared with the control. In the long-term experiment, 106 female ICR mice were given N -methyl N -nitrosourea (MNU) into their uterine corpora. The animals were divided into four groups as follows: group 1, E2 diet (5 ppm) plus TOR (0.2 mg/30 g body weight, subcutaneously, every four weeks); group 2, E2 diet alone; group 3, basal diet plus TOR. Group 4 served as the control. TOR treatment decreased the incidence of MNU and E2-induced endometrial adenocarcinoma and atypical hyperplasia at the termination of the experiment (30 weeks after the start). These results suggest that TOR exerts preventive effects against estrogen-related endometrial carcinogenesis in mice, through the suppression of c- fos as well as IL-1α expression induced by E2. Such suppressive effects of TOR may be related to the decreased ER-α and increased ER-β expressions.  相似文献   
77.
The radioactivity in the organs adjacent to the heart causes interference with the quantitative assessment of myocardial uptake of tracer on scintigraphy. In order to investigate how much the functions of these organs affect myocardial uptake seen in imaging, we compared the myocardial uptake measured by means of a gamma camera with the actual activity in the excised organs. Methods: Thirty-three rats were imaged at 5, 10, 15, 30, 45, 60, 90 and 120 min after the administration of 99mTc-tetrofosmin, and % injected dose per pixel (%ID/pixel) for each organ was assessed on planar images (PI measurement). Percent injected dose per gram of tissue (%ID/g) in the heart as well as lungs, liver, gastrointestines and blood was measured by means of a well scintillation counter (WC measurement). Comparison between PI and WC measurements was performed with % uptake, the PI-to-WC ratio and heart-to-organ ratios. Results: Our WC measurement showed an increase in cardiac uptake until 30 min (1.67 +/- 0.31%) postinjection and subsequent gradual decrease, whereas PI measurement showed maximum activity of 1.81 +/- 0.52% at 15 min postinjection. There was a prominent difference between the two measurements, particularly at 10 min, with a PI/WC ratio of about 1.6 times. Our WC measurement showed maximum pulmonary uptake at 15 min (0.87 +/- 0.31%) and a gradual decrease over 15 min, whereas PI measurement showed maximum uptake at 10 min (1.14 +/- 0.38%). There was hardly any variation in activity observed later than at 10 min. Our WC measurement showed hardly any variance in hepatic activity from 5 min (0.77 +/- 0.19%) to 30 min (0.69 +/- 0.27%) with a subsequent gradual decrease. The percent uptake in PI measurement was generally greater than that in WC measurement, and high values were found at 10 min and 15 min with PI/WC ratios of about 3.3 times and 2.3 times, respectively. Conclusion: Percent uptakes in PI measurement were greater than those in WC measurement. The difference between the two measurements was prominent in the early phases. The cardiac uptake in PI measurement was significantly greater than that in WC measurement at 10 min. It was considered that this discrepancy between the two measurements was caused by the Compton scatter from the organs adjacent to the heart.  相似文献   
78.
Endodermal sinus tumor is a rare and highly malignant lesion. This report documents the clinical findings and magnetic resonance imaging (MRI) of an uncommon case of the endodermal sinus tumor arising in the vagina of a 6-month-old infant. MRI was extremely accurate in delineating the possible extent and location of the vaginal lesion. This is the first report to demonstrate MRI of vaginal endodermal sinus tumor.  相似文献   
79.
The present study was undertaken to examine the effects of estrogens, such as estrone (E1), 17β-estradiol (E2) and estriol (E3), on endometrial Carcinogenesis initiated by N-methyl-N-nitrosourea (MNU) in mice. A total of 120 female ICR mice received MNU solution (1 mg/100 g body wt.) and normal saline at 10 weeks of age into their left and right uterine corpora, respectively. One week later, they were divided into four groups and treated as follows: Group 1 (30 mice) was given 25 ppm E1-containing diet; Group 2 (30 mice) was fed 5 ppm E2-containing diet; Group 3 (30 mice) was given 25 ppm E3-containing diet; and Group 4 (30 mice) was fed the basal diet alone. At the termination of the experiment (Week 30), all surviving animals were autopsied and histopathological examinations revealed that endometrial adenocarcinomas had developed in all groups. The incidence of adenocarcinomas in the MNU-treated uterine corpus in Group 1 (25 ppm E1-feeding, 9/23, 39%) was significantly higher than that in Group 4 (basal diet, 3/26, 12%, P<0.05). Also, the incidences of adenocarcinomas in the MNU-treated uterine corpus in Groups 2 (5 ppm E2-feeding, 8/24, 33%) and 3 (25 ppm E3-feeding, 7/26, 28%) were higher than in Group 4, but the difference was not statistically significant. Feeding of diet containing E1, E2 and E3 increased the incidences of the preneoplastic endometrial lesions (atypical, adenomatous or cystic glandular hyperplasia). In the uterine cervix, small numbers of squmous cell carcinomas, dysplasias or hyperplasias were occasionally found in all groups. These results indicate enhancing effects of the above three types of estrogens on the endometrial carcinogenesis induced by MNU in ICR mice.  相似文献   
80.
BACKGROUND: The herbicide BASTA (AgrEvo, Germany), containing glufosinate ammonium (20%) and an anionic surfactant, polyoxyethylene alkylether sulfate (33%), is widely used. In acute oral BASTA poisoning, patients develop a variety of clinical signs, including disturbed consciousness, convulsions, and apnea. These effects are suspected to be due to the effects of glufosinate on the central nervous system. CASE REPORT: A 60-year-old man ingested 500 mL of BASTA herbicide in a suicide attempt. He developed not only unconsciousness, respiratory distress, and convulsions but also an increase in urine output (7885 mL/d), elevated serum sodium (167 mEq/L), elevated plasma osmolality (332 mOsm/kg), and a decrease in both urine osmolality (200 mOsm/kg) and urine specific gravity (1.003), which suggested the development of diabetes insipidus. The plasma level of antidiuretic hormone remained within the normal range (1.3 pg/mL), despite high plasma osmolality. The administration of desmopressin was successful in normalizing urine volume, specific gravity, and osmolality. Serum sodium corrected gradually within 48 hours. The possible mechanisms causing the diabetes insipidus are discussed.  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