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   1628篇
  免费   98篇
  国内免费   5篇
耳鼻咽喉   39篇
儿科学   64篇
妇产科学   29篇
基础医学   182篇
口腔科学   19篇
临床医学   127篇
内科学   340篇
皮肤病学   124篇
神经病学   79篇
特种医学   15篇
外科学   243篇
综合类   47篇
一般理论   1篇
预防医学   93篇
眼科学   18篇
药学   194篇
中国医学   5篇
肿瘤学   112篇
  2023年   12篇
  2022年   23篇
  2021年   36篇
  2020年   34篇
  2019年   34篇
  2018年   48篇
  2017年   31篇
  2016年   36篇
  2015年   33篇
  2014年   49篇
  2013年   58篇
  2012年   92篇
  2011年   104篇
  2010年   62篇
  2009年   54篇
  2008年   92篇
  2007年   83篇
  2006年   76篇
  2005年   43篇
  2004年   47篇
  2003年   51篇
  2002年   53篇
  2001年   62篇
  2000年   58篇
  1999年   53篇
  1998年   19篇
  1997年   13篇
  1996年   24篇
  1995年   16篇
  1994年   13篇
  1993年   11篇
  1992年   29篇
  1991年   23篇
  1990年   26篇
  1989年   19篇
  1988年   28篇
  1987年   15篇
  1986年   15篇
  1985年   10篇
  1984年   12篇
  1983年   11篇
  1982年   6篇
  1980年   7篇
  1979年   15篇
  1978年   14篇
  1977年   8篇
  1976年   7篇
  1975年   8篇
  1974年   9篇
  1973年   11篇
排序方式: 共有1731条查询结果,搜索用时 46 毫秒
21.
Factors contributing to low birth weight (LBW) include poverty, ignorance, and inability to use health care services. Early marriage and low family income lead to poor maternal nutrition reserves, which lead to reduced fetal nutrition. Poor maternal nutrition is also the result of ignorance, short birth intervals, multi-parity, and lack of prenatal care. Both heavy manual labor and smoking contribute to placental ischemia, which, along with reduced fetal nutrition, leads to intrauterine growth retardation (IUGR). In developing countries, IUGR accounts for over 66% of all LBW neonates. About 7 million Indian babies annually are LBW. This study examined the incidence of LBW among 178 mothers delivering single births at the maternity hospital associated with the Department of Community Medicine of SKIMS, Srinagar, Kashmir, India, during 1989-90. 26.40% (47) of the 178 births were LBW (2500 g). Among 71 first-borns, marriage age was found to be statistically significantly associated with LBW. 31.82% of mothers younger than 20 years had LBW babies, compared to only 6.12% of mothers older than 20 years. The impact ratio, which measured excess LBW, was 4.20. Birth interval was statistically significantly associated with LBW outcome. 55.81% of women with a birth interval of less than 18 months had LBW babies, compared to 20.31% of mothers with longer birth intervals. The impact ratio was 1.75. Gravidity was also statistically associated with LBW babies. 34.58% of multigravida mothers had LBW babies, compared to 14.08% of primigravidae. The impact ratio was 1.46. Presence of prenatal care was statistically associated; the impact ratio was 1.42. 31.30% of illiterate women had LBW babies, compared to only 17.46% among literate women, which indicated significant associations with LBW. Other significant factors were manual labor, maternal smoking, and monthly family income. Reduction of LBW by 10-30% nationally by the year 2000 will be difficult and best accomplished by a high risk approach supplemented by health and nutrition education.  相似文献   
22.
Epidemiology is emerging as a promising tool for understanding and interpreting diseases in all dimensions and identifying levels of intervention for their control or eradication. Coupled with the discipline of health administration and management, epidemiology can offer viable and pragmatic solutions for tackling disease problems. Eradication of small pox in the recent past and the formulation of a strategy for the control of the modern epidemic of AIDS are 2 best known examples. An epidemiological approach to acute respiratory tract infection (ARI) in children can improve the understanding of the disease and help to prepare the ground for effective control. The principal areas of epidemiology are natural history, intervention strategy, and epidemiological inquiry. The principal viruses that have been identified to lead to ARI infection on the basis of systematic studies are rhinoviruses (100 different serotypes), parainfluenza viruses (several serotypes), respiratory syncytial virus, adenoviruses (about 8 important serotypes in children), enteroviruses (ECHO and Coxsackie with more than 70 serotypes), herpes simplex virus, measles virus, and Epstein-Barr virus. Based on the natural history of ARI, the scope of application of the 5 levels of intervention may be discussed individually as health promotion, specific protection, early diagnosis and prompt treatment, disability limitation, rehabilitation, and epidemiological inquiry. Epidemiological techniques may contribute substantially to the understanding and management of ARI control by: a) defining the ARI problem and its magnitude and behavior in relation to time, place, and person; b) identifying the epidemiological correlates of ARI in terms of agent, host, and environment, and their impact on morbidity and mortality in children; c) introducing epidemiological surveillance and monitoring techniques for effective supervision of intervention activities; and d) conducting longitudinal observational studies to evaluate efficiency and effectiveness of various intervention alternatives for ARI control.  相似文献   
23.
Seventy-eight patients (85 affected hips and 71 unaffected hips) with Legg-Calvé-Perthes disease were included in this study to evaluate the metaphyseal change in radiographs and magnetic resonance imaging (MRI) and to define the type of the metaphyseal cyst according to presence or absence of the epiphyseal involvement. The content of the metaphyseal cyst was evaluated by using T1,T2, proton, and gadolinium-enhanced T1-weighted MRI scans. Among 85 hips, there were no changes in 32 hips, marrow edema in 13 hips, false cyst with epiphyseal involvement in 28 hips, and true cyst without epiphyseal involvement in 12 hips. Granulation tissue was found in the false cysts and water-rich fibrotic tissue was found in the true cysts based on the MRI scans. The metaphyseal change in MRI scans was shown in 71% of groups 3 and 4 and in 35% of groups 1 and 2 according to the Catterall classification, and 52% of group A, 56% of group B, and 86% of group C according to the Herring classification. Of the 30 hips at the avascular stage, 33% showed metaphyseal cyst in MRI scans. Of the 53 hips at the fragmentation stage, 60% showed the metaphyseal cyst.  相似文献   
24.
PURPOSE: Angiogenesis plays an important role in a multitude of biological processes including those of tumorigenesis and cancer progression. Hypoxia is the prime driving factor for tumor angiogenesis and the family of hypoxia-inducible factors (HIFs) plays a pivotal role in this process. The role of HIF in tumor angiogenesis has been underscored in different carcinomas but yet to be reported for colorectal carcinomas. EXPERIMENTAL DESIGN: In this study, we examined HIF [HIF-1alpha (HIF1) and HIF-2alpha (HIF2)] expression in 87 curatively resected colorectal carcinoma samples, and the results were correlated with clinicopathological factors, microvessel density, cyclooxygenase 2 expression, and patient prognosis. RESULTS: HIF1 (44.8%) was more frequently expressed than HIF2 (29.9%). Most of the clinicopathological factors representing the tumor aggressiveness were significantly correlated with overexpression of HIF2 but not with HIF1 expression. HIF2 expression had direct correlation with microvessel density and cyclooxygenase 2 expression. and, in contrast, HIF1 expression had a weak but significant inverse correlation in T1 and T2 tumors only. HIF2 expression alone and the combined expression of HIF1 and HIF2 had significant impact on patient survival. In the multivariate analysis, however, only the combined expression of HIF1 and HIF2 remained independently significant. CONCLUSIONS: Taken together, our results suggest that HIF2 expression may play an important role in angiogenesis and that the combined expression of HIF1 and HIF2 may play an important role in tumor progression and prognosis of colorectal carcinomas. Therefore, HIF expression could be a useful target for therapeutic intervention.  相似文献   
25.
Imaging spectrum in sclerotic myelomas: an experience of three cases   总被引:2,自引:0,他引:2  
Grover SB  Dhar A 《European radiology》2000,10(11):1828-1831
The classic radiographic presentation of multiple myeloma is lytic skeletal lesions. Primary sclerotic manifestations are rare and occur only in 3 % of cases. The imaging spectrum in three cases of multiple myeloma with primary osteosclerosis is described. The first patient had spiculated sclerosis of the orbit, which is an uncommon site for myeloma. The second patient with POEMS syndrome had multiple, scattered, skeletal lesions with sclerotic margins. The third patient presented with a chest wall mass and had an expansile thick spiculated sclerosis in the rib. The wide imaging spectrum possible in sclerotic myelomas and their relevant differential diagnosis is emphasized. Received: 14 March 2000; Accepted: 25 April 2000  相似文献   
26.
BACKGROUND: The incidence of gastric neoplasm is increasing in the elderly population. Therefore, a rational method of treatment for gastric cancer in the elderly should be constituted to improve the survival. The purpose of the present study was to clarify whether the patient's age is an independent prognostic factor and to determine clinicopathological characteristics in the elderly. METHODS: Curative resection of gastric cancer was carried out on 601 patients who were 40 years or older. They were divided into the following two groups: younger patients (between 40 and 79 years old) and elderly patients (80 years or older). The clinicopathologic features of these patients were reviewed retrospectively and multivariate analysis was carried out. RESULTS: The distinguishing features of gastric cancer in the elderly patients were intestinal and mixed types of cancer, distal third stomach dominance in the tumour location, advanced stage of disease, and a low rate of extensive lymph node dissection (D3 or more). Regarding the recurrence site, the liver was the dominant site in the elderly group (25.3% in the younger group vs 54.5% in the elderly group). The 10-year disease-free survival rate of the elderly group was 53.2%, which was significantly worse than that (79.9%) of the younger patients (P = 0.0004). In multivariate analysis, an age of > or = 80 years is an independent prognostic factor, as well as stage, depth of tumour invasion, lymph node metastasis, scirrhous carcinoma, and blood transfusion. CONCLUSIONS: Results indicate that gastric cancer in elderly patients has a poorer prognosis than that in younger patients.  相似文献   
27.
We report an unusual clinical presentation of Lyme carditis in a previously healthy 20-year-old black woman without any epidemiologic history of Lyme disease, fulminant in nature, involving a heart valve necessitating emergent mitral valve replacement, and requiring further surgical intervention because of the development of pericardial effusion and tamponade. A dilated right ventricle with normal contractility and severe tricuspid regurgitation with increase in the right atrial size diagnosed later remains under close surveillance.  相似文献   
28.
The series of vasicine (1) analogues, an alkaloid from Adhatoda vasica Nees., were synthesized with changes in A, B or C rings. Compounds 13-19 were evaluated for in vitro bronchodilatory activity using isolated guinea pig tracheal chain. Compounds 3-8 were also synthesized in good yields using microwave-mediated synthesis under solvent free conditions. Compounds 5 and 8 with seven-member C ring were more active than etofylline and caused 100% relaxation of both the histamine and acetycholine pre-contracted guinea pig tracheal chain. The structure-activity relationship studies showed that the quinazoline and oxo functionalities were essential for activity. The compounds without C ring and instead having aliphatic and phenyl substitutions in B ring showed relaxation against histamine pre-contracted tracheal chain only, 2-methyl substituted analogues, 12 and 13, being most active with 100% relaxation effect.  相似文献   
29.
BACKGROUND: Detection of gastric cancer in an early stage is important to improve the prognosis of patients with gastric cancer. This study compared the clinicopathologic characteristics and surgical results in patients with asymptomatic gastric cancer detected by a screening program with those of patients with symptomatic cancer. The efficacy of 2 screening methods (barium meal and endoscopy) was also compared. METHODS: The subjects included 196 patients with asymptomatic gastric cancer detected by screening (screening group) and 612 patients with symptomatic gastric cancer (nonscreening group) treated from 1979 to 1997. The screening group was subdivided into the barium meal study group (n = 150) and the endoscopic study group (n = 46). RESULTS: The incidences of early gastric cancer and 5-year survival rates between the screening and nonscreening groups were 77% versus 29% (P <.0001) and 81% versus 44% (P <.0001), respectively. The endoscopic study appeared to be able to detect smaller gastric cancer in an earlier stage compared with the barium meal study, although no statistical differences in survival rate were noted between these 2 screening methods. CONCLUSIONS: Screening plays an important role in detecting gastric cancer in an early stage and in potentially reducing death attributable to gastric cancer. Endoscopic screening is recommended as the best screening method.  相似文献   
30.
In the context of infections in the body, those that occur in the gynaecological tract are less common and perhaps less clinically significant compared with other body sites. However, a few infections are important in view of their association with pathological sequelae such as tumour formation or pelvic inflammatory disease complex.This review will discuss some of the most relevant infections, first under histology, which will be further subdivided into locations in the genital tract and then under cytology, which focuses mainly on the infections seen in cervical cytology samples. There will be only brief mention of the less common infections or those that do not produce diagnostic challenges or lead to significant complications.  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