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   6698篇
  免费   402篇
  国内免费   6篇
耳鼻咽喉   60篇
儿科学   271篇
妇产科学   193篇
基础医学   989篇
口腔科学   83篇
临床医学   504篇
内科学   1603篇
皮肤病学   120篇
神经病学   573篇
特种医学   220篇
外科学   779篇
综合类   21篇
一般理论   1篇
预防医学   618篇
眼科学   79篇
药学   387篇
中国医学   17篇
肿瘤学   588篇
  2023年   37篇
  2022年   62篇
  2021年   159篇
  2020年   103篇
  2019年   152篇
  2018年   219篇
  2017年   113篇
  2016年   107篇
  2015年   151篇
  2014年   216篇
  2013年   319篇
  2012年   412篇
  2011年   450篇
  2010年   227篇
  2009年   238篇
  2008年   389篇
  2007年   387篇
  2006年   411篇
  2005年   392篇
  2004年   364篇
  2003年   333篇
  2002年   339篇
  2001年   189篇
  2000年   180篇
  1999年   138篇
  1998年   65篇
  1997年   42篇
  1996年   56篇
  1995年   45篇
  1994年   32篇
  1993年   33篇
  1992年   80篇
  1991年   78篇
  1990年   50篇
  1989年   63篇
  1988年   49篇
  1987年   55篇
  1986年   42篇
  1985年   36篇
  1984年   34篇
  1983年   21篇
  1981年   19篇
  1980年   20篇
  1979年   28篇
  1978年   15篇
  1976年   13篇
  1975年   20篇
  1974年   16篇
  1973年   16篇
  1972年   14篇
排序方式: 共有7106条查询结果,搜索用时 15 毫秒
21.
We present a review of the relationship between Human Papillomavirus (HPV), Precancer and Epidermoid Cancer of the uterine cervix, Co-factors that contribute in cervical carcinogenesis and the mechanism through which Papillomaviruses transform normal cells into neoplastic cells by inducing an overproduction of the encoded proteins. We also offer final remarks and conclusions on this pathology that increases its incidence every year.  相似文献   
22.
AIMS: The aims of this observational study were to identify the special needs of children with Type 1 diabetes in schools from the parents' point of view and the difficulties experienced with full integration, and to define a series of interventions which may improve the situation. METHODS: Parents of children aged 3-18 years with Type 1 diabetes were eligible. Those who agreed to participate completed a self-reporting questionnaire which determined the effects of the disease on children, parents and school personnel, and addressed aspects including children's integration, glycaemic control, insulin administration, meals, sports, trips and attitudes of teachers and school colleagues to their disease. RESULTS: A total of 499 questionnaires were completed and validated. Median age of children was 11.5 years (95% CI 7.8-15.2). Only 34% of parents believed that teachers could recognize the symptoms of a mild hypoglycaemic episode. Seventeen per cent of parents experienced problems at their schools when they informed staff about their children's disease, 5% were finally not accepted and 8% were forced to change school. In some cases, they had to modify glucose monitoring (9%) and treatment administration (16%) because of a lack of cooperation from the school. CONCLUSIONS: Training sessions on Type 1 diabetes, an increase in the number of nurses, better availability of resources from diabetic associations to schools and improved communication between school personnel and parents were identified as key factors that may improve the full integration of the diabetic child in this setting.  相似文献   
23.
This document shows the results obtained from a study on the concentration of toxic heavy metals in the internal tissue and exoskeleton of sea urchins, collected from their natural habitat. The levels of lead and cadmium were measured by Graphite Furnace Atomic Absorption Spectrometry. The mean concentrations of lead and cadmium in the internal tissue were 304.04 and 260.54 μg/kg respectively, whereas in the shell they were 185.02 and 142.48 μg/kg. We also performed a statistical analysis of the differences in the distribution of metals between their exoskeleton and their internal content, a correlation study of the metal content in internal tissue and shell and sampling areas, and a correlation study between the metal content and sample size. Since the sea urchin Diadema antillarum presents a wide range of variation in metal content, this study suggests that this species is an excellent bioindicator of heavy metal contamination. © 2009 Wiley Periodicals, Inc. Environ Toxicol, 2010.  相似文献   
24.
A total of 594 flat colorectal polyps, removed at endoscopy, were histologically classified into non-neoplastic (n=49) and neoplastic (n=545) polyps. Non-neoplastic polyps were subdivided into metaplastic (n=45) and hyperplastic (n=4), whereas neoplastic polyps were subdivided into adenomas (n=481), intramucosal carcinomas (n=28) and invasive adenocarcinomas (n=36). Several adenoma phenotypes were discerned: tubular (n=375), serrated (n=59), villous (n=39), mixed (n=7) and fenestrated (n=1). Intramucosal carcinomas were subdivided into tubular (n=26) and serrated (n=2), and invasive adenocarcinomas into tubular (n=32), serrated (n=3) and fenestrated (n=1). The microscopic characteristics of each histologic phenotype described in this communication are defined and illustrated.  相似文献   
25.
Objective To elucidate the role of the L-arginine: nitric oxide pathway in pregnancy and pre-eclampsia.
Participants Pregnant women (nulliparous, age < 25 years). Normotensive pregnancy (   n = 22  ) was defined when blood pressure remained at levels of < 120/80 mmHg and there was no proteinuria. Women with pre-eclampsia (   n = 22  ) had blood pressure measurements of > 140/90 mmHg and proteinuria of > 300 mg/l. Nonpregnant normotensive women (   n = 22  ) were studied as controls.
Study Design Blood samples were taken for measurements of ionised calcium, atrial natriuretic factor, cyclic guanosine 3'5'monophophate (GMP), arginine and asymmetric dimethylarginine. Urine samples were collected for determination of cyclic GMP excretion. Cyclic GMP concentrations were also determined in 12 women with severe pre-eclampsia before and after treatment with hydralazine.
Results L-arginine, asymmetric dimethylarginine and atrial natriuretic factor were not different in any group. Cyclic GMP concentrations in plasma [0.94 (SD 0.23) nM] as well as in urine [50.1 (SD15.7)μM] were increased significantly (   P < 0.05  ) in normal pregnancy compared to nonpregnant controls [plasma mean 0.46 (SD 0.12) nM and urine mean 18.4 (SD 10.3) μM], but not in the pre-eclampsia group [plasma mean 0.48 (SD 0.10) nM and urine mean 24.1 (SD 14.5) μM]. Concentrations of cyclic GMP in plasma and urine increased significantly (   P < 0.05  ) in women treated with hydralazine.
Conclusions The differences in cyclic GMP concentrations may reflect differences in nitric oxide production. Hydralazine increases cyclic GMP concentrations in severely pre-eclamptic women. This action could explain the antihypertensive effect of hydralazine.  相似文献   
26.
The presence of a resident T lymphocyte population in the meninges of normal SJL/J mice has been detected by the use of the T cell-specific mitogen concanavalin A. Optimal conditions for [3H]thymidine incorporation were studied. An antigen-specific meningeal T cell proliferative response in SJL/J mice, primed by intracerebral inoculation of Theiler's murine encephalomyelitis virus, was also detected. This response indicated that leptomeningeal mononuclear cell infiltrations are involved in the immune response that triggers the demyelinating disease.  相似文献   
27.
28.
Matrix Metalloproteinases in Breast Cancer   总被引:1,自引:0,他引:1  
Abstract: Matrix metalloproteinases (MMPs) represent a class of enzymes able to degrade numerous extracellular matrix macromolecules facilitating tumor invasion and metastasis. The principal MMPs involved in breast pathology are analyzed with their various roles and functions: gelatinases A and B, stromelysin-3, collagenase-3, and MT-MMP1 (membrane type MMP). In vivo and in vitro studies clearly demonstrate an important cooperation between tumor and stromal cells for the expression of these MMPs in breast carcinomas. The large expression of MMPs plead in favor of a major role of these enzymes in breast carcinoma progression and their detection may be used in some cases as a prognostic indicator. Studies now are in progress, directed toward the modulation of these MMPs and their inhibitors with new therapeutic agents to block tumoral invasion and metastasis due to these enzymes.?  相似文献   
29.
Musculo-fibrous anomaly in Barrett's mucosa with dysplasia   总被引:1,自引:0,他引:1  
We investigated the histological alterations occurring in the muscularis mucosae, the lamina propria mucosae, and the submucosa in areas adjacent to invasive adenocarcinoma in 32 resected esophagi with Barrett's mucosa. In 26 of the 32 specimens, we observed a thickening of the muscularis mucosae, with overgrowth of the muscle fibers into the lamina propria mucosae. In other areas, collagen-rich fibrotic tissue replaced the muscularis mucosae, the lamina propria mucosae, and even the submucosa. In 31 of the 32 specimens, we noted cystic dilatations of the esophageal glands. Normal esophageal glands and cystically dilated glands with dysplastic lining were often surrounded, compressed, and deformed by the fibrotic tissue. The compression of the glandular outlets by the collagen-rich tissue or by proliferating dysplastic cells appeared to be the two main factors in the histogenesis of these cysts. This may result in difficulty in differentiating, in biopsy specimens, between normal and dysplastic esophageal glands "trapped" in the collagen-rich fibrotic tissue and true invasive adenocarcinoma in the Barrett's mucosa.  相似文献   
30.
The effect of acute and chronic stress on the colonic mucosa of the rat was investigated at various time intervals, ranging from one day to eight weeks. The amount of DNA synthesized by the mucosa was used as a marker of time-related events. A total of 75 Sprague-Dawley rats were investigated. Acute stress was considered for rats briefly plunged (psychic stimulus) or swimming for two hours (physical stimulus). Chronic stress was determined when rats were briefly plunged or swam for two hours for periods ranging from one to eight weeks. "Sham-transported" rats were used as controls. DNA in the descending colon decreased significantly in rats swimming for two weeks, but increased (even for plunged rats) at four and eight weeks. In the ascending colon, a substantial increase in DNA content was found in rats plunged or swimming for eight weeks. The descending colon appears to be quantitatively more affected by various stressors than the ascending colon. It is apparent that, in control rats, the mucosa of the descending colon differs from the ascending colon. Fluctuations in the colonic DNA synthesis throughout the experiment suggest that this phenomenon may be connected to compensatory mechanisms toward cell adaptation to stress conditions. The model may prove of value in studies of the therapeutic abrogation of the fluctuations of the DNA replication of the colonic mucosa during the acute and chronic phases of a given stress.  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