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   1024813篇
  免费   77444篇
  国内免费   2779篇
耳鼻咽喉   13228篇
儿科学   35331篇
妇产科学   29099篇
基础医学   148467篇
口腔科学   28282篇
临床医学   92902篇
内科学   199308篇
皮肤病学   23402篇
神经病学   81285篇
特种医学   39265篇
外国民族医学   305篇
外科学   153637篇
综合类   24453篇
一般理论   399篇
预防医学   79669篇
眼科学   23809篇
药学   73858篇
  4篇
中国医学   2151篇
肿瘤学   56182篇
  2018年   11299篇
  2017年   8758篇
  2016年   9970篇
  2015年   11256篇
  2014年   15348篇
  2013年   23115篇
  2012年   30788篇
  2011年   32696篇
  2010年   19555篇
  2009年   18352篇
  2008年   30418篇
  2007年   32007篇
  2006年   32414篇
  2005年   31028篇
  2004年   30326篇
  2003年   29017篇
  2002年   27902篇
  2001年   47808篇
  2000年   48839篇
  1999年   40953篇
  1998年   11447篇
  1997年   10310篇
  1996年   10345篇
  1995年   9954篇
  1994年   9259篇
  1993年   8637篇
  1992年   32662篇
  1991年   31861篇
  1990年   31363篇
  1989年   30211篇
  1988年   27470篇
  1987年   27585篇
  1986年   25697篇
  1985年   24842篇
  1984年   18567篇
  1983年   15670篇
  1982年   9391篇
  1981年   8461篇
  1979年   16987篇
  1978年   12293篇
  1977年   10386篇
  1976年   9811篇
  1975年   10232篇
  1974年   12388篇
  1973年   11909篇
  1972年   10935篇
  1971年   10159篇
  1970年   9404篇
  1969年   8755篇
  1968年   8121篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Noninvasive localized proton magnetic resonance spectroscopy (MRS) was used for differential diagnosis of a focal brain lesion in a 2.5-year-old girl. The clinical signs were a mild head tilt and neck pain. Magnetic resonance imaging (MRI) revealed a lesion in the right hemisphere of the cerebellum, but its nature remained obscure. In this lesion quantitative determinations of cerebral metabolites by fully relaxed, short-echo-time proton MRS revealed markedly lowered N-acetylaspartate (NAA) and pronounced elevations of choline-containing compounds (Cho) and myo-inositol (Ins), whereas metabolite concentrations in cortical gray matter and white matter were within normal ranges. The metabolite pattern of the lesion indicated loss of vital neuroaxonal tissue (low NAA) and enhanced glial proliferation (high Cho and Ins), which, together with the MRI morphology, suggested a brain tumor. The diagnosis was established by neurosurgical exploration and total extirpation of the tumor. Histology confirmed an astrocytoma (WHO II). After 2 weeks' recovery the child was discharged with no neurological signs.  相似文献   
92.
The role of caffeine or coffee in causing or promoting the incidence of serious disease is equivocal. Two design factors may account for the discrepancies in reported findings on the effects of coffee drinking: (a) imprecision of measurement and (b) confounding variables. A study of 2,714 white U.S. adults disclosed that, of 32 risk factors analyzed by linear and logistic regression, only sex and cigarette smoking were found to be important potential confounders of caffeine and coffee intake. Partial R2 values of the other 30 risk factors were relatively small and were inconsistent for each sex. It is unlikely that any of these factors could explain any of the reported associations between caffeine or coffee consumption and certain diseases. However, certain weak associations with caffeine or coffee intake should be included in the study design when they are known to be risk factors of a disease under investigation. These factors for men are dietary fat intake, vitamin C intake, and body mass index; and for women are vitamin use, alcohol intake, stress, and perceived health status.  相似文献   
93.
The commodity model of social support and features of Nondirective Support may clarify varied results of support interventions for smoking cessation. A commodity model views social support as attractive in and of itself and as an alternative to high-risk choices such as smoking. If such support is easily accessible, a would-be quitter is less likely to choose to smoke. Consistent with the commodity model, social support interventions tend to be effective as long as support remains available, but they lose their effects when support is terminated. From a second approach, Nondirective Support entails accepting recipients' goals, cooperating without taking control, and validating recipients' feelings. In contrast, Directive Support entails taking control and telling recipients what to do and feel. Review of support interventions indicates the value of the continued availability of support suggested by the commodity model and of Nondirective Support's flexibility and responsiveness to the person.  相似文献   
94.
Background: The study reviews the anticancer properties of naturalisoflavones which occur in especially high concentration in soybeans. Itconsiders the suitability of soybean products for clinical trials aiming toreduce the progression of breast cancer.Methods: Evidence is reviewed that plant isoflavones such asgenistein show cytostatic activity against human mammary cancer cell linesin vitro and can also suppress carcinogen-induced mammary cancer inyoung and mature rats.Results: Plant isoflavones are converted in the bowel to compoundswith potential antioestrogenic and antioxidative properties. These compoundsshow cytostatic activity for both oestrogen receptor-positive and negativehuman mammary cancer cell lines, and also inhibit growth and progress of therat mammary cancer model. The high content of soybean products in the diet ofAsian women has been postulated as one reason for their relatively low breastcancer incidence.Conclusion: Preclinical studies suggest that soybean products begiven priority for clinical trials in breast cancer protection. A pilot studycould test soy protein supplements as long-term adjuvant dietary treatmentafter primary surgery for early breast cancer, looking for a decrease in therisk of recurrence or of second primary tumours.  相似文献   
95.
96.
The objectives of this study were to investigate (1) changes in consumption of alcohol among pregnant women over a period of 5 years (1984/85–1990), (2) changes of attitudes towards drinking during pregnancy in the general population over the same period of time, and (3) possible connections between (1) and (2). The investigation was designed as a cross-sectional study. Our subjects were two representative samples of pregnant women in Oslo, n = 577 and 425, and two representative samples of the Norwegian population, n = 1004 and 1204. The main outcome measures were a self-completed questionnaire for the pregnant women and a personal interview for the general population sample. There was a significant reduction (50% decrease) in alcohol consumption among the second cohort of pregnant women compared with the first. Furthermore, we found an increase during the 5-year period in the number of persons with a restrictive attitude towards alcohol use during pregnancy. There seems to be a connection between these two phenomena, but with our present state of knowledge it is hard to say anything about the causal relationship between them.  相似文献   
97.
Corpus cavernosography in a patient with erectile dysfunction revealed absence of communication between the 2 cavernous bodies. No similar case was found in a review of 100 consecutive cavernosograms or in the literature. The abnormality may be a source of error in pressure recordings or in intravenous injection of pharmaceutical agents.  相似文献   
98.
99.
100.
The urological complications of 320 consecutive renal transplants performed at our institution between October 17, 1985 and November 10, 1989 are reviewed. The Leadbetter-Politano technique of ureteroneocystostomy was used in the first 160 patients (group 1) and an anterior extravesical technique modified from the methods of Witzel, Sampson and Lich was performed in the second 160 patients (group 2). Urological complications occurred in 15 patients (9.4%) in group 1 and 6 (3.7%) in group 2 (p = 0.04). Ureterovesical junction obstruction occurred in 6 patients (3.7%) in group 1 and 1 (0.6%) in group 2 (p = 0.05). Complications of leakage, ureteral necrosis and ureteral stricture were comparable in the 2 groups. Therefore, we advocate the use of the anterior extravesical technique over Leadbetter-Politano ureteral reimplantation based on the lower incidence of urological complications and various technical advantages, including less operative time, avoidance of a separate cystotomy, less hematuria and ability to use short donor ureters.  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