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   1002590篇
  免费   75611篇
  国内免费   2631篇
耳鼻咽喉   13035篇
儿科学   35002篇
妇产科学   28551篇
基础医学   145945篇
口腔科学   27824篇
临床医学   90590篇
内科学   194623篇
皮肤病学   23127篇
神经病学   79381篇
特种医学   38544篇
外国民族医学   305篇
外科学   149985篇
综合类   23890篇
一般理论   388篇
预防医学   78122篇
眼科学   22801篇
药学   72317篇
  3篇
中国医学   2052篇
肿瘤学   54347篇
  2018年   10730篇
  2017年   8336篇
  2016年   9509篇
  2015年   10727篇
  2014年   14654篇
  2013年   22266篇
  2012年   29314篇
  2011年   31159篇
  2010年   18669篇
  2009年   17593篇
  2008年   29006篇
  2007年   30686篇
  2006年   31169篇
  2005年   29841篇
  2004年   29095篇
  2003年   27947篇
  2002年   26948篇
  2001年   47038篇
  2000年   48117篇
  1999年   40346篇
  1998年   11217篇
  1997年   10125篇
  1996年   10199篇
  1995年   9800篇
  1994年   9127篇
  1993年   8512篇
  1992年   32320篇
  1991年   31535篇
  1990年   31084篇
  1989年   29939篇
  1988年   27228篇
  1987年   27385篇
  1986年   25477篇
  1985年   24646篇
  1984年   18447篇
  1983年   15552篇
  1982年   9344篇
  1981年   8441篇
  1979年   16902篇
  1978年   12245篇
  1977年   10335篇
  1976年   9785篇
  1975年   10194篇
  1974年   12337篇
  1973年   11871篇
  1972年   10891篇
  1971年   10127篇
  1970年   9401篇
  1969年   8738篇
  1968年   8120篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
Isotretinoin (Accutane Capsules) is a synthetic vitamin A compound used for treatment of recalcitrant cystic acne. It has numerous ocular toxic side effects which include anterior segment inflammation, dry eye syndrome, contact lens intolerance, altered refraction, photosensitivity, and reduced night vision. Eye care practitioners should be aware of these potential side effects and be prepared to communicate with the prescribing physician if side effects present.  相似文献   
82.
Although extracellular matrix (ECM) glycoproteins play important roles in neural development, their levels are generally believed to decrease in the adult brain. Immunohistochemical analysis indicates that the anti-adhesive ECM glycoprotein SPARC/osteonectin, which contains a follistatin ‘module’, is expressed in the adult rabbit nervous system. In the cerebellum, SPARC is present in Bergmann glia, with a strong signal along their radial fibres. SPARC, while enriched in membrane fractions, is not a transmembrane protein. In the hippocampus, colocalization of SPARC is observed in cells which express the astrocytic marker GFAP. The expression of SPARC by a subset of astrocytes, particularly in synaptic enriched areas, suggests a continuing role for the ECM in the adult brain.  相似文献   
83.
84.
85.
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   
86.
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   
87.
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   
88.
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   
89.
90.
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   
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