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   6441篇
  免费   600篇
  国内免费   14篇
耳鼻咽喉   53篇
儿科学   280篇
妇产科学   201篇
基础医学   909篇
口腔科学   152篇
临床医学   663篇
内科学   1417篇
皮肤病学   124篇
神经病学   660篇
特种医学   176篇
外国民族医学   1篇
外科学   1097篇
综合类   36篇
一般理论   4篇
预防医学   401篇
眼科学   140篇
药学   294篇
  1篇
中国医学   6篇
肿瘤学   440篇
  2022年   49篇
  2021年   85篇
  2020年   68篇
  2019年   85篇
  2018年   106篇
  2017年   79篇
  2016年   123篇
  2015年   96篇
  2014年   150篇
  2013年   176篇
  2012年   294篇
  2011年   307篇
  2010年   176篇
  2009年   176篇
  2008年   285篇
  2007年   310篇
  2006年   292篇
  2005年   326篇
  2004年   313篇
  2003年   317篇
  2002年   294篇
  2001年   249篇
  2000年   261篇
  1999年   219篇
  1998年   91篇
  1997年   89篇
  1996年   75篇
  1995年   91篇
  1994年   60篇
  1993年   49篇
  1992年   121篇
  1991年   120篇
  1990年   109篇
  1989年   123篇
  1988年   86篇
  1987年   86篇
  1986年   97篇
  1985年   74篇
  1984年   83篇
  1983年   60篇
  1982年   39篇
  1981年   31篇
  1980年   31篇
  1979年   66篇
  1978年   49篇
  1977年   32篇
  1976年   36篇
  1975年   37篇
  1974年   42篇
  1972年   40篇
排序方式: 共有7055条查询结果,搜索用时 15 毫秒
41.
OBJECTIVES: This study developed a new acquired immunodeficiency syndrome (AIDS) severity system by including diagnostic, physiological, functional, and sociodemographic factors predictive of survival. METHODS: Three-hundred five persons with AIDS in Boston were interviewed; their medical records were reviewed and vital status ascertained. RESULTS: Overall median (+/- SD) survival for the cohort from the first interview until death was 560 +/- 14.4 days. The best model for predicting survival, the Boston AIDS Survival Score, included the Justice score (stage 2 relative hazard [RH] = 1.25, 95% confidence interval [CI] = 0.80, 1.96; stage 3 RH = 1.76, 95% CI = 1.15, 2.70), a newly developed opportunistic disease score (Boston Opportunistic Disease Survival Score; stage 2 RH = 1.35, 95% CI = 0.90, 2.02; stage 3 RH = 2.10, 95% CI = 1.38, 3.18), and measures of activities of daily living (any intermediate limitations, RH = 1.84, 95% CI = 1.05, 3.21; any basic limitations, RH = 2.60, 95% CI = 1.44, 4.69). This model had substantially greater predictive power (R2 = .17, C statistic = .68) than the Justice score alone (R2 = .09, C statistic = .61). CONCLUSIONS: Incorporating data on clinically important events and functional status into a physiologically based system can improve the prediction of survival with AIDS.  相似文献   
42.
43.
Numerous studies have shown evidence of cerebral ventricular enlargement in schizophrenia and its relationship to severity of clinical symptoms and psychosocial dysfunction. In this large prospective study, 88 noninstitutionalized DSM-III-R schizophrenic patients were administered a CT scan and rated for positive and negative symptomatology and premorbid adjustment. The CT scans from 14 healthy controls were used for comparison of cerebral ventricular measures. Patients had an enlarged ventricle to brain ratio of the anterior portion of the lateral ventricles, the frontal horns, compared with controls. Patients with larger frontal horns had more severe negative symptoms and poorer premorbid childhood adjustment. The area of the main body of the cerebral lateral ventricles, though not elevated in patients, was correlated with the total number of prior hospitalizations. These results support the hypothesis of a structural and functional "frontal" deficit in schizophrenia.  相似文献   
44.
The fresh brain weights of 79 infants with sudden infant death syndrome (SIDS) were tabulated and compared with expected "normal" brain weights. The series included 47 males and 32 females. Their ages ranged from 8 days to 16 months with a median of 2.5 months. The weights of all these brains were above the 50th percentile for age, and 64 of 79 brains (81%) were above the 95th percentile, including 15 (19%) at or above the 99.9th percentile. The ratio of the brain stem plus cerebellum weight to the whole brain weight of 93 formalin-fixed brains from victims of SIDS showed that the cerebrum was disproportionately heavier in most cases. No gross or microscopic evidence of cerebral edema was noted to account for the heavier weight. The significance of these findings is debatable. The increase in brain weight was less obvious in infants younger than 1 month of age but accelerated after that age. The brain weights of infants with SIDS may represent the really "normal" weights, since these patients were not known to be ill prior to death. If the brain weights of SIDS infants are really heavier than "normal," the possibility must be considered that disproportionately rapid growth of the brain during early infancy may be detrimental to the neural control of the cardiorespiratory system.  相似文献   
45.
In an ongoing multicenter clinical trial, "Treatment Strategies in Schizophrenia," the five participating sites have the capacity to perform a variety of tasks or study functions independently. These tasks include (a) verification of diagnostic eligibility through the use of computerized decision algorithms; (b) assignment of patients to treatment based on prognostic indicators using a computerized randomization algorithm; (c) entry of data into a microcomputer using a clinical trial data management system that performs simple range and missing data item checks; and (d) regular transfer of all data to the central coordinating team. The clinical trial data management system employed allows for both independent site functioning and assurance of consistency across sites. The integration of a variety of software outside the main data management system provides the central coordinators with the tools to monitor critical data as it is collected, as well as the capacity to assess the flow, quality, and uniformity of the ongoing trial.  相似文献   
46.
47.
We describe a 12-year-old boy with Wiskott-Aldrich syndrome who developed a pulmonary vasculitis associated with lymphoreticular proliferation, consistent with the histological and clinical diagnosis of lymphomatoid granulomatosis. The lesions were responsive to cyclophosphamide and steroids. The patient has had severely depressed immune function and was shown to have abnormal Epstein-Barr virus (EBV)-specific cellular and humoral immune responses. Lymph nodes obtained at autopsy were positive for EBV genome. In this patient, reactivated EBV infection resulting from impaired immune surveillance of the virus may have been responsible for the development of this paraneoplastic disorder.  相似文献   
48.
The infective third-stage larvae of the hookworms Necator americanus and Ancylostoma duodenale infect their human hosts by active skin invasion, but A. duodenale is in addition capable of oral infection. The behaviour of the larvae when crawling on surfaces has already been described. Here we analyse in various in vitro systems the other behavioural invasion phases: activation, penetration, and orientation within the host. The larvae normally remained in a motionless, energy-saving, resting posture. An activation to sinusoidal locomotion was stimulated in both species by similar cues such as touch, vibration, water currents, heat, light, and chemicals. Human breath in addition stimulated searching and waving (nictating) behaviour, which facilitates a change-over to the host. Activating cues in air streams were warmth and moisture; CO2 activated only in combination with warmth and/or moisture. Penetration behaviour in both species was stimulated by warmth and skin extracts. The stimulating components of skin extracts were fatty acids, but their stimulating characteristics differed from those inducing schistosome cercarial skin penetration. After penetration into agar substrates, both species showed thermo-orientation, but only A. duodenale followed gradients of serum. The directing serum cues were not amino acids and glucose (the supposed cues for schistosome blood vessel localization), but Ringers solution attracted the larvae. The host-finding and host-invasion behaviour of both hookworm species is well adapted to the invasion of the human skin, and there seems to be no particular adaptation of A. duodenale behaviour to the oral infection mode. Hookworm host-finding behaviour is not as complex as that of schistosome cercariae but seems well adapted to the ecological conditions in the transmission sites.  相似文献   
49.
Summary A study of the distribution of polioviruses in Surinam was undertaken by a regular virological examination of stool specimens from children of the 1–5 year age group for a period ranging from the beginning of 1964 to the middle of 1969. All three types of poliovirus were found to circulate continuously in the child population. A correlation was found between an increased level of poliovirus circulation and the appearance of clinical poliomyelitis. The application of trivalent oral vaccine at times that a clear increase of the level of poliovirus circulation was observed, had only a partial effect on this level since the acceptance rate for the vaccine was too low.Conducted with the support of the Surinam Government and the Netherlands Foundation for the Advancement of Tropical Research (WOTRO), and with technical assistance of Miss L. Kletter and Mrs. A. Arron.on temporary detachment at the Central Public Health Laboratory, Paramaribo, Surinam.  相似文献   
50.
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