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   1109341篇
  免费   80799篇
  国内免费   2714篇
耳鼻咽喉   14871篇
儿科学   38302篇
妇产科学   31130篇
基础医学   162055篇
口腔科学   31532篇
临床医学   99723篇
内科学   213526篇
皮肤病学   26153篇
神经病学   90589篇
特种医学   43261篇
外国民族医学   305篇
外科学   166014篇
综合类   24222篇
一般理论   418篇
预防医学   84135篇
眼科学   25067篇
药学   79624篇
  3篇
中国医学   2206篇
肿瘤学   59718篇
  2019年   8470篇
  2018年   13022篇
  2017年   10317篇
  2016年   12080篇
  2015年   12889篇
  2014年   16973篇
  2013年   26632篇
  2012年   34862篇
  2011年   37531篇
  2010年   22227篇
  2009年   19900篇
  2008年   35522篇
  2007年   37583篇
  2006年   37783篇
  2005年   36339篇
  2004年   35256篇
  2003年   34151篇
  2002年   33055篇
  2001年   50620篇
  2000年   52753篇
  1999年   42881篇
  1998年   12307篇
  1997年   11020篇
  1996年   10904篇
  1995年   10374篇
  1994年   9680篇
  1993年   9027篇
  1992年   32766篇
  1991年   31920篇
  1990年   31449篇
  1989年   30344篇
  1988年   27561篇
  1987年   27771篇
  1986年   25793篇
  1985年   25138篇
  1984年   18912篇
  1983年   15960篇
  1982年   9775篇
  1981年   8843篇
  1979年   17235篇
  1978年   12570篇
  1977年   10724篇
  1976年   10103篇
  1975年   10521篇
  1974年   12638篇
  1973年   12120篇
  1972年   11101篇
  1971年   10358篇
  1970年   9595篇
  1969年   8916篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
The anticarcinogenic action of the garlic constituent diallyl sulfide (DAS), was examined in the hamster buccal pouch and forestomach. Groups of hamsters were topically treated, for up to 14 weeks, with a 0.5% solution of the buccal pouch and forestomach carcinogen 7,12-dimethylbenz[a]anthracene (DMBA). Prior to, during and after DMBA treatment, groups of hamsters were also treated, on alternate days, with a 1% solution of DAS. In addition to tumor formation, the induction of gamma-glutamyl transpeptidase (gamma GT) buccal pouch epithelial lesions served as an additional presumptive index of in vivo carcinogenesis/anticarcinogenesis. DAS resulted in a significant reduction in buccal pouch tumor frequency, buccal pouch tumor burden, buccal pouch gamma GT lesion frequency and forestomach tumor frequency. In a separate experiment, DAS also reduced the level of autoradiographically quantified unscheduled DNA repair synthesis (UDS) in pieces of hamster buccal pouch concurrently exposed in vitro to the potent buccal pouch carcinogen N-methyl-N-benzylnitrosamine (MBN). This study demonstrates that DAS is an effective anticarcinogenic agent in squamous mucosa of the hamster and suggests novel cost-effective strategies for the rapid identification of tissue-specific anticarcinogens and a quantitative assessment of their efficacy.  相似文献   
92.
Exposure to cadmium via the diet is known to depend to a large extent on the intake of cereal grains, particularly the high-fibre fractions of wheat. Subjects with low iron status absorb more cadmium than those with better iron status. The purpose of the present study was to determine to what extent cadmium accumulation in human placenta is affected by the intake of grain fibre and maternal iron status during pregnancy. Thirty-nine pregnant women participated in the study. In each trimester the women were requested to complete a dietary history and to allow blood samples to be taken for haemoglobin, serum ferritin and serum thiocyanate determinations, the latter as a marker for smoking. At delivery the whole placenta was taken for the determination of the cadmium concentration. The 32 women who had serum thiocyanate levels less than 70 mumol/l, who had completed at least one dietary history and from whom a blood sample was obtained in the third trimester, were included in the final statistical analyses. In the group of women who consumed less than the median intake of grain fibre and had more than 15 micrograms ferritin/l serum in the third trimester, the placenta cadmium concentration was nearly half that in the placentae of women who had consumed more grain fibre or had lower iron status in late pregnancy.  相似文献   
93.
94.
95.
96.
PATIENTS AND METHOD: The aim of the present study was to contribute to a more accurate indication and better integration of developing third molar transplantation into orthodontic space management, using the results gleaned from the authors' own pool of patients. For this purpose, a clinical and radiographic examination of 61 transplanted developing molars in 57 patients was carried out after an average of 3.3 years. RESULTS: The overall success rate was 85%. Failure was due in 10% of cases to impaired periodontal healing (inflammatory root resorption, ankylosis, or increased pocket probing depths) and in 5% of cases to insufficient or arrested postoperative root development accompanied by increased transplant mobility. The incidence of postoperative cessation of further root development was significantly higher (p = 0.011) in transplants at early developmental stages, which also had a negative impact on the final root length, the crown-root ratio and the mobility values of these transplants. CONCLUSIONS: The transplantation of developing third molars should be given stronger consideration in treatment plans for orthodontic space management although it represents a real alternative to orthodontic space closure only in exceptional cases. However, unlike implantological or prosthodontic treatment, it offers an opportunity to replace a missing or non-retainable tooth with a patient's own vital and fully functional tooth, provided the appropriate transplant is selected.  相似文献   
97.
98.
Three hundred and twenty samples of subgingival plaque were obtained from 80 caucasian girls, ranging from 10 to 13 years of age. The samples were analyzed to verify the influence of age upon colonization of the gingival sulcus by microorganisms potentially pathogenic to the periodontal tissues. The gingival and plaque status were evaluated through the gingival index (GI) and plaque index (PlI) and the microflora was assessed by the enzymatic method benzoyl-arginine-naphthylamide (BANA). The results of the BANA test were positive for 62.50% of the tested individuals and 40% of the examined sites. The influence of age was statistically significant on BANA reactivity, and the number of positive sites was greater at 11 (57.5%) than at 12 years (28.8%).  相似文献   
99.
Cerebral function in normoxia and its reactions to standard periods of hypoxia of increasing severity were studied in 30 newborn guinea pigs less than 3 days old. Intrauterine growth retardation was induced either by uterine artery ligation at midgestation or by feeding the female in late gestation with khat leaves, an amphetamine-like stimulant chewed by men and women in several countries in eastern Africa and Arabia. After spontaneous delivery, the neonates were anesthetized and ventilated. Cardiovascular, metabolic, and neurophysiologic (somatosensory evoked potentials) parameters were monitored. Under normoxia, the khat-exposed group showed prolonged latency of the primary response of the somatosensory evoked potentials and a reduced amount of secondary components. Under hypoxia, this group also has a greater reduction of amplitude of the somatosensory evoked potentials. It is concluded that khat exposure during fetal life has an impact on the cerebral function during the neonatal period (at least up to 3 days of age) which is not solely explained by the concomitantly produced growth retardation.  相似文献   
100.
Facial reanimation after acoustic neuroma excision is currently accomplished using a variety of surgical techniques. A multi-institutional survey of patient perceptions of facial reanimation success was accomplished by mailing a questionnaire to 809 randomly selected members of the Acoustic Neuroma Association. Four hundred sixty patients who underwent 296 reanimation procedures responded. Facial to hypoglossal nerve anastomosis, tarsorrhaphy, and upper eyelid implants were most frequently performed. The patient's estimations of initial deficit, spontaneous recovery, and overall satisfaction with the reanimation procedures are discussed.  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