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   1307901篇
  免费   99600篇
  国内免费   2092篇
耳鼻咽喉   18745篇
儿科学   46026篇
妇产科学   35654篇
基础医学   185827篇
口腔科学   34300篇
临床医学   113431篇
内科学   264211篇
皮肤病学   28693篇
神经病学   101944篇
特种医学   51841篇
外国民族医学   660篇
外科学   200500篇
综合类   28088篇
现状与发展   2篇
一般理论   392篇
预防医学   97406篇
眼科学   29259篇
药学   97583篇
  2篇
中国医学   2636篇
肿瘤学   72393篇
  2019年   9856篇
  2018年   14069篇
  2017年   10608篇
  2016年   11751篇
  2015年   13229篇
  2014年   18334篇
  2013年   27746篇
  2012年   38102篇
  2011年   40205篇
  2010年   24005篇
  2009年   22898篇
  2008年   38133篇
  2007年   40707篇
  2006年   40988篇
  2005年   39577篇
  2004年   38696篇
  2003年   37409篇
  2002年   36627篇
  2001年   64583篇
  2000年   67091篇
  1999年   56906篇
  1998年   15359篇
  1997年   13912篇
  1996年   14360篇
  1995年   13610篇
  1994年   12884篇
  1993年   11898篇
  1992年   44882篇
  1991年   43723篇
  1990年   42510篇
  1989年   40361篇
  1988年   37123篇
  1987年   36458篇
  1986年   33854篇
  1985年   32490篇
  1984年   24312篇
  1983年   20440篇
  1982年   11830篇
  1981年   10767篇
  1979年   21489篇
  1978年   14921篇
  1977年   12646篇
  1976年   11776篇
  1975年   12741篇
  1974年   14782篇
  1973年   14246篇
  1972年   13069篇
  1971年   11845篇
  1970年   11129篇
  1969年   10111篇
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
91.
The Authors examine the correlation between hypertensive disorders of pregnancy and fetal growth. The results of a study of 342 pregnancies, confirm a significant correlation between hypertension and fetal growth retardation. These findings, so evident in moderate and severe hypertension, have also been confirmed in cases of mild hypertension. The medical treatment also in the pregnancies with mild hypertension, and a larger utilisation of operative deliveries, determined a decrease in perinatal mortality and morbidity.  相似文献   
92.
Background The appearance of eosinophils is a hallmark sign of the allergic late-phase response (LPR). Eosinophil cationic protein (ECP), a readily measurable product released from activated eosinophils, has so far not been evaluated in the ocular LPR. Objective Two sets of trials were performed in order to investigate changes of local and systemic eosinophil activity and their possible link with symptoms and hyper-reactivity in the allergic LPR in the eye. Methods In the first experiment, ECP was analysed in tears and serum and the clinical reaction was evaluated during a 72-h time–course after a single, high-dose allergen challenge out of season in one eye of 15 pollen-sensitized volunteers. In a second experiment, the hypothesis of an increased clinical response to an allergen challenge in an eye that had been provoked with allergen 48h previously was tested in nine sensitized individuals. Results In the first experiment, symptoms at 10 min and 2, 4, 6, 8 and 24 h significantly exceeded base line scores of the challenged eyes. Tear ECP was significantly elevated in challenged eyes compared to contralateral eyes at 6, 8 and 24 h. In addition, symptoms and ECP release correlated significantly at the 24-h evaluation. Serum ECP remained unchanged throughout the study period. In the second experiment, conjunctival hyperreactivity 48h after an allergen challenge was not confirmed. Conclusion ECP secretion occurs in the experimental ocular LPR and is in part associated with the magnitude of the clinical reaction, which suggests a truly pathogenic role of the activated eosinophil in pollen-induced allergic conjunctivitis.  相似文献   
93.
94.
95.
96.
97.
Birth weight on 12,644 singleton infants from 6,196 sibships born in Maryland between 1980 and 1984 were used to estimate the effects of nine maternal and infant covariates on the sibship correlation in birth weight. Assuming a homogeneous correlation across all families, the estimated intraclass correlation was 0.4664 (+/- 0.0099). This high sibship correlation makes it possible to predict, with reasonable accuracy, the birth weight of a child given information on previous sibs, as well as covariates on the mother and/or infant pertinent to a given pregnancy. The reduction in variance associated with incorporating information on the nine covariates used here was approximately equal to that obtained by conditioning on a single previous sib. Testing for heterogeneity in correlation among different groups of families showed that a crude measure of parity (first live birth vs. other), time between births, mother's marital status, and maternal age at the birth of the last child significantly influenced the sibship correlation in birth weight.  相似文献   
98.
This study was conducted to follow up healthy subjects from a previous study (Warwick & Williams, 1987) in which favourable dietary changes were achieved during 1 week immediately after dietary advice but were accompanied by reduced energy intakes and weight loss. Twenty-one subjects (8m, 13f; 57 per cent of the original group) participated in the follow-up study. Dietary intakes were measured using 7-d weighed records on three occasions: before, immediately after and 1 year after receiving dietary advice. Intakes 1 year after dietary advice continued to show some of the favourable changes observed immediately after the advice but were not accompanied by reduced energy intakes and weight loss. Intakes before, immediately after, and 1 year after dietary advice respectively were: energy, 9.0, 7.8 and 8.9 MJ/d (2150, 1860 and 2120 kcal/d); fat, 36.9, 32.9 and 31.5 per cent of total energy; carbohydrate, 44.2, 47.9 and 49.6 per cent of total energy; dietary fibre, 32, 36 and 36 g/d; sodium, 116, 97 and 110 mmol/d; and Na:K ratio, 1.4, 1.2 and 1.2 mmol. Nutrient densities for fibre and most micronutrients tended to be higher 1 year after dietary advice than before, but were highest immediately after the advice. Nutrient densities for sodium and total sugars did not vary between the 3 study weeks. It was concluded that our healthy subjects adapted their intakes to maintain energy balance while retaining favourable dietary changes for at least 1 year after dietary advice.  相似文献   
99.
Eledoisin has been tried as a possible treatment for dry eye based on the hypothesis that it pharmacologically stimulates tear secretion when topically applied to the eye. To determine if topically applied eledoisin pharmacologically stimulates orbital lacrimal secretion, the orbital lacrimal gland excretory duct of normal rabbits was cannulated, and eledoisin was applied topically with and without prior administration of proparacaine. To determine if topically applied eledoisin stimulated accessory lacrimal gland secretion, isotonic buffer with and without eledoisin was tested in a rabbit model with only accessory lacrimal tissue remaining after the administration of proparacaine. Topically applied eledoisin did not pharmacologically stimulate lacrimal secretion but rather increased lacrimal gland secretion only in non-anesthetized eyes through a sensory reflex mechanism that is blocked by proparacaine.  相似文献   
100.
Transcranial magnetic stimulation (TMS) and transcranial electrical stimulation (TES) of the human motor cortex produce a silent period (SP) following motor evoked potentials (MEPs). The early part of the SP can be explained by decreased alpha motor neuron excitability, whereas the late part is presumably due to suprasegmental mechanisms. In order to determine the level of the suprasegmental contribution to the generation of SPs, we recorded excitatory and inhibitory responses to TMS, TES, and percutaneous electrical brainstem stimulation (PBS) in the voluntarily activated first dorsal interosseous muscle of the hand. Stimulus intensities were set so that PBS and TES induced MEPs with areas equal to or larger than those of MEPs obtained with TMS. This procedure revealed that SPs were 49% and 83% shorter with TES and PBS, respectively, than with TMS. As TMS is more effective than TES or PBS in activating cortical interneurons, these findings support the idea that a significant component of the SP arises from intracortical mechanisms.  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