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   2429354篇
  免费   175552篇
  国内免费   4740篇
耳鼻咽喉   33232篇
儿科学   77772篇
妇产科学   65483篇
基础医学   359847篇
口腔科学   66338篇
临床医学   217282篇
内科学   471099篇
皮肤病学   53329篇
神经病学   190635篇
特种医学   90767篇
外国民族医学   490篇
外科学   364728篇
综合类   51892篇
现状与发展   12篇
一般理论   881篇
预防医学   188609篇
眼科学   56349篇
药学   182131篇
  11篇
中国医学   5263篇
肿瘤学   133496篇
  2021年   19607篇
  2019年   20227篇
  2018年   28123篇
  2017年   21119篇
  2016年   23515篇
  2015年   26572篇
  2014年   37342篇
  2013年   55528篇
  2012年   76933篇
  2011年   81812篇
  2010年   48535篇
  2009年   45875篇
  2008年   76783篇
  2007年   81796篇
  2006年   82551篇
  2005年   79738篇
  2004年   76222篇
  2003年   73370篇
  2002年   70994篇
  2001年   112935篇
  2000年   115781篇
  1999年   97156篇
  1998年   28371篇
  1997年   24696篇
  1996年   24634篇
  1995年   23263篇
  1994年   21407篇
  1993年   20201篇
  1992年   74539篇
  1991年   72666篇
  1990年   70699篇
  1989年   68087篇
  1988年   62730篇
  1987年   61454篇
  1986年   57414篇
  1985年   55130篇
  1984年   40735篇
  1983年   34638篇
  1982年   20548篇
  1979年   37226篇
  1978年   26464篇
  1977年   21878篇
  1976年   20938篇
  1975年   22642篇
  1974年   27083篇
  1973年   25768篇
  1972年   24117篇
  1971年   22902篇
  1970年   21022篇
  1969年   20095篇
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
991.
992.
993.
Steady-state auditory evoked responses to frequency-modulated tones were obtained from normal children and two groups of children with developmental language disorders (developmental dysphasia). Children with predominantly expressive language impairment produced responses not different from normal children, while children with primary receptive language impairment produced responses that were markedly diminished, even absent. This occurred in recordings from either cerebral hemisphere and at mean frequency-modulation depths ranging from +/- 20 to +/- 100 Hz. Pathophysiology of auditory mechanisms concerned with frequency-modulation analysis are particularly associated with receptive developmental language impairment and may underlie associated difficulties in speech perception.  相似文献   
994.
In the present study, we examined the ultrastructure of striatal neurons containing neuropeptide Y (NPY) which were labeled by an immunohistochemical method using peroxidase-conjugated F(ab) fragments in the rat. Each of the 26 neurons identified had a deeply indented oval nucleus. The cytoplasm, which was mainly concentrated at the emergence of the dendrites, contained an abundant Golgi apparatus and a well-developed granular endoplasmic reticulum. Dendrites were poorly branched and rarely exhibited varicosities or dendritic spines. NPY-immunoreactive (Ir) axons were small in diameter and unmyelinated. These features corresponded to a subpopulation of striatal neurons classified as aspiny type IV in previous Golgi studies. Axon terminals forming symmetrical synapses were numerous on the NPY-Ir perikarya and proximal dendrites. On distal NPY-Ir dendrites, synaptic contacts were mainly of the asymmetrical type, suggesting that NPY neurons are contacted by at least 2 categories of afferent fibers. Several NPY-Ir axonal processes and boutons were found to form symmetrical synapses with dendrites, dendritic spines and perikarya belonging to spiny type neurons. These data were consistent with the view that NPY may act as a neurotransmitter of striatal interneurons. Moreover, the frequent observation of NPY axonal processes in the close vicinity of striatal vessels suggested that NPY might also play a role in the control of cerebral vasomotricity. Thirty hours after intranigral injection of 6-hydroxydopamine to induce a degeneration of nigrostriatal dopamine terminals, some characteristic degenerative boutons were observed in close apposition to NPY-Ir cell bodies, suggesting that NPY neurons are under a direct nigrostriatal dopaminergic influence.  相似文献   
995.
STUDY OBJECTIVE: The purpose of the study was to examine adult body height as an indicator of general health. DESIGN: The study was a survey of a randomly selected sample of the adult Swedish population obtained by the Swedish National Central Bureau of Statistics. PARTICIPANTS: The sample studied was identified in 1980-81 and comprised 14,757 persons aged 16-74. Of these, 12,695 (86%) consented to interview. MEASUREMENTS AND MAIN RESULTS: Information was obtained on adult height, socioeconomic status in childhood and adult life, self perceived health, self reported longstanding illness, and mortality during a six year follow up. The numbers of people in three height groups who considered their general health as bad, who reported any longstanding illness or who died during the follow up were compared with the expected numbers in the same groups. The number of persons with reduced health and the number of deaths was larger than expected in the shortest height group. The excess risk of dying in the shortest group (about 20% higher compared to the tallest group) was reduced but not eliminated when present and childhood socioeconomic group was taken into account. Coronary heart disease mortality in particular was linked to height. The shortest group of men and women reported the largest proportion with bad general health and longstanding illness. For the latter the differences between height groups disappeared after controlling for present socioeconomic status. CONCLUSIONS: There is a detectable excess risk of morbidity and mortality from being short. Assuming that the childhood environment is an important determinant of adult stature it is also important for adult health.  相似文献   
996.
1. The disposition of AY-30,068 (I), a new tetrahydrocarbazole analgesic drug, was studied in mice, rats, dogs, rhesus monkeys, and man. 2. Oral doses of the 14C-labelled drug in aqueous solution were well absorbed in rodents, but absorption of oral doses of the crystalline drug in dogs was poor. Due to the virtual absence of serum metabolites in rats and dogs, the bioavailability of I was nearly identical to the extent of absorption. Although a small first-pass effect was observed in mice, unchanged I represented a major portion of serum radioactivity. 3. A linear increase in the serum concentrations of I occurred at doses between 0.05 and 25 mg/kg in rats, 0.1 and 50 mg/kg in dogs, and 1-160 mg in man. In rhesus monkeys given a 0.5 mg/kg oral dose, the Cmax and AUC of I were similar to values obtained following a corresponding dose in dogs. 4. After i.v. administration of a 1.0 mg/kg dose the terminal elimination half-life (t1/2 beta) of I was 4 h in mice and 9-10 h in rats and dogs. In rodents, dogs, and several human subjects, the elimination of I was interrupted by secondary peaks. Enterohepatic circulation was confirmed in bile duct cannulated rats, where the t1/2 beta of I was decreased to 2.4 h. In rodents the serum clearance and apparent volume of distribution of I were 0.04-0.2 l/kg.h and 0.5-0.8 l/kg, respectively, and 0.6 l/kg.h and 9.8 l/kg in dogs. 5. In rodents and dogs dosed with 14C-labelled I, radioactivity was excreted almost entirely in the faeces. No unchanged I was detected in rat bile, while about 70% of the radioactivity corresponded to conjugates of parent drug.  相似文献   
997.
998.
999.
1000.
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