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   3451642篇
  免费   248031篇
  国内免费   6136篇
耳鼻咽喉   47037篇
儿科学   112635篇
妇产科学   94013篇
基础医学   498863篇
口腔科学   98379篇
临床医学   313756篇
内科学   664463篇
皮肤病学   77039篇
神经病学   272401篇
特种医学   129179篇
外国民族医学   693篇
外科学   518395篇
综合类   76027篇
现状与发展   14篇
一般理论   1255篇
预防医学   267455篇
眼科学   82726篇
药学   254918篇
  13篇
中国医学   7545篇
肿瘤学   189003篇
  2021年   26908篇
  2019年   27786篇
  2018年   39068篇
  2017年   29485篇
  2016年   32936篇
  2015年   37187篇
  2014年   52411篇
  2013年   78210篇
  2012年   107878篇
  2011年   114344篇
  2010年   68233篇
  2009年   64011篇
  2008年   106785篇
  2007年   113792篇
  2006年   115064篇
  2005年   111047篇
  2004年   106822篇
  2003年   102397篇
  2002年   98850篇
  2001年   163025篇
  2000年   167356篇
  1999年   140363篇
  1998年   39871篇
  1997年   34859篇
  1996年   35055篇
  1995年   33259篇
  1994年   30582篇
  1993年   28585篇
  1992年   108255篇
  1991年   105215篇
  1990年   101947篇
  1989年   98364篇
  1988年   90207篇
  1987年   88299篇
  1986年   83065篇
  1985年   79491篇
  1984年   59020篇
  1983年   50291篇
  1982年   29369篇
  1979年   53693篇
  1978年   37867篇
  1977年   31794篇
  1976年   30151篇
  1975年   32057篇
  1974年   38834篇
  1973年   37188篇
  1972年   34719篇
  1971年   32641篇
  1970年   30285篇
  1969年   28638篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Oncologic screenings of the populations in the areas with increased incidence of esophageal cancer have revealed Barrett's ulcer in 1 percent of the examinees. Endoscopic and cytologic characteristics of this condition are presented. Precancer changes--severe dysplasia--are most frequent in male Kazakhs (14.1 percent) aged 50 to 59 (14.7 percent). Subjects with Barrett's ulcer developing severe dysplasia, as evidenced by cytograms, should be included in the group of subjects at risk for carcinoma of the lower third of the esophagus and cardia.  相似文献   
992.
993.
994.
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   
995.
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   
996.
997.
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   
998.
J S Li 《中华外科杂志》1989,27(10):629-33, 640
Serum aminogram changes were prospectively studied in 95 patients with enteric fistula and intraabdominal infection who was under total parenteral nutrition (TPN) therapy with Anfuming 14s. In patients with sepsis and starvation, the aminogram showed remarkably low total free amino acids before TPN therapy. In 81 survivors, free amino acids increased gradually to normal in 2 weeks after use of TPN and in 14 dead cases increased rapidly to a significantly higher peak at terminal stage. Both in survivors and nonsurvivors, phenylalanine level remained high during the study. In response to infection, proline was also elevated but to a lesser degree; the ratio of branched chain amino acid (BCAA) to aromatic amino acid (AAA) was lower than normal and the decrease of arginine was parallel to the severity of infection. We conclude that the ideal amino acids preparation for the starvated and septic patients should be high in BCAA and arginine but low in phenylalanine, administration of inappropriate exogenous amino acids in decompensated metabolic septic patients may bring about more harm than benefit, and in septic patients that the levels of serum phenylalanine and proline are elevated persistently along with the decrease of arginine level is a useful prognostic indication.  相似文献   
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