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   3461965篇
  免费   283728篇
  国内免费   13398篇
耳鼻咽喉   47079篇
儿科学   110034篇
妇产科学   90139篇
基础医学   550712篇
口腔科学   93599篇
临床医学   316403篇
内科学   611016篇
皮肤病学   91652篇
神经病学   296424篇
特种医学   134490篇
外国民族医学   288篇
外科学   526593篇
综合类   102533篇
现状与发展   24篇
一般理论   2419篇
预防医学   297807篇
眼科学   78424篇
药学   236621篇
  27篇
中国医学   9378篇
肿瘤学   163429篇
  2021年   55617篇
  2020年   35392篇
  2019年   58478篇
  2018年   72048篇
  2017年   54871篇
  2016年   60326篇
  2015年   74392篇
  2014年   108648篇
  2013年   173883篇
  2012年   96627篇
  2011年   97137篇
  2010年   117706篇
  2009年   121774篇
  2008年   83360篇
  2007年   87014篇
  2006年   96594篇
  2005年   92152篇
  2004年   93490篇
  2003年   84007篇
  2002年   73723篇
  2001年   102689篇
  2000年   95368篇
  1999年   95450篇
  1998年   64646篇
  1997年   62659篇
  1996年   60793篇
  1995年   56232篇
  1994年   50479篇
  1993年   47166篇
  1992年   67678篇
  1991年   64909篇
  1990年   61523篇
  1989年   60713篇
  1988年   56527篇
  1987年   55295篇
  1986年   52716篇
  1985年   52316篇
  1984年   48194篇
  1983年   44354篇
  1982年   41719篇
  1981年   39436篇
  1980年   37171篇
  1979年   40697篇
  1978年   36281篇
  1977年   32854篇
  1976年   30139篇
  1975年   29029篇
  1974年   30509篇
  1973年   29626篇
  1972年   27885篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
Summary Split or full thickness eyelid defects resulting from tumor destruction or surgical excision present a dilemma for plastic and reconstructive surgeons. Full thickness eyelid replacement requires composite grafting of the skin, together with tarsal support of its substitute and mucosa. The flap described by Fricke in 1829 was used for reconstruction of anterior lamella in six lower eyelid defects. In three of our cases chondromucosal grafts taken from nasal septum were utilized for posterior lamella repair. The results have been satisfactory from a functional and cosmetic standpoint.  相似文献   
992.
993.
E Bartoli  G F Branca  A Satta  R Faedda 《Nephron》1987,46(3):288-300
In a previous study, we described a new method [3] to measure Na reabsorption by each segment of the human nephron independently. Reabsorption was expressed as equivalent volumes of solute-free water (CH2O) generated by the loop of Henle (CH2O-HL) and by the distal tubule (CH2O-DT), and dissipated by back diffusion (BD) across collecting ducts (CH2O-BD). These data were obtained during maximal water diuresis (MWD). The present study was undertaken to calculate CH2O-HL by experiments performed during maximal antidiuresis (MA). For this purpose, a new theoretical approach was devised, described by algebraic equations which allowed calculations of segmental transport during MA alone, where only CH2O-HL could be calculated independently. The study was performed on 14 normal volunteers who were studied twice by clearance measurements, firstly during MWD and again during MA. In each experiment, clearance periods were performed during baseline conditions and during the administration of furosemide (0.7 mg/kg bolus injection followed by 0.06 mg/kg/min maintenance infusion). From the values measured during either condition, segmental reabsorption was calculated. During MWD, CH2O-HL averaged 19.4 + 10.4, during MA 20.4 + 8.0 ml/min/GFR X 100; p greater than 0.05. The paired measurements were significantly correlated (r = 0.80; p less than 0.01). These data demonstrate that CH2O-HL obtained with the original theory is a reproducible result that can be confirmed with independent measurements obtained during different experimental conditions. Thus, measurements of segmental Na transport in the human nephron are feasible and can contribute important informations on disease states.  相似文献   
994.
ABSTRACT. A 54-year-old profoundly mentally retarded female patient with phenylketonuria and a severe behaviour problem was treated with a restricted protein and high energy diet. After several weeks of dietary intervention the patient's behaviour improved significantly.  相似文献   
995.
The percentage uptake of [123I]metaiodobenzylguanidine (MIBG) by tumors of the paraganglion system is compared with the number of neurosecretory granules (assessed by both light and electron microscopy) in the subsequently resected tumors in six patients. Iodine-123 MIBG was injected intravenously; the tumor uptake of [123I]MIBG varied between 0.001% and 0.14% of the injected dose per gram of tumor tissue at 22 hr. The number of neurosecretory granules in tissue sections was scored on a scale of I-III. A direct proportional correlation was found between the percentage uptake of [123I]MIBG by the tumor and the number of neurosecretory granules in the tissue sections but not with plasma or urinary catecholamines. This technique for imaging reflects the storage status of the tumor better than plasma and urinary catecholamine measurements.  相似文献   
996.
Endogenous opioids are present in neurons of the vagus and the intrinsic nervous system and they are colocalized with gastrin in antral G-cells. This raises the possibility that endogenous opioids modulate gastrin release. Stimulation of both cervical vagi (10V, 5Hz, 5ms) elicited an increase of arterial plasma gastrin levels at intragastric pH7 or pH2. The response at pH2 was 30% of that at luminal pH7. Atropine reduced vagally stimulated gastrin levels substantially. At luminal pH2 the small residual noncholinergic response was mediated neither by adrenergic mechanisms nor by endogenous opioids. At luminal pH 7 adrenergic blockade with phentolamine and propranolol reduced vagally stimulated gastrin by 60%. In the presence of atropine adrenergic blockade elicited only a small inhibitory effect suggesting that vagal activation of adrenergic mechanisms depends on atropine-sensitive cholinergic pathways. Blockade of opiate receptors by naloxone had no effect on vagal gastrin release, however, the noncholinergic gastrin response was reduced significantly by naloxone, suggesting that cholinergic mechanisms normally restrain activation of endogenous opioids during vagal stimulation. Naloxone had no effect on the noncholinergic, nonadrenergic stimulation of gastrin levels. These data suggest that endogenous opioids can contribute to vagal gastrin release provided the cholinergic restraint is blocked and adrenergic mechanisms stimulate endogenous opioids. In conclusion a major role of endogenous opioids in the regulation of vagal gastrin release can not be detected.  相似文献   
997.
Using radioimmunoassay the authors investigated the plasma concentration of the immunoreactive atrial natriuretic factor (IR-ANF) and its content in the atria of 4-, 8-, 12-, 16-, and 20-weeks-old spontaneously hypertensive rats (SHR), and compared the results with data obtained in normotensive Wistar-Kyoto rats of the same age. With hypertension accelerating in SHR between the 8th and the 20th weeks of life, IR-ANF content in the atrium gradually decreased, and the plasma IR-ANF concentration increased. The decline in IR-ANF was due to its decrease primarily in the left atrium. Long-term (6-day) administration of synthetic ANF to SHR with fully developed hypertension led to normalization of BP. The results do not support the hypothesis that arterial hypertension in SHR is induced by a primary deficiency of ANF. The changes in IR-ANF in the atria and plasma occur rather as an adaptive and regulatory response to increasing BP. Prolonged administration of ANF to SHR had a hypotensive effect. Therapeutic application of ANF in man depends on the development of oral and long-acting analogues.  相似文献   
998.
Abstract A high frequency of serum complement component C4A deficiency may explain the higher prevalence and greater severity of systemic lupus erythematosus reported in Australian Aborigines. Inherited deficiencies of serum complement components C4A, C4B, and C2 were examined in two Australian Aboriginal populations from Darwin and Alice Springs and compared with the prevalence of complement deficiencies in white Australian blood donors. The frequency of C4A deficiency alleles was 29% in Darwin Aborigines compared with 12% in Alice Springs and 17% in Canberra blood donors. Partial C4B deficiency was also higher in Darwin Aborigines than in the other populations. Inherited deficiency of serum complement component C2 was not observed.  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