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   2274篇
  免费   188篇
  国内免费   4篇
耳鼻咽喉   42篇
儿科学   36篇
妇产科学   23篇
基础医学   345篇
口腔科学   23篇
临床医学   258篇
内科学   370篇
皮肤病学   36篇
神经病学   150篇
特种医学   114篇
外科学   361篇
综合类   15篇
一般理论   1篇
预防医学   158篇
眼科学   88篇
药学   170篇
中国医学   8篇
肿瘤学   268篇
  2024年   4篇
  2023年   37篇
  2022年   66篇
  2021年   127篇
  2020年   59篇
  2019年   92篇
  2018年   93篇
  2017年   59篇
  2016年   58篇
  2015年   68篇
  2014年   100篇
  2013年   123篇
  2012年   172篇
  2011年   145篇
  2010年   81篇
  2009年   87篇
  2008年   109篇
  2007年   117篇
  2006年   106篇
  2005年   99篇
  2004年   90篇
  2003年   76篇
  2002年   60篇
  2001年   63篇
  2000年   46篇
  1999年   52篇
  1998年   15篇
  1997年   16篇
  1996年   13篇
  1995年   12篇
  1994年   5篇
  1993年   10篇
  1992年   32篇
  1991年   20篇
  1990年   27篇
  1989年   22篇
  1988年   28篇
  1987年   8篇
  1986年   14篇
  1985年   7篇
  1984年   7篇
  1983年   3篇
  1981年   3篇
  1979年   4篇
  1974年   4篇
  1972年   4篇
  1971年   4篇
  1970年   4篇
  1969年   4篇
  1968年   3篇
排序方式: 共有2466条查询结果,搜索用时 0 毫秒
1.
2.
A randomized, placebo-controlled, double-blind study involving 60 subjects, aged 6-18 years old, was conducted over a period of 3 months to determine the effect of Pycnogenol® (a proprietary mixture of water-soluble bioflavonoids extracted from French maritime pine) on mild-to-moderate asthma. After baseline evaluation, subjects were randomized into two groups to receive either Pycnogenol® or placebo. Subjects were instructed to record their peak expiratory flow with an Assess® Peak Flow Meter each evening. At the same time, symptoms, daily use of rescue inhalers (albuterol), and any changes in oral medications were also recorded. Urine samples were obtained from the subjects at the end of the run-in period, and at 1-, 2-, and 3-month visits. Urinary leukotriene C4/D4/E4 was measured by an enzyme immunoassay. Compared with subjects taking placebo, the group who took Pycnogenol® had significantly more improvement in pulmonary functions and asthma symptoms. The Pycnogenol® group was able to reduce or discontinue their use of rescue inhalers more often than the placebo group. There was also a significant reduction of urinary leukotrienes in the Pycnogenol® group. The results of this study demonstrate the efficacy of Pycnogenol® as an adjunct in the management of mild-to-moderate childhood asthma.  相似文献   
3.
4.
5.
1‐Benzyl‐4‐hydroxy[2‐14C]piperidine, a useful intermediate in labeled compound synthesis, was prepared from [14C]formaldehyde in high yield. The distribution pattern of 14C in the product is consistent with a mechanism involving reversible iminium ion formation and rapid equilibration of the iminium ion through a cationic aza‐Cope rearrangement. These steps precede the rate‐determining intramolecular cyclization step. SCH 351125 is a potent, selective CCR5 receptor antagonist with potential as a treatment for HIV infection. [14C]SCH 351125, required for metabolism studies, was prepared from 1‐benzyl‐4‐hydroxy[2‐14C]piperidine in six steps. [14C]SCH 351125 is a mixture of four atropisomers. Preparation of [14C]SCH 351125 besylate salt of the desired atropisomer pair is also described. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   
6.
The release of newly synthesized 3H-dopamine (3H-DA) was measured in the rat striatum superfused, through a push-pull cannula, with a physiological medium enriched in 3H-tyrosine. The level of spontaneous 3H-DA release was dependent on the topographical localisation of the cannula in the striatum (anterior parts displayed higher levels than posterior ones) and on the anesthetic state (halothane anesthetized rats demonstrated higher levels than awake ones). Inhibition of DA inactivation processes by local application of benztropine (a DA reuptake inhibitor, 10−6 M) or by IV administration of pargyline (a MAO inhibitor, 100 mg/kg) enhanced the detectable outflow of 3H-DA from the striatum in both halothane anesthetized and awake rats. Local application of D-amphetamine (10−5 M) or acetylcholine (5 × 10−5 M) in the presence of eserine (5 × 10−5 M) evoked respectively a fivefold and a 30% increase in spontaneous 3H-DA release in halothane anesthetized rats. Inhibition of the firing of dopaminergic neurons by IV injection of gamma-hydroxybutyrate (400 mg/kg) produced a 30% decrease in striatal 3H-DA release. The present results demonstrate that the push-pull cannula method is suitable for the study of DA release in both the anesthetized and the awake rat.  相似文献   
7.
8.
A newborn term male infant was found to have the stigmata of VACTERL syndrome, including cervical and thoracic hemivertebra, partial sacral agenesis, 13 pairs of ribs, high imperforate anus with rectovesical fistula, and tracheoesophageal fistula with proximal esophageal atresia. No open spinal dysraphism or skin dimpling was seen. Ultrasonography of the spinal cord was performed to screen for occult anomalies. The examination revealed a lipoma of the filum terminalis and a low-lying conus medullaris at the L3-L4 level with a large central cystic structure in the terminal cord, which was continuous with the central canal (Fig. 1). This was thought to most likely represent a dilated ventriculus terminalis, and the diagnosis was confirmed on a subsequent MR image (Fig. 2). Fluid in the cyst followed cerebrospinal fluid signal in all sequences. We observed no abnormal signal in the adjacent parenchyma or enhancement associated with the cystic mass. A cranial ultrasonogram did not reveal any intracranial anomalies. The patient demonstrated no neurologic deficits in the lower extremities. Bowel and urinary continence was not assessable in this infant.  相似文献   
9.
n-Hexacosanol (hexa), a long chain fatty alcohol extracted from Hygrophila erecta, has proved to possess neurotrophic activities on cultured neurons, and to attenuate the degeneration of cholinergic neurons after injury. In the present study, we show that hexa has also interesting properties on macrophages, a cell type largely represented in the brain: when added to mice resident peritoneal macrophages, it provokes significant morphological changes, and increases their phagocytosis capacity. These results may indicate that some membrane properties involved in these different effects and in macrophage functions are affected by n-hexacosanol, but other sites of action could also be considered.  相似文献   
10.
BACKGROUND.: Mercuric chloride (HgCl2 induces a lymphoproliferative disorderand autoimmune glomerulonephritis in Brown Norway (BN) rats.This syndrome is the consequence of T cell-dependent polyclonalB cell activation and autoantibody production. We have previouslyshown that HgCl2-induced autoimmune perturbations can be preventedin BN rats by the administration of cyclosporin A (CsA). Themost potent vitamin D3 metabolite 1,25(OH)2 D3 (Vit D3) sharescertain immunomodulatory properties with CsA. We therefore choseto compare the effects of Vit D3 to those of CsA in BN ratstreated with HgCl2 in order to establish whether Vit D3 eitheralone or in combination with CsA can attenuate an autoimmunesyndrome in vivo. METHODS.: BN rats were treated with HgCl2 according to a standard protocol.Subgroups of rats were also given CsA alone, Vit D3 or syntheticanalogues of Vit D3 alone, or combinations of both agents. Differentdoses and routes of administration were compared. The followingmarkers of disease activity were evaluated: mortality, peakproteinuria, serum IgE concentrations, and renal immunoglobulindeposition. RESULTS.: Disease activity was markedly attenuated in all rats treatedwith CsA alone. Vit D3 and certain of its synthetic analoguesadministered alone also tempered the autoimmune process, butto a lesser extent than did CsA. The effect of CsA alone wasso potent, that no additive or synergistic effects could bedemonstrated when CsA was administered in combination with VitD3. CONCLUSIONS.: Despite similar described immunomodulatory effects in vitro,CsA is clearly more effective than Vit D3 in preventing HgCl2autoimmune disease in BN rats. This suggests that there is adifference in the cellular targets of these two agents in vivo,and/or a difference in the potency with which HgCl2-triggeredimmune activation is suppressed.  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