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   6318篇
  免费   486篇
  国内免费   7篇
耳鼻咽喉   35篇
儿科学   133篇
妇产科学   101篇
基础医学   1096篇
口腔科学   147篇
临床医学   556篇
内科学   1163篇
皮肤病学   91篇
神经病学   1083篇
特种医学   188篇
外科学   721篇
综合类   70篇
一般理论   1篇
预防医学   480篇
眼科学   98篇
药学   513篇
中国医学   6篇
肿瘤学   329篇
  2022年   53篇
  2021年   82篇
  2020年   56篇
  2019年   78篇
  2018年   107篇
  2017年   81篇
  2016年   129篇
  2015年   122篇
  2014年   171篇
  2013年   219篇
  2012年   297篇
  2011年   302篇
  2010年   177篇
  2009年   188篇
  2008年   303篇
  2007年   300篇
  2006年   277篇
  2005年   317篇
  2004年   242篇
  2003年   260篇
  2002年   246篇
  2001年   159篇
  2000年   173篇
  1999年   132篇
  1998年   88篇
  1997年   82篇
  1996年   53篇
  1994年   54篇
  1992年   92篇
  1991年   94篇
  1990年   98篇
  1989年   79篇
  1988年   90篇
  1987年   74篇
  1986年   81篇
  1985年   81篇
  1984年   61篇
  1983年   67篇
  1982年   62篇
  1981年   53篇
  1980年   53篇
  1979年   79篇
  1978年   68篇
  1977年   63篇
  1976年   53篇
  1974年   57篇
  1973年   54篇
  1972年   59篇
  1971年   55篇
  1968年   49篇
排序方式: 共有6811条查询结果,搜索用时 0 毫秒
31.
32.
We describe two unrelated patients with cytogenetically visible deletions of 21q22.2-q22.3 and mild phenotypes. Both patients presented minor dysmorphic features including thin marfanoid build, facial asymmetry, downward-slanting palpebral fissures, depressed nasal bridge, small nose with bulbous tip, and mild mental retardation (MR). FISH and molecular studies indicated common deleted areas but different breakpoints. In patient 1, the breakpoint was fine mapped to a 5.2 kb interval between exon 5 and exon 8 of the ETS2 gene. The subtelomeric FISH probe was absent on one homologue 21 indicating a terminal deletion spanning approximately 7.9 Mb in size. In patient 2, the proximal breakpoint was determined to be 300-700 kb distal to ETS2, and the distal breakpoint 2.5-0.3 Mb from the 21q telomere, indicating an interstitial deletion sized approximately 4.7-7.3 Mb. The 21q- syndrome is rare and typically associated with a severe phenotype, but different outcomes depending on the size and location of the deleted area have been reported. Our data show that monosomy 21q of the area distal to the ETS2 gene, representing the terminal 7.9 Mb of 21q, may result in mild phenotypes comprising facial anomalies, thin marfanoid build, and mild MR, with or without signs of holoprosencephaly.  相似文献   
33.
34.
Miltefosine is a novel antileishmanial drug that has significant selectivity in both in vitro and in vivo models. Clinical efficacy was demonstrated for the treatment of visceral leishmaniasis with the advantage of oral administration over the currently recommended antileishmanial drugs that require parenteral administration. Miltefosine produces high cure rates also in patients resistant to the standard antimonial therapy.  相似文献   
35.
The capacity of farm animals to produce cytokines could be an important determinant of robustness and health. From research in rodents and humans it appears that the production and the balance of T helper 1 (Th1) and T helper 2 (Th2)-type cytokines influences susceptibility to autoimmune and infectious diseases. It is known that pigs show a large variation in many immune response parameters. So far the extent of individual variation in the production of Th1- and Th2-type cytokines in commercial outbred pigs has not been reported. In the current experiment we determined mRNA expression, as well as protein production of cytokines in 32 pigs from eight litters. From each litter two male and two female pigs were tested at 2, 5 and 8 weeks of age. Two Th1-type cytokines, interleukin (IL)-2 and interferon (IFN)-gamma, and two Th2-type cytokines, IL-4 and IL-10, were measured after phytohaemagglutinin (PHA)-stimulation of blood mononuclear cells. Cytokine production and the Th1/Th2-ratio were highly variable. The variation in cytokine protein production was moderately consistent across ages, i.e. pigs that produced high levels of cytokine at 2 weeks of age tended to do so as well at 5 and 8 weeks of age. Cytokine production tended to increase with age, and gilts and boars differed in their IL-2/IL-4 ratio. Unexpectedly, age, gender and litter effects often differed for mRNA and protein production data. We hypothesize that cytokine production is a consistent trait in pigs, especially at the protein production level. Future investigations in more animals and across a wider age range are necessary.  相似文献   
36.
The aim of the present research was to study individual response specificity in 22 male patients having essential hypertension (HT) and to compare these patients with age-matched male normotensive controls (NT). Four stimuli, letter identification, mental arithmetic, cold pressor and isometric exercise, were administered while recordings were made of: systolic and diastolic blood pressures, heart rate, respiration, forearm and hand blood flows, and skin conductance level and fluctuations. After each session urine samples were collected and epinephrine and norepinephrine levels were analyzed. Twelve subjects in the HT group were given beta-adrenergic blocking agents and retested 1 to 21 months (X?= 12 months) after the first session. Each response was standardized, using NT as the reference group. Intraclass correlations were computed to evaluate whether HT males reacted with a more consistent hierarchy of responses than did NT. Intraclass correlations were significantly higher among the patients than in the control group, regardless of whether the blood pressure response was included or excluded in the computation of the intraclass correlations. Thus, we conclude that male HT patients show more individual response specificity than NT controls. Beta-adrenergic receptor antagonists reduced levels of cardiovascular activity and attenuated reactivity but did not affect amount of specificity. Thus, intraclass correlations provide unique and useful information, since they are not related to blood pressure reactivity or to urinary catecholamine levels, nor affected by beta-adrenergic blockade.  相似文献   
37.
A group of 83 men and women who had been referred to Johns Hopkins Hospital for cardiac catheterization for evaluation of chest pain and possible coronary artery bypass surgery were assessed behaviorally for their chest pains. During the approximately 2-week period between clinical evaluation and catheterization, the patients completed self-report forms about their chest pains. Patients completed one form for each episode of chest pain. Referring physicians also completed a form about the patients "typical" chest pain. The data were analyzed in terms of the antecedents, concomitants, and consequences of the chest pain, and patients' reports were compared to physicians' judgments. Major findings were as follows: 1) Antecedents--most episodes occurred while the patient was at home at times when his mood was one of contentment. 2) Concomitants--the average patient reported fewer than one episode per day which persisted for about 4 min and was rated as 36 on a scale of 0 to 100. The most common physical symptoms accompanying the episode were breathlessness and weakness, and the most common pain sensations were reported to be pressing or aching. There was no consistency among patients either in primary location or path of radiation of the pain. Duration of pain did not correlate significantly either with sensation or symptoms; however, severity rating did correlate with symptoms and sensations. 3) Consequences--most episodes were self-treated with nitroglycerin or rest. Patients typically returned to their ongoing activities; however, there were a number of interactions between the likelihood of returning to ones ongoing activity and the antecedents of the episodes. 4) The referring physicians significantly overestimated the frequency and severity of their patients' episodes; furthermore, they were selective in their abilities to identify correctly the antecedents or concomitants associated with their patients' pain--e.g., they were reliable in their judgments about subjects who had sleep-related episodes; however, they were inaccurate in characterizing the typical sensations or symptoms reported by their patients. It is suggested that a behavioral analysis may enable a physician to characterize his patient's chest complaints better, and perhaps also may facilitate the differentiation between chest complaints indicative of coronary artery disease and chest complaints of a noncoronary origin.  相似文献   
38.
39.
A hybridoma is described that exhibits all the characteristic features of Mott cells. It has spherules (Russell bodies) in the cytoplasm made up of dilated rough endoplasmatic reticulum and containing condensed immunoglobulin (λ1 light chains). Some of the cells appear to be very fragile, and free spherules are often found on cell smears. Cells with the Mott cell characteristics are still able to divide, but they do not secrete immunoglobulin. Hybridomas of this kind should be useful for determining the place of the Mott cell within the scheme of B cell differentiation.  相似文献   
40.
Sensorineural hearing loss is a common sequela of acute and chronic otitis media, and the round window membrane (RWM) is currently being considered as a major route for noxious agents to pass from the middle ear cavity to the cochlea. Streptococcus pneumoniae, a major causative agent of otitis media, and Streptococcus pyogenes A produce molecularly related toxins, pneumolysin and streptolysin O (SLO), that form large pores in target membranes. In this study, we analyzed the effects of SLO on the permeability of the RWM. Resected RWMs from a total of 104 guinea pigs were embedded between two chambers of an in vitro system. One chamber was designated as the tympanal (cis) compartment, and the other was designated as the inner ear (trans) compartment. The permeability of normal and SLO-damaged RWMs towards Na+, [14C]mannitol, and proteins was investigated. SLO evoked permeability defects dose dependently in the RWM with fluxes of both Na+ and [14C]mannitol being demonstrable over a time span of up to 8 h. Serum proteins and radioiodinated SLO were also shown to pass through the damage RWM. Scanning electron microscopy revealed the morphological correlates to these results. We propose that damage to the RWM by potent pore-forming cytolysins leads to leakage of ions from the perilymph. Ionic disequilibrium and passage of noxious macromolecules to the cochlea could contribute to disturbances of the inner ear function.  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