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   118584篇
  免费   7164篇
  国内免费   1580篇
耳鼻咽喉   1575篇
儿科学   2970篇
妇产科学   4107篇
基础医学   18291篇
口腔科学   3608篇
临床医学   9274篇
内科学   21611篇
皮肤病学   2436篇
神经病学   8001篇
特种医学   4018篇
外国民族医学   3篇
外科学   16743篇
综合类   5213篇
一般理论   34篇
预防医学   8680篇
眼科学   2818篇
药学   10197篇
中国医学   818篇
肿瘤学   6931篇
  2021年   981篇
  2019年   1045篇
  2018年   1609篇
  2017年   1166篇
  2016年   1196篇
  2015年   1443篇
  2014年   1883篇
  2013年   2439篇
  2012年   3542篇
  2011年   3794篇
  2010年   2284篇
  2009年   2047篇
  2008年   3378篇
  2007年   3612篇
  2006年   3597篇
  2005年   3162篇
  2004年   2976篇
  2003年   2769篇
  2002年   2627篇
  2001年   6730篇
  2000年   6921篇
  1999年   5695篇
  1998年   1829篇
  1997年   1377篇
  1996年   935篇
  1995年   862篇
  1992年   3728篇
  1991年   3806篇
  1990年   3549篇
  1989年   3552篇
  1988年   3428篇
  1987年   3277篇
  1986年   3090篇
  1985年   2967篇
  1984年   2048篇
  1983年   1792篇
  1982年   985篇
  1979年   1909篇
  1978年   1184篇
  1977年   986篇
  1976年   918篇
  1975年   1191篇
  1974年   1358篇
  1973年   1413篇
  1972年   1357篇
  1971年   1247篇
  1970年   1137篇
  1969年   1121篇
  1968年   1024篇
  1967年   897篇
排序方式: 共有10000条查询结果,搜索用时 16 毫秒
221.
Purified murein from Thiobacillus neapolitanus was poorly digested by lysozyme. It's sensitivity to the enzyme greatly increased after N-acetylation. The murein was found to contain 30 to 35% glucosamine residues lacking N-acetyl groups. It also contained phosphomuramic acid. Further modifications included amidation of diaminopimelic acid in the peptide side chains and a low alanine content. None of these modifications were found in the murein of another sulphur bacterium, Thiobacillus versutus.  相似文献   
222.
Respiratory symptoms and ventilatory capacity in swine confinement workers.   总被引:1,自引:0,他引:1  
A group of 59 workers (41 men and 18 women) employed in swine confinement areas was studied to assess the presence of acute and chronic respiratory symptoms and the prevalence of abnormalities in ventilatory function. A control group of 46 (31 men and 15 women) unexposed workers was studied for the prevalence of chronic respiratory symptoms. For both male and female swine confinement workers complaints of chronic cough, dyspnoea, and chest tightness were significantly more frequent than among control workers. Male workers also complained more of chronic phlegm. Male swine confinement workers who were smokers had significantly higher prevalences of chronic cough, chronic phlegm, and chronic bronchitis than male non-smoking swine confinement workers. The frequency of acute symptoms associated with the workshift was high among the swine confinement workers with more than half of the workers complaining of cough and dyspnoea associated with work. Significant acute across shift reductions in lung function occurred in swine confinement workers, being largest for FEF25. All Monday preshift ventilatory capacity measurements in male confinement workers were significantly lower than predicted values; FVC and FEV1 were found to be lower than predicted values for women. The data indicate that exposure in swine confinement buildings is associated with the development of acute and chronic respiratory symptoms and impairment of lung function. Smoking appears to aggravate these changes.  相似文献   
223.
In 1984 a late malaria endemic area, called Bodrogk?z was studied. This was a reexamination of the population genetic work performed by Walter, Nemeskéri. In six villages of Bodrogk?z 328 persons were tested for AB0, Rh blood groups, haptoglobins, haemoglobin concentration, haematocrit, erythrocyte amount, the MCV, the MCH and the G-6-PD were analyzed. The quantitative determination of HbF and HbA2, red cell osmotic resistance and thalassemia were measured as well. Thalassemia heterozygote carriers and an increased level of HbF were revealed. The frequency of G-6-PD deficiency was 0.39%. In Bodrogk?z the frequencies of AB0, Rh and haptoglobin types were similar in the present and all previous studies. The background of this similarity might be the genetic similarity between two following generations. On the basis of these facts, the Hb0 Arab and partially DNA work we suggested an alternative hypothesis that these mutant genes got into Bodrogk?z by the rather later migration than with ancient Hungarian people during the period of conquest of Hungary.  相似文献   
224.
This exploratory study examined the family environment of ten families, each with a physically disabled adolescent and at least one non-disabled adolescent. Family members completed the Moos Family Environment Scale (FES) and discussed with the interviewer their experiences as a family. Blind and independent ratings on the FES by social workers involved in the study provided a comparison with the families' self ratings. Family ratings on the FES gave no indication of distress, but showed slightly higher than average emphasis on cohesion and achievement orientation. Social work ratings, in contrast, indicated elevated levels of conflict, achievement orientation, and control. In this report, no attempt is made to generalize these specific findings to all families with disabled adolescents. Rather, results are interpreted, in the light of findings in the recent literature, to underscore the need for better designed research and to alert professionals to the danger of imposing the prevalent dysfunctional view upon families with disabled children and adolescents.  相似文献   
225.
Twenty-five patients with primary presentation of malignant astrocytoma, astrocytoma with anaplastic foci, and glioblastoma multiforme were treated with surgical resection and definitive radiation therapy followed by intravenous or intra-arterial administration of Iodine-125 labeled monoclonal antibody-425, which binds specifically to human epidermal growth factor receptor. The patients presented with primary untreated disease, positive contrast enhanced computed tomography scans of the brain, and compatible clinical symptoms. In this Phase II clinical trial, the patients had surgical debulking or biopsy followed by definitively administered external beam radiation therapy and one or multiple doses (35 to 90 mCi per infusion) of radiolabeled antibody. The total cumulative doses ranged from 40 to 224 mCi. The administrations of the radiolabeled antibody were performed in most cases 4-6 weeks following completion of the primary surgery and radiation therapy. Ten patients had astrocytoma with anaplastic foci and 15 had glioblastoma multiforme. No significant life-threatening toxicities were observed during this trial. At 1 year 60% of the patients with astrocytoma with anaplastic foci or glioblastoma multiforme are alive. The median survival for both groups was 15.6 months.  相似文献   
226.
Between November 1988 and February 1992, 416 patients required coronary endarterectomy for diffuse coronary artery disease. This constitutes 16.19 per cent of all patients who underwent coronary artery bypass grafting during the same period. A total of 528 endarterectomies were performed. Four-hundred and twenty-two endarterectomies were performed on right coronary system and 106 endarterectomies were performed on left coronary system. One-hundred and twelve (26.92%) patients required more than one endarterectomies. The hospital mortality was 2.16 percent. 3.37 per cent of patients had perioperative infarction. Intraaortic balloon pump was required in 1.92 per cent of patients. 5.77 per cent of the patients had significant arrhythmias. The patients have been followed up for a mean period of 27 months. One-hundred and forty patients were evaluated by exercise multigated radionuclide angiogram. One-hundred and thirty-four (95.71%) patients showed increase in ejection fraction as compared to preoperative value. Six (4.29%) patients did not show any significant change while eight (5.71%) patients had fall in ejection fraction. Postoperative coronary angiogram was done in 44 patients at a mean of 10 months. 89.59 per cent of grafts to the endarterectomised vessels and 91.67% of grafts to nonendarterectomised vessel were patent. The difference between the two groups was not statistically significant.  相似文献   
227.
The responses of human neocortical neurons to iontophoretic application of excitatory amino acids and their modulation by dopamine (DA) were studied in vitro. Brain slices were obtained from children undergoing surgery for intractable epilepsy. Application of N-methyl-D-aspartate (NMDA) to the slices induced slow depolarizations accompanied by decreased input conductances and sustained action potentials in cortical neurons. Glutamate produced rapid depolarizations and firing with few changes in input conductances. Quisqualate also induced depolarization and firing, but input conductances increased during the rising phase of the membrane depolarization. Iontophoretic application of DA alone produced no change in membrane potential or input conductance. However, when DA was applied in conjunction with the excitatory amino acids, it produced contrasting effects. With either bath application of DA or when iontophoresis of DA preceded application of NMDA, the amplitude of the membrane depolarizations and the number of action potentials were increased, whereas the latency of these responses decreased. In contrast, DA decreased the amplitude of the depolarizations and the number of action potentials evoked by glutamate or quisqualate. The fact that DA affects responses to NMDA and glutamate or quisqualate in opposite directions is of considerable importance to the understanding of cellular mechanisms of neuromodulation and the role of DA in cognitive processing and in epilepsy.  相似文献   
228.
229.
Oxygen consumption of the rabbit femoral artery after hemorrhagic shock was studied. Hemorrhagic shock was initiated and maintained at 60 mm Hg of systolic blood pressure for 2 hours. A significant reduction in femoral artery oxygen consumption was observed after hemorrhagic shock (1.64 +/- 0.14 microliter/g/hr) when compared to oxygen consumption in the normal condition (2.52 +/- 0.22 microliter/g/hr). Application of the beta-agonist isoproterenol significantly increased oxygen consumption in the isolated femoral artery after hemorrhagic shock (2.66 +/- 0.20 microliter/g/hr), but did not exceed the normal values recorded without stimulation. Also, isoproterenol significantly increased oxygen consumption in the femoral artery of nonhemorrhagic condition (4.84 +/- 0.42 microliter/g/hr). The increase in oxygen consumption conditioned by isoproterenol was significantly lower after hemorrhagic shock compared with values in the nonhemorrhagic state. The data suggest that oxygen consumption is regulated by beta-adrenergic receptors, and the phenomenon of diminished oxygen consumption after hemorrhagic shock probably occurs because of changes in beta-adrenergic receptors, causing the appearance of change in the mechanism of oxygen consumption.  相似文献   
230.
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