全文获取类型
收费全文 | 708篇 |
免费 | 39篇 |
专业分类
儿科学 | 31篇 |
妇产科学 | 7篇 |
基础医学 | 75篇 |
口腔科学 | 14篇 |
临床医学 | 104篇 |
内科学 | 135篇 |
皮肤病学 | 14篇 |
神经病学 | 105篇 |
特种医学 | 131篇 |
外科学 | 25篇 |
综合类 | 13篇 |
预防医学 | 21篇 |
眼科学 | 2篇 |
药学 | 48篇 |
中国医学 | 1篇 |
肿瘤学 | 21篇 |
出版年
2022年 | 6篇 |
2021年 | 9篇 |
2019年 | 5篇 |
2018年 | 10篇 |
2017年 | 5篇 |
2016年 | 7篇 |
2015年 | 14篇 |
2014年 | 9篇 |
2013年 | 37篇 |
2012年 | 19篇 |
2011年 | 15篇 |
2010年 | 27篇 |
2009年 | 32篇 |
2008年 | 12篇 |
2007年 | 8篇 |
2006年 | 9篇 |
2005年 | 10篇 |
2004年 | 14篇 |
2003年 | 15篇 |
2002年 | 12篇 |
2001年 | 14篇 |
2000年 | 16篇 |
1999年 | 23篇 |
1998年 | 34篇 |
1997年 | 32篇 |
1996年 | 35篇 |
1995年 | 29篇 |
1994年 | 25篇 |
1993年 | 22篇 |
1992年 | 13篇 |
1991年 | 21篇 |
1990年 | 12篇 |
1989年 | 21篇 |
1988年 | 17篇 |
1987年 | 20篇 |
1986年 | 11篇 |
1985年 | 15篇 |
1984年 | 12篇 |
1983年 | 9篇 |
1982年 | 11篇 |
1981年 | 10篇 |
1980年 | 4篇 |
1979年 | 10篇 |
1978年 | 8篇 |
1977年 | 18篇 |
1976年 | 9篇 |
1975年 | 14篇 |
1974年 | 2篇 |
1968年 | 2篇 |
1966年 | 1篇 |
排序方式: 共有747条查询结果,搜索用时 15 毫秒
1.
Liver hemangioma: US-guided 18-gauge core-needle biopsy 总被引:6,自引:0,他引:6
2.
P Sacerdote F Rubboli L Locatelli I Ciciliato P Mantegazza A E Panerai 《Journal of neuroimmunology》1991,32(1):35-41
The concentrations of beta-endorphin and cholecystokinin were measured in fresh resting peripheral mononuclear cells obtained from rats and human subjects in basal conditions and after different pharmacological treatments. Both in the human and the rat, beta-endorphin concentrations in mononuclear cells, increased after treatment with serotoninergic agonists, decreased after dopaminergic or GABAergic drugs, while the respective antagonists exerted the opposite effect. In vitro, serotoninergic and GABAergic compounds confirmed their roles in the modulation of beta-endorphin in mononuclear cells. Cholecystokinin was never affected by the pharmacological treatments. 相似文献
3.
BACKGROUND: There are obvious advantages to increasing donor retention. However, for reasons of blood safety, certain donors may, in fact, be more desirable to retain than others. “Safe” donors are defined as those who provided a blood donation that was negative on all laboratory screening tests and who subsequently reported no behavioral risks in response to an anonymous survey. This study identifies the most important factors affecting the intention of “safe” donors to provide another donation. STUDY DESIGN AND METHODS: An anonymous survey asking about donation history, sexual history, injecting drug use, and recent donation experience was mailed to 50,162 randomly selected allogeneic donors (including directed donors) who gave blood from April through July or from October through December 1993 at one of the five United States blood centers participating in the Retrovirus Epidemiology Donor Study. Before mailing, questionnaires were coded to designate donors with nonreactive laboratory screening tests at their most recent donation. RESULTS: A total of 34,726 donors (69%) responded, with substantially higher response among repeat donors. According to reported intentions only, the vast majority of “safe” donors indicated a high likelihood of donating again within the next 12 months. Only 3.4 percent reported a low likelihood of donating again. A comparison of those likely to return and those unlikely to return reveals significant differences in demographics and in ratings of the donation experience. A higher proportion of those unlikely to return were first-time donors, minority-group donors, and donors with less education. The highest projected loss among “safe” donors was seen for those who gave a fair to poor assessment of their treatment by blood center staff or of their physical well-being during or after donating. CONCLUSION: These data suggest that efforts to improve donors' perceptions of their donation experience, as well as attention to the physical effects of blood donation, may aid in the retention of both repeat and first-time donors. 相似文献
4.
We determined morphine plasma concentrations in 6 cancer patients before and with administration of diclofenac for 5 days. The non-steroidal anti-inflammatory drug does not modify morphine bioavailability. This observation suggests that diclofenac can be used in association with morphine during cancer pain treatment, without increasing the risk of overdosage or side effects of the opiate. 相似文献
5.
Normal or pregnant rats were treated orally for 21 days or throughout pregnancy with water or increasing doses of morphine and killed on days 7, 14, and 21 of pregnancy and 1 day post partum. At these time intervals, plasma, pituitary, and hypothalamic concentrations of beta-endorphin and methionine enkephalin were measured in normal and pregnant rats. Moreover, pituitary and hypothalamic concentrations of the two peptides were also measured in fetuses and newborn. Plasma beta-endorphin and methionine enkephalin increased significantly during pregnancy without any specific effect of morphine. Pituitary concentrations of beta-endorphin were not modified either by pregnancy or morphine treatment, while methionine enkephalin concentrations increased on days 7 and 11 of pregnancy, in both water- and morphine-treated rats. The pattern of the two peptides in the hypothalamus is completely superimposable to the one present in the pituitary with the exception of an increase of beta-endorphin on day 21 of pregnancy, which is more evident in control animals. Consistently with our observations in human newborn and the neurological dysfunctions we observed in them, the concentrations of both the peptides are significantly increased in the hypothalamus of fetuses and newborn of morphine-treated mothers, while in the pituitary only beta-endorphin concentrations are increased. 相似文献
6.
Steenbergen EJ; Verhagen OJ; van Leeuwen EF; van den Berg H; von dem Borne AE; van der Schoot CE 《Blood》1995,86(2):692-702
Crosslineage T-cell receptor delta (TCR delta) rearrangements are widely used as tumor markers for the follow up of minimal residual disease in childhood B-precursor acute lymphoblastic leukemia (ALL) by polymerase chain reaction (PCR). The major drawback of this approach is the risk of false-negative results due to clonal evolution. We investigated the stability of V delta 2D delta 3 rearrangements in a group of 56 childhood B-precursor ALL patients by PCR and Southern blot analysis. At the PCR level, V delta 2D delta 3-to-J alpha rearranged subclones (one pathway for secondary TCR delta recombination) were demonstrated in 85.2% of V delta 2D delta 3-positive patients tested, which showed that small subclones are present in the large majority of patients despite apparently monoclonal TCR delta Southern blot patterns. Sequence analysis of V delta 2D delta 3J alpha rearrangements showed a biased J alpha gene usage, with HAPO5 and J alpha F in 26 of 32 and 6 of 32 clones, respectively. Comparison of V delta 2D delta 3 rearrangement status between diagnosis and first relapse showed differences in seven of eight patients studied. In contrast, from first relapse onward, no clonal changes were observed in six patients studied. To investigate the occurrence of crosslineage TCR delta rearrangements in normal B and T cells, fluorescence-activated cell sorter-sorted peripheral blood CD19+/CD3- and CD19-/CD3+ cell populations from three healthy donors were analyzed. V delta 2D delta 3 rearrangements were detected at low frequencies in both B and T cells, which suggests that V delta 2-to-D delta 3 joining also occurs during normal B-cell differentiation. A model for crosslineage TCR delta rearrangements in B-precursor ALL is deduced that explains the observed clonal changes between diagnosis and relapse and is compatible with multistep leukemogenesis of B-precursor ALL. 相似文献
7.
AE Castellano G Micieli P Bellantonio MG Buzzi S Marcheselli F Pompeo F Rossi G Nappi 《Cephalalgia : an international journal of headache》1998,18(9):622-630
Intracerebral vascular reactivity induced by the nitric oxide (NO) donor isosorbide dinitrate (IDN, 5 mg sublingually) is more major and longer-lasting in migraine patients who develop delayed headache in response to the drug. The headache is purportedly due to neuronally-mediated vascular mechanisms. Indomethacin inhibits prostaglandin synthesis, which is involved in NO generation. Indomethacin also decreases cerebral blood flow by constricting precapillary resistance vessels. In the present study, the hemodynamic effects of indomethacin were evaluated in migraine patients and healthy controls by means of transcranial Doppler monitoring. Indomethacin caused a significant decrease in mean flow velocity in the middle cerebral artery. This was an additional effect to the mean velocity decrease induced by IDN. The interactions between the two drugs suggest that their effects on cerebral hemodynamics (and pain) may be of relevance both in understanding the role of NO in migraine pathogenesis and in evaluating symptomatic treatments for migraine attacks. 相似文献
8.
9.
AE Boothroyd BVS Murthy A Darbyshire AJ Petros 《Acta paediatrica (Oslo, Norway : 1992)》1996,85(12):1422-1425
Objective: Right upper lobe collapse is a common radiographic finding in intubated children. We hypothesized that deep suctioning and uncontrolled negative pressures during endotracheal tube suctioning were significant contributory factors. Methods : The incidence of right upper lobe (RUL) collapse in intubated, ventilated children on a paediatric cardiac intensive care unit was determined over a 3-month period ( n = 102). Graduated suction catheters and suction vacuums of < 165 cm H2 O were then introduced. Another prospective audit was carried out 3 months later ( n = 60). Results : We found that 24% developed RUL collapse and 4 developed an apical pneumothorax. Following the introduction of graduated catheters and controlled vacuums pressures, a significant reduction in the incidence of RUL collapse, to 7%, was observed ( p < 0.05). Conclusions : We conclude that high negative pressure and deep-suctioning causes RUL collapse in children. Any lobar collapse not only prolongs the child's stay in intensive care, but can be associated with further morbidity which may have a serious implication. By improving suctioning technique this morbidity can be significantly reduced. 相似文献
10.
The variability of thoracic impedance cardiogram signals was studied in a normal population with the objective of determining
the effect of different respiratory manoeuvres and the optimal criteria for acquisition of this type of physiological signal.
The variability of the first derivative of the thoracic impedance signal (dZ/dt) was determined at each 5ms intervals along
the signal as the ensemble confidence limits of 3% and 97% around the coherent average. The results obtained indicate that:
(a) signal variability is minimum during respiratory apnea (p<0.05) as compared with apneusis or normal respiration, (b) signal
patterns are different during apnea and apneusis, and (c) during normal respiration the cardiac component of the thoracic
impedance signal can be extracted from the respiratory noise by coherent average yielding a signal with the same pattern obtained
during apnea. 相似文献