全文获取类型
收费全文 | 3643篇 |
免费 | 104篇 |
国内免费 | 51篇 |
专业分类
耳鼻咽喉 | 26篇 |
儿科学 | 61篇 |
妇产科学 | 49篇 |
基础医学 | 510篇 |
口腔科学 | 47篇 |
临床医学 | 229篇 |
内科学 | 535篇 |
皮肤病学 | 72篇 |
神经病学 | 363篇 |
特种医学 | 97篇 |
外科学 | 414篇 |
综合类 | 205篇 |
预防医学 | 199篇 |
眼科学 | 73篇 |
药学 | 581篇 |
中国医学 | 87篇 |
肿瘤学 | 250篇 |
出版年
2023年 | 89篇 |
2022年 | 88篇 |
2021年 | 91篇 |
2020年 | 99篇 |
2019年 | 230篇 |
2018年 | 248篇 |
2017年 | 154篇 |
2016年 | 52篇 |
2015年 | 50篇 |
2014年 | 149篇 |
2013年 | 152篇 |
2012年 | 106篇 |
2011年 | 95篇 |
2010年 | 69篇 |
2009年 | 49篇 |
2008年 | 47篇 |
2007年 | 51篇 |
2006年 | 48篇 |
2005年 | 123篇 |
2004年 | 117篇 |
2003年 | 115篇 |
2002年 | 65篇 |
2001年 | 62篇 |
2000年 | 38篇 |
1999年 | 40篇 |
1997年 | 28篇 |
1996年 | 34篇 |
1995年 | 65篇 |
1994年 | 54篇 |
1993年 | 74篇 |
1992年 | 56篇 |
1991年 | 47篇 |
1990年 | 33篇 |
1989年 | 50篇 |
1988年 | 40篇 |
1987年 | 31篇 |
1986年 | 33篇 |
1985年 | 69篇 |
1984年 | 83篇 |
1983年 | 41篇 |
1982年 | 89篇 |
1981年 | 54篇 |
1980年 | 65篇 |
1979年 | 59篇 |
1978年 | 65篇 |
1977年 | 35篇 |
1976年 | 50篇 |
1975年 | 59篇 |
1974年 | 51篇 |
1973年 | 54篇 |
排序方式: 共有3798条查询结果,搜索用时 31 毫秒
101.
Clemens Allgaier Ernst Agneter Thomas J. Feuerstein Ernst A. Singer 《Naunyn-Schmiedeberg's archives of pharmacology》1992,345(4):402-409
Summary The aim of the present study was to determine the local concentrations of noradrenaline existing at presynaptic 2-adrenoceptors during electrical pulse train stimulation of brain slices at different frequencies. The experiments are based on the assumption that the concentration of released noradrenaline at the 2-adrenoceptors exerting a certain autoinhibition should be equal to the concentration of exogenous noradrenaline causing the same inhibition under conditions in which any influence of the released transmitter is excluded. In order to avoid autoinhibition, hippocampus and cortex slices of the rabbit and the rat, prelabelled with [3H]noradrenaline and superfused in presence of an uptake inhibitor, were electrically stimulated using 4 pulses delivered at 100 Hz (POP stimulation). Exogenous noradrenaline diminished the overflow of tritium elicited by POP stimulation in a concentration-dependent manner. In rabbit brain tissues the EC50 value and maximum inhibition of noradrenaline release were found to be approximately 6 nmol/l and more than 95%, respectively, whereas in rat tissues the corresponding values were between 20 and 30 nmol/l and approximately 90%. When electrical stimulation was performed with trains of 36 pulses delivered at 0.1, 0.3 or 3 Hz in absence or presence of an uptake inhibitor, the 2-adrenoceptor antagonist yohimbine (1 or 10 mol/l) enhanced the evoked tritium overflow in a manner which was dependent on the frequency of stimulation and on blockade of the re-uptake mechanism. The facilitatory effects of yohimbine reflected an extent of autoinhibition which was between 53% (36 pulses/0.1 Hz, no uptake inhibitor) and 85% (36 pulses/3 Hz, uptake inhibitor present) in rabbit and between 16% (36 pulses/0.3 Hz, no uptake inhibitor) and 71% (36 pulses/3 Hz, uptake inhibitor present) in rat brain slices. Accordingly, the corresponding estimated biophase concentrations of noradrenaline were generally higher in rat than in rabbit tissues (they were between 32.5 and 74.5 or 5.1 and 51.6 nmol/l in the presence or absence of an uptake inhibitor, respectively, in the rat, and between 15 and 23.1 or 6.1 and 18.6 nmol/l in the rabbit). The observed frequency dependence of the effect of re-uptake blockade on the calculated biophase concentrations of noradrenaline would be compatible with the idea of a dependence of the effectiveness of the re-uptake mechanism on the firing rate of the neurone in being more effective at lower frequencies. Moreover, the stikingly low biophase concentrations of noradrenaline suggest that also in brain tissue noradrenaline causes lateral inhibition of release as has recently been shown for guinea-pig vas deferens.
Send offprint requests to C. Allgaier at the above address 相似文献
102.
The nucleotide sequence of the gene coding for the plastid-encoded subunit of DNA-dependent RNA polymerase from the cryptomonad alga Pyrenomonas salina was determined. The deduced amino-acid sequence, corresponding to a 35.2 kDa polypeptide, was compared to homologues from other organisms. Evolutionary relationships were analyzed in detail by the parsimony method together with bootstrap analysis. The deduced phylogenetic tree shows that the cryptomonad gene is the most ancient type of known plastid-encoded RNA polymerase. 相似文献
103.
Yu. S. Massino E. A. Kizim A. D. Dmitriev 《Bulletin of experimental biology and medicine》1991,112(5):1618-1622
Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR, Moscow. (Presented by Academician of the Academy of Medical Sciences of the USSR E. A. Zotikov.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 112, No. 11, pp. 511–514, November, 1991. 相似文献
104.
A. S. Simbirtsev V. G. Konusova S. A. Ketlinskii 《Bulletin of experimental biology and medicine》1991,112(3):1288-1291
All-Union Research Institute of Highly Pure Biological Preparations, Leningrad. (Presented by Academician of the Academy of Medical Sciences of the USSR V. D. Belyakov). Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 112, No. 9, pp. 278–280, September, 1991. 相似文献
105.
Carlo Orzincolo M.D. Pier Nuccio Scutellari M.D. Giuseppe Castaldi M.D. 《Skeletal radiology》1992,21(1):39-44
In 12 patients affected by thalassemia major who received an intensive transfusion regimen combined with continuous iron chelation therapy (desferrioxamine 50–80 mg/kg daily), radiologic abnormalities of the long bones were observed similar to those observed in rickets and scurvy. These abnormalities were associated with a growth retardation. The pathogenesis of these lesions is uncertain, but probably the toxic effect of desferrioxamine plays an important role in their development. A relative deficiency of vitamins D and/or C cannot be entirely excluded. 相似文献
106.
Thierry Humbert Cuong Luu-Duc Michel Comet Pierre Demenge 《European journal of nuclear medicine and molecular imaging》1991,18(11):870-878
Previous studies led us to hypothesize that a fatty acid analogue, 15-p-iodophenyl--methyl pentadecanoic acid (IMPPA or BMIPP), which is taken up but not quickly metabolized by heart cells, would be a more suitable tracer of cellular viability than thallium-201. Biodistribution studies of 1-14C-IMPPA in conscious, freely moving rats showed that the concentration ratio of radioactivity in the heart with respect to the blood was about 8 for at least 60 min after intravenous administration, permitting its use as a putative tracer in these conscious, freely moving rats. Thereafter, the myocardial uptake of14C-IMPPA was studied in isoproterenol-treated rats (daily treatment for 10 days in order to induce cardiac hypertrophy and necrotic foci) with respect to control ones. Comparison of myocardial localizations by quantitative autoradiography of the uptake of201Tl and14C-IMPPA with that of triphenyltetrazolium chloride (TTC) staining enabled comparative evaluation of nutritional blood flow, localization and uptake of14C-IMPPA and necrotic foci size. Distributions of14C-IMPPA and2011 T1 in control rats' hearts were homogeneous, like TTC staining. In infarcted hearts, areas of decreased14C-IMPPA uptake were nearly the same (100%±5%) as those unstained by TTC. These areas were larger than those showing a decrease in thallium uptake (about 70%±5% of the total scar size). Therefore, IMPPA seems to be a more accurate and sensitive indicator of necrosis localization compared with thallium. It may be a useful agent for assessment of myocardial viability by single photon emission tomography (SPET) imaging. 相似文献
107.
T. Ohgami T. Kitamoto R. W. Shin Y. Kaneko K. Ogomori J. Tateishi 《Acta neuropathologica》1991,81(3):242-247
Summary To clarify the association of microglia with senile plaques, the brains from 13 patients with Alzheimer's disease (AD) and 23 nondemented aged controls were investigated immunohistochemically by a double-labeling method using anti--protein antiserum and anti-ferritin antibody, which is a recently reported microglia marker. In addition, a quantitative analysis was performed. The senile plaques which appeared initially in the nondemented aged controls consisted of a diffuse type without any amyloid cores and these were found in the group aged 50–59 years. The great majority of them were found to contain no ferritin-positive microglia. The number and proportion (percentage) of microglia-containing diffuse plaques increased with age. Classical and compact plaques began to appear in the brains of the group aged 70 years and over, and practically all of them contained microglia. These results suggest that microglia are not associated with initial plaque formation, but correlate with amyloid core formation. In AD, the most prominent feature was that the diffuse plaques, which contained either no or only a few ferritin-positive microglia, increased markedly.Supported in part by a Grant-in-Aid for Scientific Research from the Ministry of Education, Science and Culture of Japan 相似文献
108.
Summary The blood chemistry and clinical pharmacokinetics of thioridazine and its metabolites, side-chain sulphoxide, side-chain sulphone and ring sulphoxide, were studied in 31 alcoholics and were compared with values in 17 thioridazine-treated controls without alcoholism. Pathological blood chemistry values, including abnormal liver function and protein concentrations, were common among the alcoholics. In relation to dosage, the majority had a low serum concentration of thioridazine and at a given concentration of thioridazine they had high serum concentrations of its metabolites. Positive intercorrelations were found between pathological liver function tests, prolonged serum half-life and increased serum concentration of thioridazine. The free fractions of thioridazine, side-chain sulphoxide and ring sulphoxide were significantly higher and those of the side-chain sulphone lower in the alcoholics than in the controls. The free fractions of side-chain and ring sulphoxide were significantly increased in patients with a low concentration of 1-acid glycoprotein. 相似文献
109.
Jan-Erik Lindgren Agneta Ohlsson Stig Agurell Leo Hollister Hamp Gillespie 《Psychopharmacology》1981,74(3):208-212
9-Tetrahydrocannabinol (9-THC) was administered in a crossover design by smoking and IV injection to groups of heavy and light users of marihuana. Plasma concentrations of 9-THC were similar for the groups after IV injection of 5.0 mg 9-THC, but the AUC0–240 min showed a trend towards lower values for the heavy user group. To achieve a maximum desired high, both groups smoked similar amounts (about 13 mg) of 9-THC. Heavy users tended to have higher plasma levels than light users. The systemic availability of smoked 9-THC was significantly higher for the heavy users (heavy users 23±16% vs 10±7% for light users). These results also indicate that heavy cannabis users smoke more efficiently than casual smokers.Both light and heavy users showed more clinical effect following IV administration than after smoking. The response of the heavy users, both with respect to effect on heart and high, was quite comparable to that of light users.The present study does not suggest that tolerance readily develops in heavy users. 相似文献
110.
G. H. Willital C. Krebs und H. Meier 《Langenbeck's archives of surgery / Deutsche Gesellschaft fur Chirurgie》1979,349(1):535
Zusammenfassung In 10 Jahren werden 130 Kinder wegen eines Dunndarmileus operiert. In 45 Fallen war die Ursache des Dunndarmileus eine vorausgegangene Laparotomie. Bei 13 dieser 45 Relaparotomien mußte erneut eine Laparotomie durchgeführt werden. In 40 % der Relaparotomiefälle war ein durchblutungsgestörter Darm die Ursache dafür. Funktions- and durchblutungsgestörte, dilatierte, hypertrophierte and atonische Darmanteile, die für die normale Peristaltik ungeeignet sind, sollen durch eine erweiterte Resektion des Dünndarms reseziert werden (Anastomose vitaler Diinndarmabschnitte). 相似文献