全文获取类型
收费全文 | 230391篇 |
免费 | 11295篇 |
国内免费 | 833篇 |
专业分类
耳鼻咽喉 | 3241篇 |
儿科学 | 6821篇 |
妇产科学 | 5758篇 |
基础医学 | 31182篇 |
口腔科学 | 7929篇 |
临床医学 | 15631篇 |
内科学 | 56711篇 |
皮肤病学 | 7054篇 |
神经病学 | 19253篇 |
特种医学 | 5631篇 |
外国民族医学 | 30篇 |
外科学 | 29792篇 |
综合类 | 1180篇 |
一般理论 | 55篇 |
预防医学 | 20327篇 |
眼科学 | 4576篇 |
药学 | 15332篇 |
中国医学 | 927篇 |
肿瘤学 | 11089篇 |
出版年
2023年 | 1313篇 |
2022年 | 1962篇 |
2021年 | 5551篇 |
2020年 | 2945篇 |
2019年 | 5231篇 |
2018年 | 7497篇 |
2017年 | 4693篇 |
2016年 | 4775篇 |
2015年 | 5245篇 |
2014年 | 6943篇 |
2013年 | 9923篇 |
2012年 | 15571篇 |
2011年 | 16205篇 |
2010年 | 8725篇 |
2009年 | 7237篇 |
2008年 | 13362篇 |
2007年 | 14086篇 |
2006年 | 13246篇 |
2005年 | 13186篇 |
2004年 | 11830篇 |
2003年 | 11127篇 |
2002年 | 10426篇 |
2001年 | 6203篇 |
2000年 | 6679篇 |
1999年 | 5425篇 |
1998年 | 1631篇 |
1997年 | 1237篇 |
1996年 | 1121篇 |
1995年 | 1002篇 |
1994年 | 799篇 |
1993年 | 714篇 |
1992年 | 2414篇 |
1991年 | 2174篇 |
1990年 | 1978篇 |
1989年 | 1703篇 |
1988年 | 1500篇 |
1987年 | 1444篇 |
1986年 | 1390篇 |
1985年 | 1257篇 |
1984年 | 953篇 |
1983年 | 814篇 |
1979年 | 827篇 |
1978年 | 585篇 |
1975年 | 629篇 |
1974年 | 704篇 |
1973年 | 753篇 |
1972年 | 636篇 |
1971年 | 637篇 |
1970年 | 613篇 |
1969年 | 605篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
M Munzarová L Lauerová J Kovarík A Rejthar V Brezina R Kellnerová A Kovarík 《Neoplasma》1992,39(2):79-86
Five fusions between mouse embryonic cells and syngeneic adult peritoneal macrophages were performed. The resulting hybrids as well as both parental cells (6 cultures of embryonal cells and 6 cultures of adult macrophages) were grown in vitro under the same culture conditions. All populations of explanted macrophages died during the second month in primary culture and five populations of cultured embryonic cells were lost within six months under in vitro conditions as well. One embryonic cell line survived and acquired transformed and/or malignant phenotype: When inoculated into either newborn or adult syngeneic mice, progressive growth of tumors with 100% take (6/6), histologically classified as poorly differentiated fibrosarcoma with areas of metaplastic bone and osteoid, was observed. Two out of five wild hybrid strains died within six months of cell culture. The resulting three hybrid cultures adapted themselves to in vitro conditions and finally permanent lines were established with all features of transformed phenotype in vitro and with the capacity to grow as undifferentiated fibrosarcomas with 100% take (6/6) when inoculated into syngeneic mice either s.c. or i.p. Cytogenetic studies were performed and phenotypic characteristics of these lines were explored as well. Biological assays performed for the presence of oncogenic viruses were negative and none of the malignant cell lines showed positive staining with the monoclonal antibody specific for large T-antigen. It is suggested that cell fusion of two normal partners may switch on the cascade of abnormal processes which may culminate in neoplastic conversion. Cell fusion might play also a significant role in the so called "spontaneous" transformation. 相似文献
992.
F Martínez Soriano T Hernandez Gil de Tejada C Cimas Garcia E Arma?anzas 《Journal für Hirnforschung》1992,33(3):271-275
A comparative statistical analysis of "synaptic ribbons" evolution over a 24 hour period during two different photoluminous seasons (September, and winter) is carried out. Seventy male rats were used. Statistical analysis involved the Kolmogorov-Smirnov test, variance analysis, the Student t-test and Pearson's correlation test. The results show that "synaptic ribbons" evolve during the circadian phase and through two different seasons, with a clear and marked influence of point-time (p < 0.0001) and season (p < 0.0001). 相似文献
993.
Blood rheological properties were studied in 21 patients suffering from essential hypertension (EHT), degree I-II according to WHO criteria. These patients were diagnosed "de novo". The whole blood filterability (WBF), blood viscosity (BV) at 230 s-1 and 23 s-1, red cell deformability (FI), erythrocyte aggregation in autologous (MEA) and normal plasma (MEAc), fibrinogen (Fbg) and hematocrit (Ht) have been evaluated. In the hypertensive patients we have found decreased WBF, greater BV and FI in comparison with the control group (p less than 0.001). Likewise, MEA and Fbg were increased, though the differences were less significant (p less than 0.01). The evaluation of Ht did not show any differences between the two groups. The results suggest that in the newly diagnosed EHT, clear hemorheological alterations occur, both in plasma and in the erythrocytes, which could play a role in the pathogenesis of the aforementioned disease. 相似文献
994.
We recorded topographic mapping of auditory evoked potentials (AEPs) to homogeneous series of tones delivered in the absence of any cognitive task ("neutral condition") and compared them with responses to identical stimuli when they acted as non-targets in an oddball paradigm. With respect to the neutral condition, non-target responses showed an increase in N100 amplitude which was found to depend on two different, but partially overlapping effects. The "early effect" had similar latency and topography as exogenous N100 and may reflect changes in the overall state of alertness since its amplitude declined at the end of the test. The "late effect" affected the N100s descending slope and had features consistent with those of a processing negativity. It was frontally distributed, and topographic mapping revealed a right-sided predominance. Finally, non-target responses exhibited a central positivity (P250) which did not appear in neutral AEPs. P250 shares several features, including latency, amplitude and scalp topography, with the endogenous ERP component commonly labelled "P3a". Non-target P250 could be the result of an attentional shift towards the stimuli, and reflect some aspects of the classification process. We suggest that non-target responses in simple oddball paradigms should be routinely studied along with target responses in order to improve the diagnostic capabilities of cognitive ERPs. Notably, non-target responses may help to decide whether an abnormal target-P300 is related or not to a deficit in the mobilization of attentional resources. 相似文献
995.
J M Tejerina Lobo J V Bagan Sebastián J Ramón Mu?iz 《Avances en Odontoestomatología》1989,5(5):263-267
Infection of the oral mucous membrane is frequent in patients with removable prostheses, either totally of partially, and particularly when the prostheses is palatal. The principal etiological factor causing the infection is accepted to be "Candidas" aided by the presence of plaque bacteria (in patients with poor oral hygiene care), and a poor fit of the prostheses to the soft tissues. Treatment of the infection must proceed in the following order: a) use of effective medication against oral fungus such as Nystatin or Ketoconazole. b) Meticulous oral hygiene care in the mucous membrane as well as in the prostheses, but using the prostheses as little as possible during the treatment period. c) A total cure of the infection (denture stomatitis) before proceeding to the next phase of the treatment. d) Determination of the adjustment and occlusion of the prostheses in order to determine those areas of the prostheses which need to be refilled because of maladjustment of the prostheses to the soft tissues of the patient. 相似文献
996.
Among 389 consecutive chronic alcoholics in whom a liver biopsy was performed for diagnostic purposes, nine patients (2.3%) had histological changes of "alcoholic foamy degeneration" (AFD), characterized by numerous small fat droplets in the swollen hepatocytes of the centrilobular area. In five cases, there were non-specific clinical features, while the other four cases presented acute hepatic decompensation with jaundice and a reduced prothrombin activity. Seven patients had high serum lipid concentrations including hypertriglyceridemia and hypercholesterolemia, which improved after withdrawal of alcohol intake. In conclusion, AFD has a broad clinicopathological spectrum including asymptomatic patients and other cases with severe liver decompensation manifested by jaundice and reduced prothrombin activity. AFD is usually associated with hyperlipemia. 相似文献
997.
The authors compared the results of six-week treatment in a therapeutic community comprising 484 patients who had therapy in groups which were classified as "good" by their therapists, and 91 patients having therapy in groups, classified by the therapists as "poor". No significant difference was found in the two groups as regards mitigation of symptoms, insight, change of attitudes and behavior at the time of completion of treatment and after an interval of one year. Effective factors of group psychotherapy obviously are equally effective also in groups with which the therapists are not satisfied. 相似文献
998.
M F López-Fernández C López-Berges J Fermoso A Martín-Pascual J J Sánchez-Hernández A López-Borrasca J Batlle 《Thrombosis and haemostasis》1989,62(2):690-693
Factor VIII and von Willebrand factor proteins were evaluated in 115 patients having the chronic phase of the Toxic Epidemic Syndrome (TES), a new multisystemic disease probably caused by the ingestion of denatured rapeseed oil, and in 50 control volunteers. Higher circulating levels of factor VIII procoagulant activity (VIII:C) (158 +/- 58.4 U/dl), von Willebrand factor antigen (vWF:Ag) (166.1 +/- 55.5 U/dl) and von Willebrand factor ristocetin cofactor activity (vWF:RCo) (178.7 +/- 55.2 U/dl) were seen in TES patients (p less than 0.001, TES patients versus control subjects, for each parameter). The increased levels of vWF:Ag and vWF:RCo observed in TES patients correlated with the scleroderma like lesion of the skin, with the sicca syndrome and with Raynaud's phenomenon (p less than 0.01), but not with other clinical manifestations. The multimeric analysis of vWF in 92% of the TES patients was similar to that found in normal plasma, but in the remaining 8% a very slight increase of larger vWF multimers in plasma were observed. The raised levels of vWF found in TES patients in the chronic phase may reflect an "in vivo" vascular injury. 相似文献
999.
Manuel Castro-Gago Inés Novo Rodriguez Antonio Rodriguez-Núñez José Peña Guitián Santiago Lojo Rocamonde Santiago Rodriguez-Segade 《Child's nervous system》1989,5(6):361-363
The xanthine, hypoxanthine, and total oxypurine levels were determined in the CSF of 28 hydrocephalic patients (age from newborn to 2 years) and 8 healthy controls using HPLC. The Evans' index, the mean weekly increase in cranial circumference, and the intracranial pressure were also measured. Of the hydrocephalic patients 13 were self-compensated and the other 15 had a shunt implanted during the course of the study. The mean xanthine, hypoxanthine, and total oxypurine levels in the normal children were 5.20, 5.94, and 11.29 mol/l, respectively. In the self-compensated hydrocephalics these levels were 5.17, 5.71, and 10.79 mol/l, respectively. In the noncompensated hydrocephalics, they were 9.90, 9.91, and 19.82 mol/l. The differences between the latter group and the first two are statistically significant (P<0.001). The mean Evans' index and the mean weakly increase in cranial circumference in the self-compensated hydrocephalics were 0.35 and 0.25 cm, respectively. In the noncompensated hydrocephalics, they were 0.55 and 0.95 cm. The differences between the two groups are statistically significant (P<0.001). Two weeks after implantation of shunts in the noncompensated cases, the mean xanthine, hypoxanthine, and total oxypurine levels fell to 4.22, 4.57, and 8.80 mol/l, respectively. These changes are statistically significant (P<0.001). We think that the two criteria (clinical and biochemical) are equally useful for the prediction of self-compensation in hydrocephalic children and that the oxypurine values after shunt implantation can be used to monitor progress in noncompensated cases. 相似文献
1000.
Hippocampal extracellular levels of noradrenaline (NA), 5-hydroxytryptamine (5-HT), and 5-hydroxyindoleacetic acid (5-HIAA) were monitored with the microdialysis technique in freely moving rats. In one experiment 30 min samples were collected during 24 h of continuous perfusion, and the monoamine output was compared to the behavioural activity state, as arbitrarily classified in three categories: sleep/rest, drowsiness and full alertness associated with complex behaviours. In the individual animal the hippocampal NA and 5-HT output showed pronounced fluctuations during the 24 h period, but the 30 min sampling times did not allow for a clear-cut correlation to behavioural activity state. However, the mean NA and 5-HT output for all animals during the dark period of the day was 43 and 38% higher, respectively, than during the light period, and the average NA and 5-HT levels in samples collected during periods of high behavioural activity was 34 and 45% higher, respectively, than during periods of rest or sleep. In contrast, there were no detectable changes in extracellular 5-HIAA. The selective serotonin uptake blocker indalpine, added to the perfusion fluid at 1 microM, increased the extracellular 5-HT levels 6-fold, with a similar correlation to behavioural activity state as without indalpine. In a second experiment the effect of handling and tail-pinch was studied in 15 min sample fractions. Gentle handling of the animals during the sampling period increased the hippocampal NA and 5-HT output by 32 and 72%, respectively, and a similar increase (63 and 48%) was obtained by application of tail-pinch. Maximum NA output was reached during the handling or tail-pinch period, whereas maximal 5-HT levels were detected in the subsequent 15 min sample fraction. No changes in extracellular 5-HIAA was observed. It is concluded (1) that intracerebral microdialysis provides a useful method for the study of extracellular NA and 5-HT in the hippocampal formation of conscious rats during active behaviour; (2) that there are substantial fluctuations in hippocampal NA and 5-HT output in freely moving rats which correlate with the light - dark cycle as well as with the activity state of the animals; (3) that the spontaneous variations in 5-HT output are maintained during reuptake blockade; and (4) that behavioural activation through gentle handling or tail-pinch elicits NA and 5-HT release. The present data support a role of the forebrain NA and 5-HT systems in behavioural state control and highlights the necessity of experimental designs in which the spontaneous fluctuations in transmitter release are controlled for in studies of, for example, drug effects on NA and 5-HT release in conscious animals. 相似文献