全文获取类型
收费全文 | 777582篇 |
免费 | 87434篇 |
国内免费 | 442篇 |
专业分类
865458篇 |
出版年
2018年 | 7254篇 |
2017年 | 6993篇 |
2016年 | 9679篇 |
2015年 | 12625篇 |
2014年 | 15094篇 |
2013年 | 21928篇 |
2012年 | 24224篇 |
2011年 | 24766篇 |
2010年 | 16660篇 |
2009年 | 15243篇 |
2008年 | 21664篇 |
2007年 | 22580篇 |
2006年 | 21036篇 |
2005年 | 20351篇 |
2004年 | 20239篇 |
2003年 | 19424篇 |
2002年 | 18885篇 |
2001年 | 37677篇 |
2000年 | 37601篇 |
1999年 | 29681篇 |
1998年 | 9726篇 |
1997年 | 10315篇 |
1996年 | 9665篇 |
1995年 | 9047篇 |
1994年 | 8826篇 |
1993年 | 8767篇 |
1992年 | 24094篇 |
1991年 | 23093篇 |
1990年 | 22444篇 |
1989年 | 21893篇 |
1988年 | 20266篇 |
1987年 | 19000篇 |
1986年 | 17660篇 |
1985年 | 17416篇 |
1984年 | 14359篇 |
1983年 | 12291篇 |
1982年 | 9348篇 |
1981年 | 8373篇 |
1980年 | 7953篇 |
1979年 | 13783篇 |
1978年 | 10506篇 |
1977年 | 9773篇 |
1976年 | 8959篇 |
1975年 | 9819篇 |
1974年 | 10599篇 |
1973年 | 10477篇 |
1972年 | 9626篇 |
1971年 | 8815篇 |
1970年 | 7539篇 |
1969年 | 7243篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
992.
S Glazer M M Vartanova N N Konstantinova 《Biulleten' eksperimental'no? biologii i meditsiny》1985,100(10):414-415
Significant adverse correlation of the fetus mass and the degree of its hydration was noted at term in rats with placental insufficiency induced by ligation of about 40% of preplacental vessels on the 16th day of gestation. Disorders revealed in transplacental water-salt metabolism are apparently of some importance for the pathogenesis of fetal growth retardation. Even moderate retardation alters fetal respiratory activity in anoxia, which is associated with the changes in the function of respiratory centres and neuromuscular abnormalities. 相似文献
993.
The authors analyze the results of comparative studies on 15 paired sera from children with suspected measles, of 32 sera from children and adolescents aged 1.5 to 16 immunized against measles, and of 21 sera from adults aged 19 to 86 with a history of the disease. EIA proved to be more sensitive than HAIT: the detection rate of positive sera was higher, as were the titers of antibodies detected by it, in examinations of the sera from vaccinated children and the adults. Analysis of the distribution of sera with different titers of antibody to measles virus in EIA and HAIT has revealed a correlation between the titers in the sera with high antibody levels. In the cases with low antihemagglutinin titers, no correlation between the titers determined in the two tests has been observed. 相似文献
994.
S Imajoh H Kawasaki Y Emori K Suzuki 《Biochemical and biophysical research communications》1987,146(2):630-637
Endogenous inhibitors for calcium-activated neutral protease (CANP) were purified from rabbit erythrocytes and liver. The purified inhibitors showed single bands but with significantly different mobilities on sodium dodecylsulfate-polyacrylamide gel electrophoresis. Peptide mapping and sequencing analyses have revealed that the erythrocyte inhibitor (429 residues) retains the C-terminal three repetitive units of the liver inhibitor (639 residues), which contains four potential repetitive units for inhibition of CANP. The erythrocyte and liver inhibitors inhibited 3 and 4 moles of CANP on the basis of the molecular weights of 46,000 and 68,000, respectively. 相似文献
995.
Glycogen debranching enzyme: purification, antibody characterization, and immunoblot analyses of type III glycogen storage disease. 总被引:2,自引:1,他引:1 下载免费PDF全文
Type III glycogen storage disease is caused by a deficiency of glycogen debranching-enzyme activity. Many patients with this disease have both liver and muscle involvement, whereas others have only liver involvement without clinical or laboratory evidence of myopathy. To improve our understanding of the molecular basis of the disease, debranching enzyme was purified 238-fold from porcine skeletal muscle. In sodium dodecyl sulfate-polyacrylamide gel electrophoresis the purified enzyme gave a single band with a relative molecular weight of 160,000 that migrated to the same position as purified rabbit-muscle debranching enzyme. Antiserum against porcine debranching enzyme was prepared in rabbit. The antiserum reacted against porcine debranching enzyme with a single precipitin line and demonstrated a reaction having complete identity to those of both the enzyme present in crude muscle and the enzyme present in liver extracts. Incubation of antiserum with purified porcine debranching enzyme inhibited almost all enzyme activity, whereas such treatment with preimmune serum had little effect. The antiserum also inhibited debranching-enzyme activity in crude liver extracts from both pigs and humans to the same extent as was observed in muscle. Immunoblot analysis probed with anti-porcine-muscle debranching-enzyme antiserum showed that the antiserum can detect debranching enzyme in both human muscle and human liver. The bands detected in human samples by the antiserum were the same size as the one detected in porcine muscle. Five patients with Type III and six patients with other types of glycogen storage disease were subjected to immunoblot analysis. Although anti-porcine antiserum detected specific bands in all liver and muscle samples from patients with other types of glycogen storage disease (Types I, II, and IX), the antiserum detected no cross-reactive material in any of the liver or muscle samples from patients with Type III glycogen storage disease. These data indicate (1) immunochemical similarity of debranching enzyme in liver and muscle and (2) that deficiency of debranching-enzyme activity in Type III glycogen storage disease is due to absence of debrancher protein in the patients that we studied. 相似文献
996.
997.
The main condition of completing the process of adaptation of the body to the effect of an external factor is the return of the homeostatic system parameters to their initial levels or their stabilization at a new level. The article considers the state of incomplete adaptation (IA) based on the process of the stabilization of systemic reactions (respiration and blood circulation) on repeated exposure to extreme environmental factors (hypoxia and cold) associated with the excitation of the central regulatory mechanisms of the respiratory center system performing a compensatory–protective function. It is postulated that a change in the afferent information flows (the thresholds of excitation and reactivity of the peripheral receptor systems) forms the basis of IA. The IA state is supposed to persist for an indefinitely long period of time due to insufficient functional reserves and to be the cause of psychosomatic pathology. 相似文献
998.
Obesity-inducing lesions of the central nervous system alter leptin uptake by the blood-brain barrier. 总被引:1,自引:0,他引:1
Leptin regulates body adiposity by decreasing feeding and increasing thermogenesis. Obese humans and some obese rodents are resistant to peripherally administered leptin, suggesting a defect in the transport of leptin across the blood-brain barrier (BBB). Defective transport of exogenous leptin occurs in some models of obesity, but in other models transport is normal. This shows that factors other than obesity are associated with impairment of leptin transport across the BBB. In order to further investigate these factors, we determined leptin transport in rats made obese by lesioning of the ventromedial hypothalamus (VMH), paraventricular nucleus (PVN), or posterodorsal amygdala (PDA). These regions all contain leptin receptors and lesions there induce obesity and hyperleptinemia and alter the levels of many feeding hormones which might participate in leptin transporter regulation. We measured the uptake of radioactively labeled leptin by the BBB by multiple-time regression analysis which divides uptake into a reversible phase (Vi, e.g., receptor/transporter binding to the brain endothelial cell) and an irreversible phase (Ki, complete transport across the BBB). Leptin uptake was not affected in rats with VMH lesions. No significant change occurred in the entry rate (Ki) for any group, although Ki declined by over 35% in rats with PVN lesions. Decreased uptake was observed in rats with PVN lesions and with PDA lesions. This was primarily due to a reduced Vi (about 21% for the PDA). This decreased uptake is most likely explained by decreased binding of leptin to the brain endothelial cell, which could be because of decreased binding by either receptors or transporters. This suggests that some of the feeding hormones controlled by the PVN and PDA may participate in regulating leptin uptake by the BBB. 相似文献
999.
1000.
F. Marsolat D. Tromson N. Tranchant P. Bergonzo F. Moignau L. De Carlan D. Lazaro M. Agelou C. Bassinet C. Huet S. Derreumaux M. Chea G. Boisserie I. Buchheit V. Marchesi 《Physica medica : PM : an international journal devoted to the applications of physics to medicine and biology : official journal of the Italian Association of Biomedical Physics (AIFB)》2012