全文获取类型
收费全文 | 1172篇 |
免费 | 60篇 |
出版年
2023年 | 6篇 |
2022年 | 6篇 |
2021年 | 29篇 |
2020年 | 15篇 |
2019年 | 21篇 |
2018年 | 24篇 |
2017年 | 32篇 |
2016年 | 36篇 |
2015年 | 48篇 |
2014年 | 60篇 |
2013年 | 76篇 |
2012年 | 97篇 |
2011年 | 94篇 |
2010年 | 60篇 |
2009年 | 63篇 |
2008年 | 72篇 |
2007年 | 74篇 |
2006年 | 71篇 |
2005年 | 51篇 |
2004年 | 60篇 |
2003年 | 51篇 |
2002年 | 51篇 |
2001年 | 7篇 |
2000年 | 10篇 |
1999年 | 12篇 |
1998年 | 7篇 |
1997年 | 10篇 |
1996年 | 12篇 |
1995年 | 7篇 |
1994年 | 10篇 |
1993年 | 6篇 |
1992年 | 7篇 |
1991年 | 4篇 |
1990年 | 4篇 |
1988年 | 3篇 |
1987年 | 3篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1982年 | 5篇 |
1981年 | 2篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1976年 | 3篇 |
1975年 | 2篇 |
1974年 | 3篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1971年 | 2篇 |
1965年 | 1篇 |
排序方式: 共有1232条查询结果,搜索用时 15 毫秒
51.
Heterozygous submicroscopic inversions involving olfactory receptor-gene clusters mediate the recurrent t(4;8)(p16;p23) translocation 下载免费PDF全文
Giglio S Calvari V Gregato G Gimelli G Camanini S Giorda R Ragusa A Guerneri S Selicorni A Stumm M Tonnies H Ventura M Zollino M Neri G Barber J Wieczorek D Rocchi M Zuffardi O 《American journal of human genetics》2002,71(2):276-285
The t(4;8)(p16;p23) translocation, in either the balanced form or the unbalanced form, has been reported several times. Taking into consideration the fact that this translocation may be undetected in routine cytogenetics, we find that it may be the most frequent translocation after t(11q;22q), which is the most common reciprocal translocation in humans. Case subjects with der(4) have the Wolf-Hirschhorn syndrome, whereas case subjects with der(8) show a milder spectrum of dysmorphic features. Two pairs of the many olfactory receptor (OR)-gene clusters are located close to each other, on both 4p16 and 8p23. Previously, we demonstrated that an inversion polymorphism of the OR region at 8p23 plays a crucial role in the generation of chromosomal imbalances through unusual meiotic exchanges. These findings prompted us to investigate whether OR-related inversion polymorphisms at 4p16 and 8p23 might also be involved in the origin of the t(4;8)(p16;p23) translocation. In seven case subjects (five of whom both represented de novo cases and were of maternal origin), including individuals with unbalanced and balanced translocations, we demonstrated that the breakpoints fell within the 4p and 8p OR-gene clusters. FISH experiments with appropriate bacterial-artificial-chromosome probes detected heterozygous submicroscopic inversions of both 4p and 8p regions in all the five mothers of the de novo case subjects. Heterozygous inversions on 4p16 and 8p23 were detected in 12.5% and 26% of control subjects, respectively, whereas 2.5% of them were scored as doubly heterozygous. These novel data emphasize the importance of segmental duplications and large-scale genomic polymorphisms in the evolution and pathology of the human genome. 相似文献
52.
Circulating insulin inhibits endogenous glucose production. Here we report that bidirectional changes in hypothalamic insulin signaling affect glucose production. The infusion of either insulin or a small-molecule insulin mimetic in the third cerebral ventricle suppressed glucose production independent of circulating levels of insulin and of other glucoregulatory hormones. Conversely, central antagonism of insulin signaling impaired the ability of circulating insulin to inhibit glucose production. Finally, third-cerebral-ventricle administration of inhibitors of ATP-sensitive potassium channels, but not of antagonists of the central melanocortin receptors, also blunted the effect of hyperinsulinemia on glucose production. These results reveal a new site of action of insulin on glucose production and suggest that hypothalamic insulin resistance can contribute to hyperglycemia in type 2 diabetes mellitus. 相似文献
53.
Tauroursodeoxycholic acid reduces damaging effects of taurodeoxycholic acid on fundus gastric mucosa
Piepoli AL Caroppo R Armentano R Caruso ML Guerra V Maselli MA 《Archives of physiology and biochemistry》2002,110(3):197-202
We investigated the effects of tauroursodeoxycholic acid (TUDCA) to assess whether this acid may also have "protective" effects similar to those found with ursodeoxycholic acid (UDCA). We used a well-known amphibian model of gastric mucosa, and studied the effects of taurodeoxycholic acid (TDCA) on electrical transepithelial parameters, acid secretion and histology in absence or in presence of TUDCA. Mucosal exposure to TDCA, after stimulation with histamine, caused a reduction in transepithelial potential difference (V(t)) and transepithelial resistance (R(t)) and a decrease in acid secretion while mucosal exposure to TUDCA did not cause a significant change in the electrical parameters. Moreover, TDCA primarily affected the neck cells, while TUDCA affected only oxyntic cells, causing a similar degree of injury to that observed in controls. Mucosal exposure to TUDCA plus TDCA caused a reduction in short circuit current (I(sc)) and R(t), whereas acid secretion did not change. These results suggest that: (1) TUDCA reduces the damaging effects of TDCA on fundus gastric mucosa; (2) TUDCA may play an important role in the treatment of gastritis associated with bile reflux. 相似文献
54.
Cavalcante MC de Andrade LR Du Bocage Santos-Pinto C Straus AH Takahashi HK Allodi S Pavão MS 《Journal of structural biology》2002,137(3):313-321
In most ascidian species the oocytes are surrounded by two types of accessory cells called follicle cells and test cells. Test cells are located on the periphery of oocytes and remain in the perivitelline space during egg development until hatching. Heparin and histamine were previously described in the test cells of the ascidian Styela plicata. In the present study, electron microscopy techniques were used to characterize the ultrastructure of the S. plicata test cells and to localize heparin and histamine in these cells. Test cells contain several intracellular granules with unique ultrastructural features. They are formed by elongated filaments composed of serial globules with an electron-lucent circle, containing a central electron-dense spot. Immunocytochemistry showed that heparin and histamine colocalize at the border of granule filaments in the test cell. Compound 48/80, a potent secretagogue of heparin-containing mast cells, also induced degranulation of test cells. According to these results, we suggest that test cells represent ancient effector cells of the innate immunity in primitive chordates. 相似文献
55.
Salardi S Zucchini S Cicognani A Gualandi S Barbieri E Cacciari E 《Hormone research》2002,57(5-6):205-208
OBJECTIVE/METHODS: To assess exocrine and endocrine testicular function in subjects with diabetes, we evaluated serum inhibin B, gonadotrophins and testosterone levels in 33 male adolescent and young adult patients affected by type-1 diabetes (age 21.0 +/- 5 years; range 14.2-33.3), with a mean disease duration of 12.7 +/- 5.8 years (range 1.5-25.3) and various metabolic control (HbA1c 7.8 +/- 1.5%; range 5.5-13.2) and compared them with those of an age-matched group of 36 healthy control subjects (age 19.5 +/- 4.1 years; range 13.6-28.1). Both patients and controls had a testicular volume >or=15 ml. Inhibin B was measured by ELISA method. RESULTS/CONCLUSION: Diabetics and controls had comparable inhibin B (203 +/- 74 vs. 221 +/- 69 pg/ml, respectively) and follicle-stimulating hormone (FSH) levels, while luteinizing hormone (LH) and testosterone levels were significantly higher in the diabetic group. Inhibin B was negatively correlated both in patients and controls with FSH, while a negative correlation with LH was found only in the diabetic group. We conclude that our young diabetic males, after a mean disease duration of 12 years and various metabolic control, had inhibin B and FSH levels comparable to those of normal subjects. Therefore, they seem to have a regular testicular function and in particular a normal seminiferous tubule/Sertoli cell activity despite sustained hyperglycemia. 相似文献
56.
57.
Enhanced activity of the plasma membrane oxidoreductase in circulating lymphocytes from insulin-dependent diabetes mellitus patients 总被引:2,自引:0,他引:2
Lenaz G Paolucci U Fato R D'Aurelio M Parenti Castelli G Sgarbi G Biagini G Ragni L Salardi S Cacciari E 《Biochemical and biophysical research communications》2002,290(5):1589-1592
Circulating human lymphocytes contain a transmembrane oxidoreductase (PMOR) capable of reducing dichlorophenol indophenol (DCIP) by endogenous reductants, presumably NADH. Membranes from lymphocytes obtained from buffy coats contain a NADH DCIP reductase having a K(m) of about 1 microM and almost insensible to dicoumarol. The PMOR of lymphocytes from insulin-dependent diabetic patients is higher than that from age-matched controls and, in addition, has a dicoumarol-sensitive component, lacking in most controls, presumably due to membrane association of DT-diaphorase. The increase of PMOR in diabetes is likely due to overexpression of the enzyme, in view of the very low K(m) for NADH indicating that, in intact cells, the enzyme is practically saturated with the reductant substrate. 相似文献
58.
This research assessed mother–infant relationships in rhesus and Japanese macaques living in analogous captive social groups,
and monitored changes in the levels of excreted estrogen metabolites during the peripartum period. Each mother–infant pair
was focally observed 3 h per week during the first 12 weeks of life of newborns. Fecal samples were collected twice a week
from each mother, starting 4 weeks before delivery and ending 4 weeks after delivery. Infant-directed behaviors appeared to
be consistently less protective/controlling and more rejecting in rhesus macaques than in Japanese macaques. Estrogen metabolite
levels during the perinatal period were, on average, 3-fold higher in Japanese macaques and showed a sharp increase during
the last weeks of pregnancy only in the Japanese macaque group. Considering the ecological and behavioral similarities between
Japanese and rhesus macaques, the divergence between the two species in the onset and maintenance of maternal behavior was
unexpected. This was possibly linked to the difference in the overall body size and life history, and to the striking divergence
in estrogen metabolite variation during the peripartum period. Group size, social relationships, and average age of individuals
in the two captive groups were not clearly involved in the recorded differences in maternal behavior.
Electronic Publication 相似文献
59.
In this study we report preliminary data on the consumption of tannin-rich plants by sifakas (Propithecus verreauxi verreauxi) living in the Kirindy forest, western Madagascar. Sifakas spent most of their time feeding on only a few plant species.
The tannin intake during the period between the pregnancy and birth season was significantly higher in pregnant females or
females with lactating infants than in non-reproductive females and males. These periparturient females secured a larger proportion
of condensed tannins by short feeding bouts on plants not included in the group's limited preferred food species. The measured
increase in tannin intake is puzzling in light of the fact that tannins are commonly known for their protein-binding properties.
Since protein demands are highest in pregnant and lactating females, possible medicinal benefits of tannin ingestion are considered.
Tannin consumption is associated with an increase in body weight and stimulation of milk secretion. Veterinarians administer
tannins as an astringent, anti-hemorrhagic and anti-abortive. Their high potential as an alternative anthelminthic has also
recently been recognized. Thus, when viewed as self-medicating behavior, controlled increase in tannin intake could have multiple
prophylactic advantages for females during the periparturient period. The high selectivity in their plant choice, and the
presence of unusual feeding habits by a particular group of individuals (females with infants) limited in time (birth season),
suggests that an increase in tannin ingestion may be a self-medicating behavior with multiple directly adaptive benefits to
female reproduction.
Electronic Publication 相似文献
60.
(20S)-[7,7,21,21-2H(4)]-3beta-(tert-Butyldimethylsilanyloxy)-20-methyl-pregn-5-en-21-ol, an intermediate for the preparation of deuterated isotopomers of sterols to be used as standards for biomedical studies, was prepared by reduction with dichloroaluminum deuteride of ethyl (20S)-3beta-(tert-butyldimethylsilanyloxy)-7-oxo-pregn-5-en-20-carboxylate. Using controlled experimental conditions, it has also been shown that the dichloroaluminum hydride reduction of a 7-keto steroid affords the corresponding 7beta-hydroxy derivative in a highly stereoselective manner. 相似文献