全文获取类型
收费全文 | 802篇 |
免费 | 66篇 |
出版年
2023年 | 3篇 |
2022年 | 10篇 |
2021年 | 12篇 |
2020年 | 12篇 |
2019年 | 11篇 |
2018年 | 17篇 |
2017年 | 21篇 |
2016年 | 31篇 |
2015年 | 23篇 |
2014年 | 39篇 |
2013年 | 55篇 |
2012年 | 63篇 |
2011年 | 54篇 |
2010年 | 21篇 |
2009年 | 30篇 |
2008年 | 46篇 |
2007年 | 64篇 |
2006年 | 60篇 |
2005年 | 44篇 |
2004年 | 56篇 |
2003年 | 40篇 |
2002年 | 31篇 |
2001年 | 8篇 |
2000年 | 15篇 |
1999年 | 10篇 |
1998年 | 12篇 |
1997年 | 2篇 |
1996年 | 4篇 |
1995年 | 8篇 |
1994年 | 6篇 |
1993年 | 3篇 |
1992年 | 6篇 |
1991年 | 4篇 |
1990年 | 6篇 |
1989年 | 4篇 |
1988年 | 2篇 |
1987年 | 4篇 |
1986年 | 2篇 |
1985年 | 5篇 |
1983年 | 4篇 |
1982年 | 3篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1971年 | 1篇 |
1962年 | 1篇 |
1916年 | 1篇 |
排序方式: 共有868条查询结果,搜索用时 31 毫秒
101.
Kolankaya D Sentürk H Tüylü AO Hayretdağ S Selmanoğlu G Sorkun K 《Zeitschrift für Naturforschung. C, Journal of biosciences》2006,61(5-6):421-426
Three kinds of pollen taxa belonging to 3 families (Fabaceae--Trifolium spp., Brassicaceae--Raphanus spp. and Cistaceae--Cistus spp.) and commonly collected by honeybees were fed to mature male rats separately, in the form of 60 mg/animal/day for a 30-day period. The objective of this study was to investigate any positive effects or possible side effects of the use of pollen on the immune system. This was achieved through blood analysis and cell count on blood, hemoglobin, erythrocyte and immune system cells. The cell concentration of mast cells, degranulization and cell localization were investigated in prepared mesentery tissue samples. Histological investigations of the stomach and duedenum sections of pollen-fed rats were carried out to learn the reason for eosinophil gastroenteritis in the alimentary canal. The eosinophil and lymphocyte levels of rats fed with pollen of Trifolium spp., Raphanus spp., and Cistus spp. were observed to have increased blood cell counts, while neutrophil and monocyte levels decreased; different values were found in basophil leucocytes between the pollen groups. Differing reductions in mesentery mast cell concentration, degranulization and cell localization were found. Within the three separate pollens, the rats having been fed with Cistus spp. pollen were observed to have higher blood lymphocyte, eosinophil, hemoglobin and hematocrit values than those fed with the others, as well as low mesentery mast cell concentration. Hemoglobin values were determined to increase at a proportion of between 10.0-11.3%. No difference was found in other blood parameters. The fat proportion of the male rats fed with the three taxa was between 4.03-8.75%, while that for protein proportion was between 16.11-24.25%. Male rats receiving these taxa did not experience allergic reactions and it is possible to argue that the low protein and fat content of these pollens have a strengthening effect on the immune systems by the increase in lymphocyte content and the amount of hemoglobin leads to an increase of oxygen transport capacity in the tissues. 相似文献
102.
Tang Y Akbulut H Maynard J Petersen L Fang X Zhang WW Xia X Koziol J Linton PJ Deisseroth A 《Journal of immunology (Baltimore, Md. : 1950)》2006,177(8):5697-5707
We showed that the Ad-sig-TAA/ecdCD40L vaccine induces a tumor suppressive immune response to the hMUC-1 and rH2N tumor-associated self Ags (TAA) and to the Annexin A1 tumor vascular Ag, even in mice in which anergy exists to these Ags. When the TAA/ecdCD40L protein is given s.c. as a boost following the Ad-sig-TAA/ecdCD40L vector, the levels of the TAA-specific CD8 T cells and Abs increase dramatically over that seen with vector alone, in young (2-mo-old) as well as old (18-mo-old) mice. The Abs induced against hMUC-1 react with human breast cancer. This vaccine also induces a 4-fold decrement of negative regulatory CD4CD25FOXP3-T cells in the tumor tissue of 18-mo-old mice. These results suggest that the Ad-sig-TAA/ecdCD40L vector prime-TAA/ecdCD40L protein boost vaccine platform may be valuable in reducing postsurgery recurrence in a variety of epithelial neoplasms. 相似文献
103.
Bolscher JG van der Kraan MI Nazmi K Kalay H Grün CH Van't Hof W Veerman EC Nieuw Amerongen AV 《Peptides》2006,27(1):1-9
Antimicrobial peptides have been found throughout living nature, yet antimicrobial sequences may still lie hidden within a wide variety of proteins. A rational strategy was developed to select interesting domains, based on the presumed common features of antimicrobial peptides, and to release these from accessible and safe proteins. In silico proteolysis simulations of bovine lactoferrin (bLF) with selected endoproteinases predicted the liberation of peptides that encompasses a cationic amphipathic alpha-helix. Three predicted peptides were synthesized and tested for their biological activity, demonstrating that one single enzyme was sufficient to obtain an antimicrobial peptide. The proof of principle demonstrated that a 32-mer fragment isolated from the endoproteinase AspN digestion of bLF possessed strong antimicrobial activity. Moreover, desalted crude digest had improved activity over native bLF. Hence, selective digestion of bLF increases its antimicrobial activity by release of antimicrobial stretches. 相似文献
104.
Protective effects of caffeic acid phenethyl ester (CAPE) on amikacin-induced nephrotoxicity in rats
Parlakpinar H Ozer MK Ucar M Gaffaroglu M Vardi N Koc M Acet A 《Cell biochemistry and function》2006,24(4):363-367
Amikacin (AK) has nephrotoxic side effects. AK-induced nephrotoxicity may be the consequence of oxidative stress and so anti-oxidant agents could be useful in reducing AK toxicity. Caffeic acid phenethyl ester (CAPE) was recently shown to have free radical scavenging ability and it reduces lipid peroxidation. For this purpose, the rats were distributed into three groups: (I) injected with vehicle (control); (II) injected (i.p.) with 1.2 g kg(-1) AK at a single dose; (III) injected (i.p.) with AK plus 10 micromol kg(-1) CAPE. Renal morphology was investigated by light microscopy. Tissue samples and trunk blood were also obtained to determine renal malondialdehyde (MDA), blood urea nitrogen (BUN) and creatinine (Cr) levels. MDA production was found to be higher in rats given AK than among control rats. CAPE administration before AK injection caused a significant decrease in MDA production. Morphological tubule damage in rats given AK was severe in the renal cortex, whereas in rats given AK plus CAPE, no histological changes occurred. It is concluded that CAPE could be useful for reducing the nephrotoxic effects of AK. Copyright (c) 2005 John Wiley & Sons, Ltd. 相似文献
105.
Sahin M Cam H Olgar S Tunc SE Arslan C Uz E Yilmaz HR 《Molecular and cellular biochemistry》2006,291(1-2):155-160
Drug-induced liver toxicity is a common cause of liver injury. This study was designed to elucidate whether high dose vancomycin (VCM) induces oxidative stress in liver and to investigate the protective effects of erdosteine, an expectorant agent. Twenty-two young Wistar rats were divided into three groups as follows: control group, VCM, and VCM plus erdosteine. VCM was administered intraperitoneally in the dosage of 200 mg/kg twice daily for 7 days. Erdosteine was administered orally administered once a day at a dose of 10 mg/kg body weight. The activities of antioxidant enzymes such as superoxide dismutase and catalase as well as the concentration of malondialdehyde, as an indicator of lipid peroxidation, were measured to evaluate oxidative stress in homogenates of the liver. VCM administration increased malondialdehyde levels (p < 0.001), superoxide dismutase (p < 0.01) and catalase (p < 0.001) activities. Erdosteine co-administration with VCM injections caused significantly decreased malondialdehyde levels (p < 0.001), superoxide dismutase (p < 0.01) and catalase (p < 0.001) activities in liver tissue when compared with VCM alone. It can be concluded that erdosteine may prevent VCM-induced oxidative changes in liver by reducing reactive oxygen species. 相似文献
106.
Cigremis Y Parlakpinar H Polat A Colak C Ozturk F Sahna E Ermis N Acet A 《Molecular and cellular biochemistry》2006,285(1-2):149-154
Doxorubicin (DOX) is a broad-spectrum anthracycline antibiotic that has cardiotoxicity as a major side effect. One mechanism of this toxicity is believed to involve the reactive oxygen radical species (ROS); these agents likely account for the pathophysiology of DOX-induced cardiomyopathy. Aminoguanidine (AG) is an effective antioxidant and free radical scavenger which has long been known to protect against ROS formation. We investigated the effects of AG on DOX-induced changes in thiobarbituric acid reactive substances (TBARS) and reduced glutathione (GSH) content. The rats were divided into four groups:1) Control; 2) DOX group; injected intraperitoneally (i.p.) with DOX 20 mg/kg in a single dose 3) AG-treated group; injected i.p. in single dose of 20 mg/kg DOX plus 100 mg/kg AG 1 h before the DOX for 3 days, 4) AG group; injected i.p. with AG 100 mg/kg for 3 days. DOX administration to control rats increased TBARS and decreased GSH levels. AG administration before DOX injection caused significant decrease in TBARS and increase in GSH levels in the heart tissue when compared with DOX only. Morphological changes, including severe myocardial fibrosis and inflammatory cell infiltration were clearly observed in the DOX-treated heart. AG reversed the DOX-induced heart damage. Therefore AG could protect the heart tissue against free radical injury. The application of AG during cancer chemotherapy may attenuate tissue damage and improve the therapeutic index of DOX. 相似文献
107.
Koklu E Kurtoglu S Akcakus M Koklu S Buyukkayhan D Gumus H Yikilmaz A 《Hormone research》2006,65(6):269-275
BACKGROUND AND AIM: Low birth-weight is known to be associated with an increase in cardiovascular risk similar to that seen with major environmental risk factors, such as cigarette smoking or hypertension. Much epidemiological evidence has linked low birth-weight with hypertriglyceridaemia. METHOD: We measured aortic wall thickness by ultrasonography and lipid profile in 40 newborn babies with intrauterine growth restriction and 40 controls. RESULTS: Maximum and mean aortic intima-media thickness were significantly higher in the babies with intrauterine growth retardation (0.58 +/- 0.06, 0.52 +/- 0.03 mm, respectively) than in controls (0.44 +/- 0.05, 0.40 +/- 0.03 mm, p < 0.0001, p < 0.0001, respectively), more so after adjustment for birth-weight (maximum intima-media thickness: 0.23 +/- 0.03 mm/kg vs. 0.12 +/- 0.02 mm/kg, p < 0.0001; mean intima-media thickness: 0.21 +/- 0.02 mm/kg vs. 0.11 +/- 0.01 mm/kg, p < 0.0001). Serum triglyceride levels were significantly higher in the intrauterine growth retardation group (48.9 +/- 14.8 mg/dl) compared with the control group (32.5 +/- 9.8 mg/dl, p < 0.0001). The mean body mass index, prepregnancy weight, weight gain during pregnancy, maternal LDL cholesterol level and, height of the mothers were significantly lower in the intrauterine growth retardation group compared with the control group. For maximum aIMT, significant associations included the ponderal index (p = <0.01), length (p = 0.01) and serum triglyceride levels of infants (p = 0.02). CONCLUSION: Newborn babies with growth restriction have significant maximum aortic thickening with hypertriglyceridaemia, suggesting that prenatal events might predispose to later cardiovascular risk. 相似文献
108.
The purpose of this study was to demonstrate the expression of nidogen-1 and nidogen-2 and their possible role in decidualization and implantation events during early pregnancy in rats. The tissue samples were examined from pregnant animals between gestational days 1-8 using immunocytochemistry. The uterine luminal epithelium, the glandular epithelium, and the myometrial smooth muscle cells stained strongly from gestational days 1-8 with both nidogen antibodies. At day 4 the decidual reaction areas began to appear in the stromal matrix and immunostaining of both nidogens revealed that the basement membrane of the surface epithelium was discontinuous. The differentiation of stromal cells into decidual cells was seen at gestational day 5 and both nidogens were weakly expressed in the decidualizing cells. At day 6, nidogen-2 immunoreactivity was higher in the primary decidual cells close to the embryo than nidogen-1, and during development of the decidual tissue both nidogens appeared in the endometrial stromal cells. At day 7, while expression of both nidogens declined in the primary decidual cells, their expression was markedly observed in the secondary decidual cells close to the myometrium. At day 8, expression of both nidogens was also observed to increase in the primary decidual cells. While nidogen-2 expression was seen in the parietal endoderm and primary ectoderm of the rat embryos at this developmental stage, nidogen-1 expression was only detected in the parietal endoderm. These results indicate that nidogen-1 and nidogen-2 could play important roles during embryogenesis, decidualization, and implantation in the endometrium of rat uterus. 相似文献
109.
The importance of arginine mutation for the evolutionary structure and function of phenylalanine hydroxylase gene 总被引:2,自引:0,他引:2
Lüleyap HU Alptekin D Pazarbaşi A Kasap M Kasap H Demirhindi H Mungan N Ozer G Froster UG 《Mutation research》2006,601(1-2):39-45
Phenylalanine hydroxylase (PAH) gene mutations were investigated in 23 (46 alleles) unrelated phenylketonuria (PKU) patients in Cukurova region. First, all exons of PAH gene were screened by denaturing high performance liquid chromatography (DHPLC), and then, the suspicious samples were analyzed by direct sequencing technique. Consequently, the following results were obtained: IVS10-11g-->a splicing mutation in 27/46 (58.7%), R261Q mutation in 7/46 (15.2%) and E178G, R243X, R243Q, P281L, Y386C, R408W mutations, each found in the frequency of 2/46 (4.3%). In many countries, Arginine mutations have the highest frequency among PAH gene mutations in PKU patients. Although, CpG dinucleotids are effective in mutations resulting in arginine changes, this finding originated from the studies on the causes of mutations rather than the studies on the importance of arginine amino acid. In our analyses, we have detected that a majority of mutations causing a change in arginine and other amino acids concentrated in exon 7 comprising the catalytic domain (residues 143-410) of PAH gene. Several studies has emphasized the role of arginine amino acid; with the following outcomes; arginine repetition is significant for RNA binding proteins, and for histon proteins in eukaryotic gene expression, and also arginine repetition occurring in the structure of signal recognition particle's (SRPs) as a consequence of post-translational processes is very important in terms of gene expression. Therefore, the role of arginine amino acid in PAH gene is rather remarkable in that it shows the role of amino acids in the protein/RNA interaction that has started in the evolutionary process and is still preserved and maintained in the motif formation of active domain structure due to its strong binding properties. Thus, such properties imply that both arginine amino acid and exon 7 is of great significance with regards to the structure and function of the PheOH enzyme. 相似文献
110.
Breeding performance,mate fidelity,and nest site fidelity in a long‐lived seabird: behaving against the current? 总被引:1,自引:0,他引:1
There is evidence that breeding failure is associated with divorce and dispersal in many bird species. However, deviations from the general pattern “success‐stay/failure‐leave” seem to be common, suggesting that factors other than breeding performance may importantly influence mate and habitat selection. Moreover, variability in response to performance suggests coexistence of different evolutionary strategies of mate and site selection within a population. In this study, we assessed how individuals conform to the success‐stay/failure‐leave pattern in kittiwakes (Rissa tridactyla), and aimed to identify categories of individuals presenting different behavioural patterns. We considered individual attributes (experience, prior residence at the nest site, performance in multiple breeding attempts), pair attributes (arrival asynchrony, timing of failure, pair duration), and productivity in habitat patches. Timing of failure was an important factor. Pair reunion probability was close to 0.5 in failed pairs, but it was consistently higher in early failed than in late failed pairs. Prior residence better explained variability in probability of reunion in failed pairs than pair duration. However, the positive influence of prior residence on the probability of reunion was perceptible only in early failed pairs. Divorce probability in successful pairs increased with arrival asynchrony, and was higher in first‐time than in experienced breeders. Local productivity positively influenced site fidelity probability in early failed birds, but not in late failed ones. Using memory models, we found that dispersal decisions integrate information on individual breeding performance in a temporal scale longer than one year. This study contributed to the identification of relevant states to be considered when addressing mate and nest site choice. Natural selection may operate on slight fitness differences that cannot be detected without high levels of stratification according to the appropriate individual and habitat attributes. 相似文献