全文获取类型
收费全文 | 391篇 |
免费 | 30篇 |
出版年
2023年 | 1篇 |
2022年 | 8篇 |
2021年 | 18篇 |
2020年 | 8篇 |
2019年 | 5篇 |
2018年 | 15篇 |
2017年 | 16篇 |
2016年 | 17篇 |
2015年 | 20篇 |
2014年 | 27篇 |
2013年 | 47篇 |
2012年 | 25篇 |
2011年 | 25篇 |
2010年 | 19篇 |
2009年 | 15篇 |
2008年 | 26篇 |
2007年 | 19篇 |
2006年 | 20篇 |
2005年 | 14篇 |
2004年 | 10篇 |
2003年 | 12篇 |
2002年 | 9篇 |
2001年 | 5篇 |
2000年 | 3篇 |
1999年 | 3篇 |
1998年 | 4篇 |
1997年 | 4篇 |
1996年 | 2篇 |
1995年 | 4篇 |
1994年 | 1篇 |
1993年 | 3篇 |
1992年 | 4篇 |
1991年 | 4篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1986年 | 2篇 |
1978年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
排序方式: 共有421条查询结果,搜索用时 15 毫秒
341.
Antimony trioxide (Sb2O3), in aqueous suspension, was administered by gavaging to mice and monitored for chromosomal aberrations in bone marrow and sperm head abnormalities in germ cells. Acute exposur to the doses followed by observations after 6, 12, 18 and 24 h did not show any clastogenic effects. Chronic exposure daily to different doses for periods up to 21 days induced chromosornal aberrations in bone marrow. The frequencies were dose-dependent to a significant extent but no relationship could be seen with the sex of the animal. The findings indicate the harmful effects of cumulative exposure for prolonged periods to Sb2O3, which is being increasingly used in various industries. 相似文献
342.
Six thermotolerant yeasts were isolated at 37 degrees C from over-ripe grapes by serial dilution technique using glucose yeast extract medium. Purified yeast cultures were screened for ethanol production at 37 degrees C by batch fermentation, using cane molasses containing 20% sugars. Sugar conversion efficiency of these isolates varied from 66.0 to 88.5% and ethanol productivity from 1.11 to 1.73 ml/l/h. The highest ethanol producing isolate was exposed to UV radiations and 13 mutants were picked up from the UV treatment exhibiting 0.1 to 1.0%, survival. The UV mutants varied in cell size from parent as well as among themselves. Determination of ethanol produced by all the mutants revealed that only five mutants resulted in 4.5 to 6.2% increase in sugar conversion and 8.25 to 18.56% increase in ethanol concentration coupled with maximum ethanol productivity of 2.4 ml/l/h in 48 h of batch fermentation of cane molasses (20% sugars) at 37 degrees C temperature. 相似文献
343.
D.N. Kamra R.K. Sawal N.N. Pathak Neelam Kewalramani Neeta Agarwal 《Letters in applied microbiology》1991,13(3):165-167
The protozoa in the rumen of a black buck were a B-type population with numbers varying between 0·31 and 0·61 times 106 cells/ml rumen liquor, when the animal was fed either vegetative green oat or third cut berseem. The total protozoa, total holotrichs, Dasytricha, total spirotrichs and small spirotrichs were significantly higher ( P < 0·01) on berseem feeding than those on oat feeding, while the numbers of Isotricha and large spirotrichs were unaffected by change of diet. Numerically the most important group of protozoa was small spirotrichs (74·4–75·6% of total population) which accounted for only 9·85–13·61% of protozoal cell mass in the rumen. 相似文献
344.
Pawels Kurian Neelam Narang L. Judson Chandler Fulton T. Crews 《Neurochemical research》1993,18(5):639-645
To investigate the effects of increasing concentrations ofmyo-inositol (inositol) on receptor stimulated [3H]inositol polyphosphate formation in the absence of lithium, slices of rat cerebral cortex were incubated with various concentrations of [3H]inositol (1 to 30 M). Carbachol stimulated formation of [3H]inositol trisphosphate (InsP3) and [3H]inositol 1,3,4,5-tetrakisphosphate {Ins(1,3,4,5)P4} increased several fold when the inositol concentration was increased reaching a plateau at approximately 12 M inositol. Time course studies revealed that in the presence of low concentrations of inositol (1 M), [3H]InsP3 and [3H]Ins(1,3,4,5)P4 formation in response to carbachol stimulation increased slowly over a 10 to 20 min time period, whereas in the presence of 4 and 12 M inositol, carbachol stimulated [3H]InsP3 and [3H]Ins(1,3,4,5)P4 formation was rapid and essentially complete within 3 to 5 min after carbachol addition. Although the carbachol dose response in 12 M inositol had a much greater maximal efficacy, there was no change in potency. Similar to the effects of carbachol on [3H]Ins(1,3,4,5)P4 formation from prelabeled phosphoinositides, muscarinic receptor stimulation increased Ins(1,3,4,5)P4 mass formation by seven fold. Furthermore, Li+ (8 mM) completely inhibited carbachol stimulated increases in Ins(1,3,4,5)P4 mass formation. In contrast to the effects of increasing inositol on carbachol stimulated formation of radiolabeled inositol phosphates, increasing inositol had no effect upon mass formation of Ins(1,3,4,5)P4. These results show that when measuring inositol polyphosphate formation by the radiolabeling technique in the absence of Li+, increasing the inositol concentration greatly increases the stimulated component of [3H]InsP3 and [3H]Ins(1,3,4,5)P4 formation. However, this inositol induced increase in agonist stimulated Ins(1,3,4,5)P4 formation is not reflected as an increase in mass formation. 相似文献
345.
346.
347.
Two new and seven known withanolides along with beta-sitosterol, stigmasterol, beta-sitosterol glucoside, stigmasterol glucoside, alpha+beta glucose were isolated from the roots of Withania somnifera. Among the known compounds, Viscosa lactone B, stigmasterol, stigmasterol glucoside and alpha+beta glucose are being reported from the roots of W. somnifera for the first time. One of the new compounds contained the rare 16beta-acetoxy-17(20)-ene the other contained unusual 6alpha-hydroxy-5,7alpha-epoxy functional groups in the withasteroid skeleton. The structures were elucidated by spectroscopic methods and chemical transformations. 相似文献
348.
Vijay K Tiwari Nidhi Rawat Kumari Neelam Gursharn S Randhawa Kuldeep Singh Parveen Chhuneja Harcharan S Dhaliwal 《Génome》2008,51(9):757-766
Four different interspecific hybrids involving three different accessions of Aegilops longissima Schweinf. & Muschl. with high grain iron and zinc content and three Triticum turgidum L. subsp. durum (Desf.) Husn. cultivars with low micronutrient content were made for durum wheat biofortification and investigated for chromosome pairing, fertility, putative amphiploidy, and micronutrient content. The chromosome pairing in the 21-chromosome F1 hybrids (ABSl) consisted of 0-6 rod bivalents and occasionally 1 trivalent. All the F1 hybrids, however, unexpectedly showed partial but variable fertility. The detailed meiotic investigation indicated the simultaneous occurrence of two types of aberrant meiotic divisions, namely first-division restitution and single-division meiosis, leading to regular dyads and unreduced gamete formation and fertility. The F2 seeds, being putative amphiploids (AABBSlSl), had nearly double the chromosome number (40-42) and regular meiosis and fertility. The F1 hybrids were intermediate between the two parents for different morphological traits. The putative amphiploids with bold seed size had higher grain ash content and ash iron and zinc content than durum wheat cultivars, suggesting that Ae. longissima possesses a better genetic system(s) for uptake and seed sequestration of iron and zinc, which could be transferred to elite durum and bread wheat cultivars and exploited. 相似文献
349.
Kumar S Khanduja KL Verma N Verma SC Avti PK Pathak CM 《Molecular and cellular biochemistry》2008,307(1-2):109-119
We investigated the in vitro efficacy of all-trans retinoic acid (ATRA) and alpha-tocopherol succinate (α-TS) alone and in combination on the induction of cell death in freshly
isolated leukemic cells obtained from chronic myeloid leukemia (CML) patients. In vitro cytotoxicity and induction of lipid
peroxidation by ATRA (10 μM) and α-TS (25 or 50 μM) were evaluated in primary leukemic cells by MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium
bromide] assay and malondialdehyde formation respectively. Treatment of leukemic cells with α-TS alone or in combination with
ATRA significantly (P < 0.05) decreased the cell viability in a concentration and time dependent manner as compared to peripheral blood mononuclear
cells obtained from normal healthy controls. Lipid peroxidation was enhanced by 98% (P < 0.05) on combined treatment of cells with ATRA (10 μM) and α-TS (50 μM). ATRA alone did not enhance the externalization
of phosphatidyl serine as studied by annexin-V binding using fluorescence activated cell sorter analysis, whereas in combination
with α-TS it increased to 400% at 12 h. The treatment of leukemic cells to combination of ATRA with α-TS significantly decreased
(P < 0.05) mitochondrial membrane potential and enhanced lysosomal destabilization. The combination of these drugs also increased
mitochondrial and cytosolic reactive oxygen species (ROS) production, nitric oxide levels, and caspase-3 activity significantly
and caused DNA fragmentation at 24 h in a concentration dependent manner in the leukemic cells. Our data suggest that ATRA
in combination with α-TS efficiently induces apoptosis in leukemic cells, which may be a useful therapeutic modality in CML
patients. 相似文献
350.