全文获取类型
收费全文 | 1088篇 |
免费 | 64篇 |
专业分类
1152篇 |
出版年
2024年 | 3篇 |
2023年 | 11篇 |
2022年 | 28篇 |
2021年 | 64篇 |
2020年 | 29篇 |
2019年 | 28篇 |
2018年 | 30篇 |
2017年 | 30篇 |
2016年 | 49篇 |
2015年 | 76篇 |
2014年 | 78篇 |
2013年 | 77篇 |
2012年 | 91篇 |
2011年 | 95篇 |
2010年 | 55篇 |
2009年 | 48篇 |
2008年 | 43篇 |
2007年 | 59篇 |
2006年 | 35篇 |
2005年 | 38篇 |
2004年 | 40篇 |
2003年 | 39篇 |
2002年 | 28篇 |
2001年 | 10篇 |
2000年 | 8篇 |
1999年 | 7篇 |
1998年 | 11篇 |
1997年 | 2篇 |
1996年 | 2篇 |
1995年 | 4篇 |
1994年 | 3篇 |
1993年 | 3篇 |
1992年 | 4篇 |
1991年 | 5篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1980年 | 1篇 |
1975年 | 1篇 |
1973年 | 2篇 |
1968年 | 2篇 |
排序方式: 共有1152条查询结果,搜索用时 15 毫秒
991.
Fatima Cvrčková 《Applied microbiology and biotechnology》1991,35(4):515-516
Summary A new selection method based on the use of chlorsulfuron (CS) resistance as the selection marker for protoplast fusion in industrial yeast has been introduced using the system of protoplast fusion. A petite mutant of a spontaneously CS-resistant distiller's Saccharomyces cerevisiae strain and a wild-type CS-sensitive strain of the osmotolerant yeast Zygosaccharomyces mellis were fused in order to obtain a distiller's yeast suitable for fermentations on concentrated molasses. Fusion products were isolated as large colonies on minimal glycerol agar with 0.5 mg ml–1 of the herbicide Glean (75% CS). Following prolonged cultivation on molasses, stable hybrid subxlones were obtained.
Offprint requests to: F. Cvrková 相似文献
992.
David Schlessinger Randy D. Little Diha Freije Fatima Abidi Ileana Zucchi Giovanni Porta Giuseppe Pilia Ramaiah Nagaraja Sandra K. Johnson Jae-Young Yoon Anand Srivastava Juha Kere Giuseppi Palmieri Alfredo Ciccodicola Vittorio Montanaro Giovanna Romano Amelia Casamassimi Michele D'Urso 《Genomics》1991,11(4)
Yeast artificial chromosomes (YACs) have recently provided a potential route to long-range coverage of complex genomes in contiguous cloned DNA. In a pilot project for 50 Mb (1.5% of the human genome), a variety of techniques have been applied to assemble Xq24–q28 YAC contigs up to 8 Mb in length and assess their quality. The results indicate the relative strength of several approaches and support the adequacy of YAC-based methods for mapping the human genome. 相似文献
993.
Frederick H. Kasten L. Fatima R. Pineda Paul E. Schneider H. Ralph Rawls Theda A. Foster 《In vitro cellular & developmental biology. Plant》1989,25(1):57-62
Summary Cell culture is a valuable method of evaluating the biocompatibility of new dental materials. The purpose of this study was
to compare the in vitro biocompatibility of an experimental fluoride composite resin with fluoride and non-fluoride-releasing
materials currently available. The dental materials tested were: MQ Silicate (silicate cement), KETAC-CEM and FUJI (type II
glass ionomer cements), VISIO DISPERS (a light-cured, nonfluoridated, microfilled composite resin), and FR-17 (an experimental
fluoride-releasing composite resin). The Smulow-Glickman (S-G) human, gingival epithelial cell line, which exhibits semidifferentiated
characteristics, was used in the study as a test system. Biocompatibility was quantified by counting the viable cells per
unit area remaining after 24 and 48 h at two radial distances from cured specimens immersed in the cell culture medium. The
test materials were observed to be most toxic to cells nearest the materials. A Time-Distance Cytotoxicity Index (TDCI) was
calculated to relate the percentage of dead cells to viable cells at each diffusion distance for each exposure time compared
to a nontoxic control. The relative toxicity ranking of the materials tested based on the TDCI was VISIO DISPERS (91%), FUJI
(82%), FR-17 (30%), MQ Silicate (23%), and KETAC-CEM (10%), which exhibited the least toxicity. The cytotoxicity of the experimental
resin FR-17 was within the range of cytotoxicity of currently accepted restorative materials.
this study was supported in part by grant R01-DE04749 from the National Institutes of Health, Bethesda, MD, to H. R. R., and
by grant no. S07-RR05704-13 from the Biomedical Research Grant Program, Division of Research Resources, National Institutes
of Health, awarded to the Louisiana State University School of Dentistry. 相似文献
994.
DHEA, DHEA sulphate and androstenedione are C19 steroïds secreted by the adrenal cortex. These hormones with a weak androgen activity are precursors of estrogens and androgens. In human and other primates these hormones are produced in important quantities, even though, in domestic and laboratory animals, a few secretion is measured. In this survey, the androstenedione is quantified both in plasma and adrenal gland of young, prepubertal and adult rabbits and the castration effects on adrenal cortex histology are noted too. The absolute weight (AW) of the left adrenal gland is slightly higher than the right (p > 0.05) for all animals and the gland absolute weight (AW) for the adult rabbit is superior to the young and prepubertal rabitts (p < 0.05). The castration effect in adult increases the adrenal weight (p < 0.001). A zonation of adrenal cortex for young rabbits is observed. The zona fasciculata is important for young and prepubertal rabbits whereas, the zona reticularis is thicker for the adults. Thickness of glomerulosa, fasciculata and reticularis zonas increased with 6.55% (p > 0.05), 15.9% (p < 0.01) and 79.21% (p < 0.001) for the castred adult rabbits and histological modifications were observed in the zona reticularis. The plasma androstenedione is negligible for the young (0.060 ± 0.01 ng/mL), weak for the prepubertal (0.152 ± 0.03 ng/mL) and reaches (0.263 ± 0.03 ng/mL) for the adult. The androstenedione relative content (ng/100 mg of adrenal weight) is 2.90 ± 0.30; 4.54 ± 0.82 and 1.34 ± 0.36 for the young, prepubertal and adult rabbits. In this work, an increase of the androstenedione adrenal content is observed for the prepubertal rabbits, which could intervene in the process of puberty. 相似文献
995.
Fatima N. Mirza Herbert Castillo Valladares Bradley Richards Kathleen C. Suozzi 《The Yale journal of biology and medicine》2021,94(3):459
Unmet dermatologic needs of the uninsured patient population are important to identify and address, especially as the COVID-19 pandemic has introduced additional barriers of access to care. We describe the successful collaboration between a student-run free clinic and dermatology practice since 2012, highlighting excellent time to appointment intervals and resolution rates as well as the associated modest financial cost. We believe that the information provided in our report may serve as a proof of concept and facilitate the implementation of such collaborations throughout the United States. 相似文献
996.
Poh SL el Khadali F Berrier C Lurz R Melki R Tavares P 《Journal of molecular biology》2008,378(3):551-564
Viral scaffolding proteins direct polymerization of major capsid protein subunits into icosahedral procapsid structures. The scaffolding protein of bacteriophage SPP1 was engineered with a C-terminal hexahistidine tag (gp11-His6) and purified. The protein is an α-helical-rich molecule with a very elongated shape as found for internal scaffolding proteins from other phages. It is a 3.3 S tetramer of 93.6 kDa at micromolar concentrations. Intersubunit cross-linking of these tetramers generated preferentially covalently bound dimers, revealing that gp11-His6 is structurally a dimer of dimers. Incubation at temperatures above 37 °C correlated with a reduction of its α-helical content and a less effective intersubunit cross-linking. Complete loss of secondary structure was observed at temperatures above 60 °C. Refolding of gp11-His6 thermally denatured at 65 °C led to reacquisition of the protein native ellipticity spectrum but the resulting population of molecules was heterogeneous. Its hydrodynamic behavior was compatible with a mix of 3.3 S elongated tetramers (∼ 90%) and a smaller fraction of 2.4 S dimers (∼ 10%). This population of gp11-His6 was competent to direct polymerization of the SPP1 major capsid protein gp13 into procapsid-like structures in a newly developed assembly assay in vitro. Although native tetramers were active in assembly, refolded gp11-His6 showed enhanced binding to gp13 revealing a more active species for interaction with the major capsid protein than native gp11-His6. 相似文献
997.
Peroxidase from bitter gourd was purified by three step purification scheme; ammonium sulphate fractionation, gel filtration and affinity chromatography. The enzyme was purified 42 fold with the retention of 67% of the initial activity. The enzyme exhibited its maximum activity at pH 5.6 and 40 degrees C. The enzyme retained half of its activity even after 1 h incubation at 60 degrees C. Molecular weight of the purified glycosylated bitter gourd peroxidase determined by Sephacryl S-100 and SDS-PAGE was 43 kDa. The stokes radius, diffusion coefficient and sedimentation coefficient of the purified peroxidase were 27.3 A, 8.17 x 10(-7) cm(2)/sec and 3.74 S, respectively. K(m) for o-dianisidine and ABTS were 1.3 and 4.9 mM, respectively. The activity of the enzyme was inhibited by sulfide, azide and L-cysteine. The carbohydrate content and sulfydryl groups of the enzyme were 25% (w/w) mass of the protein and 16 mmoles/mole of the protein, respectively. 相似文献
998.
There is a great demand for improved technologies with regard to rapid processing of nano- and microparticles. The handling of viruses in addition to microbial and mammalian cells requires the availability of appropriate adsorbents. Recent developments in macroporous gels produced at subzero temperatures (known as cryogels) have demonstrated an efficiency for processing cell and virus suspensions, cell separation and cell culture applications. Their unique combination of properties such as macroporosity, tissue-like elasticity and biocompatibility, physical and chemical stability and ease of preparation, renders these materials interesting candidates for a broad range of potential applications within microbiological research. This review describes current applications of macroporous cryogels in microbiology with a brief discussion of future perspectives. 相似文献
999.
Submicroscopic duplications of the hydroxysteroid dehydrogenase HSD17B10 and the E3 ubiquitin ligase HUWE1 are associated with mental retardation 下载免费PDF全文
Froyen G Corbett M Vandewalle J Jarvela I Lawrence O Meldrum C Bauters M Govaerts K Vandeleur L Van Esch H Chelly J Sanlaville D van Bokhoven H Ropers HH Laumonnier F Ranieri E Schwartz CE Abidi F Tarpey PS Futreal PA Whibley A Raymond FL Stratton MR Fryns JP Scott R Peippo M Sipponen M Partington M Mowat D Field M Hackett A Marynen P Turner G Gécz J 《American journal of human genetics》2008,82(2):432-443
Submicroscopic copy-number imbalances contribute significantly to the genetic etiology of human disease. Here, we report a novel microduplication hot spot at Xp11.22 identified in six unrelated families with predominantly nonsyndromic XLMR. All duplications segregate with the disease, including the large families MRX17 and MRX31. The minimal, commonly duplicated region contains three genes: RIBC1, HSD17B10, and HUWE1. RIBC1 could be excluded on the basis of its absence of expression in the brain and because it escapes X inactivation in females. For the other genes, expression array and quantitative PCR analysis in patient cell lines compared to controls showed a significant upregulation of HSD17B10 and HUWE1 as well as several important genes in their molecular pathways. Loss-of-function mutations of HSD17B10 have previously been associated with progressive neurological disease and XLMR. The E3 ubiquitin ligase HUWE1 has been implicated in TP53-associated regulation of the neuronal cell cycle. Here, we also report segregating sequence changes of highly conserved residues in HUWE1 in three XLMR families; these changes are possibly associated with the phenotype. Our findings demonstrate that an increased gene dosage of HSD17B10, HUWE1, or both contribute to the etiology of XLMR and suggest that point mutations in HUWE1 are associated with this disease too. 相似文献
1000.
Yasuhara F Gomes GR Siu ER Suenaga CI Maróstica E Porto CS Lazari MF 《Biology of reproduction》2008,79(3):432-441
The efferent ductules express the highest amount of estrogen receptors ESR1 (ERalpha) and ESR2 (ERbeta) within the male reproductive tract. Treatment of rats with the antiestrogen fulvestrant (ICI 182,780) causes inhibition of fluid reabsorption in the efferent ductules, leading to seminiferous tubule atrophy and infertility. To provide a more comprehensive knowledge about the molecular targets for estrogen in the rat efferent ductules, we investigated the effects of ICI 182,780 treatment on gene expression using a microarray approach. Treatment with ICI 182,780 increased or reduced at least 2-fold the expression of 263 and 98 genes, respectively. Not surprisingly, several genes that encode ion channels and macromolecule transporters were affected. Interestingly, treatment with ICI 182,780 markedly altered the expression of genes related to extracellular matrix organization. Matrix metalloproteinase 7 (Mmp7), osteopontin (Spp1), and neuronal pentraxin 1 (Nptx1) were among the most altered genes in this category. Upregulation of Mmp7 and Spp1 and downregulation of Nptx1 were validated by Northern blot. Increase in Mmp7 expression was further confirmed by immunohistochemistry and probably accounted for the decrease in collagen content observed in the efferent ductules of ICI 182,780-treated animals. Downregulation of Nptx1 probably contributed to the extracellular matrix changes and decreased amyloid deposition in the efferent ductules of ICI 182,780-treated animals. Identification of new molecular targets for estrogen action may help elucidate the regulatory role of this hormone in the male reproductive tract. 相似文献