全文获取类型
收费全文 | 388篇 |
免费 | 31篇 |
出版年
2023年 | 5篇 |
2022年 | 11篇 |
2021年 | 21篇 |
2020年 | 11篇 |
2019年 | 20篇 |
2018年 | 22篇 |
2017年 | 12篇 |
2016年 | 12篇 |
2015年 | 18篇 |
2014年 | 24篇 |
2013年 | 37篇 |
2012年 | 34篇 |
2011年 | 16篇 |
2010年 | 12篇 |
2009年 | 7篇 |
2008年 | 19篇 |
2007年 | 12篇 |
2006年 | 12篇 |
2005年 | 11篇 |
2004年 | 4篇 |
2003年 | 12篇 |
2002年 | 7篇 |
2001年 | 13篇 |
2000年 | 12篇 |
1999年 | 4篇 |
1998年 | 1篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1993年 | 4篇 |
1992年 | 3篇 |
1991年 | 3篇 |
1990年 | 10篇 |
1988年 | 5篇 |
1987年 | 3篇 |
1986年 | 1篇 |
1985年 | 3篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1977年 | 1篇 |
1974年 | 5篇 |
1973年 | 1篇 |
1971年 | 1篇 |
1969年 | 1篇 |
1967年 | 1篇 |
排序方式: 共有419条查询结果,搜索用时 15 毫秒
161.
162.
163.
164.
Twenty-eight patients with multiple myeloma have been treated with a quadruple chemotherapeutic regimen consisting of 1, 3 bis (2-chloroethyl)-1-nitrosourea (BCNU), cyclophosphamide, melphalan, and prednisolone. Nineteen new patients and nine who had escaped from previous single-agent therapy were included in the study. The results to date, on eight criteria of response, seem to be superior to those obtained from previous chemotherapeutic regimens. The study has been in progress for 18 months and only three patients have died. Only one who had not received previous therapy died, and she had complicating hyperparathyroidism, which almost certainly contributed to her death. 相似文献
165.
Biotic factors that affect phytoplankton physiology and behavior are not well characterized but probably play a crucial role in regulating their population dynamics in nature. We document evidence that some marine bacteria can decrease the swimming speed of motile phytoplankton through the release of putative protease(s). Using the dinoflagellate Lingulodinium polyedrum (F. Stein) J. D. Dodge as a model system, we showed that the motility‐reducing components of bacterial‐algal cocultures were mostly heat labile, were of high molecular weight (>50 kDa), and could be partially neutralized by incubations with protease inhibitors. We further showed that additions of the purified protease pronase E decreased dinoflagellate swimming speed in a concentration‐dependent manner. We propose that motility can be used as a marker for dinoflagellate stress or general unhealthy status due to proteolytic bacteria, among other factors. 相似文献
166.
Nazish Khan Ibrar Khan Sadiq Azam Farhan Ahmad Hamid Ali Khan Asma Shah Midrar Ullah 《Saudi Journal of Biological Sciences》2021,28(8):4793-4799
The Pinus wallichiana, Daphne oleiodes and Bidens chinensis have a long history of being used traditionally for treatment of various types of disorders. Most of the uses have been without any scientific evidence and toxicological assessment. We evaluated the mutagenic and cytotoxic capabilities of various parts of P. wallichiana, D. oleoides and B. chinensis. Ames Salmonella mutagenicity assay determined the mutagenicity activity against TA 98 and TA 100 bacterial strains of Salmonella typhimurium without metabolic activator S9 system. The number of mutant colonies in negative control was considered as limit to determine the mutagenicity effects of every extract. Brine shrimps lethality bioassay was used to determine the cytotoxic capabilities of the selected plants. The P. wallichiana, D. oleiodes and B. chinensis did not showed any mutagenic activity both for frameshift mutation (TA98) and base-pair substitution (TA100) without S9 mixture. The crude methanolic extract of P. wallichiana stem showed moderate cytotoxicity (53.33%) at 1000 μg/ml with LD50 value 599.634. The D. oleoides fruit showed a toxicity of 60% at 1000 μg/ml with LD50 value 367.730. The B. chinensis (whole plant) showed lethality of 63.3% at 1000 μg/ml, with LD50 204.833. The absence of any mutagenic activity of crude extract of the tested plants in both bacteria strains, TA 98 and TA 100 without the S9 mix confirms the safety of these plants to the consumers. 相似文献
167.
Saffron, a spice derived from the flower of Crocus sativus, is rich in carotenoids. Two main natural carotenoids of saffron, crocin and crocetin, are responsible for its color. Preclinical studies have shown that dietary intake of some carotenoids have potent anti-tumor effects both in vitro and in vivo, suggesting their potential preventive and/or therapeutic roles in several tissues. The reports represent that the use of carotenoids without the potential for conversion to vitamin A may provide further protection and avoid toxicity. The mechanisms underlying cancer chemo-preventive activities of carotenoids include modulation of carcinogen metabolism, regulation of cell growth and cell cycle progression, inhibition of cell proliferation, anti-oxidant activity, immune modulation, enhancement of cell differentiation, stimulation of cell-to-cell gap junction communication, apoptosis and retinoid-dependent signaling. Taken together, different hypotheses for the antitumor actions of saffron and its components have been proposed such as a) the inhibitory effect on cellular DNA and RNA synthesis, but not on protein synthesis; b) the inhibitory effect on free radical chain reactions; c) the metabolic conversion of naturally occurring carotenoids to retinoids; d) the interaction of carotenoids with topoisomerase II, an enzyme involved in cellular DNA-protein interaction. Furthermore, the immunomodulatory activity of saffron was studied on driving toward Th1 and Th2 limbs of the immune system. In this mini-review, we briefly describe biochemical and immunological activities and chemo-preventive properties of saffron and natural carotenoids as an anticancer drug. 相似文献
168.
Zehra Agha Zafar Iqbal Maleeha Azam Maimoona Siddique Marjolein H. Willemsen Tjitske Kleefstra Christiane Zweier Nicole de Leeuw Raheel Qamar Hans van Bokhoven 《Gene》2014
We report on a consanguineous Pakistani family with a severe congenital microcephaly syndrome resembling the Seckel syndrome and Jawad syndrome. The affected individuals in this family were born to consanguineous parents of whom the mother presented with mild intellectual disability (ID), epilepsy and diabetes mellitus. The two living affected brothers presented with microcephaly, white matter disease of the brain, hyponychia, dysmorphic facial features with synophrys, epilepsy, diabetes mellitus and ID. Genotyping with a 250K SNP array in both affected brothers revealed an 18 MB homozygous region on chromosome 18p11.21-q12.1 encompassing the SCKL2 locus of the Seckel and Jawad syndromes. Sequencing of the RBBP8 gene, underlying the Seckel and Jawad syndromes, identified the novel mutation c.919A > G, p.Arg307Gly, segregating in a recessive manner in the family. In addition, in the two affected brothers and their mother we have also found a heterozygous 607 kb deletion, encompassing exons 13–19 of NRXN1. Bidirectional sequencing of the coding exons of NRXN1 did not reveal any other mutation on the other allele. It thus appears that the phenotype of the mildly affected mother can be explained by the NRXN1 deletion, whereas the more severe and complex microcephalic phenotype of the two affected brothers is due to the simultaneous deletion in NRXN1 and the homozygous missense mutation affecting RBBP8. 相似文献
169.
Essential‐Oil Composition of the Fruits of Six Heracleum L. Species from Iran: Chemotaxonomic Significance
下载免费PDF全文
![点击此处可从《化学与生物多样性》网站下载免费的PDF全文](/ch/ext_images/free.gif)
The fruit essential oils of Heracleum persicum, H. rechingeri, H. gorganicum, H. rawianum, H. pastinacifolium, and H. anisactis from Iran were obtained by hydrodistillation and characterized by GC‐FID and GC/MS analyses. The oils of the six species were compared to determine the similarities and differences among their compositions. Overall, 36 compounds were identified in the fruit oils, accounting for 92.40–96.74% of the total oil compositions. Aliphatic esters constituted the main fraction of the oils (86.61–94.31%), with octyl acetate and hexyl butyrate as the major components. The oil compositions of species belonging to section Pubescentia (H. persicum, H. gorganicum, and H. rechingeri) were discriminated by equally high contents of both octyl acetate (13.84–20.48%) and hexyl butyrate (17.73–38.36%). On the other hand, the oils of H. rawianum, H. pastinacifolium and H. anisactis, belonging to section Wendia, showed lower hexyl butyrate contents (3.62–6.6%) and higher octyl acetate contents (48.71–75.36%) than the former. Moreover, isoelemicin was identified at low amounts (0.10–2.51%) only in the oils of the latter species. The differences in the oil composition among the six species were investigated by hierarchical cluster and principal component analyses, which indicated that the oil composition confirmed well the taxonomical classification based on the morphological and botanical data, and, thus, may provide a reliable marker to discriminate Heracleum species at the intersectional level. 相似文献
170.
Pradeep Ruperao Chon‐Kit Kenneth Chan Sarwar Azam Miroslava Karafiátová Satomi Hayashi Jana Čížková Rachit K. Saxena Hana Šimková Chi Song Jan Vrána Annapurna Chitikineni Paul Visendi Pooran M. Gaur Teresa Millán Karam B. Singh Bunyamin Taran Jun Wang Jacqueline Batley Jaroslav Doležel Rajeev K. Varshney David Edwards 《Plant biotechnology journal》2014,12(6):778-786
With the expansion of next‐generation sequencing technology and advanced bioinformatics, there has been a rapid growth of genome sequencing projects. However, while this technology enables the rapid and cost‐effective assembly of draft genomes, the quality of these assemblies usually falls short of gold standard genome assemblies produced using the more traditional BAC by BAC and Sanger sequencing approaches. Assembly validation is often performed by the physical anchoring of genetically mapped markers, but this is prone to errors and the resolution is usually low, especially towards centromeric regions where recombination is limited. New approaches are required to validate reference genome assemblies. The ability to isolate individual chromosomes combined with next‐generation sequencing permits the validation of genome assemblies at the chromosome level. We demonstrate this approach by the assessment of the recently published chickpea kabuli and desi genomes. While previous genetic analysis suggests that these genomes should be very similar, a comparison of their chromosome sizes and published assemblies highlights significant differences. Our chromosomal genomics analysis highlights short defined regions that appear to have been misassembled in the kabuli genome and identifies large‐scale misassembly in the draft desi genome. The integration of chromosomal genomics tools within genome sequencing projects has the potential to significantly improve the construction and validation of genome assemblies. The approach could be applied both for new genome assemblies as well as published assemblies, and complements currently applied genome assembly strategies. 相似文献