全文获取类型
收费全文 | 4486篇 |
免费 | 407篇 |
国内免费 | 2篇 |
出版年
2023年 | 12篇 |
2022年 | 21篇 |
2021年 | 61篇 |
2020年 | 48篇 |
2019年 | 56篇 |
2018年 | 55篇 |
2017年 | 75篇 |
2016年 | 100篇 |
2015年 | 195篇 |
2014年 | 193篇 |
2013年 | 271篇 |
2012年 | 349篇 |
2011年 | 365篇 |
2010年 | 231篇 |
2009年 | 218篇 |
2008年 | 319篇 |
2007年 | 263篇 |
2006年 | 265篇 |
2005年 | 247篇 |
2004年 | 238篇 |
2003年 | 248篇 |
2002年 | 214篇 |
2001年 | 63篇 |
2000年 | 48篇 |
1999年 | 63篇 |
1998年 | 63篇 |
1997年 | 40篇 |
1996年 | 54篇 |
1995年 | 45篇 |
1994年 | 40篇 |
1993年 | 31篇 |
1992年 | 50篇 |
1991年 | 28篇 |
1990年 | 32篇 |
1989年 | 25篇 |
1988年 | 26篇 |
1987年 | 21篇 |
1986年 | 12篇 |
1985年 | 20篇 |
1984年 | 18篇 |
1983年 | 19篇 |
1982年 | 11篇 |
1981年 | 12篇 |
1980年 | 12篇 |
1979年 | 12篇 |
1977年 | 11篇 |
1976年 | 10篇 |
1974年 | 9篇 |
1973年 | 11篇 |
1971年 | 11篇 |
排序方式: 共有4895条查询结果,搜索用时 15 毫秒
1.
Identifying common prognostic factors in genomic cancer studies: A novel index for censored outcomes
Background
With the growing number of public repositories for high-throughput genomic data, it is of great interest to combine the results produced by independent research groups. Such a combination allows the identification of common genomic factors across multiple cancer types and provides new insights into the disease process. In the framework of the proportional hazards model, classical procedures, which consist of ranking genes according to the estimated hazard ratio or the p-value obtained from a test statistic of no association between survival and gene expression level, are not suitable for gene selection across multiple genomic datasets with different sample sizes. We propose a novel index for identifying genes with a common effect across heterogeneous genomic studies designed to remain stable whatever the sample size and which has a straightforward interpretation in terms of the percentage of separability between patients according to their survival times and gene expression measurements. 相似文献2.
3.
4.
Use of ATP bioluminescence measurements for the estimation of biomass during biological humification
Summary The development of the microflora during the humification of grape pulp has been investigated by the determination of ATP using the bioluminescence technique. Several extraction methods were tested including the use of dimethylsulphoxide, trichloroacetic acid, grinding and ultrasonification. Dimethylsulphoxide and ultrasonification for 15 sec appeared to be the most effective. The ATP extract was stabilized when it was mixed with 0.75 mM glycine, 4.4 mM Mg-EDTA, pH 7.5 and frozen. The relative error of the ATP assay by bioluminescence did not exceed 6.5%. This method allowed us to show that at least five distinct reproducible microbial phases exist during grape pulp humification. These results show that the microbial biomass changes noticeably and at distinct times during composting. 相似文献
5.
Expression of alternatively spliced mRNA variants at specific stages of development or in specific cells and tissues contributes to the functional diversity of the human genome. Aberrations in alternative splicing were found as a cause or a contributing factor to the development, progression, or maintenance of numerous diseases. The use of antisense oligonucleotides (ON) to modify aberrant expression patterns of alternatively spliced mRNAs is a novel means of potentially controlling such diseases. Oligonucleotides can be designed to repair genetic mutations, to modify genomic sequences in order to compensate for gene deletions, or to modify RNA processing in order to improve the effects of the underlying gene mutation. Steric block ON approach have proven to be effective in experimental model for various diseases. Here, we describe our experience in investigating two strategies for ON delivery: ON conjugation with basic peptides and lipid-based particulate system (lipoplex). Basic peptides or Cell Penetrating Peptides (CPP) such as the TAT-derived peptide appear to circumvent many problems associated with ON and drug delivery. This strategy may represent the next paradigm in our ability to modulate cell function and offers a unique avenue for the treatment of disease. Lipoplexes result from the intimate interaction of ON with cationic lipids leading to ON carrying particles able to be taken up by cells and to release ON in the cytoplasm. We have used as an experimental model the correction of a splicing alteration of the mutated β-globin intron causing thalassemia. Data on cell penetration and efficacy of correction of specific steric block ON delivered either by basic peptides or lipoplex are described. A comparison of the properties of both delivery systems is made respective to the use of this new class of therapeutic molecules. 相似文献
6.
John E. Averett Elsa M. Zardini Peter C. Hoch 《Biochemical Systematics and Ecology》1990,18(7-8):529-532
Data for the flavonoids of 19 species in 10 sections of Ludwigia are presented. Eight flavonoids, comprising four glycoflavones, of which vitexin and isovitexin are reported for the first time in Ludwigia, and four flavonol glycosides, based on quercetin, are present in these species. Each section treated here has either glycoflavones or flavonols; presence of only onte class is considered to be advanced in the genus as a whole, compared with the presence of both glycoflavones and flavonols in the more generalized sects Myrtocarpus Cinerascentes, and Pterocaulon, which were examined earlier. Only glycoflavones are present in sects Macrocarpon (four species), Seminuda (five species), the ditypic African sect. Africana, the monotypic African sects Brenania, Cryptosperma, and Prieurea, the monotypic east Asian sect. Nipponia, and the monotypic pantropical section Fissendocarpa. Only flavonols are present in the monotypic Old Wodd section Caryophylloidea and sect. Oligospermum, which comprises nine species widespread in the OId and New Worlds. 相似文献
7.
Identification and sequence of the VH gene elements encoding a human anti-DNA antibody 总被引:12,自引:0,他引:12
Antibodies to DNA similar to those found in patients with systemic lupus erythematosus (SLE) and autoimmune mice can be derived from the lymphocytes of normal individuals. It is not known whether these normal derived anti-DNA antibodies are made from the same VH gene elements as the anti-DNA antibodies made by SLE patients. To begin to answer this question, we examined mu chain cDNA clones from human hybrid clone C6B2 producing anti-DNA antibodies. The sequence of the 500 base pair restriction fragment containing the variable region (5' terminus) was determined and was sequenced. This antibody uses a VHII heavy chain subgroup gene, a J3 joining segment, a hitherto unknown D segment, and a previously reported leader sequence. Significant homology was found to a mouse anti-DNA antibody sequence in the use of VH subgroup in J3, and in the hypervariable regions with a shared Ser-Tyr construction in CDR1 and an identical five amino acid residue stretch in CDR2. Comparison with the limited sequence data of published SLE monoclonal anti-DNA antibodies, both human and mouse, suggests that this shared Ser-Tyr may be important in some but not all antibodies to DNA. Comparison of C6B2 antibody is made with other known antibody sequences with identification of those residues likely to be part of the antigen binding site. 相似文献
8.
Horst Grunz Thierry Darribère Jean -Claude Boucaut 《Development genes and evolution》1987,196(4):203-209
Summary Antibodies directed to fibronectin (anti-FN) were injected into the blastocoel of late blastulae of Xenopus laevis. Two animal caps (ectoderm) were isolated, when control embryos reached the early gastrula stage, and were combined with untreated upper blastopore lip in the sandwich method. In two control series fibronectin or Holtfreter solution was injected into the blastocoel. The results of the experiments suggest that neural induction cannot be prevented by binding anti-FN to fibronectin, which covers the blastocoelic side of the ectoderm. The data support the view that extracellular matrix proteins are not themselves responsible for neural induction. However, in comparison with the control series a slight shift of the differentiation pattern in the spinocaudal direction could be observed in the anti-FN series. The possible role of extracellular proteins in the formation of a close juxtaposition of mesodermal and ectodermal target cells as a prerequisite for shortdistance transmission of neural inducers is discussed. 相似文献
9.
10.