全文获取类型
收费全文 | 1197篇 |
免费 | 90篇 |
出版年
2021年 | 17篇 |
2020年 | 11篇 |
2019年 | 8篇 |
2018年 | 23篇 |
2017年 | 13篇 |
2016年 | 12篇 |
2015年 | 26篇 |
2014年 | 37篇 |
2013年 | 45篇 |
2012年 | 52篇 |
2011年 | 48篇 |
2010年 | 33篇 |
2009年 | 36篇 |
2008年 | 46篇 |
2007年 | 46篇 |
2006年 | 36篇 |
2005年 | 55篇 |
2004年 | 42篇 |
2003年 | 44篇 |
2002年 | 33篇 |
2001年 | 31篇 |
2000年 | 30篇 |
1999年 | 29篇 |
1998年 | 20篇 |
1997年 | 20篇 |
1996年 | 12篇 |
1995年 | 10篇 |
1994年 | 16篇 |
1993年 | 16篇 |
1992年 | 29篇 |
1991年 | 25篇 |
1990年 | 21篇 |
1989年 | 11篇 |
1988年 | 19篇 |
1987年 | 21篇 |
1986年 | 14篇 |
1985年 | 16篇 |
1984年 | 19篇 |
1983年 | 10篇 |
1981年 | 14篇 |
1979年 | 9篇 |
1978年 | 17篇 |
1977年 | 10篇 |
1975年 | 11篇 |
1974年 | 8篇 |
1973年 | 16篇 |
1972年 | 15篇 |
1971年 | 13篇 |
1970年 | 11篇 |
1932年 | 9篇 |
排序方式: 共有1287条查询结果,搜索用时 15 毫秒
91.
Comparison of statistical methods for classification of ovarian cancer using mass spectrometry data 总被引:11,自引:0,他引:11
Wu B Abbott T Fishman D McMurray W Mor G Stone K Ward D Williams K Zhao H 《Bioinformatics (Oxford, England)》2003,19(13):1636-1643
MOTIVATION: Novel methods, both molecular and statistical, are urgently needed to take advantage of recent advances in biotechnology and the human genome project for disease diagnosis and prognosis. Mass spectrometry (MS) holds great promise for biomarker identification and genome-wide protein profiling. It has been demonstrated in the literature that biomarkers can be identified to distinguish normal individuals from cancer patients using MS data. Such progress is especially exciting for the detection of early-stage ovarian cancer patients. Although various statistical methods have been utilized to identify biomarkers from MS data, there has been no systematic comparison among these approaches in their relative ability to analyze MS data. RESULTS: We compare the performance of several classes of statistical methods for the classification of cancer based on MS spectra. These methods include: linear discriminant analysis, quadratic discriminant analysis, k-nearest neighbor classifier, bagging and boosting classification trees, support vector machine, and random forest (RF). The methods are applied to ovarian cancer and control serum samples from the National Ovarian Cancer Early Detection Program clinic at Northwestern University Hospital. We found that RF outperforms other methods in the analysis of MS data. 相似文献
92.
Aranzana MJ Pineda A Cosson P Dirlewanger E Ascasibar J Cipriani G Ryder CD Testolin R Abbott A King GJ Iezzoni AF Arús P 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2003,106(5):819-825
A set of 109 microsatellite primer pairs recently developed for peach and cherry have been studied in the almond x peach F(2) progeny previously used to construct a saturated Prunus map containing mainly restriction fragment length polymorphism markers. All but one gave amplification products, and 87 (80%) segregated in the progeny and detected 96 loci. The resulting Prunus map contains a total of 342 markers covering a total distance of 522 cM. The approximate position of nine additional simple sequence repeats (SSRs) was established by comparison with other almond and peach maps. SSRs were placed in all the eight linkage groups of this map, and their distribution was relatively even, providing a genome-wide coverage with an average density of 5.4 cM/SSR. Twenty-four single-locus SSRs, highly polymorphic in peach, and each falling within 24 evenly spaced approximately 25-cM regions covering the whole Prunus genome, are proposed as a 'genotyping set' useful as a reference for fingerprinting, pedigree and genetic analysis of this species. 相似文献
93.
Expressed sequence tag profiling identifies developmental and anatomic partitioning of gene expression in the mouse prostate 总被引:1,自引:1,他引:0
Abbott DE Pritchard C Clegg NJ Ferguson C Dumpit R Sikes RA Nelson PS 《Genome biology》2003,4(12):R79
Background
The prostate gland is an organ with highly specialized functional attributes that serves to enhance the fertility of mammalian species. Much of the information pertaining to normal and pathological conditions affecting the prostate has been obtained through extensive developmental, biochemical and genetic analyses of rodent species. Although important insights can be obtained through detailed anatomical and histological assessments of mouse and rat models, further mechanistic explanations are greatly aided through studies of gene and protein expression. 相似文献94.
Tardif SD Smucny DA Abbott DH Mansfield K Schultz-Darken N Yamamoto ME 《Comparative medicine》2003,53(4):364-368
Though sexual maturation may begin at around one year of age, first successful reproduction of the common marmoset (Callithrix jacchus) is likely to be later, and it is generally recommended that animals not be mated before 1.5 years of age. The average gestation period is estimated to be 143 to 144 days. A crown-rump length measurement taken by use of ultrasonography during the linear, rapid, prenatal growth phase (between approx. days 60 and 95) can be compared against standard growth curves to estimate delivery date to within 3 to 4 days, on average. Marmosets produce more young per delivery than does any other anthropoid primate, and have more variation in litter size. Many long-established colonies report that triplets are the most common litter size, and there is documented association between higher maternal body weight and higher ovulation numbers. Higher litter sizes generally do not generate higher numbers of viable young. Marmosets are unusual among primates in having a postpartum ovulation that typically results in conception and successful delivery; reported median inter-birth intervals range from 154 to 162 days. However, pregnancy losses are quite common; one study of a large breeding colony indicated 50 percent loss between conception and term delivery. The average life span for breeding females is around six years; the range of reported average lifetime number of litters for a breeding pair is 3.45 to 4.0. Our purpose is to provide an overview of reproduction in the common marmoset, including basic reproductive life history, lactation and weaning, social housing requirements, and common problems encountered in the captive breeding of this species. A brief comparison between marmoset and tamarin reproduction also will be provided. 相似文献
95.
Hardern IM Knauper V Ernill RJ Taylor IW Cooper KL Abbott WM 《Protein expression and purification》2000,19(2):246-252
We describe here the expression of a C-terminally truncated form of human procollagenase-3 in Escherichia coli. The protein was found almost exclusively in inclusion bodies that were solubilized and refolded by two separate methods and then purified on Ni-NTA agarose. The purified proenzyme could be activated with either trypsin or APMA and active enzyme could be purified on a peptidic hydroxamate affinity column. Competitive elution from the affinity matrix yielded a highly purified preparation. 相似文献
96.
97.
98.
Interest in the use of low-copy nuclear genes for phylogenetic analyses of
plants has grown rapidly, because highly repetitive genes such as those
commonly used are limited in number. Furthermore, because low- copy genes
are subject to different evolutionary processes than are plastid genes or
highly repetitive nuclear markers, they provide a valuable source of
independent phylogenetic evidence. The gene for granule-bound starch
synthase (GBSSI or waxy) exists in a single copy in nearly all plants
examined so far. Our study of GBSSI had three parts: (1) Amino acid
sequences were compared across a broad taxonomic range, including grasses,
four dicotyledons, and the microbial homologs of GBSSI. Inferred structural
information was used to aid in the alignment of these very divergent
sequences. The informed alignments highlight amino acids that are conserved
across all sequences, and demonstrate that structural motifs can be highly
conserved in spite of marked divergence in amino acid sequence. (2)
Maximum-likelihood (ML) analyses were used to examine exon sequence
evolution throughout grasses. Differences in probabilities among
substitution types and marked among-site rate variation contributed to the
observed pattern of variation. Of the parameters examined in our set of
likelihood models, the inclusion of among-site rate variation following a
gamma distribution caused the greatest improvement in likelihood score. (3)
We performed cladistic parsimony analyses of GBSSI sequences throughout
grasses, within tribes, and within genera to examine the phylogenetic
utility of the gene. Introns provide useful information among very closely
related species, but quickly become difficult to align among more divergent
taxa. Exons are variable enough to provide extensive resolution within the
family, but with low bootstrap support. The combined results of amino acid
sequence comparisons, maximum-likelihood analyses, and phylogenetic studies
underscore factors that might affect phylogenetic reconstruction. In this
case, accommodation of the variable rate of evolution among sites might be
the first step in maximizing the phylogenetic utility of GBSSI.
相似文献
99.
An improved method for culturing primary rat brain capillary endothelial cells on glass has been developed, using a corneal extracellular matrix coat. Since the collagen-coated plastic attachment surface conventionally used for primary cultures of brain microvascular endothelium gives a high level of background fluorescence in microfluorimetric studies, an alternative attachment surface was tested involving no plastic element. Five substrata combinations were examined and a new combination of glass and corneal endothelial extracellular matrix coat was found to provide excellent cell adhesion, culture growth and purity. Other established substrata combinations tested for comparison, either involved plastic, or used glass with collagen or carbodiimide and collagen coating but the last two gave poor endothelial cell adhesion and growth. Our method using this new attachment surface combination results in stable and pure endothelial cultures, as verified by immunocytochemistry, which are suitable for fluorimetric investigations. 相似文献
100.