全文获取类型
收费全文 | 4665篇 |
免费 | 469篇 |
专业分类
5134篇 |
出版年
2022年 | 34篇 |
2021年 | 56篇 |
2020年 | 44篇 |
2019年 | 55篇 |
2018年 | 56篇 |
2017年 | 79篇 |
2016年 | 88篇 |
2015年 | 146篇 |
2014年 | 190篇 |
2013年 | 202篇 |
2012年 | 277篇 |
2011年 | 257篇 |
2010年 | 184篇 |
2009年 | 167篇 |
2008年 | 229篇 |
2007年 | 207篇 |
2006年 | 190篇 |
2005年 | 205篇 |
2004年 | 211篇 |
2003年 | 204篇 |
2002年 | 166篇 |
2001年 | 181篇 |
2000年 | 149篇 |
1999年 | 146篇 |
1998年 | 79篇 |
1997年 | 81篇 |
1996年 | 61篇 |
1995年 | 45篇 |
1994年 | 64篇 |
1993年 | 45篇 |
1992年 | 86篇 |
1991年 | 73篇 |
1990年 | 72篇 |
1989年 | 71篇 |
1988年 | 57篇 |
1987年 | 41篇 |
1986年 | 40篇 |
1985年 | 67篇 |
1984年 | 43篇 |
1983年 | 35篇 |
1982年 | 39篇 |
1981年 | 26篇 |
1980年 | 25篇 |
1979年 | 42篇 |
1978年 | 23篇 |
1977年 | 23篇 |
1976年 | 24篇 |
1974年 | 29篇 |
1973年 | 23篇 |
1972年 | 23篇 |
排序方式: 共有5134条查询结果,搜索用时 9 毫秒
161.
Renewed examinatinon with improved banding techniques of a boy previously reported to have the karyotype 46, XY,del(12)(p11) revealed a translocation 46, XY,t(10;12)(p13;p11), and reexamination of a boy previously reported to have the karyotype 46,XY/46,XY,del(5)(p13) showed the same mosaicism, but with a significantly lower frequency of cells with del(5)(p13), 8% compared with 23% at the time of birth. The decrease of the frequency of cells with chromosome abnormality in mixoploids during the first years of life as found in the present case as well as in prevously reported cases is discussed. 相似文献
162.
Summary A family with autosomal reciprocal translocation t(4;13) (q25;q31) with a sibship comprising 2 children with unbalanced karyotypes, der(13) partial trisomy 4q, 1 child with the balanced translocation, and 2 abortions were studied. The segregation risk of unbalanced derivation in reciprocal translocations is discussed. The clinical picture of the 2 children with partial trisomy 4q is compared with similar cases. 相似文献
163.
Summary The incidence of Edwards' syndrome was found to be 1 per 4857 newborn children of 34000 consecutively newborn children in two Danish counties. Six of the 7 cases were born during the months of February through April.The incidence was high compared with the expected incidence of Edwards' syndrome of approximately 1 per 10000. This might be due to clustering in the area studied during the period 1967 to 1973.The finding of variations in incidence of children with Edwards' syndrome in different parts of the world, as well as the finding of seasonal variation in birth of such children, indicates that some of the etiological factors of nondisjunction of chromosome 18 are of an environmental nature. 相似文献
164.
Johannes Nielsen 《Human genetics》1975,26(3):215-222
Summary The purpose of making chromosome investigations of newborn children as well as ethical problems in such studies and in follow-up studies of children with chromosome abnormalities is discussed, and a survey of 6 chromosome studies from a total of 47145 newborn children is presented.It is stressed that more chromosome studies of newborn children are needed for several reasons, but one of the main reasons is to study the development of children with different chromosome abnormalities, especially those with sex-chromosome abnormalities and compare them with controls. 相似文献
165.
Johannes Nielsen 《Human genetics》1975,29(2):155-159
166.
Vernica S. Martínez Pedro A. Saa Jason Jooste Kanupriya Tiwari Lake-Ee Quek Lars K. Nielsen 《PLoS computational biology》2022,18(6)
The topology of metabolic networks is recognisably modular with modules weakly connected apart from sharing a pool of currency metabolites. Here, we defined modules as sets of reversible reactions isolated from the rest of metabolism by irreversible reactions except for the exchange of currency metabolites. Our approach identifies topologically independent modules under specific conditions associated with different metabolic functions. As case studies, the E.coli iJO1366 and Human Recon 2.2 genome-scale metabolic models were split in 103 and 321 modules respectively, displaying significant correlation patterns in expression data. Finally, we addressed a fundamental question about the metabolic flexibility conferred by reversible reactions: “Of all Directed Topologies (DTs) defined by fixing directions to all reversible reactions, how many are capable of carrying flux through all reactions?”. Enumeration of the DTs for iJO1366 model was performed using an efficient depth-first search algorithm, rejecting infeasible DTs based on mass-imbalanced and loopy flux patterns. We found the direction of 79% of reversible reactions must be defined before all directions in the network can be fixed, granting a high degree of flexibility. 相似文献
167.
Dana J. Morin Damon B. Lesmeister Clayton K. Nielsen Eric M. Schauber 《Ecology and evolution》2022,12(7)
Species coexistence is governed by availability of resources and intraguild interactions including strategies to reduce ecological overlap. Gray foxes are dietary generalist mesopredators expected to benefit from anthropogenic disturbance, but populations have declined across the midwestern USA, including severe local extirpation rates coinciding with high coyote and domestic dog occurrence and low red fox occurrence. We used data from a large‐scale camera trap survey in southern Illinois, USA to quantify intraguild spatial and temporal interactions among the canid guild including domestic dogs. We used a two‐species co‐occurrence model to make pairwise assessments of conditional occupancy and detection rates. We also estimated temporal activity overlap among species and fit a fixed‐effects hierarchical community occupancy model with the four canid species. We partitioned the posterior distributions to compare gray fox occupancy probabilities conditional on estimated state of combinations of other species to assess support for hypothesized interactions. We found no evidence of broadscale avoidance among native canids and conclude that spatial and temporal segregation were limited by ubiquitous human disturbance. Mean guild richness was two canid species at a site and gray fox occupancy was greater when any combination of sympatric canids was also present, setting the stage for competitive exclusion over time. Domestic dogs may amplify competitive interactions by increasing canid guild size to the detriment of gray foxes. Our results suggest that while human activities can benefit some mesopredators, other species such as gray foxes may serve as bellwethers for habitat degradation with trophic downgrading and continued anthropogenic homogenization. 相似文献
168.
Improving the phenotype predictions of a yeast genome‐scale metabolic model by incorporating enzymatic constraints
下载免费PDF全文
![点击此处可从《Molecular systems biology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Avlant Nilsson Petri‐Jaan Lahtvee Eduard J Kerkhoven Jens Nielsen 《Molecular systems biology》2017,13(8)
Genome‐scale metabolic models (GEMs) are widely used to calculate metabolic phenotypes. They rely on defining a set of constraints, the most common of which is that the production of metabolites and/or growth are limited by the carbon source uptake rate. However, enzyme abundances and kinetics, which act as limitations on metabolic fluxes, are not taken into account. Here, we present GECKO, a method that enhances a GEM to account for enzymes as part of reactions, thereby ensuring that each metabolic flux does not exceed its maximum capacity, equal to the product of the enzyme's abundance and turnover number. We applied GECKO to a Saccharomyces cerevisiae GEM and demonstrated that the new model could correctly describe phenotypes that the previous model could not, particularly under high enzymatic pressure conditions, such as yeast growing on different carbon sources in excess, coping with stress, or overexpressing a specific pathway. GECKO also allows to directly integrate quantitative proteomics data; by doing so, we significantly reduced flux variability of the model, in over 60% of metabolic reactions. Additionally, the model gives insight into the distribution of enzyme usage between and within metabolic pathways. The developed method and model are expected to increase the use of model‐based design in metabolic engineering. 相似文献
169.
Nicolas Rapin Can Kesmir Sune Frankild Morten Nielsen Claus Lundegaard Søren Brunak Ole Lund 《Journal of biological physics》2006,32(3-4):335-353
Over the past decade a number of bioinformatics tools have been developed that use genomic sequences as input to predict to
which parts of a microbe the immune system will react, the so-called epitopes. Many predicted epitopes have later been verified
experimentally, demonstrating the usefulness of such predictions. At the same time, simulation models have been developed
that describe the dynamics of different immune cell populations and their interactions with microbes. These models have been
used to explain experimental findings where timing is of importance, such as the time between administration of a vaccine
and infection with the microbe that the vaccine is intended to protect against. In this paper, we outline a framework for
integration of these two approaches. As an example, we develop a model in which HIV dynamics are correlated with genomics
data. For the first time, the fitness of wild type and mutated virus are assessed by means of a sequence-dependent scoring
matrix, derived from a BLOSUM matrix, that links protein sequences to growth rates of the virus in the mathematical model.
A combined bioinformatics and systems biology approach can lead to a better understanding of immune system-related diseases
where both timing and genomic information are of importance. 相似文献
170.