全文获取类型
收费全文 | 5425篇 |
免费 | 611篇 |
国内免费 | 2篇 |
出版年
2021年 | 55篇 |
2020年 | 44篇 |
2019年 | 56篇 |
2018年 | 74篇 |
2017年 | 50篇 |
2016年 | 79篇 |
2015年 | 150篇 |
2014年 | 171篇 |
2013年 | 223篇 |
2012年 | 280篇 |
2011年 | 276篇 |
2010年 | 181篇 |
2009年 | 161篇 |
2008年 | 225篇 |
2007年 | 214篇 |
2006年 | 196篇 |
2005年 | 213篇 |
2004年 | 192篇 |
2003年 | 192篇 |
2002年 | 212篇 |
2001年 | 193篇 |
2000年 | 176篇 |
1999年 | 151篇 |
1998年 | 78篇 |
1997年 | 62篇 |
1996年 | 59篇 |
1995年 | 46篇 |
1994年 | 56篇 |
1993年 | 50篇 |
1992年 | 111篇 |
1991年 | 107篇 |
1990年 | 84篇 |
1989年 | 110篇 |
1988年 | 91篇 |
1987年 | 95篇 |
1986年 | 74篇 |
1985年 | 91篇 |
1984年 | 59篇 |
1983年 | 66篇 |
1982年 | 53篇 |
1981年 | 48篇 |
1980年 | 54篇 |
1979年 | 68篇 |
1978年 | 49篇 |
1977年 | 70篇 |
1976年 | 50篇 |
1975年 | 49篇 |
1974年 | 42篇 |
1973年 | 42篇 |
1971年 | 39篇 |
排序方式: 共有6038条查询结果,搜索用时 14 毫秒
901.
R S D Brown J Edwards J W Bartlett C Jones A Dogan 《The journal of histochemistry and cytochemistry》2002,50(1):113-115
Production of paraffin-section material from tissue samples that contain bone requires decalcification. Techniques such as acidic decalcification or EDTA chelation are suitable methods. Acid decalcification is generally quicker than EDTA chelation but studies have suggested that it may result in hydrolysis of DNA. Here we show that limited acid decalcification (less than 24 hr) in 5% formic acid can preserve DNA sufficient for fluorescent in situ hybridization (FISH) or comparative genomic hybridization (CGH) and that prolonged 10% formic acid decalcification results in failure of FISH and only limited retrieval of DNA for CGH studies. 相似文献
902.
During the last three years there have been a plethora of publications on the liver X-activated receptors (LXRalpha, NR1H3, and LXRbeta, NR1H2), the farnesoid X-activated receptor (FXR, NR1H4), and the pregnane X receptor (PXR, NR1I2) and the role these nuclear receptors play in controlling cholesterol, bile acid, lipoprotein and drug metabolism. The current interest in these nuclear receptors is high, in part, because they appear to be promising therapeutic targets for new drugs that have the potential to control lipid homeostasis.In this review we emphasize i) the role of LXR in controlling many aspects of cholesterol and fatty acid metabolism, ii) the expanded role of FXR in regulating genes that control not only bile acid metabolism but also lipoprotein metabolism, and iii) the regulation of bile acid transport/metabolism in response to bile acid-activated PXR. 相似文献
903.
Stem respiration increases in CO2 -enriched sweetgum trees 总被引:1,自引:1,他引:0
904.
905.
906.
The influence of earthworm-processed pig manure on the growth and productivity of marigolds. 总被引:3,自引:0,他引:3
The effects of additions of earthworm-processed pig manure (vermicompost) on the growth and productivity of French marigold (Tagetes patula) plants were evaluated under glasshouse conditions. Marigolds were germinated and grown in a standard commercial greenhouse container medium (Metro-Mix 360), substituted with 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, and 100% (by volume) pig manure vermicompost. The control consisted of Metro-Mix 360 alone without vermicompost. Plants were supplied regularly with a complete mineral nutrient solution for 121 days. The greatest vegetative growth resulted from substitution of Metro-Mix 360 with 30% and 40% pig manure vermicompost, and the lowest growth was in the potting mixtures containing 90% and 100% vermicompost. Most flower buds occurred in the potting mixtures containing 40% pig manure vermicompost (19.4 buds), and fewest in the potting mixtures containing 100% vermicompost. Marigolds grown in Metro-Mix 360 substituted with 90% and 100% pig manure vermicompost had the fewest and smallest flowers. After substitution of Metro-Mix 360 with 20%, 30%, 40%, 50%, 60%, 70%, 80%, and 90% vermicompost, the marigold roots were larger than those of plants grown in the Metro-Mix 360 controls. Substitution of Metro-Mix 360 with any concentration of pig manure vermicompost, with all needed nutrients provided, increased the overall nitrate-nitrogen concentrations of the marigold leaf tissues at flowering stage. Some of the marigold growth and productivity enhancement, resulting from substitution of Metro-Mix 360 with pig manure vermicompost, may be explained by nutritional factors; However, other, factors, such as plant-growth regulators and humates, might have also been involved since all plants were supplied regularly with all required nutrients. 相似文献
907.
Edwards Robert J. Garrett Gary P. Marsh-Matthews Edie 《Reviews in Fish Biology and Fisheries》2002,12(2-3):119-132
The Chihuahuan Desert region contains a numberof unique aquatic environments, but with fewexceptions, these have been little studied. Because of the dearth of information aboutthese environments and because many of the fishin the region are threatened with extinction orhave gone extinct, we sampled the RíoConchos basin and adjoining aquatic habitats inthe Rio Grande to assess the status of the fishof this region. Most sites showed some degreeof human-induced impacts. A number ofpotentially threatened fish were eitherabundant at only a few sites or rare or absentthroughout the localities sampled. Withoutconcerted binational efforts to conserve thefish of the region, further deletions to thenative fish fauna will likely occur. 相似文献
908.
Stabilization of (90)y-labeled DOTA-biomolecule conjugates using gentisic acid and ascorbic acid. 总被引:1,自引:0,他引:1
Radiolytic degradation of radiolabeled compounds is a major challenge for the development of new therapeutic radiopharmaceuticals. The goal of this study is to explore the factors influencing the solution stability of a (90)Y-labeled DOTA-peptide conjugate (RP697), including the amount of total activity, the activity concentration, the stabilizer concentration, and the storage temperature. In general, the rate of radiolytic decomposition of RP697 is much slower at the lower activity concentration (<4 mCi/mL) than that at the higher concentration (>10 mCi/mL). RP697 remains relatively stable at the 20 mCi level and room temperature while it decomposes rapidly at the 100 mCi level under the same storage conditions. Radical scavengers, such as gentisic acid (GA) and ascorbic acid (AA), were used in combination with the low temperature (-78 degrees C) to prevent the radiolytic decomposition of RP697. It was found that RP697 remains stable for at least 2 half-lives of (90)Y when GA or AA (10 mg for 20 mCi of (90)Y) is used as a stabilizer when the radiopharmaceutical composition is stored at -78 degrees C. The stabilizer (GA and AA) can be added into the formulation either before or after radiolabeling. The post-labeling approach is particularly useful when the use of a large amount of the stabilizer interferes with the radiolabeling. The radiopharmaceutical composition developed in this study can also apply to other (90)Y-labeled DOTA-biomolecule conjugates. The amount of the stabilizer used in the radiopharmaceutical composition and storage temperature should be adjusted according to the sensitivity of the radiolabeled DOTA-biomolecule conjugate toward radiolytic decomposition. 相似文献
909.
Cryptic differentiation and geographic variation in genetic diversity of Hall's Babbler Pomatostomus halli 总被引:1,自引:1,他引:0
Sequence variation was examined in domain I of the mitochondrial control region in three Queensland populations of Hall's Babbler Pomatostomus halli , a geographically restricted, monotypic songbird in eastern Australia. Surprisingly, we found that domain I sequences were strongly differentiated into two major clades differing by 3.29%. These two clades exhibited nearly complete geographic concordance with northern and southern populations, except for two haplotypes which were sampled in the north of the range but were phylogenetically allied to the southern clade. We also found a seven-fold higher level of genetic diversity in the northern than in the southern populations. Neutrality and molecular clock tests suggested that selection or differences in substitution rates were not responsible for this difference in diversity. However, a maximum likelihood analysis of gene flow between the north and south suggested that the difference in diversity could be due to both greater population size in the north and asymmetric gene flow dominated by south to north dispersal events. A likelihood ratio test rejected a model in which population sizes were equal and rates of gene flow symmetric, and came close to rejecting a model in which only population sizes were constrained to be equal. These results suggest that different population sizes and asymmetric gene flow could be a major source of differences in genetic variation between populations of Hall's Babbler, although ecological and biogeographic causes for these differences are obscure. 相似文献
910.
Kim E. Haworth Ira Islam Matthew Breen Wendy Putt Eleni Makrinou Matthew Binns David Hopkinson Yvonne Edwards 《Mammalian genome》2001,12(8):622-629
We describe the construction of a dog embryonic head/neck cDNA library and the isolation of the dog homolog of the Treacher
Collins Syndrome gene, TCOF1. The protein shows a similar three-domain structure to that described for human TCOF1, but the dog gene lacks exon 10 and
contains two exons not present in the human sequence. In addition, exon 19 is differentially spliced in the dog. How these
structural differences relate to TCOF1 phosphorylation is discussed. Isolation of a genomic clone allowed the exon/intron
boundaries to be characterized and the dog TCOF1 gene to be mapped to CF Chr 4q31, a region syntenic to human Chr 5. Genetic analysis of DNA of dogs from 13 different breeds
identified nine DNA sequence variants, three of which gave rise to amino acid substitutions. Grouping dogs according to head
type showed that a C396T variant, leading to a Pro117Ser substitution, is associated with skull/face shape in our dog panel.
The numbers are small, but the association between the T allele and brachycephaly, broad skull/short face, was highly significant
(p= 0.000024). The short period of time during which the domestic dog breeds have been established suggests that this mutation
has arisen only once in the history of dog domestication.
Received: 12 January 2001 / Accepted: 1 April 2001 相似文献