全文获取类型
收费全文 | 9726篇 |
免费 | 844篇 |
国内免费 | 2篇 |
出版年
2022年 | 104篇 |
2021年 | 206篇 |
2020年 | 100篇 |
2019年 | 136篇 |
2018年 | 166篇 |
2017年 | 155篇 |
2016年 | 269篇 |
2015年 | 391篇 |
2014年 | 457篇 |
2013年 | 555篇 |
2012年 | 690篇 |
2011年 | 790篇 |
2010年 | 403篇 |
2009年 | 359篇 |
2008年 | 495篇 |
2007年 | 571篇 |
2006年 | 496篇 |
2005年 | 441篇 |
2004年 | 427篇 |
2003年 | 434篇 |
2002年 | 409篇 |
2001年 | 183篇 |
2000年 | 142篇 |
1999年 | 142篇 |
1998年 | 90篇 |
1997年 | 93篇 |
1996年 | 76篇 |
1995年 | 73篇 |
1994年 | 45篇 |
1993年 | 50篇 |
1992年 | 106篇 |
1991年 | 98篇 |
1990年 | 56篇 |
1989年 | 89篇 |
1988年 | 66篇 |
1987年 | 76篇 |
1986年 | 45篇 |
1985年 | 52篇 |
1984年 | 59篇 |
1983年 | 48篇 |
1982年 | 38篇 |
1981年 | 46篇 |
1979年 | 40篇 |
1978年 | 47篇 |
1977年 | 59篇 |
1976年 | 59篇 |
1975年 | 49篇 |
1974年 | 46篇 |
1972年 | 61篇 |
1971年 | 39篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Plant and Soil - Cracks and biopores in compacted soil such as plough pans could aid deep rooting, mitigating constraints to seasonal upland use of paddy fields for rice production. This research... 相似文献
2.
3.
Analogs of the molluscan neuropeptide FMRFamide were tested on four different molluscan muscle preparations which show qualitatively different responses to the peptide; the structure-activity relations are basically similar, but not identical. The C-terminal amide and the Arg3 residue are critical for FMRFamide-like activity on all four preparations. In contrast, analogs extended at the N-terminal or with conservative substitutions for the Phe1 or Met2 residue are approximately equipotent to FMRFamide. These structural requirements parallel those for the C-terminal tetrapeptide amide of gastrin. 相似文献
4.
5.
Olga Maslova Oleg Fedevych Nadiia Shuvalova Olena Deryabina Volodymyr Zhovnir Miroslav Novak Peter Kruzliak 《Cell and tissue banking》2016,17(2):335-339
The need for selection of the optimal material for the manufacturing of cardio-patches can be resolved by the use of cryostored autologous pericardial tissue. This short communication is a concise fragment of a large-scale research and demonstrates only the efficiency of cell culturing before and after pericardial preservation in the low temperature conditions. 相似文献
6.
Household‐level correlates of children's physical activity levels in and across 12 countries
下载免费PDF全文
![点击此处可从《Obesity (Silver Spring, Md.)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Deirdre M. Harrington Fiona Gillison Stephanie T. Broyles Jean‐Philippe Chaput Mikael Fogelholm Gang Hu Rebecca Kuriyan Anura Kurpad Allana G. LeBlanc Carol Maher Jose Maia Victor Matsudo Timothy Olds Vincent Onywera Olga L. Sarmiento Martyn Standage Mark S. Tremblay Catrine Tudor‐Locke Pei Zhao Peter T. Katzmarzyk for the ISCOLE Research Group 《Obesity (Silver Spring, Md.)》2016,24(10):2150-2157
7.
Bennett Michael D.; Johnston Spencer; Hodnett George L.; Price H. James 《Annals of botany》2000,85(3):351-357
In 1965 Van't Hof estimated the nuclear DNA amount of an unidentifiedAllium cepa L. cultivar as 2C = 33.55 pg (Experimental CellResearch39: 858). This value has been adopted by commonusage as the main calibration standard for angiosperm DNA C-valueestimations. However, different cultivars have been used whileassuming species DNA C-value constancy. Surprisingly this assumptionhas never been tested. A. cepa is an outbreeder with telomericheterochromatic segments, so intraspecific variation in C-value,possibly correlated with environmental factors as seen in Zeamays L., might be expected. We used laser flow cytometry tocompare nuclear DNA amounts in roots of six A. cepa cultivarsused as calibration standards or from different environments.Tissues from one cultivar, or similar volumes of tissue fromtwo cultivars, were run and the variance between nuclei in 2Cpeaks compared. Only one shoulderless 2C peak was seen for allpairs of co-chopped cultivars. Thus, no large differences inC-value between cultivars from different environments were found.Moreover, comparing cultivars run singly or as pairs showedno evidence for increased variation in 2C peaks in the latter,and hence of critical differences in DNA amounts between AilsaCraig and another cultivar. Such variation was insufficientto make their use as alternative calibration standards, or thepractice of imputing Van't Hof's original C-value estimate tothem, unacceptable for most practical purposes. Given the mechanismsknown which can generate genome size variation, the degree ofconstancy in DNA C-value found seems remarkable. Copyright 2000Annals of Botany Company Allium cepa, onion cultivars, calibration standards, DNA C-value constancy, flow cytometry 相似文献
8.
Primary structure of bovine matrix Gla protein, a new vitamin K-dependent bone protein 总被引:7,自引:0,他引:7
The complete amino acid sequence of bovine bone matrix Gla protein (MGP) was determined by automatic sequence analysis of the intact protein and of peptides isolated from tryptic and BNPS-skatole digests. This 79-residue, vitamin K-dependent protein contains a single disulfide bond and 4.8 gamma-carboxyglutamate (Gla) residues, one each at positions 37, 41, 48, and 52, and 0.8 Gla and 0.2 Glu at position 2. There is sufficient sequence homology between MGP and bone Gla protein (BGP) to indicate that these two bovine bone proteins arose by gene duplication and subsequent divergent evolution. Although MGP has a very low solubility in water compared to BGP, there is no hydrophobic domain in MGP which could account for its insolubility, and the overall fraction of hydrophobic residues is 32% for MGP compared to 43% for BGP. MGP is the first vitamin K-dependent protein to be discovered which has several non-gamma-carboxylated residues to the NH2-terminal side of its Gla residues. The presence of NH2-terminal Glu residues between the putative targeting domain for the gamma-carboxylase in the MGP leader sequence and the mid-molecule Gla residues suggests that the gamma-carboxylase may have additional, as yet unrecognized, specificity requirements which determine the susceptibility of Glu residues for gamma-carboxylation. 相似文献
9.
10.