全文获取类型
收费全文 | 4672篇 |
免费 | 459篇 |
国内免费 | 2篇 |
出版年
2023年 | 16篇 |
2022年 | 54篇 |
2021年 | 130篇 |
2020年 | 67篇 |
2019年 | 103篇 |
2018年 | 102篇 |
2017年 | 86篇 |
2016年 | 134篇 |
2015年 | 241篇 |
2014年 | 243篇 |
2013年 | 266篇 |
2012年 | 330篇 |
2011年 | 283篇 |
2010年 | 185篇 |
2009年 | 168篇 |
2008年 | 237篇 |
2007年 | 212篇 |
2006年 | 191篇 |
2005年 | 192篇 |
2004年 | 160篇 |
2003年 | 164篇 |
2002年 | 142篇 |
2001年 | 115篇 |
2000年 | 109篇 |
1999年 | 95篇 |
1998年 | 54篇 |
1997年 | 47篇 |
1996年 | 54篇 |
1995年 | 45篇 |
1994年 | 41篇 |
1993年 | 41篇 |
1992年 | 74篇 |
1991年 | 69篇 |
1990年 | 74篇 |
1989年 | 47篇 |
1988年 | 48篇 |
1987年 | 46篇 |
1986年 | 36篇 |
1985年 | 49篇 |
1984年 | 30篇 |
1983年 | 43篇 |
1982年 | 41篇 |
1981年 | 28篇 |
1980年 | 20篇 |
1979年 | 28篇 |
1978年 | 15篇 |
1977年 | 22篇 |
1976年 | 16篇 |
1975年 | 16篇 |
1968年 | 13篇 |
排序方式: 共有5133条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
5.
Heidi Weberru? Raphael Pirzer Robert Dalla Pozza Heinrich Netz Renate Oberhoffer 《PloS one》2016,11(3)
Carotid intima-media thickness (cIMT) is a surrogate marker of early atherosclerotic changes in children. cIMT-studies are hard to compare, due to variations in ultrasound protocols, especially regarding the common carotid artery (CCA) segment measured in relation to the bulb. This study’s purpose was therefore to compare two distinct CCA segments in children, to see if cIMT values differ substantially according to the site of measurement. cIMT was assessed after power calculation in 30 children (15 girls) aged 8–17, using B-Mode ultrasound (5–13 MHz) at two CCA locations. The first measurement was performed over a distance of 1 cm immediately after the bulb (A), the second 1cm proximal the bulb (B) over the same distance of 1cm length. Means of end-diastolic far wall cIMT were compared between measurement A and B. cIMT in 30 participants was 0.51±0.06 mm for measurement A and 0.51±0.05 mm for measurement B. Results did not differ significantly (p = .947) over a distance of 2 cm after the bulb. According to our results, studies measuring CCA IMT within the first 2 cm, either close to the bulb or further proximal, can be compared. This will improve interpretation of data and application of reference values. 相似文献
6.
Kathryn S. Evans Janneke Wit Lewis Stevens Steffen R. Hahnel Briana Rodriguez Grace Park Mostafa Zamanian Shannon C. Brady Ellen Chao Katherine Introcaso Robyn E. Tanny Erik C. Andersen 《PLoS pathogens》2021,17(3)
Parasitic nematodes cause a massive worldwide burden on human health along with a loss of livestock and agriculture productivity. Anthelmintics have been widely successful in treating parasitic nematodes. However, resistance is increasing, and little is known about the molecular and genetic causes of resistance for most of these drugs. The free-living roundworm Caenorhabditis elegans provides a tractable model to identify genes that underlie resistance. Unlike parasitic nematodes, C. elegans is easy to maintain in the laboratory, has a complete and well annotated genome, and has many genetic tools. Using a combination of wild isolates and a panel of recombinant inbred lines constructed from crosses of two genetically and phenotypically divergent strains, we identified three genomic regions on chromosome V that underlie natural differences in response to the macrocyclic lactone (ML) abamectin. One locus was identified previously and encodes an alpha subunit of a glutamate-gated chloride channel (glc-1). Here, we validate and narrow two novel loci using near-isogenic lines. Additionally, we generate a list of prioritized candidate genes identified in C. elegans and in the parasite Haemonchus contortus by comparison of ML resistance loci. These genes could represent previously unidentified resistance genes shared across nematode species and should be evaluated in the future. Our work highlights the advantages of using C. elegans as a model to better understand ML resistance in parasitic nematodes. 相似文献
7.
The intensity of sperm competition is often measured using the gonadosomatic index (testes/body weight). But sperm competition could be mediated more by size of the epididymis than by size of the testicles, and little information is available on the relationship between testicular and epididymal size. We found that both organs were positively correlated in size among male rhesus macaques. Body weight accounted for over 70% of the variance in testicle size and volumetric estimates of testicle size accurately reflected testicle weight. We conclude that methods for ascertaining testicle size are accurate, but the covariation in size between testicles and epididymis will hamper understanding of the physiological mechanisms involved in sperm competition in primates. © 1993 Wiley-Liss, Inc. 相似文献
8.
9.
10.
Summary The xylanolytic and cellulolytic activity fromCellulomanas were reduced by high O2 concentrations in continous culture as well as by an air flow passed trough the samples, suggesting an inhibition or inactivation of enzymes in such conditions. 相似文献