全文获取类型
收费全文 | 8223篇 |
免费 | 738篇 |
国内免费 | 7篇 |
出版年
2022年 | 68篇 |
2021年 | 116篇 |
2020年 | 86篇 |
2019年 | 100篇 |
2018年 | 128篇 |
2017年 | 107篇 |
2016年 | 165篇 |
2015年 | 291篇 |
2014年 | 318篇 |
2013年 | 416篇 |
2012年 | 499篇 |
2011年 | 540篇 |
2010年 | 364篇 |
2009年 | 303篇 |
2008年 | 454篇 |
2007年 | 438篇 |
2006年 | 360篇 |
2005年 | 388篇 |
2004年 | 354篇 |
2003年 | 352篇 |
2002年 | 359篇 |
2001年 | 176篇 |
2000年 | 152篇 |
1999年 | 148篇 |
1998年 | 95篇 |
1997年 | 77篇 |
1996年 | 76篇 |
1995年 | 85篇 |
1994年 | 75篇 |
1993年 | 63篇 |
1992年 | 91篇 |
1991年 | 107篇 |
1990年 | 93篇 |
1989年 | 79篇 |
1988年 | 76篇 |
1987年 | 76篇 |
1986年 | 60篇 |
1985年 | 64篇 |
1984年 | 63篇 |
1983年 | 59篇 |
1982年 | 47篇 |
1981年 | 55篇 |
1980年 | 47篇 |
1979年 | 47篇 |
1978年 | 52篇 |
1977年 | 40篇 |
1976年 | 44篇 |
1975年 | 58篇 |
1974年 | 66篇 |
1971年 | 53篇 |
排序方式: 共有8968条查询结果,搜索用时 15 毫秒
1.
Yohannes M. S. Samosir Steve Adkins 《In vitro cellular & developmental biology. Plant》2014,50(4):493-501
An in vitro photoautotrophic step based on the supply of CO2-enriched air (1,600 μmol mol?1) during the light phase and ambient air (350 μmol mol?1 CO2) during the dark phase has been used to promote the ex vitro establishment of coconut (Cocos nucifera L.) seedlings. The introduction of this step into a previously developed in vitro protocol was found to improve the quality of the seedlings (as assessed by fresh weight increase, physical stature, leaf area and thickness, stomatal density, and chlorophyll a content, and primary and secondary root production), the proportion of seedlings successfully transferred to soil (improvement from 40% to 100%) and achieved in a shorter time (reduction from 10 to 6 mo). Best results using this photoautotrophic growth step were obtained when a low medium concentration of sucrose (43.8 mM or lower) was used, when it was applied to seedlings that had already reached 4 or 5 mo of age in the in vitro culture step, and when seedlings were cultured in the photoautotrophic system for 2 mo or more before transfer to soil. Our improved protocol is more efficient and it reduces the cost per plant for the international exchange of coconut germplasm. 相似文献
2.
3.
Edward Harrison 《BMJ (Clinical research ed.)》1916,1(2888):645-647
4.
5.
Daren Lee Seth Ruffins Queenie Ng Nikhil Sane Steve Anderson Arthur Toga 《BMC bioinformatics》2010,11(1):608
Background
Digital atlases provide a common semantic and spatial coordinate system that can be leveraged to compare, contrast, and correlate data from disparate sources. As the quality and amount of biological data continues to advance and grow, searching, referencing, and comparing this data with a researcher's own data is essential. However, the integration process is cumbersome and time-consuming due to misaligned data, implicitly defined associations, and incompatible data sources. This work addressing these challenges by providing a unified and adaptable environment to accelerate the workflow to gather, align, and analyze the data. 相似文献6.
Robert Blake II Elizabeth A. Shute James Waskovsky Arthur P. Harrison JR. 《Geomicrobiology journal》2013,30(3-4):173-192
Abstract Microorganisms capable of aerobic respiration on ferrous ions are spread throughout eubacterial and archaebacterial phyla. Phylogenetically distinct organisms were shown to express spectrally distinct redox‐active biomolecules during autotrophic growth on soluble iron. A new iron‐oxidizing eubacterium, designated as strain Funis, was investigated. Strain Funis was judged to be different from other known iron‐oxidizing bacteria on the bases of comparative lipid analyses, 16S rRNA sequence analyses, and cytochrome composition studies. When grown autotrophically on ferrous ions, Funis produced conspicuous levels of a novel acid‐stable, acid‐soluble yellow cytochrome with a distinctive absorbance peak at 579 nm in the reduced state. Stopped‐flow spectrophotometric kinetic studies were conducted on respiratory chain components isolated from cell‐free extracts of Thiobacillus ferrooxidans. Experimental results were consistent with a model where the primary oxidant of ferrous ions is a highly aggregated c‐type cytochrome that then reduces the periplasmic rusticyanin. The Fe(II)‐dependent, cytochrome c‐catalyzed reduction of the rusticyanin possessed three kinetic properties in common with corresponding intact cells that respire on iron: the same anion specificity, a similar dependence of the rate on the concentration of ferrous ions, and similar rates at saturating concentrations of ferrous ions 相似文献
7.
8.
9.
10.
From six to 89 months after surgery 82 patients who had been treated by radical surgery (118 excisions) for intractable hidradenitis suppurativa were reviewed. Local recurrence rates varied greatly with the disease site, being low after axillary (3%) and perianal surgery (0%) and high after inguinoperineal (37%) and submammary (50%) excision. Recurrence results from inadequate excision or an unusually wide distribution of apocrine glands, but physical factors such as obesity, local pressure, and skin maceration played a part in a few patients. Recurrence due to inadequate surgery tended to be the most troublesome. At follow up 75 (91%) of the patients were pleased with the results of their operation. A quarter of the patients developed disease at a new anatomical site after operation. Radical surgery gives good symptomatic control of severe hidradenitis suppurativa of the axilla, inguinoperineal, and perianal regions but is less satisfactory for submammary disease. 相似文献