全文获取类型
收费全文 | 2751篇 |
免费 | 165篇 |
国内免费 | 1篇 |
出版年
2023年 | 15篇 |
2022年 | 19篇 |
2021年 | 77篇 |
2020年 | 36篇 |
2019年 | 53篇 |
2018年 | 45篇 |
2017年 | 47篇 |
2016年 | 68篇 |
2015年 | 131篇 |
2014年 | 131篇 |
2013年 | 186篇 |
2012年 | 230篇 |
2011年 | 200篇 |
2010年 | 141篇 |
2009年 | 112篇 |
2008年 | 145篇 |
2007年 | 152篇 |
2006年 | 144篇 |
2005年 | 142篇 |
2004年 | 119篇 |
2003年 | 126篇 |
2002年 | 105篇 |
2001年 | 20篇 |
2000年 | 24篇 |
1999年 | 29篇 |
1998年 | 21篇 |
1997年 | 27篇 |
1996年 | 16篇 |
1995年 | 16篇 |
1994年 | 15篇 |
1993年 | 10篇 |
1992年 | 19篇 |
1991年 | 13篇 |
1990年 | 11篇 |
1989年 | 16篇 |
1987年 | 11篇 |
1986年 | 10篇 |
1985年 | 10篇 |
1984年 | 26篇 |
1983年 | 15篇 |
1982年 | 19篇 |
1981年 | 14篇 |
1979年 | 9篇 |
1978年 | 7篇 |
1977年 | 7篇 |
1974年 | 7篇 |
1973年 | 10篇 |
1967年 | 7篇 |
1965年 | 8篇 |
1964年 | 6篇 |
排序方式: 共有2917条查询结果,搜索用时 31 毫秒
1.
2.
3.
4.
Stoichiometric differences in DNA molecules containing the atpA gene suggest mechanisms for the generation of mitochondrial genome diversity in maize 总被引:14,自引:1,他引:13 下载免费PDF全文
Four genomic arrangements of the maize mitochondrial atpA gene (encoding the α subunit of the F1 ATPase), have been characterized. Most N (fertile) and S (male-sterile) cytoplasms contain two atpA arrangements of equal abundance. Prolonged exposure of blots of maize mitochondrial DNA probed with atpA-specific sequences show that cytoplasms previously reported to lack one of the atpA arrangements do contain the second arrangement but at low levels. Similarly, restriction fragments containing the atpA gene previously thought unique to male-sterile S and T cytoplasms are present in low abundance in fertile cytoplasms. These observations suggest that fertile and male-sterile cytoplasms of maize may be more closely related than previously thought, and suggest possible mechanisms to explain the observed mitochondrial genome diversity. 相似文献
5.
Summary Axillary bud expiants from South Pacific (Solomon Islands) taro, Colocasia esculenta var. esculenta cv. Akalomamale (Araceae) cultured on a modified Murashige-Skoog medium containing 1 mg NAA 1–1 and TE formed callus and produced multiple plantlets. Explants died if NAA was present at levels lower than 0.1 mg 1–1. BA was not required and may have been inhibitory. Plantlets developed faster and became larger following transfer to a hormone-free medium two weeks after the start of culture. Fully grown plants were established in a potting mix and are growing well in a greenhouse.Abbreviations BA
benzyladenine
- BM
basal medium
- Ca
Colocasia esculenta var. antiquorum
- Ce
Colocasia esculenta var. esculenta
- Ck
cytokinin(s)
- CW
coconut water
- HSMSM
half strength Murashige Skoog macroelements
- HSMS
half strength Murashige and Skoog medium
- IM
initial medium(ia)
- MS
Murashige and Skoog medium
- NAA
naphthaleneacetic acid
- SM
second medium
- TE
taro corm extract
- UCI
University of California, Irvine 相似文献
6.
7.
In a new case of interstitial del(2q), measurements of ribulose 5-phosphate 3-epimerase activity suggested that the locus for this enzyme might be localized to the subregion 2q32q33.3. 相似文献
8.
Expression of c-myc protooncogene in rat lens cells during development,maturation and reversal of galactose cataracts 总被引:2,自引:0,他引:2
Yi Wen Songtao Shu Nalin J. Unakar Isaac Bekhor 《Molecular and cellular biochemistry》1992,112(1):73-79
It is well established that normal patterns of epithelial cell proliferation and metabolism, and of fiber cell differentiation and maturation are essential for the maintenance of transparency in the ocular lens. Several factors, including exposure to high levels of sugars, have been known to result in the compromise of lens transparency. For example, initiation of lens cell damage by galactose induces lens epithelial cells to proliferate. Elevated levels of c-myc mRNA have usually been correlated with rapid cell growth and increased entry of cells into the S phase. Therefore, changes in c-myc mRNA levels may provide an early indication of the stimulation of lens epithelial cells to proliferate and differentiate, which has been postulated to be an early and important event in response to lens cell injury by galactose. By Northern blot hybridization analysis we quantitated c-myc mRNA levels in the lens capsule epithelia of rats (1) exposed to galactose, and (2) undergoing a partial recovery from the galactose-induced cell damage. At the onset of lens cell damage, we find c-myc mRNA to elevate to 6-fold by 24 hr, and by 48 hr decreases to about 3-fold the normal levels. During recovery, c-myc mRNA continues to be expressed at high levels approaching a 10-fold increase by day 12, then decreasing to levels of about 8-fold the control by day 30. The 24 h transitory elevation in c-myc mRNA in lens epithelial cells is in accord with our previous observations on the 24 h increase in MP26, crystallin and aldose reductase mRNAs following a high influx of galactose. Therefore, the elevation in c-myc mRNA as well suggest that galactose appears to cause lens cells to undergo an early transitory period of gene induction following the exposure of lens cells to galactose. 相似文献
9.
Milzani Aldo; Carrera Paolo; Bergna Giovanni; Colombo Roberto 《Bioinformatics (Oxford, England)》1986,2(1):19-22
A program in BASIC is described which allows accurate quantificationof some numerical parameters that can be objectively correlatedto biological indexes in sigmoid biological events. Attentionwas focused on the polymerization process of actin (a muscleprotein with a mol. wt of 42 000 daltons) studied as the variationin the OD360 index with time. The experimental points, if plotted,can be well approximated by a rational function of the typeOD360 = f(t), which passes through the origin and can be representedgraphically by a sigmoid curve. The program was very helpfulin comparing the experimental curves and in analysing significantparameters, such as maximum velocity and asymptote, that characterizethese curves and whose interpretation would otherwise be purelysubjective.
Received on July 11, 1985; accepted on January 13, 1986 相似文献
10.
An unusual Rhodotorula isolated from decayed wood of Nothofagus obliqua (Mirb.) Blume is described and illustrated. This species differs from all accepted Rhodotorula species (1–7, 10) to warrant its establishment as a new species, Rhodotorula nothofagi sp. nov.Postgraduate student from the Instituto de Ecología y de Evolución, Universidad Austral de Chile, Valdivia. 相似文献