全文获取类型
收费全文 | 1947篇 |
免费 | 123篇 |
国内免费 | 2篇 |
出版年
2023年 | 17篇 |
2022年 | 14篇 |
2021年 | 49篇 |
2020年 | 27篇 |
2019年 | 34篇 |
2018年 | 73篇 |
2017年 | 60篇 |
2016年 | 76篇 |
2015年 | 86篇 |
2014年 | 103篇 |
2013年 | 139篇 |
2012年 | 114篇 |
2011年 | 114篇 |
2010年 | 92篇 |
2009年 | 65篇 |
2008年 | 57篇 |
2007年 | 58篇 |
2006年 | 74篇 |
2005年 | 60篇 |
2004年 | 43篇 |
2003年 | 42篇 |
2002年 | 48篇 |
2001年 | 17篇 |
2000年 | 29篇 |
1999年 | 20篇 |
1998年 | 28篇 |
1997年 | 12篇 |
1996年 | 17篇 |
1995年 | 11篇 |
1994年 | 20篇 |
1993年 | 14篇 |
1992年 | 15篇 |
1991年 | 21篇 |
1988年 | 10篇 |
1987年 | 17篇 |
1985年 | 12篇 |
1984年 | 11篇 |
1982年 | 14篇 |
1981年 | 18篇 |
1980年 | 14篇 |
1979年 | 15篇 |
1978年 | 19篇 |
1977年 | 14篇 |
1976年 | 20篇 |
1975年 | 19篇 |
1974年 | 19篇 |
1973年 | 10篇 |
1972年 | 12篇 |
1971年 | 9篇 |
1969年 | 11篇 |
排序方式: 共有2072条查询结果,搜索用时 15 毫秒
1.
2.
3.
A systematic study of transformation reactions of Actinomycetes with respect to the progesterone molecule was undertaken. The results obtained, i.e. the types of transformation reactions in different actinomycete species, were evaluated from the point of view of taxonomy. The actinomycetes tested were divided according to the transformation types into three groups: (1) a group of species transforming progesterone in the 16α-position; (2) a group of species transforming progesterone in the β-position; (3) a group of species in which no capacity to transform progesterone into another steroid derivative was established. From the point of view of Actinomycete classification the transformation reactions on the steroid molecule fulfil all the requirements of taxonomic features of Actinomycetes. They appear to be specific properties, independent of strictly cultivation conditions and common to all the strains of individual actinomycete species tested. 相似文献
4.
Dr. Lad Čelakovský 《Plant Systematics and Evolution》1890,40(8):287-297
Ohne Zusammenfassung 相似文献
5.
Laid Douidah Lieven De Zutter Filip Van Nieuwerburgh Dieter Deforce Hanne Ingmer Olivier Vandenberg Anne-Marie Van den Abeele Kurt Houf 《PloS one》2014,9(1)
In this study, we report the screening of four Arcobacter species for the presence of small and large plasmids. Plasmids were present in 9.9% of the 273 examined strains. One Arcobacter cryaerophilus and four Arcobacter butzleri plasmids were selected for further sequencing. The size of three small plasmids isolated from A. butzleri and the one from A. cryaerophilus strains ranged between 4.8 and 5.1 kb, and the size of the large plasmid, isolated from A. butzleri, was 27.4 kbp. The G+C content of all plasmids ranged between 25.4% and 26.2%. A total of 95% of the large plasmid sequence represents coding information, which contrasts to the 20 to 30% for the small plasmids. Some of the open reading frames showed a high homology to putative conserved domains found in other related organisms, such as replication, mobilization and genes involved in type IV secretion system. The large plasmid carried 35 coding sequences, including seven genes in a contiguous region of 11.6 kbp that encodes an orthologous type IV secretion system found in the Wolinella succinogenes genome, Helicobacter pylori and Campylobacter jejuni plasmids, which makes this plasmid interesting for further exploration. 相似文献
6.
Dr. Lad Čelakovský 《Plant Systematics and Evolution》1872,22(9):283-285
Ohne Zusammenfassung 相似文献
7.
Summary A support based on pyrogeneous silicon dioxide of particle size 0.01 to 0.1/um, modified by 3-(amino)propyltriethoxysilane and activated by glutaraldehyde was employed for the immobilization of concanavalin A, immunoglobulins, basic pancreatic trypsin inhibitor, and chymotrypsin. Its binding capacity is comparable with that of porous supports while the biological activity of the proteins immobilized is retained. Nonspecific adsorption of these proteins to the support is low compared to its binding capacity. 相似文献
8.
Twelve metronidazole-resistant and twelve metronidazole-susceptible strains ofTrichomonas vaginalis were tested for the presence of dsRNA. Three resistant and five susceptible strains were found to contain dsRNA which indicated
that metronidazole resistance does not correlate with the absence of dsRNA. Electron microscopy showed the homogenates of
all dsRNA -positive strains to contain virus-like particles 32 –38 nm in diameter, while no such particles were found in the
dsRNA-negative strains. A mutual relationship between the dsRNA and virus-like particles seems to exist.
After this paper had been accepted for publication the occurrence of virus-like particles in dsRNA-positive trichomonads was
reported by others (Wang A.L., Wang C.C.: The double stranded RNA inTrichomonas vaginalis may originate from virus-like particles.Proc. Nat. Acad. Sci. USA
83, 7956–7961, 1986). 相似文献
9.
Densities of Drosera intermedia were low in two studied habitats (10–25 ramets m−1 ), a path through a wet heath (short inundation in spring, low soil moisture in summer) and a pool edge (longlasting inundation, high soil moisture in summer). The low densities could be explained by the observed low recruitment and high adult mortality.
The low recruitment resulted from: (1) a high first year mortality of the large number of seedlings that emerged each year in the path population, caused by summer drought and cover with algae after heavy rainfall; (2) the absence in two years out of three of seedling emergence at the pool edge, due to the longlasting inundation. In neither population any seedlings survived to flower; (3) low vegetative reproduction rate.
Adult mortality during the growing season was caused by drought, which did not occur at the pool edge. Rapid senescence in autumn, caused by summer drought on the path and by a rapid submersion after heavy rainfall at the pool edge, was associated with a high winter mortality. 相似文献
The low recruitment resulted from: (1) a high first year mortality of the large number of seedlings that emerged each year in the path population, caused by summer drought and cover with algae after heavy rainfall; (2) the absence in two years out of three of seedling emergence at the pool edge, due to the longlasting inundation. In neither population any seedlings survived to flower; (3) low vegetative reproduction rate.
Adult mortality during the growing season was caused by drought, which did not occur at the pool edge. Rapid senescence in autumn, caused by summer drought on the path and by a rapid submersion after heavy rainfall at the pool edge, was associated with a high winter mortality. 相似文献
10.
J. Čatský D. K. Velichkov Jana Pospísilová Jarmila Solárová Ingrid Tichá 《Biologia Plantarum》1987,29(5):355-364
The carbon balances of whole, 21-d old French bean plants (Phaseolus vulgaris L.) grown in standard nutrient solution (1K) and its modifications without (OK) or surplus (2K) potassium were calculated
from the daily photosynthetic carbon inputs of individual leaves, and the daily respiratory carbon losses by individual leaves,
stalks and petioles, and roots. Under the three K concentrations, maximum net photosynthetic rates (Pn) were found in the 2nd or in the 3rd trifoliate leaves, maximum respiratory rates (Rd) in the youngest, 4th trifoliate leaves; the Pn/Rd ratio decreased with leaf age. In all leaves of 2K plants, leaf dry masses and thicknesses, Pn, Pn/Pd ratios, and stomatal and intracellular conductances were lower than in OK and IK plants. Daily whole-plant net carbon gain
was highest in IK plants, whereas in OK and 2K plants it was 98.0 and 81.3 % of IK, respectively. Similar values were found
in the parameters of growth analysis, namely in net assimilation rates and relative growth rates.
No differences were found in water potential (Ψ
w
) or water saturation deficit (Wsat) in the OK, 1K and 2K plants sufficiently supplied with water or during wilting and resaturation. The decrease in Ψw to −0.97 MPa was associated with a 19.9 %, 31.4 % and 23.4 % decrease in Pn of OK, 1K and 2K plants, respectively, but no effect on Rd was found. In the three variants, the short-time effect of mild water stress was fully reversible. 相似文献