全文获取类型
收费全文 | 2902篇 |
免费 | 167篇 |
国内免费 | 1篇 |
专业分类
3070篇 |
出版年
2022年 | 15篇 |
2021年 | 38篇 |
2020年 | 16篇 |
2019年 | 17篇 |
2018年 | 32篇 |
2017年 | 29篇 |
2016年 | 51篇 |
2015年 | 122篇 |
2014年 | 133篇 |
2013年 | 193篇 |
2012年 | 174篇 |
2011年 | 187篇 |
2010年 | 116篇 |
2009年 | 138篇 |
2008年 | 177篇 |
2007年 | 173篇 |
2006年 | 201篇 |
2005年 | 197篇 |
2004年 | 226篇 |
2003年 | 185篇 |
2002年 | 168篇 |
2001年 | 37篇 |
2000年 | 29篇 |
1999年 | 48篇 |
1998年 | 38篇 |
1997年 | 31篇 |
1996年 | 22篇 |
1995年 | 24篇 |
1994年 | 21篇 |
1993年 | 20篇 |
1992年 | 14篇 |
1991年 | 13篇 |
1990年 | 15篇 |
1989年 | 10篇 |
1988年 | 18篇 |
1987年 | 7篇 |
1986年 | 7篇 |
1985年 | 11篇 |
1984年 | 11篇 |
1983年 | 9篇 |
1982年 | 14篇 |
1981年 | 17篇 |
1979年 | 12篇 |
1978年 | 9篇 |
1977年 | 5篇 |
1976年 | 9篇 |
1972年 | 4篇 |
1971年 | 3篇 |
1969年 | 4篇 |
1968年 | 3篇 |
排序方式: 共有3070条查询结果,搜索用时 0 毫秒
11.
12.
Immigration of the brown planthopper, Nilaparvata lugens, exhibiting various responses to density in relation to wing morphism 总被引:6,自引:0,他引:6
Considerable inherent variations in the relation between macropterous and brachypterous wing forms, and nymphal density were found in field populations of the brown planthopper, Nilaparvata lugens Stål (Homoptera: Delphacidae), collected from various locations in Japan. When compared under uniform laboratory rearing conditions, most of the female populations exhibited higher ratios of macropters with increasing nymphal density, but some showed extremely high proportion of brachypters and the others were highly macropterous, over broad ranges of density. These results indicate the possibility that the planthoppers in Japan, which are known not to persist in winter, are derived from different migration sources.About ten generations of successive selection for brachyptery from a population showing usual density-dependent wing morphism generated populations similar to highly brachypterous ones mentioned above. Genetic analysis of the inheritance of wing morphism revealed that brachyptery in the females was controlled by a single pair of dominant alleles. However, in the males wing forms did not segregate so clearly in the crossing experiments. This suggests that wing morphism in N. lugens in under sex-limited inheritance.
Einwanderung von Nilaparvata lugens mit unterscheidlicher Reaktion auf Populationsdischte bei der Flügelausbildung
Zusammenfassung In Feldpopulationen von Nilaparvata lugens Stål., welche in verschiedenen Regionen Japans gesammelt wurden, bestand in der Beziehung zwischen makropteren bzw. brachypteren Flügelformen und der Larvendichte eine beträchtliche Variation. Unter einheitlichen Zuchtbedingungen im Laboratorium stieg der Makropterenanteil bei den meisten Weibchenpopulationen mit steigender Temperatur; bei einigen Populationen hingegen war entweder der Brachypterenanteil oder der Makropterenanteil extrem hoch und zwar über weite Dichtebereiche. Dies deutet auf die Möglichkeit hin, dass die Zikade in Japan, wo sie bekanntlich nicht überwintert, jeweils aus verschiedenen Quellen einwandert.Wenn eine Population mit der üblichen dichteabhängigen Flügelausbildung 10 Generationen lang auf Brachypterie selektioniert wurde, entstanden Populationen, die den erwähnten hochbrachypteren Populationen aus dem Feld glichen. Die genetische Analyse der Vererbung der Brachypterie ergab, dass bei Weibchen ein einzelnes dominantes Allel verantwortlich ist. Bei Männchen dagegen trennten sich bei Kreuzungsexperimenten die Flügelformen nicht so klar. Dies deuted auf Unterschiede zwischen den Geschlechtern bei der Vererbung der Flügelformen.相似文献
13.
Toru Miki 《Ichthyological Research》1985,32(2):137-142
Specimens of a new genus and species of the stichaeid fish,Leptostichaeus pumilus, were collected from the Okhotsk Sea off Hokkaido in Japan. The present new genus and species clearly differs from all the other genera and species of the stichaeid fishes in the following characters: 3 or 4 pectoral fin rays; 10 or fewer caudal principal rays; 79–82 dorsal spines; no pelvic fin; last interneural spine supporting a single dorsal spine; infraorbital, occipital and lateral line canals absent; moderate size of dorsal spine shorter than eye diameter; membranes of dorsal and anal fins widely connected with caudal fin; a large black spot divided by a yellow band present just above gill cover. 相似文献
14.
15.
16.
Nakazawa Miki; Kakihana Junko; Hisabori Toru; Manabe Katsushi 《Plant & cell physiology》1990,31(6):789-796
Procedures for the purification of native phytochrome from etiolatedpea seedlings without the use of immuno-purification techniquesare described. Phytochrome (in the PFR form) was purified bypolyethyleneglycol fractionation, adsorption to pentyl agaroseand batch elution, chromatography on DEAE-Sepharose, adsorptionto phenyl Toyopearl and batch elution, and chromatography onRed Toyopearl. The resulting phytochrome had specific absorbanceratios (SAR = A666/A280 of PR) that ranged from 0.55 to 0.6.The subsequent chromatography on Sephacryl S-300 yielded verypure phytochrome with a SAR of 0.98. PR and PFR peaks in thedifference spectrum of the phytochrome were centered at 665and 730 nm, respectively. The spectral change ratio (Ar/Afr)of the difference spectrum was unchanged after the chromatographyon phenyl Toyopearl, and the value was 1.051.08, indicatingthat the spectral properties of this preparation were intact.The absorption spectra indicated that the peak absorbance ofPFR was at 728730 nm and that of PR was at 666667nm. These peak positions were essentially same as those obtainedwith the undegraded oat phytochrome. Incubation of the samplepurified on Sephacryl S-300 at 25?C for 5 h in either the PRor PFR form did not result in degradation of the molecule. Therate of dark reversion of PFR observed with the purified peaphytochrome was similar to that observed in vivo. The additionof dithionite had no effect on the reversion rate.
2Present address: Fuji-Gotenba, Research Lab. of Chugai PharmaceuticalCo. Ltd., Gotenba, Shizuoka, 412 Japan (Received February 22, 1990; Accepted May 28, 1990) 相似文献
17.
18.
19.
20.