全文获取类型
收费全文 | 865篇 |
免费 | 71篇 |
专业分类
936篇 |
出版年
2022年 | 12篇 |
2021年 | 14篇 |
2020年 | 6篇 |
2018年 | 6篇 |
2017年 | 5篇 |
2016年 | 17篇 |
2015年 | 29篇 |
2014年 | 37篇 |
2013年 | 46篇 |
2012年 | 52篇 |
2011年 | 55篇 |
2010年 | 28篇 |
2009年 | 31篇 |
2008年 | 27篇 |
2007年 | 39篇 |
2006年 | 55篇 |
2005年 | 31篇 |
2004年 | 39篇 |
2003年 | 26篇 |
2002年 | 31篇 |
2001年 | 16篇 |
2000年 | 14篇 |
1999年 | 11篇 |
1998年 | 7篇 |
1997年 | 14篇 |
1996年 | 7篇 |
1995年 | 5篇 |
1994年 | 8篇 |
1992年 | 11篇 |
1991年 | 10篇 |
1990年 | 10篇 |
1989年 | 9篇 |
1988年 | 6篇 |
1986年 | 11篇 |
1985年 | 10篇 |
1984年 | 6篇 |
1983年 | 6篇 |
1982年 | 6篇 |
1981年 | 11篇 |
1980年 | 8篇 |
1979年 | 5篇 |
1978年 | 6篇 |
1977年 | 10篇 |
1976年 | 5篇 |
1975年 | 5篇 |
1973年 | 12篇 |
1970年 | 5篇 |
1968年 | 5篇 |
1965年 | 5篇 |
1961年 | 6篇 |
排序方式: 共有936条查询结果,搜索用时 0 毫秒
1.
2.
3.
4.
5.
6.
Ramon J. Rhine Guy W. Norton Gail M. Wynn Roger D. Wynn 《International journal of primatology》1989,10(4):319-342
Focal-animal feeding data obtained from 64 adult baboons during a 3-year period were used together with equivalent data from
46 infants to evaluate hypotheses predicting selection for a birth peak and to study the baboon’s eclectic/selective feeding
adaptation, with emphasis on differential feeding by sex, developmental trends, and seasonal use of food classes (fruit, leaf,
flower, grass, etc.). The findings suggest that feeding conditions are better in the wet season than in the dry season. Despite
large sexual dimorphism, estimates of total amounts eaten were virtually identical for males and females. Infants used all
of the same plant-food classes as adults, but proportional differences occurred for some food classes in amounts eaten. Foods
eaten proportionately less by infants were probably harder for them to obtain and process or were chosen through inexperience
or for exploration. There was considerable between-year variation in amounts of food classes eaten, but the within-year standard
deviations were similar, as were also the mean amounts eaten per year. An eclectic/selective feeding adaptation has the advantage
of permitting long-run acquisition of adequate nutrition within a context of high feeding variation from season to season
and year to year. Mixed results were obtained from hypotheses about selection for a birth peak. Although a peak occurred in
the early dry season, this was not the optimal time of birth for survival. Survival was highest for individuals born in the
late wet season, when the availability and probably the quality of food for lactating mothers were greatest. 相似文献
7.
D-amino acid oxidase is a widely distributed peroxisomal enzyme whose principal natural substrates are still unknown. Thiazolidine carboxylates, their derivatives and relatives, and the intermediates in their metabolism are among the more plausible substrate candidates. Using a cytochemical procedure, we have explored the distribution of peroxide-generating enzymatic activity against two thiazolidine carboxylates. We find that these compounds are effective substrates for peroxisomal oxidation in a variety of tissues that contain peroxisomal D-amino acid oxidase. Reaction was seen in the "classical" peroxisomes of rat liver and kidney, the peroxisomes of the fat body of firefly and of Drosophila and the peroxisomes of frog retina. Interestingly, both with the thiazolidine compounds and with more traditional D-amino acid oxidase substrates, the fireflies' photocyte granules, which are peroxisomes, lack activity. 相似文献
8.
Interaction of plastocyanin with photosystem I: a chemical cross-linking study of the polypeptide that binds plastocyanin 总被引:10,自引:0,他引:10
Plastocyanin has been covalently cross-linked to photosystem I (PSI) by using a water-soluble cross-linker, N-ethyl-3-[3-(dimethylamino)propyl]carbodiimide. The cross-linking reaction is light stimulated and results in the disappearance of a single 19-kDa subunit of PSI with the formation of a new protein-staining component of 31 kDa. The new product at 31 kDa reacts with both plastocyanin and 19-kDa subunit antibodies. Carboxyl group modified plastocyanin does not form a cross-linked product with PSI, implying that the negatively charged surface-exposed groups on plastocyanin are necessary to stabilize binding. These results demonstrate a specific interaction of plastocyanin with PSI and further implicate a specific protein to which plastocyanin binds to facilitate electron transfer to the P700 reaction center. 相似文献
9.
M Wynn G Stevens D B Knaff R A Holwerda 《Archives of biochemistry and biophysics》1983,223(2):662-666
3,4-Dihydroxyphenylalanine (DOPA) is not a preferred substrate of Rhus vernicifera laccase, as rate constants for the anaerobic reduction of the type 1 cupric atom by L-DOPA (6.3 X 10(1) M-1 s-1), D-DOPA (2.6 X 10(1) M-1 s-1), and L-DOPA methyl ester (2.6 X 10(1) M-1 s-1) are considerably smaller than k1 (catechol) (7 X 10(2) M-1 s-1) and rate constants characteristic of numerous other nonphysiological organic substrates (25 degrees C, pH 7.0, I = 0.5 M). The reactions of DOPA derivatives with laccase are unique, however, in that a two-term rate law pertains: kobsd = k0 + k1[phenol]; k0(L-DOPA) = 7 X 10(-2) s-1. The reactivities of other catechol derivatives (pyrogallol, gallic acid, and methyl gallate) with laccase type 1 copper were also examined. 相似文献
10.