全文获取类型
收费全文 | 5096篇 |
免费 | 444篇 |
国内免费 | 1927篇 |
专业分类
7467篇 |
出版年
2024年 | 55篇 |
2023年 | 128篇 |
2022年 | 199篇 |
2021年 | 253篇 |
2020年 | 210篇 |
2019年 | 227篇 |
2018年 | 261篇 |
2017年 | 207篇 |
2016年 | 240篇 |
2015年 | 210篇 |
2014年 | 282篇 |
2013年 | 392篇 |
2012年 | 225篇 |
2011年 | 264篇 |
2010年 | 224篇 |
2009年 | 300篇 |
2008年 | 340篇 |
2007年 | 308篇 |
2006年 | 312篇 |
2005年 | 303篇 |
2004年 | 270篇 |
2003年 | 241篇 |
2002年 | 193篇 |
2001年 | 151篇 |
2000年 | 172篇 |
1999年 | 137篇 |
1998年 | 121篇 |
1997年 | 112篇 |
1996年 | 126篇 |
1995年 | 107篇 |
1994年 | 99篇 |
1993年 | 82篇 |
1992年 | 105篇 |
1991年 | 87篇 |
1990年 | 64篇 |
1989年 | 55篇 |
1988年 | 54篇 |
1987年 | 50篇 |
1986年 | 54篇 |
1985年 | 26篇 |
1984年 | 37篇 |
1983年 | 20篇 |
1982年 | 29篇 |
1981年 | 25篇 |
1980年 | 22篇 |
1979年 | 14篇 |
1978年 | 20篇 |
1977年 | 13篇 |
1976年 | 13篇 |
1973年 | 9篇 |
排序方式: 共有7467条查询结果,搜索用时 0 毫秒
1.
D Falk 《American journal of physical anthropology》1978,48(3):315-319
Sulcal patterns of 14 genera of Old World monkeys were analyzed from 107 endocasts. Colobines and cercopithecines differ in patterns of cerebral convolutions, and functional and evolutionary hypotheses are here proposed regarding those differences. The cercopithecine pattern seems to be the more derived since it suggests relative expansion of prefrontal, and inferior temporal integration cortices as compared to the colobine pattern. 相似文献
2.
Alicia A. Gil de Pertierra 《Zoologischer Anzeiger》2005,243(4):307-304
The surface of the tegument of the scolex and the immature proglottides of Monticellia belavistensis, M. ventrei, Nomimoscolex chubbi, and N. lopesi is described using scanning electron microscopy. Only blade-like spiniform microtriches and filiform microtriches were observed in the species studied. The types, size and density of microtriches on the apical region surface of the scolex, central cavity surface of suckers, marginal ring surface of suckers, non-adherent surface of suckers, proliferation zone surface, and immature proglottis surface were compared among these species. The distribution pattern of the microtriches was not a reliable feature to discriminate among the genera considered in this study. It varied in each of the species of Monticellia examined, and did not permit to split the heterogeneous genus Nomimoscolex. However, the microthrix pattern can be regarded as an additional diagnostic feature to distinguish among species of proteocephalideans. Further comparative research involving other species of proteocephalid taxa is needed to elucidate the systematic value of the tegumental morphology. 相似文献
3.
4.
Summary In the pars tuberalis of the hypophysis of Rana temporaria, which shows the ultrastructural characteristics of a polypeptide hormone secreting endocrine gland, seasonal changes of the ultrastructure are described. In accordance with the literature, these seasonal changes of ultrastructure are interpreted as the morphological expression of seasonal changes of endocrine activity of the pars tuberalis. 相似文献
5.
Graeme J. Inglis† 《Journal of Ecology》2000,88(1):88-99
6.
MUNENORI NOGUCHI HIROSHI INOUE TOSHIHIRO ATAGO SHOGO NAKAMURA 《The Journal of eukaryotic microbiology》1997,44(2):127-133
ABSTRACT. The effects of organic solvents on the ATPase activity and the sliding disintegration of axonemes from Chlamydomonas were investigated. The axonemal ATPase was markedly activated by methanol accompanying with marked inhibition of the sliding disintegration of axonemes. On the contrary, glycerol inhibited the ATPase activity without serious inhibition of the sliding disintegration. As far as the axonemes are not irreversibly denatured by extremely high concentration of solvents, the effects of solvents both on the ATPase and the ability of sliding are reversible. Therefore, the inhibition of sliding accompanied by the activation of ATPase is probably due to an inability to couple the hydrolysis of ATP to sliding between dynein and microtubule in the presence of methanol. The axonemal ATPase was less sensitive to vanadate inhibition after exposure to methanol. This indicates that methanol makes the dyneinADP.Pi complex unstable and increases product release. On the other hand, glycerol and ethylene glycol seem to stabilize the force generation responsible for the sliding through stabilizing the dynein.ADP.Pi complex. 相似文献
7.
8.
The ability to respond to phytochrome (Pfr, the far-red light absorbing from of phytochrome) with anthocyanin synthesis appears first in some marginal regions of the abaxial epidermis of the mustard cotyledons and from there spreads gradually over the entire tissue (transient phase). The pertinent pattern is independent of environmental influences such as light quality and nutritional culture conditions. The competence for Pfr in the epidermal cells, with regard to the initial action of Pfr (concerning anthocyanin synthesis), appears considerably earlier than the ability for actual anthocyanin synthesis. An electron microscopical study of the ultrastructural changes occurring in vacuoles and plastids of the epidermal cells during the transient phase showed that a correlation only exists between the differentiation of central cell vacuoles, originating from the aleurone vacuoles, and the appearance of the ability to accumulate anthocyanin. It is suggested that the formation of a central cell vacuole is a prerequisite for anthocyanin accumulation in the epidermal cells of the mustard seedling cotyledons.Abbreviations Pr, Pfr
red and far-red absorbing forms of phytochrome
- HS
Hoagland's nutrient solution 相似文献
9.
10.
Anna Maria Tagliasacchi Laura Maria Costantina Forino Manuela Frediani Silvana Avanzi 《Protoplasma》1983,115(2-3):95-103
Summary The pattern of DNA and RNA puffs in pair VII of polytene chromosomes has been investigated in the suspensor ofPhaseolus coccineus during early embryo development. The pattern of3H-TdR and3H-U incorporation has been also detected. Collected data indicate that: 1. both heterochromatic regions, p11 and q(111+112), of chromosome pair VII, organize large DNA puffs; 2. DNA puffs of both regions are specific of different embryo differentiation steps; 3. a seasonal influence on the DNA puffing seems also to be present, as demonstrated by the comparison of the results collected in two different crops; 4. the incorporation experiment by3H-TdR evidences that not all DNA puffs show clustered labeling; 5. the RNA puffing of the two regions seems also to be specific of determined embryo stages. 相似文献