全文获取类型
收费全文 | 2516篇 |
免费 | 245篇 |
国内免费 | 1篇 |
出版年
2023年 | 12篇 |
2022年 | 15篇 |
2021年 | 46篇 |
2020年 | 28篇 |
2019年 | 31篇 |
2018年 | 46篇 |
2017年 | 48篇 |
2016年 | 80篇 |
2015年 | 154篇 |
2014年 | 145篇 |
2013年 | 187篇 |
2012年 | 230篇 |
2011年 | 221篇 |
2010年 | 128篇 |
2009年 | 135篇 |
2008年 | 164篇 |
2007年 | 164篇 |
2006年 | 150篇 |
2005年 | 129篇 |
2004年 | 108篇 |
2003年 | 86篇 |
2002年 | 88篇 |
2001年 | 25篇 |
2000年 | 11篇 |
1999年 | 38篇 |
1998年 | 35篇 |
1997年 | 22篇 |
1996年 | 13篇 |
1995年 | 16篇 |
1994年 | 21篇 |
1993年 | 16篇 |
1992年 | 9篇 |
1991年 | 12篇 |
1990年 | 5篇 |
1989年 | 11篇 |
1988年 | 5篇 |
1987年 | 6篇 |
1986年 | 9篇 |
1985年 | 6篇 |
1984年 | 7篇 |
1983年 | 7篇 |
1982年 | 5篇 |
1981年 | 8篇 |
1980年 | 12篇 |
1977年 | 7篇 |
1976年 | 5篇 |
1974年 | 6篇 |
1973年 | 5篇 |
1970年 | 6篇 |
1969年 | 4篇 |
排序方式: 共有2762条查询结果,搜索用时 31 毫秒
21.
Josefa Alamillo Concepción Almoguera Dorothea Bartels Juan Jordano 《Plant molecular biology》1995,29(5):1093-1099
Using antibodies raised against two sunflower small heat shock proteins (sHSPs), we have detected immunologically related proteins in unstressed vegetative tissues from the resurrection plant Craterostigma plantagineum. In whole plants, further accumulation of these polypeptides was induced by heat-shock or water-stress. In desiccation-intolerant Craterostigma callus tissue, we failed to detect sHSP-related polypeptides, but their expression, and the concurrent acquisition of desiccation tolerance was induced by exogenous abscisic acid (ABA) treatment. In untressed plants, the cross-reacting polypeptides were abundant in the roots and lower part of the shoots, where they showed homogeneous tissue-distributions. This constitutive expression is novel for vegetative tissues of higher plants, and resembles the expression patterns of sHSPs in desiccation-tolerant zygotic embryos and germinating seeds.J.A. and C.A. contributed equally to this work and are both considered to be first author 相似文献
22.
Gas-vesicle (Vac) synthesis in Halobacterium salinarium PHH1 involves the expression of the p-vac region consisting of 14 different gvp genes that are arranged in two clusters: p-gvpACNO and, oppositely oriented, p-gvpDEFGHIJKLM. The latter cluster of genes is transcribed as two units: p-gvpDE and p-gvpF–M. The 5′-terminus of the p-gvpF–M mRMA was located 169 nucleotides upstream of p-gvpF within p-gvpE. The p-gvpG and p-gvpK gene was expressed in Escherichia coli and antibodies to proteins obtained were raised in rabbits. Both proteins could be detected in halobacterial cell lysates; in gas-vesicle preparations, however, neither GvpG nor GvpK could be found. The requirement for single p-gvp gene expression for gas-vesicle synthesis was determined by transformation experiments using the Vac? species Haloferax volcanii as recipient. Construct ΔA containing all p-gvp genes except for p-gvpA, encoding the major gas-vesicle structural protein, produced Vac? transformants, but the addition of p-gvpA on a second vector restored gas-vesicle synthesis to wild-type level (Vac++). Similarly, double transformants containing p-gvpD–M plus p-gvpACNO, or p-gvpG–M (fused to the promoter of the halobacterial ferredoxin gene for expression) plus p-gvpFED–ACNO were Vac++. Transformants containing the p-vac region either lacking gvpA, gvpF, or gvpGHI were Vac?, indicating the absolute requirement of these gvp genes (or at least one in the case of gvpGHI) for gas-vesicle formation. Double transformants containing the constructs p-gvpF–M plus p-gvpACNO (ΔDE) accumulated gas vesicles (Vac+) but synthesized fewer than the wild type, showing that the p-gvpDE genes are not necessary for gas-vesicle assembly. A repressor function affecting the synthesis of the p-gvpF–M mRNA could be suggested for p-gvpD and the 5′- region of its mRNA. 相似文献
23.
Lorraine Flaherty Linda Cantor Debra Zimmerman Dorothea Bennett 《Developmental biology》1977,59(2):237-240
Cell surface antigens of normal and anemic () mouse erythroid cells have been examined in cytotoxicity assays with two rat antisera. When tested on fetal liver cells, a rat anti-erythroblast serum recognized antigen(s) present on erythroid cells early in development, while rat anti-adult red blood cell serum recognized antigen(s) present on mature erythroid cells. Each of these sera had different activity on normal (+/+ or ) as compared to anemic () erythroid cells. 相似文献
24.
25.
Ferdinand Bohlmann Karl-Heinz Knoll Christa Zdero Pradip Kumar Mahanta Michael Grenz Albert Suwita Dorothea Ehlers Ngo Le Van Wolf-Rainer Abraham Arvind Anant Natu 《Phytochemistry》1977,16(7):965-985
Investigation of about 50 Senecio species has afforded many new substances, in addition to known compounds. Present in these plants are 23 fura 相似文献
26.
Serological studies relating F9 antigen of embryonal carcinoma cells to
at the murineT/t complex have been extended and confirm that only the lethal haplotype t12- and none of the other five lethal haplotypes-affects the quantitative expression of F9 antigen on sperm. Cytotoxicity tests on preimplantation embryos show that t12 homozygotes are less susceptible to antiF9 serum than tw5 homozygotes, and that using specific antimutant haplotype antisera prepared against sperm, t12 antigen is detectable on morulae, whereas tw5 antigen is not. 相似文献
27.
Based on SEM examinations of some 1600 species of monocotyledons out of 61 families the characteristics of their epicuticular waxes are described in this preliminary paper and illustrated by 20 SEM micrographs. Four basic types of waxes are recognized. Two of them occur throughout the monocotyledonous and dicotyledonous orders of angiosperms; two others are of high systematic significance and restricted to particular orders of the monocotyledons: The “Convallaria-Type” is characterized by fine wax platelets with parallel orientation, forming a pattern around the stomata reminiscent of electromagnetic field lines. This type is restricted to the three liliiflorous ordersAsparagales, Liliales, andBurmanniales. The “Strelitzia-Type” is characterized by massive compound wax rodlets; it is restricted to the superordersAreciflorae, Commeliniflorae, Zingiberiflorae, plus the two liliiflorous ordersBromeliales andVelloziales. The data are compared with the classifications ofDahlgren & Clifford (1982); they tentatively indicate the exclusion ofBromeliales, Velloziales, andTyphales from theLiliiflorae. 相似文献
28.
29.
30.
A series of recessive mutations which arrest embryonic development are located within the T/t region of chromosome 17 in the mouse. To assess whether these mutations cause death in specific differentiating cells or in all cells of the embryo, we removed the embryonic cells from normal developmental constraints and attempted to grow them ectopically in vivo and in vitro. We have succeeded in producing teratomas and teratocarcinomas by transplantation of inner cell masses from blastocysts of and genotypes. The ability of embryonic cells to grow as tumors was not affected by their genotype; 7 of the 17 tumors were homozygous for tw12, 7 were heterozygous, and 3 could not be analyzed. Virtually all the tumors of both genotypes contained derivatives of all three germ layers. Neuroepithelial and mature nervous tissue was present in all homozygous tumors and all except one heterozygous tumor. However, no cartilage or bone was found in 5 of 5 tw12 homozygous tumors, while both tissues were present in 3 of 4 tw12 heterozygous tumors. This observation is compatible with the abnormalities characteristic of embryos, which show very localized effects in nervous tissue and more general effects on bone and cartilage formation. Cells derived from homozygous tumors were capable of at least limited growth in culture and a cell line has been derived from one of them. The p63/6.9a marker protein was used to determine the presence of the tw12 haplotype in the tumor and cultured cells. We conclude that the lethality associated with the tw12 haplotype is due to lethality of specific cells, and not all cell types. 相似文献