全文获取类型
收费全文 | 2723篇 |
免费 | 352篇 |
国内免费 | 380篇 |
出版年
2024年 | 5篇 |
2023年 | 43篇 |
2022年 | 44篇 |
2021年 | 64篇 |
2020年 | 120篇 |
2019年 | 157篇 |
2018年 | 148篇 |
2017年 | 137篇 |
2016年 | 147篇 |
2015年 | 128篇 |
2014年 | 124篇 |
2013年 | 196篇 |
2012年 | 105篇 |
2011年 | 131篇 |
2010年 | 86篇 |
2009年 | 111篇 |
2008年 | 111篇 |
2007年 | 118篇 |
2006年 | 121篇 |
2005年 | 125篇 |
2004年 | 91篇 |
2003年 | 117篇 |
2002年 | 78篇 |
2001年 | 73篇 |
2000年 | 82篇 |
1999年 | 53篇 |
1998年 | 60篇 |
1997年 | 51篇 |
1996年 | 33篇 |
1995年 | 42篇 |
1994年 | 60篇 |
1993年 | 61篇 |
1992年 | 51篇 |
1991年 | 50篇 |
1990年 | 43篇 |
1989年 | 30篇 |
1988年 | 36篇 |
1987年 | 32篇 |
1986年 | 20篇 |
1985年 | 34篇 |
1984年 | 24篇 |
1983年 | 9篇 |
1982年 | 19篇 |
1981年 | 21篇 |
1980年 | 17篇 |
1979年 | 10篇 |
1978年 | 7篇 |
1977年 | 8篇 |
1976年 | 11篇 |
1973年 | 3篇 |
排序方式: 共有3455条查询结果,搜索用时 78 毫秒
61.
Growth of Ectopic Dendrites on Cortical Pyramidal Neurons in Neuronal Storage Diseases Correlates with Abnormal Accumulation of GM2 Ganglioside 总被引:2,自引:0,他引:2
Abstract: Ganglioside analysis and quantitative Golgi studies of the cerebral cortex of cats with ganglioside and nonganglioside lysosomal storage diseases reveal a correlation between the amount of accumulated GM2 ganglioside and the extent of ectopic dendrite growth on cortical pyramidal neurons. This correlation was not observed with any of the other gangliosides assayed for, including GM1 ganglioside. These results suggest a specific role for GM2 ganglioside in the initiation of ectopic neurites on pyramidal cells in vivo and are consistent with the developing hypothesis that different gangliosides have specific roles in different cell types dependent upon the receptor or other effector molecules with which they may interact. 相似文献
62.
Nucleotide sequence information from a partial genomic clone, a cDNA clone, a RACE clone and a PCR fragment was combined to reconstruct the first reported complete gene sequence encoding a large legumin subunit, designated LelB3. The length difference to the well-characterized major legumin subunits is caused by an extended glutamin/glutamic acid-rich region encoded by the C-terminal part of the chain. Amino acid sequence comparisons reveal that gene LelB3 is more closely related to B-type than to A-type legumin genes of Vicia faba. Gene LelB3 is a member of a small gene family as indicated by published (Pich and Schubert, Biol Zbl 112 (1993); 342–350) and limited own data. 相似文献
63.
Effects of an antisense napin gene on seed storage compounds in transgenic Brassica napus seeds 总被引:4,自引:0,他引:4
Junko Kohno-Murase Makoto Murase Hiroaki Ichikawa Jun Imamura 《Plant molecular biology》1994,26(4):1115-1124
To manipulate the quantity and quality of storage components in Brassica napus seeds, we have constructed an antisense gene for the storage protein napin. The antisense gene was driven by the 5-flanking region of the B. napus napin gene to express antisense RNA in a seed-specific manner. Seeds of transgenic plants with antisense genes often contained reduced amounts of napin. In some transgenic plants, no accumulation of napin was observed. However, the total protein content of transgenic and wild-type seeds did not differ significantly. Seeds lacking napin accumulated 1.4 to 1.5 times more cruciferin than untransformed seeds, although the oleosin content was not affected. Fatty acid content and composition in the seeds of transgenic plants were also analyzed by gas chromatography. Though the total fatty acid content of the transformants was the same as that of non-transformants, there was a reduction in 18:1 contents and a concomitant increase of 18:2 in seeds with reduced napin levels. This observed change in fatty acid composition was inherited in the next generation. 相似文献
64.
The soybean embryo factor binding sequence in the glycinin A2B1a gene promoter was delimited to an A/T-rich 9 bp sequence, 5-TAATAATTT-3, designated as the glycinin box, by DNA footprinting and gel mobility shift assay using synthetic oligonucleotides. It was shown that the interaction with the factor takes place at a defined DNA sequence rather than at random A/T-rich sequence blocks in the glycinin 5 flanking region. There are four glycinin boxes in the quantitative regulatory region between positions – 545 and – 378 of the glycinin A2B1a promoter. Multiple nonamer motifs similar to the glycinin box were also found in the equivalent regions of other glycinin and legumin promoters, suggesting that they must be conserved as a binding site for the embryo factor that activates the differential and stage-specific expression of seed 11S globulin genes in leguminous plants. 相似文献
65.
Storage at 6.5°C under moderate vacuum effectively prevented growth of Aeromonas hydrophila on chicory endive, but had only a limited inhibitory effect on the growth of the organism on mung bean sprouts. Growth of Listeria monocytogenes on chicory endive was strongly stimulated under these conditions, whereas it was decreased on mung-bean sprouts. 相似文献
66.
Two methods of storing fine needle aspirates were compared in 14 patients with breast cancer. the methods of storage were: (1) as a Cytospin slide prepared immediately from the aspirated material and stored at −80°C; (2) as a suspension of cells in tissue culture medium, stored at −80°C. the effect of storage on the cells was assessed by means of an oestrogen receptor immunocytochemical assay (ER-ICA). an ER positivity of 100% was obtained by ER-ICA staining of cells after storage method 1, whilst all of the specimens stored by method 2 were ER-negative. the data demonstrate that cells stored in tissue culture medium at −80°C are not suitable for ER measurement. the storage method of choice for specimens intended for ERICA is as a Cytospin slide. the ER status of cells deposited on Cytospin slides prepared immediately and stored at −80°C for 2 years could be demonstrated despite the delay in processing the specimen. 相似文献
67.
Martin Fotso Jean-Louis Azanza Remy Pasquet Jacques Raymond 《Plant Systematics and Evolution》1994,191(1-2):39-56
81 wild forms and 110 cultivated cowpea,Vigna unguiculata, accessions from 21 countries of Africa were screened for variability in seed storage proteins. Total seed proteins, albumin and globulin fractions were investigated by means of sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and isoelectric focusing (IEF) of nonreduced and/or reduced samples in one- and two-dimensional procedures. The globulin fraction is heterogeneous in molecular weight and contains both legumin-like components and three to six nondisulfide-linked subunits. Three globulin subunits, with molecular weights 110, 76, and 41 kD were found to be composed of disulfide-linked polypeptides. In the nondisulfide-linked fraction, both cultivated and wild forms exhibited patterns of four types (A–D). This fraction contains polypeptide subunits of molecular weights 62, 56, and 52 kD for A type, 62, 56, 54, and 52 kD for B type, 62, 56, 52, and 50 kD for C type, and at least 62, 56, 54, 52, 50, and 49 kD for D type. These subunits present similar multiple charge forms but C and D types possess more basic specific 50 and 49 kD nondisulfide linked components. Major albumin fraction contains subunits of 94, 86, 32, and 24kD. No infraspecific variation was observed in albumin or legumin-like fractions. The discussion is focussed on the relations between genetic variability assessed by storage protein coding genes and phenotypic variability. 相似文献
68.
薏苡胚发育及贮藏营养物质积累的研究 总被引:4,自引:0,他引:4
薏苡(Coix lacrym a-jobi)胚发育分下列各期:棒形胚前的原胚期、棒形胚期、胚芽鞘期、1叶期、2 叶期、3叶期、4 叶期、5 叶期及6叶期成熟胚。3 叶期胚具1 条不定根(种子根),4 叶期具2 条,5 叶期及成熟胚期具3 条。不定根与胚根排成1 纵行。营养物质最先在盾片细胞中积累。开花后9 天的1 叶期胚,在盾片、胚芽鞘及胚轴细胞中积累了淀粉,以后遍及成熟胚的各部分。淀粉粒含量与器官发生及生长顺序成正相关,但发育后期,盾片细胞内的淀粉粒含量下降。开花后10 天,盾片细胞中形成含晶体的蛋白质体,晶体含蛋白质及植酸钙镁。以后,这种蛋白质体增多、增大。同时,又形成不含晶体的蛋白质体。一定时期,含晶体的蛋白质体消失,不含晶体的蛋白质体增多,直到胚成熟。开花后13 天,胚芽鞘上部细胞形成蛋白质体。以后遍及成熟胚的各部分,器官发生越早,所含蛋白质体越多、越大。开花后10 天,盾片细胞中产生了脂体,成熟胚的盾片细胞,含有大量的脂体。还观察了胚发育各期与颖果及盾片长度的对应关系 相似文献
69.
70.
Field measures of tree and shrub dimensions were used with established biomass equations in a stratified, two-stage cluster sampling design to estimate above-ground ovendry woody biomass and carbon storage of the eastern deciduous forest of North America. Biomass averaged 8.1 ± 1.4 (95% C.I.) kg/m2 and totaled 18.1 ± 3.1 (95% C.I.) gigatons. Carbon storage averaged 3.6 ± 0.6 (95% C.I.) kg/m2 and totaled 8.1 ± 1.4 (95% C.I.) gigatons. These values are lower than previous estimates commonly used in the analysis of the global carbon budget which range from 17.1 to 23.1 kg/m2 for biomass and 7.7 to 10.4 kg/m2 for carbon storage. These new estimates for the deciduous forest, together with earlier work in the boreal forest begin to reveal a pattern of overestimation of global carbon storage by vegetation in analyses of the global carbon budget. We discuss reasons for the differences between the new and earlier estimates, as well as implications for our understanding of the global carbon cycle. 相似文献