全文获取类型
收费全文 | 4952篇 |
免费 | 263篇 |
出版年
2021年 | 45篇 |
2020年 | 41篇 |
2018年 | 144篇 |
2017年 | 118篇 |
2016年 | 152篇 |
2015年 | 115篇 |
2014年 | 141篇 |
2013年 | 239篇 |
2012年 | 256篇 |
2011年 | 300篇 |
2010年 | 190篇 |
2009年 | 146篇 |
2008年 | 190篇 |
2007年 | 169篇 |
2006年 | 209篇 |
2005年 | 138篇 |
2004年 | 133篇 |
2003年 | 129篇 |
2002年 | 116篇 |
2001年 | 105篇 |
2000年 | 106篇 |
1999年 | 80篇 |
1998年 | 35篇 |
1997年 | 45篇 |
1996年 | 45篇 |
1995年 | 42篇 |
1994年 | 54篇 |
1993年 | 39篇 |
1992年 | 51篇 |
1991年 | 49篇 |
1990年 | 38篇 |
1989年 | 46篇 |
1988年 | 47篇 |
1987年 | 39篇 |
1986年 | 48篇 |
1985年 | 53篇 |
1984年 | 69篇 |
1983年 | 55篇 |
1982年 | 53篇 |
1981年 | 50篇 |
1980年 | 38篇 |
1979年 | 49篇 |
1978年 | 48篇 |
1976年 | 39篇 |
1975年 | 40篇 |
1974年 | 54篇 |
1973年 | 45篇 |
1972年 | 38篇 |
1969年 | 35篇 |
1968年 | 41篇 |
排序方式: 共有5215条查询结果,搜索用时 31 毫秒
991.
Jabmila Solábová T. Herben Libuše Pavlová Kateřina Pánková J. Tupý 《Biologia Plantarum》1985,27(2-3):237-240
992.
Betulinic acid (3β-hydroxy-lup-20(29)-en-28-oic acid) was obtained from in vitro cultures of Solanum aviculare in yields up to 3% of the dry weight. This is a further example of overproduction by cells cultured in vitro of a product not found in the original parent plant. 相似文献
993.
Radka Černý-Provazník Peter van Mourik Jacqueline Limpens Tine Leupers Dr. Pavol Iványi 《Immunogenetics》1985,21(5):491-504
Cell fusion was performed between spleen cells from young BALB/cBy (H-2
d) mice which have never been immunized and SP2/0 mouse plasmacytoma cells. A monoclonal H-2-specific cytotoxic IgM antibody was obtained (By-1) which detected a new public biregional H-2 specificity, H-2.m210. The mcAb By-1 reacted strongly with H-2Kd, Dd, and H-2s antigens, gave weak cross-reactions with H-2Kk, Dq, H-2r, and H-2v antigens and was negative with H-2b, H-2f, H-2p, and H-2Ld antigens. A polymorphic reaction pattern was also observed on a panel of lymphocytes from B 10.W strains. The intriguing finding on this reaction pattern was the reactivity on H-2d cells, including the syngeneic BALB/cBy and truly autologous cells. As shown by capping and immunoprecipitation experiments on H-2d cells and by studies on H-2d-transfected mouse L cells, the target molecules for McAb By-1 were H-2Kd and H-2Dd molecules. The BALB/cBy mouse, from whose spleen cells the McAb By-1 was obtained, survived after the fusion experiment, and serum was examined for the presence of cytotoxic H-2-specific antibodies during the rest of its life. At the time of the fusion, no autoreactive serum antibodies were found, but about 4 months later, we found in the serum of this mouse autoreactive H-2-specific cytotoxic IgM antibodies. The serum antibodies followed the same reaction pattern as that of the McAb By-1. As far as we know, this is the first report of autoreactive H-2-specific antibodies in serum of a mouse which has never been immunized and of the first natural autoreactive H-2-specific monoclonal antibody.Abbreviations McAb
monoclonal antibody
- MHC
major histocompatibility complex
-
H-2
major histocompatibility complex of mice
- CTLs
cytotoxic T cells
- FMF
flow microfluorometry
- FITC
fluorescein isothiocyanate
- LPS
lipopolysaccharide W.E. coli 0111:134
- PBS
phosphate-buffered saline
- Iodogen
1,3,4,6,-tetrachloro-3,6-diphenylglycoluril
- GAMIg
goat-antimouse immunoglobulin
- Staph-A
Staphylococcus aureus Cowan I 相似文献
994.
995.
The paper summarizes hitherto known data concerning the biology and ecology ofSagittaria sagittifolia. The distribution of this species in Czechoslovakia was assessed on the basis of literature data, herbarium specimens and the authors’ own data. The occurrence of this species in plant communities is shown in tables from selected phytocoenological relevés. The chemical properties of the substratum in habitats ofSagittaria sagittifolia over all its distribution area in Czechoslovakia were studied and comparisons calculated by means of cluster analysis. Life cycle, seed production, germination and biomass production of this species were studied and compared with conditions in its habitats. 相似文献
996.
997.
Immunohistochemical analysis of nerve growth factor receptor expression in normal and malignant human tissues 总被引:9,自引:0,他引:9
P G Chesa W J Rettig T M Thomson L J Old M R Melamed 《The journal of histochemistry and cytochemistry》1988,36(4):383-389
Nerve growth factor (NGF) is a polypeptide important for normal development of the nervous system and promotion of survival and differentiation of sensory and sympathetic neurons in culture. The cellular effects of NGF are mediated by a specific cell surface molecule, nerve growth factor receptor (NGF-R). In the present study we have used a monoclonal antibody against human NGF-R to examine, by the avidin-biotin-immunoperoxidase method, the receptor distribution in a wide range of normal tissues and in more than 200 malignant tumors. Our results show that (a) human NGF-R is expressed in the peripheral nervous system but not in any of the central nervous system areas tested; (b) NGF-R expression is not restricted to neural tissues but is also found in a number of normal epithelial, mesenchymal, and lymphoid tissues; (c) NGF-R expression changes during normal development; and (d) NGF-R expression in malignant tumors generally parallels its normal tissue distribution. Thus, NGF-R is detected in a proportion of neuroectoderm-derived tumors, carcinomas, and lymphomas, and also in a characteristic group of small round-cell tumors (Ewing's sarcomas and embryonal rhabdomyosarcomas). These findings suggest a normal regulatory role for NGF in both neuronal and non-neuronal cells and identify a range of human tumors in which the NGF/NGF-R system may contribute to the malignant phenotype. 相似文献
998.
Jindřich Chrtekjun 《Folia Geobotanica》1992,27(2):177-183
The division of the speciesStachys recta into four subspecies is proposed. Besides the nominate subspecies, subsp.grandiflora (Caruel) Arcangeli, subsp.subcrenata (Vis.) Briq. and the newly combinedS. recta subsp.rhodopaea (Vel.) Chrtek jun. are described. The last subspecies differs from the others mainly by the calyx shape (infundibular here) and by the calyx teeth which are about as long as the tube. It is distributed in Macedonia and Bulgaria. A determination key to the species of theS. recta group is provided. 相似文献
999.
Marie Doleželová Jaroslav Doležel Milan Neštický 《Plant Cell, Tissue and Organ Culture》1992,31(3):215-221
Axillary bud explants of 11 selected mature waratah clones were established in vitro on a modified Murashige & Skoog medium. Adequate proliferation of axillary shoots was achieved by optimisation of the growth regulator status of the culture medium. For the majority of clones, a three to six times rate of proliferation was achieved with 1.25 M BA and 1.0 M GA3 without the occurrence of abnormalities. The white flowering clone did not respond favourably to the addition of GA3 to the medium.Abbreviations BA
benzyladenine
- GA3
gibberellic acid
- IBA
indole-3-butyric acid
- LSD
least significant difference
- MS
Murashige & Skoog medium 相似文献
1000.
The aim of this paper was to study, in the second leaf of wheat plants with a long ontogenesis (47 d), the activity of the
enzyme which catalyzes the synthesis of glutamic acid. The activity of the NADH-dependent glutamate synthase prevailed in
young tissues of not yet fully expanded second leaf at the stage of incomplete autotrophy (at this stage, organic carbon and
nitrogen substances are transferred into the leaf). This form was completely inhibited by azaserine (1 mmol1−1). The activity of the ferredoxin-dependent GOGAT increased with increasing leaf blade area, with its peak occuring at the
time of maximum expansion of the assimilation area. Thus fd-GOGAT activity was characteristic for the photosynthetic fully
autotrophic phase of leaf development which is materialized in completely mature leaf tissues. In plants grown in full-strength
Knop’s nutrient solution containing nitrogen, fd-GOGAT was active till the early and medium senescence, whereas only to the
early senescence in plants grown in a solution lacking nitrogen. No fd-GOGAT could be detected at the stage of late leaf senescence. 相似文献