全文获取类型
收费全文 | 2810篇 |
免费 | 332篇 |
国内免费 | 1篇 |
出版年
2021年 | 24篇 |
2018年 | 28篇 |
2017年 | 29篇 |
2016年 | 35篇 |
2015年 | 76篇 |
2014年 | 85篇 |
2013年 | 107篇 |
2012年 | 120篇 |
2011年 | 101篇 |
2010年 | 83篇 |
2009年 | 58篇 |
2008年 | 99篇 |
2007年 | 115篇 |
2006年 | 89篇 |
2005年 | 111篇 |
2004年 | 101篇 |
2003年 | 103篇 |
2002年 | 89篇 |
2001年 | 101篇 |
2000年 | 85篇 |
1999年 | 72篇 |
1998年 | 40篇 |
1997年 | 38篇 |
1996年 | 36篇 |
1995年 | 39篇 |
1994年 | 36篇 |
1993年 | 32篇 |
1992年 | 58篇 |
1991年 | 73篇 |
1990年 | 56篇 |
1989年 | 56篇 |
1988年 | 40篇 |
1987年 | 52篇 |
1986年 | 51篇 |
1985年 | 57篇 |
1984年 | 43篇 |
1983年 | 41篇 |
1982年 | 28篇 |
1981年 | 37篇 |
1980年 | 30篇 |
1979年 | 45篇 |
1978年 | 52篇 |
1977年 | 37篇 |
1976年 | 48篇 |
1975年 | 34篇 |
1974年 | 44篇 |
1973年 | 42篇 |
1972年 | 37篇 |
1971年 | 25篇 |
1970年 | 24篇 |
排序方式: 共有3143条查询结果,搜索用时 31 毫秒
991.
Cytogenetic analysis of lymphoblastoid cell lines 总被引:3,自引:0,他引:3
M A Abruzzo P A Hunt M Mayer P A Jacobs J C Wang R W Erbe 《Cytogenetics and cell genetics》1986,42(3):169-173
Cytogenetic abnormalities were discovered in more than half of 16 lymphoblastoid cell lines established from fragile X individuals and their relatives upon routine cytogenetic analysis of early passage cultures. Subsequently, a second series of lymphoblastoid lines was analyzed to determine if the aneuploidy was a characteristic of lymphoblastoid cell lines derived from fragile X families or a result of the use of cyclosporin A in the establishment of these lines. In the second series of 33 lymphoblastoid cultures, no aneuploid clones were found in the fragile X group, while two were detected in the control cultures, one in a line initiated with cyclosporin A and the other in a line established without cyclosporin A. We conclude that the abnormal clones in our preliminary series were not a characteristic of lines derived from fragile X families and probably not due to the use of cyclosporin A. However, the finding of chromosome abnormalities in a large proportion of lines during the first 3 mo of culture contrasts with previous reports of chromosome stability for the first 12-18 mo of cultivation and indicates that the chromosomes of lymphoblastoid lines should be monitored in any experiment in which a normal diploid complement is critical. 相似文献
992.
The circadian movement of the lamina of the primary leaf of Phaseolus coccineus is mediated by circadian volume changes of the extensor and flexor cells in the upper and lower half of the laminar pulvinus. Isolated protoplasts from the extensor, flexor, and flank cells of the pulvinus showed a circadian volume rhythm with a period longer than 24 h. In the case of the flexor protoplasts, we found a period length of 28 h, which is similar to that of the pulvinar cells in situ. In the extensor protoplasts, the volume rhythm was synchronized with 14-h light/10-h dark cycles. The larger volume was correlated with the early hours in the light period and the smaller volume with the dark period, as would be expected from the behavior of the extensor cells in situ. 相似文献
993.
994.
Mayer Alejandro M. S. Krotz Liliana Bonfil R. Daniel Bustuobad Oscar D. Groisman Jose F. de Lederkremer Rosa M. Stierle Donald B. 《Hydrobiologia》1987,151(1):483-489
995.
E. Mayer D.J. Gardiner R.E. Hester 《Biochimica et Biophysica Acta (BBA)/General Subjects》1973,297(2):568-570
The Raman spectra of cyanocobalamin (vitamin B12) and dicyanocobinamide have been obtained from aqueous solutions at concentrations of approx. 1 10−4 M. The spectra were excited by laser radiation coincident in wavelength with the visible absorption, this resulting in selective enhancement of some vibrational modes through the rigorous resonance Raman effect. In spite of substantial chemical differences, cyanocobalamin and dicyanocobinamide give essentially identical spectra, indicating that only those modes associated with the common corrin ring system are resonance enhanced. 相似文献
996.
997.
Two families were ascertained through a proband with Down syndrome and a structural rearrangement involving two chromosomes 21. It is suggested that in one patient the chromosome is an isochromosome formed by misdivision of the centromere of a maternal telocentric chromosome 21 and that in the other a Robertsonian translocation involving chromosome 21 was inherited from the mother, who is a 46,XX/46,XX, -21,+t(21q21q) mosaic. The origin of the mosaicism is discussed and considered to be likely to be the result of breakage and reunion at the chromatid, rather than the chromosome, level. 相似文献
998.
Effects of chemical combinations on the induction of aneuploidy in Saccharomyces cerevisiae 总被引:1,自引:0,他引:1
Nocodazole, ethyl acetate, acetone and methyl ethyl ketone all are known to induce aneuploidy. Treatment of yeast strain D61.M with mixtures containing ineffective low levels of nocodazole and ineffective low levels of these solvents was highly effective in inducing aneuploidy. Ineffective low levels of nocodazole mixed with ineffective low levels of methyl 2-benzimidazolecarbamate also gave elevated frequencies of aneuploidy. Dimethyl formamide, a solvent that does not induce aneuploidy, mixed with low levels of nocodazole gave no increase in aneuploidy frequency above those levels seen in controls. 相似文献
999.
From data of meteorological stations in a city (Munich) and in a forest (Ebersberger Forst, near Munich) for the summer months 1972 mean monthly diurnal variations of the following parameters were computed: vapour pressure, equivalent temperature, effective temperature, energy consumption with respiration and hourly water requirement for saturation of the respiratory air. The results show that during the summer season forest air is bioclimatically more comfortable than city air for humans. 相似文献
1000.
In the 1970s, acid sulfate soils (ASS) distributed within about 720 ha of predominantly mangrove and salt pan wetlands at
East Trinity in north Queensland were developed after the area was isolated from tidal flooding by a surrounding seawall and
the installation of tidal gates on major drainage creeks. Following drainage and oxidation of these estuarine acidic sediments,
resultant acid leachate caused considerable, ongoing environmental problems including regular fish kills. A rehabilitation
program covering much of these former tidal wetlands commenced in 2000 using a lime-assisted tidal exchange management regime.
Changes in the established populations of estuarine fish and crustaceans were monitored in the two creeks (Firewood and Hills
Creeks) where tidal flows were reinstated. In Firewood Creek between 2001 and 2005, there was a progressive increase in fish
species richness, diversity and abundance. The penaeid prawn Fenneropenaeus merguiensis was a major component of the cast net catches in the lower sections of both Firewood and Hills Creeks but its relative abundance
decreased upstream of the tidal gates on the seawall. Well established stocks of predominantly juvenile, male Scylla serrata resident upstream of the tidal gates indicated suitable habitats with acceptable water and sediment quality and adequate
availability of food. The regular fish kills that occurred prior to the management regime abated and, overall, the implementation
of the rehabilitation program is yielding positive benefits for the local fisheries. 相似文献