全文获取类型
收费全文 | 1503篇 |
免费 | 99篇 |
专业分类
1602篇 |
出版年
2023年 | 9篇 |
2022年 | 17篇 |
2021年 | 23篇 |
2020年 | 16篇 |
2019年 | 33篇 |
2018年 | 35篇 |
2017年 | 36篇 |
2016年 | 45篇 |
2015年 | 53篇 |
2014年 | 62篇 |
2013年 | 86篇 |
2012年 | 108篇 |
2011年 | 103篇 |
2010年 | 77篇 |
2009年 | 42篇 |
2008年 | 71篇 |
2007年 | 65篇 |
2006年 | 74篇 |
2005年 | 63篇 |
2004年 | 53篇 |
2003年 | 56篇 |
2002年 | 67篇 |
2001年 | 20篇 |
2000年 | 8篇 |
1999年 | 13篇 |
1998年 | 17篇 |
1997年 | 14篇 |
1996年 | 22篇 |
1995年 | 9篇 |
1994年 | 15篇 |
1993年 | 14篇 |
1992年 | 11篇 |
1991年 | 13篇 |
1990年 | 16篇 |
1989年 | 14篇 |
1988年 | 11篇 |
1987年 | 12篇 |
1984年 | 11篇 |
1983年 | 9篇 |
1982年 | 23篇 |
1981年 | 14篇 |
1980年 | 7篇 |
1979年 | 8篇 |
1978年 | 8篇 |
1977年 | 7篇 |
1976年 | 8篇 |
1975年 | 11篇 |
1974年 | 12篇 |
1973年 | 15篇 |
1968年 | 6篇 |
排序方式: 共有1602条查询结果,搜索用时 15 毫秒
11.
Karel Wernars Theo Goosen Bert M. J. Wennekes Klaas Swart Cees A. M. J. J. van den Hondel Henk W. J. van den Broek 《Molecular & general genetics : MGG》1987,209(1):71-77
Summary When a non-selected DNA sequence was added during the transformation of amdS320 deletion strains of Aspergillus nidulans with a vector containing the wild-type amdS gene the AmdS+ transformants were cotransformed at a high frequency. Cotransformation of an amdS320, trpC801 double mutant strain showed that both the molar ratio of the two vectors and the concentration of the cotransforming vector affected the cotransformation frequency. The maximum frequency obtained was defined by the gene chosen as selection marker for transformation. Cotransformation was used to induce a gene replacement in A. nidulans. An amdS320 strain was transformed to AmdS+ and cotransformed with a DNA fragment containing a fusion between a non-functional A. nidulans trpC gene and the Escherichia coli lacZ gene. Ten AmdS+, LacZ+ transformants with a Trp– mutant phenotype were selected. All of these strains could be transformed with a functional copy of the A. nidulans trpC gene, but only two strains yielded TrpC+ transformants which, with a low frequency, had a LacZ– phenotype. These latter transformants had also lost the AmdS+ phenotype. Southern blotting analysis of DNA from these transformants confirmed the inactivation of the wild-type trpC gene, but revealed that amdS vector sequences were also involved in the gene replacement events. 相似文献
12.
Attempt to detect recombination between B-F and B-L genes within the chicken B complex by serological typing,in vitro MLR,and RFLP analyses 总被引:1,自引:1,他引:0
Karel Hála Anne-Marie Chaussé Yves Bourlet Olli Lassila Viktor Hasler Charles Auffray 《Immunogenetics》1988,28(6):433-438
In search for recombinants within the chicken major histocompatibility B complex, 1155 animals from crosses between the congenic lines CB (B12) and CC (B4) were tested with alloantibodies and monoclonal antibodies for the B-F (class I), B-L (class II), and B-G (class IV) antigens and by mixed lymphocyte reaction. The absence of detectable recombination was confirmed by restriction fragment length polymorphism analysis with B-L
and B-F probes. Together with previous reports, this indicates that the distance between the B-F and B-L loci is below 0.01 centimorgan. 相似文献
13.
Rita Harris Martha Wright Michael Byrne James Varnum Blanche Brightwell Karel Schubert 《Plant cell reports》1988,7(5):337-340
Protoplasts were isolated from anther-derived suspension cultures of commercial wheat (Triticum aestivum L. cv. Chris). The protoplasts were released enzymatically and isolated by centrifugation on a sucrose cushion. The isolated protoplasts were initially cultured in a liquid medium in the dark. Numerous microcalli were produced under these conditions, some of which differentiated into globular embryos. Upon transfer to a solid medium and exposure to 16h/8h light/dark cycle, the protocalli proliferated and many of the somatic embryos matured. Complete plantlets were obtained and maintained in sterile culture.Abbreviations 2,4-D
2,4-Dichlorophenoxyacetic acid
- MES
2-[N-morpholino] ethanesulfonic acid 相似文献
14.
Fiala K. etHerrera R. (1988): Living and dead belowground biomass and its distribution in some savanna communities in Cuba.—Folia Geobot. Phytotax., Praha, 23: 225–237.— The paper sums up the first results obtained from the study of belowground biomass estimated in natural and anthropic savanna communities in different regions of Cuba at the end of the 1984 rainy season. The percentage of living roots in total root biomass of natural savannas was lower (34–50%) than that in the anthropic savanna stands (68–74%). The total belowground biomass in three savanna stands ranged from 1,073 to 1,257 g. m?2. In the natural savanna stands 433 to 517 g. m?2 of living belowground biomass was found, which was less than in the anthropic savanna stand (745 g. m?2). In all the savanna stands studied, more than 80% of both the total and living belowground biomass were found in the upper 0–0.2 m soil layer. The share of the living biomass in the belowground plant organs varied from 71 to 79%. 相似文献
15.
Karel Indrak Vaclav Brabec Jarmila Indrakova Ladislav Chrobak Adriana Sakalova Marie Jarosova Jaroslav Cermak You-jun Fei Ferdane Kutlar Yuan-chao Gu Erol Baysal Titus H. J. Huisman 《Human genetics》1992,88(4):399-404
Summary We have identified different -thalassemia mutations in 93 members of 34 families of Czech or Slovakian descent using gene amplification, hybridization with specific 32P-labeled oligonucleotide probes, sequencing of amplified DNA, and gene mapping. The GA mutation at IVS-I-1 was found in 18 families; other Mediterranean mutations were IVS-II-1 (GA), IVS-II-745 (CG), IVS-I-110 (GA), and codon 39 (CT); these were present in 9 additional families. The GT mutation at codon 121, known to cause Heinzbody -thalassemia, was present in 3 families, and the frameshift at codons 82/83 (-G), first described in the Azerbaijanian population, in 2 families. A newly discovered allele was a frameshift at codons 38/39 (-C). One -thalassemia allele was incompletely characterized. We observed in 2 families a TC mutation at position +96 UTR (untranslated region) relative to the termination codon; this mutation likely is a rare polymorphism, -Thalassemia was rare; only one person carried the -3.7 heterozygosity, and one other had a yet to be identified -thalassemia-1, while seven had the anti 3.7 triplication. 相似文献
16.
Continuous shoot growth monitoring in hydroponics 总被引:1,自引:0,他引:1
A weighing apparatus for automatic recording of fresh weight of shoots of spinach plants ( Spinacia oleracea L., cv. Subito) growing in nutrient solution is described. The system was tested for 17 days in a controlled environment and enabled the determination of the relative growth rate (RGR) of the shoot fresh weight. Results from three consecutive growth experiments demonstrated diurnal fluctuations in the relative growth rate of the shoot fresh weight. In general, relative growth rates were between 0.32 and 0.36 day−1 16 days after sowing and decreased to between 0.11 and 0.18 day−1 during the 12 following days. The variance between three replicate growth curves was compared with the variance of a growth function fitted through destructively obtained spinach shoot weight data. 相似文献
17.
Ming Shiang James C. Linden Ali Mohagheghi Karel Grohmann Michael E. Himmel 《Applied microbiology and biotechnology》1991,34(5):591-597
Summary Fed-batch fermentations of Acidothermus cellulolyticus utilizing mixtures of cellulose and sugars were investigated for potential improvements in cellulase enzyme production. In these fermentations, we combined cellulose from several sources with various simple sugars at selected concentrations. The best source of cellulose for cellulase production was found to be ball-milled Solka Floc at 15 g/l. Fed-batch fermentations with cellobiose and Solka Floc increased cell mass only slightly, but succeeded in significantly enhancing cellulase synthesis compared to batch conditions. Maximum cellulase activities obtained from fermentations initiated with 2.5 g cellobiose/l and 15 g Solka Floc/l were 0.187 units (U)/ml, achieved by continuous feeding to maintain <0.1 g cellobiose/l, and 0.215 U/ml using the same initial medium when 2.5 g cellobiose/l was step-fed after the sugar was nearly consumed. In batch, dual-substrate systems consisting of simple sugars with Solka Floc, substrate inhibition was evident in terms of specific growth rates, specific productivity values, and maximum enzyme yields. Limiting concentrations of glucose or sucrose at 5 g/l, and cellobiose at 2.5 g/l, in the presence of Solka Floc, yielded cellulase activities of 0.134, 0.159, and 0.164 U/ml, respectively.
Offprint requests to: M. E. Himmel 相似文献
18.
Kees Nieuwenhuijsen Ad J. J. C. Lammers Karel J. de Neef A. Koos Slob 《International journal of primatology》1985,6(1):77-99
Reproductive physiology was studied in female stumptail macaques. Initially the monkeys were housed indoors (individually
and in small groups) and later as one large (92 individuals) social group in an outdoor cage. Most data were collected during
the 4-year outdoor period. Plasma progesterone determination in blood samples taken at weekly intervals allowed estimation
of ovulation and conception dates. The age at first ovulation (X =3.73 years) was positively correlated with body weight at 3 years of age. The average age at first birth was 4.90 years. Gestation
lengths averaged 176.6 days. Following a live birth ovulations returned after a mean interval of 11 months but following an
abortion or still birth this interval was 1 month. Usually a number of ovulatory cycles (X =2.37) preceded a conception. Interbirth intervals (IBIs) in the outdoor cage (X =619.4 days) were significantly longer than IBIs during the indoor period (X =523.1), because indoors the infants were weaned at the age of 7 months, while outdoors weaning occurred more naturally. IBIs
following abortions or still births (X =291.9 days) were significantly shorter than IBIs following live births. Age at first ovulation, age at first birth, IBIs,
and infant production rates were not correlated with dominance rank. Ovarian cycle lengths (X =30.2 days, mode = 28 days) were comparable to previously reported data from laboratory-housed stumptails. No systematic seasonal
fluctuations were found in the onset of sexual maturity, in ovarian cycle lengths, in copulation frequencies, and in distribution
of births. 相似文献
19.
Kristin M. G. Heirwegh Nirmalya Banerjee Karel van Nerum Edmond de Langhe 《Plant cell reports》1985,4(2):108-111
Somatic embryogenesis of Cichorium intybus L. var. Carolus is induced using cubical pieces of mature tap roots with an intervening callus phase. A Murashige and Skoog's (MS) semi solid basal medium supplemented with 2,4-dichlorophenoxyacetic acid (0.02 or 0.2 mg/l) and benzylaminopurine (0.25 mg/l) and a liquid MS medium devoid of growth regulators are used respectively for induction of callus and somatic embryoids and for further development and germination. Regeneration from the nodular proembryonal stage to the full grown embryoids occurs following different morphological pathways depending on the physical and chemical environment of the culture. Further development of these embryos into plantlets and the possibilities of application of this technique in plantbreeding have been discussed.Abbreviations MS
Murashige and Skoog medium
- BAP
benzylaminopurine
- 2,4-D
2,4-dichlorophenoxyacetic acid 相似文献
20.