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161.
In hybrid zones, endogenous counter-selection of hybrids is usually first expressed as reduced fertility or viability in hybrids of the heterogametic sex, a mechanism known as Haldane's rule. This phenomenon often leads to a differential of gene flow between sex-linked markers. Here, we address the possibility of a differential gene flow for Y chromosome, mtDNA and autosomal markers across the hybrid zone between the genetically and chromosomally well-differentiated species Sorex antinorii and Sorex araneus race Vaud. Intermarker comparison clearly revealed coincidental centre and very abrupt clines for all three types of markers. The overall level of genetic differentiation between the two species must be strong enough to hinder asymmetric introgression. Cyto-nuclear mismatches were also observed in the centre of hybrid zone. The significantly lower number of mismatches observed in males than in females possibly results from Y chromosome-mtDNA interactions. Results are compared with those previously reported in another hybrid zone between S. antinori and S. araneus race Cordon. 相似文献
162.
163.
The regional abundance of C4 grasses is strongly controlled by temperature, however, the role of precipitation is less clear. Progress in elucidating the direct effects of photosynthetic pathway on these climate relationships is hindered by the significant genetic divergence between major C3 and C4 grass lineages. We addressed this problem by examining seasonal climate responses of photosynthesis in Alloteropsis semialata , a unique grass species with both C3 and C4 subspecies. Experimental manipulation of rainfall in a common garden in South Africa tested the hypotheses that: (1) photosynthesis is greater in the C4 than C3 subspecies under high summer temperatures, but this pattern is reversed at low winter temperatures; and (2) the photosynthetic advantage of C4 plants is enhanced during drought events. Measurements of leaf gas exchange over 2 years showed a significant photosynthetic advantage for the C4 subspecies under irrigated conditions from spring through autumn. However, the C4 leaves were killed by winter frost, while photosynthesis continued in the C3 plants. Unexpectedly, the C4 subspecies also lost its photosynthetic advantage during natural drought events, despite greater water-use efficiency under irrigated conditions. This study highlights previously unrecognized roles for climatic extremes in determining the ecological success of C3 and C4 grasses. 相似文献
164.
Colletotrichum lindemuthianum, the causal agent of anthracnose in the common bean (Phaseolus vulgaris), presents a wide genetic and pathogenic variability that gives rise to complications in the development of resistant bean
cultivars. The aim of this study was to identify the variability within race 65 of C. lindemuthianum, the race most commonly encountered in Brazil, through randomly amplified polymorphic DNA (RAPD) and anastomosis analyses.
Thirteen isolates of race 65, collected in different years and from various host cultivars located in diverse areas of the
state of Minas Gerais, Brazil, were investigated. Twenty-four RAPD primers were employed and 83 polymorphic bands amplified.
Genetic similarities were estimated from the Sorensen-Dice coefficient and ranged from 0.54 to 0.82. The dendrogram obtained
by cluster analysis classified the isolates into 11 separate groups. For the purposes of the analysis of anastomosis, isolates
were considered to be compatible when the fusion of hyphae from different isolates could be observed. The proportion of compatible
reactions for each isolate was estimated and similarity estimates, based on the Russel & Rao coefficient, ranged from 0.28
to 0.85. Isolates were classified into 11 anastomosis groups, 10 of which were formed by only one isolate. Although isolates
LV61, LV73 and LV58 were classified in the same anastomosis group, they were genetically distinct according to RAPD analysis.
Results from both RAPD and anastomosis analyses revealed great variability within C. lindemuthianum race 65. 相似文献
165.
鲤鱼sGnRH基因克隆及其在成熟个体的表达分析 总被引:5,自引:0,他引:5
采用RACE方法,从鲤鱼脑组织克隆了两个差异的sGnRH(salmon GnRH[Trp^7Leu^8]GnRH)cDNAs,即cDNA1和cDNA2,其长度分别为393和478bp。两个cDNAs都包括一个285bp开放阅读框,编码的sGnRH前体为94个氨基酸残基,由一个信号肽、sGnRH十肽和一个由蛋白水解位点(Gly-Lys-Arg)连接的促性腺激素释放激素相关肽共3部分组成。用内含子捕获得到相应的两个差异sGnRH基因,即sGnRH genel和gene2,其基本结构都包括4个外显子和3个内含子,3个内含子的核苷酸相似性分别为71.1%、76.1%和88.0%。鲤鱼sGnRH cDNAs及基因的基本结构和编码特点与已报道的不同形式GnRH cDNAs和GnRH基因相似,由此推测所有类型的GnRH可能来自一个共同的祖分子。Southern杂交进一步证实鲤鱼基因组存在两个不同的sGnRH基因座位。相对定量RT-PCR检测发现,两个sGnRH基因除在精巢的表达存在差异外,在脑区、垂体和成熟卵巢共表达。其中两个sGnRH基因在端脑和下丘脑的表达水平明显高于后脑区。根据sGnRH mRNAs在多个脑区、性腺和垂体的共存推测,sGnRH可能对鲤鱼下丘脑-垂体-性腺轴的调节有至关重要作用,同时可能起神经调节剂或自分泌和旁分泌调节因子的作用。 相似文献
166.
167.
Kimura Sonoko D. Schmidtke Knut Tajima Ryosuke Yoshida Koichi Nakashima Hiroshi Rauber Rolf 《Plant and Soil》2004,258(1):91-101
The adzuki bean (Vigna angularis (Wild.) Ohwi and Ohashi) and common bean (Phaseolus vulgaris L.) have a high physiological demand for N. A 2-year field study was conducted to investigate the seasonal change of available soil N and symbiotic N2 fixation usage. The beans were seeded at two densities, 22.2 plants m–2 with a row spacing of 0.3 m and 11.1 plants m–2 with a row spacing of 0.6 m. The amount of fixed N2 in the shoot was calculated using the 15N natural abundance method. The common bean demonstrated low N2 fixation and the ability to accumulate high levels of soil N. Soil nitrate under the common bean was continually absorbed. The adzuki bean, on the other hand, had a remarkable peak of N accumulation in the early reproductive stage. This was mainly due to N2 fixation, though the soil nitrate level was high. Narrowing the plant row spacing increased the dry matter yield of both species, but the origin of the increased N differed between the species. For the first 77 DAP in 1999 (73 DAP in 2000) the N increase for both beans was due to both soil and atmospheric N2. At harvest, though, the increase of N in common bean was mainly due to soil N, while that in adzuki bean was mainly due to atmospheric N2. It can be concluded that the low symbiotic N2 fixation ability of common bean was due to its high soil N uptake ability and constant N accumulation, which enabled an efficient soil N absorption. Adzuki bean absorbed N mainly for a short period and depended more on symbiotically fixed N2 and, in contrast to common bean, left a high level of NO3-N remaining in the soil after cropping. 相似文献
168.
169.
Symmetric and asymmetric protoplast fusion between long term cell suspension-derived protoplasts ofTriticum aestivum (cv. Jinan 177) and protoplasts ofHaynaldia villosa prepared from one-year-old embryogeneric calli was performed by PEG method. In asymmetric fusion, donor calli were treated
with gamma ray at a dose of 40, 60, 80 Gy (1.3 Gy/min) respectively and then used to isolate protoplasts. Results of morphological,
cytological, biochemical (isozyme) and 5S rDNA spacer sequence analysis revealed that we obtained somatic hybrid lines at
high frequency from both symmetric and asymmetric fusion. Hybrid plants were recovered from symmetric and low dose γ-fusion
combinations. GISH (genomicin situ hybridization) analysis proved exactly the existence of both parental chromosomes and the common occurrence of several kinds
of translocation between them in the hybrid clones regenerated from symmetric and asymmetric fusion. And the elimination of
donor DNA in hybrid clones regenerated from asymmetric fusion combinations was found to increase with the increasing gamma
doses. It is concluded that transference and recombination of nuclear DNA can be achieved effectively by symmetric and asymmetric
fusion, hybrids with small fragment translocation which are valuable in plant breeding can be obtained directly by asymmetric
fusion. 相似文献
170.
V. Debacker A. Rutten T. Jauniaux C. Daemers J-M. Bouquegneau 《Biological trace element research》2001,82(1-3):87-107
Combined effects of heavy-metal contamination (Cu, Zn, and CH3Hg) and starvation were tested on common quails (Coturnix coturnix japonica) and used as a model for comparison with a wild common guillemot (Uria aalge) population found stranded at the Belgian coast. Appropriate heavy-metal levels were given to the quails to obtain concentrations
similar to those found in the seabirds’s tissues. The contaminated animals were then starved for 4 d to simulate the evident
malnutrition symptoms observed at the guillemot’s level. In such conditions, food intake and total-body weight are shown to
decrease in contaminated individuals with simultaneous significant hepatic and renal increase of the heavy-metal concentrations.
Like guillemots, higher heavy-metal levels were observed in those contaminated quails that had also developed a cachectic
status characterized by a general atrophy of their pectoral muscle and complete absence of subcutaneous and/or abdominal fat
depots. Although likely the result of a general protein catabolism during starvation, it is suggested that these higher metal
levels could as well enhance a general muscle wasting process (cachectic status). 相似文献