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91.
Brown holo-membrane was prepared by the addition of all-trans-retinal to brown apo-membrane which was isolated from Halobacterium halobium grown in the presence of nicotine. The effects of pH and NaCI concentration on the absorbance spectrum of the brown holo-membrane were investigated in comparison with those of the purple membrane. The λmax of the dark-adapted brown holo-membrane shifted from 560 to 600 nm by lowering pH. The pK value which was determined as the mid-point pH for the spectral red-shift was 5.8 in the absence of NaCl. It was lowered to 4.5 and 3.4 in 0.1 and 1 M NaCl solutions, respectively. The pK value for the brown holo-membrane was larger than the corresponding value for the purple membrane in the NaCl solution. Bacteriorhodopsins present in the purple membrane and in the brown holo-membrane were solubilized in the nonionic detergent, lauryl ester of sucrose. For both solubilized bacteriorhodopsins, the pK value of spectral red-shift was about 3.1 in water, and the pI value, determined by chromatofocusing, was about 4.6 at 22°C. 相似文献
92.
Magnetic fields influence two properties of the P-870 triplet state observed in Rps.
sphaeroides reaction centers: the yield of formation and the kinetics of decay. These effects have been studied in reaction centers which were prepared in three different states: state QA
–, state QA
2– and state (– QA) (QA depleted). The triplet yields decrease with increasing magnetic fields, with B1/2's of about 140, 41 and 57 Gauss, respectively. The half-time of 3P-870 decay is not influenced by the field in state QA
–; it increases at increasing fields, in state QA
2– and state (– QA), with the same B1/2 as the triplet yield. These results are discussed in the framework of current theories of the radical-pair dynamics and of the mechanism of triplet decay.Abbreviations I
primary electron acceptor
- LDAO
lauryldimethylamine oxide
- P-870
primary electron donor
- QA
first quinone acceptor
- SDS
sodium dodecylsulfate
- YAG
Yttrium Aluminum Garnet 相似文献
93.
Population structure of Purple Sandpipers (Calidris maritima) as revealed by mitochondrial DNA and microsatellites 下载免费PDF全文
Nathalie M. LeBlanc Donald T. Stewart Snaebjörn Pálsson Mark F. Elderkin Glen Mittelhauser Stephen Mockford Julie Paquet Gregory J. Robertson Ron W. Summers Lindsay Tudor Mark L. Mallory 《Ecology and evolution》2017,7(9):3225-3242
The Purple Sandpiper (Calidris maritima) is a medium‐sized shorebird that breeds in the Arctic and winters along northern Atlantic coastlines. Migration routes and affiliations between breeding grounds and wintering grounds are incompletely understood. Some populations appear to be declining, and future management policies for this species will benefit from understanding their migration patterns. This study used two mitochondrial DNA markers and 10 microsatellite loci to analyze current population structure and historical demographic trends. Samples were obtained from breeding locations in Nunavut (Canada), Iceland, and Svalbard (Norway) and from wintering locations along the coast of Maine (USA), Nova Scotia, New Brunswick, and Newfoundland (Canada), and Scotland (UK). Mitochondrial haplotypes displayed low genetic diversity, and a shallow phylogeny indicating recent divergence. With the exception of the two Canadian breeding populations from Nunavut, there was significant genetic differentiation among samples from all breeding locations; however, none of the breeding populations was a monophyletic group. We also found differentiation between both Iceland and Svalbard breeding populations and North American wintering populations. This pattern of divergence is consistent with a previously proposed migratory pathway between Canadian breeding locations and wintering grounds in the United Kingdom, but argues against migration between breeding grounds in Iceland and Svalbard and wintering grounds in North America. Breeding birds from Svalbard also showed a genetic signature intermediate between Canadian breeders and Icelandic breeders. Our results extend current knowledge of Purple Sandpiper population genetic structure and present new information regarding migration routes to wintering grounds in North America. 相似文献
94.
中国南方紫水鸡(Porphyrio porphyrio)在快速扩散,探究其生态适应十分必要。2014年3月至2015年8月在云南鹤庆草海湿地的观察,得到以下结果。紫水鸡集中分布在以开阔水域为主并有足够植被覆盖的西草海,很少见于附近干扰频繁的其他湿地,其适宜的生境开阔水域约占49.6%、水生植被覆盖水面占39.3%、陆地占11.1%;紫水鸡早间(7:00~9:00时)频繁活动在开阔水域、高草丛、岸边草地,中午后逐渐远离岸边而藏掖草丛中;白天活动的紫水鸡集群大小在1~7只之间,1~2只的集群占62.0%,大的集群中常有司职警戒、领头的个体;紫水鸡用于觅食、休息、警戒的时间分别占47.8%、23.5%、15.1%,很少互动交流,但常驱赶靠近的其他鸟类以维护个体自身的"领域";紫水鸡应对干扰威胁的警戒、避让、惊飞平均距离分别是26.4 m、20.5 m和17.6 m。在鹤庆的紫水鸡集中分布于西草海湿地并避让人为干扰,说明其以避让和逃逸方式应对人为干扰和生境胁迫,应该考虑立法给予重点保护。 相似文献
95.
In order to estimate the degree of orientation of the α-helices of intrinsic proteins in photosynthetic membranes, polarized infrared spectroscopy has been used to measure the dichroism of the amide I and amide II absorption bands of air-dried oriented samples of purple membranes, chloroplasts and chromatophores from Rhodopseudomonas sphaeroides. Using purple membrane, in which the orientation of the α-helices is precisely known (Henderson, R. (1977) Annu. Rev. Biophys. Bioeng. 6, 87–109), as a standard to calibrate our measurements and estimating the mosaic spread (extent of orientation) of the membranes from linear dichroism measurements performed in the visible spectral range, it is concluded that in photosynthetic membranes, the α-helices of intrinsic proteins are tilted at less than 40° with respect to the normal to the plane of the membrane. 相似文献
96.
A novel type of purple sulfur bacterium was isolated from a hypersaline sulfur spring on the shore of the Dead Sea. The cells of the isolate are irregularly rod-shaped or curved, and motile by means of a tuft of polar flagella. The photosynthetic system, containing bacteriochlorophyll a and carotenoids of the spirilloxanthin series, is located on stacks of lamellar membranes in the cell cytoplasm. The organism can grow either photoautotrophically with sulfide as electron donor, which is oxidized via extracellular sulfur to sulfate, or photoheterotrophically, using acetate, succinate, fumarate, malate or pyruvate as carbon sources. The bacterium is obligately anaerobic, and requires a source of reduced sulfur for growth. The isolate is moderately halophilic, and grows optimally at NaCl concentrations between 3 and 8%, temperatures between 30 and 45°C, and neutral pH. 16S ribosomal RNA oligonucleotide cataloging suggests a close relationship to purple sulfur bacteria of the genus Ectothiorhodospira. As the isolate differs greatly from the described members of the genus Ectothiorhodospira, we describe the isolate as a new species, and propose the name Ectothiorhodospira marismortui sp. nov. 相似文献
97.
红菜薹游离小孢子培养与植株再生 总被引:11,自引:0,他引:11
以5个红菜薹(Brassica compestris ssp.chinensis var.pupurea Hort.)基因型为试材,探讨了基因型和活性炭对产胚量的影响。结果表明:产胚量最高的是基因型8902,达到42个/皿,最少的为零;加适量活性炭可以使产胚量提高近3倍。同时,对胚状体进一步再生成苗因素也进行了研究:在培养基中添加1.2%的琼脂浓度再生率最高,达到50.1%;4℃下处理10d可使再生成苗率从45%提高到65%;随胚状体年龄的延长,其再生成株率明显降低,最适的胚龄是20-24d;而培养基B5和MS对小孢子再生率的影响不大。 相似文献
98.
99.
为探讨从紫色小白菜(Brassica campestris L.ssp.chinensis(L.)Makino var.communis Tsen et Lee)叶片中提取花青苷的最佳工艺条件,在超声功率为420 W、40%乙醇和两次超声提取条件下,采用Box-Behnken的中心组合试验设计原理,设计4因素3水平试验,研究了pH、料液比、超声温度、超声时间对花青苷得率的影响。结果表明,紫色小白菜叶片花青苷提取的优化工艺参数为料液比1∶16(pH 2.76),在超声功率为420 W、温度为58℃下超声12 min,花青苷的提取得率可达4.11 mg g–1 DW。 相似文献
100.
Cuttings of Cotinus coggyria cv Royal Purple rooted well in the spring but not at all later in the season. Levels of free and conjugated IAA and ABA were measured in cuttings taken at different times of the year. Hormones were measured in the leaf, the upper stem and the lower stem (rooting zone). In cuttings taken in early June the level of IAA was much higher than that of conjugated IAA. In late July the opposite was found. No significant differences in ABA levels were found although the ABA/IAA ratio changed dramatically. 相似文献