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991.
Hydrated thalli of the lichen Lobaria pulmonaria were either preconditioned to dim irradiance (DI, 5 μmol m−2 s−1) or medium irradiance (MI, 200 μmol m−2 s−1) for 6 h. After this 6 h period, the thalli were allowed to desiccate under the two respective irradiances. Thereafter, these
dry lichens were exposed to high irradiance (HI, 1 000 μmol m−2 s−1) for 60 h. After this HI treatment, the maximal photochemical quantum yield (FV/FM) and the de-epoxidation state of xanthophyll cycle pigments (DEPS) were highest in thalli preconditioned to MI. Hence irradiance
in the last hydrated period before sampling is significant for the physiological state of lichens. A standardized irradiance
pre-treatment before start of experiments is recommended. 相似文献
992.
Glycine betaine improves thylakoid membrane function of tobacco leaves under low-temperature stress 总被引:1,自引:0,他引:1
Glycine betaine (GB) is an effective compatible solute that improves the tolerance in plants to various stresses. We investigated
the effects of 2 mM GB applied to the roots of a tobacco (Nicotiana tabacum L.) cultivar on enhancing photosynthesis under low-temperature (LT) stress (5/5 °C, 12/12 h, 300 μmol m−2 s−1) and in the subsequent recovery (25/18 °C) from the stress. The net photosynthetic rate, intrinsic efficiency measured as
the ratio of variable to maximum fluorescence, and actual efficiency of the photochemistry of photosystem 2 as well as the
ATPase activity in the thylakoid membrane decreased, and a distinct K step in the fluorescence transient O-J-I-P appeared
under cold stress. Exogenous GB alleviated the decrease in all these parameters. The LT-stress induced the accumulation of
33–66 kDa polypeptides and decreased the proportion of unsaturated fatty acids in the thylakoid membrane. In plants subjected
to LT-stress, GB protected these polypeptides from damage and enhanced the proportion of unsaturated fatty acids. An increase
in non-radiative energy dissipation (NPQ) may be involved in the improvement of the function of the thylakoid membrane by
GB since exogenous GB protected violaxanthin de-epoxidase and enhanced NPQ. 相似文献
993.
Responses of the resurrection plant <Emphasis Type="Italic">Haberlea rhodopensis</Emphasis> to high irradiance 总被引:1,自引:0,他引:1
The effect of high irradiance (HI) during desiccation and subsequent rehydration of the homoiochlorophyllous desiccation-tolerant
shade plant Haberlea rhodopensis was investigated. Plants were irradiated with a high quantum fluence rate (HI; 350 μmol m−2 s−1 compared to ca. 30 μmol m−2 s−1 at the natural rock habitat below trees) and subjected either to fast desiccation (tufts dehydrated with naturally occurring
thin soil layers) or slow desiccation (tufts planted in pots in peat-soil dehydrated by withholding irrigation). Leaf water
content was 5 % of the control after 4 d of fast and 19 d of slow desiccation. Haberlea was very sensitive to HI under all conditions. After 19 d at HI, even in well-watered plants there was a strong reduction
of rates of net photosynthesis and transpiration, contents of chlorophyll (Chl) and carotenoids, as well as photosystem 2
activity (detected by the Chl fluorescence ratio RFd). Simultaneously, the blue/red and green/red fluorescence ratios increased considerably suggesting increased synthesis of
polyphenolic compounds. Desiccation of plants in HI induced irreversible changes in the photosynthetic apparatus and leaves
did not recover after rehydration regardless of fast or slow desiccation. Only young leaves survived desiccation. 相似文献
994.
To investigate how excess excitation energy is dissipated in a ribulose-1,5-bisphospate carboxylase/oxygenase activase antisense
transgenic rice with net photosynthetic rate (P
N) half of that of wild type parent, we measured the response curve of P
N to intercellular CO2 concentration (C
i), electron transport rate (ETR), quantum yield of open photosystem 2 (PS2) reaction centres under irradiation (Fv′/Fm′), efficiency of total PS2 centres (ΦPS2), photochemical (qP) and non-photochemical quenching (NPQ), post-irradiation transient increase in chlorophyll (Chl) fluorescence (PITICF), and
P700+ re-reduction. Carboxylation efficiency dependence on C
i, ETR at saturation irradiance, and Fv′/Fm′, ΦPS2, and qP under the irradiation were significantly lower in the mutant. However, NPQ, energy-dependent quenching (qE), PITICF, and P700+ re-reduction were significantly higher in the mutant. Hence the mutant down-regulates linear ETR and stimulates cyclic electron
flow around PS1, which may generate the ΔpH to support NPQ and qE for dissipation of excess excitation energy. 相似文献
995.
Photosynthesis and photosystem 2 efficiency of two salt-adapted halophytic seashore <Emphasis Type="Italic">Cakile maritima</Emphasis> ecotypes 总被引:1,自引:1,他引:0
W. Megdiche K. Hessini F. Gharbi C. A. Jaleel R. Ksouri C. Abdelly 《Photosynthetica》2008,46(3):410-419
The effects of salinity (0–400 mM NaCl, marked S0, S100, S200, and S400) on growth, photosynthesis, photosystem 2 (PS2) efficiency, ion relations, and pigment contents were studied in two seashore
Cakile maritima ecotypes (Tabarka and Jerba, respectively, sampled from humid and arid bioclimatic areas). Growth of Jerba plants was improved
at S100 as compared to S0. Tabarka growth was inhibited by salinity at all NaCl concentrations. Leaf sodium and chloride concentrations increased with
medium salinity and were higher in Jerba than in Tabarka plants. Chlorophyll content, net photosynthetic rate, stomatal conductance
(g
s), and intracellular CO2 concentration were stimulated at moderate salinity (S100) in Jerba plants and inhibited at higher salt concentrations in both ecotypes: g
s was the most reduced parameter. The maximum quantum efficiency of PS2 (Fv/Fm), quantum yield, linear electron transport rate, and efficiency of excitation energy capture by open PS2 reaction centres
showed no significant changes with increasing salt concentration in Jerba plant and were decreased in Tabarka subjected to
S400. However, the efficiency of dissipation of excess photon energy in the PS2 antenna was maintained in Jerba and was increased
in Tabarka plants challenged with S400. Hence the relative salt tolerance of Jerba was associated with a better ability to use Na+ and Cl− for osmotic adjustment, the absence of pigment degradation, and the concomitant PS2 protection from photodamage. 相似文献
996.
997.
998.
双色荧光杂交芯片在近交系小鼠遗传监测中的应用 总被引:2,自引:0,他引:2
应用一种新的高通量SNP检测方法-双色荧光杂交芯片技术进行近交系小鼠遗传监测。应用双色荧光杂交芯片技术对4个品系近交系小鼠的多个基因组DNA样本进行SNP分型,整合6个SNP位点的芯片杂交信息,对样本所属品系进行判断。研究结果表明SNP检测方法-双色荧光杂交芯片技术能够对选定的6个SNP位点进行高准确率分型;双色荧光杂交芯片技术是一种高通量SNP检测的良好工具,适合于对少量近交系品系来源的大样本量小鼠进行遗传污染监测和品系鉴定,并具有扩大应用的潜力。 相似文献
999.
Genomic DNA was extracted from wild-type Escherichia coli strains ATCC 35321 and 8677. The lac Z gene was amplified and used as a template for in vitro synthesis of β-galactosidase. In addition the enzyme was synthesized
in vitro with a C-terminal His6 tag. The enzyme expression was also induced in these strains using isopropyl-β-D-galactoside. Single enzyme molecule assays were performed using a capillary electrophoresis-based protocol on both the in
vitro and in vivo synthesized enzyme. In vivo produced enzyme from strains 35321 and 8677 showed average combined turnover
numbers for the 4 active sites of the individual enzyme molecules of 53,400 ± 18,400 (N = 139) and 34,300 ± 17,800 min−1 (N = 181) respectively. Average combined turnover numbers of 35,800 ± 20,900 (N = 302) and 31,700 ± 17,700 min−1 (N = 315) were obtained respectively for the in vitro synthesized enzyme from strain 35321 with the absence and presence of
a C-terminal His6 tag. For strain 8677, the average combined turnover numbers were 29,000 ± 17,900 (N = 288) and 25,200 ± 12,600 min−1 (N = 240) respectively for the absence and presence of a C-terminal His6 tag. The average combined turnover numbers of the enzyme from both strains synthesized in vivo and in vitro and with the
presence and absence of a His6 tag were found to differ significantly. This indicates that the in vivo and in vitro produced enzymes are not identical and
the presence of a C-terminal His6 tag alters the activity of β-galactosidase. 相似文献
1000.
蒙古栎和紫椴幼苗对光环境转变的光合作用响应 总被引:2,自引:1,他引:1
比较研究了从温室5%光强转到10%、30%和100%光强处理下,蒙古栎(Quercus mongolica)和紫椴(Tilia amurensis)幼苗的光合能力和叶绿素荧光的响应,揭示了两个树种对光环境变化的不同适应情况及其光保护机制。结果表明,光强转换后两种幼苗都发生了严重光抑制,蒙古栎幼苗的最大光化学效率(Fv/Fm)在光强转变后第3天降到最低(0.52),紫椴幼苗在光强转变后第1天就降到了最低(0.67),蒙古栎降低幅度明显高于紫椴。之后随着光适应时间的延长逐渐恢复到原有水平,说明短时期的光抑制没有对两种幼苗的光合机构造成光损伤;从不同光照条件来看,无论是最大净光合速率(Pmax),还是实际光化学效率(ФPSⅡ),2种幼苗均为30%光强下的值高于10%和100%光强,说明过低或过高的光强都不利于幼苗的生长发育,只有适当的中光才利于幼苗的生长发育;与30%光强相比,蒙古栎幼苗100%光强下Pmax、Fv/Fm、ФPSⅡ、NPQ的变化幅度远大于紫椴幼苗,表明高光强对蒙古栎幼苗的影响要大于紫椴;100%光强下,2种幼苗均通过大量增加非光化学淬灭(NPQ)、类胡萝卜素和叶绿素之比(Car/Chl)耗散过剩光能,降低单位鲜重叶绿素含量(Chl)以减少光能吸收,避免了光合机构光破坏。 相似文献