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161.
Breaking the apple embryo dormancy by nitric oxide involves the stimulation of ethylene production 总被引:4,自引:0,他引:4
Mature seeds of apple (Mallus domestica Borb. cv. Antonówka) are dormant and do not germinate unless their dormancy is removed by several weeks of moist-cold treatment.
We investigated the effect of short-term (3 h) nitric oxide (NO) pretreatment on breaking of apple embryonic dormancy expressed
as inhibition of germination and morphological abnormalities of young seedlings. Imbibition of embryos isolated from dormant
apple seeds with sodium nitroprusside (SNP) or S-nitroso,N-acetyl penicillamine (SNAP) as NO donors resulted in enhanced germination. Moreover, NO treatment removed morphological abnormalities
of seedlings developing from dormant embryo. The NO scavenger 2-(4-carboxyphenyl)-4,4,5,5-teramethylimidazoline-1-oxyl-3 oxide
(cPTIO) removed the above effects. NO-mediated breaking of embryonic dormancy correlated well with enhanced ethylene production.
Inhibitor of ethylene synthesis (AOA) reversed the stimulatory effect of NO donors on embryo germination. Additionally SNP
reduced embryo sensitivity to exogenously applied ABA ensuing dormancy breakage. We can conclude that NO acts as a regulatory
factor included in the control of apple embryonic dormancy breakage by stimulation of ethylene biosynthesis. 相似文献
162.
163.
Szkudelski T 《American journal of physiology. Endocrinology and metabolism》2007,293(4):E901-E907
Resveratrol is a stilbene present in different plant species and exerting numerous beneficial effects, including prevention of diabetes and attenuation of some diabetic complications. Its inhibitory effect on insulin secretion was recently documented, but the exact mechanism underlying this action remains unknown. Experiments employing diazoxide and a high concentration of K(+) revealed that, in depolarized pancreatic islets incubated for 90 min with resveratrol (1, 10, and 100 microM), insulin secretion stimulated by glucose and leucine was impaired. The attenuation of the insulin secretory response to 6.7 mM glucose was not abrogated by blockade of intracellular estrogen receptors and was found to be accompanied by diminished islet glucose oxidation, enhanced lactate production, and reduced ATP levels. Glucose-induced hyperpolarization of the mitochondrial membrane was also reduced in the presence of resveratrol. Moreover, in depolarized islets incubated with 2.8 mM glucose, activation of protein kinase C or protein kinase A potentiated insulin release; however, under these conditions, resveratrol was ineffective. Further studies also revealed that, under conditions of blocked voltage-dependent calcium channels, the stilbene reduced insulin secretion induced by a combination of glucose with forskolin. These data demonstrate that resveratrol 1) inhibits the amplifying pathway of insulin secretion, 2) exerts an insulin-suppressive effect independently of its estrogenic/anti-estrogenic activity, 3) shifts islet glucose metabolism from mitochondrial oxidation to anaerobic,4) fails to abrogate insulin release promoted without metabolic events, and 5) does not suppress hormone secretion as a result of the direct inhibition of Ca(2+) influx through voltage-dependent calcium channels. 相似文献
164.
Frense D 《Applied microbiology and biotechnology》2007,73(6):1233-1240
Taxol is a valuable plant-derived drug showing activity against various cancer types. Worldwide efforts had been made to overcome
the supply problem, because the supply by isolation from the bark of the slow-growing yew trees is limited. Plant cell cultures
as well as chemical and biotechnological semisynthesis are processes, which are intensively investigated for the production
of taxanes paclitaxel (Taxol) and docetaxel (Taxotere) in the last few years. This article provides a comparison of the current
research on taxane biosynthesis and production in yew cell cultures. 相似文献
165.
Hait NC Bellamy A Milstien S Kordula T Spiegel S 《The Journal of biological chemistry》2007,282(16):12058-12065
Sphingosine 1-phosphate (S1P), a potent lipid mediator, is a ligand for a family of five G protein-coupled receptors (S1P(1-5)) that have been shown to regulate a variety of biological responses important for cancer progression. The cellular level of S1P is low and tightly regulated in a spatio-temporal manner through its synthesis catalyzed by two sphingosine kinases, denoted SphK1 and SphK2. Many stimuli activate and translocate SphK1 to the plasma membrane by mechanisms that are dependent on its phosphorylation. Much less is known about activation of SphK2. Here we demonstrate that epidermal growth factor (EGF) as well as the protein kinase C activator, phorbol ester, induce rapid phosphorylation of hSphK2 which was markedly reduced by inhibition of MEK1/ERK pathway. Down-regulation of ERK1 blocked EGF-induced phosphorylation of SphK2. Recombinant ERK1 phosphorylated hSphK2 in vitro and increased its enzymatic activity. ERK1 also was found to be in a complex with hSphK2 in vivo. Site-directed mutagenesis indicated that hSphK2 is phosphorylated on Ser-351 and Thr-578 by ERK1 and that phosphorylation of these residues is important for EGF-stimulated migration of MDA-MB-453 cells. These studies provide the first clues to the mechanism of agonist-mediated SphK2 activation and enhance understanding of the regulation of SphK2 activity by phosphorylation and its role in movement of human breast cancer cells toward EGF. 相似文献
166.
Changes in water status and water distribution in maturing lupin seeds studied by MR imaging and NMR spectroscopy 总被引:2,自引:0,他引:2
The changes in water distribution in maturing lupin (Lupinus luteus L.) seeds were visualized with magnetic resonance imaging (MRI). MRI data showed local inhomogeneities of water distribution inside the seed. At the late seed-filling stage the most intense signal was detected in the seed coat and the outer parts of cotyledons in the hilum area, but during maturation drying the decline in MR image intensity was faster in the outer part of the seed than in the central part. The changes in water status were characterized by NMR spectroscopy. Analyses of T(2) relaxation times revealed a three-component water proton system in maturing lupin seeds. Three populations of protons found during seed maturation, each with a different magnetic environment causing a different relaxation rate, were correlated with three fractions of water (structural, intracellular, and extracellular) that were observed during seed germination. This study provides evidence that lupin seeds have similar states of the different water components with regard to seed moisture content at two distinct physiological stages, seed maturation and germination. The unique feature of maturing lupin seeds is the presence of the high (1)H-NMR signal in areas corresponding to the vascular bundles. Tissue localization of dehydrins showed the presence of dehydrin protein in the area of vascular tissue. An anti-dehydrin antibody detected three polypeptides in lupin embryos with molecular masses of 73, 43 and 28 kDa, respectively. The temporal pattern of dehydrin protein accumulation correlates well with seed desiccation. 相似文献
167.
Growth and Mycorrhizal Community Structure of Pinus sylvestris Seedlings following the Addition of Forest Litter
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Algis Au
ina Maria Rudawska Tomasz Leski Audrius Skridaila Edvardas Riepas Michal Iwanski 《Applied microbiology》2007,73(15):4867-4873
We report the effects of pine and oak litter on species composition and diversity of mycorrhizal fungi colonizing 2-year-old Pinus sylvestris L. seedlings grown in a bare-root nursery in Lithuania. A layer of pine or oak litter was placed on the surface of the nursery bed soil to mimic natural litter cover. Oak litter amendment appeared to be most favorable for seedling survival, with a 73% survival rate, in contrast to the untreated mineral bed soil (44%). The concentrations of total N, P, K, Ca, and Mg were higher in oak growth medium than in pine growth medium. Relative to the control (pH 6.1), the pH was lower in pine growth medium (5.8) and higher in oak growth medium (6.3). There were also twofold and threefold increases in the C content of growth medium with the addition of pine and oak litter, respectively. Among seven mycorrhizal morphotypes, eight different mycorrhizal taxa were identified: Suillus luteus, Suillus variegatus, Wilcoxina mikolae, a Tuber sp., a Tomentella sp., Cenococcum geophilum, Amphinema byssoides, and one unidentified ectomycorrhizal symbiont. Forest litter addition affected the relative abundance of mycorrhizal symbionts more than their overall representation. This was more pronounced for pine litter than for oak litter, with 40% and 25% increases in the abundance of suilloid mycorrhizae, respectively. Our findings provide preliminary evidence that changes in the supply of organic matter through litter manipulation may have far-reaching effects on the chemistry of soil, thus influencing the growth and survival of Scots pine seedlings and their mycorrhizal communities. 相似文献
168.
Sipak-Szmigiel O Ronin-Walknowska E Cybulski C Plonka T Lubiński J 《Folia histochemica et cytobiologica / Polish Academy of Sciences, Polish Histochemical and Cytochemical Society》2007,45(Z1):S137-S141
It can be supposed that relation between HLA-G polymorphism and sHLA-G protein expression are associated with successful embryo implantation and pregnancy maintenance. The aim of the study was the estimation specific differences in expression of sHLA-G and sHLA- class I antigens in women with reproductive failure in comparison with fertile women. The study sample enrolled 80 women, divided into 2 groups. The study group (B) enrolled 60 women with reproductive failure including 20 women with 3 recurrent spontaneous abortions in the first trimester of pregnancy (RSA), 20 women with empty sac (ES) and 20 women with 3 consecutive in-vitro fertilization failures (IVFf). The control group (C) enrolled 20 fertile women with at least 2 children. Soluble HLA- class I antigens (sHLA-I) and soluble HLA-G (sHLA-G) were determined using ELISA test kits from IBio Vendor Labolatory Medicine, Inc. HLA-G allele found in individuals in our study were identified by comparing the obtained bp sequences of exon 2., 3. and 4. with bp sequences of HLA-G antigen published at the Nolan Research Institute website. The highest concentration of sHLA-I is noted among women with HLA-G 10401 allele which differed significantly for the mean sHLA-I concentration calculated for all the remaining alleles (p<0.0001). The most prevalent alleles were: HLA-G 10101, 10102 and 10108 with sHLA-I concentrations among women bearing those alleles significantly lower in comparison to the HLA-G 10401 carriers (p<0.001). Allele 10101 and 10102 was related to the lower significantly plasma sHLA-I concentrations than 10108 allele (p<0.02). Lowest mean sHLA-G values were observed in the IVFf group with significant difference from the remaining groups (p<0.05). To conclude, sHLA-G molecules is associated to certain HLA-G alleles and imply that sHLA-G levels are under genetic control. Low concentration sHLA-G seems to be prognostically important in IVF failure. 相似文献
169.
170.
Interactive playback experiments were used to study the signal value to the corn bunting, Miliaria calandra, of alternating and overlapping singing. We subjected 15 males to two stimuli that differed in the temporal pattern of song
playback (alternating or overlapping). We measured eight characteristics of the males’ response in two categories—song output
and movements. Overlapping and alternating playback elicited a similar song response, characteristic of highly aroused males.
Song response correlated positively with males’ singing activity before playback, irrespective of stimulus. There were significant
differences between latency of approach to the loudspeaker and number of flights. Birds approached the loudspeaker more quickly
and spent more time close to it when playback alternated with their songs. The results suggest overlapping song could be interpreted
as a stronger threat but elicits a more cautious, rather than stronger, response than the alternating pattern. Males were
found to shorten songs during the playback compared with songs sung before and after stimulation. The only predictor of degree
of song shortening was song activity before the playback began. It should, therefore, be regarded as a signal which is related
to escalated, close-distance counter-singing. 相似文献