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111.
A soluble enzyme, extracted from tobacco cell-suspension cultures 24 h after treatment with 100 μM methyl jasmonate, has been shown to synthesize acetovanillone (apocynin) from feruloyl-CoA in the presence of NAD. The enzyme displayed Michaelis-Menten kinetics with apparent Km values of 5.6 μM for feruloyl-CoA and 260 μM for NAD and exhibited very high specificity for its substrates. The increase in acetovanillone synthase activity was followed by an increase in the concentration of both acetovanillone and acetosyringone in the culture medium. No intermediate could be detected when analysing the reaction medium by HPLC during the formation of acetovanillone in cell-free extracts. The apparent molecular mass estimated by gel permeation on an FPLC column was ca. 79 kDa. To our knowledge, this is the first report of an enzymic system catalysing the synthesis of an acetophenone. This work demonstrates that the biosynthesis of acetophenones in tobacco proceeds from hydroxycinnamic acids through a CoA-dependent β-oxidation pathway. Interestingly in methyl jasmonate-treated cells, which synthesize very large amounts of hydroxycinnamoylputrescines, inhibition of the synthesis of these conjugates increased the concentration of acetovanillone and acetosyringone in the culture medium, suggesting that the two metabolic pathways can compete for their common precursors, i.e. hydroxycinnamoyl-CoA thioesters. 相似文献
112.
To improve the accumulation of recombinant human epidermal growth factor (hEGF) in transgenic tobacco, a highly effective
vector was constructed and transformed via Agrobacterium tumefaciens. The hEGF content in transgenic tobacco was up to 0.3% of the total soluble protein. Using the Vero E6 cell expansion assay
and the MTT method for cell proliferation, hEGF produced by transgenic tobacco significantly stimulated Vero E6 cell expansion
and proliferation, the same as commercial hEGF products. 相似文献
113.
García-Maroto F Garrido-Cárdenas JA Michaelson LV Napier JA Alonso DL 《Plant molecular biology》2007,64(3):241-250
114.
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116.
Moyano E Palazón J Bonfill M Osuna L Cusidó RM Oksman-Caldentey KM Piñol MT 《Journal of plant physiology》2007,164(4):521-524
Hyoscyamine-6beta-hydroxylase (H6H) catalyses the conversion of hyoscyamine into its epoxide scopolamine, a compound with a higher added value in the pharmaceutical market than hyoscyamine. We report the establishment of tobacco cell cultures carrying the Hyoscyamus muticus h6h gene under the control of the promoter CAMV 35S. The cell cultures were derived from hairy roots obtained via genetically modified Agrobacterium rhizogenes carrying the pRi and pLAL21 plasmids. The cultures were fed with hyoscyamine, and 4 weeks later the amount of scopolamine produced was quantified by HPLC. The transgenic cell suspension cultures showed a considerable capacity for the bioconversion of hyoscyamine into scopolamine, and released it to the culture medium. Although the scale-up from shake-flask to bioreactor culture usually results in reduced productivities, our transgenic cells grown in a 5-L turbine stirred tank reactor in a batch mode significantly increased the scopolamine accumulation. 相似文献
117.
Tettamanti G Grimaldi A Casartelli M Ambrosetti E Ponti B Congiu T Ferrarese R Rivas-Pena ML Pennacchio F Eguileor Md 《Cell and tissue research》2007,330(2):345-359
We have analyzed midgut development during the fifth larval instar in the tobacco budworm Heliothis virescens. In prepupae, the midgut formed during larval instars undergoes a complete renewal process. This drastic remodeling of the
alimentary canal involves the destruction of the old cells by programmed cell-death mechanisms (autophagy and apoptosis).
Massive proliferation and differentiation of regenerative stem cells take place at the end of the fifth instar and give rise
to a new fully functioning epithelium that is capable of digesting and absorbing nutrients and that is maintained throughout
the subsequent pupal stage. Midgut replacement in H. virescens is achieved by a balance between this active proliferation process and cell-death mechanisms and is different from similar
processes characterized in other insects.
This work was supported by FAR 2006 (University of Insubria) to G.T., by a MIUR-FIRB-COFIN grant (no. RBNE01YXA8/2004077251),
and by the Centro Grandi Attrezzature (University of Insubria). 相似文献
118.
Bao-Li Qiu Paul J. De Barro Yu-Rong He Shun-Xiang Ren 《Biocontrol Science and Technology》2007,17(8):823-839
The host instar preferences of Encarsia bimaculata and Eretmocerus sp. nr. furuhashii parasitizing Bemisia tabaci and their development on four host plants, collard, eggplant, cucumber and tomato, were studied in the laboratory. Both of the parasitoids accepted all nymphal stages of B. tabaci, but E. bimaculata preferred third and fourth instars while Er. sp. nr. furuhashii preferred second and third instars under both choice and no choice conditions. Regardless of host stage parasitized, adults of parasitoids emerged only from fourth instars. When given the simultaneous choice of all instars, E. bimaculata reduced parasitization of first and second instars (3.73 and 4.76%, respectively) while increasing parasitization of third and fourth instars (5.44 and 6.93%, respectively), in contrast Er. sp. nr. furuhashii increased its parasitization of second and third instar nymphs (1.27 and 3.17%, respectively) and decreased that of first and fourth instars (7.0 and 3.06%, respectively). Host plants did not significantly influence instar preference for either parasitoid. Developmental periods of both the parasitoids from egg to adult emergence were longest when first instars were parasitized and shortest when fourth instars were selected. Parasitoid developmental time was generally shorter on glabrous plants than on hirsute plants. 相似文献
119.
Zeidler R Albermann K Lang S 《Apoptosis : an international journal on programmed cell death》2007,12(11):1927-1943
Cigarette smoking is associated with a plethora of different diseases. Nicotine is the addictive component of cigarette but
also acts onto cells of the non-neuronal system, including immune effector cells. Although nicotine itself is usually not
referred to as a carcinogen, there is ongoing debate whether nicotine functions as a ‘tumor enhancer.' By binding to nicotinic
acetylcholine receptors, nicotine deregulates essential biological processes like angiogenesis, apoptosis, and cell-mediated
immunity. Apoptosis plays critical roles in a wide variety of physiologic processes during fetal development and in adult
tissue and is also a fundamental aspect of the biology of malignant diseases. This review provides an overlook how nicotine
influences apoptotic processes and is thus directly involved in the etiology of pathological conditions like cancer and obstructive
diseases. 相似文献
120.
Orange- to red-colored flowers are difficult to produce by conventional breeding techniques in some floricultural plants.
This is due to the deficiency in the formation of pelargonidin, which confers orange to red colors, in their flowers. Previous
researchers have reported that brick-red colored flowers can be produced by introducing a foreign dihydroflavonol 4-reductase
(DFR) with different substrate specificity in Petunia hybrida, which does not accumulate pelargonidin pigments naturally. However, because these experiments used dihydrokaempferol (DHK)-accumulated
mutants as transformation hosts, this strategy cannot be applied directly to other floricultural plants. Thus in this study,
we attempted to produce red-flowered plants by suppressing two endogenous genes and expressing one foreign gene using tobacco
as a model plant. We used a chimeric RNAi construct for suppression of two genes (flavonol synthase [FLS] and flavonoid 3′-hydroxylase [F3′H]) and expression of the gerbera DFR gene in order to accumulate pelargonidin pigments in tobacco flowers. We successfully produced red-flowered tobacco plants
containing high amounts of additional pelargonidin as confirmed by HPLC analysis. The flavonol content was reduced in the
transgenic plants as expected, although complete inhibition was not achieved. Expression analysis also showed that reduction
of the two-targeted genes and expression of the foreign gene occurred simultaneously. These results demonstrate that flower
color modification can be achieved by multiple gene regulation without use of mutants if the vector constructs are designed
resourcefully.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献