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411.
The ratio of loculus volume to the volume of the entire anther began to increase from the microspore mother cell stage and
reached 32.3% at anthesis. The content of the loculus was examined in Lilium during pollen development and two waves could be distinguished. From the premeiotic stage until the vacuolated microspore
stage, the loculus consisted of neutral polysaccharides, pectins and proteins. These substances originated from tapetal activity
from the premeiotic stage until the young microspore stage. Dictyosomes and rough endoplasmic reticulum seemed to be involved
in tapetal secretion, although, in some mitochondria, vesicles progressively developed as early as premeiosis and increased
until the young microspore stage, which could reveal their involvement in the secretion process. At this stage, numerous cytoplasmic
vesticles containing material similar to the locular material fused with the plasma membrane of the tapetum so that vesicle
content was in contact with the loculus. It seems that tapetal and callose wall degradation at the late tetrad stage may also
have contributed to the production of material in the loculus. From pollen mitosis to anthesis, the anther loculus contained
mainly the pollenkitt which was synthesized in the tapetum between the young microspore stage and the vacuolated microspore
stage. At the young microspore stage, proplastids divided and developed into elaioplasts and smooth endoplasmic reticulum
(SER) increased dramatically. Pollenkitt had a double origin: some droplets were extruded directly from the plastid stroma
through the plastid envelopes; the others were unsaturated lipid globules, which presumably derived from the interaction between
SER saccules and plastids.
Received: 2 September 1997 / Revision accepted: 12 March 1998 相似文献
412.
Gilbert Laporte Luís Lopes François Soumis 《Flexible Services and Manufacturing Journal》1998,10(1):27-42
The purpose of this paper is to develop optimal tool partitioning policies and strip sequencing strategies for a class of flexible manufacturing problems. The problems under consideration involve a large number of operations to be performed by a series of tools on a two-dimensional object. For example, these operations could consist of drilling holes in a metallic sheet. Tools are arranged in a carousel or along a toolbar according to a predetermined sequence. Operations are performed by repeatedly moving the sheet to bring the hole locations under the tool. During each pass, as all operations involving a series of consecutive tools are executed, two main problems are to be solved: (1) how to move the sheet during each pass, (2) how to partition the tools into blocks of consecutive tools. A strip strategy is used to move the sheet. Given this policy, optimal strip widths and tool partitioning policies are determined jointly. Analytical solutions are derived under two metrics corresponding to different operating modes. A numerical example is provided. 相似文献
413.
Laporte SA Boucard AA Servant G Guillemette G Leduc R Escher E 《Molecular endocrinology (Baltimore, Md.)》1999,13(4):578-586
To identify ligand-binding domains of Angiotensin II (AngII) type 1 receptor (AT1), two different radiolabeled photoreactive AngII analogs were prepared by replacing either the first or the last amino acid of the octapeptide by p-benzoyl-L-phenylalanine (Bpa). High yield, specific labeling of the AT1 receptor was obtained with the 125I-[Sar1,Bpa8]AngII analog. Digestion of the covalent 125I-[Sar1,Bpa8]AngII-AT1 complex with V8 protease generated two major fragments of 15.8 kDa and 17.8 kDa, as determined by SDS-PAGE. Treatment of the [Sar1,Bpa8]AngII-AT1 complex with cyanogen bromide produced a major fragment of 7.5 kDa which, upon further digestion with endoproteinase Lys-C, generated a fragment of 3.6 kDa. Since the 7.5-kDa fragment was sensitive to hydrolysis by 2-nitro-5-thiocyanobenzoic acid, we circumscribed the labeling site of 125I-[Sar1,Bpa8]AngII within amino acids 285 and 295 of the AT1 receptor. When the AT1 receptor was photolabeled with 125I-[Bpa1]AngII, a poor incorporation yield was obtained. Cleavage of the labeled receptor with endoproteinase Lys-C produced a glycopeptide of 31 kDa, which upon deglycosylation showed an apparent molecular mass of 7.5 kDa, delimiting the labeling site of 125I-[Bpa1]AngII within amino acids 147 and 199 of the AT1 receptor. CNBr digestion of the hAT1 I165M mutant receptor narrowed down the labeling site to the fragment 166-199. Taken together, these results indicate that the seventh transmembrane domain of the AT1 receptor interacts strongly with the C-terminal amino acid of [Sar1, Bpa8]AngII interacts with the second extracellular loop of the AT1 receptor. 相似文献
414.
PCR-based assays of mendelian polymorphisms from anonymous single-copy nuclear DNA: techniques and applications for population genetics 总被引:5,自引:0,他引:5
This paper outlines a PCR-based approach for population genetics that
offers several advantages over conventional Southern blotting methods for
revealing restriction-fragment-length polymorphisms (RFLPs) in nuclear DNA.
Primers are constructed from clones isolated from a nuclear DNA library,
and these primers subsequently are employed in in vitro syntheses of
homologous regions. Amplified products are then screened directly for RFLPs
by using gel-staining procedures. Population applications for this
PCR-based approach, including potential strengths and weaknesses, are
exemplified by two RFLP data sets generated to estimate (a) male-mediated
gene flow in the green turtle (Chelonia mydas) and (b) geographic
population genetic structure in the American oyster (Crassostrea
virginica). Restriction assays of amplified products from 14 or 15
independent primer pairs in each species revealed polymorphisms at several
loci that proved highly informative in the population genetic analyses. In
general, the Mendelian polymorphisms produced by this PCR-based approach
will provide useful genetic markers for population studies, particularly in
situations where simpler and less expensive allozyme methods have failed,
for whatever reason, to provide adequate information.
相似文献
415.
416.
J. Laporte A. Hallee K. Maghni C. Robidoux P. Borgeat P. Sirois 《Prostaglandins & other lipid mediators》1991,41(3)
A method for the isolation of non-ciliated bronchiolar epithelial (Clara) cells from the guinea pig is described. Following digestion of the lung tissue with Type XXIV protease, the isolated lung cells showed a viability greater than 90 % and contained 3 % of Clara cells. Several cell populations were then separated on the basis of size using 2 centrifugal elutriations. The macrophages and endothelial cells were removed from the Clara cells enriched fractions by differential adherence on Petri dishes. The Clara cell-rich suspension was then further purified by centrifugation on Percoll non-continuous density gradients consisting of 48-52-55 % Percoll solution. The lower interface and the pellet of the non-continuous gradient consisted of approximately 80 % Clara cells. Identification of isolated Clara cells was confirmed by light microscopic observations after nitroblue tetrazolium staining and by ultrastructural characteristic features as observed by electron microscopy. The metabolism of arachidonic acid into prostaglandins and TxB2 by purified Clara cells was examined by enzyme immunoassay (EIA) and leukotriene formation was investigated by reverse phase high performance liquid chromatography (RP-HPLC). Enriched guinea pig Clara cells incubated with arachidonic acid released TxB2, PGE2 and 6-keto PGF1α, but did not produce leukotrienes. These cells could however transform exogenous leukotriene A4 into leukotriene B4. These results suggest that guinea pig Clara cells possess the enzymes of the cyclooxygenase pathway required for TxB2, PGE2 and 6-keto-PGF1α synthesis. Clara cells do not possess the 5-lipoxygenase enzyme but show some leukotriene A4 hydrolase activity since they can produce leukotriene B4 upon incubation with leukotriene A4. 相似文献
417.
Jacek Blazewicz Horst A. Eiselt Gerd Finke Gilbert Laporte Jan Weglarz 《Flexible Services and Manufacturing Journal》1991,4(1):5-16
Due to their increasing applicability in modern industry, flexible manufacturing systems (FMSs), their design, and their control have been studied extensively in the recent literature. One of the most important issues that has arisen in this context is the FMS scheduling problem. This article is concerned with a new model of an FMS system, motivated by the practical application that takes into account both machine and vehicle scheduling. For the case of a given machine schedule, a simple polynomial-time algorithm is presented that checks the feasibility of a vehicle schedule and constructs it whenever one exists. Then a dynamic programming approach to construct optimal machine and vehicle schedules is proposed. This technique results in a pseudopolynomialtime algorithm for a fixed number of machines. 相似文献
418.
Emilie Julio Frédéric Laporte Stéphanie Reis Christophe Rothan François Dorlhac de Borne 《Molecular breeding : new strategies in plant improvement》2008,21(3):369-381
Cultivated tobacco produces secondary alkaloids involved in the formation of nitrosamines with health concerns. The recent
identification of target genes in nicotine and nornicotine biosynthetic pathways now allows biotechnological approaches for
their control. We demonstrate here that mutation breeding can be used as an alternative to genetically modified (GM) plants
for generating nornicotine-free tobacco. Ten alleles of the NtabCYP82E4 gene (nicotine N-demethylase) were identified by screening 1,311 M2 families of tobacco ethylmethane sulphonate (EMS) mutants. Alkaloid analysis
indicated that the nornicotine contents of homozygous M2 plants carrying nonsense or missense alleles of NtabCYP82E4 were very low or near-null. Backcrossing with tobacco elite varieties yielded BC1 plants phenotypically undistinguishable
from parental lines. This major objective of tobacco breeders in the last few decades could be reached in a period of less
than 1.5 years, including the creation of highly mutagenised tobacco mutant collections and the detection of mutated alleles
using a simple and versatile detection technology (capillary electrophoresis-single strand conformation polymorphism, CE-SSCP)
accessible to most breeding companies and crop species. 相似文献
419.
Cellular signal transduction is dynamic, with signaling proteins continually associating and dissociating into and from protein complexes. Here we present a fluorescence recovery after photobleaching technique to determine the lifetime of protein complexes on intracellular vesicles. We use Bayesian inference based on a model that includes the diffusion of cytosolic proteins and their interaction with membrane-bound receptors. Our analysis is general: we incorporate prior information on protein diffusion, measurement error in determining fluorescence intensities, corrections for photobleaching, and variation in the concentration of receptors between vesicles. We apply our method to the complexes formed on endosomes by G-protein-coupled receptors and the protein β-arrestin. The lifetime of these complexes determines the recycling rate of the receptors. We find in mammalian cells that the bradykinin type 2 receptor and β-arrestin2 complex has a lifetime of ∼2 min, while the angiotensin II type 1A receptor and β-arrestin2 complex has a lifetime of ∼6 min. As well as allowing quantitative comparisons between experiments, our method provides in vivo parameters for systems biology simulations of signaling networks. 相似文献
420.
Fukami M Wada Y Okada M Kato F Katsumata N Baba T Morohashi K Laporte J Kitagawa M Ogata T 《The Journal of biological chemistry》2008,283(9):5525-5532
Although chromosome X open reading frame 6 (CXorf6) has been shown to be a causative gene for hypospadias, its molecular function remains unknown. To clarify this, we first examined CXorf6 protein structure, identifying homology to mastermind-like 2 (MAML2) protein, which functions as a co-activator in canonical Notch signaling. Transactivation analysis for wild-type CXorf6 protein by luciferase assays showed that CXorf6 significantly transactivated the promoter of a noncanonical Notch target gene hairy/enhancer of split 3 (Hes3) without demonstrable DNA-binding capacity. Transactivation analysis was also performed for the previously described three apparently pathologic nonsense mutations, indicating that E124X and Q197X proteins had no transactivation function, whereas R653X protein retained a nearly normal transactivation function. Subcellular localization analysis revealed that wild-type and R653X proteins co-localized with MAML2 protein in nuclear bodies, whereas E124X and Q197X proteins were incapable of localizing to nuclear bodies. Thus, further studies were performed for R653X, revealing the occurrence of nonsense mediated mRNA decay in vivo. Next, transient knockdown of CXorf6 was performed using small interfering RNA, showing reduced testosterone production in mouse Leydig tumor cells. Furthermore, steroidogenic factor 1 (SF1) protein bound to a specific sequence in the upstream of the CXorf6 coding region and exerted a transactivation activity. These results suggest that CXorf6 transactivates the Hes3 promoter, augments testosterone production, and contains the SF1 target sequence, thereby providing the first clue to clarify the biological role of CXorf6. We designate CXorf6 as MAMLD1 (mastermind-like domain-containing 1) based on its characteristic structure. 相似文献