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201.
Herbaceous vegetation pattern and soil properties around individual Juniperus pinchotii Sudw. trees were studied on a grazed and a relict grassland in western Texas. Herb standing crop and soil samples were obtained under the canopy, at canopy edge, and beyond the canopy edge of three to five trees on each of four dates. Standing crop was lowest midway between the bole and canopy edge. Soil organic matter was highest under juniper canopies on both sites. Soil pH and P were not related to distance from tree bole on either site. Herbaceous pattern from under the canopy to canopy edge apparently depended primarily on individual tree size. However, trees had little influence on herbaceous vegetation pattern 3-5 m beyond canopy edge, a response attributed to distance-independent interaction between J. pinchotii and herbaceous vegetation. Given a shallow soil underlain by indurated caliche and tree densities ranging from 288 (relict size) to 2123 (grazed site) trees/ha, the interaction between J. pinchotii and herbaceous vegetation did not change over a distance of 3-5 m from tree canopy edge in our study area. 相似文献
202.
203.
J M Allen N D Christofides G Gornacz K Tatemoto J H Baron S R Bloom 《Experientia》1983,39(10):1129-1131
PHI, infused in man, achieved plateau plasma levels of 297 pmoles/1. The plasma half life was 3.1 min, metabolic clearance rate was 16.4 ml/kg/min and estimated volume of distribution was 73.2 ml/kg. No subjective side effects were noted during the infusion and there was no significant alteration in submaximal pentagastrin stimulated gastric acid or pepsin secretion. 相似文献
204.
Mutations in LGI1 cause autosomal-dominant partial epilepsy with auditory features. 总被引:28,自引:0,他引:28
Sergey Kalachikov Oleg Evgrafov Barbara Ross Melodie Winawer Christie Barker-Cummings Filippo Martinelli Boneschi Chang Choi Pavel Morozov Kamna Das Elita Teplitskaya Andrew Yu Eftihia Cayanis Graciela Penchaszadeh Andreas H Kottmann Timothy A Pedley W Allen Hauser Ruth Ottman T Conrad Gilliam 《Nature genetics》2002,30(3):335-341
The epilepsies are a common, clinically heterogeneous group of disorders defined by recurrent unprovoked seizures. Here we describe identification of the causative gene in autosomal-dominant partial epilepsy with auditory features (ADPEAF, MIM 600512), a rare form of idiopathic lateral temporal lobe epilepsy characterized by partial seizures with auditory disturbances. We constructed a complete, 4.2-Mb physical map across the genetically implicated disease-gene region, identified 28 putative genes (Fig. 1) and resequenced all or part of 21 genes before identifying presumptive mutations in one copy of the leucine-rich, glioma-inactivated 1 gene (LGI1) in each of five families with ADPEAF. Previous studies have indicated that loss of both copies of LGI1 promotes glial tumor progression. We show that the expression pattern of mouse Lgi1 is predominantly neuronal and is consistent with the anatomic regions involved in temporal lobe epilepsy. Discovery of LGI1 as a cause of ADPEAF suggests new avenues for research on pathogenic mechanisms of idiopathic epilepsies. 相似文献
205.
Transgenes as probes for active chromosomal domains in mouse development 总被引:32,自引:0,他引:32
Embryonic development entails a well defined temporal and spatial programme of gene expression, which may be influenced by active chromosomal domains. These chromosomal domains can be detected using transgenes which integrate randomly throughout the genome, as their expression can be affected by chromosomal position. Position effects are probably exerted most strongly on transgenes that do not contain strong promoters, enhancers or other modulating sequences. Here we have systematically explored position effects using a transgene with the weak herpes-simplex-virus thymidine-kinase promoter, linked to the readily visualized lacZ indicator gene (HSV-TK-lacZ). Each transgenic fetus with detectable expression displayed a unique lacZ staining pattern. Thus expression of this construct is apparently dictated entirely by its chromosomal position, without any construct specificity. Furthermore the transgene is faithfully transmitted to subsequent generations, allowing for systematic mapping of changes in expression during development and in adult life. These results demonstrate that transgenes can indeed be powerful tools to probe the genome for active chromosomal regions, with the potential for identifying endogenous genes involved in organogenesis and pattern formation. 相似文献
206.
John Robin Allen 《Foundations of Science》1995,1(4):571-576
Varia
Constitution of the Association for the Foundations of Science, Language and Cognition 相似文献207.
R. T. Allen M. W. Cluck D. K. Agrawal 《Cellular and molecular life sciences : CMLS》1998,54(5):427-445
Apoptosis is an essential and highly conserved mode of cell death that is important for normal development, host defense
and suppression of oncogenesis. Faulty regulation of apoptosis has been implicated in degenerative conditions, vascular diseases,
AIDS and cancer. Among the numerous proteins and genes involved, members of the Bcl-2 family play a central role to inhibit
or promote apoptosis. In this article, we present up-to-date information and recent discoveries regarding biochemical functions
of Bcl-2 family proteins, positive and negative interactions between these proteins, and their modification and regulation
by either proteolytic cleavage or by cytosolic kinases, such as Raf-1 and stress-activated protein kinases. We have critically
reviewed the functional role of caspases and the consequences of cleaving key substrates, including lamins, poly(ADP ribose)
polymerase and the Rb protein. In addition, we have presented the latest Fas-induced signalling mechanism as a model for receptor-linked
caspase regulation. Finally, the structural and functional interactions of Ced-4 and its partial mam malian homologue, apoptosis
protease activating factor-1 (Apaf-1), are presented in a model which includes other Apafs. This model culminates in a caspase/Apaf
regulatory cascade to activate the executioners of programmed cell death following cytochrome c release from the mitochondria
of mammalian cells. The importance of these pathways in the treatment of disease is highly dependent on further characterization
of genes and other regulatory molecules in mammals.
Received 18 February 1998; accepted February 1998 相似文献
208.
Intermolecular separation determines the extent of orbital overlap and thus the rate of electron transfer between neighbouring molecules in an organic crystal. If such a crystal is compressed, the resistivity decreases owing to a diminishing intermolecular distance. Metal insulator transitions have been observed by applying hydrostatic pressure to, for example, Langmuir films of metal nanoparticles. But previous attempts to observe a clear transition point in organic crystals, such as anthracene and tetracene, were not successful owing to difficulties with electrically insulating the high-pressure cell. Here we report a different approach by using a sample that is photoconductive and forms an organized film. A cylindrical tip (approximately 100 microm in diameter) was used to compress the sample instead of a piston/cylinder structure, entirely eliminating the problem of electrical insulation. Furthermore, by illuminating the sample with a laser, the conductivity of the sample is increased by several orders of magnitude. By monitoring the photocurrent with sensitivity at the 10(-13) A level, changes in resistivity at very low pressure could be monitored. We observe a sharp increase in current that could indicate a transition from hopping to delocalized conduction. 相似文献
209.
210.