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61.
62.
On 15 November 2017 the mouth of the West Kleinemonde Estuary breached following heavy catchment rains and increased river flow. The water level in the estuary following mouth opening decreased by 1.65 m within 24 h, resulting in an almost complete draining of the littoral zone where large beds of the aquatic macrophyte Ruppia cirrhosa and mats of the associated filamentous algae were present. As the water depth within the plant beds decreased, the macrophytes, together with the algal filaments, created an increasingly dense mat, trapping fish that were resident, foraging or passing through the littoral zone. By 16 November 2017 large numbers of fishes belonging to at least 20 species were trapped in pools and depressions within the littoral, as well as within the R. cirrhosa beds and filamentous algal mats in the lower reaches of this system. Other affected taxa included crustaceans, especially isopods, and large numbers of small bivalves attached to macrophyte vegetation. Beneficiaries of the fish kill, in terms of unexpected food availability, included a variety of piscivorous bird species and the Cape clawless otter Aonyx capensis. This is the first documented account of a diverse species fish kill associated with estuary mouth breaching. 相似文献
63.
Chan KY Gumbart J McGreevy R Watermeyer JM Sewell BT Schulten K 《Structure (London, England : 1993)》2011,19(9):1211-1218
Many large biological macromolecules have inherent structural symmetry, being composed of a few distinct subunits, repeated in a symmetric array. These complexes are often not amenable to traditional high-resolution structural determination methods, but can be imaged in functionally relevant states using cryo-electron microscopy (cryo-EM). A number of methods for fitting atomic-scale structures into cryo-EM maps have been developed, including the molecular dynamics flexible fitting (MDFF) method. However, quality and resolution of the cryo-EM map are the major determinants of a method's success. In order to incorporate knowledge of structural symmetry into the fitting procedure, we developed the symmetry-restrained MDFF method. The new method adds to the cryo-EM map-derived potential further restraints on the allowed conformations of a complex during fitting, thereby improving the quality of the resultant structure. The benefit of using symmetry-based restraints during fitting, particularly for medium to low-resolution data, is demonstrated for three different systems. 相似文献
64.
Norian-Rhaetian reefs in Argolis Peninsula,Greece 总被引:2,自引:0,他引:2
PD Dr. Baba Senowbari-Daryan Dr. Dionissios Matarangas Dr. Myrsini Vartis-Matarangas 《Facies》1996,34(1):77-82
Summary Upper Triassic to Lower Jurassic shallow-water carbonate sequences of the ‘Pantokrator limestones’ are widely distributed
in the Argolis Peninsula, southern Greece. Within this sequence are some reef or reefal structures. In the Mavrovouni Mountains,
near Sarmeika, 6 km SE of the ancient theatre of Epidavros (Argolis Peninsula), a Norian-Rhaetian reef complex has been identified.
This is the first well-documented Norian-Rhaetian reef in Greece. The main reef builders are coralline sponges (‘sphinctozoans,’
‘inozoans’, and sclerosponges), followed by dendroid, cerioid, and solitary corals, and algae. The reef type corresponds to
a ‘sponge-coral reef’. 相似文献
65.
Molecular clocks are routinely tested for linearity using a relative rate
test and routinely calibrated against the geological time scale using a
single or average paleontologically determined time of divergence between
living taxa. The relative rate test is a test of parallel rate equality,
not a test of rate constancy. Temporal scaling provides a test of rates,
where scaling coefficients of 1.0 (isochrony) represent stochastic rate
constancy. The fossil record of primates and other mammals is now known in
sufficient detail to provide several independent divergence times for major
taxonomic groups. Molecular difference should scale negatively or
isochronically (scaling coefficients less than 1.0) with divergence time:
where two or more divergence times are available, molecular difference
appears to scale positively (scaling coefficient greater than 1.0). A
minimum of four divergence times are required for adequate statistical
power in testing the linear model: scaling is significantly nonlinear and
positive in six of 11 published investigations meeting this criterion. All
groups studied show some slowdown in rates of molecular change over
Cenozoic time. The break from constant or increasing rates during the
Mesozoic to decreasing rates during the Cenozoic appears to coincide with
extraordinary diversification of placental mammals at the beginning of this
era. High rates of selectively neutral molecular change may be concentrated
in such discrete events of evolutionary diversification.
相似文献
66.
PD Dr. M.J. Koch 《Medizinische Genetik》2007,19(4):392-398
Dental development takes place in stages over a long period of time. From the 6ths embryonal week, when the dental lamina develops, tooth number and shape are formed, followed by the production of dental hard tissues. Genetic dental developmental defects are not rare. Mostly these defects affect the tooth number, predominantly resulting in a decrease tooth number (hypodontia) which can occur isolated or as a finding in genetic syndromes such as Rieger syndrome, Witkop syndrome or several ectodermal dysplasias. Genetic defects of dental hard tissues are less frequent, different types of isolated enamel defects (amelogenesis imperfecta) are known. Dentinogenesis imperfecta or other dentinal defects are either caused by different mutations of the DSPP gene or a part of osteogenesis imperfecta. 相似文献
67.
Familial clustering of colorectal cancer (CRC) and early disease onset are indicators of an inherited tumour syndrome. Monogenic dispositions account for 3–5% of all CRC cases and are subdivided into hereditary non-polyposis colorectal cancer (HNPCC/Lynch syndrome) and various gastrointestinal polyposis syndromes. Many of these syndromes are characterised by a broad spectrum of extracolonic tumours. Early detection and accurate classification are essential in providing effective surveillance and treatment. Initial diagnosis is based on endoscopic and histological findings as well as on the presence of extracolonic manifestations and family history. Molecular genetic examination is important for the differential diagnosis, evaluation of recurrence risk, and predictive testing of asymptomatic at risk individuals; it is performed according to largely standardised algorithms. Diagnostic difficulties are common among the hamartomatous polyposes due to their broad phenotypic overlap and frequent uncertainties in histological evaluation, as well as among patients with few adenomas. Risk-adapted surveillance guidelines have been established for HNPCC and for the more frequently observed polyposis syndromes. Beyond established tumour syndromes, familial clustering of CRC (which is often of late onset) or the occurrence of few adenomas is likely to be based upon a multifactorial (complex) etiology. Although identification of the underlying genetic risk factors and biological pathways is still in the early stages, rapid progress is being made due to methodical developments such as genome-wide association studies and CNV analysis. 相似文献
68.
PD Dr. P.N. Robinson M. Arslan-Kirchner P. Gehle J. Schmidtke Prof. Dr. Y. von Kodolitsch 《Medizinische Genetik》2011,23(3):407-420
Marfan syndrome (MFS) is an autosomal dominant, pleiotropic disease of the connective tissue with a prevalence of about 1 in 5000 persons. MFS is characterized by manifestations in the cardiovascular system, eye, skeleton, lung, skin, and dura mater that show a high degree of intra- and interfamilial variability. Many manifestations develop during or shortly before puberty; severe complications rarely occur before adulthood. Many patients with MFS display a so-called marfanoid habitus with tall stature, dolichostenomelia (long, narrow extremities), dolichocephaly (disproportionately long and narrow head), as well as other skeletal abnormalities such as scoliosis and pes planus. Scoliosis occurs in approximately 60% of those affected, pectus deformities in up to two thirds. Ectopia lentis is seen in many patients with MFS and is almost always bilateral. MFS is characterized by a high risk for complications such as severe scoliosis or pectus deformities, spontaneous pneumothorax, retinal detachment, or glaucoma secondary to lens luxation. The most severe complications occur in the cardiovascular system, including in particular acute dissection of the ascending aorta, which generally follows a long period of progressive aortic dilatation. Before the introduction of modern treatment modalities, the average life expectancy of persons with MFS was estimated to be 32 years. Today, with medical care in multidisciplinary centers, an average life expectancy of over 60 years can be achieved. This article offers a review of established and novel concepts for the diagnosis and treatment of MFS and other hereditary diseases of the aorta. 相似文献
69.
The domestic dog shows a wide range of morphologies, that humans have selected for in the process of creating unique breeds. Recent studies have revealed correlations between changes in morphology and behaviour as reported by owners. For example, as height and weight decrease, many undesirable behaviours (non-social fear, hyperactivity and attention seeking) become more apparent. The current study aimed to explore more of these correlations, but this time used reports from trained observers. Phenotypic measurements were recorded from a range of common dog breeds (n = 45) and included cephalic index (CI: the ratio of skull width to skull length), bodyweight, height and sex. These data were then correlated with results from the Dog Mentality Assessment (DMA), which involves trained observers scoring a dog’s reaction to stimuli presented over 10 standardised subtests. Each subtest is designed to evoke a behavioural response. Backward elimination and weighted step-wise regression revealed that shorter dogs demonstrated more aggressive tendencies, reacting defensively toward both assistants dressed as ghosts (p = 0.045), and to a dummy (p = 0.008). Taller dogs were more affectionate when greeting and being handled by humans (p = 0.007, p = <0.001, respectively). Taller dogs were also more cooperative (p = <0.001), and playful (p = 0.001) with humans than shorter dogs. Heavier dogs were more inquisitive toward a dummy (p = 0.011), to the source of a metallic noise (p = 0.010) and to an assistant (p = 0.003). Heavier dogs were also more attentive to the ghosts (p = 0.013). In comparison, lighter dogs were cautious of a dummy (p = <0.001) and fearful of the sound of a gunshot (p = <0.001). Lighter dogs were also cautious of, and demonstrated prolonged fearfulness toward, the source of metallic noise (p = <0.001, p = <0.034, respectively). With a far larger sample and the advantage of third-party reporting (which overcomes potential owner bias), the current findings build on previous studies in this field, further supporting covariance between morphology and behaviour. 相似文献
70.