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571.
Maturing females of the octopod Japetella diaphana (Hoyle) develop a luminous oral ring. Studies of specimens of different size show that this structure develops from a muscular ring which undergoes great cellular proliferation, associated with gradual degeneration of the original muscle. The light-producing cells (photocytes) have a relatively uniform cytoplasm whose most characteristic components are small mitochondria, granular aggregates and microtubular or microfibrillar bundles. It is concluded that the original muscle tissue is not transformed directly into luminous tissue.
Possible uses of the luminescence are discussed, based on the postures adopted by live specimens in shipboard aquaria. 相似文献
Possible uses of the luminescence are discussed, based on the postures adopted by live specimens in shipboard aquaria. 相似文献
572.
Freeman W. Cope 《Bulletin of mathematical biology》1961,23(4):337-353
Detailed equations are given for the computation of aortic distensibility in the intact living human patient from measurements
of systolic and diastolic arterial pressures, heart rate and cardiac output. From these equations, the aortic characteristics
of a large series of normal men of different ages were computed. Comparing these results with measurements on excised aortas,
a more pronounced trend toward increasing aortic stiffness with increasing age is evident in living than in dead aortas. Nor-epinephrine
and exercise apparently cause the living aortas to constrict but to become more distensible. The same change occurs after
30 minutes of high spinal anesthesia. The ganglionic blocking agents hexamethonium, pentamethonium, and tetraethylammonium
usually cause the living aorta to become stiffer, presumably due to dilatation. The aortas of patients with pulmonary disease
usually react in different fashion to exercise or tetraethylammonium. The increased aortic distensibility that occurs with
the hypertension induced by nor-epinephrine or exercise acts as a compensatory mechanism by decreasing systolic pressure.
Opinions and conclusions contained in this report are those of the author. They are not to be construed as necessarily reflecting
the views or the endorsement of the Navy Department. 相似文献
573.
574.
Measures of cardiac function in Theraphosidae spiders using in vivo magnetic resonance imaging
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Gavin D. Merrifield Nichola M. Brydges Lynsey Hall James Mullin Lindsay Gallagher Romain Pizzi William M. Holmes 《Physiological Entomology》2018,43(3):207-213
We report the first in vivo cardiac magnetic resonance imaging (MRI) measurements of Theraphosidae spiders. MRI scanning is performed on six spiders under isoflurane‐induced anaesthesia. Retrospective self‐gating cine‐cardiac MRI (RG‐CINE‐MRI) is used to overcome the difficulties of prospective cardiac gating in this species. The resulting RG‐CINE‐MRI images are successfully analyzed to obtain functional cardiac parameters from live spiders at rest. Cardiac ejection fraction is found to increase with animal mass (Pearson correlation 0.849, P = 0.03) at a faster rate than myocardial tissue volume, whereas heart rate remains constant across animals. This suggests the spider heart undergoes additional biomechanical loading with age. The results of the present study demonstrate the potential for retrospective gating with respect to evaluating aspects of cardiac function in a wide range of previously inaccessible species. 相似文献
575.
576.
F W Cope 《Physiological chemistry and physics》1979,11(3):261-262
Cytochrome oxidase protein has a measured activation energy of semiconduction much smaller than that of other proteins, falling within the range of the activation energy of the cytochrome oxidase reaction in solution. Many kinetic peculiarities of the cytochrome oxidase reaction difficult to explain by mass-action theories are easily accounted for if semiconduction is assumed to be the controlling mechanism. 相似文献
577.
George Ashdown Elvis Pand?i? Andrew Cope Paul Wiseman Dylan Owen 《Journal of visualized experiments : JoVE》2015,(106)
Filamentous-actin plays a crucial role in a majority of cell processes including motility and, in immune cells, the formation of a key cell-cell interaction known as the immunological synapse. F-actin is also speculated to play a role in regulating molecular distributions at the membrane of cells including sub-membranous vesicle dynamics and protein clustering. While standard light microscope techniques allow generalized and diffraction-limited observations to be made, many cellular and molecular events including clustering and molecular flow occur in populations at length-scales far below the resolving power of standard light microscopy. By combining total internal reflection fluorescence with the super resolution imaging method structured illumination microscopy, the two-dimensional molecular flow of F-actin at the immune synapse of T cells was recorded. Spatio-temporal image correlation spectroscopy (STICS) was then applied, which generates quantifiable results in the form of velocity histograms and vector maps representing flow directionality and magnitude. This protocol describes the combination of super-resolution imaging and STICS techniques to generate flow vectors at sub-diffraction levels of detail. This technique was used to confirm an actin flow that is symmetrically retrograde and centripetal throughout the periphery of T cells upon synapse formation. 相似文献
578.
579.
Differences in degree of defoliation in CO-air mixtures were shown by geographic variants in Acacia farnesiana (L.) Willd., a widespread, weedy, pantropic, leguminous tree. Laboratory-germinated seedlings from Mazatlán (MAME-1), Sinaloa, Mexico, showed greater sensitivity to a CO gradient than plants from Point Tuna (PORO), Puerto Rico. Seedlings of both strains grown under a light intensity of 200 ft-c showed greater sensitivity to CO than those grown under 1,800 ft-c. When intact plants of 17 geographic variants grown at low-light intensities were exposed to 2% CO in air, 11 strains (Mexico, 8; Texas, 1; California, 1; Guatemala, 1) showed almost complete defoliation. The other six strains—from Brazil, Hawaii, Puerto Rico, Italy, Algeria, and Micho-acán, Mexico—showed defoliation averaging from 23 to 70%. The significance of the CO-de-foliation response is difficult to explain in terms of the natural distribution of A. farnesiana. It is suggested that this response may be correlated with some biochemical process of adaptive significance. 相似文献
580.