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991.
An intrapleural implantation procedure by thoracotomy was developed for application in mice. Animal survival was found to depend on the following: (A) slow induction and quick reversal of a pneumothorax by controlled pleural air injection and withdrawal, (B) keeping the pleura open for the shortest possible time by quick insertion of the implant and immediate tight closure with prepositioned sutures, and (C) use of the right, not the left, pleural cavity especially for maximum size implants which for a 30-gram mouse was 12 X 5 X 4 mm. Surgical and postsurgical mortality was below 5% (n = over 300). 相似文献
992.
993.
H+/O stoichiometries of 0, 2 and 4 have been proposed for cytochrome oxidase. Here we show that a stoichiometry of 4 is thermodynamically impossible for rat liver cytochrome oxidase under normal conditions. 相似文献
994.
995.
We report the results of a M?ssbauer study of the low-potential iron-sulfur cluster FX in the Photosystem I core protein of Synechococcus 6301. The M?ssbauer spectrum of FX in the oxidized state shows an isomer shift of 0.42 mm/s, which is in good agreement with the 0.43 mm/s isomer shift found in [4Fe-4S] proteins but not with the isomer shift of 0.26 mm/s found in [2Fe-2S] proteins. In the reduced state the spectrum is asymmetrically broadened at 80 K, indicating the presence of two very closely spaced doublets with an average isomer shift of 0.55 mm/s, which is also in agreement with [4Fe-4S] proteins. At 4.2 K, the spectrum exhibits broadening and magnetic splitting similar to what is observed for [4Fe-4S] proteins and quite unlike [2Fe-2S] proteins. Given the assumption that the iron atoms of FX are tetrahedrally coordinated with sulfur ligands, the data strongly support the assignment of FX as a [4Fe-4S] cluster. 相似文献
996.
Photosystem I inhibition by polycations 总被引:2,自引:0,他引:2
997.
William L. Nyhan Toshiyuki Ando Karsten Rasmussen William Wadlington Anthony W. Kilroy Dennis Cottom David Hull 《The Biochemical journal》1972,126(4):1035-1037
Tiglic acid, which has not previously been found in human body fluids, was recently detected in the urine of two patients with propionicacidaemia. These patients had a documented defect in the oxidation of propionate. A competition between acrylyl-CoA and tiglyl-CoA for crotonase could explain the accumulation of tiglic acid. 相似文献
998.
M D Brand 《The Biochemical journal》1985,225(2):413-419
Respiring liver mitochondria were allowed to export Ca2+ on the endogenous Ca2+/nH+ antiporter in the presence of Ruthenium Red (to inhibit uptake on the Ca2+ uniporter) until a steady state was reached. Addition of sufficient of the ionophore A23187 (which catalyses Ca2+/2H+ exchange) to bring the Ca2+ and H+ gradients into equilibrium did not alter the steady state. Thermodynamic analysis showed that if a Ca2+/nH+ exchange with any value of n other than 2 was at equilibrium, addition of A23187 would have caused an easily measurable change in extramitochondrial free [Ca2+]. Therefore, the endogenous carrier of liver mitochondria catalyses electroneutral Ca2+/2H+ antiport. 相似文献
999.
Biogeochemistry of Late Paleozoic North American brachiopods and secular variation of seawater composition 总被引:3,自引:0,他引:3
Uwe Brand 《Biodegradation》1989,7(3):159-193
Sr/Ca ratios in modern brachiopod shells reflect variations in ambient seawater, whereas their Na contents show no relationship
with water depth or habitat. Their Mn and Fe contents are controlled, in part, by leaching of these elements from oxide coatings
or the low input/sedimentation rate of detrital material into depositional areas such as Quatsino Sound.
For most Carboniferous brachiopods from North America, the Mn and Fe contents are similar to those recorded by their Recent
counterparts. The high Mn and Fe contents in the brachiopods from shales suggest several possibilities for these levels. One
possibility is the leaching of Mn and Fe from oxide coatings/matrix which was not completely removed in the cleaning process,
or the high levels in part reflect unusual depositional conditions (some degree of anoxia) for the local shaly environments.
The Sr/Ca ratio of brachiopods and, by inference, complementary seawater, did not vary significantly during the Carboniferous.
The Sr/Ca minimum observed in brachiopods of Mississippian age coincides with a dip in the 87Sr/86Sr curve and correlates with the Hercynian orogeny. This is attributed to the cycling of seawater through mid-ocean ridge
basalts, and postulated exchange reactions account for variation in the composition of seawater-Ca. The unidirectional trend
of heavier δ13C values from the Devonian to the Permian is intricately coupled with the evolution of the terrestrial biomass. In addition
to expansion of terrestrial plants, burial of reduced carbon in the form of coal (organic matter) contributed to the observed
shift. The start of the Permo-Pennsylvanian glaciation is marked by a negative excursion of the secular carbon trend, which
is linked to weathering of reduced carbon and its return to the oceanic reservoir with its oxidized carbon. The oxygen isotope
values reflect the unidirectional trend towards higher values of the carbon data with decreasing geologic age. Negative excursions
of the trend may be related to extensive weathering of terrestrial and submarine rocks, whereas positive excursions may be
related to hydrothermal alteration of submarine rocks and dehydration of oceanic crust during times of active sea-floor spreading.
Oxygen-calculated water temperatures of unaltered brachiopod material are unrealistically high for all of the Devonian, and
the Chesterian-Meramecian, Desmoinesian-Missourian, and Artinskian Epochs. During these times maximum water temperatures of
42° to 56°C are well above the thermal threshold of protein denaturation. This process, which is lethal to most higher organisms,
demands an adjustment in oxygen of -2.5%. for samples older than Missourian, and of -1.250%. for samples spanning the Missourian-Artinskian
interval. With these adjustments and salinity considerations made prior to calculations, water temperatures become reasonable
for the Late Paleozoic epeiric, tropical seas of North America. 相似文献
1000.
Th. v. Brand W. Weise 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1932,18(2):339-346
Zusammenfassung Auf Grund der Untersuchung des Sauerstoffgehaltes der Galle, des Dünndarminhaltes und der Dünndarmgase einiger Tiere wird gefolgert, daß die in diesen Organsystemen lebenden Parasiten ganz vorwiegend auf einen anoxybiotischen Stoffwechsel angewiesen sind. 相似文献