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971.
Summary The effect of vehicle perturbation on sulphatase enzyme activity in arctic tundra soils was examined. Sulphatase activity
was significantly less in disturbed (vehicle track) than that adjacent undisturbed tundra soils. Soil moisture and water movement
appeared to be major controlling factors. The results of the study suggest that biochemical mineralization of organic sulphur
in disturbed tundra soils is controlled by nutrient influx associated with water movement, altering sulphatase activity to
a level consistent with the need for, as well as the supply of, the mineralized element. 相似文献
972.
Vascular knee allograft transplantation in a rabbit model 总被引:1,自引:0,他引:1
Using a rabbit model in which vascularized knee autograft transplantation was successful, vascularized knee allograft transplants survived an average of 9 days, as determined by serial bone scan. The longest surviving allograft was one of 3 months. Immunosuppression and irradiation did not significantly increase survival. Both vascularized and nonvascularized allografts elicited a second-set skin graft response but no histologic evidence of rejection. This suggests that joint allografts are clearly immunogenic but do not undergo the same destructive rejection process with a clear end point seen with soft-tissue grafts. Donor vessels did show a classic rejection picture with severe intimal damage presumably predisposing to vessel thrombosis and graft loss. Vascular rejection, therefore, limited joint allograft survival. Immediate vascularization of the allograft with subsequent limited survival does not enhance host revascularization and creeping substitution at 1, 3, or 6 months. These findings do not suggest clinical applicability for vascularized joint allograft transplantation at this time. Future experimental studies should employ genetically defined models. 相似文献
973.
K O'Brien E Moss D Judah G Neal 《Biochemical and biophysical research communications》1983,114(2):813-821
Primary metabolism of aflatoxin B1 by the liver microsomal enzymes from a range of animal species showed both quantitative and qualitative differences. Quail was shown to have the most rapid metabolism of aflatoxin B1. The major product of metabolism in this case was found to be aflatoxin B1-8,9-dihydrodiol suggesting that the quail microsomes produced high levels of the proposed reactive intermediate aflatoxin B1-8,9-epoxide. Using this system to generate the epoxide, the ability of the cytosol prepared from each species to conjugate epoxide with reduced glutathione was investigated. Large differences in ability to conjugate were observed ranging from 0 to 72% for quail and mouse respectively. Differences in both primary and secondary metabolism of AFB1 were noted between male and female Fischer 344 rats. 相似文献
974.
Erika Schmid Werner W. Franke Christine Grund Dorothea L. Schiller Heiderose Kolb Neidhard Paweletz 《Experimental cell research》1983,146(2):309-328
Cells of a clonal line (BMGE + HM) selected from bovine mammary gland epithelial cell cultures are described which, after reaching confluence, do not assume typical epithelioid morphology, but form elongated cells with long slender processes extending over the surfaces of other cells. However, cells of this line which display non-epithelioid morphology and are exceptionally rich in actin microfilaments are identified as epithelial cells by their synthesis of cytokeratins and desmosomal plaque proteins, as demonstrated by immunofluorescence and immunoelectron microscopy and by gel electrophoresis of cytoskeletal proteins. The cells do not produce vimentin and desmin filaments. The specific cytokeratin polypeptides of these myoid cells are identical to those present in normal epithelioid BMGE + H cells but are arranged in unusual arrays of meshworks of finely dispersed, non-fasciated filaments and granular structures. Desmosomal plaque proteins, notably desmoplakins, are abundant, but the electron microscopic appearance of the desmosomes is abnormal in that most of them are associated with a second accessory plaque formed at a distance of 0.1-0.15 micron from the normal desmosomal plaque. Both cytokeratin filaments and desmosomal structures are found throughout the whole cytoplasm, including the extended cell processes. The existence of an epithelial cell line with such an unusual morphology demonstrates the importance of non-morphological criteria in identifying epithelium-derived cells. Our findings also indicate that dramatic differences of cell shape and organization of epithelial cells need not necessarily be associated with changes in the expression of specific cytoskeletal proteins. The possible origin of this cell line from myoepithelial cells is discussed. 相似文献
975.
An enzymatic method for the measurement of ethanol has been developed to permit analyses with unneutralized acid extracts of blood, liver, cell suspensions, or other biological materials. Components of the assay mixture include NAD, yeast alcohol dehydrogenase, tris(hydroxymethyl)aminomethane (Tris), and lysine. Tris is a trapping agent for the reaction product, acetaldehyde. Lysine is used to maintain the pH at 9.7 where oxidation of ethanol is quantitative and most rapid, even when as much as 0.2 ml of 0.5 n HClO4 is added. Lysine also causes the reaction to be 2 to 4 times faster than it is when either glycine or 2-amino-2-methyl-1-propanol is used as the buffer. The assay is linear up to an ethanol concentration of 0.125 mm in the reaction mixture and is complete by 4 min. By substituting ethanol for NAD in the reagents, the assay performs equally well in measuring NAD. 相似文献
976.
Summary The interendothelial junctions of all segments of the renal vasculature have been studied in eight species using the freeze-fracture technique. Three types of junctions have been found. Combinations of tight and gap junction elements are characteristic for interlobular arteries and proximal afferent arterioles. Continuous tight junction strands not subdivided into individual particles are typical for the glomerular arterioles close to the glomerulus and the vasa recta. The interendothelial junctions of glomerular and peritubular capillaries and cortical veins are characterized by slight elevations decorated with sparse arrays of particles on the P-face of the endothelial cell plasma membrane.These studies were supported by the German Research Foundation within the SFB 90 Cardiovascular System. 相似文献
977.
978.
The feeds of 14 very low birthweight infants (birth weight less than 1500 g) were supplemented with a glucose polymer (Caloreen) at the rate of 6 g/kg body weight daily. Seven day periods of supplementation were alternated with seven day periods of normal feeding. Adding the glucose polymer significantly increased the rate of weight gain in these infants from 105 g/week to 140 g/week; growth rates in terms of length and head circumference were not affected. No adverse effects were noted. Glucose polymer is a useful energy supplement for very low birthweight infants. 相似文献
979.
Association between burst-pulse sounds and aggressive behavior in captive Atlantic bottlenosed dolphins (Tursiops truncatus) 总被引:1,自引:0,他引:1
Neal A. Overstrom 《Zoo biology》1983,2(2):93-103
A specific display observed during agonistic behavior among captive Atlantic bottlenosed dolphins (Tursiops truncatus) was examined. The primary component of the display was an open-mouthed posture accompanied by violent vertical head motions and the emission of pulse-type vocalizations. Jaw-clap behavior produced during the display was quantified for use as an index of aggressive motivation. By aurally monitoring the animals' vocalizations it was found that the level of aggressive response between the participants of the interactions increased with the production and subsequent duration of burst-pulse sounds. The possibility of burstpulse sounds resulting in auditory or tactile discomfort when directed toward conspecifics is discussed. 相似文献
980.
Takao Machi Neal F. Kassell W. Michael Scheld 《In vitro cellular & developmental biology. Plant》1990,26(3):291-300
Summary For our laboratory's investigation into the role of the endothelial cells in vasospasm following subarachnoid hemorrage and
in inflammatory diseases, we found it necessary to dvise a modified method of cell culture, which would be appropriate for
studying human endothelial cells from lobectomized brain. We report our techniques to increase cell harvest and ensure reproducibility,
our method of culturing endothelial cells from bovine major cerebral arteries, and our morphologic and immunocytochemical
charcterization of thee cells. To increase the harvest of endothelial cells, the blood cells were washed from the lumen of
the major cerebral arteries at the slaughterhouse and a modified reversed vessel technique was employed. The monolayer of
cultured endothelial cells displayed a cobblestone appearance when it reached confluency and transmission electron microscopy
revealed junctional complexes and interdigitation of cytoplasm at Passages 10 and 17. The cells stained positively for Factor
VIII-related antigen at Passages 3, 5, 7, 10, and 15. Also the cells metabolized acetylated low-density lipoprotein at Passage
3. To determine th purity of the cultured endothelial cells, an immunocytochemical study of the cytoskeleton was performed
on Passage 5 cells using either rhodamine-phalloidin or antibodies against smooth muscle myosin, desmin, and vimentin. 相似文献