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181.
The objective of this study was to examine the use of lysostaphin as an ATP-extracting agent for the estimation of Staphylococcus aureus cell number by a rapid bioluminescent ATP method. The results of the study showed that lysostaphin (22 U/ml) was able to lyse most of the S. aureus cells (greater than 99.9%) at room temperature in 1 min; ATP of S. aureus cells extracted by the lysostaphin lysis procedure was stable for 24 h in the presence of EDTA; there was a linear relationship between the ATP content and the number of S. aureus cells (ranging from 10(4) to 10(6) CFU/ml); and the lysis of S. aureus cells by lysostaphin allowed estimation of the number of S. aureus cells in mixed cultures and in meat samples. 相似文献
182.
Summary The reductive cleavage of the aclacinomycins A (I), Y (II), and B (III) by intact mycelia or subcellular fractions of the producer strain S. spec. AM 33352/F43 is suppressed in the presence of uncouplers, complex-forming agents, detergents, and some metal anions such as chromate. Increased concentration of the latter in complete cultures caused rearrangement of I to III. 相似文献
183.
Summary A mutant ofS.
chrysomallus with a D-glucose isomerase inducible by D-glucose or its catabolites was characterized. In contrast to the wild-type strain it showed a decreased catabolite repression by D-glucose of D-xylose consumption and a constitutive pentose phosphate pathway as well. A hypothesis concerning altered induction pattern of its D-glucose isomerase is discussed. 相似文献
184.
Affinity constant (Km) of D-glucose, L-alanine, L-aspartate, L-lysine, L-proline and nutrients coupled Na+ were determined in renal brush border membrane vesicles prepared from control and pyelonephritic rats. The Km of D-glucose, amino acids and nutrients coupled Na+ was noted to be significantly increased (p less than 0.001) in experimental animals. The Vmax of D-glucose and amino acids was determined at different concentrations of nutrients keeping extravesicular Na+ constant or at different concentrations of extravesicular Na+ keeping nutrient concentration constant. In the experimental rats the Vmax decreased significantly (p less than 0.01) when compared to control. The increased Km and decreased Vmax may be one of the underlying mechanism leading to decrease in the uptake of D-glucose and amino acids. 相似文献
185.
Petrobia harti (Ewing) developed more rapidly, deposited more eggs and lived longer onOxalis corniculata than onO. articulata. No development took place on several other recorded host plants. In the field this mite was most abundant during early summer. Males made up less than 10% of the population, and no diapause eggs were seen in the field.Petrobia tunisiae Manson developed on various winter Gramineae, produced about 17 non-diapause eggs during its first generation and mostly diapause eggs in the second. A few diapause eggs kept in the laboratory and dipped in chloroform hatched even after 3 years. A summer diapause is postulated for this species. 相似文献
186.
The protein synthesis-stimulating activity of the cytosolic fraction from regenerating rat liver was tested in a cell-free system using washed polysomes from normal rat liver. This activity undergoes significant changes during liver regeneration after partial hepatectomy (p.h.). An initial decrease until 16 h after p.h. is followed by a significant increase until 24 h after p.h. Beyond 32 h after p.h. the activity begins to decline again. Evidence is presented that these changes of the cytosolic activity may not be due to alterations in the distribution of protein synthesis-stimulating factors between the microsomal and the cytosolic fraction. The Met-tRNAf-binding activity of the cytosolic fraction changes during liver regeneration analogously to the protein synthesis-stimulating activity measured in the polysomal assay. This indicates that initiation factor eIF-2 is involved in the observed changes of the cytosolic activity. This conclusion could be confirmed by addition of purified eIF-2 to the polysomal assay system. Addition of eIF-2 to cytosolic fractions of low endogenous protein synthesis-stimulating activity (16 h after p.h.) enhances amino-acid incorporation to a significantly higher extent than addition to highly active cytosolic fractions (24 h and 32 h after p.h.). From these results it is concluded that changes in eIF-2 plays an essential role in the described alterations of the cytosolic activities during liver regeneration. 相似文献
187.
To find out minimal sizes of the proteinase inhibitor proteins hirudin and eglin necessary for their biological activity the inhibitors were incubated with exopeptidases. From the incubation mixtures shortened derivatives were isolated and characterized. Eglin c can be N-terminally shortened by up to 6 amino-acid residues without any loss of affinity towards chymotrypsin. The complex of thrombin with hirudin lacking 3 C-terminal amino-acid residues showed a 15-20-fold increased Ki value as found previously for desulfato-hirudin and desulfato-hirudin shortened by 2 amino-acid residues. Obviously, the C-terminal part of the hirudin molecule has a positive influence on its affinity to thrombin. 相似文献
188.
One antigen, one gold? A quantitative analysis of immunogold labeling of plasma membrane 5'-nucleotidase in frozen thin sections 总被引:3,自引:0,他引:3
K E Howell U Reuter-Carlson E Devaney J P Luzio S D Fuller 《European journal of cell biology》1987,44(2):318-327
We present an evaluation of the efficiency of immunogold labeling for a low abundance plasma membrane protein. Several independent methods were used to determine the density of 5'-nucleotidase on the plasma membrane of the Fao cell. These methods include morphometry in combination with either enzymology or cell surface radiometric assay. Immunocytochemistry of frozen thin sections with either single or double layers of antibody and visualized with protein A complexed with 5 nm colloidal gold was used to estimate the same density. The application of a balance sheet to immunogold labeling demonstrates that the labeling is never quantitative. For example, labeling of the cell surface is always greater than labeling on the section. We show that departures from the "one antigen, one gold" ideal are systematic, so that an efficiency can be calculated and quantitative results can be obtained. The ability to obtain reliable quantitative results from immunogold labeling extends the utility of this already powerful technique. 相似文献
189.
We estimate the active part of cytochrome P-450, which is involved in a special substrate transformation, by measuring the initial change of the production rate as a function of the relaxation transitions between two different steady states of the reaction cycle of cytochrome P-450 using the light-reversibility of the carbon monoxide inhibition. The kinetic data of such relaxations are interpreted within a model cycle, which reduces the reaction cycle to three steps. The estimation of the rate constant of the first reduction step, derived from model simulation of the production rate, is confirmed by independent experimental study of the reduction kinetics.An application of our model to the O-deethylation of 7-ethoxycoumarin reveals that — in a time average — 10%–15% of the spectroscopically detectable cytochrome P-450 is involved in that transformation.Abbreviations Cyt. P-450
microsomal cytochrome P-450
- 7-EC
7-ethoxycoumarin 相似文献
190.
Plasmodium berghei ookinetes were cultured from hamster blood as described previously (Kurtti and Munderloh, 1986). An average of 7.3 X 10(6) ookinetes was harvested from each ml of blood. Ookinetes were purified by centrifugation on first a 40% and then a 36% Percoll gradient. The final preparation comprised 32.8% of the ookinetes initially obtained, and contained 3.3 other parasite stages or blood cells per ookinete. Unpurified and purified ookinetes were resuspended in hamster blood and fed to Anopheles stephensi. There was a strong linear correlation between the concentration of purified or unpurified ookinetes and the number of oocysts formed. With unpurified ookinetes, a maximum was reached when preparations containing 1 X 10(7) ookinetes/ml were fed, and feeding preparations containing a higher concentration did not produce more oocysts. Sporozoites were found in the salivary glands of mosquitoes fed ookinetes by days 14 (unpurified) or 15 (purified) PI. Approximately 5 times as many purified as unpurified ookinetes were required to produce each oocyst. 相似文献