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1.
Phospholipid turnover during cell-cycle traverse in synchronous Chinese-hamster ovary cells. Mitogenesis without phosphoinositide breakdown. 总被引:2,自引:0,他引:2
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The turnover of phospholipids was investigated in quiescent serum-starved Chinese-hamster ovary (CHO-K1) cells stimulated to progress through the cell cycle by the addition of dialysed bovine serum. A variety of radiolabelling techniques were employed to study the rapid effects of serum on phospholipids and later events during G1 and S phases of the cell cycle. Pulse-labelling studies using [32P]Pi revealed that there was a stimulation of the synthesis rate of all phospholipids investigated during the initial few hours after serum addition. The greatest stimulation (20-fold) was observed in phosphatidylcholine, and the smallest in the polyphosphoinositides (PPIs). Mock stimulation with serum-free medium caused a similar increase in PPI turnover, but little or no effect on turnover of other phospholipids. This effect could be accounted for by a stimulation of the turnover of cellular ATP pools increasing [32P]ATP specific radioactivity. Late G1 and S phases were associated with a decrease in the rate of synthesis of all phospholipids. Phosphatidic acid was the only phospholipid whose labelling fell below that in mock-stimulated cells during the period of the cell cycle. Stimulation of serum-starved cells that had been prelabelled with myo-[2-3H]inositol caused no change in the amounts of inositol trisphosphate, but both serum-stimulated and mock-stimulated cells exhibited similar small decreases in both inositol bisphosphate and inositol monophosphate, of approx. 30% after 30 s. When cells were serum-stimulated in the presence of 10 mM-Li+, there was no increase in the size of the total inositol phosphate pool. We conclude that mitogenic stimulation and cell-cycle traverse cause profound and complex effects on phospholipid turnover in CHO-K1 cells, but there is no evidence for a role of inositol lipid turnover in the proliferative response to serum in this cell line. 相似文献
2.
We have investigated the effect of bleomycin (BLM) on thymidine phosphorylation in lectin-stimulated normal human lymphocytes. BLM reduces thymidine phosphorylation by decreasing the activity of thymidine kinase (TK). Accordingly, polyacrylamide gel electrophoresis (PAGE) of extracts of cells incubated for 48, 72 and 96 h showed here that this activity dropped 48, 65 and 67% respectively. The electrophoretic profiles of TK activity were similar but different in amplitude. These effects of the BLM were confirmed firstly by direct measurement of TK activity, secondly by amount of 3H-thymidine incorporation in the cultures before cell lysis. Both the measurement of TK activity and 3H-thymidine incorporation were correlated. 相似文献
3.
By preparing a new experimental model for the carpal tunnel syndrome, the authors evaluated the differences of the human and rabbit carpal tunnels using a comparative anatomical study. A nearly identical situation-regarding the osseous and connective tissue formations in the carpal channel--was found. Therefore, the carpal tunnel of the rabbit is recommended for a model of chronic nerve compression, which is now planned by the authors. 相似文献
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6.
Biochemistry of the autolytic processes in Antarctic krill post mortem. Autoproteolysis. 总被引:2,自引:0,他引:2
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1. Autoproteolysis post mortem was examined at 0 degree C by following the changes in the major classes of krill (Euphausia superba and Euphausia crystallorophias) proteins and by liberation of peptides and free amino acids, and was based on experiments conducted on board expedition vessels in the Antarctic. 2. Primarily salt-soluble proteins were broken down during the first week of incubation, whereas water-soluble and insoluble proteins were degraded to a much smaller extent. The enzymes responsible for the hydrolysis presumably originate primarily from the digestive apparatus of the krill. 3. In general, the individual amino acids were released at rates corresponding to their relative occurrence in the bulk protein of the krill. Alanine was liberated in larger amounts than would be expected from the composition of the krill protein, and was evidently formed also by reactions other than proteolysis. Glutamic acid, and certain amino acids which presumably occur with high frequency adjacent to glumatic acid residues in the krill protein, were liberated only to a limited extent, and accumulated in smaller peptides. 4. During proteolysis, arginine seemed to be converted to some degree into ornithine, and on prolonged incubation conversion of arginine and lysine into their corresponding decarboxylation products, agmatine and cadaverine, appeared to take place. 相似文献
7.
The proton ionophore carbonyl cyanide m-chlorophenylhydrazone (CCCP) inhibited antigen-stimulated secretion and calcium influx in rat basophilic leukemia cells. In a glucose-free solution the inhibitory effects of CCCP were due to a decrease in the intracellular ATP concentration; however, when glucose was present there was no decrease in ATP. Instead, we found that in a glucose-containing saline solution, CCCP inhibited antigen-stimulated calcium uptake because it depolarized the plasma membrane, which in rat basophilic leukemia cells inhibits antigen-stimulated calcium uptake. In the presence of glucose, relatively low concentrations of CCCP inhibited calcium uptake while higher concentrations were required to inhibit secretion. In contrast, the initial antigen-stimulated rise in cytoplasmic calcium, measured with the fluorescent calcium indicator quin2, was not inhibited by CCCP. This suggests that the release of calcium from intracellular stores might, in some cases, be sufficient to support antigen-stimulated secretion. In the presence of CCCP the pH gradient becomes important for regulating the membrane potential across the plasma membrane. When cells were depolarized with CCCP and the external pH was increased, the membrane potential returned to resting levels and antigen-stimulated calcium uptake was restored. Inhibition of antigen-stimulated secretion by higher concentrations of CCCP could also be reversed by increasing the external pH. 相似文献
8.
Estimating downwind concentrations of viable airborne microorganisms in dynamic atmospheric conditions. 总被引:3,自引:2,他引:1
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A Gaussian plume model has been modified to include an airborne microbial survival term that is a best-fit function of laboratory experimental data of weather variables. The model has been included in an algorithm using microbial source strength and local hourly mean weather data to drive the model through a summer- and winter-day cycle. For illustrative purposes, a composite airborne "virus" (developed using actual characteristics from two viruses) was used to show how wind speed could have a major modulating effect on near-source viable concentrations. For example, at high wind speeds such as those occurring during the day, or with short travel times, near-source locations experience high viable concentrations because the microorganisms have not had time to become inactivated. As the travel time increases, because of slow wind speed or longer distances, die-off modulation by sunshine, relative humidity, temperature, etc., potentially becomes increasingly predominant. 相似文献
9.
Mohr RD 《Bioethics》1987,1(1):35-50
Mohr argues that coercive government policies in response to the AIDS crisis are unjustified and pose a serious threat to the rights of homosexuals. AIDS presently can be transmitted only to those whose actions place them at risk. Paternalistic state coercion is warranted only when a person has diminished capacity or when necessary to prevent someone from ceasing to be an independent agent. Furthermore, an individual may regard sex as a central value. Finally, using public health as a rationale for closing bathhouses or otherwise regulating sexual behavior is a step toward totalitarianism, because coercion is unwarranted when protection from a disease can be achieved by individual action and because the public good served by reducing the size of the pool of AIDS-exposed people is outweighed by the unjust discrimination involved in using coercive measures that affect only certain individuals. 相似文献
10.
The two new potent anthracycline antitumor antibiotics, morpholinodaunomycin and cyanomorpholinoadriamycin, are nonmutagenic or weakly mutagenic in Salmonella typhimurium or V79 Chinese hamster cells, but highly active inducing DNA repair in in cultured rat hepatocytes. Both agents were found to induce malignant transformation in vitro of C3H M2 mouse fibroblasts and mammary tumors in female Sprague-Dawley rats. The data indicate a) that these new anthracyclines, too, are highly oncogenic and b) in conjunction with previously published results, that the predictive value of in vitro short-term tests for in vivo carcinogenicity is dependent on the employment of a battery of such tests.Abbreviations ADM
adriamycin
- CNMoADM
cyanomorpholinoadriamycin
- DNM
daunomycin
- MNNG
N-methyl-N-nitro-N-nitrosoguanidine
Dedicated to Dr. J.H. Weisburger on his 65th birthday 相似文献