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41.
Sensitivity of CaMg ATPase from axonic plasma membrane (APM) and sarcoplasmic reticulum (SR) of lobster, , to DDT was studied. The CaMg ATPase found in SR with the high Ca2+ affinity is sensitive to DDT while the portion of ATPase related to the low Ca2+ affinity site is not inhibited by DDT. Also, DDT is more inhibitory against the CaMg ATPase prepared from APM than the one obtained from SR. The relationship between inhibition of the CaMg ATPase by DDT in the axonic nerve membrane and poisoning symptoms of the nervous system is discussed. 相似文献
42.
Hajime Tokuda Tsutomu Unemoto 《Biochemical and biophysical research communications》1981,102(1):265-271
The membrane potential generated at pH 8.5 by K+-depleted and Na+-loaded is not collapsed by proton conductors which, instead, induce the accumulation of protons in equilibrium with the membrane potential. The generation of such a membrane potential and the accumulation of protons are specific to Na+-loaded cells at alkaline pH and are dependent on respiration. Extrusion of Na+ at pH 8.5 occurs in the presence of proton conductors unless respiration is inhibited while it is abolished by proton conductors at acidic pH. The uptake of α-aminoisobutyric acid, which is driven by the Na+-electrochemical gradient, is observed even in the presence of proton conductors at pH 8.5 but not at acidic pH. We conclude that a respiration-dependent primary electrogenic Na+ extrusion system is functioning at alkaline pH to generate the proton conductor-insensitive membrane potential and Na+ chemical gradient. 相似文献
43.
Heliodoro Célis 《Biochemical and biophysical research communications》1980,92(1):26-31
The 1-butanol extracted proteolipid from mitochondria was incorporated to liposomes. This proteolipid mediates the H+ transfer across the lipid bilayer in response to a negative charge produced by valinomycin and KCl. The process is sensitive to DCCD, but not to oligomycin. The flux of H+ depends on the concentration of proteolipid and the inhibition of this flux depends on the concentration of DCCD. 相似文献
44.
Measurements of proton translocation in CF1-depleted, N, N′-dicyclohexylcarbodiimide-resealed broken chloroplasts were made under different light intensities. Kinetic analysis of the data shows that the outward leakage of accumulated protons through CF0 is still dependent on light intensity with a first-order rate constant equal to mR0, where R0 is the initial rate of proton uptake which normally increases with light intensity and m is a characteristic constant which is independent of proton gradient and light intensity. Measurements of proton translocation in these modified chloroplasts cross-linked with glutaraldehyde under illumination and in the dark respectively suggest that the light-dependent proton leakage through CF0 is regulated by conformation change in the membrane. It is proposed that the ovserved regulation of proton leakage through the CF1.CF0 complex in native chloroplasts is for optimizing the steady state synthesis of ATP under different light intensities. 相似文献
45.
Connie R. Faltynek Jeremiah E. Silbert 《Biochemical and biophysical research communications》1978,83(4):1502-1508
A microsomal preparation from chick embryo epiphyseal cartilage was incubated with UDP-[14C]glucuronic acid and UDP-N-acetylgalactosamine to form [14C] chondroitin-labeled proteoglycan. Two [14C]proteoglycan populations were obtained which differed in size, [14C]glycosaminoglycan content, and susceptibility to alkali. One population of [14C]proteoglycan appeared near the void volume on Sepharose 2B, while the other population was smaller, similar in size to monomer proteoglycan. The larger [14C]proteoglycan contained long [14C]chondroitin chains added to short primers; these chains were in part resistant to alkali cleavage from protein. The smaller [14C]proteoglycan contained mainly [14C]chondroitin chains of intermediate length added to endogenous chondroitin sulfate; these chains were all susceptible to alkali cleavage from protein. The larger [14C]proteoglycan may represent a precursor proteoglycan present at the site of glycosaminoglycan chain synthesis. 相似文献
46.
Biochemical research on oogenesis. RNA accumulation during oogenesis of the dogfish Scyliorhinus caniculus 总被引:2,自引:0,他引:2
Four biochemical mechanisms have been shown to operate in the oocytes of amphibians and teleosts: (1) amplification of the 28 S and 18 S genes, (2) noncoordinate accumulation of 5 S RNA and 28 S + 18 S RNA, (3) storage of 5 S and transfer RNA made in excess by small oocytes within nucleoprotein particles, (4) expression of different 5 S genes in oocytes and somatic cells. We have tried to extend these observations to another group of vertebrates, i.e., selacians (Chondrichthya). Our data suggest that ribosomal gene amplification is low or absent in the oocytes of the dogfish Scyliorhinus caniculus. However, previtellogenic oocytes of this species accumulate more 5 S RNA than needed for ribosome assembly. Transfer and 5 S RNA present in small oocytes are probably not free in the cell sap. A substantial fraction of these RNAs sediments at 10 S when homogenates of immature ovaries are centrifuged in sucrose density gradients. In contrast to what we observed in amphibians and teleosts, 5 S RNA from ovaries of S. caniculus is identical in sequence to 5 S RNA from liver. Among the four mechanisms mentioned above, the second and probably the third one are used by the oocytes of S. caniculus. Mechanism (4) is absent in this species. No definitive conclusion can be drawn concerning mechanism (1), i.e., ribosomal gene amplification. 相似文献
47.
J Katz W Troll M Levy K Filkins J Russo M Levitz 《Archives of biochemistry and biophysics》1976,173(1):347-354
Direct evidence was obtained for the presence of hormone-stimulated trypsin-like protease activity in the rat uterus. Ovariectomized rats were either untreated (U), treated with estradiol (E), or estradiol plus progesterone (EP). The uteri were excised and subcellular fractions were prepared. Each fraction was assayed for protease activity using protamine as substrate, the cleavage products being quantitated fluorometrically following reaction with 4-phenylspiro[furan-2(3H),1′-phthalan]-3,3′dione (Fluram). Fractions from U rats yielded negative results, whereas the 12,000g pellets and nuclei from the uteri of E and EP rats exhibited appreciable activities. No significant increase in protease activity was observed in thymus and diaphragm following hormone treatment, indicating organ specificity. The enzyme (or enzymes) from the 12,000g pellet was solubilized and some characteristics were determined. The apparent Km is about 1.0 × 10?6m, the temperature optimum is about 44 °C and maximum velocity is achieved in the alkaline range (pH ~ 8.5). The protease is a plasminogen activator and is inhibited by diisopropyl fluorophosphate, Antipain, and Leupeptin. These properties resemble those of trypsin. 相似文献
48.
William N. Fishbein K. Nagarajan Warren Scurzi 《Archives of biochemistry and biophysics》1976,172(2):726-733
Three previously uncharacterized, nongenetic urease isozymes have been analyzed by sucrose density gradient sedimentation, gel electrophoresis, and chemical reactivity. The full complement of isozymes could be reliably generated by choosing appropriate levels of NaCl, pH, and ethylene glycol, and was stable for several days in dilute solution. The three forms of interest were found to be quaternary isomers of other isozymes, but differed from them qualitatively in their bonding sites, with disulfide bonds being substituted for noncovalent bonds. The separation of these isomer-pairs during sedimentation and electrophoresis cannot be readily explained by differences in size or charge, but must rather arise from a difference in shape. A simple two-dimensional model can provide the appropriate molecular architecture to satisfy these requirements: Only one of the two half-units in each α-urease molecule undergoes disulfide bonding during polymerization, and it does so with two adjacent molecules, thus producing asymmetric polymers from symmetric starting components. 相似文献
49.
Polymerization-deploymerization purified microtubules from mouse brain contain, in addition to tubulin, several minor proteins, including protein kinase activity. The protein kinase copurifies with microtubules in constant proportion to tubulin through two, three, or four cycles of polymerization; it can be resolved from tubulin by gel filtration chromatography and has an apparent molecular weight of 280,000. Its activity is stimulated 7-fold by cyclic AMP, and resembles the soluble brain protein kinase described by Miyamoto (1). The microtubule preparation serves as an endogenous substrate for this protein kinase; both 6S and 30S tubulin are substrates for phosphorylation to the extent of about 0.10 ± 0.05 moles/mole. 相似文献
50.
The biotransformation of pregnenolone-7alpha-3H and of progesterone-7alpha-3H by porcine fetal and maternal adrenal homogenates at 56 and 112 days of pregnancy and of dehydroepiandrosterone-7alpha-3H by fetal adrenal homogenates has been investigated in vitro. Both pregnenolone-7alpha-3H and progesterone-7alpha-3H were metabolized extensively by maternal adrenal preparations, the principal radioactive metabolites isolated being cortisol, corticosterone, 11-deoxycortisol, deoxycorticosterone, 11beta-hydroxyprogesterone and androstenedione. In addition, 17alpha-hydroxyprogesterone, 20alpha-dihydroprogesterone and cortisone were formed from both substrates and 17alpha-hydroxypregnenolone and progesterone were formed from pregnenolone. Although essentially the same radioactive metabolites were isolated after incubation of fetal adrenal glands with pregnenolone-7alpha-3H or progesterone-7alpha-3H, a greater proportion of the radioactivity was associated with corticosteroids at 112 days of pregnancy than at 56 days. 11beta-Hydroxyandrostenedione and androstenedione were isolated and identified together with an unknown polar metabolite, after incubation of fetal adrenal tissue with dehydroepiandrosterone-7alpha-3H. These results are discussed in relation to feto-placental steroid biosynthesis and metabolism and the role of the fetal adrenal in the initiation of parturition in the pig. 相似文献