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41.
A S Abramovitz J Y Hong V Randolph 《Biochemical and biophysical research communications》1983,117(1):22-29
We have previously reported the purification of polypeptides from soybean which are potent inhibitors of superoxide production by human neutrophils. We now report that neither oxygen uptake nor hydrogen peroxide production by stimulated neutrophils is affected by these inhibitors. Furthermore, the E-1 and E-3 polypeptides inhibit ferricytochrome c reduction by a xanthine oxidase superoxide generation system. The inhibitory activity of E-3 in the model system is blocked by 1 mM KCN while E-1 is only slightly cyanide sensitive. Atomic absorption analysis of E-1 and E-3 polypeptides reveal copper in the latter and manganese in the former. Thus, E-3 is a copper-containing superoxide dismutase while E-1 appears to be a manganese-containing superoxide dismutase. 相似文献
42.
Crosslinking of chromosomal proteins to DNA in HeLa cells by UV gamma radiation and some antitumor drugs 总被引:1,自引:0,他引:1
Z M Banjar L S Hnilica R C Briggs J Stein G Stein 《Biochemical and biophysical research communications》1983,114(2):767-773
Immunochemical techniques were used to investigate the protein-DNA crosslinking by ultraviolet (UV) and gamma radiation as well as 1,3-bis-(2-chloroethyl)-1-nitrosourea (BCNU) or cis- and trans-diamminedichloroplatinum II (cis-DDP and trans-DDP). Antisera to 0.35 M NaCl extract and 0.35 M NaCl residue of HeLa nuclei were employed. Both gamma and UV irradiation, exposure to cis- or trans-DDP and, to a lesser extent, BCNU, resulted in crosslinking of various antigens to the DNA. Although several antigens were crosslinked by all the employed agents, other exhibited agent-specific crosslinking patterns. 相似文献
43.
Amino acid sequence homology between rat prostatic steroid binding protein and rabbit uteroglobin 总被引:2,自引:0,他引:2
M E Baker 《Biochemical and biophysical research communications》1983,114(1):325-330
Using a computer program designed to detect evolutionary relationships between proteins, I find that the polypeptide chain of rabbit uteroglobin has amino acid sequence homology with the C1 and C2 polypeptide chains of rat prostatic steroid binding protein. Using this finding I suggest several interesting approaches for studying the biology of these proteins. 相似文献
44.
The herbicide glyphosate (N-phosphonomethyl glycine) is a potent reversible inhibitor of the 5-enolpyruvylshikimate-3-phosphate (EPSP) synthase activity of the purified arom multienzyme complex from Neurospora crassa. Inhibition of the EPSP synthase reaction by glyphosate is competitive with respect to phosphoenolpyruvate, with K(i) 1.1 microM, and uncompetitive with respect to shikimate-3-phosphate. The kinetic patterns are consistent with a compulsory order sequential mechanism in which either PEP or glyphosate can bind to an enzyme: shikimate-3-phosphate complex. 相似文献
45.
A stimulating effect of guanyl nucleotides on the rat-liver soluble cyclic GMP high-affinity phosphodiesterase activity 总被引:1,自引:0,他引:1
The high affinity (low Km) cyclic GMP phosphodiesterase (PDE) is activated by GTP, while the cyclic AMP PDE is not. GTP and its hydrolysis-resistant analogue, guanylylimidodiphosphate (GppNHp), display a half-maximal stimulating effect at almost the same concentration (5 X 10(-6) M). The GTP stimulating effect is not observed when the socalled cyclic GMP low affinity (high Km) PDE is operative. GTP cooperates with the increase of the substrate concentration on removing the IBMX inhibitory effect. The isolation through a classical chromatographic procedure on a DEAE-cellulose column, of a PDE fraction specific for cyclic GMP, results in the loss of the GTP stimulating effect. 相似文献
46.
Cytosol from rabbit heart and slow and fast skeletal muscles was fractionated using (NH4)2SO4 to yield three cytosolic protein fractions, viz., CPF-I (protein precipitated at 30% saturation), CPF-II (protein precipitated between 30 and 60% saturation), and cytosol supernatant (protein soluble at 60% saturation). The protein fractions were dialysed and tested for their effects on ATP-dependent, oxalate-supported Ca2+ uptake by sarcoplasmic reticulum from heart and slow and fast skeletal muscles. CPF-I from heart and slow muscle, but not from fast muscle, caused marked inhibition (up to 95%) of Ca2+ uptake by sarcoplasmic reticulum from heart and from slow and fast muscles. Neither unfractionated cytosol nor CPF-II or cytosol supernatant from any of the muscles altered the Ca2+ uptake activity of sarcoplasmic reticulum. Studies on the characteristics of inhibition of sarcoplasmic reticulum Ca2+ uptake by CPF-I (from heart and slow muscle) revealed the following: (a) Inhibition was concentration- and temperature-dependent (50% inhibition with approx. 80 to 100 μg CPF-I; seen only at temperatures above 20°C). (b) The inhibitor reduced the velocity of Ca2+ uptake without appreciably influencing the apparent affinity of the transport system for Ca2+. (c) Inhibition was uncompetitive with respect to ATP. (d) Sarcoplasmic reticulum washed following exposure to CPF-I showed reduced rates of Ca2+ uptake, indicating that inhibition results from an interaction of the inhibitor with the sarcoplasmic reticulum membrane. (e) Concomitant with the inhibition of Ca2+ uptake, CPF-I also inhibited the Ca2+-ATPase activity of sarcoplasmic reticulum. (f) Heat-treatment of CPF-I led to loss of inhibitor activity, whereas exposure to trypsin appeared to enhance its inhibitory effect. (g) Addition of CPF-I to Ca2+-preloaded sarcoplasmic reticulum vesicles did not promote Ca2+ release from the vesicles. These results demonstrate the presence of a soluble protein inhibitor of sarcoplasmic reticulum Ca2+ pump in heart and slow skeletal muscle but not in fast skeletal muscle. The characteristics of the inhibitor and its apparently selective distribution suggest a potentially important role for it in the in vivo regulation of sarcoplasmic reticulum Ca2+ pump, and therefore in determining the duration of Ca2+ signal in slow-contracting muscle fibers. 相似文献
47.
The membrane (Na+ + Mg2+)-ATPase of Acholeplasma laidlawii B has been solubilized with a Brij-58/sodium deoxycholate mixture and purified by a combination of gel filtration and ion-exchange chromatography. The purified, partially delipidated ATPase has a specific activity of 195 μmol Pi/mg protein per h, which could be enhanced by 25% upon the addition of exogenous phospholipids. The kinetic properties of the purified enzyme are similar to those of the native membrane-bound enzyme, suggesting that it has not been substantially altered during the purification procedure. The enzyme is an assembly of five polypeptide species and its kinetic properties suggest that it is dissimilar to other known ATPases. 相似文献
48.
We previously demonstrated inhibition of Na+-dependent 32Pi transport in canine renal brush-border membranes in association with NAD+-induced ADP ribosylation of membrane protein(s) and postulated that NAD+ inhibits Pi transport across the brush-border membrane via ADP ribosylation. Recently it was shown that incubation of rat brush-border membrane with NAD+ resulted in release of Pi which was prevented by EDTA. It was proposed that NAD+-mediated inhibition of 32Pi transport might occur through this mechanism. To determine whether NAD+ inhibited 32Pi transport by a mechanism other than or in addition to release of Pi, we compared Na+-dependent 32Pi counterflow in brush-border membrane equilibrated with Pi or with Pi generated from NAD+. Release of Pi from NAD+ incubated with brush-border membrane was confirmed. The increased uptake of 32Pi which was demonstrated in brush-border membrane equilibrated with Pi was not measured when intravesicular Pi was generated from a concentration of NAD+ which effected ADP-ribosylation of brush border membranes (100 μM NAD+). In contrast, increased uptake of 32Pi was demonstrated when intravesicular Pi was generated from 1 μM NAD+ which did not effect ADP ribosylation. Mg2+-dependent ADP ribosylation of brush-border membrane incubated with NAD+ was demonstrated which persisted during the time interval of 32Pi uptake measurements. Our findings are compatible with the hypothesis that NAD+-induced ADP ribosylation of brush-border membrane protein(s) results in inhibition of Pi transport across the membrane in vivo. EDTA may act to prevent this inhibition in brush-border membrane by chelation of Mg2+ and decreased ADP ribosylation. 相似文献
49.
The postribosomal particle of rabbit liver contains protein-synthesis factors and serum albumin mRNA
As demonstrated by indirect immunoprecipitation and polyacrylamide gel electrophoresis, an 85S particle separated by sucrose density-gradient centrifugation from the postribosomal pellet of rabbit liver, is able to synthesize serum albumin if supplemented with both ribosomal subunits and sources of energy. It is retained on heparin bound to Sepharose 4B, contains translatable mRNA and apparently all protein factors required for translation. This particle may represent a highly organized protein synthesizing machinery, the combination of which with ribosomes results in formation of new protein molecules. 相似文献
50.
F Peillon A M Brandi D Bression M Le Dafniet J Racadot 《Biochemical and biophysical research communications》1983,112(1):42-46
The ability of 2-Hydroxyestradiol, a catecholestrogen, and 17 beta Estradiol to interact with the dopamine inhibition of prolactin and with dopamine receptors has been tested on dispersed human prolactin-secreting cells obtained from ten pituitary adenomas. There is a 80% inhibition of prolactin secretion obtained by addition of dopamine in a superfusion system. This inhibition is not affected by preexposure to the steroids, or by their introduction into the perifusion medium. Moreover 2 Hydroxyestradiol and 17 beta Estradiol do not interact with the binding of 3H Domperidone to DA receptors. 相似文献