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91.
Endothelin-3 stimulates production of endothelium-derived nitric oxide via phosphoinositide breakdown. 总被引:7,自引:0,他引:7
T Emori Y Hirata K Kanno K Ohta S Eguchi T Imai M Shichiri F Marumo 《Biochemical and biophysical research communications》1991,174(1):228-235
Cultured bovine endothelial cells (EC) have specific receptors for endothelin (ET)-3 functionally coupled to phosphoinositide breakdown. We studied whether ET-3 stimulates synthesis of nitric oxide (NO), an endothelium-derived relaxing factor that activates soluble guanylate cyclase in EC, and whether the ET-3-induced NO formation involves G-proteins. ET-3 dose-dependently stimulated production of intracellular cGMP in EC, of which effects were abolished by pretreatment with NG-monomethyl L-arginine, an inhibitor of NO synthesis, and methylene blue, an inhibitor of soluble guanylate cyclase. The stimulatory effects of ET-3 on cGMP production, inositol trisphosphate formation and increase in cytosolic free Ca2+ concentration were similarly blocked by pretreatment with pertussis toxin (PTX). These data suggest that ET-3 induces synthesis of NO mediated by phosphoinositide breakdown via PTX-sensitive G-protein in EC. 相似文献
92.
Annual production rates of reproductive organs inFagus crenata forests in the lower area of the species' range were studied using 10 litter traps in 1980–1986. The production rates of
dispersed pollen were estimated by multiplying the number of fallen male inflorescences per ha per year by the mean amount
of pollen per inflorescence before anthesis. Large annual fluctuations in the production rates of male and female inflorescences
were recognized, whereas their annual trends were synchronized with each other. Pollen production rates were within the range
1.0–6900 (mean: 1630)×109ha−1 yr−1, the maximum/minimum ratio attaining 7000.F. crenata was the lowest producer of pollen among seven tree species studied: the number of pollen grains equivalent to a single ovule
was in the range 6.0–14×104. Furthermore, the mean dry weight of a single pollen grain (3.77×10−5mg) was higher than for wind-pollinated species. Three factors seemed to cause the low seed fertility ofF. crenata. The dry-matter production rate in the best seed year reached 3252 kg ha−1 yr−1, of which pollen accounted for 259 kg ha−1 yr−1. Unproductive years with less than 10% of the maximum production occurred four times in a 7-yr period. In such years there
were fewer male and female inflorescences, and more fruit dropped as a result of insect damage. Lower nut dissemination would
play an important role in suppressing any increase in nut predators, and fewer flowers would be produced to avoid wastage
of photosynthates in a cool-temperate climate. 相似文献
93.
94.
Carboxyphosphonoenolpyruvate phosphonomutase, a novel enzyme catalyzing C-P bond formation. 总被引:4,自引:3,他引:1 下载免费PDF全文
T Hidaka S Imai O Hara H Anzai T Murakami K Nagaoka H Seto 《Journal of bacteriology》1990,172(6):3066-3072
An enzyme catalyzing the formation of an unusual C-P bond that is involved in the biosynthesis of the antibiotic bialaphos (BA) was isolated from the cell extract of a mutant (NP71) of Streptomyces hygroscopicus SF1293. This enzyme, carboxyphosphonoenolpyruvate (CPEP) phosphonomutase, was first identified as a protein lacking in a mutant (NP213) defective in one of the steps in the pathway to BA. The first 30 residues of the amino terminus of this protein were identical to those predicted by the nucleotide sequence of the gene that restored BA production to NP213. The substrate of the enzyme, a P-carboxylated derivative of phosphoenolpyruvate named CPEP, was also isolated from the broth filtrate of NP213 as a new biosynthetic intermediate of BA. CPEP phosphonomutase catalyzes the rearrangement of the carboxyphosphono group of CPEP to form the C-P bond of phosphinopyruvate. 相似文献
95.
cDNA for chimeric protein, P450(3P4), consisting of the amino-terminal 43 residues (the membrane-anchor region) of rabbit P450IIC14 and the remaining 447 residues of rabbit P450IIE1 was constructed, then cloned into expression vector pAAH5, and expressed in Saccharomyces cerevisiae AH22 cells under the control of yeast ADH1 promoter. P450(3P4) thus synthesized in the transformed yeast cells was partially purified, and its spectral and catalytic properties were examined. In the oxidized state P450(3P4) exhibited a high-spin type absorption spectrum even in the absence of a substrate. The reduced CO complex of the P450 showed a Soret absorption maximum at 452 nm. P450(3P4) catalyzed aniline p-hydroxylation, N-nitrosodimethylamine demethylation, benzphetamine N-demethylation, and laurate and caprate (omega-1)-hydroxylation in the reconstituted system containing the P450 and NADPH-P450 reductase. These results indicate that P450(3P4) preparation obtained from the transformed yeast cells has spectral and catalytic characteristics identical with those of P450IIE1 purified from rabbit liver microsomes, confirming the substrate specificity reported of P450IIE1. 相似文献
96.
97.
K Ohta Y Hirata T Imai K Kanno T Emori M Shichiri F Marumo 《Biochemical and biophysical research communications》1990,169(2):578-584
To elucidate the mechanism by which endothelin-1 (ET-1) is released from renal epithelial cells, we have investigated the effects of several compounds on release of ET-1-like immunoreactivity (LI) from LLCPK1 cell line. Thrombin, transforming growth factor-beta, cytokines (tumor necrotizing factor-alpha, interleukin-1 beta), and phorbol ester stimulated ET-1-LI release in a time- and dose-dependent manner. The cytokine-induced ET-1-LI release was not affected by indomethacin. Northern blot analysis using cDNA for porcine preproET-1 as a probe revealed a single major band corresponding to the size of ET-1 mRNA in LLCPK1. These data indicate that the preproET-1 gene is also expressed in renal epithelial cells and the release of ET-1 from renal cells is regulated by the similar mechanism to that from endothelial cells. 相似文献
98.
K Ikeda Y Imai M Fukase T Fujita 《Biochemical and biophysical research communications》1990,168(3):889-897
The influence of 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] on adenylate cyclase responsiveness in cultured osteoblastic cells was studied using a human osteosarcoma cell line SaOS-2. 1,25(OH)2D3 treatment had no effect on cell growth, cell protein and alkaline phosphatase activity. 1,25(OH)2D3 did not alter the basal production of cyclic AMP (cAMP) in intact cells, but the cAMP formation in response to parathyroid hormone (PTH), isoproterenol (ISO) and cholera toxin was attenuated by 1,25(OH)2D3. The response to forskolin, however, was unaffected by 1,25(OH)2D3 treatment. Islet activating protein failed to modify these 1,25(OH)2D3 effect. In cell free experiments, 1,25(OH)2D3 showed similar effect--that is, PTH and ISO-stimulated adenylate cyclase activity were attenuated, but forskolin-stimulated adenylate cyclase was unaffected. 1,25(OH)2D3 treatment had no effect on the kinetics of PTH binding to PTH receptor and on the ADP ribosylation of GTP stimulatory binding protein (Gs) in SaOS-2 cells. According to these results, 1,25(OH)2D3 appeared to change the coupling of Gs with adenylate cyclase, but does not affect receptor, Gs and adenylate cyclase themselves, nor GTP inhibitory binding protein. 相似文献
99.
Inflammatory pseudotumor of the lung diagnosed as granulomatous lesion by preoperative brushing cytology. A case report 总被引:1,自引:0,他引:1
The clinical and cytologic features of a case of inflammatory pseudotumor of the lung are presented. Chest roentgenograms revealed a solitary circumscribed round mass in a nine-year-old boy. The mass was diagnosed as a granulomatous lesion by bronchoscopic brushing cytology. Although smears and cultures of sputum and brushing specimens were negative for tuberculosis, a tuberculin reaction was positive and antitubercular therapy was instituted. Since the mass had grown further after six months of therapy, an open lung biopsy was performed to resect the lesion and establish the diagnosis. Imprint smears of the cut surface of the lesion showed cytologic features similar to those of the brushings: short, spindle-shaped cells with a tendency to be arranged in stori-form patterns against a background of minimal necrotic debris. Histopathology established the final diagnosis of inflammatory pseudotumor, a rare granulomatous lesion radiologically resembling a true tumor. Since this lesion usually occurs in younger patients, inflammatory pseudotumor should be considered in pediatric cases with an intrapulmonary lesion that shows histiocytic spindle-shaped cells in stori-form patterns, but whose smears and cultures test negative for tuberculosis. 相似文献
100.
Incubation in the presence of NADPH and molecular oxygen of 14C-labeled polychlorinated biphenyls (PCBs) and two tetrachlorobiphenyl (TCB) isomers with a reconstituted system containing NADPH-cytochrome P-450 reductase and cytochrome P-450, both purified from liver microsomes of phenobarbital(PB)-pretreated rabbits, led to covalent binding of radioactive metabolites of PCBs and TCBs to the protein components of the system. A rabbit liver cytosol fraction added to the system provided more binding sites for the activated metabolites and thus increased the extent of binding markedly. The binding reaction depended absolutely on the reductase, cytochrome P-450 and NADPH, and required dilauroyl phosphatidylcholine and sodium cholate for maximal activity. A further stimulation of the binding was attained by including cytochrome b5 in the reconstituted system. Four forms of cytochrome P-450, purified from liver microsomes of PB- and 3-methylcholanthrene(MC)-treated rabbits and rats, were used to reconstitute the PCB- and TCB-metabolizing systems, and it was found that PB-inducible forms of the cytochrome from both animals were more active than those inducible by MC in catalyzing the PCB- and TCB-binding reaction. Sodium dodecyl sulfate(SDS)-polyacrylamide gel electrophoresis indicated that, in the system containing the reductase, cytochrome P-450 and cytochrome b5, PCB metabolites bound to the reductase and cytochrome P-450, but not to cytochrome b5. In the presence of the liver cytosol fraction, the binding took place to many cytosolic proteins in addition to the reductase and cytochrome P-450. 相似文献