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81.
R Würmli S Wolffram E Scharrer 《Comparative biochemistry and physiology. A, Comparative physiology》1987,88(1):127-129
1. The influence of nitrate and nitrite on net absorption of electrolytes (Na+, K+, Cl-) and water from ligated loops was studied at various intestinal sites in rats. 2. Nitrate strikingly reduced Cl- absorption in rat proximal and distal colon, whereas Na+ absorption was reduced only moderately. Nitrite also reduced Cl- absorption in the colon. 3. Nitrate showed no significant effect on electrolyte absorption in the small intestine. 4. The results suggest that Cl-/HCO3- on exchange is the major route of Cl- absorption in the colon, whereas this mechanism seems not to be of importance for Cl- absorption by the small intestine. 相似文献
82.
Changes in quality of blood units containing one and a half or double amounts of glucose, stored at +4 degrees C for three weeks were analysed. An experimental preservative containing glucose and fructose (1 : 1) was also used. No other additives (purine or purine-nucleoside) were applied. A standard CPD preservative of the National Inst. of Haematology and Blood Transfusion was used as control. The pH, plasma free haemoglobin, K+ content, red blood cell (RBC) ATP and 2,3-DPG content, and RBC fragility index were determined in each sample. Increase of glucose concentration, the addition of fructose had a beneficial effect on blood pH, and on plasma free haemoglobin and K+ concentration. 150% glucose improved the 2,3-DPG maintenance in stored blood. 相似文献
83.
Summary Freeze-fracture autoradiography is accepted as an adequate technique for localization studies of soluble substances at the electron microscopical level. The method, however, involves many critical preparation steps, among them a protective carbon coating of the developed nuclear emulsion adhering to the replica. We demonstrate here that this additional carbon coating may be omitted. This simplification leads to a significant improvement of the sample yield as compared with the previously described procedures.These studies were supported by the Deutsche Forschungsgemeinschaft 相似文献
84.
A cytochrome c (cyt. c) was solubilized with Triton-X-100 and co-purified with cytochrome c oxidase from membranes of chemotrophically grown cells of Rhodopseudomonas capsulata. Cyt. c and cytochrome oxidase were separated on Sephadex G-50 columns. Antibodies against cytochrome c2 from the same bacterium did not cross react with the membrane-bound cyt. c. The IEP of the membrane-bound cyt. c was found to be pH 8.2, the midpoint potential was 234 +/- 11 mV at pH 7.0. This cyt. c binds CO. The native cyt. c is a dimer with an apparent Mr of 25000 containing 2 mol heme per mol dimer, which is believed to function as an electron donor for the high-potential cytochrome c oxidase. 相似文献
85.
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87.
A two-step purification procedure for 5-aminolevulinic acid dehydratase (EC 4.2.1.24) from human red blood cells has been developed. It involves one ion exchange and one gel filtration step. The purification is about 1000-fold, and the yield is more than 85%. With the purified enzyme a direct spectrophotometric assay of product formation without subsequent reaction with Ehrlich's reagent is described. 相似文献
88.
89.
An aldehyde reductase (EC 1.1.1.2) from human liver has been purified to homogeneity. The enzyme is NADPH-dependent, prefers aromatic to aliphatic aldehydes as substrates, and is inhibited by barbiturates and hydantoins. The following physicochemical parameters were determined: molecular weight, 36,200; sedimentation coefficient, 2.9 S; Stokes radius, 2.65 nm; isoelectric point, pH 5.3; extinction coefficient at 280 nm, 54,300 M-1 cm-1. Results from polyacrylamide gel electrophoresis with and without sodium dodecyl sulfate, gel filtration, and ultracentrifugation suggest a monomeric structure. On molecule of NADPH binds to the enzyme causing a red shift of the coenzyme absorption maximum from 340 to 352 nm. The amino acid composition has been determined and a partial specific volume of 0.74 was computed from these data. An alpha-helicity of 7 and 18% was estimated from the ellipticities at 208 and 222 nm, respectively. Combination of the most reactive thiol group with p-mercuribenzoate does not cause loss of catalytic activity. Inactivation occurs when more than one thiol group is modified. The presence of NADPH or NADP+ prevents loss of activity by thiol modification. The comparison of structural features of aldehyde reductase with other monomeric and oligomeric dehydrogenases suggest similarities of aldehyde reductase with octopine dehydrogenase. 相似文献
90.