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51.
Studies of the temperature dependence (10-40 degrees C) of guanylate cyclase in rat intestinal microbillus membranes reveal a change in energy of activation (slope of the Arrhenius plot) at 30 +/- 1 degree C. The break point temperature corresponds to the lipid thermotropic transition in these membranes previously characterized by differential scanning calorimetry (range: 23-39 degrees C; peak temperature, 31 degrees C). The break point temperature for guanylate cyclase also corresponds to that of a number of other microbillus membrane enzymes and of D-glucose transport. These activities are defined as "intrinsic" membrane activities by this operational criterion. Treatment with the nonionic detergent Lubrol WX increased the guanylate cyclase activity 4- to 8-fold and removed the discontinuity in the Arrhenius plot. 相似文献
52.
A kinetic study was made of the relationship between respiration rate, sugar content and ATP levels, in fresh and aged potato tubers stored at 4°. The ATP content in tubers rose rapidly immediately after the chilling stress, while respiration rate decreased below the initial rate and sugar accumulation was not detected. After 4 days of storage, the ATP level declined and the sugars started to accumulate. The typical increase in respiration rate that usually follows chilling stress, appeared only in fresh tubers (at about the 6th day of storage). In dinitrophenol-treated tubers, the ATP level remained below the initial level and sugar accumulation was blocked completely. The evidence presented suggests that ATP elevation is not generated by the respiration burst. 相似文献
53.
Summary A 1730-g male infant, born at 37 weeks gestation, had multiple congenital anomalies, consisting of microcephaly, hypertelorism, bilateral cleft lip and palate, micrognathia, lowset ears, and cryptorchidism. Chromosome analysis showed a recombinant 22 derived from the paternal inversion (22) (p13q12.2). The proband's karyotype is 46,XY,rec(22),dup q,inv(22)(p13q12.2)pat, which has a duplication of q12.2qter. An identical recombinant has been reported in a female infant in Mexico whose mother was a carrier of the inversion. Similar congenital anomalies present in these two patients demonstrate the phenotype of duplication of the distal long arm 22. This report also documents the occurrence of an identical inversion in two apparently unrelated Mexican families. 相似文献
54.
M F Mottola J H Plust P D Christopher C L Schachter 《Canadian journal of physiology and pharmacology》1992,70(12):1634-1638
The purpose of the present study was to examine the effects of exercise on maternal glycogen storage patterns and fetal outcome in mature (approximately 12 months of age) Sprague-Dawley rats. The exercise consisted of treadmill running at 30 m.min-1, on a 10 degree incline, for 60 min, 5 days per week, for 4 weeks prior to pregnancy, which continued until day 19 of gestation. In mature animals, chronic exercise increased (p < 0.05) liver glycogen concentration in both pregnant and nonpregnant rats. In pregnant exercised animals, the glycogen concentration of the maternal liver increased almost twofold (p < 0.05) compared with the sedentary pregnant group. There was no difference in the amount of glycogen stored in the gastrocnemius or soleus muscles in response to training, pregnancy, or chronic maternal exercise in the mature rat. In the pregnant groups, there were fewer (p < 0.05) viable fetuses and more (p < 0.05) resorption sites than in young rats. In addition, exercise during pregnancy in the mature animal decreased (p < 0.05) fetal body weight. These results demonstrate that a conflict may exist between maternal exercise and fetal demands for energy in the mature rat. This conflict seems to favour the maternal system, as evidenced by the enhanced maternal liver glycogen storage and the negative effect on fetal growth. 相似文献
55.
56.
Miriam Bloom 《American journal of botany》1976,63(4):399-405
A clear dichotomy exists in the genus Ruellia, separating the blue from the red flowered species. Flavonoids differ in a qualitative rather than a quantitative way. Apigenin 7-glucuronide and malvidin 3,5-diglucoside are common to all the blue flowered species, whereas chalcononaringenin 2'-glucoside (isosalipurposide) and pelargonidin 3,5-diglucoside are shared by the red flowered ones. The blue flowered species are linked with the red via apigenin 7-glucuronide and 3,5-diglucosylation of their respective anthocyanins. Both groups are involved in flavonoid race formation. All examined species (and some populations within species) differ in flavonoid content. The patterns of variability displayed provide a basis upon which an evolutionary scheme is constructed. Genetic drift is hypothesized as the effector of race formation in the blue flowered group. 相似文献
57.
J.Ronald Munro Saroja Narasimhan Steve Wetmore J.R. Riordan Harry Schachter 《Archives of biochemistry and biophysics》1975,169(1):269-277
A GDP-l-fucose:glycoprotein fucosyltransferase which transfers l-fucose to terminal β-N-acetyl-d-glucosaminyl residues of sialidase-, β-galactosidase-treated α1-acid glycoprotein and a CMP-sialic acid:glycoprotein sialyltransferase acting on sialidase-treated apolipoprotein-Ala1 from human very low density lipoprotein have been shown to be concentrated in rat liver Golgi apparatus preparations at enrichments of 40- and 45-fold, respectively, and in pork liver Golgi-rich fractions at enrichments of 35- and 20-fold, respectively. A second fucosyltransferase acting on sialidase-treated α1-acid glycopretein was absent from rat liver and was enriched only 13-fold in a pork liver Golgi-rich fraction. The smooth-surfaced microsome fraction was the only other rat liver subcellular fraction with appreciable levels of the GDP-l-fucose: β-N-acetyl-d-glucosaminide fucosyltransferase and the lipoprotein sialyltransferase (enrichments of 2.6- and 5.2-fold, respectivley). This enrichment could not be attributed to the plasma membrane content of the smooth microsome fraction since plasma membrane fractions from rat liver were shown to have relatively low concentrations of these two transferases (enrichments of 0.3 or less). Rat liver plasma membrane was also shown to have similarly low relative specific activities for three other glycosyltransferases (sialyl-, galactosyl-, and N-acetylglucosaminyl-). The accurate determination of the glycosyltransferase activities of the plasma membrane fraction required the use of relatively low concentrations of plasma membrane and relatively high concentrations of nucleotide-sugars in order to avoid interference by the high nucleotide-sugar pyrophosphatase and hydrolase activities of this fraction. 相似文献
58.
59.
Leon Salganicoff Patricia A. Hebda John Yandrasitz Miriam H. Fukami 《Biochimica et Biophysica Acta (BBA)/General Subjects》1975,385(2):394-411
Subcellular components were obtained from pig platelets, disrupted by means of a French press and separated into 4 primary fractions. The granule fraction (10 000 g) was subjected to a sucrose gradient fractionation. Primary fractions and the granule subfractions were studied electron microscopically and biochemically by following the distribution of markers of membranes, lysosomes of α-granules, mitochondria and dense granules. With this technique of platelet homogenization, 80% of the serotonin and 93% of the β-N-acetylglucosaminidase were found to be particulate. In the gradient, mitochondria were sharply banded in a fraction (density 1.16–1.17) having a specific activity 10–100 times higher than the other fractions of the gradient. Serotonin-containing granules were found in a pellet of density greater than 1.27 and contained 60% of the serotonin and adenine nucleotides of the granule fraction. The lysosome markers that were monitored, acid phosphatase and β-N-acetylglucosaminidase, exhibited different distribution patterns. Acid phosphatase showed the highest specific activity in the microsomal fraction with only 2.8% in the granule fraction, and this latter amount also appeared to be associated with membranes upon further fractionation. β-N-Acetylglucosaminidase was present in both the granule fraction and in the microsomal fraction with nearly the same specific activity. However, that present in the granule fraction was clearly associated with granules that distributed over a wide range of densities on a sucrose gradient. The calcium distribution was followed to attempt to determine its subcellular location; 19% was found in the same subfraction as the serotonin-containing granules, but at least 50% of the particulate calcium was associated with granules distinctly separate from the storage granules. 相似文献
60.
Ian D. Stephen Miriam J. Law Smith Michael R. Stirrat David I. Perrett 《International journal of primatology》2009,30(6):845-857
Numerous researchers have examined the effects of skin condition, including texture and color, on the perception of health,
age, and attractiveness in human faces. They have focused on facial color distribution, homogeneity of pigmentation, or skin
quality. We here investigate the role of overall skin color in determining perceptions of health from faces by allowing participants
to manipulate the skin portions of color-calibrated Caucasian face photographs along CIELab color axes. To enhance healthy
appearance, participants increased skin redness (a*), providing additional support for previous findings that skin blood color enhances the healthy appearance of faces. Participants
also increased skin yellowness (b*) and lightness (L*), suggesting a role for high carotenoid and low melanin coloration in the healthy appearance of faces. The color preferences
described here resemble the red and yellow color cues to health displayed by many species of nonhuman animals. 相似文献