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711.
Serum albumin is known to act as a carrier for a variety of molecules and metal ions. This property of the protein could be due to the presence of different types of secondary structures in its molecules. The most commonly known are the α-helix, β-sheets, β-turns and random coil forms. A rigorous analysis of human serum albumin has been carried out by using four different approaches. Comparative studies have revealed that the segment Asp 107 to Val 122 of this protein assumes a γ-helical structure. Under favourable circumstances, two prolines at the i and (i + 5)th positions can initiate a γ-helix. Further requirements for the formation and stability of γ-helix are discussed. 相似文献
712.
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714.
K. K. Vaas H. S. Raina R. K. Langer Shyam Sunder 《International Review of Hydrobiology》1988,73(5):547-558
The energy transfer at different trophic levels in a temperate lake ecosystem locally called Sar (lake) has been investigated. Total phytoplankton production in terms of energy fixation has been estimated at 3.2 × 106 cal m−2 y−1, out of which the fish harvest amounts to 2640 cal m−2 y−1. The conversion efficiency from phytoplankton to fish has been estimated at 0.082 %. Apart from other ecological parameters discussed in the paper, suggestions for the efficient use of other available energy from the system has been highlighted. 相似文献
715.
We observed a group of capped langurs for 12 mo in the Pakhui Wildlife Sanctuary, Arunachal Pradesh, India. We recorded the
time of feeding on different food plant species, food categories, and the feeding heights of monkeys in trees. Capped langurs
spent 68% of their feeding time on leaves, 16% on flowers, and 16% on fruits. Feeding on leaves was consistently high (p < 0.01) during the year, with the highest feeding in May (85%) and the lowest in January (47%). The seasonal difference in
feeding on leaves is significant (p < 0.05): it was higher in summer and during monsoon. The feeding time on flowers was maximal (35%) in March and that on fruits
and seeds was minimal (38%) in January. Langurs ate 52 plant species throughout the year. The largest number of plants (6)
were species of Moraceae, and langurs spent more feeding time (20%) on them alone. The number of plants eaten per month varied
significantly (p < 0.05). Langurs ate Gmelina arborea, Albizzia lucida, Ficus glomereta, and Makania micrantha throughout the year. They spent 44% of their feeding time in terminal canopies and their average feeding height was 30–35 m.
This is the first study to examine the feeding ecology of capped langurs and provides baseline data for the species. 相似文献
716.
A histochemical analysis of mucous cells in the gills, buccal cavity and epidermis of the nine-spined stickleback, Pungitius pungitius L., using alcian blue and PAS, showed that most cells contained more than one type of glycoprotein. In all regions, the cell content of sialylated glycoproteins increased, and of sulphated glycoproteins decreased during adaptation to sea water. The histochemical properties of the cuticle-secreting cells in the epidermis were less easy to study, but it seems that their content of neutral glycoproteins increased and their content of acid glycoproteins decreased, during adaptation to sea water. Mucous cells were generally less common in seawater-adapted animals, though in the epidermis of fish kept in sea water for 21 days, there were as many as in the freshwater controls. Sulphated glycoproteins may be more effective than others in freshwater osmoregulation for they are highly charged and could attract cations strongly. They may also help to combat bacterial and fungal infections, and perhaps these are less likely when laboratory fish are transferred to sea water. 相似文献
717.
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719.
The interactions of flavin mononucleotide (riboflavin-5'-monophosphate) with two polypeptides, poly-(α-L-lysine) and poly-(α-L-histidine)
in water and 0.05 M phosphate buffer were studied by measuring circular dichroism in the pH range 3 to 11. The interation
of flavin mononucleotide with the two polypeptides was due to hydrophobic as well as ionic associations and was further influenced
by the involvement of the ribityl side chain. The results of the present study have shown that small changes in the environmental
conditions of the interacting molecules could modify their mode of interaction considerably.
CDRI Communication No. 2816. 相似文献
720.
Cytotoxic and DNA-damaging effects of 1,2-bis(sulfonyl)hydrazines on human cells of the Mer+ and Mer- phenotype 总被引:1,自引:0,他引:1
A series of 1,2-bis(sulfonyl)hydrazines with the capacity to function as alkylating agents have been evaluated for their toxicity towards Mer- HT29 and Mer- BE cells, and for their ability to produce DNA damage expressed as single-strand breaks and DNA interstrand cross-links. Compounds of this class with methylating potential showed a marked difference in their capacity to inhibit the growth of Mer- and Mer+ cells, being considerably more toxic to BE Mer- cells. Dose-dependent DNA single-strand breaks were induced by these agents, with the quantity of breaks produced in Mer- and Mer+ cells being essentially the same. Maintenance of these lesions did not appear to explain the differential in toxicity to BE and HT29 cells. A chloroethylating compound of this class was also more toxic to Mer- BE cells than to Mer+ HT29 cells, but the differential toxicity was considerably less than that of the methylating agents of the series. The chloroethylating agent did not produce measurable single-strand breaks of the DNA of treated cells, but caused more DNA interstrand cross-links in Mer- cells than in Mer+ cells. Thus, DNA interstrand cross-links may be at least in part responsible for the cell kill produced by this agent. The findings suggest that methylating and chloroethylating derivatives of the 1,2-bis(sulfonyl)hydrazine family have different biochemical determinants of their cytodestructive actions. 相似文献