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21.
Cells J. Victor Nadler 《Journal of neurochemistry》1987,49(4):1155-1160
Na+-dependent uptake of L-[3H]proline was measured in a crude synaptosomal preparation from the entire rat hippocampal formation or from isolated hippocampal regions. Among hippocampal regions, Na+-dependent proline uptake was significantly greater in areas CA1 and CA2-CA3-CA4 than in the fascia dentata, whereas there was no marked regional difference in the distribution of Na+-dependent gamma-[14C]aminobutyric acid ([14C]GABA) uptake. A bilateral kainic acid lesion, which destroyed most of the CA3 hippocampal pyramidal cells, reduced Na+-dependent proline uptake by an average of 41% in area CA1 and 52% in area CA2-CA3-CA4, without affecting the Na+-dependent uptake of GABA. In the fascia dentata, neither proline nor GABA uptake was significantly altered. Kinetic studies suggested that hippocampal synaptosomes take up proline by both a high-affinity (KT = 6.7 microM) and a low-affinity (KT = 290 microM) Na+-dependent process, whereas L-[14C]glutamate is taken up predominantly by a high-affinity (KT = 6.1 microM) process. A bilateral kainic acid lesion reduced the Vmax of high-affinity proline uptake by an average of 72%, the Vmax of low-affinity proline uptake by 44%, and the Vmax of high affinity glutamate uptake by 43%, without significantly changing the affinity of the transport carriers for substrate. Ipsilateral-commissural projections of CA3 hippocampal pyramidal cells appear to possess nearly as great a capacity for taking up proline as for taking up glutamate, a probable transmitter of these pathways. Therefore proline may play an important role in transmission at synapses made by the CA3-derived Schaffer collateral, commissural, and ipsilateral associational fibers. 相似文献
22.
Book reviewed in this article:
The Psychomedical Case History of a Low-Caste Woman of North India . Ruth S. Freed and Stanley A. Freed.
Fertility, Sterilization, and Population Growth in Shanti Nagar, India: A Longitudinal Ethnographic Approach . Stanley A. Freed and Ruth S. Freed. 相似文献
The Psychomedical Case History of a Low-Caste Woman of North India . Ruth S. Freed and Stanley A. Freed.
Fertility, Sterilization, and Population Growth in Shanti Nagar, India: A Longitudinal Ethnographic Approach . Stanley A. Freed and Ruth S. Freed. 相似文献
23.
24.
Victor Chude 《Plant and Soil》1988,112(2):293-295
The profile distribution of total and extractable B was determined in 16 Nigerian cacao-growing soil profiles formed from
different parent materials. Total B for all soils ranged from 8 to 54μgg−1 with a mean of 24μgg−1. The soils formed from sandstones in the rainforest zone contained higher amounts of total B than soils derived from basement
complex. Boron extractable in hot water, in 0.1% CaCl2, and in 1N NH4OAc varied from 0.13 to 1.38, 0.44 to 1.20 0.03 to 0.56μgg−1 respectively. The corresponding means were 0.66, 0.75 and 0.27μgg−1 B. Soils on metamorphic rocks gave the highest values. All extractable B values were related to organic matter while only
CaCl2-extractable B correlated with total B. Generally total and extractable B values were higher in the top soils than in the
subsoils. 相似文献
25.
Manickam Sugumaran Steven J. Saul Victor Semensi 《Archives of insect biochemistry and physiology》1988,9(4):269-281
The mechanism of formation of quinone methide from the sclerotizing precursor N-acetyldopamine (NADA) was studied using three different cuticular enzyme systems viz. Sarcophaga bullata larval cuticle, Manduca sexta pharate pupae, and Periplaneta americana presclerotized adult cuticle. All three cuticular samples readily oxidized NADA. During the enzyme-catalyzed oxidation, the majority of NADA oxidized became bound covalently to the cuticle through the side chain with the retention of o-diphenolic function, while a minor amount was recovered as N-acetylnorepinephrine (NANE). Cuticle treated with NADA readily released 2-hydroxy-3′,4′-dihydroxyacetophenone on mild acid hydrolysis confirming the operation of quinone methide sclerotization. Attempts to demonstrate the direct formation of NADA-quinone methide by trapping experiments with N-acetylcysteine surprisingly yielded NADA-quinone-N-acetylcysteine adduct rather than the expected NADA-quinone methide-N-acetylcysteine adduct. These results are indicative of NADA oxidation to NADA-quinone and its subsequent isomerization to NADA-quinone methide. Accordingly, all three cuticular samples exhibited the presence of an isomerase, which catalyzed the conversion of NADA-quinone to NADA-quinone methide as evidenced by the formation of NANE—the water adduct of quinone methide. Thus, in association with phenoloxidase, newly discovered quinone methide isomerase seems to generate quinone methides and provide them for quinone methide sclerotization. 相似文献
26.
Victor N. Mikheev Dmitry S. Pavlov Daria Pakulska 《Environmental Biology of Fishes》1992,35(4):351-360
Synopsis Swimming speed and swimming path of goldfish and tetra larvae were studied in aquaria containing food patches composed of decapsulated cysts and immobilized nauplii of Artemia salina or sparsely distributed prey. The mean swimming speed of starved larvae in the medium without food was about four times higher than the speed of larvae feeding in a patch. Satiated larvae swam about 1.5 times slower than hungry fish. Consumption of single prey items by starved larvae caused the following sequence of swimming responses: handling pause (cessation of swimming), slow swimming in a restricted area, and fast swimming (approximately twice as fast as hungry larvae before encountering food) accompanied by a widening of the area searched (area increased searching). Mean swimming speed was constant over a broad range (101–103 ind·1–1 of food density, although at extreme (high or low) values of food density it depended on swimming responses of the predator. Frequency of visits to the different parts of the aquarium strongly depended on encounters of hungry fish with food particles or patches. 相似文献
27.
In the past year, additional experimental data have expanded our understanding of the molecular mechanisms that underlie nuclear receptor control of regulatory programs. It is increasingly clear -that steroid members (e.g. glucocorticoid and estrogen) and non-steroid members (e.g. retinoic acid, thyroid hormone, and vitamin D) of the nuclear receptor superfamily may utilize distinct strategies in achieving their complex control of gene regulation. 相似文献
28.
In this work, we have calculated the optimal surface area per amphiphile molecule using a two-dimensional gas of electric dipoles interacting with hard The optimal surface area can be evaluated according to a formula (in the two-body approximation) or as a root of an equation (in the three-body approximation). If the equation has more than one positive root, which is greater than the hard core area, then a polydisperse dimensional distribution of supramolecular aggregates is possible. 相似文献
29.
Extracellular Fluid Proteins of Goldfish Brain: Evidence for the Presence of Proteases and Esterases 总被引:1,自引:1,他引:0
Preparations of enriched fractions of extracellular fluid (ECF) proteins from goldfish brain were found to contain protease(s) and esterase(s). The N-substituted furanacryloyl (FA) peptides FA-Phe-Gly-Gly and FA-Phe-OMe were used as model substrates for determining protease and esterase activity, respectively, in a spectrophotometric assay. Studies of the profile of substrate specificity and identification of the types of compounds that were effective as inhibitors showed that these ECF enzymes have some distinctive properties. GSH, but not GSSG, and EDTA inhibited the protease(s) without influencing the esterase(s), whereas L-1-tosylamide-2-phenylethylchloromethyl ketone blocked both protease and esterase activities of ECF. Most of the protease and esterase properties of ECF could be bound to concanavalin A-Sepharose affinity chromatographic columns in association with ependymin--a brain extracellular protein. These observations indicate that ECF may contain a metalloprotease(s) and raise the possibility that the ependymins might be a substrate for these ECF enzymes. 相似文献
30.
Cytokinin-induced switch in development in excised cotyledons of radiata pine cultured in vitro 总被引:2,自引:0,他引:2
Victor M. Villalobos Melvin J. Oliver Edward C. Yeung Trevor A. Thorpe 《Physiologia plantarum》1984,61(3):483-489
Cotyledons of Pinus radiata D. Don were cultured under shoot-forming (plus cytokinin) and elongating (minus cytokinin) conditions. Using. autoradiographic and precursor incorporation techniques, the sites and rate of macromolecular synthesis were examined during the first five days in culture. Active incorporation of 3 H-thymidine, 3 H-uridine and 3 H-leucine occurred. In shoot-forming cotyledons the incorporation became preferentially located in the epidermal and sub-epidermal cell layers in contact with the medium. In elongating cotyledons, in contrast, incorporation was randomly distributed, and the amount of incorporation declined with time. Biochemically, differences in DNA, RNA and total protein synthetic patterns were observed. In elongating cotyledons the rates of RNA and protein synthesis were higher during the first 48 h than in shoot-forming tissues, after which the synthetic rates were similar. Two peaks of newly formed DNA were observed in both tissues. These findings indicate that the cytokinin-induced changes in developmental pathways began within 24 h in culture. 相似文献