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101.
Norepinephrine Release in the Rat Pineal Gland: The Input from the Biological Clock Measured by In Vivo Microdialysis 总被引:2,自引:1,他引:1
W. J. Drijfhout A. G. van der Linde S. E. Kooi C. J. Grol B. H. C. Westerink 《Journal of neurochemistry》1996,66(2):748-755
Abstract: The sympathetic innervation of the rat pineal gland was investigated, measuring the norepinephrine (NE) release by on-line in vivo microdialysis. NE was assayed using an HPLC method with precolumn derivatization and fluorescence detection. Its high sensitivity and reliability made it very suitable to monitor the low levels of NE in the dialysates (12.5 fmol during nighttime, 3 fmol during daytime). To increase NE levels, the monoamine reuptake inhibitor cocaine was added to Ringer's solution at concentrations of 10−6 and 10−5 M . This resulted in increases of neurotransmitter output of 167 and 219%, respectively, but did not change the qualitative and/or quantitative outcome of other experiments. Perfusion with 10−6 M tetrodotoxin for 1 h resulted in a decrease of the NE release by >80%, whereas perfusion with the α2 -receptor antagonist yohimbine caused a twofold increase. These results indicate that the NE release in the rat pineal was of neuronal origin and regulated by a negative feedback mechanism involving inhibitory presynaptic α2 -receptors. Long-term (i.e., 16 h) measurements are described, showing the circadian properties of NE release. A pronounced rhythm is reported, showing extremely sharp transitions between low daytime and high nighttime values. Increases and decreases are reported to occur within the duration of collecting one sample (20 min). For comparison, the rhythm of melatonin release was also recorded. The on and off switches of the sympathetic input correlated well with the circadian rhythm of melatonin release and can thus be considered as the primary clock signal, inducing the nightly production of melatonin. 相似文献
102.
J W Eckblad 《Experimental parasitology》1973,33(2):331-342
Experimental studies were conducted under both laboratory and field conditions to determine the effects of prey density, three levels of prey aggregation, water depth, and predator density on the number of snails killed per larva of Sepedon fuscipennis. Of these factors, predation rates were most influenced by prey density and water depth. The number of small (2–4.5 mm) Lymnaea palustris killed per larva of S. fuscipennis increased at a decreasing rate as prey density increased under shallow water conditions. Larvae killed a mean of 14 snails at a prey density of 200/m2, while an average of 24 snails were killed per larva of S. fuscipennis at a prey density of 4000/m2. This functional response to prey density was largely confined to third-instar larvae, and as water depth was increased the response was not apparent.A field study in which larval densities of S. fuscipennis were manipulated showed that the population density of smaller individuals of L. palustris (< 4.5 mm) was reduced when predator density was increased. Populations of Physa integra, Gyraulus parvus, and larger L. palustris were not significantly reduced by the malacophagous larvae at the levels tested. 相似文献
103.
Eizi Kuno 《Population Ecology》1969,11(2):127-136
A simple method of sequential sampling is developed which would make it automatically possible to secure, without excess sampling, a predetermined level of precision for a series of population estimates being required. It appears to have wide application to sampling field populations under various situations since it is simply based upon the relationship of variance to mean for which a comprehensive formula deduced for biological populations from the linearity in the regression of mean crowding on mean density could be adopted. Some problems that may arise in practical application of the method are also discussed. 相似文献
104.
Using species traits to assess human impacts on near shore benthic ecosystems in the Canadian Arctic
Human activities have the potential to alter the diversity and composition of biological communities in natural environments, which can cause changes in ecosystem functioning. This has led to the development of environmental assessment techniques that take into account species identity, as species can contribute differently to various ecosystem processes. Biological Traits Analysis (BTA) is used to compare the abundances of specific biological traits in samples to produce information about how ecosystem functioning may change across a specific terrestrial or aquatic system. In the present study, BTA was used to assess the influence of municipal wastewater effluent on benthic marine communities in near shore soft sediments in four locations across the Canadian Arctic Territory of Nunavut, Canada. Shifts in trait composition were assessed relative to indicators of sediment enrichment (sediment chlorophyll, organic content, degree of anoxia), and natural variation in habitat characteristics (water depth, porosity, average grain size) at a site receiving wastewater and a reference site in each sampling location. The results indicated a mild enrichment effect of wastewater, as evidenced by changes in trait composition at three of the four sites that received wastewater inputs. However, the amount of variance in trait composition explained by metrics of wastewater enrichment in these locations were generally equal to or lower than the amount of variance explained by sediment characteristics related to natural processes. These results provide greater insight into the underlying causes and consequences of human activities than more traditional methods for environmental impact assessment, and can be directly applied in a management context. 相似文献
105.
Gary A. Borkan David E. Hults Peter J. Mayer 《American journal of physical anthropology》1982,25(Z3):181-202
The field of gerontology is remarkably diverse; yet there has been relatively little investigation of physical anthropological issues in aging research. This review explores gerontologic topics of actual and/or potential interest to physical anthropologists. The evolution of aging presents a theoretical dilemma in that postreproductively expressed traits may be outside the influence of natural selection. The physiological changes of aging comprise a diversified mosaic of physical deterioration as would be expected from an evolutionary model. Studies of prehistoric aging are limited to estimating lifespan, which may not be indicative of rate of aging. Considerable attention has been devoted to body composition and aging, and notable findings include a loss of lean tissue with age and relatively constant (though redistributing) fat mass. Osteoporosis is a major problem of aging in females, as is tooth loss in both sexes. The study of variation in rates of aging is only beginning, and a number of approaches to measuring biological age in adulthood are presented. Determining the associations of lifestyle, economic, and nutritional status with biological age may reveal sources of variation in rates of aging and may be of practical importance. 相似文献
106.
Leonard H. Rome Jonothan Miller 《Biochemical and biophysical research communications》1980,92(3):986-993
Treatment of the lysosomal enzyme, α-L-iduronidase, with 2,3 butanedione, an arginine modifying reagent, under conditions where enzyme activity was unaffected, reduced by 50% the internalization of the enzyme into cultured human fibroblasts. The lowered rate of internalization was a result of a reduced binding of the enzyme to cell surface receptors. The butanedione treatment of α-L-iduronidase caused a 90% reduction of binding when isolated fibroblast membranes were used as the source of receptor. This marked reduction of binding was also seen when membranes from a rat chondrosarcoma were examined. Although there is ample evidence that the receptor recognizes mannose 6-phosphate residues on the enzyme, the results suggest that other structural features, such as arginine moieties, may also be important in iduronidase binding. 相似文献
107.
In this review, structures of natural products isolated from the soft corals of genus Cladiella and their biological activities are described. 相似文献
108.
109.
《Bioorganic & medicinal chemistry letters》2020,30(7):127019
A series of novel HIV-1 protease inhibitors has been designed and synthesized, which contained morpholine derivatives as the P2 ligands and hydrophobic cyclopropyl as the P1′ ligand at the meantime in this study, with the aim of improving the interactions between the active sites of HIV-1 protease and the inhibitors. Twenty-eight compounds were synthesized and assessed, among which inhibitors m18 and m1 exhibited excellent inhibitory effect on the activity of HIV-1 protease with IC50 value of 47 nM and 53 nM, respectively. The molecular modeling of m1 revealed possible hydrogen bondings or van der Waals between the inhibitor and the protease, worthy of in-depth study. 相似文献
110.
《Mycoscience》2020,61(1):16-21
Bioactive compounds of endophytic fungus Trichoderma polyalthiae were extracted from culture broth media. The crude extracts showed strong antimicrobial activity against human pathogens. Biologically active compounds were isolated and purified by chromatographic methods. The structures of the pure compounds were elucidated by spectroscopic methods. They were identified as Violaceol I and Violaceol II. These compounds were detected as secondary metabolites produced by this genus for the first time. Violaceol I and II had a broad spectrum of antimicrobial activity against human pathogens, including Gram-positive bacteria (Staphylococcus saprophyticus, Staphylococcus aureus, Methicillin-Resistant S. aureus, Bacillus subtilis, Bacillus cereus) and Gram-negative bacteria (Salmonella typhimurium, Shigella sonnei) and Candida albicans. Violaceol I exhibited Minimal Inhibitory Concentration (MIC) values (<9.765–156.25 μg/mL) that were higher than Violaceol II (<9.765–312.5 μg/mL). Additionally, the MIC value of the phenol violaceol from this taxon was lower than the previous reports. 相似文献