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71.
72.
Sinlan Poo Ana Karen Candia Kristina L. Cohen Francesca T. Erickson Sara A. Mason Bradley D. Nissen Adair F. McNear Jonathon J. Reinig Joseph S. Sherrock Ashley R. Aguiluz Letitia L. Jacques Hanna E. R. Jenkins Anne Devan-Song 《Biotropica》2023,55(4):806-815
Environmentally cued hatching has been well-documented in amphibians in response to a wide range of abiotic and biotic factors. The hatching of terrestrial amphibian eggs in response to flooding may be basal within the group, but amphibian lineages in tropical Asia and sub-Saharan Africa have not received as much attention as their Neotropical counterparts. We investigated submergence-induced hatching in Feihyla hansenae, a Rhacophorid tree frog with terrestrial eggs. We quantified natural rates of clutch submergence at our study site in Thailand. Using submergence experiments, we found that embryos are capable of hatching early to escape flooding, and that failure to hatch results in mortality. Among the embryos that were able to hatch early, only the earliest, youngest hatchlings experienced a trade-off in body size that persisted for 6 days, while later, older hatchlings were not significantly smaller than spontaneous hatchlings under control conditions. By incorporating our natural and experimental data into Monte Carlo methods to simulate and compare survival probabilities with and without hatching plasticity, we found an overall 3.1% increase in submergence survival due to hatching plasticity. Our findings support the idea that flooding-induced hatching is widespread across amphibians with terrestrial eggs and highlight the importance of researching understudied tropical regions. As climate change is projected to affect rainfall patterns, the ability of embryos to escape abiotic egg-stage threats may be an indicator of species' ability to flexibly navigate a changing environment. 相似文献
73.
74.
Richard M. Klein Timothy D. Perkins Jeffrey Tricou Adrian Oates Karen Cutler 《American journal of botany》1991,78(9):1191-1198
Scarcity of red spruce (Picea rubens Sarg.) seedlings in declining spruce-fir forests of Camels Hump mountain, Vermont, prompted a study on some contributing factors involved in failure of spruce regeneration. Cones were shorter than those from low elevation red spruce trees from unaffected sites. Seed number in cones collected in declining areas of Camels Hump was low as were seed sizes and weights. Seed germination was at control levels only in good seed years. Capacity of seeds to form seedlings was reduced relative to that of controls, although seedling growth was normal. Coniferous litter contains presumed allelopathic substances leachable by contemporary precipitations that affect seed germination and seedling root development in red spruce, but not in balsam fir. Shield fern contains leachable substances that reduce seed germination and seedling root development in red spruce, but not balsam fir. Roots of red spruce germlings have lower capacity to penetrate through the increased forest duff depths of declining forests than do balsam fir roots. It is anticipated that substantial reproduction of red spruce will not occur in declining montane conifer forests under present conditions. 相似文献
75.
This study shows that mitochondria in liver, kidney, heart, and brain of the mouse have a distinct mitochondrial density. It also demonstrates that the mtDNA copy number per mitochondrion is organ-specific. A reliable method of determining mitochondrial density per organ is by stereological analysis of tissue sections while mtDNA quantitation is by the use of radiolabelled mtDNA probe. This is the first study in which a comprehensive examination of mitochondrial density and quantitation of mitochondrial genomes in mouse organs have been done. In summary the variability is not only in mitochondrial density but also in genomic copy number in mitochondria of various tissues. 相似文献
76.
Ermias Admasu Simon J. Thirgood Afework Bekele M. Karen Laurenson 《African Journal of Ecology》2004,42(2):144-152
The spatial ecology of golden jackal Canis aureus was studied on farmland adjacent to the Bale Mountains National Park in southern Ethiopia during 1998–2000. Three adult and four subadult jackals were captured in leg‐hold traps and radiotagged. The range size of the adult jackals varied from 7.9 to 48.2 km2 and the subadults from 24.2 to 64.8 km2 . These ranges are the largest recorded for this species. Range overlap of the tagged jackals averaged 54%, which, in conjunction with observations of associations between individuals, suggested that all the tagged jackals belonged to one social group. Tagged jackals were observed alone on 87% of occasions despite the extensive overlap in individual ranges. Pairs consisting of a male and female were the most commonly observed group and larger groups were seen on only five occasions. Jackals in this population appeared less gregarious than observed elsewhere. The jackals used all the habitats available to them, particularly at night when they foraged in Artemesia and Hypericum bush and farmland. During the day they were more frequently found in Hagenia and Juniper woodland and their diurnal resting sites were characterized by thick cover. This is the first detailed study of golden jackals in a human‐modified landscape in Africa and further demonstrates the flexibility in behaviour and ecology exhibited by this species throughout its range. 相似文献
77.
78.
Balzer Sandrock Karen M. Hudson Douglas E. Williams Michael A. Lieberman 《In vitro cellular & developmental biology. Animal》1996,32(4):225-233
Summary The regulation of megakaryopoeisis by cytokines is not yet well understood. It is possible that autocrine loops are established
during megakaryocyte growth and differentiation, aiding in the maturation of these cells. The CHRF-288-11 human megakaryoblastic
cell line has been examined for cytokine production in growing cells and cells stimulated to differentiate by the addition
of phorbol esters. It has been demonstrated that these cells produce RNA corresponding to the interleukins IL-1α, 1β, 3, 7,
8, and 11, granulocyte-macrophage colony stimulating factor (GM-CSF), stem cell factor (SCF), transforming growth factor-β
(TGF-β), tumor necrosis factor-α (TNF-α), interferon-α (INF-α), and basic fibroblast growth factor (bFGF). Additionaly, RNA
corresponding to the receptors for IL-6, GM-CSF, SCF, INF-α,β, bFGF, and monocyte colony stimulating factor (M-CSF) were also
expressed by the cells. The receptor for TNF-α was detected immunologically. Analysis at the protein level demonstrated that
significant amounts of INF-α, TNF-α, GM-CSF, SCF, IL-1α, and a soluble form of the IL-6 receptor were produced by the cells.
Addition of phorbol esters to CHRF-288-11 cells enhances their megakaryocytic phenotype; such treatment also results in increased
secretion of INF-α, TNF-α, and GM-CSF. These results suggest that potential autocrine loops are established during the differentiation
of CHRF-288-11 cells, which may alter the capability of the cell to differentiate. These findings are similar to those recently
obtained for marrow-derived megakaryocytes (Jiang et al.) suggesting that CHRF-288-11 cells provide a useful model system
for the study of cytokine release during megakaryocyte differentiation. 相似文献
79.
Juli O'Connor Dean F. Revell Karen E. Masters Ian F. Connerton Ian G. Sumner 《Protein expression and purification》1996,7(4):377-383
The gene encoding the 67-kDa cocoa storage protein precursor has been cloned fromTheobroma cacaoand expressed inEscherichia coliusing the pET expression system. The recombinant storage protein has been renatured from inclusion bodies at 30°C using 20 m
glycine–NaOH buffer, pH 10.0, containing 1 m
oxidized glutathione and 0.1% Brij. The renatured protein was purified and demonstrated to adopt a stable native conformation by optical spectroscopy. Secondary structure analysis from circular dichroism indicated the protein to be 23% α-helix and 38% β-sheet, in close agreement with values obtained using a secondary structure prediction program. 相似文献
80.
Atelocauda koae, a rust of the native HawaiianAcacia koa, is considered as a demicyclic species, having spermogonial, aecial, and telial states, but is unusual in production of aeciospores
simultaneously with teliospores rather than consecutively. Host inoculation with spores of each state separately confirmed
that the life cycle was perpetuated by the telial state, but the aeciospores, while capable of germination and stomal penetration,
did not produce detectable infection. This rust therefore behaves as a microcyclic species, and appears to be in evolutionary
transition toward this reduced state. Teliospores produced vestigial, permanently attached basidiosopores which germinated
to produce infective hyphae. The hyphae entered the host either through stomata or penetrated the epidermis directly, with
the latter method being more common. Unusual nuclear associated with teliospore germination, in which meiosis occurs in more
than one diploid nucleus was observed, in confirmation of an earlier study. 相似文献