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91.
The assimilation of H14CN by a variety of fungi 总被引:1,自引:0,他引:1
92.
93.
Studies with cyanidium caldarium,an anomalously pigmented chlorophyte 总被引:12,自引:0,他引:12
Mary Belle Allen 《Archives of microbiology》1959,32(3):270-277
Summary
Cyanidium caldarium, an alga found in acid hot springs troughout the world, has a morphology and developmental history resembling those of Chlorella, but contains C-phycocyanin and no chlorophyll other than chlorophyll a. The reasons for considering it to be a member of the Chlorophyta are reviewed.
Cyanidium is also remarkable for its thermal and acid tolerance. It grows readily in the dark on sugar media. However, light is required for the formation of chlorophyll and phycocyanin except in occasional variant cells which can form limited amounts of these pigments in the dark. Light-grown Cyanidium carries out normal green plant photosynthesis but resembles the red and some of the blue-green algae in that chlorophyll-absorbed light is used with lower efficiency than that absorbed by phycocyanin.The possible significance of the unusual pigmentation of Cyanidium is discussed.Contribution no.23 from the Laboratory of Comparative Physiology and Morphology of The Kaiser Foundation. 相似文献
94.
Human arterial smooth muscle cells in culture: Inverse relationship between proliferation and expression of contractile proteins 总被引:5,自引:0,他引:5
Gunnar Fager Göran K. Hansson Allen M. Gown David M. Larson Omar Skalli Göran Bondjers 《In vitro cellular & developmental biology. Plant》1989,25(6):511-520
Summary Human arterial smooth muscle cells (hASMC) from explants of the inner media of uterine arteries were studied in secondary
culture. We had previously found that these cells depend on exogenous platelet-derived growth factor (PDGF) for proliferation
in vitro. Deprivation of the serum mitogen(s) by culture in plasma-derived serum or bovine serum albumin (BSA) caused a true
growth arrest that was reversible upon reexposure to the mitogen(s). When added to serum-containing medium, heparin caused
a reversible growth arrest which could be competed for by increasing concentrations of serum. In the current study we used
a set of smooth muscle-specific actin and myosin, antibodies to study the expression of contractile proteins in stress fibers
under indirect immunofluorescence on hASMC in culture. Even in sparse culture, grwoth-arrested hASMC expressed stress fibers
containing these actin and myosin epitopes. This was true irrespective of whether growth arrest was achieved by culture in
media containing only BSA or a combination of heparin and whole blood serum. hASMC proliferating in whole blood serum in sparse
culture did not express such strees fibers, as judged by immunofluorescent staining. This was true also for cells that were
restimulated to proliferate in serum after a growth arrest. Utilizing a monoclonal antibody against a nuclear antigen expressed
in proliferating human cells, we were able to demonstrate an inverse relationship between the expression of this antigen and
the SMC-specific contractile proteins, respectively. Under these culture conditions, the reversible transition between defifferentiated
and differentiated hASMC was almost complete and terminated about 1 wk after the change in culture condition. We conclude
that hASMC in vitro respond, to exogenous PDGF by proliferation and dedifferetiation as a single population of cells. We also
conclude that this modulation is reversible, because the cells become uniformly quiescent and differentiated when the mitogenic
stimulus is blocked or removed.
This study was supported by grants from the Swedish Medical Research Council (Project no. 4531 and 6816), the Swedish Association
against Heart and Chest Diseases, the King Gustaf V and Queen Victoria Foundation, the National Institutes of Health, Bethesda,
MD (grant HL 29873) and the Swedish National Board for Laboratory Animals. 相似文献
95.
96.
S R Tamat D E Moore B J Allen 《Pigment cell research / sponsored by the European Society for Pigment Cell Research and the International Pigment Cell Society》1989,2(4):281-285
The application of inductively coupled plasma atomic emission spectrometry (ICP-AES) to the determination of the concentration of complex boron-containing compounds in biological tissue samples is described. Tissue digestion is achieved with perchloric acid and hydrogen peroxide in 1 hr at 75 degrees C. The ICP-AES method gave a linear response for elemental boron concentration in the range 0.05 to 100 ppm and does not require the reduction of the boron to a simple species, such as boric acid. Complete recovery of boron in complex boron cluster compounds was obtained. The procedure has been applied to the determination of the boron content in compounds synthesised for neutron capture therapy and is suitable for use in biodistribution studies of such compounds. 相似文献
97.
98.
99.
The specific activity of 2,3-dehydrodolichyl diphosphate synthase in homogenates of protease-treated seminiferous tubules, enriched spermatogenic cells, and Sertoli cells changed as a function of the age of prepuberal rats. The highest enzymatic activity occurred in each case in 23-day-old rats. Homogenates of pachytene spermatocytes, spermatids, or Sertoli cells had higher synthase activity than a whole testicular homogenate prepared by protease treatment of tubules. Enzymatic activity in pachytene spermatocytes expressed per mg of protein was about 1.7-fold higher than in spermatids, 5.3-fold higher than in spermatogonia, and about 8.3-fold higher than in spermatozoa. Therefore, the increase in spermatogenic cell synthase before day 23 can be accounted for by the appearance of the pachytene spermatocytes. Enzymatic activity decreased remarkably after the differentiation of spermatids into spermatozoa. Synthase activity in enriched Sertoli cell preparations was 1.5-2.3-fold higher than in spermatogenic cell preparations between days 15 and 30. Therefore, both spermatogenic cells and Sertoli cells contribute to changes in the enzymatic activity in seminiferous tubules during development. These changes may be important in regulating the availability of dolichyl phosphate for glycoprotein synthesis during early stages of differentiation. 相似文献
100.
R E Allen L L Rankin 《Proceedings of the Society for Experimental Biology and Medicine. Society for Experimental Biology and Medicine (New York, N.Y.)》1990,194(2):81-86
Satellite cells are myogenic cells attributed with the role of postnatal growth and regeneration in skeletal muscle. Following proliferation and subsequent differentiation, these cells will fuse with one another or with the adjacent muscle fiber, thereby increasing myonuclei numbers for fiber growth and repair. The potential factors which could regulate this process are many, including exercise, trauma, passive stretch, innervation, and soluble growth factors. Three classes of growth factors in particular (fibroblast growth factor, insulin-like growth factor, and transforming growth factor-beta) have been studied extensively with respect to their effects on satellite cell proliferation and differentiation in culture. Fibroblast growth factor has been shown to stimulate proliferation but depress differentiation. Insulin-like growth factor stimulates both proliferation and differentiation, although the latter to a much greater degree. Transforming growth factor-beta slightly depresses proliferation but inhibits differentiation. When administered in combination, these factors can induce satellite cell activities in culture which mimic those typical of satellite cells found in vivo in growing, regenerating, or healthy mature muscle. Alterations in the concentrations of these growth factors in the muscle environment as well as alterations in the cell's sensitivity or responsiveness to these factors represent potential mechanisms for regulating satellite cell activity in situ. 相似文献