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101.
102.
103.
Aspects of the life cycle of marine nematodes 总被引:1,自引:0,他引:1
Summary 1. Life cycles of approximately one month are recorded for laboratory maintained cultures of chromadorid, monhysterid and oncholaimid nematodes.2. Amphimictic and parthenogenetic reproduction occurs in the species investigated. Reproduction inMonhystera parelegantula is by parthenogenesis.3. The chromadoridChromadorina epidemos and the oncholaimidViscosia macramphida are able to reproduce by either amphimixis or parthenogenesis.4.Acanthonchus cobbi, Chromadora macrolaimoides andEuchromadora gaulica are amphimitically reproducing species.
Aspekte des Lebenszyklus mariner Nematoden
Kurzfassung Bei einigen marinen Nematoden, die in Biscayne Bay (Florida) gesammelt und im Labor gezüchtet worden sind, vollzieht sich der gesamte Lebenszyklus ungefähr innerhalb eines Monats. BeiAcanthonchus cobbi, Chromadora macrolaimoides undEuchromadora gaulica ist zweigeschlechtliche Fortpflanzung festgestellt worden.Monohystera parelegantula vermehrt sich parthenogenetisch. Ein möglicherweise durch Umwelteinflüsse bedingter Wechsel von bisexueller und parthenogenetischer Fortpflanzung tritt beiChromadora epidemos undViscosia macramphida auf.相似文献
104.
Summary 1. Studies of the broad-leafed turtle grass,Thalassia testudinum
König, have revealed a diverse range of fungal infestation different in generic composition and dynamics of attack from that found on submerged wood. Certain of the fungi, notably the AscomyceteLindra thalassiae, initiate considerable degradation of leaf tissue and show a developmental cycle in nature related to the physiological state of the host plant.2. Use of fungal-cellulose mats as a trapping substrate has been extremely effective for discernment of ecologically significant shifts in nematode concentrations, especially those of the omnivorous species,Metoncholaimus scissus.3. Patterns of activity ofM. scissus, as well as those of various foliicolous nematodes, suggest that loci of organic material, such as fungal infested leaves and decaying plant tissue, significantly affect biological activity of these animals.4. Laboratory analysis of degraded cotton cellulose filters show a striking incidence of fungal reproduction of the ascomycetous fungusLulworthia, along with development of a considerable associated nematode fauna, especially species ofViscosia (V. macramphida) andLeptolaimus (L. plectoides). Successional patterns in nematode development are noted with continued degradation of the cotton cellulose matrix.
Contribution No. 768 from the Institute of Marine Science, University of Miami, Miami, Florida, and from the Canada Department of Agriculture, Ottawa, Canada. This work was supported at the IMS by grant GM 12842 from the National Institutes of Health, USA. 相似文献
Studien über marine Pilz-Nematoden-Assoziationen und Pflanzendegradation
Kurzfassung Untersuchungen am SeegrasThalassia testudinum König haben ergeben, daß sich hier Pilzinfektionen hinsichtlich der Komposition der beteiligten Gattungen und der Dynamik des Befalls von den am untergetauchten Holz festgestellten Infektionen unterscheiden. Bestimmte Pilze, insbesondere der AscomycetLindra thalassiae, leiten eine erhebliche Degradation des Blattgewebes ein und zeigen einen Entwicklungszyklus, welcher in Beziehung steht zum physiologischen Zustand der Wirtspflanze. Die Anwendung von Pilz-Zellulose-Matten als Einfangsubstrat war außerordentlich erfolgreich für das Erkennen ökologisch signifikanter Verschiebungen in den Nematodenkonzentrationen, insbesondere bei der omnivoren ArtMetoncholaimus scissus. Die Aktivitätsmuster vonM. scissus — ebenso wie die verschiedener foliicolöser Nematoden — deuten darauf hin, daß pilzinfizierte und zerfallende Pflanzenteile in entscheidendem Maße die biologische Aktivität dieser Tiere beeinflussen. Laboratoriumsanalysen degradierter Wollzellulosefilter lassen eine überraschend starke Vermehrung des AscomycetenLulworthia erkennen und gleichzeitig die Entwicklung einer beachtlichen Fauna assoziierter Nematodenarten, insbesondere vonViscosia macramphida undLeptolaimus plectoides. Im Verlaufe der weiteren Degradation der Wollzellulosematrix kommt es bei der Nematodenfauna zu entsprechenden Sukzessionen.
Contribution No. 768 from the Institute of Marine Science, University of Miami, Miami, Florida, and from the Canada Department of Agriculture, Ottawa, Canada. This work was supported at the IMS by grant GM 12842 from the National Institutes of Health, USA. 相似文献
105.
Jila H. Boal Scott F. Deamond Daniel E. Callahan Sarah A. Bruce Paul O. P. Ts'o L. L. Kan 《Cell biochemistry and biophysics》1989,14(3):245-256
The nuclear magnetic resonance (NMR) parameters, spin-lattice (T1), and spin-spin (T2) relaxation time, are usually longer for neoplastic cells than for normal cells of the same cell type. This has generally
been true at low NMR frequencies (≤100 MHz) when comparisons have been made between normal and neoplastic cells that have
both spent a short time in culture. We have previously demonstrated that although the T1 values of paired normal and neoplastic Syrian hamster (SH) fibroblastic cells in culture are not significantly different
when measured at 300 MHz, the 300 MHz T2 values for the neoplastic cells are smaller than those of the normal cells. (Xin et al. (1986),Cell Biophysics
8, 213.) Since treatment of normal diploid cells with polypeptide growth factors or tumor promoters frequently results in reversible
expression of neoplasia-associated phenotypes, T1 and T2 were obtained at 300 MHz for treated and untreated SH cells to see if these compounds could also produce smaller 300 MHz
T2 values. Secondary culture SH fetal fibroblast cells were treated with epidermal growth factor (EGF), fibroblast growth factor
(FGF), phorbol-12,13-didecanoate (PDD) and 4-α-phorbol-12,13-didecanoate (4αPDD). Treatment with either growth factor resulted
in smaller T2 values, but a statistically significant decrease was not observed for PDD or 4αPDD. The observed reductions in T2 values were correlated with the morphological and growth-stimulatory effects of these compounds on the cells. 相似文献
106.
James C. Beck Howard L. Hosick Bruce A. Watkins 《In vitro cellular & developmental biology. Plant》1989,25(5):409-418
Summary We investigated the effects of conditioned media derived from mouse mammary fat pads on the proliferation of CL-S1 cells,
an epithelial cell line originally isolated from a preneoplastic mammary outgrowth line. Cell proliferation in vitro in serum-free
defined medium was compared to that in this medium conditioned using intact mammary fat pad pieces or isolated fat pad adipocytes.
Culture medium was conditioned by incubating the conditioning material in defined culture medium for 24 h at 37°C. Conditioned
medium induced CL-S1 proliferation as much as 10- to 20-fold above the minimal levels of growth in control cultures after
13 d of culture. The growth-stimulatory factor(s) had an apparent molecular weight of greater than 10 kDa. This growth-stimulatory
activity was both heat and trypsin stable. Because the role of adipose tissue is to store and release lipids, we next tested
whether lipids are released during medium conditioning. The lipid composition of the fat pad conditioned medium was characterized
using both thin layer and gas liquid chromatography. These lipid analyses indicated that the fat pad pieces released significant
amounts of fatty acids and phospholipids into the medium during the conditioning period. The free fatty acid composition included
both saturated and unsaturated molecules, and about 80% of the total fatty acids consisted of palmitate, stearate, oleate,
and linoleate. These same fatty acids were a structural component of the majority of phospholipid found in the medium. The
addition of palmitate or stearate to defined medium had no effect or was inhibitory for CL-S1 proliferation, depending on
the concentration used. Defined medium supplemented with oleate, arachidonate, or linoleate induced CL-S1 proliferation, and
the inhibitory effects of palmitate and stearate were overcome by addition of oleate and linoleate. These data indicate that
both unsaturated and saturated fatty acids are released from intact adipose cells of the mouse mammary fat pad and that fatty
acids can influence the growth of prenoplastic mouse mammary epithelium. Thus, unsaturated fatty acids, perhaps in conjunction
with other substances released simultaneously, are candidate molecules for the substances that mediate the effect of adipose
tissue on growth of epithelium.
This work was supported in part by a grant from the American Institute for Cancer Research; grant CA 46885 from the National
Institutes of Health, Bethesda, MD; and by State of Washington initiative 171. 相似文献
107.
Sadis Matalon Joseph S. Beckman Michael E. Duffey Bruce A. Freeman 《Free radical biology & medicine》1989,6(6):557-564
The purpose of this study was to quantify the effects of extracellularly generated partially reduced oxygen species on active sodium (NA+) transport across the ventral toad skin, a well-studied epithelium. Sections of skin from decapitated toads were mounted in an Ussing chamber, bathed on both sides with electrolyte solution containing 500 μM xanthine and bubbled continuously with room air. The tissues were short-circuited, and short circuit current (Isc) and tissue resistance (Rt were monitored continuously with an automatic voltage clamp apparatus. Fifteen mU/ml of xanthine oxidase (XO), either purchased from Calbiochem or purified from cream, were instilled in either the apical (mucosal) or basolateral (serosal) baths at t = 0 and T = 10 min. Hydrogen peroxide (H2O2) concentrations increased to 200 μM within the first 20 min and then decreased, reaching a value of 40 μM by 60 min. Mean [H2O2] was 90 μM. Instillation of XO in the apical bath resulted in a large decrease in Isc and an increase in Rt, their values being 43% and 160% of their corresponding controls 85 min after the first instillation. Addition of superoxide dismutase and catalase completely prevented these changes. Instillation of XO in the basolateral bath had no effect. Similar physiological responses were obtained using the Calbiochem XO or the purified XO, which contained no measurable protease activity. It was concluded that extracellularly generated partially reduced oxygen species may interfere with active Na+ transport by possibly damaging apical Na+ channel proteins. 相似文献
108.
109.
Summary Two different3H-saxitoxin-binding proteins, with distinct biochemical and functional properties, were isolated from rat brain using a combination of anion exchange and lectin affinity chromatography as well as high resolution size exclusion and anion exchange HPLC. The alpha subunits of the binding proteins had different apparent molecular weights on SDS-PAGE (Type A: 235,000; Type B: 260,000). When reconstituted into planar lipid bilayers, the two saxitoxin-binding proteins formed sodium channels with different apparent single-channel conductances in the presence of batrachotoxin (Type A: 22 pS; Type B: 12 pS) and veratridine (Type A: 9 pS; Type B: 5 pS). The subtypes were further distinguished by scorpion (Leiurus quinquestriatus) venom which had different effects on single-channel conductance and gating of veratridine-activated Type A and Type B channels. Scorpion venom caused a 19% increase in single-channel conductance of Type A channels and a 35-mV hyperpolarizing shift in activation. Scropion venom double the single-channel conductance of Type B channels and shifted activation by at least 85 mV. 相似文献
110.
Summary Isolated nerve cells fromLymnaea stagnalis were studied using the internal-perfusion and patch-clamp techniques. Patch excision frequently activated a voltage-independent Ba2+-permeable channel with a slope conductance of 27 pS at negative potentials (50mm Ba2+). This channel is not seen in patches on healthy cells and, unlike the voltage-dependent Ca channel, is not labile in isolated patches. The activity of the channel in inside-out patches is unaffected by intracellular ATP, Ca2+ below 1mm or the catalytic subunit of cAMP-dependent protein kinase but is reversibly blocked by millimolar intracellular Ca2+ or Ba2+. The channel can be activated in on-cell patches by either internal perfusion with high Ca2+ or the long-term internal perfusion of low Ca2+ solutions not containing ATP. These channels may carry the inward Ca2+ current which causes a regenerative increase in intracellular Ca+ when snail neurons are perfused with high Ca2+ solutions. High internal Ca2+, or long periods of internal perfusion with ATP-free solutions, induces an increase in a resting (–50 mV) whole-cell Ba2+ conductance. This conductance can be turned off by returning the intracellular perfusate to a low Ca2+ solution containing ATP and Mg2+. The activity of this channel appears to have an opposite dependence on intracellular conditions to that of the voltage-dependent Ca channel. 相似文献