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61.
Chiou TT Bonhomme B Jin H Miralles CP Xiao H Fu Z Harvey RJ Harvey K Vicini S De Blas AL 《The Journal of biological chemistry》2011,286(25):22456-22468
Collybistin promotes submembrane clustering of gephyrin and is essential for the postsynaptic localization of gephyrin and γ-aminobutyric acid type A (GABA(A)) receptors at GABAergic synapses in hippocampus and amygdala. Four collybistin isoforms are expressed in brain neurons; CB2 and CB3 differ in the C terminus and occur with and without the Src homology 3 (SH3) domain. We have found that in transfected hippocampal neurons, all collybistin isoforms (CB2(SH3+), CB2(SH3-), CB3(SH3+), and CB3(SH3-)) target to and concentrate at GABAergic postsynapses. Moreover, in non-transfected neurons, collybistin concentrates at GABAergic synapses. Hippocampal neurons co-transfected with CB2(SH3-) and gephyrin developed very large postsynaptic gephyrin and GABA(A) receptor clusters (superclusters). This effect was accompanied by a significant increase in the amplitude of miniature inhibitory postsynaptic currents. Co-transfection with CB2(SH3+) and gephyrin induced the formation of many (supernumerary) non-synaptic clusters. Transfection with gephyrin alone did not affect cluster number or size, but gephyrin potentiated the clustering effect of CB2(SH3-) or CB2(SH3+). Co-transfection with CB2(SH3-) or CB2(SH3+) and gephyrin did not affect the density of presynaptic GABAergic terminals contacting the transfected cells, indicating that collybistin is not synaptogenic. Nevertheless, the synaptic superclusters induced by CB2(SH3-) and gephyrin were accompanied by enlarged presynaptic GABAergic terminals. The enhanced clustering of gephyrin and GABA(A) receptors induced by collybistin isoforms was not accompanied by enhanced clustering of neuroligin 2. Moreover, during the development of GABAergic synapses, the clustering of gephyrin and GABA(A) receptors preceded the clustering of neuroligin 2. We propose a model in which the SH3- isoforms play a major role in the postsynaptic accumulation of GABA(A) receptors and in GABAergic synaptic strength. 相似文献
62.
63.
Frense D 《Applied microbiology and biotechnology》2007,73(6):1233-1240
Taxol is a valuable plant-derived drug showing activity against various cancer types. Worldwide efforts had been made to overcome
the supply problem, because the supply by isolation from the bark of the slow-growing yew trees is limited. Plant cell cultures
as well as chemical and biotechnological semisynthesis are processes, which are intensively investigated for the production
of taxanes paclitaxel (Taxol) and docetaxel (Taxotere) in the last few years. This article provides a comparison of the current
research on taxane biosynthesis and production in yew cell cultures. 相似文献
64.
Kristiansen Kell Ørnstrup Holger Brandt Kirsten 《Plant Cell, Tissue and Organ Culture》1999,56(3):145-153
The objective was to reduce in vitro production costs while retaining or improving plant quality, in particular the suitability
for pot plant production. Plants were grown at photosynthetic photon flux densities (PPFD) of 0–40 μmol m-2 s-1 and sucrose concentrations of 3–7% during the multiplication phase and the effects of sucrose, BA, and NAA during root formation
were investigated. Ex vitro growth were tested in both experiments. A small reduction in the rhizome multiplication rate was
found with increasing PPFD and sucrose concentration. Increasing sucrose concentration reduced the number of aerial shoots.
Aerial shoots were etiolated when cultured in darkness and their number increased with increasing PPFD at 3% sucrose, whereas
PPFD did not affect the number of aerial shoots at 5 or 7% sucrose. During the multiplication phase a synergistic promoting
effect of PPFD and sucrose was observed on root formation. Root formation after transfer to rooting medium was affected by
sucrose and PPFD during the multiplication phase. PPFD did not influence root formation after propagation on 7% sucrose, whereas
on 3 or 5 % sucrose root formation was gradually inhibited when PPFD was decreased below 17 μmol m-2 s-1. The formation of thick roots was promoted by propagation in light, and not influenced by sucrose concentration. Ex vitro
growth was not affected by in vitro conditions, except for 7% sucrose during the multiplication phase that reduced flowering.
Root formation on rooting medium was reduced by BA and promoted both by NAA and high levels of sucrose. The root inhibiting
effect of BA could not completely be overcome by simultaneous application of NAA and high sucrose concentrations. Thick roots
were only produced in the presence of NAA, and not affected by sucrose treatment. Ex vitro flowering was negatively influenced
by the presence of BA during root formation and by high levels of sucrose if BA was absent in the rooting medium. High sucrose
levels and NAA could partially compensate for the negative effect of BA on flowering.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
65.
Precise information about endangered species, in particular identifying their resources requirements, is needed to identify
areas that might support populations. Little is known about the endangered Mount Hermon June Beetle (Polyphylla barbata) found only within Zayante soils region of Santa Cruz County, California. We investigated the beetle’s host plant selection,
habitat association and mating behavior between June 2004 and September 2005. We identified angiosperm and Pteridophyta phyla,
and fungi within the frass pellets of Mount Hermon June Beetle larvae demonstrating that they are not specialist feeders but
are microhabitat specialists. Larval species was confirmed by DNA analysis. Significant differences were found in vegetation
assemblages between regions where the Mount Hermon June Beetle did and did not occur for Chorizanthe pungens var. hartwegiana, and bare ground. 相似文献
66.
67.
Swarup R Kramer EM Perry P Knox K Leyser HM Haseloff J Beemster GT Bhalerao R Bennett MJ 《Nature cell biology》2005,7(11):1057-1065
Re-orientation of Arabidopsis seedlings induces a rapid, asymmetric release of the growth regulator auxin from gravity-sensing columella cells at the root apex. The resulting lateral auxin gradient is hypothesized to drive differential cell expansion in elongation-zone tissues. We mapped those root tissues that function to transport or respond to auxin during a gravitropic response. Targeted expression of the auxin influx facilitator AUX1 demonstrated that root gravitropism requires auxin to be transported via the lateral root cap to all elongating epidermal cells. A three-dimensional model of the root elongation zone predicted that AUX1 causes the majority of auxin to accumulate in the epidermis. Selectively disrupting the auxin responsiveness of expanding epidermal cells by expressing a mutant form of the AUX/IAA17 protein, axr3-1, abolished root gravitropism. We conclude that gravitropic curvature in Arabidopsis roots is primarily driven by the differential expansion of epidermal cells in response to an influx-carrier-dependent auxin gradient. 相似文献
68.
Kirsten M. Madsen C. William Applegate Dr. C. Craig Tisher 《Cell and tissue research》1982,226(2):363-374
Summary Morphological examination of kidney biopsies from patients with glomerulonephritis and hematuria has revealed the presence of erythrocytes within epithelial cells of the proximal tubule. This observation suggested that the proximal tubule might be capable of phagocytizing morphologically intact erythrocytes. To examine this possibility small quantities of heparinized autologous blood were injected into surface convolutions of proximal tubules of the rat kidney using standard micropuncture techniques. At time intervals ranging from 10 min to 120 h after injection, the kidneys were preserved for light and transmission electron microscopy by drip-fixation with a half-strength Karnovsky's glutaraldehyde-formaldehyde fixative.During the initial 6 h there was a flattening of the brush border and accumulation of electron-dense material representing hemoglobin in apical vacuoles and in lysosome-like structures. From 6 to 15 h after micropuncture, there was progressive loss of the brush border and the simultaneous formation of pseudopodia-like evaginations that extended from the apical plasma membrane and surrounded the individual erythrocytes. By 18 and 24 h, erythrocytes were observed in the proximal tubule cells. At later time intervals, edema, lymphocytic infiltration, and fibrosis were observed in the interstitium. In addition, crystalline structures were present in the lumen and the cells of both proximal and distal tubules. These findings suggest that in addition to their well-established ability to pinocytize hemoglobin and other proteins, the cells of the proximal tubule are capable of phagocytizing morphologically intact autologous erythrocytes. It is possible that phagocytosis by the proximal tubule cells may play a role in the disposal of erythrocytes from the tubular fluid in hematuric conditions. 相似文献
69.
Søren O. Petersen Anne Lise Nielsen Kirsten Haarder Kaj Henriksen 《Microbial ecology》1992,23(3):239-255
Nitrification and denitrification were studied in a millimeterscale microenvironment using a two-phase system with a liquid manure-saturated layer. Samples consisted of liquid cattle manure and air-dried soil stabilized with silica gel, placed between two aerobic soil phases with a water content near field capacity. A high potential for NH4
+ oxidation developed within 0–2 mm distance from the interface, and NH4
+ diffused only 10–20 mm into the soil. Some NH4
+ was probably immobilized by microorganisms in the soil between 0 and 4 days, after which nitrification was the only sink for NH4
+. A potential for denitrification developed within the manure-saturated zone. Maximum rates of both potential and actual denitrification were recorded by Day 4, but denitrification continued for at least 2–3 weeks. The potential for nitrification peaked after 14 days. When the pH of the manure was adjusted to 5.5, nitrification was reduced close to the interface, and NH4
+ penetrated further into the soil before it was oxidized. The pH adjustment had an inhibitory effect on denitrification: Both potential and actual rates of denitrification were almost eliminated for several days. The size of the manure-saturated layer strongly affected denitrification losses. With layers of 8 and 16 mm thickness, losses equivalent to 33 and 40% of the original NH4
+ pool, respectively, were estimated. When manure corresponding to a 12 mm layer was homogeneously mixed with the soil, only 0.3% was lost.Offprint requests to: S. O. Petersen. 相似文献
70.
I Ottestad S Hassani GI Borge A Kohler G Vogt T Hyötyläinen M Orešič KW Brønner KB Holven SM Ulven MC Myhrstad 《PloS one》2012,7(8):e42550