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41.
L.Charles Dickinson James C.W. Chien 《Biochemical and biophysical research communications》1973,51(3):587-592
Single crystals of horse CoHb were obtained by reduction of CoHb+ crystals with dithionite. Epr measurements showed that the g? and Coà tensors are both axial and share the same principal axis systems. Of the four subunits, the “heme” normals of C? and d? subunits ãb?plane 29 ± 1° from b?; they have the same orientation as the hemes in methemoglobin. The normals of “hemes” à and B? are 47 above the ãb? plane as compared to 16° in methemoglobin. 相似文献
42.
Developmental Expression of Go in Neuronal Cultures from Rat Mesencephalon and Hypothalamus 总被引:1,自引:1,他引:0
The developmental expression of the alpha-subunit of Go was examined in neuronal cultures derived from rat mesencephalon (MES) and hypothalamus (HYP). These cultures were essentially free of contaminating glia and were maintained as a stable population for periods up to 3 weeks. Immunoblotting utilizing specific antisera against Go indicated that in neurons from both brain regions, membrane concentrations of Go increased dramatically during the first 2 weeks in vitro. Thereafter, increases in the amount of Go per neuron kept pace with increasing process (axons and dendrites) formation. Multiple forms of immunoreactive Go were detected in MES and HYP neurons, and the proportions of these forms changed between 4 and 14 days in culture. Finally, increasing neuron density significantly increased membrane levels of Go in MES but not HYP cultures. 相似文献
43.
Autoradiographic Localization of Angiotensin II Receptor Binding Sites on Noradrenergic Neurons of the Locus Coeruleus of the Rat 总被引:2,自引:2,他引:0
The locus coeruleus (LC) of the rat was lesioned by microinjection of selective neurotoxins into the brainstem. 6-Hydroxydopamine (6-OHDA), 3 micrograms/microliter, given unilaterally at two sites 0.6 mm apart on the rostro-caudal axis of the LC, was used to lesion catecholamine-containing neuronal elements. Ibotenic acid, 2.5 micrograms/0.5 microliters, administered similarly was used to lesion nerve cell bodies. Two weeks after administration of the neurotoxin, lesion efficacy was determined based on the norepinephrine content of the cerebral cortex ipsi- and contralateral to the lesion. 6-OHDA lesions of the LC caused a 46% reduction in ipsilateral cortical norepinephrine and a 60% reduction in specific 125I-[Sar1, Ile8]-angiotensin II (125I-SIAII) binding in the LC. Ibotenic acid lesions of the LC caused a 73% reduction in ipsilateral cortical norepinephrine and a 81% reduction in specific 125I-SIAII binding in the LC. These results indicate that AII receptor binding sites in the LC are localized on noradrenergic nerve cell bodies or their dendritic and axonal ramifications within the LC. 相似文献
44.
We used whole-cell patch-clamp recording techniques to investigate G protein-activated currents in cultured rat retinal pigment
epithelial (RPE) cells. Using 140 mm KCl intracellular and 130 mm NaCl extracellular solutions, rat RPE cells possessed both inward and outward K+ currents. Upon addition of the nonhydrolyzable guanine triphosphate analogue, guanosine-5′-O-(3-thiophosphate) (GTPγS, 0.1
mm), to the recording electrode, a nonspecific cation (NSC) current was elicited. The NSC current had a mean reversal potential
of +5.7 mV in 130 mm extracellular NaCl with Cs+-aspartate in the pipette, and was not affected by alterations in the extracellular Ca2+ or Cl− concentration. The GTPγS-activated current was found to be permeable to several monovalent cations (K+, Na+, choline, TRIS, and NMDG). Addition of fluoroaluminate, an activator of large molecular weight heterotrimeric GTP-binding
proteins (G proteins), to the intracellular recording solution activated the NSC current. The G protein involved was pertussis
toxin (PTX)-sensitive, since GTPγS failed to activate the NSC current in cells pretreated with PTX. Further investigation
of second messenger molecules suggested that activation of the NSC current was not affected by alterations in intracellular
Ca2+ or ATP. From these results, we conclude that a G protein-regulated NSC current is present in rat RPE cells. Activation of
the NSC current may sufficiently depolarize RPE cells to activate outward K+ currents. This would provide a mechanism by which these cells could rid themselves of accumulated K+.
Received: 25 January 1996/Revised: 24 April 1996 相似文献
45.
Determination of the entire nucleotide sequence of the aphid 28S ribosomal RNA gene (28S rDNA) revealed that it is 4,147 by
in length with a G + C content of 60.3%. Based on the nucleotide sequence, we constructed a presumed secondary-structure model
of the aphid 28S rRNA which indicated that the aphid 28S rRNA is characterized by the length and high G + C content of its
variable regions. The G + C content of the aphid's variable regions was much higher than that of the entire sequence of the
28S rRNA, which formed a striking contrast to those ofDrosophila with the G + C content much lower than the entire 28S molecule. In this respect, the aphid 28S rRNA somewhat resembled those
of vertebrates. This is the third report of a complete large-subunit rRNA sequence from an arthropod, and the first 28S rRNA
sequence for a nondipterous insect.
Correspondence to: H. Ishikawa 相似文献
46.
P. J. Flor J. Gomeza M. A. Tones R. Kuhn J.-P. Pin T. Knöpfel 《Journal of neurochemistry》1996,67(1):58-63
Abstract: The metabotropic glutamate receptor (mGluR) subtype 1 exists as at least three variants (−1a, −1b, and −1c) generated by alternative splicing at the C-terminal domain. Fluorometric Ca2+ measurements were used to compare the concentration dependency of agonist-induced rises in intracellular free Ca2+ concentration ([Ca2+ ]i ) in human embryonic HEK 293 cells transiently expressing rat mGluR1a, mGluR1b, or mGluR1c. The rank order of agonist potencies was quisqualate ≫ (2 S, 1' S, 2' S )-2-(carboxycyclopropyl)glycine (L-CCG-I) > (1 S, 3 R )-1-aminocyclopentane-1,3-dicarboxylic acid [(1 S, 3 R )-ACPD] and did not differ among the splice variants. However, agonists were consistently more potent at mGluR1a than at mGluR1c and mGluR1b. In the same system, we characterized the agonist pharmacology of two chimeric rat mGluR3/1 receptors where the first and/or the second intracellular loop(s) and the C-terminal domain were exchanged with the corresponding mGluR1a or mGluR1c sequences and that were previously shown to mediate elevations in [Ca2+ ]i in response to agonists. The potency of agonists was higher at the chimera having the C-terminus of mGluR1a as compared with those having the mGluR1c C-terminus. Both chimeric mGluR3/1 receptors had the same rank order of agonist potencies: L-CCG-I ≫ (1 S, 3 R )-ACPD ∼ quisqualate. These data support the hypothesis that the C-terminal domain of mGluRs plays a role in determining the potency of agonists for inducing mGluR-mediated functional responses. 相似文献
47.
Since plants can be transformed genetically to produce functional antibodies, an immunological approach may be developed for controlling their arthropod pests. Specific antibodies would protect plants from arthropods if they could gain access to the pest antigen in sufficient amounts such that the normal function of the antigen is disrupted. In order to study the fate of ingested antibodies in the body of the European corn borer (ECB), Ostrinia nubilalis (Hübner), (Lepidoptera: Pyralidae), we fed the larvae on serum-containing diet. When larvae were fed on the serum-containing diet for various lengths of time between 12 and 96 h, no significant differences were noted in the immunoglobulin G (IgG) concentration in their body. Immediately after the larvae stopped feeding, the concentrations of the IgG in their midgut was about one half that of the diet itself, but it decreased significantly after 6 h and again after 18 h (about 3 and 10 fold, respectively). Immediately after the larvae stopped feeding, the concentration of the IgG in their hemolymph was about 1/500 that in the diet. The concentration of IgG in the hemolymph of ECB larvae was influenced directly by the titer of antibodies in their diet. During the first 6 h after the larvae stop feeding the concentration of IgG in their hemolymph did not decrease significantly; however, it did so after 18 h (about 6 fold). The possibility that specific antibodies will gain access to antigens in the ECB body is discussed. 相似文献
48.
49.
50.
Amina El Jamali Nadia Rachdaoui Claude Jacquemin Claude Corrèze 《Journal of neurochemistry》1996,67(6):2532-2539
Abstract: Long-term (48-h) forskolin treatment of rat astroglial cells led to a slight decrease (30–40%) in the response to isoproterenol, vasoactive-intestinal peptide, guanyl 5'-(βγ-imido)diphosphate, guanosine 5'- O -(3-thiotriphosphate) [GTP(S)], and AIF4 − in crude membrane fractions. In contrast, the acute stimulatory effect of forskolin was increased by 1.25–1.5-fold. These two opposite effects of forskolin were mediated by a cyclic AMP-dependent mechanism. No changes in Gs α, Gi α, or Gβ protein levels could be determined by immunoblotting using specific antisera. No significant differences were observed in the ability of G proteins extracted from control and forskolin-treated cells to reconstitute a full adenylyl cyclase activity in membranes from S49 cyc− cells, lacking Gs α protein. Gs α proteins were detected in two pools of membranes, one in the heavy sucrose fractions and the other in light sucrose fractions. Forskolin treatment of the cells shifted Gs α protein toward the light-density membranes. We did not find any significant change in the distribution of adenylyl cyclase. In contrast to the decreased stimulation of adenylyl cyclase activity by agonists acting via Gs α, observed in the crude membrane fraction, the responses of adenylyl cyclase to forskolin as well as to GTP(S) were increased in the purified plasma membrane fractions. These results may indicate that sensitization of the catalyst appears to be the dominant component in the astroglial cell response to long-term treatment by forskolin. 相似文献