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291.
Alan K. Keenan Alma Gal Alexander Levitzki 《Biochemical and biophysical research communications》1982,105(2):615-623
Turkey erythrocyte adenylate cyclase was activated by GppNHp and l-epinephrine to its stable, highly active form. In this form the enzyme could be solubilized by Lubrol-PX and subsequently re-inserted into phospholipid vesicles concomitantly with the removal of up to 99.3% of the Lubrol. The ability of GTP and l-epinephrine to reverse the GppNHp/epinephrine activated state was taken as a measure for the reappearance of hormone sensitivity in the reconstituted vesicles. An incomplete but significant reappearance of hormone sensitivity in the reconstituted adenylate cyclase was achieved. This hormone sensitivity was found to be stereospecific for (?)epinephrine. The 125I-cyanopindolol binding properties of the reconstituted β-receptor depend on the nature of the detergent and the phospholipids used in the reconstitution. 相似文献
292.
DeHaven-Hudkins DL Cowan A Cortes Burgos L Daubert JD Cassel JA DeHaven RN Kehner GB Kumar V 《Life sciences》2002,71(23):2787-2796
Loperamide and three of its analogs were evaluated for their ability to inhibit binding to cloned human opioid receptor subtypes and to produce antipruritis and antinociception following local s.c. administration to rodents. All four compounds were fully efficacious agonists with affinities of 2 to 4 nM for the cloned human mu opioid receptor. Local s.c. injection of loperamide, ADL 01-0001 or ADL 01-0002 at the same site as the introduction of the pruritogenic compound 48/80 resulted in antipruritic activity in a mouse model of itch. Similarly, i.paw or i.pl. administration of compounds ADL 01-0001, ADL 01-0002 and ADL 01-0003 to inflamed paws caused potent antinociception, inhibiting late phase formalin-induced flinching, Freund's adjuvant-induced mechanical hyperalgesia and tape stripping-induced mechanical hyperalgesia. Loperamide and its analogs were efficacious in animal models of itch and inflammatory pain, and may have potential therapeutic utility as antipruritic and antihyperalgesic agents. 相似文献
293.
Edward L. Schwartz Anthony F. Hadfield Alfred E. Brown Alan C. Sartorelli 《Biochimica et Biophysica Acta (BBA)/Molecular Cell Research》1983,762(4):489-497
Two analogs of N-acetylmannosamine, (Ac4-NAcMan) and the 2-trifluoroacetamido derivative (Ac4F3-NAcMan), were synthesized as potential inhibitors of the formation of sialic acid-containing glycoconjugates and were examined for their ability to modify the incorporation of into cellular glycoconjugates of Friend murine erythroleukemia cells. Ac4F3-NAcMan and Ac4-NAcMan inhibited cellular replication in suspension culture at concentrations of 0.02 and 0.08 mM, respectively. The cytotoxicity of Ac4-NAcMan was relatively reversible, whereas that produced by Ac4F3-NAcMan was not, as judged by measurement of the cloning efficiencies of cells exposed to these agents. The analogs inhibited incorporation of into ethanol-soluble and -insoluble materials. Separation of ethanol-soluble metabolites by HPLC demonstrated that Ac4F3-NAcMan caused accumulation of radioactivity from in CMP-N-acetylneuraminic acid (CMP-NeuNAc) equal to the decrease in macromolecular-bound 3H caused by this agent. In contrast, similar exposure to Ac4-NAcMan produced a large increase in the amount of radioactivity in ethanol-soluble N-acetylneuraminic acid while decreasing the amount of label from in cellular CMP-NeuNAc, suggesting that the analogs differ in their biochemical sites of action. Treatment of cells with either analog increased the amount of neuraminidase-hydrolyzable sialic acid-like material on the cell surface; this appeared to be due to the incorporation of the analogs into cellular glycoconjugates, since incubation of cells with 3H-labeled analogs resulted in the appearance of radioactivity in cellular ethanol-insoluble and neuraminidase-hydrolyzable material. Incubation of cells with Ac4-NAcMan labeled with 14C in the 4-O-acetyl group further demonstrated that incorporation occurred with approx. 50% retention of this substituent. Thus, both the amount and the nature of the surface sialic acid constituents of treated cells were altered, suggesting that these or similar analogs could potentially be used to modify cellular membrane function. 相似文献
294.
Menani JV Barbosa SP De Luca LA De Gobbi JI Johnson AK 《American journal of physiology. Regulatory, integrative and comparative physiology》2002,282(3):R837-R841
Central cholinergic mechanisms are suggested to participate in osmoreceptor-induced water intake. Therefore, central injections of the cholinergic agonist carbachol usually produce water intake (i.e., thirst) and are ineffective in inducing the intake of hypertonic saline solutions (i.e., the operational definition of sodium appetite). Recent studies have indicated that bilateral injections of the serotonin receptor antagonist methysergide into the lateral parabrachial nucleus (LPBN) markedly increases salt intake in models involving the activation of the renin-angiotensin system or mineralocorticoid hormones. The present studies investigated whether sodium appetite could be induced by central cholinergic activation with carbachol (an experimental condition where only water is typically ingested) after the blockade of LPBN serotonergic mechanisms with methysergide treatment in rats. When administered intracerebroventricularly in combination with injections of vehicle into both LPBN, carbachol (4 nmol) caused water drinking but insignificant intake of hypertonic saline. In contrast, after bilateral LPBN injections of methysergide (4 microg), intracerebroventricular carbachol induced the intake of 0.3 M NaCl. Water intake stimulated by intracerebroventricular carbachol was not changed by LPBN methysergide injections. The results indicate that central cholinergic activation can induce marked intake of hypertonic NaCl if the inhibitory serotonergic mechanisms of the LPBN are attenuated. 相似文献
295.
Stephen Millam Alan T. H. Burns Trevor J. Hocking 《Plant Cell, Tissue and Organ Culture》1991,24(1):43-47
The effects of three different general purification protocols have been assessed quantitatively using mesophyll protoplasts of Brassica napus. Within the initial sample two distinct sub-populations were determined. The methods used influenced the ratio of the vacuolated to chloroplastic type protoplast sub-populations. Overall recovery rates of the initial sample varied according to the method used from 38% to 27%, but the relative recovery of the sub-populations varied considerably with a purified ratio of between 1.0:0.78 to 1.0:7.0. Size distribution profiles of the initial and purified populations are also presented. 相似文献
296.
Soltani Mehdi Badzohreh Gholamreza Mirzargar Saed Farhangi Mehrdad Shekarabi Pezhman Hosseini Lymbery Alan 《Probiotics and antimicrobial proteins》2019,11(3):765-773
Probiotics and Antimicrobial Proteins - Growth behavior and production of short-chain fatty acid (SCFA) of two probiotics, Pediococcus acidilactici and Lactococcus lactis, each at... 相似文献
297.
298.
299.
This study examines the efficacy of published δ18O data from the calcite of Late Miocene surface dwelling planktonic foraminifer shells, for sea surface temperature estimates for the pre-Quaternary. The data are from 33 Late Miocene (Messinian) marine sites from a modern latitudinal gradient of 64°N to 48°S. They give estimates of SSTs in the tropics/subtropics (to 30°N and S) that are mostly cooler than present. Possible causes of this temperature discrepancy are ecological factors (e.g. calcification of shells at levels below the ocean mixed layer), taphonomic effects (e.g. diagenesis or dissolution), inaccurate estimation of Late Miocene seawater oxygen isotope composition, or a real Late Miocene cool climate. The scale of apparent cooling in the tropics suggests that the SST signal of the foraminifer calcite has been reset, at least in part, by early diagenetic calcite with higher δ18O, formed in the foraminifer shells in cool sea bottom pore waters, probably coupled with the effects of calcite formed below the mixed layer during the life of the foraminifera. This hypothesis is supported by the markedly cooler SST estimates from low latitudes—in some cases more than 9 °C cooler than present—where the gradients of temperature and the δ18O composition of seawater between sea surface and sea bottom are most marked, and where ocean surface stratification is high. At higher latitudes, particularly N and S of 30°, the temperature signal is still cooler, though maximum temperature estimates overlap with modern SSTs N and S of 40°. Comparison of SST estimates for the Late Miocene from alkenone unsaturation analysis from the eastern tropical Atlantic at Ocean Drilling Program (ODP) Site 958—which suggest a warmer sea surface by 2-4 °C, with estimates from oxygen isotopes at Deep Sea Drilling Project (DSDP) Site 366 and ODP Site 959, indicating cooler than present SSTs, also suggest a significant impact on the δ18O signal. Nevertheless, much of the original SST variation is clearly preserved in the primary calcite formed in the mixed layer, and records secular and temporal oceanographic changes at the sea surface, such as movement of the Antarctic Polar Front in the Southern Ocean. Cooler SSTs in the tropics and sub-tropics are also consistent with the Late Miocene latitude reduction in the coral reef belt and with interrupted reef growth on the Queensland Plateau of eastern Australia, though it is not possible to quantify absolute SSTs with the existing oxygen isotope data. Reconstruction of an accurate global SST dataset for Neogene time-slices from the existing published DSDP/ODP isotope data, for use in general circulation models, may require a detailed re-assessment of taphonomy at many sites. 相似文献
300.
Bengt Fellström Faiez Zannad Roland Schmieder Hallvard Holdaas Alan Jardine Helen Rose Wim Wilpshaar 《Trials》2005,6(1):1-8