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81.
Stereognostic coordination chemistry 4 the design and synthesis of a selective uranyl ion complexant
A new approach to ligand design for the sequestration of metal-oxo cations has been called stereognostic coordination chemistry, in that the ligand incorporates a traditional Lewis base coordination to the metal center and a hydrogen bond donor to interact with the oxo group. This paper reports the synthesis of ligands that are more rigid and sterically predisposed to bind the targeted UO22+ cation. These are the tripod ligands tris-N,N′,N′′-[2-(2-carboxy-phenoxy)ethyl]-1,4,7-triazacyclononane bis-hydrochloride (ETAC · 2HCl) and tris-N,N′,N′′-[2-(2-carboxy-4-decyl-phenoxy)ethyl]-1,4,7-triazacyclononane tris-hydrochloride (DETAC · 3HCl), which chelate uranyl with a tris-carboxylate coordination sphere and provide a hydrogen bond donor through a protonated amine on the triazacyclononane macrocycle to interact with one uranyl oxo atom. Structural models predict that upon uranyl binding the hydrogen bond donor must point directly towards the oxo atom, enforcing a stereognostic interaction. Both ETAC and DETAC chelate the uranyl ion; DETAC is a powerful extractant and will quantitatively extract uranyl into an organic phase at pH 1.9 and above. The extraction coefficient is estimated to be 1014 in neutral aqueous conditions. Vibrational spectra of 18O labeled UO22+ have been used to probe the stereognostic coordination to uranyl utilizing hydrogen bonding. 相似文献
82.
Sacred groves in the Moyamba District of Sierra Leone were assessed for their value to local herbalists and traditional folk medicine practitioners of the Kpaa Mende people. Herbalists (tufablaa) collecting in 23 sacred groves were interviewed regarding their general knowledge of medicinal plants, and their perceptions regarding changes in the occurrence of medicinal plants. Over 75 medicinal plant remedies are currently in use among the Kpaa Mende, with some plants reported here for the first time in terms of their medicinal uses in Sierra Leone. A significant feature of Kpaa Mende ethnobotany is the employment of 2 or more kinds of plants in combination as a remedy for particular afflictions. The discovery of rare and uncommon plants in the groves and their medicinal uses are discussed in terms of the role of the sacred groves in medicinal plant conservation. 相似文献
83.
Alexander A. Kortt Robin E. Guthrie Mark G. Hinds Barbara E. Power Neva Ivancic J. Bruce Caldwell L. Clem Gruen Raymond S. Norton Peter J. Hudson 《Journal of Protein Chemistry》1995,14(3):167-178
The VH domain of anti-influenza neuraminidase antibody NC41, with and without a C-terminal hydrophilic marker peptide (FLAGTM), has been expressed in high yield (15–27 mg/L) inEscherichia coli. Both forms were secreted into the periplasm where they formed insoluble aggregates which were solubilized quantitatively with 2 M guanidine hydrochloride and purified to homogeneity by ion-exchange chromatography. The VH-FLAG was composed of three isoforms (pI values of 4.6, 4.9, and 5.3) and the VH molecule was composed of two isoforms with pI values of 5.1 and 6.7; the difference between the VH isoforms was shown to be due to cyclization of the N-terminal glutamine residue in the pI 5.1 isoform. At 20°C and concentrations of 5–10mg/ml the VH domain dimerized in solution and then partly precipitated, resulting in the broadening of resonances in its1H NMR spectrum. Reagents such as CHAPS,n-octylglucoside, and ethylene glycol, which presumably mask the exposed hydrophobic interface of the VH molecule, prevented dimerization of the VH and permitted good-quality NMR spectra on isotope-labeled protein to be obtained. 相似文献
84.
Raymond R. Padua Rajat Sethi Naranjan S. Dhalla Elissavet Kardami 《Molecular and cellular biochemistry》1995,143(2):129-135
To examine whether basic fibroblast growth factor (bFGF) administered to the heart by perfusion can improve cardiac resistance to injury we employed an isolated rat heart model of ischemia-reperfusion injury and determined the extent of functional recovery in bFGF-treated and control hearts. Global ischemia was simulated by interruption of flow for 60 min. Recovery of developed force of contraction (DF), recorded after reestablishment of flow for 30 min, reached 63.8±1.5% and 96.5±3.5% of preischemic levels in control and bFGF-treated hearts (10 g/heart), respectively, indicating that bFGF induced significantly improved recovery of mechanical function. Recoveries of the rates of contraction or relaxation were also significantly improved in bFGF-treated hearts. Extent of myocardial injury, assessed by determination of phosphocreatine kinase in the effluent, was reduced as a result of bFGF treatment. As a first step towards understanding the mechanism and direct cellular target(s) of bFGF-induced cardioprotection, we investigated its fate after perfusion. Perfusion of 10 g bFGF/heart resulted in a 4-fold increase in bFGF associated with the heart compared to control levels, as estimated by biochemical fractionation and immunoblotting. Immunofluorescent staining of the bFGF-perfused hearts revealed intense anti-bFGF staining in association with blood vessels as well as the periphery of cardiomyocytes, suggesting that the latter may be a target for direct bFGF action. In conclusion, our findings of bFGF-induced increases in cardiac resistance to, and improved functional recovery from, ischemia-reperfusion injury indicate that bFGF may have clinical applications in the treatment of ischemic heart disease. 相似文献
85.
Net Glutamate Release from Astrocytes Is Not Induced by Extracellular Potassium Concentrations Attainable in Brain 总被引:2,自引:0,他引:2
Abstract: Elevated extracellular potassium concentration ([K+ ]e ) has been shown to induce reversal of glial Na+ -dependent glutamate uptake in whole-cell patch clamp preparations. It is uncertain, however, whether elevated [K+ ]e similarly induces a net glutamate efflux from intact cells with a physiological intracellular milieu. To answer this question, astrocyte cultures prepared from rat and mouse cortices were incubated in medium with elevated [K+ ]e (by equimolar substitution of K+ for Na+ ), and glutamate accumulation was measured by HPLC. With [K+ ]e elevations to 60 m M , medium glutamate concentrations did not increase during incubation periods of 5–120 min. By contrast, 45 min of combined inhibition of glycolytic and oxidative ATP production increased medium glutamate concentrations 50–100-fold. Similar results were obtained in both rat and mouse cultures. Studies were also performed using astrocytes loaded with the nonmetabolized glutamate tracer d -aspartate, and parallel results were obtained; no increase in medium d -aspartate content resulted from [K+ ]e elevation up to 90 m M , whereas a large increase occurred during inhibition of energy metabolism. These results suggest that a net efflux of glutamate from intact astrocytes is not induced by any [K+ ]e attainable in brain. 相似文献
86.
Lipsitz Lewis A.; Morin Raymond; Gagnon Margaret; Kiely Dan; Medina Aharon 《Journal of applied physiology》1997,83(2):383-390
Lipsitz, Lewis A., Raymond Morin, Margaret Gagnon, DanKiely, and Aharon Medina. Vasomotor instability precedingtilt-induced syncope: does respiration play a role? J. Appl. Physiol. 83(2): 383-390, 1997.This studyaimed to determine whether alterations in cardiovascular dynamicsbefore syncope are related to changes in spontaneous respiration.Fifty-two healthy subjects underwent continuous heart rate (HR),arterial blood pressure (BP), and respiratory measurements during10-min periods of spontaneous and paced breathing (0.25 Hz) in thesupine and 60° head-up tilt positions. Data were evaluated by powerspectrum and transfer function analyses. During tilt, 27 subjectsdeveloped syncope or presyncope and 25 remained asymptomatic. Subjectswith tilt-induced syncope had significantly greater increases inlow-frequency (0.04-0.15 Hz) systolic BP, diastolic BP, and HRpower during tilt than the asymptomatic subjects(P 0.01). This difference waspresent during spontaneous but not paced breathing. However, averagetidal volume, respiratory rate, minute ventilation, proportion ofbreaths below 0.15 Hz, and low-frequency respiratory power during tilt did not differ between syncopal and nonsyncopal subjects. Transfer magnitudes between low-frequency respiration and BP, and between BP andinterbeat interval, were also similar between groups. Thus vasomotorinstability before syncope is not related to alterations in respirationor the cardiovagal baroreflex but may reflect oscillating centralsympathetic outflow to the vasculature. 相似文献
87.
Kingston Janene K.; Geor Raymond J.; McCutcheon Laura Jill 《Journal of applied physiology》1997,83(4):1133-1143
Kingston, Janene K., Raymond J. Geor, and Laura JillMcCutcheon. Rate and composition of sweat fluid losses areunaltered by hypohydration during prolonged exercise in horses.J. Appl. Physiol. 83(4):1133-1143, 1997. Rate and ionic composition of sweat fluid losses and partitioning of evaporative heat loss into respiratory and cutaneous components were determined in six horses during three 15-km phases of exercise at ~40% of maximalO2 uptake. Pattern of change insweat rate (SR) and composition was similar during each phase. SRincreased rapidly for the first 20 min of exercise but remained at~24-28ml · m2 · min1during the remainder of each phase. Similarly, the concentrations of Naand Cl in sweat increased until 30 min of exercise but were unchangedthereafter. Sweat osmolality and concentrations of Na and Cl werepositively correlated with SR. Sweat K concentration decreased duringexercise but was not correlated with SR. Fluid losses were 33.8 ± 1.5 liters, resulting in decreases of ~21% in plasma volume and~11% in total body water. The ~6% hypohydration was notassociated with an alteration in SR, sweat composition, or heatstorage. Respiratory and cutaneous evaporative heat loss represented~23 and 70%, respectively, of the total heat dissipated, and thepartitioning of heat loss was similar in each exercise phase. Weconclude that SR and the relative proportions of respiratory andcutaneous evaporative heat loss are unchanged in horses during prolonged low-intensity exercise despite moderate hypohydration. 相似文献
88.
A common gene for juvenile and adult-onset primary open-angle glaucomas confined on chromosome 1q. 总被引:11,自引:2,他引:9 下载免费PDF全文
J Morissette G Ct J L Anctil M Plante M Amyot E Hon G E Trope J Weissenbach V Raymond 《American journal of human genetics》1995,56(6):1431-1442
Primary open-angle glaucoma (POAG), which causes progressive loss of the visual fields, was subdivided into two groups according to age at onset: (1) chronic open-angle glaucoma (COAG) diagnosed after age 40 years and (2) juvenile open-angle glaucoma (JOAG) diagnosed between 3 years of age and early adulthood. A JOAG gene (GLC1A) was recently mapped to chromosome 1q. We studied 142 members of a huge multigenerational French Canadian family affected with autosomal dominant POAG. Either JOAG or COAG was diagnosed in 40 patients. Six subjects were also diagnosed with ocular hypertension (OHT), which may lead to POAG. To localize a common disease gene that might be responsible for both glaucoma subsets, we performed linkage analysis considering JOAG and COAG under the same phenotypic category. JOAG/COAG was tightly linked to seven microsatellite markers on chromosome 1q23-q25; a maximum lod score of 6.62 was obtained with AF-M278ye5. To refine the disease locus, we exploited a recombination mapping strategy based on a unique founder effect. The same characteristic haplotype, composed of 14 markers spanning 12 cM between loci D1S196 and D1S212, was recognized in all persons affected by JOAG, COAG, or OHT, but it did not occur in unaffected spouses and in normal family members > 35 years of age, except for three obligatory carriers. Key recombination events confined the disease region within a 9-cM interval between loci D1S445 and D1S416/D1S480. These observations demonstrate that the GLC1A gene is responsible for both adult-onset and juvenile glaucomas and suggest that the JOAG and COAG categories within this family may be part of a clinical continuum artificially divided at age 40 years. 相似文献
89.
Summary We have investigated features for minimizing the inactivation of tyrosinase (E.C. 1.14.18.1) that is caused by immobilization on glass beads and Celite®. The degree of inactivation is dependent on the enzyme loading and the carrier's surface area. Addition of a sacrificial protein during the immobilization procedure offers a protective effect with increased residual activity on the basis of comparable enzyme loading. 相似文献
90.
Richard L. Schading Raymond I. Carruthers Barbara A. Mullin-Schading 《Biocontrol Science and Technology》1995,5(2):201-208
The viability of conidia from two species of deuteromycetes fungi pathogenic to insects was determined using two fluorochrome stains, fluorescein diacetate (FDA) and propidium iodide (PI). These stains were used either alone or in combination, and results were compared with standard conidial germination tests. FDA fluoresces bright green in viable conidia and PI fluoresces red in non-viable conidia, when viewed using specific fluorescence microscopic techniques. Conidia from two isolates of Paecilomyces fumosoroseus (Wize) Brown and Smith and two isolates of Beauveria bassiana (Balsamo) Vuillemin were evaluated. Conidia were suspended in deionized water and half of each suspension was treated with microwave radiation to kill all the conidia. Conidia were tested for viability in non-microwaved suspensions in a mixture (ca. 1:1) of viable and non-viable conidial suspensions, and in the microwaved suspensions that contained all non-viable conidia. No significant differences were observed for the four isolates tested between germination tests on water and agar and viability tests conducted with FDA alone or FDA in combination with PI. One isolate of B. bassiana that had been damaged in storage was also tested. Differences were observed between the actual germination and the percentage of viability determined using FDA or FDA plus PI. Damaged conidia maintained a measure of viability and fluoresced green, but did not fully germinate. 相似文献