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121.
Dale R. Disharoon M. Gary Wickham David M. Worthen Fred H. Lofftus 《Biotechnic & histochemistry》1983,58(3):143-151
The quality of sections obtained by microtomy depends to a large extent on the quality and characteristics of the microtome knife itself. Despite the need for improved microtomy techniques, there have been few significant developments since the introduction of glass and diamond knives in the 1950's. The manufacture of microtome knives from vitreous carbon provides new possibilities for developing both improved methods and improved equipment for specimen sectioning. Vitreous carbon has unique physical properties that lend themselves to the generation of precision cutting edges. Such an edge can be obtained either by breaking a piece of vitreous carbon or by using lapidary techniques. The resultant edge seems well adapted to both thick and thin sectioning. The introduction of vitreous carbon as a sectioning tool offers a significant alternative to metal, glass and diamond knives. 相似文献
122.
Fred Stutzenberger 《Journal of industrial microbiology & biotechnology》1991,7(4):243-249
Summary Protein-extracted lucerne fiber was used as carbon and energy source for production of extracellular polygalacturonate lyase byThermomonospora curvata. The optimal fiber concentration was 1.5% (w/v); peal lyase activity in culture fluid occurred after 3 days growth at 53°C. During that time, lyase biosynthesis was controlled through induction; production was accelerated by adding small amounts of pectin or by grinding the fiber to 40-mesh particle size to release more inducer. After 3 days growth, lyase activity decreased; inactivation of the enzyme was delayed by the presence of 1 mM Ca or by inhibition of serine proteases with 0.05 mM phenylmethylsulfonyl fluoride. The molecular weight of the lyase produced during growth on the fiber was 35 kDa compared to 56 kDa for the enzyme produced on pure pectin. TheK
m
of the 35-kDa form was 0.54% pectin compared to 0.06% for the 56-kDa form. The smaller form was rapidly inactivated at 60°C, the optimal temperature for activity of the larger form. 相似文献
123.
S I Simon J D Chambers E Butcher L A Sklar 《Journal of immunology (Baltimore, Md. : 1950)》1992,149(8):2765-2771
Neutrophil aggregation in response to formyl peptide was analyzed in blood and isolated cells by fluorescence flow cytometry. The isolated leukocyte aggregates and the leukocytes in blood were identified with the vital nucleic acid stain LDS-751. This method enabled us to discriminate nucleated cells from other blood cells and to detect granulocyte aggregates without isolation or E lysis. Cells isolated in the absence of endotoxin retained the characteristics of cells in blood and exhibited similar aggregation kinetics and dose-response to formyl peptide. We show that it is possible to analyze epitope expression in blood with homogeneous flow cytometric assays and that carefully isolated neutrophils retain the expression characteristics of those in blood. The expression of CD18 was at its lowest levels in unstimulated cells, while the rate of formyl peptide stimulated aggregation was most rapid in these cells. Aggregation in isolated cells as well as blood preceded an increase in receptor expression. After stimulation, L-selectin expression decreased in both blood and isolated cells over a time frame similar to disaggregation. The aggregation response in blood was blocked by pretreatment with antibody to CD18 over a concentration range consistent with the amount of antibody bound. Aggregation was also blocked in isolated cells and blood by antibodies DREG-200 and DREG-56 to L-selectin, but not by isotype controls or anti-LFA-1. The results are discussed in terms of the roles of adhesive receptor expression and recognition in neutrophil aggregation. The methods validated here permit linkage between isolated cells and in vivo studies. 相似文献
124.
R Weingarten L Ransn?s H Mueller L A Sklar G M Bokoch 《The Journal of biological chemistry》1990,265(19):11044-11049
Mastoparan, a peptide toxin from wasp venom, stimulates guanine nucleotide binding and hydrolysis by G proteins. To elucidate the site of mastoparan-G protein interaction, we utilized a polyclonal antibody (R16,17) directed against the carboxyl terminus of the Gi alpha subunit to develop a competitive enzyme-linked immunosorbent assay. We investigated the ability of mastoparan to influence R16,17 antibody binding to G protein alpha subunits in a purified preparation of brain Gi and in neutrophil membrane extracts. Mastoparan antagonized the ability of R16,17 to detect G protein alpha subunits with an IC50 of 15 microM in the purified preparation and with an IC50 of 1 microM for the predominant G protein population in membrane extracts. This reduction was not seen when an unrelated peptide or a peptide of similar charge composition to mastoparan was used in place of mastoparan in the assay. Additionally, antibody R16,17 blocked up to 85% of mastoparan-stimulated GTPase activity. Taken together, these data indicate that the interaction of mastoparan with G protein depends in part on the carboxyl terminus of Gi alpha. Pertussis toxin-catalyzed ADP-ribosylation of Gi alpha markedly inhibited mastoparan-stimulated GTPase activity but only slightly attenuated the ability of mastoparan to recognize G protein. These data suggest that ribosylation inhibits mastoparan-induced G protein activation by a mechanism distinct from the ability of mastoparan to physically interact with G protein. Since mastoparan is thought to mimic hormone-liganded receptors, these findings may be applicable to the mechanism of receptor-Gi protein uncoupling that results from ADP-ribosylation of the G protein. 相似文献
125.
126.
Aren van Waarde Guido van den Thillart Fred Dobbe 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1982,147(1):53-59
Summary Changes in the concentrations of ammonia, glutamate, alanine, aspartate, -ketoglutarate, oxaloacetate and succinate were measured in freeze-clamped lateralred muscle, dorsal white muscle and liver, and in rapidly cooled blood of goldfish after 12 h of anoxia. Alanine accumulation, succinate accumulation and aspartate depletion are observed in all tissues examined; in the liver the concentrations of glutamate increase and those of ammonia decrease. The mass-action ratio of the glutamate-pyruvate transaminase-catalyzed reaction stays within one order of magnitude from thermodynamic equilibrium in the direction of alanine formation. The mass-action ratio of the glutamate-oxaloacetate transaminase reaction is far from equilibrium when measured oxaloacetate concentrations are used. When levels of free oxaloacetate are calculated from LDH and MDH equilibrium constants, the mass-action ratio of glutamate-oxaloacetate transamination is close to equilibrium in the direction of aspartate formation. Since neither alanine nor glutamate decreases, and since ammonia gradients suggest a continuous ammonia production in all tissues examined, anaerobic proteolysis is assumed. A possible coupling between amino acid catabolism and ethanol production is discussed.Abbreviations
ALA
alanine
-
ASP
aspartate
-
EDTA
ethylene diamine tetraacetate
-
FP
ox
oxidated flavoprotein
-
FP
red
reduced flavoprotein
-
FUM
fumarate
-
GLU
glutamate
-
GOT
glutamate oxaloacetate transaminase
-
GPT
glutamate pyruvate transaminase
-
IMP
inosine monophosphate
- KG
-ketoglutarate
-
LDH
lactate dehydrogenase
-
MAL
malate
-
MAR
mass action ratio
-
MDH
malate dehydrogenase
-
OAA
oxaloacetate
-
PYR
pyruvate
-
sAMP
adenylosuccinate
-
SDH
succinate dehydrogenase
-
SUCC
succinate 相似文献
127.
Summary The intratesticular excurrent duct system of the bull is composed of rete testis, tubuli recti, and the terminal segment of the seminiferous tubules. Each terminal segment is surrounded by a vascular plexus and may be subdivided into a transitional region, middle portion, and terminal plug. The modified supporting cells of the middle portion and the terminal plug no longer display the typical Sertoli-Sertoli junctions seen in the transitional region and the seminiferous tubule proper. In the region of the terminal plug a distinct central lumen is generally not observed: spermatozoa and tubular fluid must pass through an intricate system of communicating clefts between the apices of the closely attached modified supporting cells. Vacuoles in the supranuclear region of the cells in the middle portion indicate strong transepithelial fluid transport. In analogy to the epithelium of rete testis and tubuli recti, the supporting cells of the terminal segment are capable of phagocytosing spermatozoa. The vascular plexus investing the terminal segment serves a dual purpose: it is a regulatory device for fluid and sperm transport, as well as an area of increased diapedesis for white blood cells.Supported by a grant from the Deutsche Forschungsgemeinschaft 相似文献
128.
Milford H. Wolpoff Fred H. Smith Mirko Malez Jakov Radov
i Darko Rukavina 《American journal of physical anthropology》1981,54(4):499-545
Human remains excavated from Vindija cave include a large although fragmentary sample of late Mousterian-associated specimens and a few additional individuals from the overlying early Upper Paleolithic levels. The Mousterian-associated sample is similar to European Neandertals from other regions. Compared with earlier Neandertals from south central Europe, this sample evinces evolutionary trends in the direction of Upper Paleolithic Europeans. Compared with the western European Neandertals, the same trends can be demonstrated, although the magnitude of difference is less, and there is a potential for confusing temporal with regional sources of variation. The early Upper Paleolithic-associated sample cannot be distinguished from the Mousterian-associated hominids. We believe that this site provides support for Hrdli?ka's “Neandertal phase” of human evolution, as it was originally applied in Europe. 相似文献
129.
Surface Changes in Mild Steel Coupons from the Action of Corrosion-Causing Bacteria 总被引:7,自引:4,他引:3
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Christian O. Obuekwe Donald W. S. Westlake Fred D. Cook J. William Costerton 《Applied microbiology》1981,41(3):766-774
Changes which occur on the surface of mild steel coupons submerged in cultures of an Fe(III)-reducing bacterium, isolated from corroded pipe systems carrying crude oil, were studied microscopically to investigate the interaction between the corrosion-causing bacterium and the corroding mild steel coupon. Under micro-aerobic conditions and in the absence of the bacteria, a dense, crystalline, amorphous coat formed on the surface of the steel coupons. In the presence of bacteria the surface coat was extensively removed, exposing the bare metal to the environment. After about 2 weeks of exposure, the removal of the surface coating was followed by colonization of the metal surface by the bacteria. Colonization was mediated by fibrous, exopolysaccharidic material formed by the bacteria. Extension of studies to other bacteria isolated from crude oil and corroded pipes reveals that the formation of exopolysaccharide fibers and possession of adherent properties are common characteristics of bacteria from crude oil systems. 相似文献
130.
The fate of the N-formyl-chemotactic peptide receptor in stimulated human granulocytes: subcellular fractionation studies 总被引:4,自引:0,他引:4
A J Jesaitis J R Naemura R G Painter M Schmitt L A Sklar C G Cochrane 《Journal of cellular biochemistry》1982,20(2):177-191
Experiments were performed to examine how human granulocytes, stimulated by N-formyl-chemotactic peptides, process the N-formyl peptide receptor. One percent of the surface N-formyl-chemotactic peptide receptors of purified human granulocytes were covalently, specifically, and radioactively labeled at 4 degrees C using the photochemically reactive N-formyl-chemotactic hexapeptide CHO-Nle-Leu-Phe-Nle-[125I] Tyr-N epsilon (6-(4'-azido-2'-nitrophenyl-amino)hexanoyl)-Lys. After incubation in the presence of 500 nM of N-formyl-Met-Leu-Phe at 37 degrees C, the cells were lysed and fractionated by isopycnic surcrose density gradient sedimentation. Receptor-associated radioactivity cosedimented with plasma membrane in fractions from cells kept at 4 degrees C or incubated at 37 degrees C for 2 min or less. Fractionation of cells incubated at 37 degrees C for longer times revealed that the radioactivity sedimented to lower densities coincident with Golgi markers and the site of noncovalently bound and internalized formyl-chemotactic peptide. To follow the redistribution of unoccupied receptors, human granulocytes were stimulated with 500 nM N-formyl-Met-Leu-Phe at 37 degrees C for 5 min, washed, lysed by N2 cavitation, and fractionated by rate zonal sucrose density gradient sedimentation. Compared to unstimulated controls the specific binding of N-formyl-Met-Leu-[3H]Phe decreased 76% +/- 9% in plasma membrane fractions. N-formyl-Met-Leu-[3H]Phe-binding activity associated with an intracellular pool cosedimenting with specific granules remained unchanged. Approximately 20% of the activity lost in the plasma membrane could be accounted for by a redistribution of specific N-formyl-Met-Leu-Phe binding to fractions enriched in azurophil granules. We conclude that the receptor is the carrier in the internalization of the N-formyl-chemotactic peptides to a Golgi-enriched fraction and hypothesize that after a short residency in this fraction, the receptor may dissociate from the ligand and pass onto a fraction cosedimenting with dense granules. 相似文献