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991.
Arnold Trehub 《Journal of theoretical biology》1979,81(3):569-576
An adaptive neuronal network (synaptic matrix) was simulated. After learning a number of randomly generated scenes, the network was tested for associative sequential recall in a stimulus-bound mode and in an image-bound mode. It is demonstrated that neuronal mechanisms of this kind can exhibit orderliness or looseness of associative response suggestive of human recall behavior. 相似文献
992.
Arnold van Huis Keith Cressman & Joyce I. Magor 《Entomologia Experimentalis et Applicata》2007,122(3):191-214
Solitarious desert locusts, Schistocerca gregaria (Forskål) (Orthoptera: Acrididae), inhabit the central, arid, and semi‐arid parts of the species’ invasion area in Africa, the Middle East, and South‐West Asia. Their annual migration circuit takes them downwind to breed sequentially where winter, spring, and summer rains fall. In many years, sparse and erratic seasonal rains support phase change and local outbreaks at only a few sites. Less frequently, seasonal rains are widespread, frequent, heavy, and long lasting, and many contemporaneous outbreaks occur. When such seasonal rains fall sequentially, populations develop into an upsurge and eventually into a plague unless checked by drought, migration to hostile habitats, or effective control. Increases in the proportion of gregarious populations as the plague develops alter the effectiveness of control. As an upsurge starts, only a minority of locusts is aggregated into treatable targets and spraying them leaves sufficient unsprayed individuals to continue the upsurge. Spraying all individuals scattered within an entire infested zone is arguably both financially and environmentally unacceptable. More of the population gregarizes and forms sprayable targets after each successive season of good rains and successful breeding. Eventually, unless the rains fail, the entire upsurge population becomes aggregated at high densities so that the infested area diminishes and a plague begins. These populations must continue to increase numerically and spread geographically to achieve peak plague levels, a stage last reached in the 1950s. Effective control, aided by poor rains, accompanied each subsequent late upsurge and early plague stage and all declined rapidly. The control strategy aims to reduce populations to prevent plagues and damage to crops and grazing. Differing opinions on the optimum stage to interrupt pre‐plague breeding sequences are reviewed. 相似文献
993.
Previous studies indicate that ATP formation by the electron transport chain is impaired in sepsis. However, it is not known whether sepsis affects the mitochondrial ATP transport system. We hypothesized that sepsis inactivates the mitochondrial creatine kinase (MtCK)-high energy phosphate transport system. To examine this issue, we assessed the effects of endotoxin administration on mitochondrial membrane-bound creatine kinase, an important trans-mitochondrial ATP transport system. Diaphragms and hearts were isolated from control (n = 12) and endotoxin-treated (8 mg.kg(-1).day(-1); n = 13) rats after pentobarbital anesthesia. We isolated mitochondria using techniques that allow evaluation of the functional coupling of mitochondrial creatine kinase MtCK activity to oxidative phosphorylation. MtCK functional activity was established by 1) determining ATP/creatine-stimulated oxygen consumption and 2) assessing total creatine kinase activity in mitochondria using an enzyme-linked assay. We examined MtCK protein content using Western blots. Endotoxin markedly reduced diaphragm and cardiac MtCK activity, as determined both by ATP/creatine-stimulated oxygen consumption and by the enzyme-linked assay (e.g., ATP/creatine-stimulated mitochondrial respiration was 173.8 +/- 7.3, 60.5 +/- 9.3, 210.7 +/- 18.9, was 67.9 +/- 7.3 natoms O.min(-1).mg(-1) in diaphragm control, diaphragm septic, cardiac control, and cardiac septic samples, respectively; P < 0.001 for each tissue comparison). Endotoxin also reduced diaphragm and cardiac MtCK protein levels (e.g., protein levels declined by 39.5% in diaphragm mitochondria and by 44.2% in cardiac mitochondria; P < 0.001 and P = 0.009, respectively, comparing sepsis to control conditions). Our data indicate that endotoxin markedly impairs the MtCK-ATP transporter system; this phenomenon may have significant effects on diaphragm and cardiac function. 相似文献
994.
995.
996.
Mikala Gabor Klöckners Udo Varadi Maria Eisfeld Jörg Schwartz Arnold Varadi Gyula 《Molecular and cellular biochemistry》1998,185(1-2):95-109
The involvement of cAMP-dependent phosphorylation sites in establishing the basal activity of cardiac L-type Ca2+ channels was studied in HEK 293 cells transiently cotransfected with mutants of the human cardiac 1 and accessory subunits. Systematic individual or combined elimination of high consensus protein kinase A (PKA) sites, by serine to alanine substitutions at the amino and carboxyl termini of the 1 subunit, resulted in Ca2+ channel currents indistinguishable from those of wild type channels. Dihydropyridine (DHP)-binding characteristics were also unaltered. To explore the possible involvement of nonconsensus sites, deletion mutants were used. Carboxyl-terminal truncations of the 1 subunit distal to residue 1597 resulted in increased channel expression and current amplitudes. Modulation of PKA activity in cells transfected with the wild type channel or any of the mutants did not alter Ca2+ channel functions suggesting that cardiac Ca2+ channels expressed in these cells behave, in terms of lack of PKA control, like Ca2+ channels of smooth muscle cells. 相似文献
997.
Kai K. Eberle K. E. Zinsmaier Sigrid Buchner M. Gruhn Mario Jenni Christine Arnold Christian Leibold Dietmar Reisch N. Walter Ernst Hafen A. Hofbauer Gert O. Pflugfelder E. Buchner 《Cell and tissue research》1998,294(2):203-217
The “cysteine string protein” (CSP) genes of higher eukaryotes code for a novel family of proteins characterized by a “J” domain and an unusual cysteine-rich region. Previous studies had localized the proteins in neuropil and synaptic terminals of larval and adult Drosophila and linked the temperature-sensitive paralysis of the mutants described here to conditional failure of synaptic transmission. We now use the null mutants as negative controls in order to reliably detect even low concentrations of CSPs by immunohistochemistry, employing three monoclonal antibodies. In wild-type flies high levels of cysteine string proteins are found not only in apparently all synaptic terminals of the embryonic, larval, and adult nervous systems, but also in the “tall cells” of the cardia, in the follicle cells of the ovary, in specific structures of the female spermatheca, and in the male testis and ejaculatory bulb. In addition, low levels of CSPs appear to be present in all tissues examined, including neuronal perikarya, axons, muscles, Malpighian tubules, and salivary glands. Western blots of isolated tissues demonstrate that of the four isoforms expressed in heads only the largest is found in non-neural organs. The wide expression of CSPs suggests that at least some of the various phenotypes of the null mutants observed at permissive temperatures, such as delayed development, short adult lifespan, modified electroretinogram, and optomotor behavior, may be caused by the lack of CSPs outside synaptic terminals. 相似文献
998.
A dextranase (EC 3.2.1.11) was purified and characterized from the IP-29 strain of Sporothrix schenckii, a dimorphic pathogenic fungus. Growing cells secreted the enzyme into a standard culture medium (20 °C) that supports the
mycelial phase. Soluble bacterial dextrans substituted for glucose as substrate with a small decrease in cellular yield but
a tenfold increase in the production of dextranase. This enzyme is a monomeric protein with a molecular mass of 79 kDa, a
pH optimum of 5.0, and an action pattern against a soluble 170-kDa bacterial dextran that leads to a final mixture of glucose
(38%), isomaltose (38%), and branched oligosaccharides (24%). In the presence of 200 mM sodium acetate buffer (pH 5.0), the
K
m for soluble dextran was 0.067 ± 0.003% (w/v). Salts of Hg2+, (UO2)2+, Pb2+, Cu2+, and Zn2+ inhibited by affecting both V
max and K
m. The enzyme was most stable between pH values of 4.50 and 4.75, where the half-life at 55 °C was 18 min and the energy of
activation for heat denaturation was 99 kcal/mol. S. schenckii dextranase catalyzed the degradation of cross-linked dextran chains in Sephadex G-50 to G-200, and the latter was a good
substrate for cell growth at 20 °C. Highly cross-linked grades (i.e., G-10 and G-25) were refractory to hydrolysis. Most strains
of S. schenckii from Europe and North America tested positive for dextranase when grown at 20 °C. All of these isolates grew on glucose at
35 °C, a condition that is typically associated with the yeast phase, but they did not express dextranase and were incapable
of using dextran as a carbon source at the higher temperature.
Received: 29 December 1997 / Accepted: 4 March 1998 相似文献
999.
I. Perrault Sophie Châtelin Vanessa Nancy Jean-Michel Rozet Sylvie Gerber Imad Ghazi Eric Souied Jean-Louis Dufier Arnold Munnich Jean de Gunzburg Josseline Kaplan 《Human genetics》1998,102(3):322-326
Leber’s congenital amaurosis (LCA) is the earliest and most severe of all inherited retinal dystrophies. Recently, we mapped
an LCA gene to chromosome 17p13.1 (LCA1) and ascribed the disease to mutations of the retinal guanylate cyclase (ret GC) gene
in a subset of families of North African ancestry. Owing to the genetic heterogeneity of LCA and considering that LCA1 results
from an impaired production of cGMP in the retina (with permanent closure of cGMP-gated cation channels), we hypothesized
that the activation of the cGMP phosphodiesterase (PDE) could trigger the disease by lowering the intracellular cGMP level
in the retina. The rod and cone cGMP-PDE inhibitory subunits were regarded therefore as candidate genes in LCA. Here, we report
the exclusion of five rod and cone cGMP-PDE subunits in LCA families unlinked to chromosome 17p13.
Received: 7 April 1997 / Accepted: 3 November 1997 相似文献
1000.
Die Pyrenoidstärke von Mesotaenium caldariorum enthält Chlorophyll mit Extinktionsmaxima bei λ = 435 und 675 nm. Zugabe von 5-Aminolävulinsäure (ALA, 10?3 M/L) erhöht die Chlorophyllkonzentration in der Pyrenoidstärke und mit zeitlicher Verzögerung auch im Chloroplastenraum. Am Pyrenoid tritt das Konzentrationsmaximum neun Stunden nach Zugabe der ALA auf, im Chloroplastenraum erst nach 60 Stunden. Nach Behandlung mit 14C-ALA ist Radioaktivität mikroautoradiographisch zunächst nur am Pyrenoid (Maximum nach neun Stunden) nachzuweisen, im Chloroplastenraum erst zeitlich verzögert (Maximum nach 60 Stunden). 84 Stunden nach Zugabe der ALA hat sich die Radioaktivität gleichmäßig über den Chloroplasten verteilt. 相似文献