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61.
Phosphorus-31 nuclear magnetic resonance studies of wild-type and glycolytic pathway mutants of Saccharomyces cerevisiae. 总被引:19,自引:0,他引:19
G Navon R G Shulman T Yamane T R Eccleshall K B Lam J J Baronofsky J Marmur 《Biochemistry》1979,18(21):4487-4499
High-resolution phosphorus-31 nuclear magnetic resonance (31P NMR) spectra of wild-type and mutant strains of Saccharomyces cerevisiae were observed at a frequency of 145.7 MHz. Levels of various phosphorus metabolites were investigated upon addition of glucose under both aerobic and anaerobic conditions. Three mutant strains were isolated and their biochemical defects characterized: pfk lacked phosphofructokinase activity; pgi lacked phosphoglucose isomerase activity; and cif had no glucose catabolite repression of the fructose bisphosphatase activity. Each mutant strain was found to accumulate characteristic sugar phosphates when glucose was added to the cell suspension. In the case of the phosphofructokinase deficient mutant, the appearance of a pentose shunt metabolite was observed. 31P NMR peak assignments were made by a pH titration of the acid extract of the cells. Separate signals for terminal, penultimate, and central phosphorus atoms in intracellular polyphosphates allowed the estimation of their average molecular weight. Signals for glycero(3)phosphochline, glycero(3)phosphoserine, and glycero(3) phosphoethanolamine as well as three types of nucleotide diphosphate sugars could be observed. The intracellular pH in resting and anaerobic cells was in the range 6.5--6.8 and the level of adenosine 5'-triphosphate (ATP) low. Upon introduction of oxygen, the ATP level increased considerably and the intracellular pH reached a value of pH 7.2--7.3, irrespective of the external medium pH, indicating active proton transport in these cells. A new peak representing the inorganic phosphate of one of the cellular organelles, whose pH differed from the cytoplasmic pH, could be detected under appropriate conditions. 相似文献
62.
63.
The growth interactions amongst the blue-green algal species Anabaena oscillarioides, Microcystis aeruginosa and the green alga, Chlorella sp. were studied both in mixed cultures and in filter cultures separated by a membrane filter in the two arms of an interaction U-tube. The role of nutrients especially phosphate upon the interaction has also been studied.
Anabaena and Microcystis both inhibited the growth of Chlorella while Microcystis also inhibited the growth of Anabaena. The inhibitory effect of Microcystis was found to be dependent on high concentrations of the initial algal inocula and independent of the initial concentration of nutrients such as inorganic phosphate, indicating that the nature of the inhibition is probably due to the production of inhibitory extracellular products by Microcystis. On the other hand, the inhibitory effect of Anabaena on Chlorella is the consequence of nutrient competition with Anabaena competing more effectively for the available phosphate. 相似文献
64.
The importance of the lysophosphatidylcholine and choline moiety of bile phosphatidylcholine in lymphatic transport of fat 总被引:3,自引:0,他引:3
A luminal supply of biliary phosphatidylcholine is important in the translocation of absorbed fat into lymph and in the amount and composition of phosphatidylcholine concurrently synthesized. This study was undertaken to determine whether the effect was due to absorbed lysophosphatidylcholine, to a specific (1-palmitoyl) biliary lysophosphatidylcholine or to extra choline supplied by lysophosphatidylcholine. Rats with bile fistulae and thoracic duct lymph fistulae were given test meals of oleic acid and monoolein (molar ratio 2 : 1) infused duodenally for 8 h. Addition of choline chloride to the test meal increased lymphatic output of triglyceride and phospholipid but not to values found previously in rats with supplements of bile phosphatidylcholine or with bile ducts intact. Addition of dioleoyl phosphatidylcholine increased triglyceride and phospholipid output to values found in rats with intact bile ducts. Since dioleoyl phosphatidylcholine was as efficient as biliary phosphatidylcholine it was concluded that a luminal supply of 1-palmitoyl lysophosphatidylcholine was not essential. It seemed likely from the smaller effect of supplemented choline and from the fatty acid composition of lymph phosphatidylcholine that the essential requirement was a supply of absorbed lysophosphatidylcholine for rapid reacylation to phosphatidylcholine. 相似文献
65.
The separation of active and inactive forms of heparin. 总被引:38,自引:0,他引:38
L H Lam J E Silbert R D Rosenberg 《Biochemical and biophysical research communications》1976,69(2):570-577
Heparin has been fractionated into two distinct forms. The isolation of these species was accomplished by sucrose density gradient centrifugation of heparin mixed with antithrombin-heparin cofactor. Approximately of this mucopolysaccharide was bound to antithrombin-heparin cofactor and had potent anticoagulant activity. This component was clearly separated from the remaining of the heparin which could not form a stable complex with antithrombin-heparin cofactor and had minimal anticoagulant activity. 相似文献
66.
Alan Tin Lun Lam Valerie Ho Svetlan Vassilev Shaul Reuveny Steve Kah Weng Oh 《Cell proliferation》2022,55(8)
ObjectivesInduced pluripotent stem cells (iPSCs) generated by monolayer cultures is plagued by low efficiencies, high levels of manipulation and operator unpredictability. We have developed a platform, reprogramming, expansion, and differentiation on Microcarriers, to solve these challenges.Materials and MethodsFive sources of human somatic cells were reprogrammed, selected, expanded and differentiated in microcarriers suspension cultures.ResultsImprovement of transduction efficiencies up to 2 times was observed. Accelerated reprogramming in microcarrier cultures was 7 days faster than monolayer, providing between 30 and 50‐fold more clones to choose from fibroblasts, peripheral blood mononuclear cells, T cells and CD34+ stem cells. This was observed to be due to an earlier induction of genes (β‐catenin, E‐cadherin and EpCAM) on day 4 versus monolayer cultures which occurred on days 14 or later. Following that, faster induction and earlier stabilization of pluripotency genes occurred during the maturation phase of reprogramming. Integrated expansion without trypsinization and efficient differentiation, without embryoid bodies formation, to the three germ‐layers, cardiomyocytes and haematopoietic stem cells were further demonstrated.ConclusionsOur method can solve the inherent problems of conventional monolayer cultures. It is highly efficient, cell dissociation free, can be operated with lower labor, and allows testing of differentiation efficiency without trypsinization and generation of embryoid bodies. It is also amenable to automation for processing more samples in a small footprint, alleviating many challenges of manual monolayer selection.We have developed an allied protocol for reprogramming, selecting, expanding and differentiating human pluripotent stem cells on Microcarriers (designated as RepMC). This method allows faster reprogramming, selecting 30‐50‐fold more candidates for characterization and also allows us to find high quality candidates that differentiate to cardiomyocytes and blood lineages. Mechanistically, this method appears to accelerate the induction, maturation and stabilization phases of reprogramming. Our findings help simplify the process of deriving and expanding iPSCs for therapeutic applications, offering a robust and scalable suspension platform for large‐scale generation of clinical grade iPSCs. 相似文献
67.
W. Y. Chan T. B. Ng Joyce S. Y. Lam Jack H. Wong K. T. Chu P. H. K. Ngai S. K. Lam H. X. Wang 《Applied microbiology and biotechnology》2010,85(4):985-993
Earlier investigations disclose that some plant ribosome-inactivating proteins (RIPs) adversely affect mouse embryonic development.
In the present study, a mushroom RIP, namely lyophyllin from Lyophyllum shimeji, was isolated, partially sequenced, and its translation inhibitory activity determined. Its teratogenicity was studied by
using a technique entailing microinjection and postimplantation whole-embryo culture. It was found that embryonic abnormalities
during the period of organogenesis from E8.5 to E9.5 were induced by lyophyllin at a concentration as low as 50 μg/ml, and
when the lyophyllin concentration was raised, the number of abnormal embryos increased, the final somite number decreased,
and the abnormalities increased in severity. The affected embryonic structures included the cranial neural tube, forelimb
buds, branchial arches, and body axis, while optic and otic placodes were more resistant. Lyophyllin at a concentration higher
than 500 μg/ml also induced forebrain blisters within the cranial mesenchyme. When the abnormal embryos were examined histologically,
an increase of cell death was found to be associated with abnormal structures, indicating that cell death may be one of the
underlying causes of teratogenicity of the mushroom RIP. This constitutes the first report on the teratogenicity of a mushroom
RIP. 相似文献
68.
J M De Bakker M E Kammüller E S Muller A W Lam W Seinen N Bloksma 《Virchows Archiv. B, Cell pathology including molecular pathology》1990,58(4):279-287
Changes in the popliteal lymph node (PLN) in mice evoked by a local graft-versus-host (GVH) reaction and by a single injection of various agents into the hind footpad were compared. The drug diphenylhydantoin induced similar weight changes in time as the GVH reaction. More vigorous and protracted reactions were induced by the drug nitrofurantoin and the contact sensitizer dinitrochlorobenzene, whereas the antigens lipopolysaccharide and sheep erythrocytes caused very moderate and short-lasting weight changes. Alterations of lymph node architecture upon injection of diphenylhydantoin resembled those observed during the GVH response. Some quantitative and qualitative differences were noted for nitrofurantoin, but clearly deviant morphological alterations were seen in response to lipopolysaccharide and sheep erythrocytes. The PLN reaction to dinitrochlorobenzene had features of both the GVH reaction and the antigen-induced responses. These findings support the concept that some drugs and chemicals may induce or exacerbate lymphoproliferative disorders by GVH-like mechanisms. 相似文献
69.
Kovanen PE Rosenwald A Fu J Hurt EM Lam LT Giltnane JM Wright G Staudt LM Leonard WJ 《The Journal of biological chemistry》2003,278(7):5205-5213
Interleukin (IL)-2, IL-4, IL-7, IL-9, IL-15, and IL-21 form a family of cytokines based on their sharing the common cytokine receptor gamma chain, gamma(c), which is mutated in X-linked severe combined immunodeficiency (SCID). As a step toward further elucidating the mechanism of action of these cytokines in T-cell biology, we compared the gene expression profiles of IL-2, IL-4, IL-7, and IL-15 in T cells using cDNA microarrays. IL-2, IL-7, and IL-15 each induced a highly similar set of genes, whereas IL-4 induced distinct genes correlating with differential STAT protein activation by this cytokine. One gene induced by IL-2, IL-7, and IL-15 but not IL-4 was dual-specificity phosphatase 5 (DUSP5). In IL-2-dependent CTLL-2 cells, we show that IL-2-induced ERK-1/2 activity was inhibited by wild type DUSP5 but markedly increased by an inactive form of DUSP5, suggesting a negative feedback role for DUSP5 in IL-2 signaling. Our findings provide insights into the shared versus distinctive actions by different members of the gamma(c) family of cytokines. Moreover, we have identified a DUSP5-dependent negative regulatory pathway for MAPK activity in T cells. 相似文献
70.
Differences in genotypes of Helicobacter pylori from different human populations 总被引:12,自引:0,他引:12 下载免费PDF全文
Kersulyte D Mukhopadhyay AK Velapatiño B Su W Pan Z Garcia C Hernandez V Valdez Y Mistry RS Gilman RH Yuan Y Gao H Alarcón T López-Brea M Balakrish Nair G Chowdhury A Datta S Shirai M Nakazawa T Ally R Segal I Wong BC Lam SK Olfat FO Borén T Engstrand L Torres O Schneider R Thomas JE Czinn S Berg DE 《Journal of bacteriology》2000,182(11):3210-3218
DNA motifs at several informative loci in more than 500 strains of Helicobacter pylori from five continents were studied by PCR and sequencing to gain insights into the evolution of this gastric pathogen. Five types of deletion, insertion, and substitution motifs were found at the right end of the H. pylori cag pathogenicity island. Of the three most common motifs, type I predominated in Spaniards, native Peruvians, and Guatemalan Ladinos (mixed Amerindian-European ancestry) and also in native Africans and U.S. residents; type II predominated among Japanese and Chinese; and type III predominated in Indians from Calcutta. Sequences in the cagA gene and in vacAm1 type alleles of the vacuolating cytotoxin gene (vacA) of strains from native Peruvians were also more like those from Spaniards than those from Asians. These indications of relatedness of Latin American and Spanish strains, despite the closer genetic relatedness of Amerindian and Asian people themselves, lead us to suggest that H. pylori may have been brought to the New World by European conquerors and colonists about 500 years ago. This thinking, in turn, suggests that H. pylori infection might have become widespread in people quite recently in human evolution. 相似文献