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101.
Angela Krämer Regina Haars Rainer Kabisch Hans Will Friedlinde A. Bautz Ekkehard K. F. Bautz 《Molecular & general genetics : MGG》1980,180(1):193-199
Summary Monoclonal antibodies were raised against purified RNA polymerase II (or B) from Drosophila melanogaster. The antibody produced by one hybridoma cell clone was found to be directed against the two large subunits of the enzyme. The absence of antibodies directed against proteins possibly contaminating the antigens used for immunization allowed us to identify RNA polymerase unequivocally in interbands and puffs of polytene chromosomes. Within a single heat shock puff (87C1) RNA polymerase was found to be clustered in two separate areas suggesting two distint regions of RNA polymerase activity in this puff.Abbreviations FITC
fluorescein isothiocyanate
- PAGE
polyacrylamide gel electrophoresis
- PBS
phosphate buffered saline
- SDS
sodium dodecyl sulfate
- Enzyme
DNA-dependent RNA polymerase or nucleotide-triphosphate
- RNA
nucleotidyltransferase (EC 2.7.7.6) 相似文献
102.
JoséLuis Avila Antonio Bretaña María Argelia Casanova Angela Avila Francisco Rodríguez 《Experimental parasitology》1979,48(1):27-35
A liquid medium was developed for the continuous cultivation of Trypanosoma cruzi. Among the several highly purified macromolecules tested only bovine liver catalase, horseradish peroxidase, lactoperoxidase, and bovine hemoglobin supported the continuous growth, at high yield, of mice-virulent Trypanosoma cruzi; other hemoproteins were inactive. Bovine liver catalase showed optimal Trypanosoma cruzi growth-promoting activity, parasites reaching 20 × 106 parasites/ml (95% epimastigotes) at about 10 days in most of the 45 subpassages to date. Furthermore, this protein in the incubation medium provided all the amino acid requirements of actively growing parasites, thus eliminating the need for exogeneous free amino acids. Additional experiments revealed that the hemoprotein's growth-promoting activity was independent of any enzymatic activity and that reconstituting the exact protein composition by means of exogeneous amino acids did not support parasite multiplication, suggesting the importance of the primary structure of the active proteins for growth-promoting activity. These active macromolecules supported the multiplication of five different strains of Trypanosoma cruzi, but did not support Leishmania brasiliensis or Leishmania mexicana proliferation, suggesting species specificity. 相似文献
103.
104.
Guy G.S. Dutton Keith L. Mackie Angela V. Savage Mary D. Stephenson 《Carbohydrate research》1978,66(1):125-131
Klebsiella K23 capsular polysaccharide has been investigated by the techniques of hydrolysis, methylation, Smith degradation-periodate oxidation, and base-catalysed degradation, either on the original or the carboxyl-reduced polysaccharide. The structure was found to consist of a tetrasaccharide repeating-unit, as shown below. The anomeric configurations of the sugar residues were determined by 1H-and 13C-n.m.r. spectroscopy on the original and degraded polysaccharides. 相似文献
105.
Angela M. Longo 《Developmental biology》1978,65(2):260-270
We have analyzed the incorporation of radioactive amino acids by rat C6 glioma cells into material precipitable with anti-β-nerve growth factor (NGF). We show that amino acids are incorporated into a protein the size of β-NGF which is immunologically related to NGF and which has peptides similar to those of mouse β-NGF. Several lines of evidence obtained in this study support the hypothesis that NGF is produced by the proteolytic cleavage of a higher molecular weight precursor. This evidence includes kinetic studies, demonstration of higher molecular weight material (24,000) immunologically related to NGF, and in vitro processing of the 24,000 MW protein to material of the approximate size of β-NGF. 相似文献
106.
Summary Evidence is presented in support of the hypothesis that the contents of digestive vacuoles in refed starvedTetrahymena pyriformis GL-9 are egested from the cell in approximately the sequence of their order of formation. The investigations involved measurements of the rates of disappearance of digestive vacuoles from the cells and the subsequent appearance of egested globules in the surrounding medium using both cultures and individual cells. The cells were first fed peptone and latex particles for a period and then this type of vacuole formation was suppressed by the addition of excess carmine particles (or the process was repeated with the particles in reverse order). Thus two types of morphologically distinct digestive vacuoles could be produced and observed microscopically. These observations suggest that the temporal nature of the movement of the digestive vacuoles through the cell result in the temporal nature of egestion and that no selective mechanism occurs at egestion. Thus digestive vacuoles are thought to pass through the cell from cytopharynx to cytoproct in approximately the order formed and at approximately constant rate. Under conditions of excess nutrients, where the cells become filled with digestive vacuoles, they seem to be able to maintain an approximately uniform number of digestive vacuoles within themselves by maintaining approximately constant and equal rates of vacuole formation and egestion. The maximum rates of latex or carmine vacuole formation or egestion found in single cells were approximately 0.3–0.4 vacuoles per cell per minute. The results are discussed. 相似文献
107.
Citrate lyase (EC 4.1.3.6) was purified 38-fold from cell-free extracts of Streptococcus diacetilactis. The enzyme was homogeneous in analytical ultracentrifugation and polyacrylamide gel electrophoresis The final enzyme preparation contained acetate: HS-citrate lyase ligase—an acetylating enzyme which converts inactive HS-citrate lyase into enzymatically active acetyl-S-citrate lyase. This enzyme activity was purified 25-fold over the crude extract and seemed to be associated with citrate lyase. Partially purified citrate lyase from Leuconostoc citrovorum contained also its acetylating enzyme. Purified citrate lyases from Klebsiella aerogenes and Rhodopseudomonas gelatinosa were devoid of acetylating enzyme activity. The HS-form of citrate lyase from S. diacetilactis was completely acetylated and hence activated by incubation with ATP and acetate for 25 min at 25° C. The enzyme did not acetylate the HS-lyases from R. gelatinosa and K. aerogenes. In contrast to the citrate lyases from R. gelatinosa and K. aerogenes the enzymes from S. diacetilactis and L. citrovorum showed onlya very weak reaction inactivation. It is assumed that this is due to the association of the acetylating enzymes with these lyases. 相似文献
108.
Twenty wild caught Mouse opossums Marmosa robinsoni Bangs 1898 formed the basis of a laboratory colony which was maintained at the Brookfield Zoo during 1971–3. Approximately 250 young including 3rd-generation descendants were produced.
M. robinsoni is polyoestrous with a mean cycle length of 25.5±0.5 days. Vaginal oestrus, which normally lasts three days, is accompanied by a pronounced cycle of cornification and mucification. During this period large numbers of desquamated epithelial cells and mucus are found in the urine. Females are sexually receptive 24 hours before cornified cells first appear in the urine and receptivity lasts two to four days. Fertile copulation takes place throughout this period. Ovulation is spontaneous and occurs late in oestrus. The mean number of corpora lutea recorded was 19.8±0.9 ( n =23).
Anovular cycles, associated with atresia of mature Graafian follicles, were found in approximately 25% of the females. The sterile cycles, which had a mean length of 15.6±0.7 days, were not always accompanied by a behavioural oestrus. Observations on the behaviour of introduced pairs provided direct evidence of sexual incompatibility. Sexual incompatibility was found to have been responsible for at least 10% of the unsuccessful pairings recorded during the study.
There were no indications in the Brookfield colony of the decline in productivity among laboratory-bred animals reported in other Marmosa colonies. Litter-sizes and litter-rates in the F1 and F2 generations did not differ from those in the wild-caught generation. However, the fact that only one out of three pairings produced young suggests that productivity in the colony was lower than in the wild. The cause of this low productivity was not established. 相似文献
M. robinsoni is polyoestrous with a mean cycle length of 25.5±0.5 days. Vaginal oestrus, which normally lasts three days, is accompanied by a pronounced cycle of cornification and mucification. During this period large numbers of desquamated epithelial cells and mucus are found in the urine. Females are sexually receptive 24 hours before cornified cells first appear in the urine and receptivity lasts two to four days. Fertile copulation takes place throughout this period. Ovulation is spontaneous and occurs late in oestrus. The mean number of corpora lutea recorded was 19.8±0.9 ( n =23).
Anovular cycles, associated with atresia of mature Graafian follicles, were found in approximately 25% of the females. The sterile cycles, which had a mean length of 15.6±0.7 days, were not always accompanied by a behavioural oestrus. Observations on the behaviour of introduced pairs provided direct evidence of sexual incompatibility. Sexual incompatibility was found to have been responsible for at least 10% of the unsuccessful pairings recorded during the study.
There were no indications in the Brookfield colony of the decline in productivity among laboratory-bred animals reported in other Marmosa colonies. Litter-sizes and litter-rates in the F
109.
110.
Different patterns of lignified cell walls are associated with diverse functions in a variety of plant tissues. These functions rely on the stiffness and hydrophobicity that lignin polymers impart to the cell wall. The precise pattern of subcellular lignin deposition is critical for the structure–function relationship in each lignified cell type. Here, we describe the role of xylem vessels as water pipes, Casparian strips as apoplastic barriers, and the role of asymmetrically lignified endocarp b cells in exploding seed pods. We highlight similarities and differences in the genetic mechanisms underpinning local lignin deposition in these diverse cell types. By bringing together examples from different developmental contexts and different plant species, we propose that comparative approaches can benefit our understanding of lignin patterning mechanisms.Diverse lignin patterns underpin distinct functions in different plant tissues. 相似文献