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891.
Summary The role of nerve cell density in the regulation of bud production in hydra was examined. Animals with different rates of bud production were produced by altering the temperature, population density and illumination of their cultures. When the distribution of cell types was examined in animals with different rates of bud production, the density of nerve cells in those animals was found to be correlated with their rate of bud production. Transfer of animals from one environment to another resulted in immediate changes in the rate of differentiation of large interstitial cells into nerve cells. This suggests that the density of nerve cells may play a role in regulating the rate of bud production in hydra. 相似文献
892.
R. J. J. Kanoza D. M. Brunette A. D. Purdon J. Sodek 《In vitro cellular & developmental biology. Plant》1978,14(9):746-753
Summary An operational criterion for the identification and isolation of epithelial-like (E) cells, based on their ability to cover
and protect, a collagen gel from the action of collagenase, has been developed. The E cells isolated by this collagenase-separation
technique (CST) exhibited the ultrastructural features, including desmosomes and abundant tonofilaments, that are considered
characteristic of this cell type. Unlike confluent cultures of fibroblast-like (F) cells, E cells were not found to have large
external transformation-sensitive (LETS) protein on their surface membranes. The CST provides a nondestructive, and efficient
means of identifying and isolating E cells from mixed populations. 相似文献
893.
Poiley J. A. Schuman R. F. Pienta R. J. 《In vitro cellular & developmental biology. Plant》1978,14(5):405-412
Summary Normal human embryonic cells were subcultured for over 100 population doublings without modification of the basic medium.
The cells were evaluated for growth rate, confluent density, chromosome stability, growth in soft agar, ability to hydrolyze
casein and tumorigenicity. The cells possessed the characteristics of normal cells. The batch of serum used to supplement
the medium was found to be of primary importance in the long-term growth of this cell culture.
Research sponsored by the National Cancer Institute under Contract No. NO1-CO-25423 with Litton Bionetics, Inc. 相似文献
894.
Regulation of the synthesis of human chorionic gonadotropin by strains of HeLa cells in culture 总被引:2,自引:0,他引:2
Janice Yang Chou 《In vitro cellular & developmental biology. Plant》1978,14(9):775-778
Summary Thirty-seven strains of HeLa cells were examined for their ability to synthesize human chorionic gonadotropin (hCG) and its
alpha subunit (hCG-α) in culture. Synthesis of hCG-α and hCG also was investigated in the presence of sodium butyrate and
5-bromo-2′-deoxyuridine (BrdUrd). All HeLa strains synthesized hCG-α in culture. Sodium butyrate increased the synthesis of
hCG-α in all HeLa cells; BrdUrd increased synthesis in 32 of the 37 strains examined. Although few HeLa strains synthesized
hCG in the absence of inducers, hCG was detected in most strains in the presence of sodium butyrate. The synthesis of hCG
and its alpha subunit is, therefore, a stable genetic characteristics of HeLa cells.
Certain preparations of hCG and its subunits were generously provided through the Center for Population Research of the National
Institute of Child Health and Human Development, NIH. 相似文献
895.
Summary A cell cycle analysis of theTrichoplusia ni (TN-368) insect cell line is described. By means of autoradiography and percent labeled metaphase data, the cell cycle parameters
were determined to be as follows: S, 4.5 hr; G2, 8.5 hr; M, 0.5 hr; G1, 1.0 hr; the total cell time being 14.5 hr. A synchronization procedure using 50mm thymidine in a double block procedure was used to provide a method of obtaining a large number of cells in particular cell
cycle phases, especially S and G2.
This work was supported in part by U.S. Environmental Protection Agency Grant R-802516. 相似文献
896.
R. S. PHILLIPS R. J. M. WILSON G. PASVOLS 《The Journal of eukaryotic microbiology》1978,25(3):394-398
SYNOPSIS. Gametocytes differentiated from ring-stage parasites in microcultures of human blood infected with Plasmodium falciparum. Immature gametocytes could be distinguished morphologically from late asexual trophozoites after ~ 40 h of culture. Differentiation into crescentic forms took several days and the incorporation of [3H]-isoleucine by developing gametocytes was demonstrated. About 1% of red cells contained gametocytes at the maximum densities attained. Differentiation of gametocytes occurred either directly from rings placed in culture or from the progeny of subsequent cycles of schizogony and invasion in vitro. The latter occurrence was confirmed by the development of gametocytes in marker fetal red cells added to cultures, although fetal red cells provide a less favorable environment than those with HbA for growth of the parasites. 相似文献
897.
B.A. Jakschik L.H. Lee G. Shuffer C.W. Parker 《Prostaglandins & other lipid mediators》1978,16(5):733-748
Rat basophilic leukemia (RBL-1) cells metabolized arachidonic acid through more than one enzymatic pathway. The major cyclooxygenase product was prostaglandin (PG) D2 as established by chromatographic and chemical behavior and the effect on platelet aggregation. PGD2 formation from exogenous arachidonic acid was inhibited by indomethacin, 1 μg/ml. RBL-1 incubated with exogenous arachidonic acid also formed SRS-A the synthesis of which was not inhibited by indomethacin. However, the SRS-A activity was blocked by the specific receptor antagonist FPL 55712. [14C]arachidonic acid was effectively incorporated into the phospholipids of RBL-1 cells. Challenge of such prelabelled cells or unlabelled cells with A 23187 caused release of PGD2, SRS-A and another presently unidentified product. However, with A 23187 as a stimulus, the RBL-1 cyclo-oxygenase could not be blocked by low concentrations of indomethacin. This work further substantiates our earlier findings that SRS-A formed from arachidontic acid is not a cyclooxegenase product. 相似文献
898.
The larval midgut of the silkmoth Hyalophora cecropia was examined using scanning electron microscopy. Goblet cells were observed to contain within their cavities a matrix plug. This matrix material was extruded onto the lumen side of the epithelium when the tissue was stretched. The rôle of this matrix material in maintenance of the capacity of the midgut to transport ions in vivo and in vitro is discussed. 相似文献
899.
Ade–H and ade–I are two auxotrophic mutants of Chinese hamster ovary (CHO-K1) cells which specifically require adenine as the purine source to grow. The enzymatic defects of these mutants were examined in cell-free extracts. It was found that ade–H did not have any detectable adenylosuccinate synthetase activity and ade–I was defective in the adenylosuccinate lyase enzyme. The relevance of adenine-requiring mutants to the study of the regulation of purine metabolism in mammalian cells is discussed.This work was supported by research grants from the National Institute of Aging (AG00029) and the National Foundation, March of Dimes (1-423), and by a contract from the Center for Toxicological Research, Food and Drug Administration (72-213). David Patterson is a recipient of a Research Career Development Award from the National Institute of Arthritis, Metabolic and Digestive Diseases (AM00044).Contribution (No. 218) from the Eleanor Roosevelt Institute for Cancer Research. 相似文献
900.
C. K. K. H. YUEN B. DEHGAN 《Botanical journal of the Linnean Society. Linnean Society of London》1982,85(4):283-296
The leaf epidermis of 14 species ofCodonanthe and 10 species of Nematanthus has been examined. Species of Codonanthe section Codonanthe are geographically restricted to south-eastern Brazil, and are diploid. They possess multicellular-uniseriate nonglandular trichomes, glandular trichomes with a four-celled head and a short body, anisocytic stomata and lack extrafloral nectaries. Species of Codonanthe section Spathuliformae and Codonanthe subgenus Codonanthella are distributed from southern Mexico through Central America to north-western South America and are tetraploid. They possess unicellular non-glandular trichomes (except C. caribaea), glandular trichomes with a two-celled head (except C. caribaea) and a short body, anisocytic stomata and extrafloral nectaries (except C. caribaea). All Nematanthus species are distributed in south-eastern Brazil and are diploid (N=8). Six species of Nematanthus consistently have multicellular-uniseriate nonglandular trichomes, glandular trichomes with a four-celled head and a short (unicellular) or long (multicellular) body, anisocytic stomata and lack extrafloral nectaries. Four species of Nematanthus have multicellular-uniseriate non-glandular trichomes, glandular trichomes with a head of more than four cells and a short body, anisocytic and helicocytic stomata and lack extrafloral nectaries. 相似文献