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91.
92.
Brian A. Bidlingmeyer Steven A. Cohen Thomas L. Tarvin 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》1984,336(1)
A new approach to the pre-column derivatization and analysis of amino acids is described. The method is based upon formation of a phenylthiocarbamyl derivative of the amino acids. The derivatization method is rapid, efficient, sensitive, and specific for the analysis of primary and secondary amino acids in protein hydorlyzates. The liquid chromatographic system allows for the rapid, bonded-phase separation with ultraviolet detection of the common amino acids with 12-min analysis time and a 1-pmol sensitivity. 相似文献
93.
Alice H. Lin Patricia L. Ruppel Robert R. Gorman 《Prostaglandins & other lipid mediators》1984,28(6):837-849
[3H] Leukotriene B4 (LTB4) binds concentration dependency to intact human polymorophonuclear leukocytes (PMN's). The binding is saturable, reaches equilibrium in 10 min at 4°C, and is readily reversible. Mathematical modeling analysis reveals biphasic binding of [3H] LTB4 indicating two discrete populations of binding sites. The high affinity binding sites have a dissociation constant of 0.46 × 10−9M and Bmax of 1.96 × 104 sites per neutrophil; the low affinity binding sites have a dissociation constant of 541 × 10−9M and a Bmax of 45.6 × 104 sites per neutrophil. Competitive binding experiments with structural analogues of LTB4 demonstrate that the interaction between LTB4 and the binding site is stereospecific, and correlates with the relative biological activity of the analogs. At 25°C[3H] LTB4 is rapidly dissociated from the binding site and metabolized to 20-OH and 20-COOH-LTB4. Purification of neutrophils in the presence of 5-lipoxygenase inhibitors significantly increases specific [3H] LTB4 binding, suggesting that LTB4 is biosynthesized during the purification procedure. These data suggest that stereospecific binding and metabolism of LTB4 in neutrophils are tightly coupled processes. 相似文献
94.
Taenia taeniaeformis: characterization of larval metabolic products and growth of host gastric cells in vitro 总被引:1,自引:0,他引:1
Development of larvae of the cestode parasite Taenia taeniaeformis in the liver of rats induces gross hyperplasia of the gastric mucosa and excessive mucus production in the stomach without any direct contact with the stomach. Because the taeniid larvae are known to elaborate excretory-secretory (E-S) product in vivo and in vitro, the product was analyzed further, and its effects on cultured rat and dog stomach cells were investigated. In vitro E-S product contained less negatively charged glycosaminoglycan than either heparin or chondroitin sulfate, and proteins of various molecular weights. It stimulated the growth of both rat and dog stomach cells at concentrations of 3-9 micrograms protein/ml culture medium. At a concentration of 30 micrograms protein/ml culture medium, it stimulated hexosamine production in the cells up to 20 times, and multiple intracytoplasmic granules were found in both rat and dog cultured cells by light and electron microscopy. These results suggest that larval E-S product may be involved in the induction of gastric hyperplasia and hypermucus secretion. 相似文献
95.
96.
Gary L. Stiles Ruth H. Strasser Brian F. Kilpatrick Sabrina R. Taylor Robert J. Lefkowitz 《Biochimica et Biophysica Acta (BBA)/General Subjects》1984,802(3)
Photoaffinity labeling techniques have recently demonstrated that mammalian β1- and β2-adrenergic receptors reside on peptides of Mr 62 000–64 000. These receptor peptides are susceptible to endogenous metalloproteinases which produce peptides of Mr 30 000–55 000. Several proteinase inhibitors markedly attenuate this process, specifically EDTA and EGTA. In this study we investigated the functional significance of this proteolysis (and its inhibition) in the β2-adrenergic receptor-adenylate cyclase system derived from rat lung membranes. Membrane preparations containing proteolytically derived fragments of the receptor of Mr 40000–55 000 are fully functional with respect to their ability to bind β-adrenergic antagonist radioligands such as [3H]dihydroalprenolol and β-adrenergic antagonist photoaffinity reagents such as p-azido-m-[125I]iodobenzylcarazolol. They retain the ability to form a high-affinity, agonist-promoted, guanine nucleotide-sensitive complex thought to represent a ternary complex of agonist, receptor and guanine nucleotide regulatory protein. Nonetheless, after proteolysis, GTP is less able to revert this high-affinity receptor complex to one of lower affinity, and all aspects of adenylate cyclase stimulation are reduced. In addition, the functional integrity of the N protein in membranes prepared without proteinase inhibitors is reduced as assessed by reconstitution studies with the cyc[su− variant of S49 lymphoma cell membranes. These results suggest that endogenous proteolysis does not directly impair the ability of β-adrenergic receptors to either bind ligands or interact with the guanine nucleotide regulatory protein. However, they imply that endogenous proteolysis likely impairs the functionality of other components of the adenylate cyclase system, such as the nucleotide regulatory protein. 相似文献
97.
98.
A strain of Escherichia coli with a deletion of the penicillin-binding protein 6 gene (dacC) has been constructed. The properties of this strain establish that the complete lack of penicillin-binding protein 6 has no marked effect on the growth of E. coli. 相似文献
99.
Brian B. Spear 《Chromosoma》1980,77(2):193-202
The DNA in the macronucleus of the protozoan Oxytricha, unlike like that of typical eukaryotes, exists as short, gene-sized molecules. Within the macronucleus the rRNA genes are contained in molecules 7,380 nucleotide pairs in length. This rDNA has been substanially purified by selective denaturation of non-ribosomal DNA followed by Sl nuclease digestion. Results from restriction nuclease digestion and rRNA:DNA hybridization show that the rDNA is a linear, non-palindromic molecule which contains one gene each for the 19s and 25s rRNAs. A total of less than 600 base pairs of DNA lies between the 19s and 25s genes or at the 3 end of the 25s gene. The non-coding portion of the ribosomal DNA is almost entirely limited to an approximately 1,400 base pair region at the 5 end of the molecule. 相似文献
100.
M.S. Lin 《Experimental cell research》1980,127(1):179-183
The frequency of sister chromatid exchanges (SCE) in the chromosomes of the diploidy and polyploidy of Chinese hamster cells and human cells has been studied using BUdR-DAPI (bromodeoxyuridine, 4′-6-diamidino-2-phenylindol) fluorescence. The rate of SCEs per cell under constant control conditions is in proportion to the ploidy levels. In addition, the frequency of SCEs observed in a given human chromosome (nos. 1) is also directly proportional to the number of such chromosomes presented in the cells. The mean of SCEs in human chromosome numbers 1 is very similar (0.46–0.48) for diploid, triploid, and tetraploid cells. The results suggest that the rate of SCEs is a function of cellular ploidy levels. 相似文献