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81.
Jia-Ling Chou Zhi-Xiang Shen Irene J. Tan Robert L. Stolfi Daniel S. Martin Steven H. Dikman Samuel Waxman 《Experimental cell research》1990,186(2)
Cells from autochthonous mouse mammary carcinomas which display estrogen-independent growth vivo were studied for their hormonal responses in primary culture. A culture system employing insulin-supplemented, serum-free medium and basement membrane Matrigel as a substratum was used to cultivate tumor cells. The cells did not exhibit in vitro estrogenor prolactin-dependent growth. Primary tumors still displayed a constitutional expression of α-, β-, and γ-casein mRNAs. These messages were dramatically reduced during the culture period. However, seven to eightfold increases in α- and β-casein mRNAs were inducible in the 5-day cultures by treatment with prolactin and hydrocortisone. If the hormones were present through a 2-week culture period, the levels of α-, β-, and γ-casein mRNAs in the cells were maintained and displayed in a time-dependent increase with a peak at 10–14 days. The accumulation of β-casein mRNA in vitro did not require DNA synthesis. Administration of prolactin directly into the growing tumors in vivo could also enhance β-casein mRNA levels in the tumor cells. Morphological studies of the cells cultured in the presence of prolactin and hydrocortisone did not reveal visible changes compared with those without hormonal treatment. Transplantation of tumor cells cultured in the presence or absence of hormones resulted in the development of tumors in mice at approximately the same time. The current studies suggest that the autochthonous mammary tumor cells, independent of estrogen for cell growth, were still inducible for casein gene expression in vitro and in vivo by appropriate hormones. The induction and maintenance of casein messages by a single hormonal treatment did not appear to correlate with morphology and DNA synthesis of cells in vitro or with tumor-producing capacities in vivo. 相似文献
82.
Expression and regulation of UDP-glucuronate: neolactotetraosylceramide glucuronyltransferase in the nervous system 总被引:3,自引:0,他引:3
Sulfoglucuronyl glycolipids (SGGLs) are temporally and spatially regulated molecules present in the nervous system during its development. The characteristics of the rat brain enzyme glucuronyltransferase involved in the biosynthesis of SGGLs have been described. The enzyme catalyzes the transfer of glucuronic acid (GlcA) from UDP-GlcA to terminal galactose of the neolacto (type 2) series of glycolipids to form beta 1-3-linked glucuronyl neolacto glycolipids. The enzyme was highly specific for the neolacto series of acceptor glycolipids, neolactotetraosylceramide (nLcOse4Cer), neolactohexaosylceramide (nLcOse6-Cer), and neolactooctaosylceramide (nLcOse8Cer) and was different from the drug-inducible phenol:GlcA transferase. Considerable activity of GlcA transferase was present in the adult rat cerebral cortex, even though SGGLs almost completely disappeared from the cortex by postnatal day 15. In the cerebellum, although levels of SGGLs increased with development, the specific activity of GlcA transferase declined. The results indicated that GlcA transferase was not a regulatory enzyme controlling the expression of SGGLs. Measurements of the levels of nLcOse4Cer and nLcOse6Cer in these neural tissues indicated that the availability of these precursors may regulate the differential expression of SGGLs seen previously. GlcA transferase was significantly reduced in the cerebellar Purkinje cell degenerating murine mutant (pcd/pcd), which is consistent with the loss of SGGLs in the cerebellum of this mutant and specific association of these glycolipids with Purkinje cells. 相似文献
83.
The regulation of intermediate filament reorganization in mitosis. p34cdc2 phosphorylates vimentin at a unique N-terminal site 总被引:7,自引:0,他引:7
The disassembly of vimentin-containing intermediate filament (IF) networks during mitosis in BHK-21 cells is accompanied by increased phosphorylation of vimentin (Chou, Y.-H., Rosevear, E., and Goldman, R. D. (1989) Proc. Natl. Acad. Sci. U. S. A. 86, 1885-1889). We have recently identified p34cdc2 as the catalytic subunit of one of the two endogenous vimentin kinases in mitotic baby hamster kidney cells (Chou, Y.-H., Bischoff, J. R., Beach, D., and Goldman, R. D. (1990) Cell 62, 1063-1071). To begin to characterize the biochemical basis of the p34cdc2-mediated IF disassembly process, we have purified and sequenced the 32P-labeled tryptic peptides derived from in vitro-phosphorylated vimentin. The results demonstrate that Ser-55, in the N-terminal non-alpha-helical domain of vimentin, is the most favored phosphorylation site. This finding supports the idea that the N-terminal domain of type III IF protein plays a crucial role in regulating IF structure and supramolecular organization. 相似文献
84.
Composition and Metabolism of Gangliosides in Rat Peripheral Nervous System During Development 总被引:3,自引:9,他引:3
Abstract: Ganglioside composition of rat trigeminal nerve was studied during development in order to understand the changes that occur as a result of cellular differentiation in the nerve. The ganglioside composition of the trigeminal nerve was entirely different from that of brain. The major gangliosides in adult trigeminal nerve were GM3, GD3, and LM1 (sialosyl-lactoneotetraosylceramide or sialosylparagloboside). The structure of LM1 and other gangliosides was established by enzymatic degradation and by analysis of the products of acid hydrolysis. At 2 days after birth, when the Schwann cells were immature, GM3 and GD3 were the major gangliosides in the nerve, 50 and 18 mol %, respectively. As the nerve developed and Schwann cells proliferated and myelinated the axons, the mol % of GM3 and GD3 reduced and that of LM1 steadily increased. Polysialogangliosides did not change drastically with nerve development. The rate of deposition of LM1 in the nerve with age was very similar to that of myelin marker lipids, cerebrosides, and sulfatides; thus, deposition appears to be localized mainly in the rat nerve myelin. LM1 also had long-chain fatty acids 22:0 and 24:0, which are not usually found in CNS gangliosides. The ganglioside pattern of the rat trigeminal nerve was very similar to that of rat sciatic nerve, but was different from that of rabbit and chicken sciatic nerve. The activity of the two key enzymes involved in the metabolism of GM3, viz., CMP-N-acetylneuraminic acid:lactosylceramide sialyltransferase and UDP-N-acetylgalactosamine:GM3-N-acetylgalactosaminyltransferase, was also studied during development of the nerve and brain. The developmental profiles of both enzymes were consistent with the amounts of GM3 present in the nerve. 相似文献
85.
Ashida H Anderson K Nakayama J Maskos K Chou CW Cole RB Li SC Li YT 《The Journal of biological chemistry》2001,276(30):28226-28232
We found that commercially available sialidases prepared from Clostridium perfringens ATCC10543 were contaminated with an endoglycosidase capable of releasing the disaccharide GlcNAcalpha1-->4Gal from glycans expressed in the gastric gland mucous cell-type mucin. We have isolated this enzyme in electrophoretically homogeneous form from the culture supernatant of this organism by ammonium sulfate precipitation followed by affinity chromatography using a Sephacryl S-200 HR column. The enzyme was specifically retained by and eluted from the column with methyl-alpha-Glc. By NMR spectroscopy, the structure of the disaccharide released from porcine gastric mucin by this enzyme was established to be GlcNAcalpha1-->4Gal. The specificity of this enzyme as an endo-beta-galactosidase was established by analyzing the liberation of GlcNAcalpha1-->4Gal from GlcNAcalpha1-->4Galbeta1-->4GlcNAcbeta1-->6(GlcNAcalpha1--> 4Galbeta1-->3)GalNAc-ol by mass spectrometry. Because this novel endo-beta-galactosidase specifically releases the GlcNAcalpha1-->4Gal moiety from porcine gastric mucin, we propose to call this enzyme a GlcNAcalpha1-->4Gal-releasing endo-beta-galactosidase (Endo-beta-Gal(GnGa)). Endo-beta-Gal(GnGa) was found to remove the GlcNAcalpha1-->4Gal epitope expressed in gastric adenocarcinoma AGS cells transfected with alpha1,4-N-acetylglucosaminyltransferase cDNA. Endo-beta-Gal(GnGa) should become useful for studying the structure and function of glycoconjugates containing the terminal GlcNAcalpha1-->4Gal epitope. 相似文献
86.
Chen YM Lee TH Lee SJ Lin JZ Huang R Chou HN 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》2006,844(1):134-141
Artemia assays and protein phosphatase assays are commonly used for the screening of microcystins (MCs) in algal samples instead of the standard mouse toxicity assay. However, it has been shown that their results are often biased because of the matrix effects. To eliminate the possible interferences in the algal matrices, a new solid-phase extraction (SPE) method using silica gel as a sorbent was developed and evaluated. Results show that this SPE method could not only reduce the toxicity of the Microcystis samples towards brine shrimp by 50-80% but also eliminate 90-100% of the endogenous phosphatase activity from Spirulina and Chlorella samples, thus improving the determination of microcystins in algal samples using either of the two bioanalytical methods. The application of this SPE method as an off-line cleanup for high-performance liquid chromatography (HPLC) with UV detection is also described in this study. After SPE, the HPLC chromatograms of Microcystis samples have clear baselines that have no interferences with the analyte peaks. 相似文献
87.
The mudskipper Periophthalmus walailakae is recorded from Singapore, where it was previously misidentified as Periophthalmodon schlosseri, with which it is syntopic. Periophthalmus walailakae is distinguished from its congeners by the following combination of characters: pelvic fins completely united and shaped like a disk, and first dorsal fin dark brown or black, with a rounded posterior edge and a white distal margin. This species most closely resembles Pn. schlosseri but has one row of teeth on the upper jaw, scales on the isthmus, and a different upper lip and jaw morphology. Contrary to an earlier report, scales are present on the snout, interorbital, and isthmus of Ps. walailakae. The two species can also be distinguished by size, external morphology, and body color patterns. 相似文献
88.
Shen J Hisaeda H Chou B Yu Q Tu L Himeno K 《Biochemical and biophysical research communications》2008,365(4):621-627
The ubiquitin-proteasome system (UPS) plays an indispensable role in inducing MHC class I-restricted CD8+ T cells. In this study, we exploited UPS to induce CD8+ T cells specific for mycobacterial HSP65 (mHSP65), one of the leading vaccine candidates against infection with Mycobacterium tuberculosis. A chimeric DNA termed pU-HSP65 encoding a fusion protein between murine ubiquitin and mHSP65 was constructed, and C57BL/6 (B6) mice were immunized with the DNA using gene gun bombardment. Mice immunized with the chimeric DNA acquired potent resistance against challenge with the syngeneic B16F1 melanoma cells transfected with the mHSP65 gene (HSP65/B16F1), compared with those immunized with DNA encoding only mHSP65. Splenocytes from the former group of mice showed a higher grade of cytotoxic activity against HSP65/B16F1 cells and contained a larger number of granzyme B- or IFN-γ-producing CD8+ T cells compared with those from the latter group of mice. 相似文献
89.
Huang RB Du QS Wang CH Chou KC 《Biochemical and biophysical research communications》2008,377(4):1243-1247
The long-sought three-dimensional structure of the M2 proton channel of influenza A virus was successfully determined recently by the high-resolution NMR [J.R. Schnell, J.J. Chou, Structure and mechanism of the M2 proton channel of influenza A virus, Nature 451 (2008) 591-595]. Such a milestone work has provided a solid structural basis for studying drug-resistance problems. However, the action mechanism revealed from the NMR structure is completely different from the traditional view and hence prone to be misinterpreted as “conflicting” with some previous biological functional studies. To clarify this kind of confusion, an in-depth analysis was performed for these functional studies, particularly for the mutations D44N, D44A and N44D on position 44, and the mutations on positions 27-38. The analyzed results have provided not only compelling evidences to further validate the NMR structure but also very useful clues for dealing with the drug-resistance problems and developing new effective drugs against H5N1 avian influenza virus, an impending threat to human beings. 相似文献
90.