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21.
Transmucosal transport rates for triolein in proximal and distal intestine were compared in unanesthetized rats. Emulsified [1-14-C] triolein together with bile and pancreatic juice from donor rats was infused for 6 hr into either the duodenum or the midpoint of the small intestine at such a rate that absorption was essentially complete in both regions of the intestine. Lymph was collected from the thoracic duct during triolein infusion and for an additional 6-hr period. The decrease in the rate of lymphatic output of labeled fat was found to follow a simple exponential function in all animals. This rate of decrease (decay rate) was used to calculate the half-times of lipid turnover through the intestinal wall and the fractional output rates. Distal intestine transported lipid 40% more slowly than proximal intestine, and the difference was associated with a greater accumulation of triglyceride in the distal intestinal wall. Chylomicron synthesis and/or release is the rate-limiting step for distal lymphatic fat transport in vivo, whereas fat uptake from the lumen is rate limiting for proximal intestine. 相似文献
22.
Sixin Jiang Brigitte Heller Vincent S. Tagliabracci Lanmin Zhai Jose M. Irimia Anna A. DePaoli-Roach Clark D. Wells Alexander V. Skurat Peter J. Roach 《The Journal of biological chemistry》2010,285(45):34960-34971
Stbd1 is a protein of previously unknown function that is most prevalent in liver and muscle, the major sites for storage of the energy reserve glycogen. The protein is predicted to contain a hydrophobic N terminus and a C-terminal CBM20 glycan binding domain. Here, we show that Stbd1 binds to glycogen in vitro and that endogenous Stbd1 locates to perinuclear compartments in cultured mouse FL83B or Rat1 cells. When overexpressed in COSM9 cells, Stbd1 concentrated at enlarged perinuclear structures, co-localized with glycogen, the late endosomal/lysosomal marker LAMP1 and the autophagy protein GABARAPL1. Mutant Stbd1 lacking the N-terminal hydrophobic segment had a diffuse distribution throughout the cell. Point mutations in the CBM20 domain did not change the perinuclear localization of Stbd1, but glycogen was no longer concentrated in this compartment. Stable overexpression of glycogen synthase in Rat1WT4 cells resulted in accumulation of glycogen as massive perinuclear deposits, where a large fraction of the detectable Stbd1 co-localized. Starvation of Rat1WT4 cells for glucose resulted in dissipation of the massive glycogen stores into numerous and much smaller glycogen deposits that retained Stbd1. In vitro, in cells, and in animal models, Stbd1 consistently tracked with glycogen. We conclude that Stbd1 is involved in glycogen metabolism by binding to glycogen and anchoring it to membranes, thereby affecting its cellular localization and its intracellular trafficking to lysosomes. 相似文献
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24.
Previous data generated by ourselves and others questioned the role of degranulation as a mechanism to explain CTL-mediated cytotoxicity. In this report we examine this tissue in greater depth. CTL-mediated lysis was probed with three different inhibitors. 4,4'-diisothiocyano-2,2'-disulfonic acid stilbene inhibits degranulation in a wide range of cell types, including CTL. EGTA, through chelation of Ca2+, also inhibits degranulation processes in CTL, and would inhibit other events or processes dependent on extracellular Ca2+. We also used prolonged exposure to PMA to exhaust PKC activity in CTL. Using these inhibitors, we have defined three pathways of lysis used by CTL. One pathway requires Ca2+, is PMA sensitive, but does not depend on degranulation. The second pathway is independent of Ca2+, is not PMA sensitive, and also does not depend on degranulation. All primary CTL and cloned CTL lyse most target cells via pathway I. However, when confronted with certain target cells (which we have referred to previously as Ca2+-independent target cells), pathway II is induced. When pathway II is induced, pathway I apparently shuts down. We show here that pathway II does not depend on protein synthesis, and that it also leads to DNA solubilization in target cells. A limited number of cloned CTL use pathways I and II as just described, but use in addition, and simultaneously, a third pathway that appears to involve degranulation. This pathway is seen irregularly in most CTL clones, and may be influenced by levels of IL-2 in the culture medium. 相似文献
25.
Rat renal phosphate-dependent glutaminase is rapidly inactivated by incubating with L-2-amino-4-oxo-5-chloropentanoic scid. Concentrations of phosphate, which increase the glutaminase activity, decrease the rate of inactivation by chloroketone. In addition, inactivation is not blocked by glutamine. Instead, glutamate was shown to specifically reduce the rate of chloroketone inactivation. Upon sodium lauryl sulfate-polyacrylamide gel electrophoresis, the purified glutaminase preparation exhibits at least five protein staining bands which range in molecular weight from 57,000 to 75,000. Studies with 14C-labeled chloroketone indicate that this reagent reacts with each of these peptides. The mean stoichiometry of binding was calculated to be 1.3 mol/mol of enzyme. Therefore, these results indicate that the glutaminase may contain a specific site for binding glutamate and that the purified enzyme consists of a series of related peptides which may have resulted from partial proteolysis. 相似文献
26.
Alveolar function following surfactant deactivation 总被引:4,自引:0,他引:4
Nieman G. F.; Bredenberg C. E.; Clark W. R.; West N. R. 《Journal of applied physiology》1981,51(4):895-904
27.
Kirstin Clark Nichols 《International journal for parasitology》1975,5(2):245-252
Temnocephala novae-zealandie, a flatworm epizoic on crayfish, was examined by light and electron microscopy to investigate the variation within rhabdocoel turbellarians and to provide information on the possible structural modifications in the evolution of parasitism. The sucker is clearly glandular; the tentacular glands are eosinophilic and at the surface store and often release mucus as a coiled thread; the epidermis is clearly not reduced in structure and contains septate junctions in the anterior portion. Light microscope studies documented the presence of ten pair of paranephrocytes (athrocytes). In the laboratory, egg deposition, survival on and apart from the host and another crayfish, and behavior during the host molt were observed. 相似文献
28.
29.
Seasonal occurrence of Campylobacter spp. in surface waters and their correlation with standard indicator bacteria 总被引:4,自引:0,他引:4
A M Carter R E Pacha G W Clark E A Williams 《Applied and environmental microbiology》1987,53(3):523-526
Campylobacter jejuni, Campylobacter coli, and a Campylobacter-like organism were isolated from a number of natural water sources in central Washington, including ponds, lakes, and small mountain streams at elevations ranging from 1,460 to 5,400 feet (ca. 445 to 1,646 m) above sea level. At the two sites where extensive sampling was done, the bacteria were recovered throughout the year. Generally, the recovery rates were highest in the fall and winter months and lowest during the spring and summer months. Campylobacter density did not show significant correlation with microbiological (plate counts of fecal and total coliforms, fecal streptococci, and heterotrophic bacteria) or physical (water temperature, pH, and conductivity) parameters. 相似文献
30.
L Kwock W C Davenport R L Clark J Zarembra B Lingle E L Chaney M Friedman 《Radiation research》1987,111(2):276-291
We studied the effects of ionizing radiation on the morphology of the pulmonary circulation using an in vivo rat model and an in vitro pulmonary artery endothelial cell model. Gamma radiation was given as either an acute (30 Gy) or fractionated (5 X 6 Gy) dose to one hemithorax of rats. An acute 30-Gy dose delivered resulted in a 70% decrease in pulmonary arterial perfusion, using technetium-99m microaggregated albumin (99mTc-MAA), in the irradiated lung by 2-3 weeks after irradiation. Pulmonary microradiographs, using a barium sulfate perfusion method, obtained 2-3 weeks after irradiation demonstrated widespread loss of capillary filling and segmentation of the vessels. Histologic examination demonstrated intact capillaries, suggesting that the alterations in pulmonary perfusion were at the precapillary level. Similar abnormalities in lung perfusion and morphology were found after delivery of fractionated doses of radiation, but the onset of the changes was delayed, occurring 4-6 weeks postirradiation. Using cultured pulmonary endothelial cell monolayers, cell sloughing and retraction from the surface substrate were observed within 24 h after in vitro delivery of 30 Gy. Similar findings occurred in monolayers given fractionated doses (5 X 6 Gy) of radiation 2-3 days after the final dose. The in vivo animal and in vitro endothelial cell models offer a useful means of examining the morphologic alterations involved in radiation lung vascular damage. 相似文献