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121.
Throckmorton D Kurscheid-Reich D Rosales OR Rodriguez-Commes J Lopez R Sumpio B Zhong Q Ding KH McCarthy R Barrett PQ Isales CM 《Peptides》2002,23(1):79-85
We have previously reported that parathyroid hormone (PTH) has specific effects on a human umbilical vein endothelial cell line. Further studies were performed to characterize the signaling cascades initiated by PTH. We report that PTH induced the appearance of voltage sensitive calcium channels. Furthermore, PTH increased ceramide but not diacylglycerol content. Since elevations in [Ca(2+)](i) and phospholipid turnover are signals for the activation of protein kinase C (PKC), the cells were screened for PKC isoforms. PTH induced a redistribution of the PKCepsilon to the particulate fractions of cell homogenates. In summary, PTH induced PKC translocation through a calcium-phospholipid pathway in an endothelial cell line. 相似文献
122.
Epand RF Martinou JC Montessuit S Epand RM Yip CM 《Biochemical and biophysical research communications》2002,298(5):744-749
Direct imaging of the interaction of the apoptotic protein, Bax, with membrane bilayers shows the presence of toroidal-shaped pores using atomic force microscopy. These pores are sufficiently large to allow passage of proteins from the intermitochondrial space. Both the perturbation of the membrane and the amount of protein bound to the bilayer are increased in the presence of calcium. The results from the imaging are consistent with leakage studies from liposomes of the same composition. The work shows that Bax by itself can form pores in membrane bilayers. 相似文献
123.
Decidual lymphocytes of human spontaneous abortions induce apoptosis but not necrosis in JEG-3 extravillous trophoblast cells 总被引:6,自引:0,他引:6
Olivares EG Muñoz R Tejerizo G Montes MJ Gómez-Molina F Abadía-Molina AC 《Biology of reproduction》2002,67(4):1211-1217
The human decidua contains an unusually high proportion of lymphocytes, mainly NK and T cells, which are potentially cytotoxic to the trophoblast when they are stimulated with certain cytokines. Given the high incidence of spontaneous abortion in humans and other species, our working hypothesis is that decidual lymphocytes are involved in immunological mechanisms that attack the trophoblast and induce abortion when any gestational problem arises. To test this hypothesis, flow cytometry was used to compare decidual lymphocyte populations in first-trimester spontaneous abortions and elective terminations of first-trimester pregnancy. We found significantly higher proportions of decidual lymphocytes that expressed activation markers, and of T cells (mainly T helper cells) in spontaneous abortions than in elective terminations of pregnancy. Decidual lymphocytes from spontaneous abortion, like decidual lymphocytes from elective termination of pregnancy and peripheral blood lymphocytes, were however, unable to lyse the JEG-3 extravillous cytotrophoblast cell line in a (51)Cr-release assay. Nevertheless, decidual lymphocytes from spontaneous abortion, unlike decidual lymphocytes from elective termination of pregnancy and peripheral blood lymphocytes, induced apoptosis in JEG-3 cells as determined by DNA fragment-release assay. Hematoxylin and eosin staining showed a significantly higher proportion of apoptotic JEG-3 cells when these cells were treated with decidual lymphocytes from spontaneous abortion than when JEG-3 cells were cultured with decidual lymphocytes from elective termination of pregnancy. The ultrastructural signs of apoptosis were confirmed by electron microscopy. These data support the hypothesis that activated decidual lymphocytes participate in human spontaneous abortion by inducing apoptosis but not necrosis of the trophoblast. 相似文献
124.
Valdés R Casado FJ Pastor-Anglada M 《Biochemical and biophysical research communications》2002,296(3):575-579
Most nucleoside-derived anticancer drugs are taken up by the high-affinity Na-dependent nucleoside transporter CNT1. Since such drugs are to some extent cell-cycle-dependent in their cytotoxic action, we examined the relationship between CNT1 expression and cell-cycle progression in the rat hepatoma cell line FAO. Cell cultures were synchronized either at late G1 or early S stages by combining mimosin treatment with either previous synchronization or not by serum starvation. Cell-cycle progression was then assessed by measuring [methyl-3H]thymidine incorporation into DNA and monitoring cyclin E and A protein levels. In these conditions, CNT1 protein amounts increase at the G1-S transition. When cells were synchronized using hydroxyurea (HU), which directly interacts with nucleotide metabolism by inhibiting ribonucleotide reductase, CNT1 protein amounts increased in synchronized cells and remained high during cell-cycle progression. These data indicate that CNT1 adapts to cell-cycle progression and responds to nucleos(t)ide metabolism status, a feature that might contribute to the cytotoxic action of cell-cycle-dependent anticancer drugs. 相似文献
125.
Bezerra FS Nogueira-Machado JA Martins-Souza RL Chaves MM Correa RF Coelho PM 《Memórias do Instituto Oswaldo Cruz》2003,98(1):73-75
High doses of gamma radiation (10 Krad) in Biomphalaria tenagophila snails (Taim strain), which have been found to be resistant to Schistosoma mansoni, were not sufficient to impair their resistance to the parasite. The number of hemocytes, as well as their phagocytic activity, were not affected by irradiation, thus showing resemblance with mammal macrophages, which are resistant to gamma irradiation also. 相似文献
126.
Ferreira FM Palmeira CM Seiça R Moreno AJ Santos MS 《Journal of biochemical and molecular toxicology》2003,17(4):214-222
Several studies have been carried out to evaluate the alterations in mitochondrial functions of diabetic rats. However, some of the results reported are controversial, since experimental conditions, such as aging, and/or strain of animals used were different. The purpose of this study was to evaluate the metabolic changes in liver mitochondria, both in the presence of severe hyperglycaemia (STZ-treated rats) and mild hyperglycaemia (Goto-Kakizaki (GK) rats). Moreover, metabolic alterations were evaluated both at initial and at advanced states of the disease. We observed that both models of type 1 and type 2 diabetes presented alterations on respiratory chain activity. Because of continual severe hyperglycaemia, 9 weeks after the induction of diabetes, the respiratory function declined in STZ-treated rats, as observed by membrane potential and respiratory ratios (RCR, P/O, and FCCP-stimulated respiration) assessment. In contrast, GK rats of 6 months age presented increased respiratory ratios. To localize which respiratory complexes are affected by diabetes, enzymatic respiratory chain activities were evaluated. We observed that succinate dehydrogenase and cytochrome c oxidase activities were significantly augmented both in STZ-treated rats and GK rats of 6 months age. Moreover, H(+)-ATPase activity was also significantly increased in STZ-treated rats with 3 weeks of diabetes and in GK rats of 6 months age as compared to controls. Therefore, these results clearly suggest that both animal models of diabetes present some metabolic adjustments in order to circumvent the deleterious effects promoted by the high glucose levels typical of the disease. 相似文献
127.
Regulation by irradiance level of the mechanism for dissolved inorganic carbon (DIC) acquisition was examined in the red
macroalga Gracilaria tenuistipitata Zhang et Xia. For this purpose, affinity for external DIC, carbonic anhydrase (CA; EC 4.2.1.1) activity and content of ribulose-1,5-bisphosphate
carboxylase/oxygenase (Rubisco; EC 4.1.1.39) were determined in thalli grown at 45 and 500 μmol photons m−2 s−1. Oxygen evolution rates declined by 50% when the medium pH was changed from 8.1 to 8.7, and the pH compensation point attained
was ca. 9.2. These characteristics were unaffected by the light treatments. In contrast, photosynthetic conductance for DIC
at pH 8.7 was doubled in thalli grown at high irradiance compared with those grown at low irradiance (to 0.74 × 10−6 from 0.33 × 10−6 m s−1). Photosynthetic rates at saturating DIC concentration were also higher by 60% in thalli grown at high irradiance. These
differences could not be attributed to changes in the use of external DIC, since external CA activity did not vary. Although
the irradiance level did not modify the pool size of Rubisco, Rubisco content expressed on a chlorophyll a basis was almost doubled at high irradiance. These results likely indicate that the internal transport of DIC towards the
active-site of Rubisco, rather than the external use of DIC, is enhanced in the thalli grown at high irradiance.
Received: 7 June 1999 / Accepted: 16 October 1999 相似文献
128.
Ana Maria Costa-Leonardo Helena Xavier Soares Raquel Cristina Barsotti 《Entomologia Experimentalis et Applicata》1998,88(2):109-114
In this paper we examine the potential of the termites Armitermes euamignathus Silvestri: 1901 and Embiratermes festivellus (Silvestri, 1901) (Isoptera, Termitidae, Nasutitermitinae) to produce neotenics experimentally. Three nests of the mound-building termite A. euamignathus, from the Brazilian cerrado, had their primary queens removed in August 1994. After 12 months, only one mound survived; it had a normal appearance. In this healthy, orphaned colony we found the primary king, six physogastric nymphoid female replacement reproductives, two ergatoid female replacement reproductives, 46 nymphs, several presoldiers, soldiers, workers, larvae and many eggs. These data show that neotenics in A. euamignathus may originate from both workers and nymphs, but nymphoids are produced in larger numbers. The biometric study of nymphs and nymphoids suggests that these brachypterous neotenics were derived from third instar nymphs after a single moult or from four instar nymphs after a reduction of wing bud length. A piece of an E. festivellus nest with some third instar nymphs, soldiers and workers was kept under laboratory conditions. After 12 months, the whole experimental subcolony was examined and appeared to contain two pigmented nymphoid females, two pigmented nymphoid males, only one larva, seven nymphs of the same instar, 148 workers, five soldiers and many eggs. These results also indicate the capacity of the termite E. festivellus to produce nymphoid neotenics. These neotenic females were laying eggs, but they were not physogastric after a year, unlike some nymphoids of the same species collected from natural colonies. 相似文献
129.
Vladimir I. Razinkov Grigory B. Melikyan Richard M. Epand Raquel F. Epand Fredric S. Cohen 《The Journal of general physiology》1998,112(4):409-422
Cells expressing the hemagglutinin protein of influenza virus were fused to planar bilayer membranes containing the fluorescent lipid probes octadecylrhodamine (R18) or indocarbocyanine (DiI) to investigate whether spontaneous curvature of each monolayer of a target membrane affects the growth of fusion pores.
R18 and DiI lowered the transition temperatures for formation of an inverted hexagonal phase, indicating that
these probes facilitate the formation of negative curvature structures. The probes are known to translocate from
one monolayer of a bilayer membrane to the other in a voltage-dependent manner. The spontaneous curvature of
the cis monolayer (facing the cells) or the trans monolayer could therefore be made more negative through control of the polarity of voltage across the planar membrane. Electrical admittance measurements showed that the
open times of flickering fusion pores were shorter when probes were in trans monolayers and longer when in cis
monolayers compared with times when probe was symmetrically distributed. Open times were the same for probe
symmetrically distributed as when probes were not present. Thus, open times were a function of the asymmetry of
the spontaneous curvature between the trans and cis monolayers. Enriching the cis monolayer with a negative curvature probe reduced the probability that a small pore would fully enlarge, whereas enriching the trans monolayer
promoted enlargement. Lysophosphatidylcholine has positive spontaneous curvature and does not translocate.
When lysophosphatidylcholine was placed in trans leaflets of planar membranes, closing of fusion pores was rare.
The effects of the negative and positive spontaneous curvature probes do not support the hypothesis that a flickering pore closes from an open state within a hemifusion diaphragm (essentially a “flat” structure). Rather, such effects support the hypothesis that the membrane surrounding the open pore forms a three-dimensional hourglass
shape from which the pore flickers shut. 相似文献
130.
Kelly E. Leon Raquel Buj Elizabeth Lesko Erika S. Dahl Chi-Wei Chen Naveen Kumar Tangudu Yuka Imamura-Kawasawa Andrew V. Kossenkov Ryan P. Hobbs Katherine M. Aird 《The Journal of cell biology》2021,220(8)
Oncogene-induced senescence (OIS) is a stable cell cycle arrest that occurs in normal cells upon oncogene activation. Cells undergoing OIS express a wide variety of secreted factors that affect the senescent microenvironment termed the senescence-associated secretory phenotype (SASP), which is beneficial or detrimental in a context-dependent manner. OIS cells are also characterized by marked epigenetic changes. We globally assessed histone modifications of OIS cells and discovered an increase in the active histone marks H3K79me2/3. The H3K79 methyltransferase disruptor of telomeric silencing 1-like (DOT1L) was necessary and sufficient for increased H3K79me2/3 occupancy at the IL1A gene locus, but not other SASP genes, and was downstream of STING. Modulating DOT1L expression did not affect the cell cycle arrest. Together, our studies establish DOT1L as an epigenetic regulator of the SASP, whose expression is uncoupled from the senescence-associated cell cycle arrest, providing a potential strategy to inhibit the negative side effects of senescence while maintaining the beneficial inhibition of proliferation. 相似文献