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991.
The long-lived, light-induced radical YD• of the Tyr161 residue in the D2 protein of Photosystem II (PSII) is known to magnetically interact with the CaMn4 cluster, situated ∼ 30 Å away. In this study we report a transient step-change increase in YD• EPR intensity upon the application of a single laser flash to S1 state-synchronised PSII-enriched membranes from spinach. This transient effect was observed at room temperature and high applied microwave power (100 mW) in samples containing PpBQ, as well as those containing DCMU. The subsequent decay lifetimes were found to differ depending on the additive used. We propose that this flash-induced signal increase was caused by enhanced spin relaxation of YD• by the OEC in the S2 state, as a consequence of the single laser flash turnover. The post-flash decay reflected S2 → S1 back-turnover, as confirmed by their correlations with independent measurements of S2 multiline EPR signal and flash-induced variable fluorescence decay kinetics under corresponding experimental conditions. This flash-induced effect opens up the possibility to study the kinetic behaviour of S-state transitions at room temperature using YD• as a probe. 相似文献
992.
Zbigniew Kaniuga Violetta Sączyńska Ewa Miśkiewicz Maciej Garstka 《Acta Physiologiae Plantarum》1999,21(3):231-241
Changes in fatty acids of leaf polar lipids: monogalactosyldiacylglycerol (MGDG), digalactosyldiacylglycerol (DGDG), sulfoquinosyldiacylglycerol
(SQDG) and phosphatidylglycerol (PG) in maize seedlings of chiling-sensitive (CS) CM 7 and Co 151 lines and chilling-tolerant
(CT) S 215 and EP 1 lines upon chilling for either 4 or 6 days in the dark and after rewarming for 4 days at original growth
conditions were studied. The content of free fatty acids (FFA) in control leaves as well as alterations in the proportion
of major fatty acids, unsaturation ratio (UR), double bond index (DBI) and changes in the proportion of heigh-temperature
melting of both phosphatidylglycerol (htm-PG) and sulfoquinovosylglycerol (htm-SQDG) after chilling and rewarming of seedlings
were estimated.
FFA content in intact leaves was 2–3-fold higher in the chilling susceptible CM 7 line than in the other three inbreeds studied.
After chilling for 6 days the level of FFA increased only in CM 7 and S 215 lines by about 30 %. Upon rewarming seedlings
chilled for 6 days the level of FFA increased about two-fold in CS Co 151 line and CT EP 1 line and decreased in CS CM 7 line.
Limited accumulation of FFAs during chilling and post-chilling rewarming of maize seedlings, did not correspond to the extent
of polar lipid breakdown (Kaniuga et al. 1999b) probably due to the contribution of active oxidative systems to the peroxidation of fatty acids under these conditions.
During rewarming seedlings chilled for 6 days major changes were observed in decrease of 18:3 and an increase of 16:0 in all
four polar lipids studied with more pronounced changes in CS than CT lines. Similarly, in CS inbreeds a decrease in UR of
fatty acids in MGDG, DGDG and SQDG after post-chilling rewarming was greater than in CT lines. Proportion of htm-fraction
in both PG and SQDG increased after post-chilling rewarming in all four inbreeds, however to a lesser extent in CT than CS
lines. A similar pattern of changes in DBI in CS and CT maize seedlings was observed in glycolipid and combine lipid classes.
More extensive degradation of polar lipids in CS than CT maize inbreeds following galactolipase action in chloroplasts (Kaniuga
et al. 1998) provides FFAs for initiation of peroxidation by LOX which is manifested by decrease of UR and DBI. This sequence of
reactions during chilling and post-chilling rewarming appears to be a main route of fatty acids peroxidation responsible for
secondary events involved in chilling injury. In addition, the extent of these changes differentiates CS and CT inbreeds.
Contribution of esterified fatty acids in thylakoid lipids to direct peroxidation, may be of minor importance. 相似文献
993.
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996.
Market Failure and the Environmental Policies of Firms: Economic Rationales for "Beyond Compliance" Behavior 总被引:4,自引:0,他引:4
Forest Reinhardt 《Journal of Industrial Ecology》1999,3(1):9-21
This paper is an inquiry into the circumstances under which the voluntary provision of environmental public goods might be sensible from a firm's point of view. If environmental externalities were the only departure from the economic assumptions of perfect competition, and if no firms had preferential access to superior (low-cost) stocks of natural resources, firms that volunteered to internalize costs could not survive. But because externalities coexist with other departures from the competitive paradigm, such as asymmetric information and oligopoly competition, firms may find it in their shareholders' interests to provide environmental public goods to a greater degree than required by law. A number of firms, especially in Europe and North America, assert that they are pursuing "beyond-compliance" environmental policies. From the perspective of a firm's shareholders, it makes sense to pursue such policies if they increase the firm's expected value or if they appropriately manage business risk.
This paper discusses economically rational explanations for such policies. It analyzes the ways in which a firm's chances of financial success in pursuing any one of them are influenced by the firm's market position and organizational capabilities and by the basic structure of the industry in which it competes. 相似文献
This paper discusses economically rational explanations for such policies. It analyzes the ways in which a firm's chances of financial success in pursuing any one of them are influenced by the firm's market position and organizational capabilities and by the basic structure of the industry in which it competes. 相似文献
997.
Karl Schumacher Raimund Strehl Sabine Kloth Michel Tauc Will W. Minuth 《In vitro cellular & developmental biology. Animal》1999,35(8):465-471
Summary During kidney development the embryonic ampullar collecting duct (CD) epithelium changes its function. The capability for
nephron induction is lost and the epithelium develops into a heterogeneously composed epithelium consisting of principal and
intercalated cells. Part of this development can be mimicked under in vitro conditions, when embryonic collecting duct epithelia
are isolated from neonatal rabbit kidneys and kept under perfusion culture. The differentiation pattern is quite different
when the embryonic collecting duct epithelia are cultured in standard Iscove’s modified Dulbecco’s medium as compared to medium
supplemented with additional NaCl. Thus, the differentiation behavior of embryonic CD epithelia is unexpectedly sensitive.
To obtain more information about how much influence the medium has on cell differentiation, we tested medium 199, basal medium
Eagle, Williams’ medium E, McCoys 5A medium, and Dulbecco’s modified Eagle medium under serum-free conditions. The experiments
show that in general, all of the tested media are suitable for culturing embryonic collecting duct epithelia. According to
morphological criteria, there is no difference in morphological epithelial cell preservation. The immunohistochemical data
reveal two groups of expressed antigens. Constitutively expressed antigens such as cytokeratin 19, PCD 9, Na/K ATPase, and laminin are present in all cells of the epithelia independent of the culture media used. In contrast,
a group of antigens detected by mab 703, mab 503, and PNA is found only in individual series. Thus, each culture medium produces
epithelia with a very specific cell differentiation pattern. 相似文献
998.
Masayuki Inouye Takaya Mio Kimiaki Sumino 《Biochimica et Biophysica Acta (BBA)/Molecular and Cell Biology of Lipids》1999,1438(2):204-212
The increased production of oxygen-derived free radicals (OFR) and lipid peroxidation may contribute to vascular complications in diabetes. Some lipid peroxidation products have already been reported to be formed via glucose-induced oxidative stress. We have identified 9-hydroxy linoleic acid (9-OH-C18:2) in the red cell membrane phospholipid of diabetic subjects. We hypothesized that 9-OH-C18:2 would be formed in hydroxyl radical reactions to linoleic acid (C18:2) during glucose-induced oxidative stress, and confirmed that the formation of 9-OH-C18:2 was induced by ultraviolet (UV)-C irradiation to the synthetic C18:2. UV-C light generates highly reactive hydroxy radicals. C18:2 is confirmed to be the precursor of 9-OH-C18:2. To estimate the degree of oxidative damage to red cell membrane phospholipids, we developed a selective ion monitoring gas chromatography-mass spectrometric measurement for C18:2 and 9-OH-C18:2, following methanolysis of red cell membrane phospholipids. The relative peak height ratio of C18:2 to 9-OH-C18:2 (9-OH-C18:2/C18:2) was measured in phospholipid extracts of red cell membranes from healthy (n=29, 3.1±1.9%) and diabetic (n=27, 20.9±16.1%) subjects. It was confirmed that 9-OH-C18:2/C18:2 is significantly (P<0.001) elevated in patients with diabetes. The measurement of 9-OH-C18:2/C18:2 in red cell membranes should be useful for assessing oxidative damage to membrane phospholipids in diabetes. 相似文献
999.
NaCl胁迫对甘薯叶片叶绿体超微结构及一些酶活性的影响 总被引:4,自引:0,他引:4
随NaCl 胁迫浓度的提高,甘薯叶片叶绿体数目逐渐减少, 类囊体膜片层松散、扭曲、破裂并逐渐解体, 叶绿素含量下降。与此同时,H2O2 、MDA 含量增加, ASP、SOD 活性表现出先上升后下降的趋势。耐盐品种在NaCl 胁迫下能维持较强的H2O2 清除能力和较低的MDA 水平 相似文献
1000.
乙烯促进线粒体呼吸过程中活性氧的作用 总被引:6,自引:0,他引:6
外源乙烯能促使绿豆(PhaseolusradiatusL.)黄化幼苗下胚轴线粒体呼吸高峰提前出现及峰值的提高,它对抗氰途径的促进作用比对细胞色素途径的更加显著.外源乙烯作用下绿豆线粒体的超氧阴离子自由基产生速率迅速提高,同时外源的加入使线粒体呼吸高峰的出现明显提前,这从一个侧面表明乙烯对线粒体呼吸的促进作用可能是通过提高线粒体的产生速率而实现的.SOD活性随乙烯处理时间延长而下降,但乙烯作用下的产生并非仅由SOD的活性所决定. 相似文献