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61.
Young-Rae?Chae Keun-Garp?RyuEmail author 《Biotechnology and Bioprocess Engineering》2004,9(5):379-382
Entomopathogenic nematodes are used for insect control. Herein, an extracellular protease was partially purified from a culture
supernatant ofXenorhabdus nematophilus, a symbiotic bacterium of an entomopathogenic nematode,Steinernema glaseri, using precipitation with 80% v/v isopropyl alcohol followed by gel permeation chromatography with a packed Sephacryl S-300
HR media. The partially purified protease exhibited maximal activity at pH 7 in the presence of 1 mM CaCl2. The protease was identified as a metallo-protease based on the inhibition of its activity by the metal chelating agent,
EDTA. 相似文献
62.
Water relations, proline content and gas exchange of leaf were investigated under periodic water stress for two C3 plants
(eggplant and tomato) in a greenhouse to study comparative adaptive responses. Although both species showed reduced water
content of leaf and increased osmolality and proline content under low soil water potential, the recovery capacity after the
stress was better in eggplant than tomato. Both species over-accumulated proline under low soil water potential and returned
to its initial concentration during the recovery, indicating that proline may act as an osmoprotectant during drought. Proline
was directly corresponding with osmolality during stress, and dehydration stress reduced the gas exchange parameters such
as transpiration rate (ET), stomatal conductance (GS), and photosynthesis rate (Pn). At the final stage of the experiment
both species showed 2.6 and 3.3 times lower Pn and 27 and 19 times lower GS for eggplant and tomato, respectively, as compared
to control. But after stress was relieved by rewatering, both plants increased GS for 2 to 3 times and Pn for 4.5 times. Eggplant
showed better water use efficiency (WUE) in relation to fruit production under the stress than tomato. Higher biomass allocation
at root and fruit parts in eggplant indicated more efficient recovery than that of tomato. These findings inferred that both
C3 plants developed internal complementary drought survival mechanism by lowering relative water content, increasing proline,
and decreasing stomatal conductance but eggplants withstood the periodic draughting better than tomato, mainly due to its
ability to recover from a water stress condition. 相似文献
63.
Zeslawska E Jacob U Schweinitz A Coombs G Bode W Madison E 《Journal of molecular biology》2003,328(1):109-118
Urokinase type plasminogen activator (uPA), a trypsin-like serine proteinase, plays an important role in normal tissue re-modelling, cell adhesion, and cell motility. In addition, studies utilizing normal animals and potent, selective uPA inhibitors or genetically modified mice that lack functional uPA genes have demonstrated that uPA can significantly enhance tumor initiation, growth, progression and metastasis, strongly suggesting that this enzyme may be a promising anti-cancer target. We have investigated the structure-activity relationship (SAR) of peptidomimetic inhibitors of uPA and solved high resolution X-ray structures of key, lead small molecule inhibitors (e.g. phenethylsulfonamidino(P4)-D-seryl(P3)-L-alanyl(P2)-L-argininal(P1) and derivatives thereof) in complex with the uPA proteinase domain. These potent inhibitors are highly selective for uPA. The non-natural D-seryl residue present at the P3 position in these inhibitors contributes substantially to both potency and selectivity because, due to its D-configuration, its side-chain binds in the S4 pocket to interact with the uPA unique residues Leu97b and His99. Additional potency and selectivity can be achieved by optimizing the inhibitor P4 residue to bind a pocket, known as S1sub or S1beta, that is adjacent to the primary specificity pocket of uPA. 相似文献
64.
David-Schwartz R Badani H Smadar W Levy AA Galili G Kapulnik Y 《The Plant journal : for cell and molecular biology》2001,27(6):561-569
Vesicular arbuscular mycorrhizal fungi infect plants by means of both spores and vegetative hyphae at early stages of symbiosis. Using 2500 M2 fast-neutron-mutagenized seeds of the miniature tomato (Lycopersicon esculentum) cultivar, Micro-Tom, we isolated a mutant, M161, that is able to resist colonization in the presence of Glomus intraradices spores. The myc(-) phenotype of the mutant was stable for nine generations, and found to segregate as a single Mendelian recessive locus. The mutant exhibited morphological and growth-pattern characteristics similar to those of wild-type plants. Alterations of light intensity and day/night temperatures did not eliminate the myc(-) characteristic. Resistance to mycorrhizal fungal infection and colonization was also evident following inoculation with the fungi Glomus mosseae and Gigaspora margarita. Normal colonization of M161 was evident when mutant plants were grown together with arbuscular mycorrhizal-inoculated wild-type plants in the same growth medium. During evaluation of the pre-infection stages in the mutant rhizosphere, spore germination and appressoria formation of G. intraradices were lower by 45 and 70%, respectively, than the rates obtained with wild-type plants. These results reveal a novel, genetically controlled step in the arbuscular mycorrhizal colonization process, governed by at least one gene, which significantly reduces key steps in pre-mycorrhizal infection stages. 相似文献
65.
春玉米根系生育特征与冠层关系的研究 总被引:12,自引:0,他引:12
以农田实际观测资料为依据,分析了春玉米根系生育特征及其与冠层生长的关系,并提出了定量描述方程;较详细地阐述了水分条件对根系生长的影响,指出利用根系伸展深度确定灌溉计划湿润深度和进行根冠调控,以指导农田优化灌溉的可行性。 相似文献
66.
Lenfant P 《Comptes rendus biologies》2002,325(3):239-252
A total of 842 white sea bream (Diplodus sargus), sampled in Banyuls-sur-Mer, were analysed to test 'genotype-phenotype' relationship for various characters related to the fitness. The results show significant differences (MLH and FIS) for the age according to the sex between females carrying out and not carrying out sexual inversion. This suggests an overdominance for old females and a genetic sex determination. The individuals laying very early during the period of reproduction are also differentiated from the individuals reproducing later in the season. These results suggest either a stable calendar of laying in time separating the individuals genetically reproducing precociously from the others and this by differential selection and/or genetic drift either a Wahlund effect among cohorts. 相似文献
67.
Cordoba E Shishkova S Vance CP Hernández G 《The Plant journal : for cell and molecular biology》2003,33(6):1037-1049
Legumes acquire significant amounts of nitrogen for growth from symbiotic nitrogen fixation. The glutamine synthetase (GS)/NADH-dependent glutamate synthase (NADH-GOGAT) cycle catalyzes initial nitrogen assimilation. This report describes the impact of specifically reducing nodule NADH-GOGAT activity on symbiotic performance of alfalfa (Medicago sativa L.). Four independent transgenic alfalfa lines, designated GA89, GA87, GA88, and GA82 (for GOGATantisense), containing an antisense NADH-GOGAT cDNA fragment under the control of the soybean leghemoglobin (lbc3) promoter were evaluated. The GA plants were fertile and showed normal growth in non-symbiotic conditions. The NADH-GOGAT antisense transgene was heritable and the T1 plants showed phenotypic alterations - similar to primary transformants. Clonally propagated plants were inoculated with Sinorhizobium meliloti after rooting and the symbiotic phenotype was analyzed 21 days post-inoculation. Nodules of each GA line had reduced NADH-GOGAT activity, ranging from 33 to 87% of control plants, that was accompanied by comparable decreases in RNA and protein. Plants from the GA89 line, with the lowest NADH-GOGAT activity (c. 30%), presented a strikingly altered symbiotic phenotype: concomitantly activities of key enzyme for carbon and nitrogen assimilation decreased; nodule amino acids and amides were reduced while sucrose accumulated. Antisense GOGAT plants were chlorotic, reduced in fresh weight, and had a lower N content than control plants. Photosynthesis was also impaired in antisense plants. Specifically, reducing NADH-GOGAT in nodules resulted in plants having impaired nitrogen assimilation and altered carbon/nitrogen metabolic flux. 相似文献
68.
The assembly of microtubules generates forces that play a role in cellular motility processes such as the motion of chromosomes
during mitosis. Recently, Mogilner and Oster proposed a model for the growth of microtubules that agrees quantitatively with
the force-velocity relation measured for individual microtubules. In addition, the authors predicted that the stall force
for any polymer consisting of N independently growing protofilaments should increase as the square root of N. We simulated this model and found that the stall force increases linearly with N, and is in fact consistent with the maximum force predicted by thermodynamic arguments. We show that this discrepancy can
be explained by a more careful treatment of the “off-term” in the Mogilner-Oster model.
Received: 27 September 1999 / Revised version: 12 December 1999 / Accepted: 20 December 1999 相似文献
69.
次生栎林蒸腾强度与生态因子的关系 总被引:7,自引:0,他引:7
采用多元回归分析和灰色关联分析方法,探讨下蜀次生栎林蒸腾强度与生态因子的相关关系。研究认为用二次工咕次多项式回归方程和指数回归方程拟合更能反映各生态因子在整个生长季中与蒸腾强度关系的性质。影响蒸腾强度的主要生态因子是温度和净辐射;其次是空气相对湿度和土壤热流通量;风速和土壤含水率的影响很小。灰色关联分析与多元回归分析的结论一致。研究结果为进一步阐明次生栎林的结构和功能提供了理论基础。 相似文献
70.
Tsukasa Tameyasu Naokata Ishii Noboru Oishi Mitsuyo Shimada Ibuki Shirakawa Tsuyoshi Akimoto Naoto Yamamoto Shoichi Kosuge Haruo Sugi 《Comparative biochemistry and physiology. Part A, Molecular & integrative physiology》1998,120(4):731-736
To investigate characteristics of ATP-dependent sliding of a non-muscle cell myosin, obtained from a cellular slime mold Dictyostelium discoideum, on actin filament, we prepared hybrid thick filaments, in which Dictyostelium myosin was regularly arranged around paramyosin filaments obtained from a molluscan smooth muscle. A single to a few hybrid filaments were attached to a polystyrene bead (diameter, 4.5 μm; specific gravity, 1.5), and the filaments were made to slide on actin filament arrays (actin cables) in the internodal cell of an alga Chara corallina, mounted on the rotor of a centrifuge microscope. The filament-attached bead was observed to move with a constant velocity under a constant external load for many seconds. The steady-state force–velocity relation of Dictyostelium myosin sliding on actin cables was hyperbolic in shape except for large loads ≤0.7–0.8 P0, being qualitatively similar to that of skeletal muscle fibres, despite a considerable variation in the number of myosin molecules interacting with actin cables. Comparison of the P–V curves between Dictyostelium myosin and muscle myosins sliding on actin cables suggests that the time of attachment to actin in a single attachment–detachment cycle is much longer in Dictyostelium myosin than in muscle myosins. 相似文献