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891.
892.
Temperature increases due to absorption of 1.2 GHz, CW, 70 mW/cm2, radio frequency (RF) energy, were measured in 3.3-cm-radius homogeneous muscle-equivalent spheres, M. mulatta cadaver heads (both detached from and attached to the body) and living, anesthetized M. mulatta heads. Temperatures were measured with a Vitek, Model 101 Electrothermia Monitor and temperature distributions were compared to theoretical predictions from a thermal-response model of a simulated cranial structure. The results show that the thermal response model accurately predicts the temperature distribution in muscle-equivalent spheres, the distribution of temperature in detached M. mulatta heads when exposed from the back of the head, and the distribution of temperature in attached M. mulatta cadaver heads for animals oriented with body parallel to the H-field. The temperature distribution in the detached M. mulatta heads varies markedly with exposure orientation, ie, facing forward, backward, or to the side. The orientation of the M. mulatta cadaver body significantly affects the temperature distribution in the head - with H-field orientation showing high, nonuniform values, and E-field orientation showing low, uniform values. In live animals blood flow produces a significant short-term effect on the temperature distribution in the midbrain, but not the cortex. Midbrain temperatures are both significantly higher and lower than the comparable cadaver measurements, depending on location. 相似文献
893.
Jela Brozmanová ?ubica ?ernáková Viera Vl?ková Jozef Duraj Ivana Fridrichová 《Molecular & general genetics : MGG》1991,227(3):473-480
Summary The Escherichia coli recA protein coding region was ligated into an extrachromosomally replicating yeast expression vector downstream of the yeast alcohol dehydrogenase promoter region to produce plasmid pADHrecA. Transformation of the wild-type yeast strains YNN-27 and 7799-4B, as well as the recombination-deficient rad52-t C5-6 mutant, with this shuttle plasmid resulted in the expression of the bacterial 38 kDa RecA protein in exponential phase cells. The wild-type YNN27 and 7799-4B transformants expressing the bacterial recA gene showed increased resistance to the toxic effects of both ionizing and ultraviolet radiation. RecA moderately stimulated the UV-induced mutagenic response of 7799-4B cells. Transformation of the rad52-t mutant with plasmid pADHrecA did not result in the complementation of sensitivity to ionizing radiation. Thus, the RecA protein endows the yeast cells with additional activities, which were shown to be error-prone and dependent on the RAD52 gene. 相似文献
894.
This work is based on a previous observation and on a related mathematical modeling regarding the linear growth of a colony of microorganisms under given conditions. We had previously shown that the growth rate of the colony is merely proportional to the individual exponential multiplication constant, , of the microorganisms.Tiny colonies of penicillium are subjected to different doses of irradiation. The subsequent observation of the colonies' growth rate beautifully furnishes a measure of how the multiplication constant, , of the microorganism is affected by irradiation.The plot of with respect to the irradiation dose, shows a linear interdependence between the two quantities. The extrapolation of this plot easily yields the radiation pasteurization dose of the microorganisms in hand. 相似文献
895.
Gunilla Frykholm Bengt Glimelius Sven Richter Jörgen Carlsson 《In vitro cellular & developmental biology. Animal》1991,27(12):900-906
Summary A panel of human colon carcinoma cell lines were characterized regarding both antigenic heterogeneity and variations in radiosensitivity.
Monoclonal antibodies were used to study the expression of carcinoembryonic antigen (CEA), gastrointestinal cancer antigen
(GICA or CA 19-9) and carcinoma-associated antigen (CA-50). Radiosensitivity was studied with the clonogenic survival technique.
Three cell lines, LS 174T, HCTC, and SW 1116 stained positive for all three antigens. HT-29 was positive for CA 19-9 and CA-50
whereas Caco-2 was positive for CEA and CA 19-9. The cell lines SW 620 and LIM 1215 only stained positive for one of the antigens,
CA-50 and CEA, respectively. In nearly all positive cases the stainings were very heterogeneous with mixtures of positive
and negative cells. One exception was the HCTC cells which stained homogeneously for the CA 19-9 and CA-50 antigens. The neuroendocrinelike
COLO 320 cells were negative in all cases. The radiosensitivity varied strongly between the cell lines with Dq-values between 0.8 and 1.9, extrapolation numbers between 2.0 and 4.7, Do-values between 1.1 and 2.8. The surviving fraction at 2 Gy varied between 0.3 and 0.7 with HCTC as the most radiosensitive
and HT-29 as the most radioresistant cell line. Thus, there were differences in antigenic expression and intrinsic radiosensitivity
between the cell-lines and antigenic heterogeneities within each cell line. The analyzed panel of cell lines will be valuable
in studies of dose-effect relations for monoclonal antibodies labeled with toxic radionuclides simulating both antigenic heterogeneity
and variations in radiosensitivity. 相似文献
896.
There was a 5-fold increase in cytotoxicity for cumene hydroperoxide, 10-fold for tert-butyl hydroperoxide and 25-fold for hydrogen peroxide, under metabolizing conditions (37°C) in comparison to nonmetabolizing conditions (0°C), when human P31 cells were exposed for 60 min. The induction of DNA single-strand breaks correlated poorly with cytotoxicity. Hydrogen peroxide was by far the most effective agent inducing single-strand breaks irrespective of temperature. Cumene hydroperoxide produced fewer strand breaks than tert-butyl hydroperoxide despite its greater cytotoxicity at either 37°C or at 0°C. The pattern of single-strand break induction did not change with temperature. The number of breaks, however, increased when the cells were exposed at 37°C. The pattern of rejoining was similar for hydrogen peroxide- and tert-butyl hydroperoxide-induced breaks at both temperatures whereas the rejoining of cumene hydroperoxide-induced breaks deviated somewhat from this pattern. The results indicate that there is no clear-cut relationship between induction of DNA single-strand breaks and cytotoxicity after hydroperoxide exposure. 相似文献
897.
J. C. Sanford Y. S. Chyi B. I. Reisch 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1984,67(6):553-558
Summary Experiments were designed and carried out to investigate the possibility of inducing egg transformation in tomato, as described by Pandey in Nicotiana L. Pollinations were made, which included the following treatments: irradiated donor pollen, irradiated donor pollen mixed with normal self pollen, irradiated donor pollen followed by delayed self-pollination, and a simple pollen mixture of non-irradiated donor and self pollen. No transformants were found after screening 5,620 seedlings representing 22,300 potential transformation events. If egg transformation occurs, it would appear to be limited to species outside of Lycopersicon esculentum Mill.Approved by the Director of the New York State Agricultural Experiment Station for publication as Journal Paper No. 3537, August 5, 1983 相似文献
898.
The influences of various day/night air temperatures on net CO2 uptake and nocturnal acid accumulation were determined for Opuntia ficus-indica, complementing previous studies on the water relations and responses to photosynthetically active radiation (PAR) for this widely cultivated cactus. As for other Crassulacean acid metabolism (CAM) plants, net nocturnal CO2 uptake had a relatively low optimal temperature, ranging from 11°C for plants grown at day/night air temperatures of 10°C/0°C to 23°C at 45°C/35°C. Stomatal opening, which occurred essentially only at night and was measured by changes in water vapor conductance, progressively decreased as the measurement temperature was raised. The CO2 residual conductance, which describes chlorenchyma properties, had a temperature optimum a few degrees higher than the optimum for net CO2 uptake at all growth temperatures. Nocturnal CO2 uptake and acid accumulation summed over the whole night were maximal for growth temperatures near 25°C/15°C, CO2 uptake decreasing more rapidly than acid accumulation as the growth temperature was raised. At day/night air temperatures that led to substantial nocturnal acid accumulation (25°C/15°C.). 90% saturation of acid accumulation required a higher total daily PAR than at non-optimal growth temperatures (10°C/0°C and 35°C/25°C). Also, the optimal temperature of net CO2 uptake shifted downward when the plants were under drought conditions at all three growth temperatures tested, possibly reflecting an increased fractional importance of respiration at the higher temperatures during drought. Thus, water status, ambient PAR, and growth temperatures must all be considered when predicting the temperature response of gas exchange for O. ficus-indica and presumably for other CAM plants. 相似文献
899.
900.
Nils Ryrholm 《International journal of biometeorology》1988,32(3):205-216
The mothIdaea dilutaria Hübn. (Geometridae) has an isolated population on the Kullaberg peninsula in southern Sweden. Investigations of the local and micro-climate on the peninsula showed that the local distribution range of the moth coincided with the areas of warmest climate, supporting the hypothesis that the Kullaberg poppulation is dependent for its survival on the warm climate of this area and that the species here is a thermal relict from a previously warmer climatic period. 相似文献