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41.
David Carpenter 《Agriculture and Human Values》2003,20(2):165-176
A conceptual framework influenced bythe concept of moral ecology is developed andused to analyze the transition fromtechnological (green revolution) to ecological(organic) rice farming by resource poor farmersfrom the Philippine island of Bohol. This MoralEcology Framework (MEF) focuses on theepistemology of the two farming systems and howthis influences management principles andpractice. The orienting concepts of systemic understanding, exchange betweensociety and the environment, local versusextra-local exchange and scope areintegral to this analysis. The case studydemonstrates how the ostracism of nature underthe green revolution coupled with itsinflexible production options affected thesustainability of some local rice farmingsystems. Whereas the transition to organicfarming and the concomitant incorporation ofecological processes and more flexibleproduction options has allowed local farmers toenhance the sustainability of their farmingsystems by altering the exchange processeswithin the socio-ecological system. 相似文献
42.
Diffusion of radon and thoron from the Ilunar surface provides a mechanism for production of a radioactive surface layer on the moon. If the radon and thoron flux from the lunar surface is equal to that measured at the earth's surface, the equilibrium activity of this surface layet is estimated as approximately 1 microcurie per square meter, due to radon and its decay products. This activity consists of alpha particles and gamnmna rays at well-defined energies and of beta rays. 相似文献
43.
EA Adelberg 《Science (New York, N.Y.)》1964,146(3648):1193-1195
44.
Ecosystem experiments 总被引:1,自引:0,他引:1
Carpenter SR Chisholm SW Krebs CJ Schindler DW Wright RF 《Science (New York, N.Y.)》1995,269(5222):324-327
Experimental manipulations of entire ecosystems have been conducted in lakes, catchments, streams, and open terrestrial and marine environments. Experiments have addressed applied problems of ecosystem management and complex responses of communities and ecosystems to perturbations. In the course of some experiments, environmental indicators and models have been developed and tested. Surprising results with implications for ecological understanding and management are common. 相似文献
45.
Venus may rotate in a direction opposite to that of the earth at a rate of only one revolution in 240 days. The estimated period is accurate within 20 percent if the axis of rotation of Venus is perpendicular to the plane of the planet's orbit. 相似文献
46.
The neural encoding of serial order was studied in the motor cortex of monkeys performing a context-recall memory scanning task. Up to five visual stimuli were presented successively on a circle (list presentation phase), and then one of them (test stimulus) changed color; the monkeys had to make a single motor response toward the stimulus that immediately followed the test stimulus in the list. Correct performance in this task depends on memorization of the serial order of the stimuli during their presentation. It was found that changes in neural activity during the list presentation phase reflected the serial order of the stimuli; the effect on cell activity of the serial order of stimuli during their presentation was at least as strong as the effect of motor direction on cell activity during the execution of the motor response. This establishes the serial order of stimuli in a motor task as an important determinant of motor cortical activity during stimulus presentation and in the absence of changes in peripheral motor events, in contrast to the commonly held view of the motor cortex as just an "upper motor neuron." 相似文献
47.
48.
Carpenter RA 《Science (New York, N.Y.)》1976,191(4228):665-668
The tensions between availability of materials and quality of the environment will increase with economic growth and the appreciation of environmental values. These tensions can be relieved to an extent by internalizing the costs of environmental protection so that they are reflected in the price of materials. Economic incentives and disincentives, such as effluent fees, are receiving renewed attention (5, pp. 49-51). In addition, government regulation to protect the environment will, perhaps arbitrarily, affect the availability and use of materials. The report, Man, Materials, and Environment (5, p. 25), concluded that: A national materials policy should be based upon the principle that calculations of benefits and costs associated with the extraction, transport, processing, use, and disposal of materials should take full account of the value of common property resources and of any change in the value of common properties resulting from the impact of materials on the environment; and should support the principle that those responsible for impairment of the environment should bear the costs of damage or repair. These principles should become a commonplace element of property rights, legislation, and administrative practice at all levels of government. The difficulty of measuring benefits and costs should not delay adoption of these principles but suggests the need for continuous observation and experimentation. Environmental protection regulations will result in: (i) increased costs for many materials; (ii) disruptive changes in use of materials, due to environmental characteristics and revised cost effectiveness calculations; (iii) restrictions on the siting of processing and manufacturing installations; (iv) preemption of access and surface rights to some mineral bearing lands, particularly those that are federally controlled; (v) diversion of capital from new production facilities; and (vi) frustrating delays in decisions, such as those affecting leasing and plant siting. In return for these generally undesirable disruptions in the continued development and supply of materials, society will obtain: (i) improved quality of air and water; (ii) long-term protection of the natural ecosystems of which man is a part; (iii) more efficient allocation of natural resources on the basis of more accurate and complete accounting of costs; (iv) improved human health through decreased contamination of the environment with toxic substances; and (v) conservation of materials through a closing of the production, use, and disposal cycle. Ingenuity and a more complete understanding of the parts and interactions of the energy, materials, and environment system can do much to reduce the tensions in these conflicts and bring about equitable trade-offs among societal goals. 相似文献
49.
Carpenter BK 《Science (New York, N.Y.)》2011,332(6035):1269-1270
50.
Brown PG Hildebrand AR Zolensky ME Grady M Clayton RN Mayeda TK Tagliaferri E Spalding R MacRae ND Hoffman EL Mittlefehldt DW Wacker JF Bird JA Campbell MD Carpenter R Gingerich H Glatiotis M Greiner E Mazur MJ McCausland PJ Plotkin H Rubak Mazur T 《Science (New York, N.Y.)》2000,290(5490):320-325
The preatmospheric mass of the Tagish Lake meteoroid was about 200,000 kilograms. Its calculated orbit indicates affinity to the Apollo asteroids with a semimajor axis in the middle of the asteroid belt, consistent with a linkage to low-albedo C, D, and P type asteroids. The mineralogy, oxygen isotope, and bulk chemical composition of recovered samples of the Tagish Lake meteorite are intermediate between CM and CI meteorites. These data suggest that the Tagish Lake meteorite may be one of the most primitive solar system materials yet studied. 相似文献