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81.
Social insects live in societies that include both reproductive and nonreproductive adults. Understanding the factors that determine which individuals become successful reproductives is necessary to explain the evolution of these societies. The phenotypic effects of the gene Pgm-3 (or a closely linked gene) that may cause workers of the fire ant Solenopsis invicta to selectively execute all queens of a specific genotype were investigated. These effects, which involve differences in queen reproductive development, are expressed only in colonies exhibiting a particular type of social organization (multiple-queen colonies), and it is only in such colonies that selective execution on the basis of genotype occurs. This is an unusual example of genotype-environment interaction in gene expression in which the environmental component is the social environment. The queens executed are, surprisingly, those with the greatest reproductive development. Thus, there is a counterintuitive relation between the potential and realized reproductive success of queens in multiple-queen societies of this ant. 相似文献
82.
Keller HU Jorda L Küppers M Gutierrez PJ Hviid SF Knollenberg J Lara LM Sierks H Barbieri C Lamy P Rickman H Rodrigo R 《Science (New York, N.Y.)》2005,310(5746):281-283
The OSIRIS cameras (optical, spectroscopic, and infrared remote imaging system) onboard the European Space Agency's Rosetta spacecraft observed comet 9P/Tempel 1 for 17 days continuously around the time of NASA's Deep Impact mission. The cyanide-to-water production ratio was slightly enhanced in the impact cloud, compared with that of normal comet activity. Dust particles were flowing outward in the coma at >160 meters per second, accelerated by the gas. The slope of the brightness increase showed a dip about 200 seconds after the impact. Dust Afrho values before and long after the impact confirm the slight decrease of cometary activity. The dust-to-water mass ratio was much larger than 1. 相似文献
83.
The three-dimensional structure of canine parvovirus and its functional implications 总被引:59,自引:0,他引:59
J Tsao M S Chapman M Agbandje W Keller K Smith H Wu M Luo T J Smith M G Rossmann R W Compans 《Science (New York, N.Y.)》1991,251(5000):1456-1464
The three-dimensional atomic structure of a single-stranded DNA virus has been determined. Infectious virions of canine parvovirus contain 60 protein subunits that are predominantly VP-2. The central structural motif of VP-2 has the same topology (an eight-stranded antiparallel beta barrel) as has been found in many other icosahedral viruses but represents only about one-third of the capsid protein. There is a 22 angstrom (A) long protrusion on the threefold axes, a 15 A deep canyon circulating about each of the five cylindrical structures at the fivefold axes, and a 15 A deep depression at the twofold axes. By analogy with rhinoviruses, the canyon may be the site of receptor attachment. Residues related to the antigenic properties of the virus are found on the threefold protrusions. Some of the amino termini of VP-2 run to the exterior in full but not empty virions, which is consistent with the observation that some VP-2 polypeptides in full particles can be cleaved by trypsin. Eleven nucleotides are seen in each of 60 symmetry-related pockets on the interior surface of the capsid and together account for 13 percent of the genome. 相似文献
84.
Vitamin D and sterol composition of 10 types of mushrooms from retail suppliers in the United States
Phillips KM Ruggio DM Horst RL Minor B Simon RR Feeney MJ Byrdwell WC Haytowitz DB 《Journal of agricultural and food chemistry》2011,59(14):7841-7853
Vitamin D(2) (ergocalciferol) and sterols were analyzed in mushrooms sampled nationwide in the United States to update the USDA Nutrient Database for Standard Reference. Vitamin D(2) was assayed using HPLC with [(3)H]-vitamin D(3) internal standard and sterols by GC-FID mass spectrometric (MS) confirmation. Vitamin D(2) was low (0.1-0.3 μg/100 g) in Agaricus bisporus (white button, crimini, portabella) and enoki, moderate in shiitake and oyster (0.4-0.7 μg/100 g), and high in morel, chanterelle, maitake (5.2-28.1 μg/100 g) and UV-treated portabella (3.4-20.9 μg/100 g), with significant variability among composites for some types. Ergosterol (mg/100 g) was highest in maitake and shiitake (79.2, 84.9) and lowest in morel and enoki (26.3, 35.5); the range was <10 mg/100 g among white button composites but 12-50 mg/100 g among samples of other types. All mushrooms contained ergosta-5,7-dienol (22,23-dihydroergosterol) (3.53-18.0 mg/100 g) and (except morel) ergosta-7-enol. Only morel contained brassicasterol (28.6 mg/100 g) and campesterol (1.23-4.54 mg/100 g) and no ergosta-7,22-dienol. MS was critical in distinguishing campesterol from ergosta-7,22-dienol. 相似文献
85.
Simon RR Phillips KM Horst RL Munro IC 《Journal of agricultural and food chemistry》2011,59(16):8724-8732
This study compared the compositional changes in mushrooms exposed to sunlight with those occurring after commercial ultraviolet (UV) light processing. Button mushrooms (75 kg) were processed in the presence or absence of UVB light; a third group was exposed to direct sunlight. Mushroom composition was evaluated using chemical analyses. Vitamin D concentrations were 5, 410, and 374 μg/100 g (dw) in control, UVB, and sunlight groups, respectively. On a dry weight basis, no significant changes in vitamin C, folate, vitamins B(6), vitamin B(5), riboflavin, niacin, amino acids, fatty acids, ergosterol, or agaritine were observed following UVB processing. Sunlight exposure resulted in a 26% loss of riboflavin, evidence of folate oxidation, and unexplained increases in ergosterol (9.5%). It was concluded that compositional effects of UVB light are limited to changes in vitamin D and show no detrimental changes relative to natural sunlight exposure and, therefore, provide important information relevant to the suitability and safety of UVB light technology for vitamin D enhanced mushrooms. 相似文献
86.
Objective To determine if feline lacrimal glands, glands of the third eyelid, corneas, and corneal sequestra contain porphyrins, which could be responsible for the brown/amber discoloration of corneal sequestra and tears in affected cats. Procedures Samples of grossly normal cornea, lacrimal gland, gland of the third eyelid, and sequestra obtained via keratectomy were collected. Porphyrin concentrations of the homogenate were determined by spectrofluorometry with protoporphyrin IX and coproporphyrin III dihydrochloride used as standards. A hamster harderian gland was used as a positive control. Results Normal tissues were harvested from one eye each of 14 nonclient owned, adult, mixed‐breed, short‐hair cats euthanized for reasons not associated with this study. Eighteen sequestra were acquired from cats undergoing unilateral lamellar keratectomies. Breeds of the affected cats included eight Himalayan, five domestic shorthair, and one each of four other breeds. Only the positive control and standards contained levels of porphyrins above background. All feline samples examined were histologically normal with no evidence of porphyrins. Conclusions Porphyrins are absent in normal feline lacrimal glands, corneas, and corneal sequestra. Porphyrins do not appear to be the cause of the brown/amber color of feline corneal sequestra. 相似文献
87.
Disseminated infection with Histoplasma capsulatum was diagnosed in a 7-yr-old female Bengal tiger (Panthera tigris). Clinical signs were nonspecific with the exception of brief periods of tachypnea for 5 days prior to death. H. capsulatum organisms were found in the lungs, tracheobronchial lymph nodes, and liver. Diagnosis was confirmed by tracheal wash, urine H. capsulatum enzyme immunoassay, and necropsy results. This report represents the first published account of disseminated histoplasmosis in a tiger. 相似文献
88.
Assessment of NH3 emissions after application of cattle slurry Over a two year period at different sites following application of cattle slurry measurements of NH3 emissions have been carried out using the Integrated Horizontal Flux Method. The objective of these studies was to quantify NH3 losses under field conditions and to investigate the influence of various environmental factors on the NH3 emission. Depending on environmental conditions and infiltration rates NH3 volatilization losses in the described experiments ranged from 12 to 65 per cent of the applied NH4-N. Of the many factors influencing NH3 emission three factors were chosen which can easily be measured or at least estimated. Using these factors a framework for an assessment of NH3 emissions has been set up. Within this framework the expected NH3 losses are estimated depending on infiltration rate of the slurry, mean aerial temperature, precipitation and time after application (with or without incorporation of manure). This framework offers a practical tool for evaluation of NH3 losses after application of cattle slurry and may be used to avoid NH3 losses under different environmental conditions. 相似文献
89.
Field experiments under various conditions were carried out in Hohenheim and the Allgäu to measure the effects of liquid manure properties and meteorological factors on ammonia losses. The micrometeorological method (IHF) and the wind tunnel method were used. Depending on the prevailing conditions the ammonia losses varied between 14 and 99% of the applied ammonium nitrogen. The relationship between the ammonia loss and the logarithm of the dry matter content of liquid manure was highly significant. The dry matter content also influenced the time course of the ammonia loss. Solar radiation was the other major factor affecting ammonia loss. Compared to dry matter content and-solar radiation, effects of other factors such as ammonium content and pH of liquid manure, air temperature, relative humidity and wind speed were small in the given range tested. Based on the relationships between the various parameters a simple model for estimation of ammonia loss was developed. 相似文献
90.