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41.
Bigas A Garrido ME de Rozas AM Badiola I Barbé J Llagostera M 《Veterinary microbiology》2005,105(3-4):223-228
Haemophilus parasuis is a member of the family Pasteurellaceae and an important respiratory-tract pathogen of swine, which is the etiological agent of Glasser's disease. Because no genetic manipulation system is available for H. parasuis so far, in vivo studies about the role of its genes involved in virulence are unfeasible. Here we demonstrate that H. parasuis has a cyclic AMP (cAMP)-dependent natural transformation system that enables the uptake of DNA in which the ACCGAACTC sequence signal must be present. After improving DNA transformation parameters, such as cAMP and DNA concentration and exposition time of the exogenous DNA, a knockout mutant of H. parasuis defective in the thy gene, encoding the thymidylate synthase enzyme, has been constructed. Data presented in this work open the possibility for the functional analysis of genes involved in the infectious process of this animal pathogen. 相似文献
42.
Jordi Marsal Merce Mata Jesus del Campo Amadeu Arbones Xavier Vallverdú Joan Girona Natalia Olivo 《Irrigation Science》2008,26(4):347-356
The use of partial root-drying (PRD) irrigation implies doubling pipelines instead of using a conventional single pipeline.
However, pipelines can be spaced a short distance apart (e.g. 1 m) along the vine row (“D” layout) or joined with cable ties
and laid as a single pipeline (“S” layout). Pipelines in “S” configuration are laid under the vine row, and in “D” at both
sides of the vine row. These two different layouts can change the wetted soil zone and affect grapevine response to irrigation.
The focus of this study was therefore on establishing the role of pipeline layout in vine-grape (cv. ‘Tempranillo’) response
under semi-arid conditions in which PRD is managed as a deficit irrigation technique. Six irrigation treatments were applied,
which resulted from the combination of Control (C, full irrigation), PRD and seasonal sustained deficit irrigation (SSDI),
and “S” and “D” pipeline layouts. SSDI and PRD were irrigated to 50% C throughout the irrigation season, and C irrigation
was scheduled according to a crop water balance technique. Midday stem water potential (Ψstem) and leaf conductance (gl) indicated that, on the whole, PRD treatments had a slightly higher water status than SSDI treatments, but a substantially
lower status than C treatments. Use of the “D” pipeline layout significantly reduced Ψstem in both PRD and SSDI treatments and in some instances for Control conditions, too. Berry yield, vine intercepted radiation,
leaf abscisic acid (ABA) and gl were highly correlated with Ψstem. Differences in water status between PRD-S and SSDI-S, according to a sub-surface irrigation test, seemed to be more related
to changes in soil evaporation losses and irrigation efficiency than to any intrinsic PRD effect. PRD-S accounted for water
savings equivalent to 10% according to the ratio between applied water and grape production for the SSDI-S treatment, whereas
PRD-D berry yield was not significantly different from that associated with the SSDI-S treatment. In conclusion, under the
growing conditions of this experiment, PRD-S offered the possibility of slightly improving water conservation when irrigation
was applied to the soil surface. 相似文献
43.
Joan Girona Jesus del Campo Merce Mata Gerardo Lopez Jordi Marsal 《Irrigation Science》2011,29(1):55-63
A five-year experiment (2002–2006) was conducted to determine apple (cv ‘Golden Smoothee’) and pear (cv ‘Conference’) crop
coefficients (Kc) using two large weighing lysimeters. Daily reference evapotranspiration (ETo) and crop evapotranspiration
(ETc) were evaluated. Midday canopy light interception of both crops planted in hedgerows, 4 × 1.6 m, was determined on a
weekly basis from bud-break until leaf fall from year 2002 (fourth after planting) to year 2006 of both plantations. Relationships
between canopy light interception and calculated Kc (ETc/ETo) were evaluated from bud-break until harvest. There were differences
in Kc values between apple and pear trees. When daily Kc values from bud-break until harvest were adjusted to hyperbolic functions
each year, adjusted curves for pear trees were very similar regardless of year (maximum Kc around 1.0). In apple trees, the
maximum values of Kc increased over time, from 0.49 in 2002 to 1.04 in 2006. Midday light interception in both apple and pear
trees increased during the 5 years of experiment from 29.0 to 45.6% in apples and from 27.5 to 41.6% in pears in midsummer.
Although there was a significant positive correlation between midday canopy light interception and Kc in apple and pear trees,
in different times within a specific year, these relationships were different between crops. While the apple data fitted into
the same equation regardless of the year, different equations were needed to fit the pear data in different years. This discrepancy
may have been related to differences in the canopy properties between apple and pear trees. Pear canopies had higher porosity
than apple canopies and thus improved light penetration. Apple trees were more vigorous and produced taller and denser canopies.
Pear Kc values were greatly influenced by the evaporative demands of different years and consequently differences in midday
canopy light interception did not adequately reflect the differences in Kc across the two species. 相似文献
44.
Jordi Marsal Jaume Casadesus Gerardo Lopez Merce Mata Joaquim Bellvert Joan Girona 《Irrigation Science》2016,34(3):201-208
The level of irrigation restriction to apply in a deficit irrigation (DI) programme for sustainable peach (‘Baby gold 6’) production was investigated. The experiment involved four irrigation treatments over five consecutive seasons (2007–2011). They were full irrigation (control), reducing irrigation by 20 % during the first half of stage III (DI-80 %), withholding irrigation until reaching a light stress level (DI-L) and withholding irrigation until reaching a moderate stress level (DI-M). The withholding of irrigation in both DI-L and DI-M was applied only during stage II and postharvest periods and was based on midday stem water potential thresholds (Ψ stem). For the DI-L treatment ?1.5 MPa was used in both periods, and for DI-M ?1.8 and ?2.0 MPa were used during stage II and postharvest, respectively. Average Ψ stem values during DI periods were approximately ?1.4 and ?1.2 MPa for DI-M and DI-L, respectively. The pre-defined thresholds required to trigger irrigation were rarely reached. No significant differences between treatments were found in terms of yield in any experimental year. However, DI-M and to a lesser extent DI-L had lower final fruit fresh mass at harvest related to lower Ψ stem after three consecutive years of the experiment (during 2010 and 2011). Therefore, in terms of fruit size, DI was not sustainable. Rather than lowering Ψ stem thresholds, we recommend discontinuing DI after 3-year application. 相似文献
45.
African origins of the domestic donkey 总被引:1,自引:0,他引:1
46.
Vilaró F Pérez-Hedo M Eras J Canela R Eizaguirre M 《Journal of agricultural and food chemistry》2012,60(12):3020-3025
The juvenile hormones (JHs) have been considered the most versatile hormones in the animal kingdom. JH-II is the most abundant JH in Sesamia nonagrioides, important maize pests in the Mediterranean basin. This study compared the sensitivities and matrix effects of four ionization modes on analyzing JH-II in S. nonagrioides hemolymph using ultrahigh-performance liquid chromatography-mass spectrometry (UHPLC-MS) in single ion monitoring (SIM) mode. The ionization techniques tested were electrospray ionization (ESI), atmospheric pressure chemical ionization (APCI), atmospheric pressure photoionization (APPI), and APPI with the lamp turned off, which corresponds to atmospheric pressure thermospray ionization (APTSI). ESI was discarded because of the high matrix effect. APPI was discarded because the correlation responses between solvent and matrix on the instrumental quality parameters were worse than those for APTSI and APCI. In our analytical conditions, APCI has shown the best validation parameter values. APCI ionization is widely available in instrumental laboratories. 相似文献
47.
Gömöry F Solovyov M Souc J Navau C Prat-Camps J Sanchez A 《Science (New York, N.Y.)》2012,335(6075):1466-1468
Invisibility to electromagnetic fields has become an exciting theoretical possibility. However, the experimental realization of electromagnetic cloaks has only been achieved starting from simplified approaches (for instance, based on ray approximation, canceling only some terms of the scattering fields, or hiding a bulge in a plane instead of an object in free space). Here, we demonstrate, directly from Maxwell equations, that a specially designed cylindrical superconductor-ferromagnetic bilayer can exactly cloak uniform static magnetic fields, and we experimentally confirmed this effect in an actual setup. 相似文献
48.
J. Pablo Fernndez-Trujillo Javier M. Obando-Ulloa Juan A. Martínez Eduard Moreno Jordi García-Mas Antonio J. Monforte 《Postharvest Biology and Technology》2008,50(2-3):125-134
A set of near-isogenic lines (NILs) of melon (Cucumis melo L.) was used to test the relationship between the climacteric pattern and postharvest disorders at harvest and after 30 days at 8 °C. The NILs contained different chromosome introgressions in the linkage group III from the non-climacteric exotic Korean accession PI 161375 transferred into the genetic background of the non-climacteric Spanish cultivar ‘Piel de Sapo’ (PS). A quantitative trait locus (QTL) in this linkage group induced climacteric behavior in eight NILs accompanied by a peak of ethylene production and fruit dehiscence to different degrees. The cultivar ‘Nicolás’ and one NIL showed a non-climacteric pattern of respiration rate and ethylene production. The climacteric NILs were used to test the relationship between this pattern and postharvest disorders. The reference climacteric lines ‘Fado’ and ‘Védrantais’ were more sensitive to CI and associated Cladosporium rot than the NILs or PS. In general, a more intense climacteric behavior was accompanied by fruit dehiscence, and higher total losses and greater skin scald after storage, than in PS. A higher incidence of chilling injury (CI) in the climacteric NILs was found compared with the non-climacteric ones, although with exceptions (one NIL for CI in the form of scald; the same NIL and one more for pitting). The climacteric onset and netting scald were not related, and CI in the form of skin spots was only found in climacteric NILs and was positively correlated with the maximum peak of ethylene production. Some climacteric NILs did not follow the rule of a higher susceptibility to other disorders and decay after storage compared with PS, such as for example in fruit over-ripening (detected externally or internally), Cladosporium rot at the peduncle and Alternaria rot. Mealiness was independent of climacteric behavior. Three climacteric NILs obtained better flavor scores after storage than PS, although the maximum peak of ethylene production was positively correlated with off-flavor. Genotypic correlation between disorder data and the physiological data of climacteric fruit revealed positive (flavor index) or negative postharvest consequences (skin injuries, rots or off-flavors). At least one QTL can be assigned to most of the quality traits analyzed. 相似文献
49.
Weikum WM Vouloumanos A Navarra J Soto-Faraco S Sebastián-Gallés N Werker JF 《Science (New York, N.Y.)》2007,316(5828):1159
This study shows that 4- and 6-month-old infants can discriminate languages (English from French) just from viewing silently presented articulations. By the age of 8 months, only bilingual (French-English) infants succeed at this task. These findings reveal a surprisingly early preparedness for visual language discrimination and highlight infants' selectivity for retaining only necessary perceptual sensitivities. 相似文献
50.
Süel GM Kulkarni RP Dworkin J Garcia-Ojalvo J Elowitz MB 《Science (New York, N.Y.)》2007,315(5819):1716-1719
The dynamic process of differentiation depends on the architecture, quantitative parameters, and noise of underlying genetic circuits. However, it remains unclear how these elements combine to control cellular behavior. We analyzed the probabilistic and transient differentiation of Bacillus subtilis cells into the state of competence. A few key parameters independently tuned the frequency of initiation and the duration of competence episodes and allowed the circuit to access different dynamic regimes, including oscillation. Altering circuit architecture showed that the duration of competence events can be made more precise. We used an experimental method to reduce global cellular noise and showed that noise levels are correlated with frequency of differentiation events. Together, the data reveal a noise-dependent circuit that is remarkably resilient and tunable in terms of its dynamic behavior. 相似文献