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211.
Isberg J Hammersberg J Johansson E Wikström T Twitchen DJ Whitehead AJ Coe SE Scarsbrook GA 《Science (New York, N.Y.)》2002,297(5587):1670-1672
Room-temperature drift mobilities of 4500 square centimeters per volt second for electrons and 3800 square centimeters per volt second for holes have been measured in high-purity single-crystal diamond grown using a chemical vapor deposition process. The low-field drift mobility values were determined by using the time-of-flight technique on thick, intrinsic, freestanding diamond plates and were verified by current-voltage measurements on p-i junction diodes. The improvement of the electronic properties of single-crystal diamond and the reproducibility of those properties are encouraging for research on, and development of, high-performance diamond electronics. 相似文献
212.
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214.
Eduardo Fraga‐Manteiga Darren J. Shaw Sophie Dennison Andrew Brownlow Tobias Schwarz 《Veterinary radiology & ultrasound》2014,55(4):393-398
Computed tomography (CT) is commonly used to assess animals with head trauma. However, strongly attenuating objects such as metallic gunshot cause artifacts that may make accurate localization of shrapnel pieces difficult. The purpose of this study was to develop an optimized CT protocol for minimizing metal artifacts in an animal model of gunshot head trauma. A cadaver head of a stranded Gray seal (Halichoerus grypus) was shot post‐mortem with a 0.223‐inch caliber rifle. The head was frozen, thawed, and scanned using a multislice CT scanner and protocols with varying acquisition and reconstruction parameters. Scans were acquired with and without use of the scanner's proprietary Extended CT Scale (ECTS) mode and beam hardening reduction (Posterior Fossa Optimization [PFO]) filter. Window/level display settings were also varied. For each protocol and each of five selected metallic shrapnel pieces, a single observer measured combined metal halo artifact and shrapnel area using a hand‐traced region of interest. The number of hypo‐ and hyper‐attenuating streak artifacts was also recorded. Measurements were repeated for three different reading sessions. Metal CT artifacts were minimized with a high‐frequency image reconstruction algorithm and a wide window setting. Further artifact reduction was achieved with a proprietary ECTS raw data reconstruction technique and a very wide window. This enabled a more confident evaluation of surrounding bone. On the other hand, these techniques are unfortunately not effective under conditions of soft tissue evaluation. Increasing tube voltage and use of a proprietary PFO filter did not yield a significant reduction in metal artifacts. 相似文献
215.
Precision Agriculture - Many farmers hesitate to adopt new management strategies with actual or perceived risks and uncertainties. Especially in ornamental plant production, farmers often stick to... 相似文献
216.
Conservation: limits of land sparing 总被引:1,自引:0,他引:1
Fischer J Batáry P Bawa KS Brussaard L Chappell MJ Clough Y Daily GC Dorrough J Hartel T Jackson LE Klein AM Kremen C Kuemmerle T Lindenmayer DB Mooney HA Perfecto I Philpott SM Tscharntke T Vandermeer J Wanger TC Von Wehrden H 《Science (New York, N.Y.)》2011,334(6056):593; author reply 594-593; author reply 595
217.
Pimentel-Elardo SM Buback V Gulder TA Bugni TS Reppart J Bringmann G Ireland CM Schirmeister T Hentschel U 《Marine drugs》2011,9(10):1682-1697
Four new tetromycin derivatives, tetromycins 1-4 and a previously known one, tetromycin B (5) were isolated from Streptomyces axinellae Pol001(T) cultivated from the Mediterranean sponge Axinella polypoides. Structures were assigned using extensive 1D and 2D NMR spectroscopy as well as HRESIMS analysis. The compounds were tested for antiparasitic activities against Leishmania major and Trypanosoma brucei, and for protease inhibition against several cysteine proteases such as falcipain, rhodesain, cathepsin L, cathepsin B, and viral proteases SARS-CoV M(pro), and PL(pro). The compounds showed antiparasitic activities against T. brucei and time-dependent inhibition of cathepsin L-like proteases with K(i) values in the low micromolar range. 相似文献
218.
Miriam M. Shanaman Tobias Schwarz Arnon Gal Robert T. O'Brien 《Veterinary radiology & ultrasound》2013,54(6):591-604
Contrast‐enhanced multi‐detector computed tomography (CE‐MDCT) is used routinely in evaluating human patients with acute abdominal symptoms. Contrast‐enhanced ultrasound (CEUS) continues to be in its infancy as it relates to evaluation of the acute abdomen. The purpose of this study was to compare survey radiography, B‐mode ultrasound, CEUS, and CE‐MDCT findings in canine patients presenting with acute abdominal signs; with a focus on the ability to differentiate surgical from non‐surgical conditions. Nineteen dogs were prospectively enrolled. Inclusion required a clinical diagnosis of acute abdominal signs and confirmed surgical or non‐surgical causes for the clinical signs. Agreement for the majority of recorded imaging features was at least moderate. There was poor agreement in the identification of pneumoperitoneum and in the comparison of pancreatic lesion dimensions for B‐mode vs. CEUS. The CT feature of fat stranding was detected in cases including, but not limited to, gastric neoplasia with perforation, pancreatitis, and small intestinal foreign body. Ultrasound underestimated the size and number of specific lesions when compared with CE‐MDCT. Contrast‐enhanced ultrasound was successful in detecting bowel and pancreatic perfusion deficits that CE‐MDCT failed to identify. Accuracy for differentiation of surgical vs. non‐surgical conditions was high for all modalities; 100%, 94%, and 94% for CE‐MDCT, ultrasonography and survey radiography respectively. Findings indicated that CE‐MDCT is an accurate screening test for differentiating surgical from non‐surgical acute abdominal conditions in dogs. Focused CEUS following CE‐MDCT or B‐mode ultrasonography may be beneficial for identifying potentially significant hypoperfused lesions. 相似文献
219.
Edward P. Wilhelm Margaret I. Boulton Tobias E. S. Barber Andy J. Greenland Wayne Powell 《Plant Breeding》2013,132(6):539-545
In wheat, semidwarfism resulting from reduced height (Rht)‐B1b and Rht‐D1b was integral to the ‘green revolution’. The principal donors of these alleles are ‘Norin 10’, ‘Seu Seun 27’ and ‘Suwon 92’ that, according to historical records, inherited semidwarfism from the Japanese landrace ‘Daruma’. The objective of this study was to examine the origins of Rht‐B1b and Rht‐D1b by growing multiple seed bank sources of cultivars comprising the historical pedigrees of the principal donor lines and scoring Rht‐1 genotype and plant height. This revealed that ‘Norin 10’ and ‘Suwon 92’ sources contained Rht‐B1b and Rht‐D1b, but the ‘Seu Seun 27’ source did not contain a semidwarf allele. Neither Rht‐B1b nor Rht‐D1b could be definitively traced back to ‘Daruma’, and both ‘Daruma’ sources contained only Rht‐B1b. However, ‘Daruma’ remains the most likely donor of Rht‐B1b and Rht‐D1b. We suggest that the disparity between historical pedigrees and Rht‐1 genotypes occurs because the genetic make‐up of seed bank sources differs from that of the cultivars actually used in the pedigrees. Some evidence also suggests that an alternative Rht‐D1b donor may exist. 相似文献
220.
Tobias O. Okeno Isaac S. Kosgey Alexander K. Kahi 《Tropical animal health and production》2010,42(6):1073-1079
Cost-benefit analysis using net present value (NPV) as the economic evaluation criterion was used to investigate the economic
merits of four breeding strategies used for genetic improvement of dairy cattle in Kenya. The breeding strategies were evaluated
over a 25-year period. The costs involved in setting up and running each strategy were obtained from large-scale dairy cattle
farms, and government and private institutions involved in genetic improvement of dairy cattle. Only benefits from genetic
improvement were considered. The impact on NPV due to changes in genetic and economic parameters was investigated. The ranking
of the breeding strategies greatly differed with genetic ranking. Among the local selection programs, a strategy utilizing
young bulls, sons of local bulls, was more profitable than one utilizing old progeny tested bulls. Continuous semen importation
was not an economically viable alternative. The strategy utilizing young bulls progeny of imported bulls (PIB) was only viable
if imports were from countries which are >2.00 SD in genetic merit above the local dairy cattle population. The ranking of
strategies was not sensitive to changes in genetic parameters but to economic parameters. The use of local semen from young
bulls progeny of local proven bulls is recommended. Alternatively, PIB can be utilized but the semen will have to be imported
from countries which are >2.00 SD above the local dairy cattle population or the cost of imported semen should be ≤ US$40
per straw. 相似文献