全文获取类型
收费全文 | 25704篇 |
免费 | 233篇 |
国内免费 | 164篇 |
专业分类
林业 | 1035篇 |
农学 | 233篇 |
基础科学 | 84篇 |
3580篇 | |
综合类 | 5866篇 |
农作物 | 829篇 |
水产渔业 | 222篇 |
畜牧兽医 | 13324篇 |
园艺 | 141篇 |
植物保护 | 787篇 |
出版年
2016年 | 43篇 |
2015年 | 52篇 |
2014年 | 64篇 |
2013年 | 60篇 |
2012年 | 2167篇 |
2011年 | 2478篇 |
2010年 | 515篇 |
2009年 | 361篇 |
2008年 | 2123篇 |
2007年 | 2177篇 |
2006年 | 1927篇 |
2005年 | 1923篇 |
2004年 | 1794篇 |
2003年 | 1643篇 |
2002年 | 1509篇 |
2001年 | 1013篇 |
2000年 | 1293篇 |
1999年 | 501篇 |
1998年 | 94篇 |
1997年 | 80篇 |
1996年 | 105篇 |
1995年 | 154篇 |
1994年 | 152篇 |
1993年 | 156篇 |
1992年 | 181篇 |
1991年 | 197篇 |
1990年 | 198篇 |
1989年 | 162篇 |
1988年 | 183篇 |
1987年 | 193篇 |
1986年 | 156篇 |
1985年 | 128篇 |
1984年 | 165篇 |
1983年 | 144篇 |
1982年 | 115篇 |
1981年 | 84篇 |
1980年 | 77篇 |
1979年 | 76篇 |
1978年 | 37篇 |
1976年 | 46篇 |
1974年 | 43篇 |
1973年 | 35篇 |
1970年 | 40篇 |
1963年 | 69篇 |
1960年 | 40篇 |
1959年 | 44篇 |
1958年 | 44篇 |
1957年 | 69篇 |
1954年 | 40篇 |
1953年 | 37篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
Forterre F Konar M Tomek A Doherr M Howard J Spreng D Vandevelde M Jaggy A 《Journal of the American Veterinary Medical Association》2008,232(4):559-563
OBJECTIVE: To evaluate the accuracy of neurologic examination versus magnetic resonance imaging (MRI) in localization of cervical disk herniation and evaluate the usefulness of withdrawal reflex testing in dogs. DESIGN: Retrospective case series. ANIMALS: 35 client-owned dogs with a single-level cervical disk herniation as determined via MRI. PROCEDURES: 1 of 2 board-certified neurologists performed a complete neurologic examination in each dog. Clinical signs of a cervical lesion included evidence of neck pain and tetraparesis. The withdrawal reflex was used for neuroanatomic localization (C1-C5 or C6-T2). Agreement between results of neurologic and MRI examinations was determined. RESULTS: Agreement between neurologic and MRI diagnoses was 65.8%. In 11 dogs in which the lesion was clinically localized to the C6-T2 segment on the basis of a decreased withdrawal reflex in the forelimbs, MRI revealed an isolated C1-C5 disk lesion. In 1 dog, in which the lesion was suspected to be at the C1-C5 level, MRI revealed a C6-T2 lesion. Cranial cervical lesions were significantly associated with an incorrect neurologic diagnosis regarding site of the lesion. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that the withdrawal reflex in dogs with cervical disk herniation is not reliable for determining the affected site and that a decreased withdrawal reflex does not always indicate a lesion from C6 to T2. 相似文献
112.
113.
Christiansen E Krokene P Berryman AA Franceschi VR Krekling T Lieutier F Lönneborg A Solheim H 《Tree physiology》1999,19(6):399-403
Norway spruce trees (Picea abies (L.) Karst.) pretreated by wounding and fungal infection showed highly enhanced resistance to a subsequent challenge inoculation with the pathogenic bluestain fungus Ceratocystis polonica (Siem.) C. Moreau. This is the first time the effectiveness of the constitutive and inducible defenses has been shown to depend on prior wounding and infection in conifers, although such acquired resistance has previously been found in several angiosperms. Trees that were pretreated with a combination of 12 bark wounds (1.6 x 10 cm), four fungal inoculations and four sterile inoculations 1-15 days before mass inoculation with C. polonica at 400 inoculations per square meter over a 0.8 m stem section had significantly shorter necroses in the phloem, less bluestained sapwood, and less dead cambium than untreated control trees. Pretreatment with four fungal or sterile inoculations alone did not lead to enhanced resistance. Pretreatment by bark wounding alone seemed to provide an intermediate degree of resistance compared to bark wounding, fungal inoculations and sterile inoculations combined. All trees had a marked increase in the number of resin ducts in the year of inoculation compared with previous years, suggesting that formation of traumatic resin ducts play an important role in the development and maintainance of enhanced resistance. 相似文献
114.
Marie-Etancelin C Basso B Davail S Gontier K Fernandez X Vitezica ZG Bastianelli D Baéza E Bernadet MD Guy G Brun JM Legarra A 《Journal of animal science》2011,89(3):669-679
Genetic parameters of traits related to hepatic lipid metabolism, carcass composition, and product quality of overfed mule ducks were estimated on both parental lines of this hybrid: the common duck line for the maternal side and the Muscovy line for the paternal side. The originality of the statistical model was to include simultaneously the additive genetic effect of the common ducks and that of the Muscovy ducks, revealing a greater genetic determinism in common than in Muscovy. Plasma metabolic indicators (glucose, triglyceride, and cholesterol contents) were heritable, in particular at the end of the overfeeding period, and heritabilities increased with the overfeeding stage. Carcass composition traits were highly heritable in the common line, with values ranging from 0.15 for liver weight, 0.21 for carcass weight, and 0.25 for abdominal fat weight to 0.32 for breast muscle weight. Heritabilities of technological outputs were greater for the fatty liver (0.19 and 0.08, respectively, on common and Muscovy sides for liver melting rate) than for the pectoralis major muscle (between 0.02 and 0.05 on both parental sides for cooking losses). Fortunately, the processing industry is mainly facing problems in liver quality, such as too high of a melting rate, than in meat quality. The meat quality appraisal criteria (such as texture and cooking losses), usually dependent on pH and the rate of decline of pH, were also very lowly heritable. This study demonstrated that genetic determinism of meat quality and ability of overfeeding is not similar in the common population and in the Muscovy population; traits related to fattening, muscle development, and BW have heritability values from 2 to 4 times greater on the common line than on the Muscovy line, which is relevant for considering different selection strategies. 相似文献
115.
Papadogiannakis EI Koutinas AF Saridomichelakis MN Vlemmas J Lekkas S Karameris A Fytianou A 《Veterinary immunology and immunopathology》2005,104(3-4):227-237
Lymphocyte subsets, major histocompatibility complex (MHC)-II expressing cells and number of amastigotes in the epidermis and dermis were investigated immunohistochemically in 48 dogs with patent leishmaniosis, with or without exfoliative dermatitis (ED) to study the immunopathogenesis of this common cutaneous form of the disease. Skin biopsies were obtained and compared for ED sites (group A, n = 26), normal-appearing skin from the same animals (group B, n = 24), and leishmanial dogs not exhibiting ED (group C, n = 22), and normal controls (group D, n = 22). The CD3+, CD45RA+, CD4+, CD8+ (CD8a+), CD21+, and MHC-II+ cells and leishmania amastigotes were identified immunohistochemically and counted with the aid of an image analysis system. Pyogranulomatous to granulomatous dermatitis, expressed in various histopathological patterns, was noticed in all groups A and B and in half of group C dogs. In the epidermis, the low number of T-cells and their subsets did not differ significantly between groups A and B, but CD8+ outnumbered CD4+ lymphocytes in both groups. MHC-II+ expression on epidermal keratinocytes was intense in the skin with and without lesions from dogs with ED but not in group C dogs. CD3+, CD8+ and MHC-II+ cells were fewer in group C compared to group A and B dogs. In the dermis, CD3+ cells in group A animals were mainly represented by the CD8+. CD45RA+ and CD21+ cells were also seen in high numbers. MHC-II expression, potentially in lymphocytes, fibroblasts, dendritic cells, and macrophages was intense. The numbers of all cellular subpopulations in the dermis were significantly different between the groups, being highest in group A and lowest in group D. In sebaceous adenitis sites, CD4+ outnumbered CD8+ cells in contrast to the neighbouring dermis and the epidermis. The number of CD21+ and CD45RA+ cells was much lower in the inflamed sebaceous glands compared to the dermis. Finally, the number of amastigotes in the normal-appearing skin was significantly higher in the ED dogs (group B) than in those not exhibiting this cutaneous form of the disease (group C). 相似文献
116.
Tittarelli M Di Ventura M De Massis F Scacchia M Giovannini A Nannini D Caporale V 《Journal of veterinary medicine. B, Infectious diseases and veterinary public health》2005,52(9):403-409
The authors studied the persistence of infection in 46 ewes experimentally infected with Brucella melitensis biovar 3 and monitored through three subsequent reproductive cycles. The entire experimental period lasted for 151 weeks. Infection of ewes and elimination of Brucella in milk, or its presence in vaginal discharges, persisted throughout the duration of the trial, as demonstrated by recurrent elimination of Brucella in milk and vaginal discharges. Brucella melitensis was recovered from the tissues of one ewe killed at the end of the trial. The strain was recovered from vaginal swabs and milk following parturition in the third reproductive cycle from an ewe that had aborted in the first cycle but was not pregnant in the second cycle. From a public health point of view, the periodical recovery of Brucella from the milk during the entire trial period illustrated that brucellosis in sheep remains a continuous occupational risk and a significant public health problem for consumers of fresh milk and milk products. That risk may persist for at least 3 years following the initial infection of the flock. Lamb antibody titres became negative in all lambs within 5 months after birth. This suggested that serological tests on lambs may have no practical diagnostic significance if performed during the first 5 months of life. Nevertheless, the birth of three infected lambs suggested that the phenomenon of latent carrier state may represent another way for B. melitensis to persist in a flock. 相似文献
117.
Un H Eskiizmirliler S Unal N Freuling CM Johnson N Fooks AR Müller T Vos A Aylan O 《Berliner und Münchener tier?rztliche Wochenschrift》2012,125(5-6):203-208
Following a sustained spill-over event from dogs to foxes, fox rabies spread rapidly in the Aegean region, Turkey. In order to control the outbreak a program of oral vaccination of foxes against rabies was introduced. In the selected vaccination area three annual campaigns between 2008 and 2010 were undertaken during the winter months whereby the vaccine baits were distributed exclusively by plane using a density of 18 baits per km2. Subsequently, fox rabies cases were reported only from locations bordering the non-vaccinated areas. Hence, it was shown that fox rabies control by means of oral rabies vaccination is feasible in Turkey. However, for the progress towards the elimination of fox-mediated rabies in Turkey to be maintained, it is necessary that political and financial support is secured to extend oral vaccination where infected foxes remain. 相似文献
118.
119.
Abstract Cockle, a defect of lamb's pelts, has recently been shown to be associated with infestation of lambs with the louse Bovicoh ovis. The mechanisms by which infestation with the louse leads to cockle are not known, but immunological hypersensitivity has been suggested. The objectives of our work are to determine if lambs respond immunologically to lice and, if so, whether hypersensitivity occurs. Preliminary results are presented here. 相似文献
120.