全文获取类型
收费全文 | 204014篇 |
免费 | 10340篇 |
国内免费 | 152篇 |
专业分类
林业 | 8962篇 |
农学 | 6399篇 |
基础科学 | 1232篇 |
25184篇 | |
综合类 | 35583篇 |
农作物 | 8131篇 |
水产渔业 | 9781篇 |
畜牧兽医 | 103347篇 |
园艺 | 2724篇 |
植物保护 | 13163篇 |
出版年
2018年 | 2823篇 |
2017年 | 3156篇 |
2016年 | 2918篇 |
2015年 | 2422篇 |
2014年 | 3114篇 |
2013年 | 7989篇 |
2012年 | 5599篇 |
2011年 | 6955篇 |
2010年 | 4542篇 |
2009年 | 4609篇 |
2008年 | 6825篇 |
2007年 | 6549篇 |
2006年 | 6065篇 |
2005年 | 5635篇 |
2004年 | 5385篇 |
2003年 | 5496篇 |
2002年 | 4971篇 |
2001年 | 5935篇 |
2000年 | 6031篇 |
1999年 | 4820篇 |
1998年 | 2090篇 |
1997年 | 2002篇 |
1995年 | 2257篇 |
1994年 | 1940篇 |
1993年 | 1856篇 |
1992年 | 3815篇 |
1991年 | 4030篇 |
1990年 | 4027篇 |
1989年 | 4028篇 |
1988年 | 3664篇 |
1987年 | 3627篇 |
1986年 | 3723篇 |
1985年 | 3645篇 |
1984年 | 2995篇 |
1983年 | 2708篇 |
1982年 | 1856篇 |
1979年 | 2973篇 |
1978年 | 2377篇 |
1977年 | 2030篇 |
1976年 | 2088篇 |
1975年 | 2239篇 |
1974年 | 2728篇 |
1973年 | 2727篇 |
1972年 | 2642篇 |
1971年 | 2420篇 |
1970年 | 2351篇 |
1969年 | 2355篇 |
1968年 | 2033篇 |
1967年 | 2140篇 |
1966年 | 1940篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
951.
952.
953.
To assess the oral activity of KP102 (also known GHRP-2) on growth hormone (GH) release in ruminant animals, 5 or 10 mg/kg body weight (BW) of KP102 dissolved in saline was orally administered twice at 2 hr-intervals to either 1- or 3-mo-old goats (n = 5-6). Plasma GH concentrations in the 1-mo-old goats were elevated at 15 min after the first administration of both 5 and 10 mg/kg BW of KP102. Significant elevation of GH concentrations continued until 180 min after 10 mg/kg BW of KP102, whereas the elevated GH levels after the administrations of 5 mg/kg BW of KP102 subsided to basal concentrations within 90 min. The second administration of 10 mg/kg BW of KP102 failed to elevate the GH concentration, but 5 mg/kg BW of KP102 abruptly stimulated GH release. Plasma GH concentrations in the 3-mo-old goats were also significantly elevated after the administration of both 5 and 10 mg/kg BW of KP102. The plasma GH responses to 5 and 10 mg/kg BW of KP102 were almost identical. The elevated GH levels after the first administration of KP102 tended to be maintained throughout the experiment, and a transient increase in plasma GH levels was observed after the second administration. However, the stimulatory effect of KP102 on GH release in the 3-mo-old goats was small and less abrupt than that in the 1-mo-old goats. The concentrations of insulin-like growth factor-I were not increased by KP102 during the brief sampling periods used in this experiment. These results show that the oral administration of the peptidergic GH secretogogue KP102 stimulates GH release in a ruminant species, and that the oral activity of KP102 on GH release is modified by the age. 相似文献
954.
Chae C Cheon DS Kwon D Kim O Kim B Suh J Rogers DG Everett KD Andersen AA 《Veterinary pathology》1999,36(2):133-137
Gnotobiotic piglets were inoculated intralaryngeally with swine Chlamydia trachomatis strain R33 or orally with swine C. trachmatis strain R27. Archived formalin-fixed, paraffin-embedded tissues from piglets euthanatized 4-7 days postinoculation were examined by in situ hybridization for C. trachomatis nucleic acid using a nonradioactive digoxigenin-labeled DNA probes that targeted specific ribosomal RNA or omp1 mRNA molecules of the swine C. trachomatis strains. Positive hybridization signals were detected in bronchial epithelial cells, bronchiolar epithelial cells, pneumocytes, alveolar and interstitial macrophages, and jejunal and ileal enterocytes. Chlamydia-infected cells had a strong signal that was confined to the intracytoplasmic inclusions. Positive hybridization signals were not detected in tissue sections from an uninfected control piglet or in C. psittaci-infected sheep placenta. The morphology of host cells was preserved despite the relatively high temperature required in parts of the incubation procedure. The data indicate that in situ hybridization can be used to detect swine C. trachomatis in formalin-fixed, paraffin-embedded tissue specimens. 相似文献
955.
Cynthia C. Nordberg DVM Kenneth A. Johnson MVSc PhD 《Veterinary radiology & ultrasound》1999,40(2):128-136
Magnetic resonance imaging was conducted on previously frozen left carpi from six normal dogs using a 1.5 Tesla magnet in combination with a transmit/receive wrist coil. Three-millimeter thick T1-weighted spin-echo images and 1-mm thick T2*-weighted gradient-recalled 3-D images were obtained in dorsal and sagittal planes. Carpi were embedded, sectioned, and stained. Anatomic structures on the histologic sections were correlated with the MR images. All of the carpal ligaments plus the radioulnar articular disc and the palmar fibrocartilage were identified on MR images. The accessorio-quartile ligament, which had not been well described previously in dogs, was also identified. It originated on the accessory carpal bone and inserted on the fourth carpal bone. The T2*-weighted gradient echo imaging technique provided better images than T1-weighted technique, largely because thinner slices were possible (1 mm vs. 3 mm), resulting in less volume averaging of thin ligaments with surrounding structures. Although MRI is currently the imaging modality of choice to identify ligamentous injury in humans, further studies are needed to determine if abnormalities can be detected in canine carpal ligaments using MRI. 相似文献
956.
J B Woodie A J Ruggles A L Bertone J Hardy R K Schneider 《Journal of the American Veterinary Medical Association》1999,214(11):1653-1656
OBJECTIVE: To determine whether fracture fragment dimensions, suspensory ligament damage, and racing status at the time of injury were associated with outcome in Standardbred horses with apical fracture of the proximal sesamoid bone. DESIGN: Retrospective study. ANIMALS: 43 Standardbred racehorses. PROCEDURE: Medical records, racing records, and radiographs were reviewed, and ultrasonographic findings were scored. Measurements of the fractured portion of the proximal sesamoid bone were made. RESULTS: Seventy-four percent (32/43) of horses were pacers, and 26% (11/43) were trotters. Statistical differences between trotters and pacers regarding ability to start, number of starts, or amount of money earned after injury were not detected. Females earned significantly more money per start after injury than males. Eighty-six percent (37/43) of fractures involved hind limbs and 14% (6/43) involved forelimbs. Horses with forelimb injuries earned less money per start. Severity of suspensory ligament damage did not affect postinjury racing performance. A higher proportion of horses that had raced before injury returned to racing after surgery than horses that had not raced before injury, although a significant difference between these groups was not detected. Eighty-eight percent of horses that raced before injury raced after injury. Fifty-six percent of horses that did not race before injury raced after injury. Fracture fragment dimensions did not affect outcome. CLINICAL IMPLICATIONS: Dimensions of the apical fracture fragment of the proximal sesamoid bone in Standardbred horses and degree of suspensory ligament damage did not affect outcome. Prognosis for return to racing soundness is good in horses that had raced before injury and fair in horses that had not raced before injury. 相似文献
957.
P Mandebvu J W West G M Hill R N Gates R D Hatfield B G Mullinix A H Parks A B Caudle 《Journal of animal science》1999,77(6):1572-1586
A study was undertaken to compare Tifton 85 (T85) and Coastal (CBG) bermudagrasses for effects of cultivar and age at harvest on yields of DM and digestible DM, in vitro digestion, nutrient content, cell wall composition, in situ digestion kinetics, and feed intake and digestion by growing beef steers. In Exp. 1, T85 and CBG forages staged for growth in May or July of 1993 were harvested at 3, 4, 5, 6, 7, and 8 wk from subplots. Tifton 85 bermudagrass had 7.1% greater DM yield, 18.2% higher (P < .05) digestible DM yield, and 7.1% greater IVDMD than CBG, and, after 5 wk of forage growth, IVDMD of both T85 and CBG decreased with increased age at harvest (P < .05). In Exp. 2, T85 and CBG forages staged for growth in July 1997 were harvested at 2, 3, 4, 5, 6, and 7 wk from subplots. Even though T85 had higher concentrations of NDF and ADF than CBG, T85 had 34.1% higher DM yield, 47.9% higher digestible DM, 55.0% higher digestible NDF, 91.7% higher digestible ADF, greater IVDMD, in vitro NDF and ADF disappearances, and higher in situ DM and NDF digestion (P < .05). Coastal bermudagrass had higher concentrations of lignin and lower concentrations of total neutral sugars, arabinose, glucose, and xylose than T85 (P < .05). In vitro digestibilities of DM, NDF, and ADF were lower and concentrations of ADF and lignin were greater for 7- vs 6-wk harvests of both T85 and CBG (P < .05). In Exp. 3, T85 and CBG forages staged for growth in July 1997 were harvested as hay at 3, 5, and 7 wk from .8-ha pastures and fed to 36 individually penned growing beef steers (initial BW = 244 kg) to quantify ad libitum intake without supplementation. Tifton 85 bermudagrass had lower concentrations of lignin and ether-linked ferulic acid and greater concentrations of NDF, ADF, hemicellulose, and cellulose than CBG (P < .05). Steers fed T85 had higher (P < .05) digestion of DM, OM, NDF, ADF, hemicellulose, and cellulose than steers fed CBG. Digestion of NDF, ADF, hemicellulose, and cellulose decreased (P < .05) with increased age at harvest for both cultivars. In conclusion, T85 produced more DM and had more digestible nutrients in vitro, in situ, and in vivo than CBG, and 3 and 5 wk of growth would be recommended ages to harvest either cultivar. 相似文献
958.
S Burkhardt J Hentschke H Weiler B Ehlers A Ochs J Walter U Wittstatt R G?ltenboth 《Berliner und Münchener tier?rztliche Wochenschrift》1999,112(5):174-179
Herpesvirus infections which take a fatal turn on African elephants as well as on Asian elephants seem to occur increasingly not only in the USA but also in European stocks. The endotheliotropic herpesvirus causes a rapidly progressing and severe disease which makes any therapeutical effort unsuccessful and finally results in death of the animal, especially in young Asian elephants. As all attempts to culture the virus failed up to now, molecular biological procedures have to be used more often for diagnostical purpose together with the common methods of pathology, virology, and electronmicroscopical evaluation. This is a report on the case of 'KIBA', an eleven year old male elephant at the Zoological Garden Berlin, infected with the endotheliotropic elephants herpesvirus. 'KIBA' was born at the Zoo in Houston, Texas, and raised within his herd. Upon arriving in Berlin in November 1997 he adapted to the new premises and climate and new social circumstances without any problems. In June 1998 he already serviced three females of his new herd several times. In August 1998 he died after passing a peracute progression of the disease after residenting in Berlin for only 9 months. The dissection of the animal revealed some evidence on an agent damaging the endothelium. Major signs indicating this agent were bleedings in several serous membranes, mucosa and on the the right atrium, as well as other parts of the myocardium. Furthermore there have been ulcerations at various localisations of the whole digestive tract. Slightly basophilic intranuclear inclusion bodies have been found histologically in endothelial cells of different organ samples. An examination of altered organ-material by electronmicroscopy made some herpesvirus-like particles visible. A virological investigation first revealed evidence of giant cell formations with solitary basophilic intranuclear inclusion bodies in different cell cultures, however, without any distinct cytopathogenic effect. Supported by molecular biological procedures the infection of 'KIBA' could be verified as the elephants herpesvirus. By means of PCR and subsequent sequence analysis a DNA-sequence typical for the elephants herpesvirus could be obtained which showed an identity of 97% with the terminase sequence of the elephant herpesvirus described by American authors. The deduced amino acid-sequences were 100% identical. To the terminase of the human cytomegalovirus, the elephant sequence had an identity of 53% (similarity: 74%). Based on the cooperation of ILAT, Institute of Veterinary-Pathology/Free University Berlin, Robert-Koch-Institut Berlin, and Zoological Garden Berlin, the cause of 'KIBA's' death could be discovered immediately. Possible implications of this case especially on breeding and keeping elephants are discussed briefly. 相似文献
959.
960.