全文获取类型
收费全文 | 159641篇 |
免费 | 5347篇 |
国内免费 | 110篇 |
专业分类
林业 | 6841篇 |
农学 | 5070篇 |
基础科学 | 940篇 |
19607篇 | |
综合类 | 27623篇 |
农作物 | 6120篇 |
水产渔业 | 7936篇 |
畜牧兽医 | 78843篇 |
园艺 | 2013篇 |
植物保护 | 10105篇 |
出版年
2019年 | 1547篇 |
2018年 | 2221篇 |
2017年 | 2526篇 |
2016年 | 2321篇 |
2015年 | 1955篇 |
2014年 | 2450篇 |
2013年 | 5906篇 |
2012年 | 4493篇 |
2011年 | 5523篇 |
2010年 | 3624篇 |
2009年 | 3685篇 |
2008年 | 5405篇 |
2007年 | 5152篇 |
2006年 | 4873篇 |
2005年 | 4544篇 |
2004年 | 4306篇 |
2003年 | 4448篇 |
2002年 | 4088篇 |
2001年 | 4966篇 |
2000年 | 4942篇 |
1999年 | 4012篇 |
1998年 | 1650篇 |
1997年 | 1631篇 |
1996年 | 1483篇 |
1995年 | 1776篇 |
1994年 | 1643篇 |
1993年 | 1489篇 |
1992年 | 3101篇 |
1991年 | 3177篇 |
1990年 | 3084篇 |
1989年 | 3056篇 |
1988年 | 2813篇 |
1987年 | 2858篇 |
1986年 | 2939篇 |
1985年 | 2802篇 |
1984年 | 2355篇 |
1983年 | 2075篇 |
1982年 | 1418篇 |
1979年 | 2106篇 |
1978年 | 1693篇 |
1977年 | 1418篇 |
1976年 | 1464篇 |
1975年 | 1526篇 |
1974年 | 1878篇 |
1973年 | 1861篇 |
1972年 | 1803篇 |
1971年 | 1693篇 |
1970年 | 1555篇 |
1969年 | 1669篇 |
1967年 | 1455篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
112.
113.
Arthroscopic verification of ultrasonographic diagnosis of meniscal pathology in dogs 总被引:1,自引:0,他引:1
OBJECTIVE: To determine the clinical usefulness of ultrasonography for diagnosis of meniscal pathology in dogs. STUDY DESIGN: Double-blind prospective study. ANIMALS: Dogs (n=10) with lameness localized to the stifle. MATERIALS AND METHODS: Sonographic examination of each affected stifle was performed by 1 ultrasonographer unaware of specific historical and clinical data for the dog. Sonographic findings were recorded, but not reviewed until study completion. Arthroscopic examination of the affected stifle was performed within 48 hours of ultrasonography by 1 surgeon unaware of ultrasonographic findings. Arthroscopic findings were recorded, but not reviewed until study completion. Two investigators compared the ultrasonographic and arthroscopic findings at study completion to determine the sensitivity, specificity, positive predictive value, and negative predictive value. RESULTS: Two of the 10 dogs had bilateral stifle evaluation. Twenty-four lateral and medial menisci, with normal and abnormal findings, were examined. The sensitivity and specificity for ultrasonographic diagnosis were 90.0% and 92.9%, respectively; positive and negative predictive values were 90.0% and 92.9%, respectively. CONCLUSIONS: Ultrasonography is highly specific and sensitive for diagnosing bucket handle tears of the medial meniscus in dogs. CLINICAL RELEVANCE: Ultrasonographic evaluation of menisci in dogs is a noninvasive method for accurately and efficiently diagnosing pathology, determining the need for surgical intervention, and providing comprehensive information to clients. 相似文献
114.
Salinity and Orobanche or Phelipanche spp. infection are important crop stress factors in agricultural areas. In this study, we investigated the effect of salt stress on Phelipanche ramosa seed germination and its attachment onto Arabidopsis thaliana roots. We also evaluated the effect of both stresses on the expression of genes regulated by abiotic and biotic stresses. According to our results, high concentration of NaCl delayed P. ramosa seed germination in the presence of a strigolactone analogue (GR24). A similar pattern was observed in the presence of A. thaliana plants. Furthermore, we found that salt‐treated A. thaliana seedlings were more sensitive to P. ramosa attachment compared with the untreated plants, indicating that there was a positive correlation between salt sensitivity and the ability of P. ramosa to infect A. thaliana plants. At the molecular level, a synergystic effect of both salt and P. ramosa stresses was observed on the cold‐regulated (COR) gene expression profile of treated A. thaliana seedlings. Our data clarify the interaction between parasitic plants and their hosts under abiotic stress conditions. 相似文献
115.
The normal embryonic development of organs and other tissues in mice and all species is preprogrammed by genes. Inactivation of a gene involved in any stage of normal embryonic development can have severe consequences leading to embryonic or postnatal developmental defects and lethality. Pathology methods are reviewed for evaluating normal and abnormal placenta and embryo, especially after E12.5. These methods include pathology protocols for necropsy and histopathology in addition to references that will provide additional knowledge for embryo assessment including histology atlases and advanced embryo imaging techniques. 相似文献
116.
117.
R.A. Lelliott 《EPPO Bulletin》1984,14(3):337-341
The reasons for using, and the methods used for cost benefit analysis of eradication campaigns against alien pests and diseases in the UK are discussed. Details of the costanalysis for a current campaign against white rust of chrysanthemums ( Puccinia horiana ) are given. 相似文献
118.
H. T. A. M. Schepers 《European journal of plant pathology / European Foundation for Plant Pathology》1984,90(6):247-256
An inquiry was held in 1982, 1983 and 1984 to collect information on the survival and dispersal of cucumber powdery mildew. Growers who planted a crop in December, January or February were asked when they observed mildew for the first time in their crop. A gradual increase in the number of infected crops was observed from planting until May. The earliest observations of infected crops were immediately after planting. The weeks of the first observation of mildew, the disease-free periods and the apparent rates of increase of infected crops are presented for various districts. In the districts with the highest crop density (Pijnacker), mildew was generally observed early in the growing season, while the apparent rate of increase of infected crops was higher than in other districts. In the district with the lowest crop density (Northern Netherlands), mildew was observed late in the growing season and the apparent rate of increase of infected crops was low. Possible means of survival and dispersal of inoculum are discussed. It is suggested that overwintering of inoculum is possible because cucumber plants are grown all year round. Dispersal of cucumber powdery mildew is suggested to take place by transportation of infected planting stock, visitors and wind. 相似文献
119.
ABSTRACT The quantitative relationships between incidence of latent infection (ILI) of prune by Monilinia fructicola and wetness duration (WD) for different bloom and fruit developmental stages and different inoculum concentrations were obtained. Three levels of ILI were considered as criteria for low, moderate, and high risks of latent infection, respectively. Seasonal patterns of WD leading to different risk levels of latent infection were obtained for low (IP(L)) and high (IP(H)) inoculum potential conditions in orchards. Longer WD was needed at a resistant than at a susceptible fruit developmental stage to induce similar levels of latent infection. The curves of WD leading to different levels of ILI over the growing season (risky WD curves) were used in risk analysis for latent infection. Multi-year historical WD data from 10 prune-growing locations in California were compared with risky WD curves. The percentage of days (P) with WD leading to a certain risk level of latent infection was calculated for each month from historical weather data. Under the IP(L) condition, the P distributions for low risk of latent infection were higher in March and April than in May and were the lowest in June for most locations. Under the IP(H) condition, the number of days that WD leading to low risk of latent infection in May increased compared with those under the IP(L) condition. The risk analysis approach was evaluated by using separate experimental data as incidence of fruit brown rot obtained from different prune orchards over years. Consistency between predicted overall risk levels of latent infection and observed incidence of fruit brown rot was obtained. The results demonstrated the usefulness of the risk analysis in decision support system for disease management. 相似文献
120.
Isabela V. Primiano Mariana C. Cia Luis E. A. Camargo Lilian Amorim 《Plant pathology》2021,70(2):358-366
Neophysopella tropicalis, one of the causal agents of Asian grapevine leaf rust (AGLR), can cause severe epidemics in Brazil that lead to yield losses in commercial vineyards. An early detection of the pathogen by air sampling of urediniospores on spore traps or in symptomless leaves would be valuable to multiple studies, such as epidemics modelling, risk forecasting, monitoring of pathogen introductions in rust-free areas, and predicting the beginning of epidemics. This study developed a quantitative PCR (qPCR) protocol to quantify N. tropicalis urediniospores attached to adhesive tapes and in grapevine leaves before symptom appearance. A specific primer pair was designed based on the internal transcribed spacer (ITS) sequence region of the AGLR pathogen. Standard amplification curves using genomic DNA from urediniospores of N. tropicalis and from urediniospores attached to adhesive tapes were established. Grapevine leaves inoculated with N. tropicalis were collected at 2, 5, and 7 days postinoculation (dpi). One primer pair (580F/720R) amplified a 140 bp product in all AGLR isolates but did not amplify products of other rust genera, such as Phakopsora, Puccinia, Hemileia, Tranzschelia, Cerotelium, and Coleosporium. As little as 0.1 pg DNA and 10 urediniospores of N. tropicalis attached to adhesive tapes could be detected. qPCR enabled the detection of the pathogen as early as 2 dpi, before symptom appearance. This method can be used to monitor N. tropicalis inoculum in grapevine-growing areas and to quantify symptomless infections of the AGLR pathogen. 相似文献