全文获取类型
收费全文 | 5304篇 |
免费 | 308篇 |
国内免费 | 4篇 |
专业分类
林业 | 269篇 |
农学 | 244篇 |
基础科学 | 9篇 |
1002篇 | |
综合类 | 609篇 |
农作物 | 587篇 |
水产渔业 | 424篇 |
畜牧兽医 | 2067篇 |
园艺 | 74篇 |
植物保护 | 331篇 |
出版年
2023年 | 28篇 |
2022年 | 89篇 |
2021年 | 116篇 |
2020年 | 97篇 |
2019年 | 107篇 |
2018年 | 137篇 |
2017年 | 160篇 |
2016年 | 184篇 |
2015年 | 164篇 |
2014年 | 199篇 |
2013年 | 284篇 |
2012年 | 350篇 |
2011年 | 418篇 |
2010年 | 223篇 |
2009年 | 220篇 |
2008年 | 314篇 |
2007年 | 301篇 |
2006年 | 269篇 |
2005年 | 248篇 |
2004年 | 232篇 |
2003年 | 189篇 |
2002年 | 203篇 |
2001年 | 144篇 |
2000年 | 119篇 |
1999年 | 77篇 |
1998年 | 32篇 |
1997年 | 18篇 |
1996年 | 20篇 |
1995年 | 21篇 |
1993年 | 21篇 |
1992年 | 28篇 |
1991年 | 27篇 |
1990年 | 33篇 |
1989年 | 37篇 |
1988年 | 31篇 |
1987年 | 40篇 |
1986年 | 18篇 |
1985年 | 32篇 |
1984年 | 23篇 |
1983年 | 27篇 |
1981年 | 19篇 |
1980年 | 15篇 |
1978年 | 21篇 |
1977年 | 19篇 |
1976年 | 28篇 |
1975年 | 14篇 |
1974年 | 20篇 |
1973年 | 22篇 |
1972年 | 22篇 |
1971年 | 15篇 |
排序方式: 共有5616条查询结果,搜索用时 0 毫秒
991.
Populations of the green peach aphid,Myzus persicae (Sulzer), and the potato aphid,Macrosiphum euphorbiae (Thomas), were observed on 27 named varieties of Irish potatoes in the Yakima Valley of Washington intermittently from 1947 through 1968. The Epicure, Great Scot, and B5141-6 varieties produced relatively fewer green peach aphids than other varieties tested; Bliss Triumph and Red Pontiac produced relatively fewer potato aphids. Except for Doebay Red, the red-skinned varieties, Bliss Triumph, Red McLure, Norland, and Earnly Rose, were extremely to moderately productive of the green peach aphid. No correlation was apparent between abundance of aphids and the specific gravity or yield of tubers. 相似文献
992.
Four clones of Sitka spruce (Picea sitchensis (Bong.) Carr.) from two provenances, at 53.2 degrees N (Skidegate a and Skidegate b) and at 41.3 degrees N (North Bend a and North Bend b), were grown near Edinburgh (55.5 degrees N), U.K., for three growing seasons in ambient (~350 micromol per mol) and elevated (~700 micromol per mol) CO2 concentrations under conditions of non-limiting water and nutrient supply. Bud phenology was not affected by elevated [CO2] in the second growing season, but in the third year, the duration of shoot extension growth in three of the four clones (North Bend clones and Skidegate a) was significantly shortened, because of the suppression of lammas growth. Saplings in elevated [CO2] had significantly greater dry masses of all components than saplings in ambient [CO2]. However, comparison of relative component dry masses between plants of similar size showed no effect of [CO2] treatment on plant allometric relationships. This finding, and the observed suppression of lammas growth by high [CO2] during the third growing season suggests that the main effect of increasing [CO2] is to accelerate sapling development. Clonal provenance did not affect dry mass production in ambient [CO2]. However, in elevated [CO2] the more southerly clones significantly out-performed the more northerly clones when grown at a latitude close to the latitudinal provenance of the Skidegate clones. As atmospheric carbon dioxide concentration rises, such changes in the relative performance of genotypes may be exploited for economic gain through appropriate selection of provenances for forest plantings. 相似文献
993.
Johnny Altwal Ber-In Lee Mary-Keara Boss Susan M. LaRue Tiffany Wormhoudt Martin 《Veterinary and comparative oncology》2024,22(1):125-135
Canine craniomaxillofacial osteosarcoma (OSA) is most commonly treated surgically; however, in cases where surgery is not feasible or non-invasive treatment is desired, stereotactic body radiation therapy (SBRT) may be elected for local tumour control. In this study, we evaluated 35 dogs treated with SBRT. Nine dogs (26%) had calvarial, seven (20%) had mandibular and 19 (54%) had maxillary OSA. Median time to first event (TFE) was 171 days, and overall median survival time (MST) was 232 days. Site-specific MSTs were 144 days for mandible, 236 days for calvarium and 232 days for maxilla (p = .49). Pulmonary metastatic disease was observed in 12/35 (34%) patients and was detected pre-SBRT in six dogs (17%) and post-SBRT in the remaining six dogs (17%). Eighteen adverse events post-SBRT were documented. Per veterinary radiation therapy oncology group criteria, five were acute (14%) and three were late (9%) grade 3 events. Neurological signs in two dogs were suspected to be early-delayed effects. Cause of death was local progression for 22/35 (63%) patients, metastasis for 9/35 (26%) patients and unknown for four. On univariate analysis, administration of chemotherapy was associated with a longer TFE (p = .0163), whereas volume of gross tumour volume was associated with a shorter TFE (p = .023). Administration of chemotherapy and five fractions versus single fraction of SBRT was associated with increased survival time (p = .0021 and .049). Based on these findings, a treatment protocol incorporating chemotherapy and five fractions of SBRT could be considered for dogs with craniomaxillofacial OSA electing SBRT with careful consideration of normal tissues in the field. 相似文献
994.
Heon Woong Kim Sung Ryong Kim Young Min Lee Hwan Hee Jang Jung Bong Kim 《Potato Research》2018,61(1):1-17
Anthocyanin concentration and composition and the effect of steaming and baking on these were evaluated in tubers of Korean red- and purple-fleshed potato cultivars and breeding clones using liquid chromatography with diode array detection and electrospray ionization-mass spectrometry (LC-DAD-ESI-MS). Twenty-six anthocyanins were isolated, of which 24 were identified. Remarkably, five cis isomers were identified, of which four, viz., cis-petanin, cis-peonanin, petunidin 3-cis-caffeoylrutinoside-5-glucoside, and petunidin 3-cis-feruloylrutinoside-5-glucoside, are reported for the first time. Moreover, pelargonidin 3-p-coumaroylrutinoside-5-glucoside (pelanin), peonidin 3-p-coumaroylrutinoside-5-glucoside (peonanin) and petunidin 3-p-coumaroylrutinoside-5-glucoside (petanin) were identified as the principal anthocyanins. We found that the total anthocyanin content of coloured potatoes was decreased by steaming and baking compared with the raw state. In addition, we performed partial least square discriminant analysis (PLS-DA) to discriminate between the analyzed anthocyanins. Cis isomers seemed to play a vital role as a biomarker in the PLS-DA model based on the type of processing and colour of the tubers. 相似文献
995.
In Su Cheon Sung-Moo Park Hye Jin Lee Ji Eun Hong Sang Yun Ji Byoung-Shik Shim Kwang Ho Kim Pil Seung Heo Yoo Yong Kim Hyun Jung Jung Hakhyun Ka Seung Hyun Han Manki Song Cheol-Heui Yun 《Research in veterinary science》2014
In human or mouse, mature T cells express either CD4 or CD8, resulting in different functions in the periphery. Interestingly, porcine CD4 and CD8 double positive (DP) T cells are present in the blood, and their proportions change from youth to adulthood. However, the features of these cells in swine are poorly understood. We investigated the fate of porcine peripheral T cells based on their functional characteristics, including proliferation and the expression of CD4 and CD8 co-receptors. The results showed that all the populations changed their CD8 expression in a time-dependent manner and porcine T cells had different proliferative pattern from human T cells. The results further revealed that Th2 cytokines were increased later in porcine T cells compared to human T cells upon stimulation with IL-2 + PMA. Collectively, we found that the fate of porcine peripheral T cells is different from that of human T cells, and the changes occur in a time- and stimulation-dependent manner. 相似文献
996.
997.
Food safety is one of the major concerns in every country regardless of the economic and social development. The frequent occurrence of food scandals in the world has led the Chinese government to implement several strategies to fortify the food supply system to a high food safety standard. This relies heavily on laboratory testing services but conventional methods for detection of food contaminants and toxicants are limited by sophisticated sample preparation procedures,long analysis time,large instruments and professional personnel to meet the increasing demands. In this review,we have incorporated most of the current and potential rapid detection methods for many notorious food contaminants and toxicants including microbial agents,toxic ions,pesticides,veterinary drugs and preservatives,as well as detection of genetically modified food genes and adulterated edible oil. Development of rapid,accurate,easy-to-use and affordable testing methods could urge food handlers and the public to actively screen for food contaminants and toxicants instead of passively relying on monitoring by the government examination facility. This review also provides several recommendations including how to encourage the public to engage in the food safety management system and provide optimal education and financial assistance that may improve the current Chinese food safety control system. 相似文献
998.
Staphylococcus simulans, a coagulase-negative staphylococcal species, can cause several diseases in humans and animals. This report describes a case of dermatosis characterized by broad, well-circumscribed hyperkeratosis and alopecia on the back of a household pygmy hedgehog (Erinaceous albiventris). Quills and exudates were studied by microscopy. The microscopic examination of the exudates collected from the lesion revealed several leukocytes and numerous gram-positive cocci. An aerobic bacterial culture revealed overgrowth of the same gram-positive bacteria. The bacterium was identified as S. simulans by polymerase chain reaction amplification and direct sequencing targeted to the 16S ribosomal RNA gene. This report is the first to show that S. simulans could be related to the dermatitis of hedgehogs. 相似文献
999.
Analyses of monoclonal antibodies reacting with porcine CD3: results from the Second International Swine CD Workshop 总被引:2,自引:0,他引:2
M. D. Pescovitz B. K. Book B. Aasted J. Dominguez A. Ezquerra I. Trebichavsky B. Novikov I. Valpotic J. Nielsen S. Arn D. H. Sachs J. K. Lunney P. C. Boyd J. Walker R. Lee G. Lackovic P. Kirkham R. M. E. Parkhouse A. Saalmü ller 《Veterinary immunology and immunopathology》1998,60(3-4):261-268
Among the 57 monoclonal antibodies (mAb) analyzed within the T-cell group from the Second Swine CD Workshop, six mAb fell within clusters T10 and T11 (No. 088, STH164; No. 148, FY1A3; No. 149, FY2C1; No. 150, FY1H2; No. 151, FY2A11; No. 169, BB23-8E6). The mAb within these two groups gave a similar appearance on flow cytometry and stained all peripheral blood T-cells as defined by CD4 and wCD8 staining. All six mAb precipitated a 24 kDa protein. On the basis of inhibition analyses performed as part of the workshop and from published data, the mAb define at least three epitopes. There is only minimal stimulation of resting peripheral lymphocytes, but four of the mAb produce strong stimulation in the presence of PMA. With the exception of STH164, all have been shown to react with CD3-transfected COS cells. The new mAb, therefore, react with three epitopes on porcine CD3 designated CD3a (BB23-8E6, FY2A11), CD3b (FY1A3, FY2C1), and CD3c (FY1H2). mAb STH164 appears to be reactive with another epitope, however, since its reactivity with CD3 has not been confirmed it is designated as wCD3. 相似文献
1000.
Carbon nanotube (CNT) films are very flexible and serve as active materials for lithium-ion batteries (LIBs). Hence, they have high potential as flexible free-standing electrodes for wearable batteries. However, nanocarbon materials such as CNTs and graphene are of limited use as electrodes because they have a large initial irreversible capacity due to the formation of a solid electrolyte interphase (SEI). Herein, we prelithiated the CNT films to make them available as electrodes for flexible batteries by reducing their irreversible capacity. The SEI is pre-formed through a direct prelithiation (DP) method that brings lithium metal into direct contact with CNT films in an electrolyte. As a result, the capacity of directly-prelithiated CNT film electrodes continues to increase to 1520 mAh/g until 350th cycle of charge/discharge and their initial irreversible capacity vanishes. The changes in the electrochemical properties of CNT film electrodes by DP treatment and their flexibility are investigated. 相似文献