全文获取类型
收费全文 | 14126篇 |
免费 | 1071篇 |
国内免费 | 72篇 |
专业分类
林业 | 627篇 |
农学 | 833篇 |
基础科学 | 125篇 |
2000篇 | |
综合类 | 1668篇 |
农作物 | 496篇 |
水产渔业 | 1045篇 |
畜牧兽医 | 7078篇 |
园艺 | 230篇 |
植物保护 | 1167篇 |
出版年
2023年 | 90篇 |
2021年 | 90篇 |
2020年 | 123篇 |
2019年 | 201篇 |
2018年 | 373篇 |
2017年 | 347篇 |
2016年 | 337篇 |
2015年 | 309篇 |
2014年 | 329篇 |
2013年 | 571篇 |
2012年 | 489篇 |
2011年 | 583篇 |
2010年 | 464篇 |
2009年 | 421篇 |
2008年 | 559篇 |
2007年 | 581篇 |
2006年 | 478篇 |
2005年 | 521篇 |
2004年 | 412篇 |
2003年 | 448篇 |
2002年 | 359篇 |
2001年 | 760篇 |
2000年 | 722篇 |
1999年 | 591篇 |
1998年 | 173篇 |
1997年 | 165篇 |
1996年 | 126篇 |
1995年 | 150篇 |
1994年 | 156篇 |
1993年 | 120篇 |
1992年 | 321篇 |
1991年 | 346篇 |
1990年 | 291篇 |
1989年 | 266篇 |
1988年 | 271篇 |
1987年 | 319篇 |
1986年 | 245篇 |
1985年 | 193篇 |
1984年 | 170篇 |
1983年 | 150篇 |
1982年 | 94篇 |
1981年 | 83篇 |
1980年 | 80篇 |
1979年 | 141篇 |
1978年 | 94篇 |
1977年 | 73篇 |
1975年 | 77篇 |
1974年 | 79篇 |
1971年 | 69篇 |
1969年 | 70篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
42.
Mixtures of cymoxanil with mancozeb (Mancur) or with mancozeb plus oxadixyl (Pulsan, Sandocur-M) were effective in controlling either metalaxyl-sensitive (MS) or -resistant (MR) isolates ofPseudoperonospora cubensis on cucumbers (cv. ‘Elem’) in growth chambers. Metalaxyl+mancozeb (Ridomil-MZ) and oxadixyl+mancozeb (SAN-518) mixtures were effective against the metalaxyl-sensitive but less so against the metalaxyl-resistant isolate. Fungicide mixtures were far more effective in controlling either the sensitive or the resistant isolates than were the individual components applied alone, thereby representing significant levels of synergistic interactions. Increased efficacy of mixtures relative to their combined components (synergy factor) was calculated by the Wadley method. Mixtures containing cymoxanil showed high synergy factors against the resistant isolate, whereas Ridomil-MZ and SAN-518 did not evince this phenomenon. We concluded that cymoxanil mixtures might be suitable for the control of downy mildew incited by a metalaxyl-resistant isolate ofP. cubensis. 相似文献
43.
Attempts were made to identify 900 species of staphylococci or micrococci recovered from samples of bovine milk examined for mastitis pathogens. The presence and identity of haemolysins was recorded together with results of disc diffusion antibiotic sensitivity tests. The occurrence of clinical mastitis was also noted and somatic cell counts (SCC) were performed on milk samples which were normal in appearance. Eight hundred and thirty-one coagulase positive staphylococci were obtained, of which 810 were S. aureus and 21 were S. intermedius. Of 65 coagulase negative staphylococci the species of 19 could not be determined by the identification systems used. The remainder were identified as S. hyicus sub sp. hyicus (1), S. hyicus sub sp. chromogenes (19), S. haemolyticus (17), S. hominis (3), S. epidermidis (4), S. capitis (1) and either S. hominis or S. warneri (1). Four other isolates could not clearly be assigned to the genus Staphylococcus or Micrococcus and were designated irregular strains. No micrococci were identified. The presence of alpha, beta, or delta haemolysins occurring singly or in various combinations was identified in 98.3% of coagulase positive staphylococci and in 60% of coagulase negative staphylococci. Epsilon haemolysin was detected in 47.6% of the coagulase negative staphylococci and in 9.5% of S. intermedius. All staphylococci were sensitive to tetracycline (30 microg), novobiocin (1.6 microg), nafcillin (30 microg), methicillin (10 microg) and cephalothin (30 microg) and variable numbers of each species were sensitive to penicillin (2 iu) and streptomycin (10 microg). One non-identified species of coagulase negative staphylococcus was sensitive to erythromycin (0.4 microg) the remaining staphylococci were resistant. Each of the four irregular strains was sensitive to erythromycin and novobiocin. Clinical mastitis was associated with 30.6% of coagulase positive staphylococci, 15.3% of coagulase negative staphylococci, and two of the four irregular strains (50%). Subclinical mastitis as determined by SCC of 500 x 10(3) or greater was associated with 92.7% of coagulase positive and 37.5% of coagulase negative staphylococci. 相似文献
44.
45.
46.
47.
Fusarium oxysporum f.sp.dianthi causes severe wilting in carnation (Dianthus caryophyllus L.) worldwide. The pathogen is present in the soil profile in which carnation roots are distributed and may infect the plants at any time during the growing season. To minimize the losses induced by Fusarium wilt, growers use carnation cuttings free ofFusarium spp. and fumigate the soil with methyl bromide prior to planting. The severity of epidemics and the resulting losses are governed by the main and interacting effects of the three components of the disease syndrome: the host, the pathogen and the environment. Host variables include the type and the degree of cultivar resistance (i.e., complete, partial or tolerance); pathogen variables include the race, its virulence and infectivity, and the amount of initial inoculum; environmental variables include solar radiation intensity, photoperiod, temperature and the growth substrate. In the present review the information available on the effect of the host, the pathogen and the environment, and their interactions, on Fusarium wilt in carnation is summarized. 相似文献
48.
现已证明,在酵母中产生的一种新型的6-植酸酶比其他在市场上供应的植酸酶的效率至少高20%。因为6-植酸酶与其他商品化的植酸酶相比,可进一步减少无机磷源的使用,从而降低生产成本以及磷的污染。 相似文献
49.
50.
T. Honda T. Nomura Y. Yamaguchi F. Mukai 《Zeitschrift für Tierzüchtung und Züchtungsbiologie》2004,121(4):242-252
The gene pool of the Japanese Black cattle has been completely closed to foreign breeds during the last 100 years. Genetic diversity of the Japanese Black cattle from 1960 to 2000 was monitored with three estimates of effective number of ancestors. Founder genome equivalent (Nge) accounts for all the causes of reduction of diversity. Effective number of founders (Nef) and non‐founders (Nenf) explain reduced diversity because of unequal genetic contributions of founders and random genetic drift in non‐founders, respectively. Further examination using gene dropping simulation was conducted to obtain information on survival of founder alleles. Unique founder alleles were dropped down along the actual pedigree with Monte Carlo procedure following Mendelian segregation rules, and generated genotypes of all the current live animals (612 959 heads). Pedigree records consisted of 2 075 188 animals was used for these analysis. The estimates of three effective numbers (Nef, Nge, and Nenf) decreased from 418.6 to 50.3, 86.6 to 7.3, and 109.2 to 8.5, respectively, during the period 1960–2000. The increasing differences between two kinds of genetic diversity indices derived from Nge and Nef showed that large part of the reduced diversity from 1980 was attributed to genetic drift caused by the intensive use of particular limited number of sires. In gene dropping analysis, probabilities of extinction of founder alleles were derived from their distributions of frequency in the current animals. Several founders showed low probabilities of allele extinction, irrespective of their relatively low genetic contributions. This suggests that these founders have lineages through which their alleles are surely transmitted to the current breed. The use of these founders as a strategy for recovering the genetic diversity was discussed. 相似文献