全文获取类型
收费全文 | 132948篇 |
免费 | 7289篇 |
国内免费 | 812篇 |
专业分类
林业 | 5395篇 |
农学 | 3861篇 |
基础科学 | 1041篇 |
14918篇 | |
综合类 | 28795篇 |
农作物 | 5040篇 |
水产渔业 | 5663篇 |
畜牧兽医 | 66999篇 |
园艺 | 1689篇 |
植物保护 | 7648篇 |
出版年
2019年 | 1257篇 |
2018年 | 1735篇 |
2017年 | 1965篇 |
2016年 | 1775篇 |
2015年 | 1679篇 |
2014年 | 1918篇 |
2013年 | 4478篇 |
2012年 | 3757篇 |
2011年 | 4509篇 |
2010年 | 2998篇 |
2009年 | 2861篇 |
2008年 | 4167篇 |
2007年 | 4050篇 |
2006年 | 3736篇 |
2005年 | 3637篇 |
2004年 | 3311篇 |
2003年 | 3460篇 |
2002年 | 3278篇 |
2001年 | 3570篇 |
2000年 | 3609篇 |
1999年 | 2866篇 |
1998年 | 1224篇 |
1997年 | 1155篇 |
1995年 | 1233篇 |
1992年 | 2527篇 |
1991年 | 2784篇 |
1990年 | 2775篇 |
1989年 | 2761篇 |
1988年 | 2604篇 |
1987年 | 2593篇 |
1986年 | 2685篇 |
1985年 | 2497篇 |
1984年 | 2116篇 |
1983年 | 1839篇 |
1982年 | 1287篇 |
1981年 | 1205篇 |
1979年 | 1962篇 |
1978年 | 1595篇 |
1977年 | 1387篇 |
1976年 | 1357篇 |
1975年 | 1479篇 |
1974年 | 1954篇 |
1973年 | 1874篇 |
1972年 | 1909篇 |
1971年 | 1777篇 |
1970年 | 1717篇 |
1969年 | 1528篇 |
1968年 | 1245篇 |
1967年 | 1438篇 |
1966年 | 1250篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
Mycotic infection was diagnosed in 6.8% of 6,858 cases of bovine abortion and stillbirth examined during a 9-year period. Aspergilli were associated with approximately 5% of all abortion cases and 71% of 446 cases that were cultured for fungi and diagnosed as mycotic abortion. Aspergillus fumigatus was the most frequent isolate (62%), followed by A. terreus (6.7%), Emericella (Aspergillus) nidulans (3.0%), A. flavus (2.9%), and E. rugulosus (less than 1.0%). Zygomycetes (Absidia, Mortierella, Rhizomucor, Rhizopus) accounted for 21% of the cases. Pseudallescheria boydii and yeasts (Candida, Torulopsis) were each identified in 2% of the cases. Fungi that uncommonly cause infection accounted for 2% of the cases and included Curvularia geniculata, Exophilia jeanselmei, Hendersonula toruloidea, Lecythosphora hoffmannii, Talaromyces flavus var. flavus (Penicillium vermiculatus), T. (Penicillium) thermophilus, and Wangiella dermatitidis. About 10% of the mycotic cases were mixed fungal infections involving A. fumigatus (87%), A. flavus (12.5%), or E. nidulans (12.5%) coexisting with Absidia corymbifera (72%), Rhizomucor pusillus (4.3%), or Rhizopus arrhizus (4.3%). In each mixed infection, both septate and nonseptate hyphae were observed in placental tissues. Twelve percent of the mycotic abortion cases were diagnosed by histologic examination alone because isolation attempts were negative or only formalin-preserved tissues were available. 相似文献
992.
J.A Stegeman M.C.M De Jong H.M.J.F Van Der Heijden A.R.W Elbers T.G Kimman 《Research in veterinary science》1996,61(3):263-267
The performance of tests for the detection of antibodies to Aujeszky's disease virus glycoprotein E (ge) in a target population was evaluated by constructing and analysing receiver operating characteristic (roc) curves. These curves assess the discriminating ability of a test over the entire range of test signals. The advantages of applying the analysis to a sample of the target population (all commercial pigs in the Netherlands), as compared to using a panel of test sera, are that the estimates of sensitivity and specificity, the comparisons between tests and the choices of the cut-off values are all relevant for the target population. The results of a gE-elisa in colostrum (test A) and in a single droplet of whole blood (test B) were compared with the results obtained with the same elisa in serum (gold standard). The area under the ROC curve, which is a quantitative measure of test performance, was significantly (P<0·01) smaller with test A than test B or the gold standard, indicating that test B performed better than test A. No significant difference was observed between test B and the gold standard. 相似文献
993.
Frankena K Somers JG Schouten WG van Stek JV Metz JH Stassen EN Graat EA 《Preventive veterinary medicine》2009,88(2):150-157
This study describes the effects of floor system, digital dermatitis (DD) and interdigital dermatitis and heel-horn erosion (IDHE) on locomotion performance in 225 dairy cows of 12 commercial dairy herds. Nine herds were kept in cubicle houses with concrete passageways (either solid, slatted, or grooved concrete) and three herds were kept in straw yards. Animals were at most five times examined at monthly intervals for lesion severity of DD and IDHE and for locomotion score. Locomotion score was rated on a scale ranging from 1 to 5 (from normal to severe) and disturbed locomotion (lameness) was defined as a score > or =3. A logistic regression model was used to analyze the 943 observations using lameness (yes/no) as outcome variable. The proportion of observations scored as lame (locomotion score > or =3) increased from 18% 1 month after trimming to 29% at 4 months after trimming. Severe lesions of DD and IDHE were associated with a significantly higher proportion of lame cows. The proportion of animals with disturbed locomotion increased from 16% to 40% as the severity of DD increased and from 17% to 30% with increasing severity of IDHE lesions. Locomotion performance highly differed between the cubicle house and straw yard group. Only 1% of all gaits in straw yard cows were scored as lame, while in cubicle housed cows these percentages varied from 24% to 46% with grooved floors showing the highest average locomotion score. Due to the extreme low incidence of lameness in straw yards, the statistical analysis had to be restricted to observations on concrete floors (n=744). The logistic regression model with lameness (yes/no) as dependent variable and random effects of cow and herd resulted in Odds Ratios for severe DD and IDHE of, respectively, 3.2 and 3.2, both significantly larger than unity. Cows housed at grooved concrete floors showed the highest OR of 6.5 compared to solid concrete floors. Recovery of lameness was poor as disturbance in gait lasted several months. 相似文献
994.
A haematological disorder in a dog characterised by a massive leucocytosis, mainly composed of eosinophils and their precursors is reported here. The normal composition of cells in the bone marrow was displaced in favour of the eosinophils and their precursors. No apparent cause for the pronounced eosinophilia could be determined by clinical, haematological, clinical-chemical, radiological or pathological examinations. A diagnosis of eosinophilic leukaemoid reaction was suggested as the criteria for the diagnosis of eosinophilic leukaemia in the dog but this was not firmly established. 相似文献
995.
996.
997.
998.
999.
1000.