全文获取类型
收费全文 | 3496篇 |
免费 | 131篇 |
国内免费 | 3篇 |
专业分类
林业 | 211篇 |
农学 | 93篇 |
基础科学 | 21篇 |
623篇 | |
综合类 | 523篇 |
农作物 | 178篇 |
水产渔业 | 287篇 |
畜牧兽医 | 1379篇 |
园艺 | 104篇 |
植物保护 | 211篇 |
出版年
2023年 | 21篇 |
2022年 | 21篇 |
2021年 | 63篇 |
2020年 | 64篇 |
2019年 | 69篇 |
2018年 | 63篇 |
2017年 | 68篇 |
2016年 | 84篇 |
2015年 | 48篇 |
2014年 | 86篇 |
2013年 | 130篇 |
2012年 | 149篇 |
2011年 | 235篇 |
2010年 | 109篇 |
2009年 | 98篇 |
2008年 | 190篇 |
2007年 | 211篇 |
2006年 | 224篇 |
2005年 | 204篇 |
2004年 | 209篇 |
2003年 | 199篇 |
2002年 | 194篇 |
2001年 | 47篇 |
2000年 | 41篇 |
1999年 | 41篇 |
1998年 | 51篇 |
1997年 | 50篇 |
1996年 | 44篇 |
1995年 | 37篇 |
1994年 | 35篇 |
1993年 | 29篇 |
1992年 | 35篇 |
1991年 | 30篇 |
1990年 | 35篇 |
1989年 | 30篇 |
1988年 | 22篇 |
1987年 | 23篇 |
1986年 | 17篇 |
1985年 | 28篇 |
1984年 | 21篇 |
1983年 | 26篇 |
1982年 | 24篇 |
1981年 | 22篇 |
1980年 | 19篇 |
1978年 | 18篇 |
1977年 | 11篇 |
1975年 | 18篇 |
1974年 | 17篇 |
1967年 | 8篇 |
1966年 | 8篇 |
排序方式: 共有3630条查询结果,搜索用时 15 毫秒
11.
Ana M. Casas Carlota R. Gazulla Arantxa Monteagudo Carlos P. Cantalapiedra Marian Moralejo M. Pilar Gracia Francisco J. Ciudad William T.B. Thomas José L. Molina-Cano Scott Boden Bruno Contreras-Moreira Ernesto Igartua 《作物学报(英文版)》2021,(4):862-872
Response to vernalization and photoperiod are the main determinants controlling the time to flowering in temperate cereals. While the individual genes that dete... 相似文献
12.
H. W. Poulsen H. G. Zuckerman C. H. Metzger W. B. Ward W. C. Edmundson E. R. Bennet R. A. Jehle A. B. Beaumont John S. Gardner E. L. Newdick Frank W. Hussey E. J. Wheeler H. C. Moore Marx Koehnke A. G. Tolaas E. E. Isaac H. O. Werner O. Butler William H. Martin K. H. Fernow E. R. Jackman E. B. Tussing E. V. Hardenburg J. B. R. Dickey K. H. Klages G. S. Ralston H. L. Bailey John Tucker 《American Journal of Potato Research》1934,11(8):207-226
13.
Umberto MOLINI Vimanuka MUTJAVIKUA Mari de VILLIERS Lourens de VILLIERS Alaster SAMKANGE Lauren M. COETZEE Siegfried KHAISEB Giovanni CATTOLI William G. DUNDON 《The Journal of veterinary medical science / the Japanese Society of Veterinary Science》2022,84(5):707
Samples from eleven birds (chicken, dove and peacock) with symptoms of fowlpox, caused by the avipoxvirus (APV), were collected in seven different areas of the Windhoek district, Namibia between April and October 2021. A fragment of the 4b core protein and the DNA polymerase gene of APV were amplified by PCR from the DNA of the samples and sequenced. Phylogenetic analysis revealed that the viruses present in the chickens all belonged to clade A1 while the viruses in the doves and peacock were from subclade A3.1. This is the first report of subclade A3.1 avipoxvirus in peacock. In addition, all of the samples obtained from chickens were shown by PCR to be positive for the integration of reticuloendotheliosis virus while those from the doves and peacocks were negative. This study is the first characterization of avipoxvirus in Namibia and provides additional information on the presence of avipoxvirus in southern Africa. 相似文献
14.
Polychronis Kostoulas Leonidas Leontides William J. Browne Ian A. Gardner 《Preventive veterinary medicine》2009,89(3-4):155-162
The variance partition coefficient (VPC) measures the clustering of infection/disease among individuals with a specific covariate pattern. Covariate-pattern-specific VPCs provide insight to the groups of individuals that exhibit great heterogeneity and should be targeted for intervention. VPCs should be taken into consideration when planning study designs, modeling data and estimating sample sizes. We present a Bayesian discrete mixed model for the estimation of covariate-pattern-specific VPCs when measurement of the infection/disease is based on an imperfect test. The utility of the presented model is demonstrated with three applications. In all cases, imperfect tests biased VPC estimates towards the null but corrected estimates could be obtained by modeling the sensitivity and specificity of the test procedure with beta distributions. The comparison of adjusted VPCs between the intercept only and the fitted models with higher level covariates explained the portion of heterogeneity in the data that was accounted for by the covariates. 相似文献
15.
16.
Smith JR Legendre AM Thomas WB LeBlanc CJ Lamkin C Avenell JS Wall JS Hecht S 《Journal of the American Veterinary Medical Association》2007,231(8):1210-1214
CASE DESCRIPTION: An 8-year-old domestic shorthair cat was evaluated because of signs of depression, circling, and visual deficits. CLINICAL FINDINGS: The cat had no cutaneous lesions, and results of an ophthalmologic examination and thoracic radiography were within reference limits. Computed tomography of the brain revealed a mass lesion involving the right parietal, temporal, and occipital lobes; the mass was in broad-based contact with the skull and smoothly marginated and had strong homogenous enhancement after contrast agent administration. During craniectomy, samples of the mass were collected for cytologic and histopathologic evaluations and microbial culture. A diagnosis of Blastomyces dermatitidis-associated meningoencephalitis with secondary pyogranulomatous inflammation was made. TREATMENT AND OUTCOME: Amphotericin B (0.25 mg/kg [0.11 mg/lb], IV) was administered on alternate days (cumulative dose, 1.75 mg/kg [0.8 mg/lb]). To minimize the risk of nephrotoxicosis, assessments of serum biochemical variables (urea nitrogen and creatinine concentrations) and urinalyses were performed at intervals. The third dose of amphotericin B was postponed 48 hours because the cat became azotemic. The cat subsequently received fluconazole (10 mg/kg [4.5 mg/lb], PO, q 12 h) for 5.5 months. Six months after discontinuation of that treatment, the cat appeared healthy and had no signs of relapse. CLINICAL RELEVANCE: Brain infection with B dermatitidis is typically associated with widespread disseminated disease. The cat of this report had no evidence of systemic disease. Blastomycosis of the CNS should be considered as a differential diagnosis for brain lesions in cats from areas in which B dermatitidis is endemic. 相似文献
17.
18.
Ogunkoya Ayodele Kaplan Jed Whitlock Cathy Nanavati William Roberts David W. Poulter Benjamin 《Landscape Ecology》2021,36(12):3591-3606
Landscape Ecology - Widespread changes in forest structure and distribution have been documented in northern Patagonia over the past century. We employed LPJ-GUESS, a dynamic global... 相似文献
19.
20.
Vimal Nair Min Cheol Kim James A. Golen Arnold L. Rheingold Gabriel A. Castro Paul R. Jensen William Fenical 《Marine drugs》2020,18(11)
A new cytotoxic thiodepsipeptide, verrucosamide (1), was isolated along with the known, related cyclic peptide thiocoraline, from the extract of a marine-derived actinomycete, a Verrucosispora sp., our strain CNX-026. The new peptide, which is composed of two rare seven-membered 1,4-thiazepane rings, was elucidated by a combination of spectral methods and the absolute configuration was determined by a single X-ray diffraction study. Verrucosamide (1) showed moderate cytotoxicity and selectivity in the NCI 60 cell line bioassay. The most susceptible cell lines were MDA-MB-468 breast carcinoma with an LD50 of 1.26 µM, and COLO 205 colon adenocarcinoma with an LD50 of 1.4 µM. Also isolated along with verrucosamide were three small 3-hydroxy(alkoxy)-quinaldic acid derivatives that appear to be products of the same biosynthetic pathway. 相似文献