全文获取类型
收费全文 | 14857篇 |
免费 | 385篇 |
国内免费 | 27篇 |
专业分类
林业 | 631篇 |
农学 | 806篇 |
基础科学 | 139篇 |
2009篇 | |
综合类 | 1672篇 |
农作物 | 495篇 |
水产渔业 | 1054篇 |
畜牧兽医 | 7060篇 |
园艺 | 229篇 |
植物保护 | 1174篇 |
出版年
2023年 | 97篇 |
2021年 | 92篇 |
2020年 | 129篇 |
2019年 | 206篇 |
2018年 | 376篇 |
2017年 | 346篇 |
2016年 | 334篇 |
2015年 | 308篇 |
2014年 | 325篇 |
2013年 | 576篇 |
2012年 | 481篇 |
2011年 | 574篇 |
2010年 | 465篇 |
2009年 | 420篇 |
2008年 | 555篇 |
2007年 | 578篇 |
2006年 | 476篇 |
2005年 | 518篇 |
2004年 | 405篇 |
2003年 | 449篇 |
2002年 | 359篇 |
2001年 | 758篇 |
2000年 | 720篇 |
1999年 | 589篇 |
1998年 | 171篇 |
1997年 | 164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 | 290篇 |
1989年 | 265篇 |
1988年 | 271篇 |
1987年 | 319篇 |
1986年 | 245篇 |
1985年 | 193篇 |
1984年 | 170篇 |
1983年 | 147篇 |
1982年 | 94篇 |
1981年 | 83篇 |
1980年 | 79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 20 毫秒
161.
Phosphate-solubilizing microorganisms associated with the rhizosphere of mangroves in a semiarid coastal lagoon 总被引:14,自引:0,他引:14
P. Vazquez G. Holguin M. E. Puente A. Lopez-Cortes Y. Bashan 《Biology and Fertility of Soils》2000,30(5-6):460-468
The phosphate-solubilizing potential of the rhizosphere microbial community in mangroves was demonstrated when culture media
supplemented with insoluble, tribasic calcium phosphate, and incubated with roots of black (Avicennia germinans L.) and white [Laguncularia racemosa (L.) Gaertn.] mangrove became transparent after a few days of incubation. Thirteen phosphate-solubilizing bacterial strains
were isolated from the rhizosphere of both species of mangroves: Bacillus amyloliquefaciens, Bacillus licheniformis, Bacillus atrophaeus, Paenibacillus macerans, Vibrio proteolyticus, Xanthobacter agilis, Enterobacter aerogenes, Enterobacter taylorae, Enterobacter asburiae, Kluyvera cryocrescens, Pseudomonas stutzeri, and Chryseomonas luteola. One bacterial isolate could not be identified. The rhizosphere of black mangroves also yielded the fungus Aspergillus niger. The phosphate-solubilizing activity of the isolates was first qualitatively evaluated by the formation of halos (clear zones)
around the colonies growing on solid medium containing tribasic calcium phosphate as a sole phosphorus source. Spectrophotometric
quantification of phosphate solubilization showed that all bacterial species and A. niger solubilized insoluble phosphate well in a liquid medium, and that V. proteolyticus was the most active solubilizing species among the bacteria. Gas chromatographic analyses of cell-free spent culture medium
from the various bacteria demonstrated the presence of 11 identified, and several unidentified, volatile and nonvolatile organic
acids. Those most commonly produced by different species were lactic, succinic, isovaleric, isobutyric, and acetic acids.
Most of the bacterial species produced more than one organic acid whereas A. niger produced only succinic acid. We propose the production of organic acids by these mangrove rhizosphere microorganisms as a
possible mechanism involved in the solubilization of insoluble calcium phosphate.
Received: 21 April 1999 相似文献
162.
Mediterranean fruit fly, Ceratitis capitata (Wied.), is a major pest of fruits and vegetables throughout the region, reduces yield of marketable fruit and limits exports. The Arava Medfly Eradication Project (AMEP) was initiated in 1997, and serves as a pilot effort to begin implementing the sterile insect technique in the Near East. It could become a model for future implementation of the proposed EASTMED project, a plan conceived and planned by the International Atomic Energy Agency in 1994–1995 with input of regional experts. The target area lies in the Arava Valley between the Dead Sea and the Red Sea. AMEP activities include host mapping, population monitoring and suppression followed by weekly releases of sterile flies. This project will lead to permanent establishment and maintenance of Medfly free areas. In addition, new technologies are being tested under local conditions. This includes use of tsl male-only strains of medflies, aerial releases with a chilled insect release machine, female attractants and new trap designs. At present, the project relies upon long-distance shipping of pupae from Madeira, Portugal and Guatemala rather than local sources. The medfly population on the Israeli side of the Arava valley, was monitored in 132 trimedlure loaded traps. It dropped by July 1999 to 0.04 flies per trap per day from the pre-eradication level of 0.71 flies per trap per day in July 1998. In June 1999, only 19% of the traps captured wild flies as compared to 40% of the traps in June 1997. As medfly does not respect international boundaries, transboundary co-operation is a key factor for successful implementation. Current project status and plans for future expansion within Israel, Jordan and the Palestinian Authority will be presented. 相似文献
163.
K Stafford Y Stafford D Paton P Gamble 《Revue d'élevage et de médecine vétérinaire des pays tropicaux》1992,45(3-4):229-230
Blood samples were taken from 121 sows and gilts on 7 commercial piggeries located around Lusaka (Zambia). The samples tested negative for antibodies to Aujeszky's disease, transmissible gastroenteritis (TGE), swine influenza, hog cholera and brucellosis. Seventy-eight pigs from 5 farms had positive titres to porcine parvovirus. Eighteen sera showed positive titres to Leptospira celledoni. 相似文献
164.
Andrew Y. Li Felix D. Guerrero John H. Pruett 《Pesticide biochemistry and physiology》2007,87(2):147-155
Resistance to insecticides remains a major problem for the successful control of the horn fly, Haematobia irritans irritans (L.), one of the most important pests of cattle in many countries including the United States. The organophosphate (OP) insecticide diazinon has been used to control pyrethroid-resistant populations of the horn fly. There are only a few reported cases of horn fly resistance to diazinon in the United States and Mexico. Piperonyl butoxide (PBO) has been used successfully as a synergist of pyrethroid insecticides to control horn flies. PBO-synergized diazinon products are also available for horn fly control in the United States, although PBO is known to inhibit the bio-activation of certain OP insecticides including diazinon. A study was conducted to evaluate the effect of PBO on diazinon toxicity to horn flies using a filter paper bioassay technique. These bioassays in both the susceptible and diazinon-resistant horn fly strains revealed a biphasic effect of PBO on diazinon toxicity to horn flies. PBO inhibited diazinon toxicity when the PBO concentration used was high (5%), and no effect was observed when PBO concentration was intermediate (2%). However, at low concentrations (1% and lower), PBO significantly synergized diazinon toxicity. We demonstrated that enhanced esterase activity was associated with survivability of horn flies exposed to diazinon alone. PBO has been shown to inhibit esterase activity in other insect species. However, results of biochemical assays with esterases from this study suggest that PBO did not have significant effect on the overall esterase activity in the horn fly. The observed synergistic effect of PBO at lower concentrations on diazinon toxicity to horn flies could not be explained by reduced esterase activity due to PBO inhibition. It is likely that PBO synergized diazinon toxicity at lower concentrations by facilitating penetration of diazinon through the cuticle and/or inhibiting the oxidative detoxification of diazinon, and reduced diazinon toxicity at high PBO concentration by inhibiting the bio-activation of diazinon. 相似文献
165.
A. E. Poulin Braim R. J. W. Bell J. A. Textor W. Y. Lo S. M. Puchalski L. D. Galuppo 《Equine Veterinary Education》2010,22(6):290-295
A 2‐year‐old Thoroughbred filly presented to the William R. Pritchard Veterinary Medical Teaching Hospital at the University of California at Davis for whole body nuclear scintigraphic evaluation after an acute onset of nonweightbearing right hindlimb lameness post race. The use of computed tomography (CT) enabled visualisation of additional pathology that was not initially appreciable using combined imaging modalities of nuclear scintigraphy and digital radiography, which ultimately altered the selected course of treatment. Computed tomography in horses with fractures of the cuboidal bones of the hock can provide valuable additional information regarding fracture configuration and radiographically occult pathology, which may help to guide clinical decisions about treatment. 相似文献
166.
Artificial infection by transplantation of juvenile Fasciola worms into the abdominal cavity of rats
H Saeki N Taira Y Tomishita T Ishii 《Nippon juigaku zasshi. The Japanese journal of veterinary science》1989,51(1):151-156
Rats were successfully infected with Japanese Fasciola sp. by transplantation of juvenile worms (JW) or metacercariae (MC) into the abdominal cavity. Moreover, the rat was investigated on its suitability for different experiments with liver flukes. JWs or MCs transplanted intraperitoneally (IP) matured in the bile duct of rats. Moreover, more stable infections were established by inoculation of JWs than MCs. About 3 of 10-15 JWs transplanted into the abdominal cavity of a rat matured and laid eggs in the bile duct. The mean prepatent period was 63.5 days in the JW inoculated group. EPG values were kept constant at a level of 10(2)-10(3) about 100 to 230 days after the transplantation of JWs. The life span of Japanese liver flukes was estimated to be about 400 days in rats. From these results, it was concluded that the rat is suitable for various experiments with Fasciola sp. 相似文献
167.
Grigera SA Perry RS Schofield AJ Chiao M Julian SR Lonzarich GG Ikeda SI Maeno Y Millis AJ Mackenzie AP 《Science (New York, N.Y.)》2001,294(5541):329-332
The concept of quantum criticality is proving to be central to attempts to understand the physics of strongly correlated electrons. Here, we argue that observations on the itinerant metamagnet Sr3Ru2O7 represent good evidence for a new class of quantum critical point, arising when the critical end point terminating a line of first-order transitions is depressed toward zero temperature. This is of interest both in its own right and because of the convenience of having a quantum critical point for which the tuning parameter is the magnetic field. The relationship between the resultant critical fluctuations and novel behavior very near the critical field is discussed. 相似文献
168.
W. S. Tsai Y. C. Huang D. Y. Zhang K. Reddy S. H. Hidayat W. Srithongchai S. K. Green F. -J. Jan 《Plant pathology》2008,57(3):408-416
Twenty-four isolates of Chilli veinal mottle virus (ChiVMV) from China, India, Indonesia, Taiwan and Thailand were analysed to determine their genetic relatedness. Pathogenicity of virus isolates was confirmed by induction of systemic mosaic and/or necrotic ringspot symptoms on Capsicum annuum after mechanical inoculation. The 3' terminal sequences of the viral genomic RNA were determined. The coat protein (CP) coding regions ranged from 858 to 864 nucleotides and the 3' untranslated regions (3'UTR) from 275 to 289 nucleotides in length. All isolates had the inverted repeat sequence GUGGNNNCCAC in the 3'UTR. The DAG motif, conserved in aphid-transmitted potyviruses, was observed in all isolates. All 24 isolates were considered as belonging to ChiVMV because of their high CP amino acid and nucleotide identity (more than 94·8 and 89·5%, respectively) with the reported ChiVMV isolates including the pepper vein banding virus (PVBV), the chilli vein-banding mottle virus (CVbMV) and the CVbMV Chiengmai isolate (CVbMV-CM1). Based on phylogenetic analysis, ChiVMV isolates including all 24 isolates tested, PVBV, CVbMV and CVbMV-CM1 can be classified into three groups. In addition, a conserved region of 204 amino acids with more than 90·2% identity was identified in the C terminal of the CP gene of ChiVMV and Pepper veinal mottle virus (PVMV), and may explain the serological cross reaction between these two viruses. The conserved region may also provide useful information for developing transgenic resistance to both ChiVMV and PVMV. 相似文献
169.
Han JH Krochta JM Hsieh YL Kurth MJ 《Journal of agricultural and food chemistry》2000,48(11):5658-5665
Lactitol-based cross-linked hydrogel was synthesized, and model proteins (alpha-chymotrypsin, beta-lactoglobulin, bovine serum albumin (BSA), and gamma-globulin) were incorporated into the cross-linked hydrogel. The larger-molecular-weight proteins have lower diffusivity (D(e)) in the hydrogel. Increasing temperature accelerated the diffusion rate of proteins; however, the diffusion did not follow the Arrhenius equation at temperatures above 37 degrees C. The swelling ratio of the hydrogel was slightly decreased after heating for 2 h at 37 and 45 degrees C, and significantly reduced after 1 h at 60 degrees C. Therefore, diffusion of beta-lactoglobulin and BSA may be decreased by hydrogel shrinking at temperature over 37 degrees C. The model proteins have high affinities to buffer solution compared to the hydrogel network structure, resulting in high partition coefficients (K > 1) which do not affect the calculation of D(e) values. Incorporated protein release follows the theory of hindered diffusion. 相似文献
170.