全文获取类型
收费全文 | 8422篇 |
免费 | 438篇 |
国内免费 | 9篇 |
专业分类
林业 | 602篇 |
农学 | 277篇 |
基础科学 | 63篇 |
1396篇 | |
综合类 | 1297篇 |
农作物 | 549篇 |
水产渔业 | 648篇 |
畜牧兽医 | 3150篇 |
园艺 | 216篇 |
植物保护 | 671篇 |
出版年
2023年 | 46篇 |
2022年 | 74篇 |
2021年 | 139篇 |
2020年 | 155篇 |
2019年 | 176篇 |
2018年 | 160篇 |
2017年 | 154篇 |
2016年 | 180篇 |
2015年 | 133篇 |
2014年 | 185篇 |
2013年 | 347篇 |
2012年 | 420篇 |
2011年 | 574篇 |
2010年 | 325篇 |
2009年 | 300篇 |
2008年 | 564篇 |
2007年 | 511篇 |
2006年 | 517篇 |
2005年 | 545篇 |
2004年 | 444篇 |
2003年 | 490篇 |
2002年 | 425篇 |
2001年 | 99篇 |
2000年 | 98篇 |
1999年 | 106篇 |
1998年 | 87篇 |
1997年 | 81篇 |
1996年 | 69篇 |
1995年 | 92篇 |
1994年 | 88篇 |
1993年 | 74篇 |
1992年 | 60篇 |
1991年 | 58篇 |
1990年 | 72篇 |
1989年 | 51篇 |
1988年 | 44篇 |
1987年 | 39篇 |
1986年 | 53篇 |
1985年 | 54篇 |
1984年 | 52篇 |
1983年 | 48篇 |
1982年 | 33篇 |
1980年 | 36篇 |
1979年 | 32篇 |
1978年 | 40篇 |
1977年 | 38篇 |
1976年 | 35篇 |
1975年 | 38篇 |
1974年 | 32篇 |
1973年 | 25篇 |
排序方式: 共有8869条查询结果,搜索用时 562 毫秒
971.
OBJECTIVE: To evaluate the combined diode laser cycloablation procedure and adjunctive Ahmed gonioimplant use in dogs with primary glaucoma. DESIGN: Retrospective study. ANIMALS: 48 dogs, 51 eyes with primary glaucoma. PROCEDURE: Medical records from two large private clinical ophthalmology services were reviewed. Signalment, duration of glaucoma, gonioscopic evaluation, laser power and duration settings, immediate postoperative and final intraocular pressure and visual results, short and long-term visual outcome, and surgical complications were recorded. RESULTS: The age range of affected dogs was 3.0-14.0 years, with a mean age of 7.5 +/- 2.6 years. Eleven pure breeds were represented, with the most common being the American Cocker Spaniel. The sex distribution was 22 neutered males, 1 intact male, 23 spayed females, and 2 intact female dogs. The right eye was affected in 33 cases, and the left eye in 18 cases. The average total joules, which was administered with the diode laser, was 109.6 +/- 23.6 J. Immediate surgical complications included fibrin formation in the anterior chamber (15), corneal ulcers (4), hyphema (7), and focal retinal detachment (1). Long-term complications included cataract formation (8 total, 2 of which were significant, vision-threatening), elevated intraocular pressure (IOP) (6), unstable gonioimplant (1), and glaucoma recurrence (14). Additional surgeries performed on the eyes over the course of study included: intrascleral prosthesis (4), enucleation (1), resection of fibrotic scar tissue (5), and repeat laser cycloablation (8). The dogs were examined for a mean follow-up time of 17.6 months (range: 2-83 months postoperatively). Twenty-nine cases were followed greater than one year. Vision was maintained in 42/51 eyes (82%) in the immediate short-term of this study. In all cases included in the study, good control of IOP was achieved in 39/51 (76%) of eyes, and IOP was poor or uncontrolled in 12/51 (24%) of eyes. Twenty out of 41 eyes (49%) maintained fair to excellent vision six months after surgery. Twelve months postoperative observations demonstrated that 12/29 (41%) of the eyes were still visual. CONCLUSIONS: In primary glaucoma, the combined procedure of laser diode cyclophotocoagulation and Ahmed valve implant was associated with return or maintenance of vision in 42/51 eyes (82%) in the immediate short-term of this study, and a long-term IOP control in 39/51 (76%) of the cases, with 12/29 eyes (41%) visual after 12 months. 相似文献
972.
German AJ Cannon MJ Dye C Booth MJ Pearson GR Reay CA Gruffydd-Jones TJ 《Journal of Feline Medicine and Surgery》2005,7(1):33-41
Four cases of oesophageal stricture subsequent to doxycycline administration are reported. All cases were young to middle age (median age 3 years; range 1-7 years), and either domestic shorthair or domestic longhair breed. In all cases the predominant clinical sign was regurgitation, which developed at variable times after doxycycline administration. In all cases the reason for doxycycline use was treatment or prophylaxis of suspected infections (Mycoplasma haemofelis, Chlamydophila felis or Bordetella bronchiseptica), and the duration of therapy was variable. In one case the stricture was definitively diagnosed at post mortem examination, in the three other cases, definitive diagnosis was by endoscopy. Balloon dilation was successful in the three cases that were treated. This is the largest case series, to date, of oesophageal disease in cats associated with doxycycline administration. Caution should be exercised when administering oral medication to cats, especially doxycycline, and should be accompanied either by a water or food swallow. 相似文献
973.
Four cats with fungal rhinitis 总被引:2,自引:0,他引:2
Fungal rhinitis is uncommon in the cat and cases of nasal aspergillosis-penicilliosis have been rarely reported. Signs of fungal rhinitis include epistaxis, sneezing, mucopurulent nasal discharge and exophthalmos. Brachycephalic feline breeds seem to be at increased risk for development of nasal aspergillosis-penicilliosis. Computed tomography (CT) imaging and rhinoscopy are useful in assessing the extent of the disease and in obtaining diagnostic samples. Fungal culture may lead to false negative or positive results and must be used in conjunction with other diagnostic tests. Serological testing was not useful in two cats tested. The cats in this study were treated with oral itraconazole therapy. When itraconazole therapy was discontinued prematurely, clinical signs recurred. Hepatotoxicosis is a possible sequel to itraconazole therapy. 相似文献
974.
Derek W. Gammon Mark A. Brown John E. Casida 《Pesticide biochemistry and physiology》1981,15(2):181-191
Pyrethroids are divided into two classes (Types I and II) based on their effects on the cercal sensory nerves recorded in vivo and in vitro and on the symptomology they produce in dosed cockroaches, Periplaneta americana. Type I compounds include pyrethrins, S-bioallethrin, [1R,cis]resmethrin, kadethrin, the 1R,trans and 1R,cis isomers of tetramethrin, phenothrin, and permethrin, and an oxime O-phenoxybenzyl ether. Electrophysiological recordings from dosed individuals reveal trains of cercal sensory spikes and sometimes also spike trains from the cercal motor nerves and in the CNS. Low concentrations of these pyrethroids act in vitro to induce repetitive firing in a cercal sensory nerve following a single electrical stimulus. This in vitro measurement, standardized for evaluating structure-activity relationships, shows that only 1R, insecticidal isomers are highly effective neurotoxins. The most potent compounds on the isolated nerve are [1R,trans]- and [1R,cis]tetramethrin, each active at 3 × 10?13M. The poisoning symptoms of Type I compounds are restlessness, incoordination, hyperactivity, prostration, and paralysis. Type II compounds include [1R,cis,αS]- and [1R,trans,αS]cypermethrin, deltamethrin, and [S,S]fenvalerate. These α-cyanophenoxybenzyl pyrethroids do not induce repetitive firing in the cercal sensory nerves either in vivo or in vitro; moreover, they cause different symptoms, including a pronounced convulsive phase. Two other pyrethroids with an α-cyano substituent, i.e., fenpropathrin and an oxime O-α-cyanophenoxybenzyl ether, are classified as Type I based on their action on a cercal sensory nerve but the symptoms with these compounds resemble Type II. The two classes of pyrethroid action evident with the cockroach are discussed relative to their neurophysiological effects and symptomology in other organisms. 相似文献
975.
Thin-layer and gas-liquid chromatography, ultraviolet analysis and bioassay with Chlorella spp. have been used to investigate the pathway of degradation of diuron to phytotoxic derivatives when diuron was used as a soil-residual herbicide in irrigation canals. Observations suggest that 1-(3,4-dichlorophenyl)-3-methylurea and 1-(3,4-dichlorophenyl)urea make a contribution to total residues equivalent to a maximum of about 40 and 55%, respectively, of diuron concentrations. Application of a phyto-toxicity rating suggests that in this environment, measurement of diuron specifically would underestimate the total phytotoxicity of residues by a maximum of about 7%. 相似文献
976.
John G. Davison 《Pest management science》1976,7(5):429-435
Convolvulus arvensis is the most important species of bindweed in Britain. Established plants spread by means of lateral roots: establishment from seed and fragments of the underground growth is not important. The hormone weedkillers like 2,4-D and MCPA give good control in the year of treatment. With the correct dose and timing there is also good control in the year after treatment. Adding paraquat to 2,4-D reduces the effect in the year after treatment. Repeated annual treatment with high doses of chlorthiamid that prevent shoot growth for the entire season are no more effective against the underground growth than the standard dose of 2,4-D. Calystegia sepium spreads rapidly by rhizomes and stolons. It is more susceptible than C. arvensis to MCPB. 相似文献
977.
Two wild oat herbicides, benzoylprop-ethyl and flamprop-methyl were administered to lactating cows at low dose levels (0.3–3.0 mg/kg in total diet) and the excretion of total metabolites in milk, urine and faeces was measured. Total residues in tissues were also determined. Similarly a third and related herbicide flamprop-isopropyl was fed to cows, pigs and hens (at 0.5 mg/kg in total diet) and the residues were determined in excreta and tissues, including eggs. The amounts of the compounds fed were equivalent to approximately 10–300 times the total residue found in cereal treated in the field. Residues in milk in most cases were well below 0.001 mg/kg; in muscle samples <0.003 mg/kg; and in eggs, 0.0008 mg/kg, decreasing by 50% in approximately 3 days to 0.0001 mg/kg 4 days after the termination of treatment. Elimination of the herbicides from the animals was rapid in every case and this, together with the low residue levels, was attributed to very efficient metabolic de-esterification to the parent carboxylic acid metabolites (benzoylprop and flamprop). These metabolites possess physical properties ideally suited for excretion via the kidneys and bile into urine and faeces and, conversely, unsuited for transport into milk and eggs. 相似文献
978.
Chas. A. Mitchell L. F. Guerin John Robillard 《Canadian journal of veterinary research》1968,32(4):544-546
The decay rate of six strains of Influenza virus Type A of human origin and eight strains of avian origin were examined in aerosol form under fixed conditions of temperature and humidity. Strains of avian origin were demonstrated to have greater resistance to decay of viability. 相似文献
979.
980.
John A. Johnson Mrs. Yu-Yen Linko 《Plant foods for human nutrition (Dordrecht, Netherlands)》1964,11(2-4):256-268
Summary Organic compounds present in minute quantities are responsible for bread flavor profile. Organic acids, alcohols, esters and carbonyl compounds have been identified and estimated, quantitatively, by use of paper, column and vapor-phase chromatography. Because of the minute quantities of most organic flavor constituents, some system of extraction and concentration must be employed for successful analysis. Separation into classes and concentration is best accomplished by formation of derivatives. Developing solvents, carrier system, and techniques of chromatography must be carefully selected for each group of compounds. Success in the analysis of bread flavor constituents has been significant in recent years because of the development of chromatography techniques.
with 4 figs.
Contribution no. 424, Department of Flour and Feed Milling Industries, Kansas State Agricultural Experiment Station, Manhattan, Kansas, U.S.A. 相似文献
Zusammenfassung Die Geschmackseigenschaften von Brot werden durch in sehr geringen Mengen vorhandene organische Verbindungen bedingt. Mittels Papier-, Säulen- und Gaschromatographie wurden organische Säuren, Alkohole, Ester und Karbonylverbindungen ermittelt und mengenmäßig bestimmt. Die äußerst geringen Mengen der Mehrzahl der organischen Geschmackskomponenten können nur mit einer Methode, die Extraktion und Konzentration umfaßt, erfolgreich analysiert werden. Diese Trennung in Gruppen und Konzentration wird am besten über die Bildung von Sekundärverbindungen erreicht. Hierbei muß für jede Gruppe von Komponenten eine sehr sorgfältige Auswahl der Entwicklungslösungen, der Vektorsysteme und der chromatographischen Technik getroffen werden. Die bedeutenden Fortschritte der chromatographischen Techniken der letzten Jahre sind der Grund für die Erfolge auf dem Gebiete der Analyse der Geschmackskomponenten von Brot.
Résumé Des composés organiques, présents en très faible quantités, régissent le profil de saveur du pain. Des acides organiques, des alcools, des esters et des composés carbonyliques ont été identifiés, et évalués, quantitativement par chromatographie sur papier, sur colonne, et en phase vapeur. Du fait des faibles quantités de la plupart des composants organiques de saveur, un système d'extraction et de concentration doit être utilisé pour réussir les analyses. La séparation en classes et la concentration peut être obtenue de façon la meilleure par formation de dérivés. Les solvants de développement, les systèmes vecteurs, et les techniques de chromatographie, doivent être soigneusement selectionnés pour chaque groupe de composants. Les réussites dans le domaine de l'analyse des composants de la saveur du pain ont été significatives ces dernières années, du fait du développement des techniques chromatographiques,
with 4 figs.
Contribution no. 424, Department of Flour and Feed Milling Industries, Kansas State Agricultural Experiment Station, Manhattan, Kansas, U.S.A. 相似文献