首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   466篇
  免费   18篇
  国内免费   4篇
林业   31篇
农学   20篇
基础科学   4篇
  139篇
综合类   65篇
农作物   30篇
水产渔业   16篇
畜牧兽医   91篇
园艺   31篇
植物保护   61篇
  2023年   6篇
  2022年   10篇
  2021年   8篇
  2020年   9篇
  2019年   10篇
  2018年   14篇
  2017年   12篇
  2016年   16篇
  2015年   14篇
  2014年   18篇
  2013年   22篇
  2012年   28篇
  2011年   37篇
  2010年   25篇
  2009年   19篇
  2008年   34篇
  2007年   24篇
  2006年   35篇
  2005年   20篇
  2004年   19篇
  2003年   20篇
  2002年   19篇
  2001年   5篇
  2000年   4篇
  1999年   3篇
  1998年   7篇
  1997年   2篇
  1996年   3篇
  1995年   6篇
  1993年   4篇
  1992年   2篇
  1991年   2篇
  1990年   2篇
  1987年   3篇
  1982年   3篇
  1981年   1篇
  1978年   2篇
  1976年   1篇
  1975年   2篇
  1965年   1篇
  1961年   1篇
  1960年   1篇
  1958年   3篇
  1956年   1篇
  1955年   1篇
  1954年   1篇
  1945年   1篇
  1939年   3篇
  1937年   1篇
  1936年   1篇
排序方式: 共有488条查询结果,搜索用时 15 毫秒
91.
92.
Ohne Zusammenfassung Recherches effectuées en 1938 sur la jaunisse, les taches noires, la formation d’anthocyanine et l’analyse de l’amidon chez la betterave  相似文献   
93.
Instability of the nuclear genome is a hallmark of cancer and aging. MMS19 protein has been linked to maintenance of genomic integrity, but the molecular basis of this connection is unknown. Here, we identify MMS19 as a member of the cytosolic iron-sulfur protein assembly (CIA) machinery. MMS19 functions as part of the CIA targeting complex that specifically interacts with and facilitates iron-sulfur cluster insertion into apoproteins involved in methionine biosynthesis, DNA replication, DNA repair, and telomere maintenance. MMS19 thus serves as an adapter between early-acting CIA components and a subset of cellular iron-sulfur proteins. The function of MMS19 in the maturation of crucial components of DNA metabolism may explain the sensitivity of MMS19 mutants to DNA damage and the presence of extended telomeres.  相似文献   
94.
Osteoarthritis belongs to the most common joint diseases in humans and animals and shows increased incidence in older patients. The bioactivities of collagen hydrolysates, sulfated glucosamine and a special fatty acid enriched dog-food were tested in a dog patient study of 52 dogs as potential therapeutic treatment options in early osteoarthritis. Biophysical, biochemical, cell biological and molecular modeling methods support that these well-defined substances may act as effective nutraceuticals. Importantly, the applied collagen hydrolysates as well as sulfated glucosamine residues from marine organisms were strongly supported by both an animal model and molecular modeling of intermolecular interactions. Molecular modeling of predicted interaction dynamics was evaluated for the receptor proteins MMP-3 and ADAMTS-5. These proteins play a prominent role in the maintenance of cartilage health as well as innate and adapted immunity. Nutraceutical data were generated in a veterinary clinical study focusing on mobility and agility. Specifically, key clinical parameter (MMP-3 and TIMP-1) were obtained from blood probes of German shepherd dogs with early osteoarthritis symptoms fed with collagen hydrolysates. Collagen hydrolysate, a chondroprotective food supplement was examined by high resolution NMR experiments. Molecular modeling simulations were used to further characterize the interaction potency of collagen fragments and glucosamines with protein receptor structures. Potential beneficial effects of collagen hydrolysates, sulfated glycans (i.e., sulfated glucosamine from crabs and mussels) and lipids, especially, eicosapentaenoic acid (extracted from fish oil) on biochemical and physiological processes are discussed here in the context of human and veterinary medicine.  相似文献   
95.
Ancylostoma ceylanicum is a common zoonotic hookworm of dogs and cats throughout Asia and has also been reported to occur within the Australasian region. The aim of this study to was to determine the efficacy of a spot-on formulation containing emodepside and praziquantel (Profender®, Bayer) and praziquantel and pyrantel oral tablets (Drontal® for Cats, Bayer) against experimental A. ceylanicum infections in cats.Twenty-four kittens were each subcutaneously injected with 100 infective third-stage larvae of A. ceylanicum. Kittens were stratified by egg count and randomly allocated equally into control and two treatment groups. The first group were treated with emodepside 2.1%/praziquantel 8.6% (Profender®, Bayer) at the recommended label dose. The second group was treated with 80 mg pyrantel and 20 mg praziquantel (Drontal® for Cats, Bayer) at the recommended label dose. The kittens in the control group were not treated. Egg counts were performed daily until the end of the study period and compared for the treated and control groups. No eggs were detected in the treated group of kittens within 4 days of treatment and faecal samples from this group remained negative throughout the rest of the study, resulting in a treatment efficacy (egg reduction) of 100% (P < 0.0001). The egg counts remained high (993 ± 666 epg) in the untreated control group for the rest of the study period. This study demonstrated that both combination products containing topical emodepside/praziquantel (Profender®, Bayer) and praziquantel/pyrantel oral tablets (Drontal® for Cats, Bayer) given at the recommended dose is highly effective against infection with A. ceylanicum in cats.  相似文献   
96.
ABSTRACT

Disease development in plants is strongly dependent on weather conditions, with temperature playing a particularly significant role by influencing latency period duration. Using two models describing the relationship between latency period and temperature, we performed simulations aimed at predicting changes in the latency period of leaf rust (Puccina recondita f. sp. tritici) on triticale in response to expected climate change. The simulations were based on meteorological data recorded in the period 1986–2005 at locations representing 16 provinces in Poland and based on values obtained after transformation of the observed data to reflect temperature changes under four scenarios (RCP2.6, RCP4.5, RCP6.0 and RCP8.5) according to the giss_e2_r climate model. In all scenarios, the results for the two triticale cultivars studied, Witon (vulnerable to P. recondita) and Gniewko (less susceptible), showed a threat of faster development (shorter leaf rust latency period) on triticale triggered by climate change in south-east and south-central Poland than in other regions. The results also showed an increased probability of future regional diversification of leaf rust latency period duration on vulnerable triticale cultivars, opportunities for earlier start of leaf rust epidemics on triticale in Poland and an increase in ?nal disease severity in comparison with 1986–2005.  相似文献   
97.
Chemical and biological sedimentary records of a high alpine lake were used to reconstruct palaeoecological conditions and compared with two centuries of instrumental temperature measurements. Air temperature determined the lake water pH throughout the past 200 yr almost regardless of the level of atmospheric deposition. Our data suggest a strong climate forcing of the acid-base balance in sensitive high-altitude lakes. Their physico-chemical conditions and biota strongly depend on the duration of ice and snow cover which is significantly different between warm and cold periods. Beside changes in weathering rates, in-lake alkalinity generation and water-retention time, delayed freezing in autumn and earlier ice-out dates with a shorter duration of CO2 over-saturation could be crucial for the tight temperature-pH coupling.  相似文献   
98.
水稻"三控"施肥技术规程   总被引:25,自引:9,他引:25  
从氮肥总量控制、氮肥的分阶段调控、磷钾肥的施用和其他配套技术等方面,介绍了水稻"三控"施肥技术规程:并指出应用水稻"三控"施肥技术规程中应注意的问题.  相似文献   
99.
Journal of Plant Diseases and Protection - In the Lower Elbe region of Northern Germany, low levels of fungicide resistance were recorded among Botrytis isolates obtained from blossom-end rot...  相似文献   
100.

Background

A leptin-like immunoreactive substance has been found in chicken eggs and has been implicated in serving as a maternal signal to program offspring growth and metabolism. In the present study, we investigated the effects of in ovo leptin administration on hatch weight, serum and hepatic concentrations of metabolites and hormones, as well as on the expression of genes involved in hepatic lipid metabolism and the predicted microRNAs (miRNAs) targeting the affected genes. To this end we injected fertile eggs with either 0.5 μg of recombinant murine leptin or vehicle (PBS) before incubation.

Results

Prenatally leptin-exposed chicks showed lower hatch weight, but higher liver weight relative to the body weight, compared to the control group. In ovo leptin treatment increased the hepatic content and serum concentration of leptin in newly hatched chickens. The hepatic contents of triglycerides (TG) and total cholesterol (Tch) were decreased, whereas the serum levels of TG, Tch and apolipoprotein B (ApoB) were increased. The hepatic mRNA expression of sterol regulator element binding protein 1 (SREBP-1c), SREBP-2, hydroxy-3-methylglutaryl coenzyme A reductase (HMGCR) and cholesterol 7α-hydroxylase 1 (CYP7A1) was significantly up-regulated, as was the protein content of both SREBP-1c and SREBP-2 in hepatic nuclear extracts of leptin-treated chickens. Moreover, out of 12 miRNAs targeting SREBP-1c and/or HMGCR, five were significantly up-regulated in liver of leptin-treated chicks, including gga-miR-200b and gga-miR-429, which target both SREBP-1c and HMGCR.

Conclusions

These results suggest that leptin in ovo decreases hatch weight, and modifies hepatic leptin secretion and lipid metabolism in newly hatched broiler chickens, possibly via microRNA-mediated gene regulation.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号