全文获取类型
收费全文 | 23402篇 |
免费 | 371篇 |
国内免费 | 774篇 |
专业分类
林业 | 4381篇 |
农学 | 2385篇 |
基础科学 | 745篇 |
3920篇 | |
综合类 | 2745篇 |
农作物 | 2544篇 |
水产渔业 | 2121篇 |
畜牧兽医 | 1995篇 |
园艺 | 1319篇 |
植物保护 | 2392篇 |
出版年
2024年 | 30篇 |
2023年 | 94篇 |
2022年 | 253篇 |
2021年 | 295篇 |
2020年 | 270篇 |
2019年 | 326篇 |
2018年 | 2966篇 |
2017年 | 2964篇 |
2016年 | 1450篇 |
2015年 | 379篇 |
2014年 | 298篇 |
2013年 | 353篇 |
2012年 | 1275篇 |
2011年 | 2559篇 |
2010年 | 2524篇 |
2009年 | 1626篇 |
2008年 | 1675篇 |
2007年 | 1916篇 |
2006年 | 388篇 |
2005年 | 438篇 |
2004年 | 275篇 |
2003年 | 296篇 |
2002年 | 234篇 |
2001年 | 190篇 |
2000年 | 184篇 |
1999年 | 169篇 |
1998年 | 172篇 |
1997年 | 95篇 |
1996年 | 119篇 |
1995年 | 104篇 |
1994年 | 112篇 |
1993年 | 110篇 |
1992年 | 90篇 |
1991年 | 60篇 |
1990年 | 77篇 |
1989年 | 62篇 |
1988年 | 47篇 |
1987年 | 14篇 |
1986年 | 11篇 |
1985年 | 2篇 |
1984年 | 6篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1981年 | 5篇 |
1977年 | 4篇 |
1968年 | 4篇 |
1964年 | 2篇 |
1962年 | 2篇 |
1961年 | 2篇 |
1895年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
91.
应用光镜和透射电镜观察,恒河猴肾上腺皮质可分为球状带、束状带和网状带。其特点是:(1)被膜较发达,有时可伸入球状带将其细胞分隔为团块。(2)球状带有时呈指状指入束状带和网状带,其内可见嗜铬细胞;球状带细胞可分为明、暗2种类型,他们排列成团球状、滤泡状、索状和不规则形。(3)网状带较发达,有的可分为内、外2个区;有时网状带呈刺状伸入束状带;有时网状带细胞可见于被膜下或髓质内。(4)有时部分被膜连同皮质一起呈指状伸入髓质内。(5)皮质细胞均含丰富的溶酶体、线粒体和内质网,但不同部位的细胞所含的脂滴在数量、大小、形态和电子密度等方面存在差异。 相似文献
92.
1发病情况山东费县探沂镇碗窑村史某 ,从安徽购进98头长白仔猪 ,由于天气不好 ,误了运输时间 ,一周才到家 ,运回家后死亡4头 ,途中每天喂两次 ,车上铺厚厚垫草 ,猪多拥挤 ,没有活动余地 ,回家后仔猪虚弱全部发病 ,体温升高 ,拉稀 ,呈水样 ,颜色为黄、灰绿色 ,尿黄。根据临床症状 ,剖检变化 ,以及流行病学初步诊断为长途运输引起的猪伤寒病。2临床症状仔猪精神不振 ,喜卧草垛中 ,寒战 ,全部不食 ,鼻颈无汗 ,眼结膜发红 ,被毛粗乱 ,脱水十分严重 ,体温40~41℃ ,脉搏85次/分 ,呼吸32次/分 ,腹泻呈黄、灰绿色 ,尿液黄 ,有的肛门… 相似文献
93.
Ribonuclease 6 (RNase6 or RNase K6) is a protein that belongs to a superfamily thought to be the sole verte‐brate‐specific enzyme known for a wide range of physiological functions, including digestion, cytotoxicity, angiogenesis, male reproduction and host defense. In our study, 51 functional genes and 11 pseudogenes were identified from 27 Rodentia species. Intriguingly, in the 3 main lineages of rodents there were multiple RNase6s identified in all species of Ctenohystrica, whereas only a single RNase6 was observed in other Rodentia species examined except for 2 species in the mouse‐related clade. The evolutionary scenario of “birth (gene duplication) and death (gene deactivation)” and gene sorting have been demonstrated in Ctenohystrica. In addition, bursts of positive selection, diversification of isoelectric point and positive net charge have been identified in Ctenohystrica, especially at two key sites that are involved in antimicrobial function. Site Trp30 has undergone positive selection and Ile45 has changed into other residues in Group B and Group C of the Ctenohystrica. Our results demonstrated a complex and intriguing evolutionary pattern of rodent RNase6, and indicated that functional modification may have occurred, which establishes an important theoretical foundation for future functional assays in rodent RNase6. 相似文献
94.
阿托品(atropine)是兽医临床常用抗胆碱药物,超量及非法使用易造成其在动物源性食品中大量残留,从而影响消费者健康。为减少残留对消费者的危害,探究残留检测方法十分必要。本文从其主要检测方法——分光光度法、高效液相色谱法和仪器联用法入手,简述了各种方法的研究进展并总结出各自的特性。分光光度法灵敏度高、操作简便,可用于基层阿托品残留检测;高效液相色谱法和仪器联用法准确度与灵敏度高,但这两种方法使用仪器较多,对操作人员要求高,在基层检测中受到很大限制。因此,建立更加快速、操作简单、低成本的免疫学方法具有十分重要的意义。 相似文献
95.
After very hot summer, 22 sheep from 5 different flocks consisting of approximately 150-200 animals each were diagnosed with facial eczema in September 2005, in southwest Turkey. Photophobia, corneal opacity, severe ulcers of the facial skin, especially localized around the eyes and mouth, and 3% mortality were the most prominent clinical symptoms. GGT levels of the animals were very high and varying between 261- 328 U/l. While the activities of ALT and total bilirubin were elevated and AST was normal in affected sheep. Total bilirubin level was higher than normal. Seven of the 22 sheep were euthanatized and necropsy was performed on all of these animals. Severe icterus, hepatomegaly, enlarged gallbladder, congestion of mesenteric vessels were the common necropsy findings. Histopathological changes of the liver included necrosis of the hepatocytes, cholangiohepatitis characterized by mononuclear inflammatory cell infiltrate in the portal area and mild to severe fibrosis around bile ducts. A diagnosis of sporidesmin toxicosis was made based on the histopathology of the livers, the elevation in liver enzymes, and the development of cutaneous lesions consistent with photosensitization and high spore counts in the ruminal contents. Surviving sheep were treated with procaine penicillin + dihidrostreptomycin sulfate, multivitamin complexes and flunixin meglumine. Additionally, zinc sulphate was also given at a dose of 6 gr per 100 lt drinking water for 28 days. All treated sheep recovered. Pasture spore counts were between 96,300- 267,500 spores/g grass. 相似文献
96.
Shahbazfar AA Mardjanmehr SH Arab HA Rassouli A Abdollahi M 《Tropical animal health and production》2011,43(4):843-849
Artemisinin has been used for centuries to treat malaria, intestinal tract helminthosis, diarrhea, and used as an antipyretic
and sedative agent, but the usage in veterinary medicine is a new field. Recently, it has been used successfully to control
experimental poultry coccidiosis. The present study aimed to determine the effects of different doses of artemisinin in broiler
chickens with chronic usage. Sixty birds divided into one control and four treatment groups that fed rations mixed with artemisinin
at doses of 17, 34, 68, and 136 ppm for 36 days. During the experiment, birds showed no clinical signs except anemia. In microscopic
examinations, heart, lung, and spleen had no lesion, but liver, kidney, and brain showed various lesions. Degenerative lesions
like intracytoplasmic eosinophilic inclusions were seen in both kidney and liver but fatty change was seen only in liver.
There was no relationship between severity of the liver lesions and drug dosage. Central chromatolysis, scattered neuronal
necrosis, and mild spongy changes were observed in five regions of the brain that were chosen for sectioning (motor cortex,
cerebellar nuclei, midbrain nuclei, and hindbrain nuclei at two separate levels). Severity of lesions in brain was dose-dependent,
and cerebral cortex was the most vulnerable area. Haematologic tests showed lower values for hematocrit and red blood cell
count dose-dependently. In conclusion, artemisinin is a promising drug for prevention and control of coccidiosis in broiler
chickens and its side effects are not too much serious especially at therapeutic doses. 相似文献
97.
Brucellosis caused by Brucella abortus in domestic water buffaloes (Bubalus bubalis) raised under the traditional system of husbandry in northern India was diagnosed using an enzyme-linked immunosorbent assays
(ELISA) with a Protein-G-based indicator system (Protein-G ELISA). A total of 1,551 animals that are positive (N = 61), negative (N = 243), and suspected (N = 1,247) for brucellosis were examined. Rose bengal test (RBT) was used to predict the disease, and accordingly, animals
were dichotomized in positive and negative population for receiver operating characteristic (ROC) curve analysis to determine
the sensitivity, the specificity, and the performance index of Protein-G ELISA. Taking all animals (N=1551) into account, the ROC curve analysis revealed cut off value of 29.6% positivity (%P) with 98.40% and 94.94%, sensitivity
and specificity, respectively. The results were compared with ELISA in which anti-bovine conjugate was used. The cut off in
ELISA was 37.9%P and sensitivity and specificity were 96.26% and 97.07%, respectively. The performance indexes of both the
assays were almost equal and were 193.34 for Protein-G ELISA and 193.33 for ELISA. The cut off values of both the tests changed,
if only known positive (N = 61) and known negative (N=243) animals were used for ROC curve analysis, and accordingly, changes in sensitivity and specificity were observed with
significant decrease of performance indexes of both the tests. The high optical density (P<0.0001) background signal with negative serum control and high %P (P<0.0001) in sera from negative population were noticed in ELISA in comparison to Protein-G ELISA. 相似文献
98.
Nagamine MK Sanches DS Pinello KC Torres LN Mennecier G Latorre AO Fukumasu H Dagli ML 《Veterinary research communications》2011,35(6):391-399
Mast cell tumor (MCT) is one of the most prevalent neoplasms that affect skin and soft tissue in dogs. Because mast cell tumors
present a great variety of clinical appearance and behavior, their treatment becomes a challenge. Trichostatin A (TSA), an
antifungal antibiotic, has shown inhibitory effects on the proliferation and induction of apoptosis in various types of cancer
cells. In order to evaluate the potential of trichostatin A as a therapeutic drug, cells of grade 3 MCT were cultured and
treated with concentrations of 1 nM to 400 nM of TSA. MTT assay and trypan blue exclusion assays were performed to estimate
cell growth and cell viability, and cell cycle analysis was evaluated. TSA treatment showed a reduction in numbers of viable
cells and an increase of cell death by apoptosis. The cell cycle analysis showed an increase of hypodiploid cells and a reduction
of G0/G1 and G2/M –phases. According to these results, trichostatin A may be an interesting potential chemotherapeutic agent
for the treatment of canine MCT. 相似文献
99.
Characterization of Doayo and Kapsiki taurine cattle breeds of Cameroon in their natural environment
Data were collected on live weight (LW), heart girth (HG), height-at-withers (HW), trunk length (TL), age, sex, and coat color
of 207 taurines cattle—122 of the Doayo (Namchi) breed and 85 of the Kapsiki (Kirdi) breed. The animals, aged 1 to 20 years,
were selected from 60 herds randomly selected from villages of Poli of Faro and Mokolo of Tsanga, divisions of the North and
Far North Regions of Cameroon. The data were analyzed using the SAS program with a linear model, applying standard tests.
Results indicated no breed effect (P > 0.05) in the growth trends of LW, HG, HW, and TL. HG and TL were highly significantly (P < 0.0001) related to LW. The growth pattern for the two breeds was the same since the linear contrast of least square means
for the traits at various age groups did not differ (P > 0.05) significantly. The breeds attained maturity as from 4 years. In the absence of breed effect (P > 0.05), a single regression equation was established for the estimation of live weight as thus LW = - 244.42 ( ±22.57 ) kg + 2.49 ( ±0.23 ) HG + 1.04 ( ±0.25 ) TL {\hbox{LW}} = - {244}.{42 }\left( {\pm {22}.{57}} \right){\hbox{ kg}} + {2}.{49 }\left( {\pm 0.{23}} \right){\hbox{ HG}} + {1}.0{4 }\left( {\pm 0.{25}} \right){\hbox{ TL}} , with HG contributing up to 70% of total variation and TL, 2%. This equation could be used to develop a measuring band useful
in the rural environment for commercial and clinical veterinary purposes. 相似文献
100.
The consumption of solid feed is essential for successful transition from a pre-ruminant to a functional digestive tract. Lambs fed starter rations containing highly fermentable carbohydrates often experience dramatic changes in concentrations of rumen and blood metabolites. The optimal amount of roughage required in the diet of pre-ruminant animals is still unclear. The objective of this study was to determine the effect of feeding alfalfa hay on performance and rumen development in young Balouchi lambs. In a completely randomized design, 30 lambs were fed one of three experimental diets consisting of a control, without alfalfa hay (C), a diet containing 7.5% alfalfa hay (A1), and a diet containing 15% alfalfa hay (A2). Lambs fed A1 and A2 diets had lower dry matter intake during the pre-weaning period (P?0.01) and overall (P?=?0.02), but feed conversion ratio and average daily gain were not affected by feeding alfalfa hay. Concentration of beta-hydroxybutyric acid was higher in C compared with the A1 and A2 groups (P?0.01). Concentrations of glucose and non-esterified fatty acids did not differ among the groups of animals. Feeding alfalfa hay reduced thickness of the rumen epithelial keratinized layer (P?=?0.04) and increased thickness of muscular layer (P?=?0.05). We concluded that including 15% alfalfa hay in the starter diet could reduce thickness of the keratinization layer and increase muscularity of rumen wall without adverse effects on growth and performance of newborn lambs. 相似文献