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   4566篇
  免费   233篇
  国内免费   2篇
林业   199篇
农学   233篇
基础科学   13篇
  815篇
综合类   358篇
农作物   694篇
水产渔业   401篇
畜牧兽医   1779篇
园艺   69篇
植物保护   240篇
  2023年   29篇
  2022年   88篇
  2021年   163篇
  2020年   97篇
  2019年   121篇
  2018年   144篇
  2017年   134篇
  2016年   146篇
  2015年   150篇
  2014年   205篇
  2013年   269篇
  2012年   328篇
  2011年   383篇
  2010年   220篇
  2009年   199篇
  2008年   292篇
  2007年   296篇
  2006年   263篇
  2005年   218篇
  2004年   214篇
  2003年   186篇
  2002年   140篇
  2001年   131篇
  2000年   92篇
  1999年   57篇
  1998年   28篇
  1997年   17篇
  1996年   9篇
  1995年   9篇
  1994年   3篇
  1993年   8篇
  1992年   16篇
  1991年   14篇
  1990年   22篇
  1989年   17篇
  1988年   7篇
  1987年   9篇
  1986年   7篇
  1985年   5篇
  1984年   4篇
  1983年   5篇
  1980年   5篇
  1978年   11篇
  1975年   3篇
  1974年   5篇
  1972年   5篇
  1971年   3篇
  1970年   3篇
  1969年   3篇
  1968年   4篇
排序方式: 共有4801条查询结果,搜索用时 0 毫秒
11.
UVB radiation proves to be one of the most relevant environmental risks because of its hazardous effects, such as premature skin aging and especially skin photocarcinogenesis. Anthocyanins, water-soluble pigments present in plants, are known to be powerful antioxidants that help protect plants from UV damage. In this study, we aimed at investigating the protective effect of anthocyanins from black soybean [Glycine max (L.) Merr] seed coats on UVB-induced apoptosis, and furthermore, we investigated the molecular mechanism responsible for regulation of apoptosis in vitro and in vivo. Pretreatment with anthocyanins reduced UVB-induced reactive oxygen species levels and inhibited UVB-induced apoptotic cell death through the prevention of caspase-3 pathway activation and reduction of proapoptotic Bax protein levels. UVB irradiation induced apoptotic cell death, which was inhibited by topical application of anthocyanins in hairless mice. It is concluded that anthocyanins from the seed coat of black soybeans may be useful compounds to modulate UVB-induced photoaging.  相似文献   
12.
Patch and skin bioassays were used in laboratory and indoor tests to evaluate the repellency of (E)-cinnamaldehyde, identified in Cinnamomum cassia Blume bark and essential oil, and a cream containing 5% (w/w) cassia oil against Aedes aegypti (L.) females. Results were compared with those of a known C. cassia compound cinnamyl alcohol, N,N-diethyl-m-toluamide (DEET) and two commercial repellents: MeiMei cream containing citronella and geranium oils and Repellan S aerosol containing 19% DEET. In patch bioassay tests with A. aegypti females, (E)-cinnamaldehyde at 0.153 mg cm(-2) and DEET at 0.051 mg cm(-2) provided 93 and 89% protection at 40 min after exposure. In skin bioassay tests, (E)-cinnamaldehyde at 0.051 mg cm(-2) and DEET at 0.025 mg cm(-2) provided 87 and 95% protection at 30 min after application. (E)-Cinnamaldehyde was significantly more effective than cinnamyl alcohol in both bioassays. In indoor tests with four human volunteers, 5% cassia oil cream provided 94, 83 and 61% protection against A. aegypti females exposed for 30, 50 and 70 min after application respectively. Cassia oil cream was a slightly less effective repellent than MeiMei cream. Repellan S aerosol provided 91% repellency at 120 min after application. Products containing cassia oil merit further study as potential repellents for the protection of humans and domestic animals from blood-feeding vectors and the diseases they transmit.  相似文献   
13.
We investigated the effects of hepatic and renal impairment on the pharmacokinetics of enrofloxacin in Sprague-Dawley rats. Experimental hepatic and renal failure were induced by carbon tetrachloride (CCL4) and 5/6 nephrectomy, respectively. After intravenous dosing of enrofloxacin (10 mg/kg), plasma concentrations of enrofloxacin were measured using liquid chromatograph/mass spectrometry. There was no significant effect of hepatic impairment on enrofloxacin pharmacokinetics. However, renal impairment markedly prolonged elimination half life (t1/2λz) of enrofloxacin (P < 0.05), comparing with respective control. Total body clearance (Clb) and volume of distribution at steady state (Vss) were significantly decreased (P < 0.05) by renal impairment. In conclusion, these results suggested that renal impairment could affect the pharmacokinetics of enrofloxacin.  相似文献   
14.
Aspergillus spp. are opportunistic pathogens which cause pulmonary aspergillosis in animals and humans with compromised immune systems. Two Eurasian black vultures (Aegypius monachus Linnaeus) were found dead or clinically ill from carbofuran insecticide during the winter of 2004. Carbofuran was detected in the stomach contents by gas chromatograph-mass spectrometry. Gross lesions showed severe granulomatous pneumonia and serofibrinous pleuropneumonia in both birds, with most lesions restricted to the pulmonary system. Histological lesions included pyogranulomatous pneumonia and suppurative parabronchiolitis/pleuritis/air sacculitis with a number of septated fungal hyphae, suggesting severe pulmonary aspergillosis. Fungal isolates from each vulture were identified as Aspergillus fumigatus by both lactophenol cotton blue staining and genetic analysis. This is the first report of pulmonary aspergillosis caused by A. fumigatus in wild Eurasian black vultures and suggests that Aspergillus infection could be an important cause of death in these birds which migrate from Mongolia to Korea during the winter. The incidence of the disease may be related to impaired immunity caused directly or indirectly by carbofuran poisoning.  相似文献   
15.
16.
This study was performed to evaluate the effect of beta-tricalcium phosphate and poly L-lactide-co-glycolide-co-epsilon-caprolactone (TCP/PLGC) membrane in the repair of partial bone defects in canine proximal humerus. Three adult mixed-breed dogs were used during the experimental period. The length of the defect was quarter of the full length of humerus, and width of the defect was quarter of middle diameter of the lateral aspect of humerus. The humeri of each dog were divided into treatment (TCP/PLGC) and control groups. The defect was covered with TCP/PLGC membrane in treatment group. To evaluate regeneration of the bone, computerized tomography (CT) and histopathologic examination were performed. The radiopaque lines were appeared at the original defect sites in TCP/PLGC group but below the original site in control at 4th week. Radiopacity and thickness of the defect sites, and radiopaque lines were more increased at 8th week than those of 4th week. Histopathologic findings revealed fibrous connective tissue migration into the defect and the migration inhibited the structure of new cortex to be placed in the original level in control whereas new cortex growth was found in the level of original line in TCP/PLGC group. However, the new cortical bone in the TCP/PLGC group was thinner and less organized than the adjacent intact cortex, and the amount of new cancellous bones were also scanty. The result suggested that TCP/PLGC membrane is a good guided bone regeneration material to restore the original morphology of humerus in partial defect.  相似文献   
17.
In this study, we characterized the secreted proteins of Brucella abortus into the enriched media under the bacterial laboratory growth condition and investigated the pathogenic importance of culture supernatant (CS) proteins to B. abortus infection. CS proteins from stationary phase were concentrated and analyzed using 2D electrophoresis. In MALDI TOF/TOF analysis, more than 27 proteins including CuZn SOD, Dps, Tat, OMPs, Adh, LivF, Tuf, SucC, GroEL and DnaK were identified. Cytotoxic effects of CS proteins were found to increase in a dose-dependent manner in RAW 264.7 cells. Upon B. abortus challenge into phagocytes, however, CS proteins pre-treated cells exhibited lower bacterial uptake and intracellular replication compared to untreated cells. Immunization with CS proteins induced a strong humoral and cell mediated immune responses and exhibited significant higher degree of protection against virulence of B. abortus infection compared to mice immunized with Brucella broth protein (BBP). Taken together, these results indicate that B. abortus secreted a number of soluble immunogenic proteins under laboratory culture condition, which can promote antibody production resulted in enhancing host defense against to subsequently bacterial infection. Moreover, further analysis of CS proteins may help to understand the pathogenic mechanism of B. abortus infection and host–pathogen interaction.  相似文献   
18.
The Brucella mdh gene was successfully cloned and expressed in E. coli. The purified recombinant malate dehydrogenase protein (rMDH) was reactive to Brucella-positive bovine serum in the early stage, but not reactive in the middle or late stage, and was reactive to Brucella-positive mouse serum in the late stage, but not in the early or middle stage of infection. In addition, rMDH did not react with Brucella-negative bovine or mouse sera. These results suggest that rMDH has the potential for use as a specific antigen in serological diagnosis for early detection of bovine brucellosis.  相似文献   
19.
Intradermal tests were performed on 58 dogs diagnosed with atopic dermatitis from 2004~2008 at the Veterinary Medical Teaching Hospital of Konkuk University, Korea. To compare the allergen distribution observed in the present investigation to the results from other studies conducted in Korea and elsewhere, the allergens were grouped according to their kinds. There was no significant difference in gender distribution among the dogs. The most common breeds among the 58 dogs were Maltese (n = 11) and Shih-tzu (n = 11). The average age was 4.8 years. The most frequently produced a positive reaction on the intradermal tests was mold (67.3%) followed by house dust (54.5%) and house dust mites (49.1%). The present study found a low distribution of dogs allergic to various outdoor allergens compared to studies performed in other countries; this may reflect differences in living conditions for dogs living in Korea.  相似文献   
20.
Five coronaviruses (CoVs) were detected in diarrheal feces from four zoo ruminant species: one wisent (Bison bonasus), two Himalayan tahr (Hemitragus jemlahicus), one sitatunga (Tragelaphus spekii), and one nyala (Tragelaphus angasii). We sequenced and analyzed the spike (S) and hemagglutinin/esterase (HE) genes of these viruses and compared the nucleotide (nt) and deduced amino acid (aa) sequences with those of other bovine CoV (BcoV) strains. Comparison of the entire deduced aa sequences of the S and HE glycoproteins revealed no specific differences that would account for discrimination between bovine-like CoV strains from zoo ruminants and BcoVs strains. In addition, the 99.9% aa identity among the five CoV strains revealed that the ruminants were infected by the same strain. Phylogenetically, bovine-like CoVs belong to group 2a CoVs, which are related most closely to the BcoV strains recently isolated in Korea. These data suggest that cattle are potential reservoirs for CoVs that are capable of infecting zoo ruminants.  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