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   289篇
  免费   22篇
  国内免费   1篇
  2023年   7篇
  2022年   7篇
  2021年   3篇
  2020年   10篇
  2019年   12篇
  2018年   7篇
  2017年   8篇
  2016年   11篇
  2015年   15篇
  2014年   21篇
  2013年   28篇
  2012年   26篇
  2011年   20篇
  2010年   11篇
  2009年   10篇
  2008年   13篇
  2007年   6篇
  2006年   10篇
  2005年   5篇
  2004年   7篇
  2003年   10篇
  2002年   3篇
  2001年   8篇
  2000年   4篇
  1999年   1篇
  1998年   3篇
  1997年   1篇
  1996年   4篇
  1995年   1篇
  1994年   2篇
  1993年   5篇
  1992年   3篇
  1990年   1篇
  1989年   2篇
  1988年   3篇
  1987年   2篇
  1986年   2篇
  1984年   2篇
  1982年   2篇
  1981年   2篇
  1980年   4篇
  1979年   1篇
  1978年   3篇
  1977年   1篇
  1976年   3篇
  1975年   1篇
  1973年   1篇
排序方式: 共有312条查询结果,搜索用时 15 毫秒
1.

Introduction  

The Work Productivity and Activity Impairment (WPAI) questionnaire is a well validated instrument to measure impairments in work and activities. However, its validation among patients with rheumatoid arthritis (RA) has not been well established. The present study's purpose is to evaluate the construct validity of the WPAI-general health version among RA patients and its ability to differentiate between RA patients with varying health status.  相似文献   
2.
Raza  Shahbaz  Mohsin  Mashkoor  Madni  Waqas Ahmed  Sarwar  Fatima  Saqib  Muhammad  Aslam  Bilal 《EcoHealth》2017,14(1):182-186
EcoHealth - We investigated wild migratory birds faecal swabs for extended-spectrum β-lactamases-producing Klebsiella pneumoniae (ESBL-K. pneumoniae) from wetland habitats in Pakistan. ESBL-K....  相似文献   
3.
4.
Astract  The mycotoxin ochratoxin A (OTA) is a public health issue in many countries. Data on OTA concentrations in foods and in blood are available for several European countries including the Balkan area, as well as for Canada and Japan. Yet, for developing countries such data are scarce. In this study we determined OTA blood levels as biomarker of exposure in bladder cancer patients and in healthy controls from Pakistan. OTA in blood was analyzed after extraction by HPLC with fluorescence detection (limit of detection: <0.03 ng/mL) in 96 patients and in 31 controls. Over 92% of all blood samples (87 patients, 30 controls) contained quantifiable amounts of OTA: The mean OTA concentrations were 0.33 ng/mL (SD 0.42; range: 0.03 to 3.41 ng/mL) in bladder cancer patients, and 0.31 ng/mL (SD 0.29; range: 0.04 to 1.25 ng/mL) in healthy controls. These OTA concentrations are comparable to those reported for the general population in the European Union. Presented at the 27th Mykotoxin-Workshop, Dortmund Germany, done 13–15, 2005. The IfADo is accredited as WHO Cellaporating Center for Occupational Health.  相似文献   
5.
This study was carried out to see the impact of Angoumois grain moth (AGM) on different cultivars of barley so that we must grow resistant variety of barley or improve those which are susceptible to it. Eggs of Sitotroga cerealella (Oliv.) were collected and reared in incubators available in Stored Product Entomology Laboratory, Pir Mehr Ali Shah Arid Agriculture University Rawalpindi, under temperature 27 ± 2°C and 60 ± 2% relative humidity. For the experiment, five different cultivars of barley; Sanober-96, Jau-83, Soorab-96, ICBA and Sterling were selected for AGM feed. After an interval of 30, 60 and 90 days of infestation, percentage damage and weight loss in grains were determined. After carrying out laboratory and field germination tests, viability of different cultivars were checked. Damage was maximum in variety Soorab (99.38%), which becomes susceptible while it was minimum in Sanober-96 (90.62%), which becomes resistant. Weight loss was maximum in variety Soorab (49.71%), which becomes susceptible and was minimum in Sanober-96 (45.32%), which becomes resistant. Damage was positively correlated with weight loss and negatively correlated with seed germination. In germination tests, on filter paper, maximum germination was found in variety Sterling (3%) which becomes resistant and it was minimum in ICBA which becomes susceptible (0%). In sand germination test, maximum seeds germinated in variety Sanober-96 (2%), and minimum seeds germinated in ICBA (0%). By calculating the percentage of losses of different cultivars, it was found that none of cultivars proved itself completely resistant or susceptible.  相似文献   
6.
The economic loss due to pest attack in stored commodities is a serious problem worldwide. About 200 insect species attack stored commodities. These insect pests are responsible for quantitative and qualitative losses in cereal grains. Among the stored grain pests, Angoumois grain moth, Sitotroga cerealella is considered as common, top of the list and most destructive pest of cereal grains. Its infestation starts in the standing crop and continues in storage. Although there are many control strategies, our need is some effective, cheap and readily available strategy for safe storage. This review presents different ways by which S. cerealella can be controlled. In this paper, a list of approaches is given which are used to improve the protection of stored grains against S. cerealella attack. These approaches include use of edible oils, containers, synthetic chemicals, agricultural waste materials, plant derivatives, bacterial protoxins, biopesticides, biocontrol enhancers and semiochemicals. If these tactics are followed as combined strategies in a compatible manner, they can provide us an integrated pest management programme for the efficient control of S. cerealella in cereal grains.  相似文献   
7.
The effects of predicted climate change on aphid–natural enemy interactions have principally considered the effects of elevated carbon dioxide concentration and air temperature. However, increased incidence of summer droughts are also predicted in Northern Europe, which could affect aphid–plant interactions and aphid antagonists. We investigated how simulated summer drought affected the bird cherry–oat aphid, Rhopalosiphum padi L., and its natural enemy the parasitoid wasp Aphidius ervi. Drought and, to a greater extent, aphids reduced barley ( Hordeum vulgare) dry mass by 33% and 39%, respectively. Drought reduced leaf and root nitrogen concentrations by 13% and 28%, respectively, but foliar amino acid concentrations and composition remained similar. Aphid numbers were unaffected by drought, but population demography changed significantly; adults constituted 41% of the population on drought‐treated plants, but only 26% on those receiving ambient irrigation. Nymphs constituted 56% and 69% of the population on these plants, respectively, suggesting altered aphid development rates on drought‐stressed plants. Parasitism rates were significantly lower on drought‐stressed plants (9 attacks h?1 compared with 35 attacks h?1 on ambient‐irrigated plants), most likely because of lower incidence of nymphs and more adults, the latter being more difficult to parasitize. Any physiological changes in individual aphids did not affect parasitoid preferences, suggesting that attacks were postponed because of drought‐induced changes in aphid demography. This study demonstrates the potential for sporadic climate change events, such as summer drought, to be disruptive to herbivore–antagonist interactions.  相似文献   
8.
A protocol has been developed for in vitro plant regeneration from a nodal explant of Dracaena sanderiana Sander ex Mast. Nodal explant showed high callus induction potentiality on MS medium supplemented with 6.78 μM 2,4-dichlorophenoxyacetic acid (2,4-D) followed by 46.5 μM chlorophenoxy acetic acid (CPA). The highest frequency of shoot regeneration (85%) and number of shoots per explant (5.6) were obtained on medium supplemented with 7.84 μM N6-benzylaminopurine (BA). Rooting was high on MS solid compared to liquid medium when added with 7.38 μM indole-3-butyric acid (IBA). Fifty percent of the roots were also directly rooted as microcuttings on soil rite, sand and peat mixture (1:1:1). In vitro and ex vitro raised plantlets were used for acclimatization. More than 90% of the plantlets was successfully acclimatized and established in plastic pots. Ex vitro transferred plantlets were normal without any phenotypic aberrations.  相似文献   
9.
Abstract

Biosynthesis of metal nanoparticles is an area of interest among researchers because of its eco-friendly approach. Current study focuses at biosynthesis of silver nanoparticles (AgNPs) and optimization of physico-chemical conditions to obtain mono-dispersed and stable AgNPs having antimicrobial activity. Initially Bacillus mojavensis BTCB15 produced silver nanoparticles (AgNPs) of 105?nm. Silver nanoparticles (AgNPs) were characterized by particle size analyzer, UV-Vis Spectroscopy, Fourier transforms infrared spectroscopy (FTIR), Atomic force microscopy (AFM), and X-ray diffraction (XRD). Whereas, under optimal conditions of temperature 55?°C, pH 8, addition of surfactant Tween 20, and metal ion K2SO4, about 104% size reduction was achieved with average size of 2.3nm. Molecular characterization revealed 98% sequence homology with Bacillus mojavensis. AgNPs exhibited antibacterial activity at concentrations ranging from 0.5 to 2.5?µg/µl against Escherichia coli BTCB03, Klebsiella pneumonia BTCB04, Acinetobacter sp. BTCB05, and Pseudomonas aeruginosa BTCB01 but none against Staphylococcus aureus BTCB02. Highest antibacterial activity was observed at 0.27?µg/µl and lowest at 0.05?µg/µl of AgNPs indicated by zone of inhibition. Conclusively, under optimum conditions, Bacillus mojavensis BTCB15 was able to produce AgNPs of 2.3?nm size and had antibacterial activity against multi drug resistant pathogens.  相似文献   
10.
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