全文获取类型
收费全文 | 1220篇 |
免费 | 45篇 |
国内免费 | 27篇 |
出版年
2023年 | 8篇 |
2022年 | 7篇 |
2021年 | 15篇 |
2020年 | 20篇 |
2019年 | 12篇 |
2018年 | 21篇 |
2017年 | 10篇 |
2016年 | 9篇 |
2015年 | 18篇 |
2014年 | 19篇 |
2013年 | 53篇 |
2012年 | 19篇 |
2011年 | 18篇 |
2010年 | 14篇 |
2009年 | 30篇 |
2008年 | 27篇 |
2007年 | 33篇 |
2006年 | 37篇 |
2005年 | 43篇 |
2004年 | 51篇 |
2003年 | 55篇 |
2002年 | 47篇 |
2001年 | 46篇 |
2000年 | 37篇 |
1999年 | 32篇 |
1998年 | 33篇 |
1997年 | 45篇 |
1996年 | 41篇 |
1995年 | 32篇 |
1994年 | 44篇 |
1993年 | 53篇 |
1992年 | 42篇 |
1991年 | 35篇 |
1990年 | 21篇 |
1989年 | 19篇 |
1988年 | 35篇 |
1987年 | 28篇 |
1986年 | 23篇 |
1985年 | 20篇 |
1984年 | 14篇 |
1983年 | 11篇 |
1982年 | 17篇 |
1981年 | 17篇 |
1980年 | 12篇 |
1978年 | 8篇 |
1977年 | 10篇 |
1976年 | 11篇 |
1975年 | 9篇 |
1974年 | 10篇 |
1973年 | 13篇 |
排序方式: 共有1292条查询结果,搜索用时 15 毫秒
1.
2.
Kristian Aspegren Leena Mannonen Anneli Ritala Riitta Puupponen-Pimiä Ulrika Kurtén Marjatta Salmenkallio-Marttila Veli Kauppinen Teemu H. Teeri 《Molecular breeding : new strategies in plant improvement》1995,1(1):91-99
Transgenic plant cell cultures have a potential for production and secretion of important proteins and peptides. To assess the possibilities of using a stable barley suspension culture for secretion of heterologous proteins in active form, we expressed the cDNA of the thermostable-glucanase (EGI) ofTrichoderma reesei in barley suspension cells. The cDNA coding for EGI and its signal sequence was placed under the control of the CaMV 35S promoter and the construction was transferred to the cells by particle bombardment. Stably transformed lines were obtained by selecting for a cotransformed antibiotic resistance marker. The expression of EGI cDNA led to accumulation of EGI in the culture medium, as shown by analysis with EGI-specific antibodies. Enzymatic assays confirmed that the EGI secreted by the suspension cells retained its activity and thermostable character. Furthermore, it was shown that the enzyme produced by the transgenic suspension culture could be used for degradation of soluble-glucans during mashing. 相似文献
3.
A consensus linkage map of barley 总被引:5,自引:0,他引:5
Peter Langridge Angelo Karakousis Nick Collins Jodie Kretschmer Sue Manning 《Molecular breeding : new strategies in plant improvement》1995,1(4):389-395
A consensus linkage map of the barley genome was constructed. The map is based on six doubled haploid and one F2 population. The mapping data for three of the doubled haploid populations was obtained via the GrainGenes database. To allow merger of the maps, only RFLP markers that produce a single scorable band were included. Although this reduced the available markers by about half, the resultant map contains a total of 587 markers including 87 of known function. As expected, gene order was highly conserved between maps and all but two discrepancies were found in closely linked markers and are likely to result from the small population sizes used for some maps. The consensus map allows the rapid localisation of markers between published maps and should facilitate the selection of markers for high-density mapping in defined regions. 相似文献
4.
Simulation of field scale denitrification losses from soils under grass ley and barley 总被引:2,自引:0,他引:2
Denitrification losses from soils under barley and grass ley crops were simulated. The model, which includes the major processes determining inputs, transformations and outputs of nitrogen in arable soils, represents a scale compatible with information generally available in agricultural field research. The denitrification part of the model includes a field potential denitrification rate and functions for the effect of soil aeration status, soil temperature and soil nitrate content. Easily metabolizable organic matter is assumed not to limit denitrification. Simulated values were compared with denitrification measurements made during two growing seasons in the barley and grass ley treatments of a field experiment in central Sweden.Calibration revealed that the optimal parameter values describing the effect of soil aeration on denitrification rates were similar for both treatments. The response function derived agreed well with two data sets found in the literature. The potential denitrification rate constant, derived in the simulations, was higher for grass ley than for barley, which was consistent with the differences in overall rates of carbon and nitrogen turnover found between treatments.The simulated mean denitrification rates for the two seasons were within 20% of the mean of the measured values. However, simulated denitrification showed less temporal variability and a less skewed frequency distribution than measured denitrification. Some of the measured denitrification events not explained by the model could have been due to the stimulating effects of soil drying/wetting and freezing/thawing on microbial activity. 相似文献
5.
半矮秆基因brh1在大麦中的精细定位 总被引:1,自引:1,他引:0
选用从大麦、小麦和水稻中分离的RFLP标记 ,构建了大麦半矮秆基因brh1精细图谱。以快中子处理六棱大麦品种Steptoe的种子 ,从M2 代中选择出brh1突变体FN5 3。brh1是一个极易鉴别的形态学标记 ,通过对FN5 3×Morex的F2 代群体进行鉴定表明 ,brh1基因为隐性 ,前人通过BSA法将其初步定位在大麦第 1染色体 (7H)短臂上 ,靠近端粒区。这一区间还有一个控制秆锈病抗性的显性基因Rpg1。所以 ,brh1的精细定位不仅对研究其本身具有重要意义 ,同时 ,也为Rpg1的图位克隆和功能研究提供了更大的重组配子群体。定位实验全部以F2 中具有brh1特征的个体为对象完成 ,鉴定工作在苗期进行。在该精细图上 ,brh1区间长15 .2cM ,各标记间的平均距离为 0 .8cM。其中 ,大麦的cDNA克隆MWG2 0 74B与brh1共分离。 2 0 74A在靠近着丝点一侧 ,与brh1相距 0 .8cM。BCD12 9和R3139在定位群体内呈现与MWG2 0 74A共分离。CDO5 4 5位于端粒一侧 ,距离brh1为 0 .8cM。根据禾谷类作物基因组的共线性原理 ,CDO5 4 5成功定位在水稻的同源染色体即第 6染色体短臂brh1区间内。然而 ,由于在定位亲本间缺乏多态性 ,BCD12 9和MWG2 0 74的 2条主带A和B均未能定位在水稻的共线性区段内。推测MWG2 0 74的其他各带可能被定位在水稻的目标区间内 ,从而有 相似文献
6.
Removal of emulsified food and mineral oils from wastewater using surfactant modified barley straw 总被引:3,自引:0,他引:3
Barley straw, an agricultural waste, was chemically modified and evaluated for the removal of emulsified oils from aqueous solution. The chemical modification was performed using NaOH and a cationic surfactant, hexadecylpyridinium chloride monohydrate (CPC). The surface textural and chemical properties of the surfactant modified barley straw (BMBS) were characterized by N2 adsorption, FT-IR, SEM and water soluble mineral content. The adsorption tests were carried out in batch adsorption system for removal of standard mineral oil (SMO) and canola oil (CO) from water. For both emulsified oils in wastewater, adsorption was found to be strongly related with solution pH. The isotherm study indicated that emulsified oil adsorption on BMBS could be fitted well with the Langmuir model other than Freundlich model. The maximum adsorption capacity for CO and SMO at 25 °C determined from the Langmuir isotherm is 613.3 and 584.2 mg g−1, respectively. Desorption tests in water solution show that oil is strongly bonded with adsorbent and desorption is only about 1–2% in 24 h. 相似文献
7.
The severity of a root rot disease of cereals, caused by Rhizoctonia solani Kühn AG8, was inversely correlated to the Zn status of plants in field studies in 1989 and 1990. In 1989, a preliminary survey was conducted in a farmer's field in South Australia where Zn deficiency and disease were both widespread. Zn concentration in Spear wheat plants at the 3-leaf to early tillering stage was negatively correlated with severity of the disease. For the elevent elements analysed, a correlation matrix showed that Zn had the highest, and only significant (R2=0.52**) association with disease. The effect of Zn applications and their residual value on disease severity was further studied in a long-term field experiment in 1989 and 1990 to which Zn had been applied in 1986. There was a decrease in the area of Rhizoctonia bare patch as Zn rate was increased, a result consistent with the field survey results; the recommended rate of 2.5 kg Zn ha–1 reduced the area affected by bare patch from 42% to 21% of the total crop area compared with no Zn application, overcame Zn deficiency and increased grain yield from 1.1 to 2.8 t ha–1. In 1990, fresh Zn application treatments were applied to trial plots designed for this purpose, in order to compare the response with the older Zn treatments applied in 1986. The areas of bare patch in the older Zn treatments were approximately 5% greater than those in the fresh Zn treatments. The results are consistent with the hypothesis that Zn deficient plants are more susceptible to root rot caused by R. solani. Testing this hypothesis is the subject of a companion paper. 相似文献
8.
Seasonal leaf water relations characteristics were studied in fully irrigated spring barley (Hordeum distichum L. cv. Gunnar) fertilized at low (50 kg K ha−1) or high (200 kg K ha−1) levels of potassium applied as KCl. The investigation was undertaken from about 14 days before anthesis until the milk ripe
stage in leaves of different position and age. Additionally, the effects of severe water stress on leaf water relations were
studied in the middle of the grain filling period in spring barley (cv. Alis). The leaf water relations characteristics were
determined by the pressure volume (PV) technique.
Water relations of fully irrigated plants were compared in leaf No 7 with the water relations of slowly droughted plants (cv.
Alis). Leaf osmotic potential at full turgor (ψ
π
100
) decreased 0.1 to 0.3 MPa in droughted leaves indicating a limited osmotic adjustment due to solute accumulation. The leaf
osmotic potential at zero turgor (ψ
π
0
) was about −2.2 MPa in fully irrigated plants and −2.6 MPa in droughted plants. The relative water content at zero turgor
(R0) decreased 0.1 unit in severely droughted leaves. The ratio of turgid leaf weight to dry weight (TW/DW) tended to be increased
by drought. The tissue modulus of elasticity (ε) decreased in droughted plants and together with osmotic adjustment mediated
turgor maintenance during drought. A similar response to drought was found in low and high K plants except that the R0 and ε values tended to be higher in the high K plants. Conclusively, during drought limited osmotic adjustment and increase
in elasticity of the leaf tissue mediated turgor maintenance. These effects were only slightly modified by high potassium
application.
The seasonal analysis in fully irrigated plants (cv. Gunnar) showed that within about 14 days from leaf emergence ψ
π
100
decreased from about −0.9 to −1.6 MPa in leaf No 7 (counting the first leaf to emerge as number one) and from about −1.1
to −1.9 MPa in leaf No 8 (the flag leaf) due to solute accumulation. A similar decrease took place in ψ
π
0
except that the level of ψ
π
0
was displaced to a lower level of about 0.2 to 0.3 MPa. Both ψ
π
100
and ψ
π
0
tended to be 0.05 to 0.10 MPa lower in high K than in low K plants. R0 was about 0.8 to 0.9 and was independent of leaf position and age, but tended to be highest in high K plants. The TW/DW ratio
decreased from about 5.5 in leaf No 6 to 4.5 in leaf No 7 and 3.8 in leaf No 8. The TW/DW ratio was 4 to 10% higher in high
K than in low K plants indicating larger leaf cell size in the former. The apoplastic water content (Va) at full turgor constituted about 15% in leaf No 7. ε was maximum at full turgor and varied from about 11 to 34 MPa. ε tended
to be higher in high K plants. Conclusively, in fully watered plants an ontogenetically determined accumulation of solutes
(probably organic as discussed) occurred in the leaves independent of K application. The main effect of high K application
on water relations was an increase in leaf water content and a slight decrease in leaf ψπ.
The effect of K status on growth and drought resistance is discussed. 相似文献
9.
Sarah L. Roberts-Oehlschlager James M. Dunwell 《Plant Cell, Tissue and Organ Culture》1990,20(3):235-240
A period of four days preincubation at 25 °C on a medium containing mannitol was found to be superior to those pretreatments requiring incubation at 4 °C. In addition, the yield of green plants was improved by orienting anthers flat on the medium during mannitol preincubation, and reducing the number of anthers cultured per dish. 相似文献
10.
Below-ground carbon distribution in barley (Hordeum vulgare L.) with and without nitrogen fertilization 总被引:5,自引:0,他引:5
Gerd Johansson 《Plant and Soil》1992,144(1):93-99
The distribution of net assimilated C in barley (Hordeum vulgare L.) grown at two N-levels was determined in a growth chamber. The N-fertilization involved 0 and 3.61 mol N g-1 dry soil. After growth for seven weeks in an atmosphere with continuously 14C-labelled CO2, 14C was determined in shoots, roots, rhizosphere respiration and soil. At the low N-level, 32% of the net assimilated 14C was translocated below ground, whereas at the high N-level 27% was translocated below ground. The release of C from roots (root respiration, microbial respiration originating from decomposition of 14C-labelled root material and 14C remaining in soil) was greater with no N-supply (19% of net assimilated 14C) than in the treatment with N-supply (15%). Thus, the effect of N-supply on both translocation of assimilated 14C below ground and the release of 14C from growing roots was relatively small. 相似文献