全文获取类型
收费全文 | 28012篇 |
免费 | 2158篇 |
国内免费 | 2073篇 |
专业分类
林业 | 3556篇 |
农学 | 1940篇 |
基础科学 | 552篇 |
2465篇 | |
综合类 | 10273篇 |
农作物 | 1229篇 |
水产渔业 | 4508篇 |
畜牧兽医 | 5036篇 |
园艺 | 1411篇 |
植物保护 | 1273篇 |
出版年
2024年 | 129篇 |
2023年 | 417篇 |
2022年 | 839篇 |
2021年 | 1010篇 |
2020年 | 1088篇 |
2019年 | 1441篇 |
2018年 | 889篇 |
2017年 | 1525篇 |
2016年 | 1566篇 |
2015年 | 1292篇 |
2014年 | 1558篇 |
2013年 | 1924篇 |
2012年 | 2276篇 |
2011年 | 2100篇 |
2010年 | 1729篇 |
2009年 | 1567篇 |
2008年 | 1390篇 |
2007年 | 1505篇 |
2006年 | 1228篇 |
2005年 | 942篇 |
2004年 | 768篇 |
2003年 | 688篇 |
2002年 | 582篇 |
2001年 | 552篇 |
2000年 | 458篇 |
1999年 | 409篇 |
1998年 | 300篇 |
1997年 | 301篇 |
1996年 | 271篇 |
1995年 | 272篇 |
1994年 | 228篇 |
1993年 | 198篇 |
1992年 | 153篇 |
1991年 | 145篇 |
1990年 | 136篇 |
1989年 | 107篇 |
1988年 | 77篇 |
1987年 | 57篇 |
1986年 | 30篇 |
1985年 | 24篇 |
1984年 | 11篇 |
1983年 | 4篇 |
1982年 | 9篇 |
1981年 | 8篇 |
1980年 | 8篇 |
1979年 | 8篇 |
1978年 | 5篇 |
1977年 | 5篇 |
1976年 | 5篇 |
1956年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 312 毫秒
91.
P. van de Graaf † M. E. Joseph J. M. Chartier-Hollis T. M. O'Neill 《Plant pathology》2002,51(3):331-337
A detailed study of conidial germination, germ-tube growth and the formation of infection structures in Phoma clematidina , the causal agent of clematis wilt, is described for two clematis varieties differing in disease resistance. On both the resistant and susceptible varieties, the fungus entered leaves and stems by direct penetration of the cuticle, often, but not always, following the formation of infection structures. More germ tubes per conidium were formed on the susceptible host, but these germ tubes were on average shorter than on the resistant host. Although germ tubes regularly entered the plant via trichomes, stomata were not found to be sites of entry. Following penetration of the cuticle of resistant plants, germ-tube growth was sometimes restricted to the subcuticular region, and halo formation occurred at the sites where penetration was attempted. Subcuticular growth and halo formation were not observed on susceptible plants. These observations may partly explain the resistance of small-flowered clematis varieties to P. clematidina . 相似文献
92.
20%多效唑·甲哌 FEE7 微乳剂防止小麦倒伏和增产机理研究 总被引:1,自引:0,他引:1
冬小麦二棱期喷施植物生长调节剂20%多效唑·甲哌鎓微乳剂375 mL/hm2,可以显著抑制茎秆基部节间伸长,增加各节间充实度,其中赤霉素(Gas)和生长素(IAA)降低,可显著增强小麦抗倒伏能力和降低田间倒伏率.处理还协调了穗数、穗粒数和粒重的关系,增产幅度6.2%~28.6%.增产原因可能在于促进籽粒灌浆强,增加籽粒中内源Gas、IAA、细胞分裂素(CTKs)的水平,增强了籽粒库活性,同时促进茎叶中干物质向籽粒运转. 相似文献
93.
94.
95.
植物生长调节剂在茄果类蔬菜上的应用进展 总被引:4,自引:0,他引:4
概述了植物生长调节剂的作用和当前茄果类蔬菜作物栽培中常用生长调节剂的种类、主要作用及其调控生理基础,指出了植物生长调节剂使用应注意的问题及其应用前景。 相似文献
96.
97.
REN Yu-sheng WU Zong-gui CUI Fang JIA Guo-liang YU Shi-qing TANG Chao-wu LI Bo 《园艺学报》2002,18(11):1377-1380
AIM: To investigate the effects of platelet-derived growth factor on DNA and collagen protein synthesis in human vascular fibroblasts. METHODS: In the present experiment, the human vascular fibroblasts were cultured and effects of platelet-derived growth factor-BB on DNA and collagen protein synthesis in human vascular fibroblasts were observed by using [3H]-TdR incorporation and [3H]-proline incorporation in vitro. RESULTS: Platelet-derived growth factor-BB significantly promoted NDA synthesis and collagen protein synthesis of quiescent human vascular fibroblasts, with a maximal response at a concentration of 30μg·L-1at 24 h and 36 h, respectively. CONCLUSION: Platelet-derived growth factor-BB promotes DNA and collagen protein synthesis in cultured human vascular fibroblasts. 相似文献
98.
Variation of Parthenium hysterophorus in response to soil quality: implications for invasiveness 总被引:1,自引:0,他引:1
Summary The performance of Parthenium hysterophorus , native to the tropical Americas and invasive to several countries, was evaluated for response to soil quality. Phenological (six stages) and quantitative growth variables [relative growth rates in height (Rh ) and diameter (Rd )] were measured every fortnight. Based on harvest data, the variables, root:shoot (R:S) ratio, specific leaf area (SLA), relative growth rate in biomass (Rw ), net assimilation rate (NAR) and dry matter allocation to plant components, were determined. High clay content in soils prolonged the rosette stage, enhanced Rh and Rd and hampered root growth, but promoted biomass allocation to shoots. The extreme degree of plant mortality was observed, with only 33.3% individuals surviving to reproduce in the soils with highest clay contents. This appears to be one of the most important findings that certainly has a major bearing on the range of adaptation of the weed. Seed mass declined whereas seed production increased in relatively coarser soils with the exception of nearly pure sand. In soils rich in clay, plants produced a smaller number of larger seeds. These data suggest that variation in fundamental functional traits would enable P. hysterophorus to adjust to a variety of habitat conditions. 相似文献
99.
The influence of rain and drought before, and air temperature during, weed control with hot water was studied in laboratory experiments on the test weed Sinapis alba (white mustard). The plants were grown in a greenhouse and treated outdoors. There was no difference in weed control effect when S. alba plants at the four‐leaf stage were treated at the air temperatures 7°C and 18°C. The effective energy dose for a 90% fresh weight reduction was 465 kJ m?2 for both air temperatures. Weed control of S. alba at the four‐ to six‐leaf stage in rainfall above the rainwater run‐off level increased the required effective energy dose by 20% (i.e. 120 kJ m?2) compared with dry plants. A short period of drought just before treatment on S. alba at the two‐ to four‐leaf stage increased the plant fresh weight reduction, which was 22% at low energy dose (190 kJ m?2) and 44% at high energy dose (360 kJ m?2). Hot water weed control should thus be carried out when the plants are drought stressed and avoided when the plants are wet. The air temperature seems to be of little importance in the range 7–18°C. 相似文献
100.
Laboratory evaluation of the insect growth regulator lufenuron againstHelicoverpa armigera on cotton
An insect growth regulator (IGR), lufenuron (Match 5EC), was tested for its toxicity toHelicoverpa armigera on cotton. Potency of the IGR against the larval stage of the pest was demonstrated with respect to larval instars; the LC90 values of 1st, 2nd, 3rd, 4th and 5th instar larvae were 5.63, 7.89, 8.03, 11.39 and 14.76 mg a.i.l
−1, respectively. However, different larval instars did not differ significantly with respect to LC50 and LC10. IGR-treated larvae had swollen heads and were significantly smaller (1.5–2.3 mm) than the untreated control (2.9 mm). Larval
weight was significantly reduced from 190 mg in the control to 50–70 mg in the lufenuron treatment. IGR treatment in the larval
stage significantly affected both pupal length and pupal weight. Pupal duration of the test insect was significantly extended
by IGR treatment. Pupal deformities, including an inability to shed the last larval skin and formation of larval-pupal intermediates,
occurred following treatment. A significant reduction in adult emergence was recorded. In addition, abnormalities in the form
of development of cavities in the forewings of adult were evident. A significant decline in fecundity was noted in the studies.
http://www.phytoparasitica.org posting Feb. 3, 2003. 相似文献