全文获取类型
收费全文 | 8535篇 |
免费 | 519篇 |
国内免费 | 1012篇 |
专业分类
林业 | 955篇 |
农学 | 969篇 |
基础科学 | 532篇 |
1138篇 | |
综合类 | 3153篇 |
农作物 | 620篇 |
水产渔业 | 459篇 |
畜牧兽医 | 1296篇 |
园艺 | 409篇 |
植物保护 | 535篇 |
出版年
2024年 | 35篇 |
2023年 | 145篇 |
2022年 | 299篇 |
2021年 | 353篇 |
2020年 | 372篇 |
2019年 | 318篇 |
2018年 | 253篇 |
2017年 | 354篇 |
2016年 | 312篇 |
2015年 | 385篇 |
2014年 | 462篇 |
2013年 | 454篇 |
2012年 | 600篇 |
2011年 | 684篇 |
2010年 | 584篇 |
2009年 | 473篇 |
2008年 | 462篇 |
2007年 | 366篇 |
2006年 | 344篇 |
2005年 | 357篇 |
2004年 | 206篇 |
2003年 | 293篇 |
2002年 | 411篇 |
2001年 | 401篇 |
2000年 | 251篇 |
1999年 | 161篇 |
1998年 | 122篇 |
1997年 | 87篇 |
1996年 | 85篇 |
1995年 | 64篇 |
1994年 | 66篇 |
1993年 | 53篇 |
1992年 | 45篇 |
1991年 | 56篇 |
1990年 | 44篇 |
1989年 | 30篇 |
1988年 | 26篇 |
1987年 | 12篇 |
1986年 | 4篇 |
1985年 | 4篇 |
1984年 | 4篇 |
1983年 | 3篇 |
1982年 | 2篇 |
1981年 | 5篇 |
1980年 | 4篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1956年 | 3篇 |
1955年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
961.
培养适应 2 1世纪我国社会主义现代化建设要求的高素质专门人才 ,是高等职业教育贯彻落实国家教育方针的重要任务 ,作为高等职业教育与社会结合点的专业 ,是保证培养适销对路人才的重要环节 ,因此 ,加强高等职业教育专业的规范化管理有着重要的实践意义 相似文献
962.
宝珠梨疫腐病病原菌研究 总被引:1,自引:0,他引:1
宝珠梨疫腐病是云南省的一种新记录病害,其病原菌为恶疫霉Phytophthora cactorum (Lebert et Cohn) Schrot.适宜恶疫霉分离培养的培养基是番茄汁培养基、V8汁培养基和PDA培养基。适宜恶疫霉生长的pH值范围在3~10之间,最适pH值为5~6,适宜生长的温度范围为在10~30℃之间,最适生长的温度为20~25℃. 恶疫霉对果糖、麦芽糖、蔗糖等碳源的利用好于其它碳源,对酵母膏、天门冬酰胺、牛肉膏等氮源的利用好于其它氮源。 相似文献
963.
河南省豆科植物根瘤菌表型多样性研究 总被引:1,自引:1,他引:1
在河南省根瘤菌资源调查的基础上 ,选取 2 9株快生根瘤菌和 34株参比菌株 ,进行了 10 2项表型性状测定和聚类分析。结果表明 :不同地理来源、甚至同一地理来源或同种寄主的不同菌株在碳氮源利用、抗生素抗性、耐逆性等方面存在着较大的多样性。有 7株菌对链霉素、青霉素和白霉素有较强的耐受性 ;有 2 3株和 2 5株菌可分别耐受 2 .0 g/ L的香酚兰和中性红 ;有 2株菌可在含 5 0 g/ L Na Cl的 YMA培养基上生长 ;有 6株菌在 p H值 11条件下能够生长。在 84 %的相似性水平上未知菌株构成了 2个独立的表观群 ,其中 Cluster 1有 7株菌 ,中心菌株为 H 0 38;Cluster 2有 3株菌 ,中心菌株为 H0 2 6。 相似文献
964.
玉米氮、磷、钾肥料效应的研究 总被引:4,自引:1,他引:4
在吉林省蛟河市对玉米进行"3414"肥效试脸,拟合了肥料效应三元二次方程和一元二次方程。通过三元二次方程得出,在该土壤条件下氮、磷、钾最高施肥量为(kg/hm2)N-P2O5-K2O=212.24-57.0-78.3,对应的最高产量为10 551.5 kg/hm2;最佳施肥量(kg/hm2)N-P2O5-K2O=168.4-55.4-63.2,对应的产量为10 432.7kg/hm2。通过拟合一元二次方程得出,在该土壤条件下氮、磷、钾最高施肥量为212.1 kg/hm2、67.0 kg/hm2、64.0kg/hm2;最佳经济施肥量184.1 kg/hm2、63.0 kg/hm2、60.3 kg/hm2。 相似文献
965.
966.
GUO Zheng-hui HUANG Hai DU Tao XU Ke-wei CAO Yi CHEN Jie-qing DONG Wen YAO You-sheng LIN Tian-xin XIE Wen-lian JIANG Chun HAN Jin-li HUANG Jian 《园艺学报》2011,27(6):1090-1096
AIM: To study the expression of prostate-specific membrane antigen (PSMA) on the level of phospho-ERK, cell growth and migration of prostate cancer LNCaP cells.METHODS: The method of silencing PSMA was established by lentivirus-mediated RNAi in our early experiment. The cells were divided into 3 groups.In experimental group, the expression of PSMA in LNCaP cells was stably blocked by lentivirus-mediated RNAi. In negative control group, the cells were transfected with lentivirus-mediated control RNAi (without any interference to PSMA).The normal LNCaP cells served as blank control. The cells in these 3 groups were cultured in both 2 environments: normal medium and medium with PD98059 (an inhibitor of ERK phosphorylation). The phospho-ERK was detected by Western blotting and immunocytochemistry. Furthermore, the growth and migration of the cells were evaluated by MTT and transwell assays,respectively.RESULTS: In normal medium, the expression of phospho-ERK was attenuated in experimental group (P<0.05) and the quantity of "positive" cells was less than those in other 2 groups (P<0.05). Furthermore, the growth curves of the cells showed that the growth ability in experimental group was significantly decreased (P<0.05, after 48 h) and the migration ability in experimental group was reduced (P<0.05). In the inhibitory medium, the cells in all 3 groups expressed phospho-ERK at a lower level. Moreover, the abilities of growth and migration in these 3 groups were poorly displayed. These inhibitory effects on phosphorylation of ERK were similar to the cells in experimental group cultured in normal medium.CONCLUSION: PSMA may play a role in up-regulation of phospho-ERK and it may take an advantage in growth and migration of prostate cancer LNCaP cells. 相似文献
967.
螺虫乙酯对烟粉虱的防治效果评价 总被引:8,自引:0,他引:8
采用室内毒力测定与田间试验相结合的方法,研究了螺虫乙酯(Movento)对烟粉虱的防治效果。室内毒力测定结果表明:96 %螺虫乙酯原药对烟粉虱卵和若虫都具有非常高的杀虫活性,LC50分别为18.91 mg?L-1和14.97 mg?L-1,与对照95 %吡虫啉没有显著差异|但对烟粉虱成虫的杀虫效果并不十分理想,LC50达到了453.34 mg?L-1,且显著高于对照95 %吡虫啉。田间试验结果表明:24 %螺虫乙酯悬浮剂(SC)对烟粉虱有良好的防效和持效性,且螺虫乙酯与Biopower(助剂)混用的防效明显优于螺虫乙酯单独使用的效果|螺虫乙酯与0.2 %〔0.24 g?(667 m2)-1〕Biopower混用,药后1~28 d对烟粉虱的防效分别为64.91 %~66.92 %、82.00 %~82.59 %、88.11 %~89.97 %、89.99 %~93.94 %和91.10 %~93.56 %。 相似文献
968.
原状黄土的抗剪强度与黄土的干容重、含水量、粘粒含量等物理力学性质有关.通过对具体参数指标的分析,确定了不同区域内黄土的土性参数,进而提出了深路堑边坡的稳定性分析及打滑桩设计. 相似文献
969.
Peng-Fei Fan Han-Lan Fei Matthew B. Scott Wen Zhang Chang-Yong Ma 《Biological conservation》2011,(9):2247-2254
Knowledge of habitat and feeding ecology is essential for developing an effective conservation management plan for threatened primates. Despite having been rediscovered nearly a decade ago, very little is known of the critically endangered cao vit gibbon (Nomascus nasutus) or its habitat. We analysed forest cover, made direct observations and conducted interviews of local elders to better understand forest changes and to determine the forest characters and species important to the survival of the gibbon. Interviews indicated human-induced forest resource exploitation focused on species-specific and larger trees most easily accessed. Gibbon forest habitat comprised four primary forest types. The mean canopy height over the whole site was 10.52 m. Gibbons consumed 81, or nearly half of the tree and liana species recorded in the site; however, only 19 species provide 77.8% of the diet. Six of the 19 food species were logged for different reasons throughout the history of the site. We conclude that effective conservation management of primates with highly limited distributions, focused dietary needs, and in degraded ecosystems will require active forest restoration, such as planting important food species in degraded sites. 相似文献
970.
Lee MY Liao MH Tsai YN Chiu KH Wen HC 《Journal of agricultural and food chemistry》2011,59(6):2347-2355
The Tithonia diversifolia methanolic extract (TDM), which showed antiproliferative activity against human glioblastoma U373 cells, with an IC50 value of 59.2±3.7 μg mL(-1), was passed through silica gel chromatography and successively eluted with different percentages of EtOAc/hexane. The 10-60% EtOAc/hexane subfractions, which exhibited a comparatively higher antiproliferative activity, were isolated, and then structural identification was proceeded with 1H nuclear magnetic resonance. The isolated compound was tagitinin C, a kind of sesquiterpenoid. The IC50 value was 6.1±0.1 μg mL(-1) in U373 treated with tagitinin C. In flow cytometric analysis and inhibition of pan-caspase, the results showed that the anti-glioblastoma effect was apoptosis-independent. In PARP, p-p38, ULK1, and LC3-II expression, the anti-glioblastoma induced by tagitinin C was likely via autophagy. In the ULK1 siRNA transfection experiment, autophagy blockade counteracted the suppression induced by tagitinin C. The result suggested that tagitinin C induces U373 cell death dependent upon autophagy under certain conditions. 相似文献