全文获取类型
收费全文 | 9961篇 |
免费 | 829篇 |
国内免费 | 869篇 |
专业分类
11659篇 |
出版年
2024年 | 26篇 |
2023年 | 167篇 |
2022年 | 339篇 |
2021年 | 568篇 |
2020年 | 407篇 |
2019年 | 449篇 |
2018年 | 441篇 |
2017年 | 287篇 |
2016年 | 424篇 |
2015年 | 663篇 |
2014年 | 733篇 |
2013年 | 778篇 |
2012年 | 882篇 |
2011年 | 763篇 |
2010年 | 520篇 |
2009年 | 420篇 |
2008年 | 530篇 |
2007年 | 458篇 |
2006年 | 405篇 |
2005年 | 325篇 |
2004年 | 270篇 |
2003年 | 251篇 |
2002年 | 188篇 |
2001年 | 173篇 |
2000年 | 151篇 |
1999年 | 167篇 |
1998年 | 90篇 |
1997年 | 81篇 |
1996年 | 75篇 |
1995年 | 74篇 |
1994年 | 94篇 |
1993年 | 48篇 |
1992年 | 52篇 |
1991年 | 67篇 |
1990年 | 42篇 |
1989年 | 48篇 |
1988年 | 32篇 |
1987年 | 26篇 |
1986年 | 34篇 |
1985年 | 25篇 |
1984年 | 16篇 |
1983年 | 12篇 |
1982年 | 10篇 |
1981年 | 5篇 |
1980年 | 5篇 |
1978年 | 4篇 |
1973年 | 4篇 |
1970年 | 3篇 |
1969年 | 3篇 |
1968年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
91.
Baitian Xu Hongyin Zhang Keping Chen Qin Xu Yao Yao Hui Gao 《Current microbiology》2013,67(2):255-261
A new yeast antagonist, Pichia caribbica, isolated in our laboratory from the soil collected from unsprayed orchards, was evaluated for its biocontrol capability against Rhizopus stolonifer on peaches and the possible mechanisms involved. The decay incidence and lesion diameter of Rhizopus decay of peaches treated by P. caribbica were significantly reduced compared with the control fruits, and the higher the concentration of P. caribbica, the better the efficacy of the biocontrol. Rapid colonization of the yeast in peach wounds stored at 25 °C was observed. In peaches, the activities of peroxidase (POD), catalase (CAT), and phenylalanine ammonia-lyase (PAL) were significantly induced by P. caribbica treatment compared to those of the control fruits. All these results indicated that P. caribbica has a great potential for the development of commercial formulations to control postharvest Rhizopus decay of peaches. Its modes of action were based on competition for space and nutrients with pathogens, inducement of activities of defense-related enzymes such as POD, CAT, and PAL of peaches. 相似文献
92.
Wei Liu Shuxia Ji Xiaoliang Fang Qingguo Wang Zhen Li Fangyin Yao Lei Hou Shaojun Dai 《Journal of Plant Growth Regulation》2013,32(3):483-490
Rice LTRPK1, which encodes a member of the casein kinase I family, has been reported to be involved in root development, hormone response, and metabolic processes. Here we further show that LTRPK1 participates in stress resistance by regulating cytoskeleton rearrangement and formation of cold tolerance and adaptation. Semiquantitative RT-PCR analysis revealed enhanced expression of LTRPK1 in plants subject to low-temperature stress at 4 °C, suggesting a role in low-temperature-related cell responses and signal transduction pathways. Further analysis of LTRPK1-deficient transgenic plants showed that under low-temperature treatment, the growth rate of transgenic plant primary roots, which is commonly used as an indicator for cold stress response abilities, was less inhibited than that of control plants. Moreover, damage to the plasma membrane of root cells in LTRPK1-deficient plants was greater than that of controls as measured by relative electrical conductivity (REC). The malondialdehyde (MDA) content of LTRPK1-deficient plants also increased over that of the control, indicating increased plasma membrane permeability. Further immunofluorescence localization observations indicated that microtubules of transgenic plants subject to low temperature disassembled more rapidly, whereas the control plant microtubules in most cells of the root elongation zone kept their normal habitus, which suggested that LTRPK1-deficient plants had reduced capacity to resist low-temperature stress through regulation of microtubule assembly. These results demonstrate involvement of LTRPK1 in low-temperature stress and provide new insight for rice breeding and germplasm innovation to improve crop cold tolerance. 相似文献
93.
A core functional region of the RFP1 promoter from Chinese wild grapevine is activated by powdery mildew pathogen and heat stress 总被引:1,自引:0,他引:1
Yihe Yu Weirong Xu Jie Wang Lei Wang Wenkong Yao Yan Xu Jiahua Ding Yuejin Wang 《Planta》2013,237(1):293-303
RING-finger proteins (RFP) function as ubiquitin ligases and play key roles in plant responses to biotic and abiotic stresses. However, little information is available on the regulation of RFP expression. Here, we isolate and characterize the RFP promoter sequence from the disease-resistant Chinese wild grape Vitis pseudoreticulata accession Baihe-35-1. Promoter-GUS fusion assays revealed that defense signaling molecules, powdery mildew infection, and heat stress induce VpRFP1 promoter activity. By contrast, the RFP1 promoter isolated from Vitis vinifera was only slightly induced by pathogen infection and heat treatment. By promoter deletion analysis, we found that the ?148 bp region of the VpRFP1 promoter was the core functional promoter region. We also found that, in Arabidopsis, VpRFP1 expressed under its own promoter activated defense-related gene expression and improved disease resistance, but the same construct using the VvRFP1 promoter slightly improve disease resistance. Our results demonstrated that the ?148 bp region of the VpRFP1 promoter plays a key role in response to pathogen and heat stress, and suggested that expression differences between VpRFP1 and VvRFP1 may be key for the differing disease resistance phenotypes of the two Vitis genotypes. 相似文献
94.
95.
96.
目的观察去泛素化酶RPN11和增殖相关核标记物Ki67在结直肠癌组织中的表达,研究其与结直肠癌肿瘤细胞增殖的相关性及与结直肠癌临床病理特征的关系。方法采用免疫组织化学SABC法检测56例结直癌组织及20例癌旁正常组织中的RPN11和Ki67表达,结合临床病理学资料进行统计分析。结果免疫组织化学染色显示:RPN11及Ki67在结直肠癌组织的阳性表达率明显高于正常结直肠组织;RPN11和Ki67的表达均与肿瘤分化程度、TNM分期、转移有关,而与性别、年龄无明显相关;RPN11与Ki67的表达呈正相关。结论RPN11和Ki67可能共同参与结直肠癌肿瘤细胞的增殖调控,并促进结直肠癌的发生发展以及浸润转移。 相似文献
97.
Jian Liu Ning Ding Yao Yu Lanxiang Liu Xincheng Yuan Hongyu Lv Yuqian Zhao Zhenhe Ma 《Journal of biophotonics》2019,12(10)
The occurrence and development of ischemic stroke are closely related to cerebral blood flow. Real‐time monitoring of cerebral perfusion level is very useful for understanding the mechanisms of the disease. A wide field of view (FOV) is conducive to capturing lesions and observing the progression of the disease. In this paper, we attempt to monitor the whole‐brain microcirculation in middle cerebral artery occlusion (MCAO) rats over time using a wide FOV swept‐source OCT (SS‐OCT) system. A constrained image registration algorithm is used to remove motion artifacts that are prone to occur in a wide FOV angiography. During ischemia, cerebral perfusion levels in the left and right hemispheres, as well as in the whole brain were quantified and compared. Changes in the shape and location of blood vessels were also recorded. The results showed that the trend in cerebral perfusion levels of both hemispheres was highly consistent during MCAO, and the position of the blood vessels varied over time. This work will provide new insights of ischemic stroke and is helpful to assess the effectiveness of potential treatment strategies. 相似文献
98.
Zhu XM Yao FH Yao YM Dong N Yu Y Sheng ZY 《The international journal of biochemistry & cell biology》2012,44(7):1097-1105
High mobility group box-1 protein (HMGB1) had been proved to induce maturation and activation of dendritic cell (DC), however, the endogenous changes and mechanisms underlying are unknown. Since endoplasmic reticulum stress (ERS) activates an adaptive unfolded protein response (UPR) that facilitates cellular survival and repair, we hypothesized that HMGB1 may regulate the function of DC by modulating ERS. In our study, HMGB1 stimulation induced significant ERS responses in DCs in a time- and dose-dependent manner, demonstrated by the up-regulation of a number of ERS markers. Gene silence of XBP-1 in splenic DCs decreased the levels of CD80, CD86 as well as major histocompatibility complex (MHC)-II expression and cytokine secretion after HMGB1 treatment, when compared with untransfected or nontargeting-transfected DCs (all P<0.05). Moreover, XBP-1 silenced DCs after treatment with HMGB1 failed to stimulate notable proliferation and differentiation of T cells, unlike normal DCs or nontargeting-transfected DCs (all P<0.05). Gene silence of XBP-1 resulted in down-regulation of the receptor for advanced glycation end products (RAGE) expression on the surface of splenic DCs induced by HMGB1 stimulation (P<0.05). These findings demonstrate an important role for ERS and its regulator XBP-1 in HMGB1-induced maturation and activation of DCs. 相似文献
99.
Three new compounds, 1 – 3 , and 20 known compounds were isolated from the AcOEt and BuOH extract of edible Opuntia Milpa Alta. The petroleum ether extract was examined by GC and MS. A total of 26 compounds were identified, representing 95.6% of the total extract, phytosterol (36.03%) being the most abundant component, and polyunsaturated fatty acids (18.57%) represented the second largest group, followed by phytol (12.28%), palmitic acid, palmitate (13.54%), vitamin E (4.51%), and other compounds (7.47%). The effects of various extracts from edible Opuntia Milpa Alta (petroleum ether extract, AcOEt extract, BuOH extract, aqueous extract, H2O parts) and the positive control (received dimethylbiguanide) were tested on streptozotocin (STZ)‐induced diabetic mice. The results indicated that all the treatment groups could significantly decrease blood glucose levels in STZ‐induced diabetic mice compared to the model control group (P<0.01), except the aqueous extract group (P<0.05). Especially, the petroleum ether extract group and the positive control group showed remarkable decrease of blood glucose levels. Taken together, the results indicate that the petroleum ether extract is the major hypoglycemic part in edible Opuntia Milpa Alta, which may be developed to a potential natural hypoglycemic functional ingredient. 相似文献
100.
Effects of organic matter incorporation on nitrous oxide emissions from rice-wheat rotation ecosystems in China 总被引:8,自引:0,他引:8
Zhisheng Yao Zaixing Zhou Xunhua Zheng Baohua Xie Baoling Mei Rui Wang Klaus Butterbach-Bahl Jianguo Zhu 《Plant and Soil》2010,327(1-2):315-330
Organic matter addition is thought to be an important regulator of nitrous oxide (N2O) emissions from croplands. Contradictory effects, however, were reported in previous studies. To investigate the effects of crop residue management on N2O emissions from rice-wheat rotation ecosystems, we conducted field experiments at three sites (Suzhou, Wuxi and Jiangdu) in the Yangtze River Delta, using static chamber and gas chromatography methods. Our data show that N2O emissions throughout the rice season from plots treated with wheat straw application at a high rate (WS) prior to rice transplanting (1.1–2.0 kg N ha?1) were significantly lower (P?<?0.05) than those from the control plots without organic matter addition or added with wheat straw at a moderate rate (1.6–2.9 kg N ha?1). Furthermore, the WS treatments had a residual inhibitory effect on N2O emissions in the following non-rice season, which consistently resulted in significantly lower emissions (P?<?0.05) compared to the control treatments (2.2–3.1 vs. 3.9–5.6 kg N ha?1). In comparison to the control treatments, the WS treatments reduced both the seasonal and annual direct emission factors of the applied nitrogen (EFd) by 50–68% (mean: 57%). The addition of compost (aerobically composted rice or wheat straw harvested in the last rotation) reduced the seasonal and annual EFds by 29–32%. Over the entire rice-wheat rotation cycle, annual N2O emissions from the fertilized fields at the three sites ranged from 3.3?±?0.3 to 16.8?±?0.6 kg N ha?1, with a coefficient of variation (CV) of 61%. Similarly, the EFds during the rice-wheat rotation cycle ranged from 0.4% to 2.5%, with a CV of 67%. These high spatial variations might have been related to: variations in soil properties, such as texture and soil organic carbon; management practices, such as straw treatments (i.e., compost versus fresh straw) and weather conditions, such as precipitation and rainfall distribution. Our results indicate that the incorporation of fresh wheat straw at a high rate during the rice season is an effective management practice for the mitigation of N2O emissions in rice-wheat rotation systems. Whether this practice is also effective in reducing the overall global warming potential of net N2O, CH4 and CO2 emissions needs to be seen through further studies. 相似文献