全文获取类型
收费全文 | 1681篇 |
免费 | 149篇 |
国内免费 | 146篇 |
专业分类
1976篇 |
出版年
2024年 | 4篇 |
2023年 | 27篇 |
2022年 | 76篇 |
2021年 | 90篇 |
2020年 | 63篇 |
2019年 | 94篇 |
2018年 | 83篇 |
2017年 | 43篇 |
2016年 | 73篇 |
2015年 | 128篇 |
2014年 | 143篇 |
2013年 | 135篇 |
2012年 | 153篇 |
2011年 | 140篇 |
2010年 | 78篇 |
2009年 | 74篇 |
2008年 | 81篇 |
2007年 | 63篇 |
2006年 | 73篇 |
2005年 | 47篇 |
2004年 | 37篇 |
2003年 | 34篇 |
2002年 | 42篇 |
2001年 | 22篇 |
2000年 | 29篇 |
1999年 | 16篇 |
1998年 | 11篇 |
1997年 | 17篇 |
1996年 | 12篇 |
1995年 | 19篇 |
1994年 | 7篇 |
1993年 | 10篇 |
1992年 | 6篇 |
1991年 | 9篇 |
1990年 | 10篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1987年 | 3篇 |
1986年 | 7篇 |
1985年 | 3篇 |
1984年 | 4篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1979年 | 1篇 |
排序方式: 共有1976条查询结果,搜索用时 0 毫秒
11.
Liu Qian Wang Zinuo Zhang Ning Zuo Jian Feng Haibo Duan Huabo 《The International Journal of Life Cycle Assessment》2021,26(6):1285-1297
The International Journal of Life Cycle Assessment - As an ambitious strategy of national interest in China and with an aim at achieving the ‘one-hour economic circle’ among Greater Bay... 相似文献
12.
Paper is increasingly recognized as a portable substrate for cell culture, due to its low-cost, flexible, and special porous property, which provides a native cellular 3D microenvironment. Therefore, paper-based microfluidics has been developed for cell culture and biomedical analysis. However, the inability of continuous medium supply limits the wide application of paper devices for cell culture. Herein, a paper-based microfluidic device is developed with novel folded paper strips as wick-like structure, which is used for medium self-driven perfusion. The paper with patterns of hydrophilic channel, culture areas, and hydrophobic barrier could be easily fabricated through wax-printing. After printing, the hydrophilic paper strip at the periphery of the lower layer is then folded at 90° and extended into the medium container for continuous automatic supply of medium to the cell culture area. Tumor cells cultured in the paper device are tested for anti-cancer drug screening. Visualized cell viability and chemical sensitivity testing can be achieved by colorimetry combined with simple smartphone imaging, effectively reducing precision instrument dependence. The wick paper-based microfluidic device for cell culture endows the method the advantages of lower cost, ease-of-operation, miniaturization, and shows a great potential for large-scale cell culture, antibody drug production, and efficient screening. 相似文献
13.
Feng Wang Li Zuo Bo Hong Dongyi Han Ethan M Range Lingyun Zhao Yanan Sui Weiwei Guo Liangfa Liu 《Journal of biomedical science》2013,20(1):91
Background
Noise induced injury of the cochlea causes shifts in activation thresholds and changes of frequency response in the inferior colliculus (IC). Noise overexposure also induces pathological changes in the cochlea, and is highly correlated to hearing loss. However, the underlying mechanism has not been fully elucidated. In this study, we hypothesized that overexposure to noise induces substantial electrophysiological changes in the IC of guinea pigs.Results
During the noise exposure experiment, the animals were undergoing a bilateral exposure to noise. Additionally, various techniques were employed including confocal microscopy for the detection of cochlea hair cells and single neuron recording for spontaneous firing activity measurement. There were alterations among three types of frequency response area (FRA) from sound pressure levels, including V-, M-, and N-types. Our results indicate that overexposure to noise generates different patterns in the FRAs. Following a short recovery (one day after the noise treatment), the percentage of V-type FRAs considerably decreased, whereas the percentage of M-types increased. This was often caused by a notch in the frequency response that occurred at 4 kHz (noise frequency). Following a long recovery from noise exposure (11–21 days), the percentage of V-types resumed to a normal level, but the portion of M-types remained high. Interestingly, the spontaneous firing in the IC was enhanced in both short and long recovery groups.Conclusion
Our data suggest that noise overexposure changes the pattern of the FRAs and stimulates spontaneous firing in the IC in a unique way, which may likely relate to the mechanism of tinnitus. 相似文献14.
15.
Xiaofei Lv Yuan Zhang Shaoqi Rao Dongfang Su Dan Feng Min Wang Xinrui Li Dan Li Honghui Guo Xiaoyu Zuo Min Xia Haimei Ouyang Wenhua Ling Jian Qiu 《Gene》2013
Studies focusing on the association of gene methylthioadenosine phosphorylase (MTAP) with the risk of coronary artery disease (CAD) and myocardial infarction (MI) are limited. 相似文献
16.
Shuangshuang Yin Wenyuan Gao Yuyong Liang Juan Wang Hui Liu Changlong Wei Beimei Zuo 《Acta Physiologiae Plantarum》2013,35(5):1579-1585
In this study, we investigated the induction of Pseudostellaria heterophylla adventitious root and the effects of sucrose concentration and phosphate source on biomass increase and metabolites accumulation. These roots were initially cultured in Murashige and Skoog medium for 4 weeks. IBA 3.0 mg L?1 proved to be the best auxin for inducing adventitious roots and the frequency of adventitious roots induced from roots (100 %) was higher than that from leaves (78 %) and stems (27 %). The medium with 4 % sucrose resulted in the optimum biomass i.e. 1.04 g/flask DW, and the content of saponin and polysaccharides reached the peak i.e. 0.676 and 24.4 %, respectively. With regards to phosphate source, 1.25 mM phosphate concentration was more favorable for biomass of roots (0.87 g/flask of DW), whereas the optimum saponin (0.74 %) and polysaccharides (22.09 %) were achieved with 2.5 mM phosphate. However, the saponin content at 2.5 mM phosphate did not show significant difference from the saponin content at 0.625 mM (0.69 %) or 3.75 mM phosphate (0.69 %). 相似文献
17.
Haiyang Chen Yanguo Teng Jinsheng Wang Liuting Song Rui Zuo 《Biological trace element research》2013,151(3):462-470
In this study, a method of positive matrix factorization (PMF) combined support vector machines (SVMs) was adopted to identify possible sources and apportion contributions for trace element pollution in surface sediments from the Jinjiang River, Southeastern China. Utilizing diagnostics tools, four significant factors were extracted from sediment samplers, which were collected in December 2010 at 15 different sites. By treating source identification as a pattern recognition problem, the factor loadings derived from PMF were classified by SVM classifiers which have been trained and validated with fingerprints of eight potential source categories. Using SVM, industrial wastewater from lead ore mining and metal handcraft manufacture, atmospheric deposition, and natural background were identified as main sources of trace element pollution in surface sediments from the Jinjiang River, which were affirmed by visually comparing compound patterns and the differences between the predicted and actual fractional compositions. Apportionment results showed that source of lead ore mining made the largest contribution (33.62 %), followed by atmospheric deposition (30.99 %), metal handcraft manufacture (30.09 %), and natural background (5.29 %). 相似文献
18.
Jing Yao Chongzhao Hao Ke Yu Hai Zuo Yanli Chen Qing Ma 《Journal of Phytopathology》2013,161(1):18-26
The penetration process and defence reactions (hypersensitive response, oxidative burst and cell wall fortification) of Colletotrichum orbiculare were studied histochemically on pepper cultivar ‘A11’ (non‐host) and susceptible cucumber cultivar ‘Changchun Thorn’ (host). The results indicate that C. orbiculare could hardly penetrate the non‐host pepper leaves. It was papillae rather than hypersensitive response and H2O2 that played an important role in resisting the colonization and development of C. orbiculare on the non‐host pepper. The depolymerization of the actin microfilament weakened the papilla deposition of pepper and allowed successful penetration of the non‐adapted C. orbiculare, suggesting that the actin cytoskeleton of pepper is significant in preventing the invasion of the non‐host pathogen C. orbiculare. 相似文献
19.
The common cold is most often a result of human rhinovirus (HRV) infection. Common cold symptoms including rhinorrhea and nasal obstruction frequently occur during HRV infection of the upper respiratory tract. Conversely, HRV may also infect the epithelial cells of the lower respiratory tract. Symptom severity associated with HRV infection ranges from mild to potentially serious depending on a person’s susceptibility and pre-existing condition, such as chronic obstructive pulmonary disease. An over active host immune response is believed to be the primary contributor to HRV pathogenesis. Enhanced activity of various host cell cytokines and granulocytes mediate specific cellular pathways inducing many of the symptoms associated with HRV infection. There are over 100 serotypes of HRV which can be further categorized based on the specific characteristics of each type. The two main categories of HRV consist of the major and minor groups. The unique host cell receptor is the distinguishing factor between these two groups. Yet, these viruses may also differ in mechanism of infection and replication. Due to the high frequency of hospital and clinical visits and the corresponding economic burden, novel therapies are of interest. Several different treatment options varying from herbal remedies to anti-viral drugs have been studied. However, the vast number of HRV serotypes complicates the progress of developing a universal treatment for attenuating HRV infection. 相似文献
20.