全文获取类型
收费全文 | 7660篇 |
免费 | 545篇 |
国内免费 | 713篇 |
专业分类
8918篇 |
出版年
2024年 | 25篇 |
2023年 | 100篇 |
2022年 | 258篇 |
2021年 | 413篇 |
2020年 | 303篇 |
2019年 | 348篇 |
2018年 | 326篇 |
2017年 | 265篇 |
2016年 | 361篇 |
2015年 | 501篇 |
2014年 | 565篇 |
2013年 | 613篇 |
2012年 | 769篇 |
2011年 | 645篇 |
2010年 | 365篇 |
2009年 | 367篇 |
2008年 | 389篇 |
2007年 | 330篇 |
2006年 | 289篇 |
2005年 | 240篇 |
2004年 | 207篇 |
2003年 | 180篇 |
2002年 | 152篇 |
2001年 | 151篇 |
2000年 | 115篇 |
1999年 | 100篇 |
1998年 | 69篇 |
1997年 | 72篇 |
1996年 | 70篇 |
1995年 | 54篇 |
1994年 | 49篇 |
1993年 | 31篇 |
1992年 | 42篇 |
1991年 | 20篇 |
1990年 | 25篇 |
1989年 | 19篇 |
1988年 | 16篇 |
1987年 | 16篇 |
1986年 | 11篇 |
1985年 | 18篇 |
1984年 | 9篇 |
1983年 | 6篇 |
1982年 | 5篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1966年 | 1篇 |
1965年 | 2篇 |
排序方式: 共有8918条查询结果,搜索用时 15 毫秒
41.
Lei Liu Xu Yang Haoran Wang Guanglin Cui Yujun Xu Peihua Wang Gang Yuan Xiaojing Wang Hu Ding Dao Wen Wang 《Human genetics》2013,132(2):139-145
Recent publications have found an association between variants of exostosin 2 (EXT2) gene and the risk of type 2 diabetes in some population but not in others. In an attempt to address these inconsistencies, we investigated EXT2 variants in two independent cohorts, and conducted a literature-based meta-analysis. Through regression model, we assessed the relationship between the EXT2 single nucleotide polymorphisms (SNPs) (rs3740878, rs11037909 and rs1113132) and the risk of type 2 diabetes in Han Chinese population, including a total of 2,533 cases and 2,643 controls. We combined our data with that from previously published studies and performed a meta-analysis to evaluate the effect size of the gene. Consistent with some studies, we found marginal association for the rs3740878 (OR = 1.07, 95 % CI = 0.99, 1.16, p = 0.09), rs11037909 (OR = 1.07, 95 % CI = 0.99, 1.16, p = 0.08), and rs1113132 (OR = 1.08, 95 % CI = 1.00, 1.17, p = 0.06) in our 2 cohorts. Meta-analysis, comprising 9,224 type 2 diabetes and 10,484 controls, revealed that three SNPs (rs3740878, rs11037909 and rs1113132) in EXT2 were significantly associated with type 2 diabetes (ORs range from 1.06 to 1.07, p = 0.038, p = 0.008 and p = 0.005, respectively). Variation in the EXT2 locus appears to be associated with a small increase in the risk of type 2 diabetes. However, well-designed prospective studies with larger sample size and more ethnic groups are needed to further validate the results. 相似文献
42.
43.
Jing Hui Xiao-jie Yu Xiao-jin Cui Teng Mu Jia-shuai Lin Pei Ni 《Bioscience, biotechnology, and biochemistry》2013,77(9):1514-1521
It is an usual clinical phenomenon that cancer patients are prone to thrombosis. Until now, there have been no efficient methods or appropriate drugs to prevent and cure tumor thrombus. Therefore, the construction of a bifunctional chimeric protein for the treatment of cancer, complicated with thrombosis, is of great significance. Utilizing the superantigenic activity of staphylococcal enterotoxin C2 (SEC2) and the thrombolytic activity of staphylokinase (Sak), Sak-linker-SEC2 and SEC2-linker-Sak were constructed which had good anti-tumor and thrombolytic activities at the same time. Due to the intrinsic emetic activity of SEC2 and high molecular weight (MW) of chimeric proteins (44?kDa), their clinical applications will be restricted. In this study, novel chimeric proteins including ΔSEC2–ΔSak and ΔSak–ΔSEC2 were constructed through the truncation of SEC2 and Sak without 9-Ala linker and His-tag. Compared with the former, both the truncated proteins preserved nearly the same anti-tumor and thrombolytic activities. In addition, their MWs were only 29?kDa and their immunoreactivities were slightly lower than that of Sak-linker-SEC2 and SEC2-linker-Sak, respectively. Therefore, the novel chimeric proteins possessed merits and characteristics, such as low MS, low immunogenicity, and difunctionality which the former had not. It will be of great interest if the above-mentioned proteins can be used to cure Trousseau syndrome in clinic. 相似文献
44.
Dai Yichen Cui Xiaolin Zhang Ge Mohsin Ali Xu Huiming Zhuang Yingping Guo Meijin 《Cytotechnology》2022,74(3):351-369
Cytotechnology - Human umbilical cord mesenchymal stem/stromal cells (hUC-MSCs) have attracted significant research interests in regenerative medicine and cell-based therapies due to their... 相似文献
45.
Removal of agricultural non-point source pollutants by ditch wetlands: implications for lake eutrophication control 总被引:6,自引:0,他引:6
Ditches grown with nature reed (Phragmites communis Trin) and wild rice (Zizania latifolia Turcz) were selected to study the removal capacity of agricultural non-point source pollutants so as to find a way to alleviate
eutrophication in Lake Taihu. Ditches sediment from depths below 40 cm can accumulate organic matter and total nitrogen (TN).
TN is correlated positively to organic matter in reed populated sediment and wild rice populated sediment. This suggests that
the main composition of TN is organic nitrogen derived from plant decomposition. A significant negative relationship between
TN and pH was found in reed and wild rice sediments. Seasonal harvest of helophyte vegetation is an effective method to remove
N and P from wetlands. Organic matter and TN concentrations in water and sediments (0–20 cm) in areas where reeds were removed
are lower than non-harvested areas (control). Reeds and wild rice have high uptake ability of nitrogen (N) and phosphorus
(P). However, the low economic value of these plants will not stimulate voluntary harvest of farmers. Zizania caduciflora Turez Hand-mazt is a kind of vegetable widely cultivated in ditches around the lake. It can also absorb N and P effectively.
Thus, large scale cultivation of Z. caduciflora to replace nature plants may improve water quality. 相似文献
46.
47.
BingZhi Yu Zhe Zhang Xin Deng XiaoYan Xu Chen Feng YanXiao Li Cheng Cui WenHui Su HongMei Zhao DaHai Yu 《中国科学:生命科学英文版》2008,51(9):767-773
Recent studies have suggested that growth factors and hormones play important roles in cell prolif-eration and differentiation during early embryonic development. In the present study, we examined the expression and localization of insulin in the mouse oocytes and one-cell stage embryos by quantitative ELISA, RT-PCR, Western blot and immunofluorescence. In the mouse oocytes and one-cell stage em-bryos, expression of insulin was uniformly distributed in the cytoplasm. We also examined the expres-sion, activity and localization of mTOR (mammalian target of rapamycin) and p70S6K. The expression of mTOR and p70S6K was not significantly different at the cell cycle of mouse one-cell stage embryos. mTOR and S6K were distributed evenly in the cytoplasm at G1, G2 and M phase phase, but at S phase, the distribution of mTOR and S6K was around the pronucleus. At different phases, the activity of mTOR fluctuated. We also used the PI3K specific inhibitor-Wortmannin to investigate the cleavage rate of eggs. The result showed that the rate obviously decreased. When the mTOR specific inhibitor Rapa-mycin was used, the first mitotic division of the mouse one-cell stage embryo was delayed. These re-sults suggested that insulin was expressed both in mouse oocytes and one-cell stage embryos, and may play functional roles in regulation of mouse early embryogenesis by activating the signal pathway of PI3K/PKB/mTOR/S6K. 相似文献
48.
49.
对来源于枯草芽孢杆菌菌株168(Bacillus subtilis 168)的壳聚糖酶编码基因进行了序列优化及全合成,并在毕赤酵母(Pichia pastoris)中实现了分泌表达,表达产物的蛋白质浓度达到0.30mg/ml。表达的壳聚糖酶最适p H为5.6,最适温度为55℃,比酶活达84.54U/ml。该酶在50℃及以下较稳定。利用该酶水解低脱乙酰度壳聚糖并使用超高效液相色谱-四极杆飞行时间质谱(ultra-performance liquid chromatography quadrupole time-of-flight mass spectrometry,UPLC-QTOF MS)对产物的组分进行了分离及鉴定。根据一级质谱信息,推测酶解产物中包含至少37种聚合度2~18,不同脱乙酰度的壳寡糖组分。综上,利用毕赤酵母分泌表达了来源于枯草芽孢杆菌菌株168的壳聚糖酶基因,利用表达产物水解制备了低脱乙酰度壳寡糖并对其组分进行了分析,可为后续壳寡糖结构与功能关系的研究提供参考。 相似文献
50.
Li NJ Zeng GM Huang DL Hu S Feng CL Zhao MH Lai C Huang C Wei Z Xie GX 《Bioresource technology》2011,102(17):8137-8142
The production of oxalate at different initial Pb2+ concentrations during solid-state fermentation of straw with Phanerochaete chrysosporium was investigated. It was found that the maximal peak value of oxalate concentration (22.84 mM) was detected at the initial Pb2+ concentration of 200 mg kg−1 dry straw, while the minimum (15.89 mM) at the concentration of 600 mg Pb2+ kg−1 dry straw, and at moderate concentration of Pb2+ the capability of oxalic acid secretion was enhanced. In addition, it was also found that more oxalic acid accumulation went together with better Pb2+ passivation effect and higher manganese peroxidase (MnP) activity. The present findings will improve the understandings of the interactions of heavy metals with white-rot fungi and the role of oxalate in lignin degradation system, which could provide useful references for more efficient treatment of Pb-contaminated lignocellulosic waste. 相似文献