全文获取类型
收费全文 | 40672篇 |
免费 | 3338篇 |
国内免费 | 3627篇 |
专业分类
47637篇 |
出版年
2024年 | 112篇 |
2023年 | 437篇 |
2022年 | 1108篇 |
2021年 | 1751篇 |
2020年 | 1325篇 |
2019年 | 1592篇 |
2018年 | 1610篇 |
2017年 | 1216篇 |
2016年 | 1630篇 |
2015年 | 2385篇 |
2014年 | 2855篇 |
2013年 | 3137篇 |
2012年 | 3780篇 |
2011年 | 3445篇 |
2010年 | 2243篇 |
2009年 | 1980篇 |
2008年 | 2543篇 |
2007年 | 2182篇 |
2006年 | 1981篇 |
2005年 | 1693篇 |
2004年 | 1535篇 |
2003年 | 1415篇 |
2002年 | 1265篇 |
2001年 | 718篇 |
2000年 | 553篇 |
1999年 | 501篇 |
1998年 | 395篇 |
1997年 | 266篇 |
1996年 | 233篇 |
1995年 | 238篇 |
1994年 | 171篇 |
1993年 | 147篇 |
1992年 | 160篇 |
1991年 | 142篇 |
1990年 | 118篇 |
1989年 | 112篇 |
1988年 | 84篇 |
1987年 | 79篇 |
1986年 | 67篇 |
1985年 | 69篇 |
1984年 | 30篇 |
1983年 | 33篇 |
1982年 | 39篇 |
1981年 | 18篇 |
1979年 | 23篇 |
1978年 | 17篇 |
1977年 | 24篇 |
1976年 | 17篇 |
1975年 | 16篇 |
1972年 | 16篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Bethany M. Henrick Lucie Rodriguez Tadepally Lakshmikanth Christian Pou Ewa Henckel Aron Arzoomand Axel Olin Jun Wang Jaromir Mikes Ziyang Tan Yang Chen Amy M. Ehrlich Anna Karin Bernhardsson Constantin Habimana Mugabo Ylva Ambrosiani Anna Gustafsson Stephanie Chew Heather K. Brown Petter Brodin 《Cell》2021,184(15):3884-3898.e11
992.
MAGE-C2/CT10 promotes growth and metastasis through upregulating c-Myc expression in prostate cancer
Molecular and Cellular Biochemistry - Prostate cancer (PC) is the most common reproductive cancer in men and the third leading cause of cancer death among men worldwide. Recently targeted therapy... 相似文献
993.
994.
Zhang‐Yan Peng Tong‐Han Lan Lei Yang Hu Chao Mei Jia Hua Ping Xu Yong Jie Che Xiang Lin 《Cell biology international》2012,36(11):973-979
Ion current fluctuation of voltage‐dependent potassium channel in LβT2 cells has been investigated by autocorrelation function and DFA (detrended fluctuation analysis) methods. The calculation of the autocorrelation function exponent and DFA exponent of the sample was based on the digital signals or the 0–1 series corresponding to closing and opening of channels after routine evolution, rather than the sequence of sojourn times. The persistent character of the correlation of the time series was evident from the slow decay of the autocorrelation function. DFA exponent α was significantly greater than 0.5. The main outcome has been the demonstration of the existence of memory in this ion channel. Thus, the ion channel current fluctuation provided information about the kinetics of the channel protein. The result suggests the correlation character of the ion channel protein non‐linear kinetics indicates whether the channel is open or not. 相似文献
995.
Jun‐ichi Itoh Ken‐ichiro Hibara Mikiko Kojima Hitoshi Sakakibara Yasuo Nagato 《The Plant journal : for cell and molecular biology》2012,72(6):869-881
Phyllotaxy is defined as the spatial arrangement of leaves on the stem. The mechanism responsible for this extremely regular pattern is one of the most fascinating enigmas in plant biology. In this study, we identified a gene regulating the phyllotactic pattern in rice. Loss‐of‐function mutants of the DECUSSATE (DEC) gene displayed a phyllotactic conversion from normal distichous pattern to decussate. The dec mutants had an enlarged shoot apical meristem with enhanced cell division activity. In contrast to the shoot apical meristem, the size of the root apical meristem in the dec mutants was reduced, and cell division activity was suppressed. These phenotypes indicate that DEC has opposite functions in the shoot apical meristem and root apical meristem. Map‐based cloning revealed that DEC encodes a plant‐specific protein containing a glutamine‐rich region and a conserved motif. Although its molecular function is unclear, the conserved domain is shared with fungi and animals. Expression analysis showed that several type A response regulator genes that act in the cytokinin signaling pathway were down‐regulated in the dec mutant. In addition, dec seedlings showed a reduced responsiveness to exogenous cytokinin. Our results suggest that DEC controls the phyllotactic pattern by affecting cytokinin signaling in rice. 相似文献
996.
马尾松花粉中植物甾醇成分分析 总被引:1,自引:0,他引:1
采用正己烷超声浸提法提取破壁马尾松花粉中的植物甾醇成分,L-B比色法(Liebermann-Burchard)测定马尾松花粉中总甾醇含量,并用GC-MS(气相色谱-质谱联用法)首次对马尾松花粉中的植物甾醇进行详细定性分析。测得马尾松花粉中总甾醇含量为1.680 mg/g,并鉴定出8种植物甾醇成分,分别为:Δ5-菜油甾醇,豆甾醇,Δ7-菜油甾醇,β-谷甾醇,Δ5-燕麦甾醇,禾本甾醇,环阿屯醇和24-亚甲基环木菠萝烷醇。 相似文献
997.
Sapey Enoch Jiang Bingjun Liu Luping Yuan Shan Wu Tingting Ibrahim Seifeldin Elrayah Sun Shi Yue Yanlei Han Tianfu 《Plant Molecular Biology Reporter》2022,40(3):433-445
Plant Molecular Biology Reporter - The j allele delays flowering and enhances yield of long juvenile (LJ) soybean under short day (SD) condition. However, the underlying mechanism of j in flowering... 相似文献
998.
以山梨猕猴桃(Actinidia rufa(Siebold and Zuccarini)Planchon ex Miquel)品种‘63101’和中华猕猴桃(Actinidia chinensis var.chinensis C. F. Liang)品种‘磨山雄7号’杂交产生的400余株F1代个体为材料,连续2~3年对其果实品质和外观特点的9个性状进行测定,分析它们的遗传规律。结果显示,子代群体单果质量连续3年低于双亲中值,遗传传递力连续3年低于100%,优势率连续3年均为负值;可溶性固形物子代中值除2015年略低外,其余2年均高于亲中值12.3%;优势率均为正值,遗传传递力均大于100%;子代果实形状出现分离,与母本圆柱形相同的比例占82%;果皮毛被中,偏离母本的有毛比例为60%;果皮颜色出现绿色、绿褐色、褐色的分离,比例为1∶1.5∶1;果实肩部形状多与母本的方形相似,占比为63%;果肉颜色也多与母本的绿色相似,占比为86%;果实风味中,与父本和母本相似的表型占比均为32%,口感酸的占比18%,超低亲极酸占比1%,超高亲浓甜占比9%。说明杂交子代单果质量和可溶... 相似文献
999.
综合采用样线法、粪堆计数法及重复调查法对甘肃省兴隆山国家级自然保护区的野生马麝(Moschus chrysogaster)进行了种群调查,结合生境分析,确定了其种群分布、数量特征及影响因素。结果表明,兴隆山保护区分布有野生马麝(1159±275)头,平均种群密度为(3.51±0.83)头/km2;各植被类型生境中的野生麝种群数量及密度存在差异,灌丛生境分布有70%的野生马麝种群,达(807±170)头,种群密度为(6.49±1.63)头/km2;针叶林种群密度最大,达(8.85±83.25)头/km2,分布有野生麝(123±45)头;针阔混交林分布最少,仅(41±15)头,种群密度为(5.00±1.84)头/km2;人工林生境无野生马麝分布。保护区各植被类型生境中的野生马麝种群分布差异反映了马麝对适宜生境功能的需求,食物、保温和隐蔽性是制约野生马麝冬季分布和种群数量的关键因素。此外,因生境及人为干扰强度的不同,保护区各区域的野生马麝种群分布存在差异。建议通过减少人为干扰、地表植被管理及人工林管理优化... 相似文献
1000.
Variable selection is critical in competing risks regression with high-dimensional data. Although penalized variable selection methods and other machine learning-based approaches have been developed, many of these methods often suffer from instability in practice. This paper proposes a novel method named Random Approximate Elastic Net (RAEN). Under the proportional subdistribution hazards model, RAEN provides a stable and generalizable solution to the large-p-small-n variable selection problem for competing risks data. Our general framework allows the proposed algorithm to be applicable to other time-to-event regression models, including competing risks quantile regression and accelerated failure time models. We show that variable selection and parameter estimation improved markedly using the new computationally intensive algorithm through extensive simulations. A user-friendly R package RAEN is developed for public use. We also apply our method to a cancer study to identify influential genes associated with the death or progression from bladder cancer. 相似文献