全文获取类型
收费全文 | 13833篇 |
免费 | 1349篇 |
国内免费 | 2017篇 |
出版年
2024年 | 48篇 |
2023年 | 228篇 |
2022年 | 557篇 |
2021年 | 912篇 |
2020年 | 669篇 |
2019年 | 834篇 |
2018年 | 730篇 |
2017年 | 526篇 |
2016年 | 667篇 |
2015年 | 941篇 |
2014年 | 1143篇 |
2013年 | 1125篇 |
2012年 | 1319篇 |
2011年 | 1230篇 |
2010年 | 762篇 |
2009年 | 670篇 |
2008年 | 751篇 |
2007年 | 622篇 |
2006年 | 543篇 |
2005年 | 478篇 |
2004年 | 467篇 |
2003年 | 420篇 |
2002年 | 350篇 |
2001年 | 225篇 |
2000年 | 209篇 |
1999年 | 168篇 |
1998年 | 110篇 |
1997年 | 78篇 |
1996年 | 69篇 |
1995年 | 64篇 |
1994年 | 44篇 |
1993年 | 48篇 |
1992年 | 34篇 |
1991年 | 25篇 |
1990年 | 30篇 |
1989年 | 25篇 |
1988年 | 15篇 |
1987年 | 12篇 |
1986年 | 12篇 |
1985年 | 15篇 |
1984年 | 6篇 |
1983年 | 5篇 |
1982年 | 7篇 |
1981年 | 2篇 |
1980年 | 3篇 |
1950年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 796 毫秒
81.
吲(口朶)乙酸和苄基腺嘌呤对菊芋再生新皮组织分化的影响 总被引:1,自引:0,他引:1
根据前人的研究,植物激素对部分茎段剥皮后新皮再生有一定的影响。草本植物菊芋(Helianthus tuberosus L.)在正常情况下环剥后,其维管组织的分化过程与杜仲、茄子很不一样,对于一些外源激素的刺激反应可能也有差异,为此,有必要应用一些外源激素对菊芋环剥后再生新皮的组织分化进行试验研究。 相似文献
82.
长白猪、枫泾猪和它们的杂种后代Ag—NOR的研究 总被引:11,自引:0,他引:11
4头枫泾猪,3头长白猪和5头长白×枫泾杂一代的NOR平均数分别为3.88、2和2.95。33头长白×枫泾杂二代猪(杂一代互交后代),其中7头黑猪的NOR众数为4,平均数为3.85;9头白猪的NOR众数为2,平均数为2.25;14头白猪的NOR众数为3,平均数为2.86;3头花猪的NOR众数分别为4.3、3,平均数为3.65、3.00和3.08。根据长白、枫泾和长白×枫泾杂一代和杂二代的NOR数目的区别和变化,NOR的遗传符合孟德尔定律。根据NOR数目与毛色的高度相关,提出了决定猪的黑白毛色的基因位于8号染色体并与NOR连锁的假设。猪的毛色除由位于8号染色体上的毛色基因所决定外,还应受其它基因位点的影响。 相似文献
83.
After adenovirus infected HeLa cells were pulse labeled and pulse-chase labeled with 3H-thymidine, the nuclear matrix and DNA remaining tightly bound to the matrix were obtained by sequential cell fractionation. Measuring the radioactivity of labeled DNA indicated that newly synthesized viral DNA specifically attach to the nuclear matrix and the amount of binding DNA is in direct proportion to the viral DNA replication activity: then the DNA gradually detach from the matrix and are involved in viral assembly. Electron microscopic autoradiography of the extracted cells showed the virion and viral DNA associated with the nuclear matrix, and thus further confirmed the anchoring of newly synthesized viral DNA to the nuclear matrix. 相似文献
84.
85.
86.
87.
叶表面角质层在贝母属植物叶鉴定中的意义 总被引:2,自引:0,他引:2
叶表面角质层在贝母属植物叶鉴定中的意义李萍,濮祖茂,蒋鑫,刘惠娟,徐国钧(中国药科大学生药学教研室;分析中心电镜室南京210009)ThediagnosticvalueofthecuticleintheleavesfromgenusFritillar... 相似文献
88.
Ai-Jie Xin Li Cheng Hua Diao Peng Wang Yi-Hua Gu Bin Wu Yan-Cheng Wu Guo-Wu Chen Shu-Min Zhou Shu-Juan Guo Hui-Juan Shi Sheng-Ce Tao 《Clinical proteomics》2014,11(1):10
It is well known that cell surface glycans or glycocalyx play important roles in sperm motility, maturation and fertilization. A comprehensive profile of the sperm surface glycans will greatly facilitate both basic research (sperm glycobiology) and clinical studies, such as diagnostics of infertility. As a group of natural glycan binders, lectin is an ideal tool for cell surface glycan profiling. However, because of the lack of effective technology, only a few lectins have been tested for lectin-sperm binding profiles. To address this challenge, we have developed a procedure for high-throughput probing of mammalian sperm with 91 lectins on lectin microarrays. Normal sperm from human, boar, bull, goat and rabbit were collected and analyzed on the lectin microarrays. Positive bindings of a set of ~50 lectins were observed for all the sperm of 5 species, which indicated a wide range of glycans are on the surface of mammalian sperm. Species specific lectin bindings were also observed. Clustering analysis revealed that the distances of the five species according to the lectin binding profiles are consistent with that of the genome sequence based phylogenetic tree except for rabbit. The procedure that we established in this study could be generally applicable for sperm from other species or defect sperm from the same species. We believe the lectin binding profiles of the mammalian sperm that we established in this study are valuable for both basic research and clinical studies. 相似文献
89.
90.
To interpret visual scenes, visual systems need to segment or integrate multiple moving features into distinct objects or surfaces. Previous studies have found that the perceived direction separation between two transparently moving random-dot stimuli is wider than the actual direction separation. This perceptual “direction repulsion” is useful for segmenting overlapping motion vectors. Here we investigate the effects of motion noise on the directional interaction between overlapping moving stimuli. Human subjects viewed two overlapping random-dot patches moving in different directions and judged the direction separation between the two motion vectors. We found that the perceived direction separation progressively changed from wide to narrow as the level of motion noise in the stimuli was increased, showing a switch from direction repulsion to attraction (i.e. smaller than the veridical direction separation). We also found that direction attraction occurred at a wider range of direction separations than direction repulsion. The normalized effects of both direction repulsion and attraction were the strongest near the direction separation of ∼25° and declined as the direction separation further increased. These results support the idea that motion noise prompts motion integration to overcome stimulus ambiguity. Our findings provide new constraints on neural models of motion transparency and segmentation. 相似文献