全文获取类型
收费全文 | 2153篇 |
免费 | 273篇 |
国内免费 | 154篇 |
专业分类
化学 | 864篇 |
晶体学 | 5篇 |
力学 | 502篇 |
综合类 | 51篇 |
数学 | 446篇 |
物理学 | 712篇 |
出版年
2024年 | 13篇 |
2023年 | 40篇 |
2022年 | 115篇 |
2021年 | 90篇 |
2020年 | 65篇 |
2019年 | 62篇 |
2018年 | 81篇 |
2017年 | 100篇 |
2016年 | 104篇 |
2015年 | 84篇 |
2014年 | 110篇 |
2013年 | 166篇 |
2012年 | 136篇 |
2011年 | 132篇 |
2010年 | 100篇 |
2009年 | 131篇 |
2008年 | 140篇 |
2007年 | 121篇 |
2006年 | 81篇 |
2005年 | 83篇 |
2004年 | 94篇 |
2003年 | 68篇 |
2002年 | 57篇 |
2001年 | 46篇 |
2000年 | 49篇 |
1999年 | 38篇 |
1998年 | 36篇 |
1997年 | 27篇 |
1996年 | 23篇 |
1995年 | 25篇 |
1994年 | 21篇 |
1993年 | 21篇 |
1992年 | 21篇 |
1991年 | 18篇 |
1990年 | 17篇 |
1989年 | 8篇 |
1988年 | 8篇 |
1987年 | 9篇 |
1986年 | 8篇 |
1985年 | 5篇 |
1984年 | 9篇 |
1982年 | 4篇 |
1981年 | 5篇 |
1980年 | 1篇 |
1979年 | 3篇 |
1978年 | 1篇 |
1977年 | 3篇 |
1974年 | 1篇 |
排序方式: 共有2580条查询结果,搜索用时 15 毫秒
151.
《Electrophoresis》2017,38(24):3155-3160
Messenger RNA (mRNA) profiling is a technique increasingly applied for the forensic identification of body fluids and skin. More recently, an mRNA‐based organ typing assay was developed which allows for the inference of brain, lung, liver, skeletal muscle, heart, kidney, and skin tissue. When applying this organ typing system in forensic casework for the presence of animal, rather than human, tissue is an alternative scenario to be proposed, for instance that bullets carry cell material from a hunting event. Even though mRNA profiling systems are commonly in silico designed to be primate specific, physical testing against other animal species is generally limited. In this study, human specificity of the organ tissue inferring system was assessed against organ tissue RNAs of various animals. Results confirm human specificity of the system, especially when utilizing interpretation rules considering multiple markers per cell type. Besides, we cross‐tested our organ and body fluid mRNA assays against the target types covered by the other assay. Marker expression in the nontarget organ tissues and body fluids was observed to a limited extent, which emphasizes the importance of involving the case‐specific context of the forensic samples in deciding which mRNA profiling assay to use and when for interpreting results. 相似文献
152.
153.
提取了8种海参中的粗多糖,经DEAE-52阴离子交换柱分离纯化得到其中的海参硫酸软骨素(SC-CHS),除日本刺参CHS外其余均为首次获得的海参多糖。对获得的SC-CHS进行分子量、单糖组成及硫酸基含量等基本性质分析后,利用高温1HNMR对SC-CHS结构进行初步鉴别。结果表明,高温条件下SC-CHS的1HNMR图谱具有较好的分辨度。对其支链硫酸化岩藻糖的异头氢进行归属和比较,并以此为指标鉴别不同种类海参硫酸软骨素的结构差异,建立了一种以海参硫酸软骨素结构特征为指标的海参指纹图谱;初步探讨了不同海域生长的海参中硫酸软骨素支链岩藻糖硫酸基的特点,比较发现:寒带海域海参的硫酸软骨素岩藻糖上硫酸基取代以2,4-di OSO3、3,4-di OSO3双取代为主,含部分4-OSO3单取代;温带海域海参以2,4-di OSO3双取代为主,含部分4-OSO3单硫酸基取代;热带亚热带海域海参以2,4-di OSO3双取代和4-OSO单取代为主。这将为海参构效关系的进一步分析鉴定提供理论依据。 相似文献
154.
Keng-hsing Chao 《Optics Communications》2011,284(21):5221-5224
In this paper, we report on a micro tunable cat's eye retro-reflector. The tunability is obtained through the use of a smart film, a polymer dispersed liquid crystal device (PDLC). The cat's eye device consists of three subassemblies, a front-side focusing unit, the smart film, and a back-side reflecting unit. The characterization of the device, considering possible fabrication inaccuracy such as misalignment, is presented. Such a device can be used in a free-space communication system, or more specifically, an optical identification system. 相似文献
155.
156.
针对一维的海冰-海水耦合热力学系统,以该系统中的物理参数为辨识量,以温度偏差为目标函数,建立了一个参数辨识模型,并证明了该问题最优解的存在性,从而为这类海冰-海水耦合热力学系统参数辨识问题的数值计算提供数学理论依据. 相似文献
157.
《Analytical letters》2012,45(5):868-878
Efficient protein digestion is a key step for successful mass spectrometry identification. However, traditional in-solution digestion suffers some drawbacks, such as autolysis of protease, long analysis times and lack of control. Recently, specific single-stranded nucleic acids, aptamers, screened from random sequence pools, have been performed high affinity for targets. In this paper, we have developed a novel enzyme reactor, which immobilized chymotrypsin based on aptamer-grafted silica beads. Mixed proteins, which consist of bovine serum albumin, myoglobin, and cytochrome c, were used as samples, to evaluate the digestion performance of the enzymatic reactor. With the use of this novel tool, proteins were digested in 40 min to an extent similar to that achieved with soluble enzyme at 37°C after 16 h. Moreover, enzymatic reactor regeneration was carried out through chymotrypsin elution and re-immobilization. The advanced characteristics of the aptamer-based chymotrypsin reactor demonstrated that aptamers could serve as novel materials for rapid and efficient enzyme immobilization and application in protein studies. 相似文献
158.
Alexander V. Avdeev Eldar V. Goriounov Mikhail M. Lavrentiev Jr. Renato Spigler 《Applied Mathematical Modelling》2009
A behavior-oriented diffusion model, governing the time evolution of the cross-shore position of coastal profiles, is studied. Here, two time-independent, space-varying coefficients, which embody the relevant physical properties, are identified simultaneously. Two sets of real data, the first measured over 10 years at Duck, in NC (USA), the second obtained over 39 years measurements at Delfland (Holland), have been processed numerically by a suitable “inversion algorithm”, earlier developed by the authors. This is based on the minimization of a certain cost functional in order to identify both coefficients. The numerical results, obtained by solving the diffusion equation with the so-determined coefficients, favorably agree with the real data, which fact validates and calibrates somehow the diffusion model under investigation. A short-term prediction is finally obtained for coastal profiles, using such a model. 相似文献
159.
160.