全文获取类型
收费全文 | 5174篇 |
免费 | 889篇 |
国内免费 | 798篇 |
专业分类
化学 | 3978篇 |
晶体学 | 85篇 |
力学 | 358篇 |
综合类 | 86篇 |
数学 | 509篇 |
物理学 | 1845篇 |
出版年
2024年 | 27篇 |
2023年 | 113篇 |
2022年 | 250篇 |
2021年 | 264篇 |
2020年 | 267篇 |
2019年 | 259篇 |
2018年 | 235篇 |
2017年 | 250篇 |
2016年 | 299篇 |
2015年 | 337篇 |
2014年 | 372篇 |
2013年 | 455篇 |
2012年 | 524篇 |
2011年 | 474篇 |
2010年 | 353篇 |
2009年 | 327篇 |
2008年 | 311篇 |
2007年 | 266篇 |
2006年 | 217篇 |
2005年 | 194篇 |
2004年 | 128篇 |
2003年 | 108篇 |
2002年 | 124篇 |
2001年 | 100篇 |
2000年 | 106篇 |
1999年 | 83篇 |
1998年 | 56篇 |
1997年 | 51篇 |
1996年 | 47篇 |
1995年 | 42篇 |
1994年 | 30篇 |
1993年 | 28篇 |
1992年 | 32篇 |
1991年 | 26篇 |
1990年 | 23篇 |
1989年 | 16篇 |
1988年 | 8篇 |
1987年 | 5篇 |
1986年 | 4篇 |
1985年 | 11篇 |
1984年 | 5篇 |
1983年 | 9篇 |
1982年 | 8篇 |
1981年 | 3篇 |
1979年 | 5篇 |
1977年 | 3篇 |
1975年 | 1篇 |
1973年 | 1篇 |
1957年 | 2篇 |
1936年 | 1篇 |
排序方式: 共有6861条查询结果,搜索用时 15 毫秒
11.
Xue Luan Zhongcheng Cong Tassos P. Anastassiades Yin Gao 《Molecules (Basel, Switzerland)》2022,27(10)
Previously synthesized N-butyrylated hyaluronic acid (BHA) provides anti-inflammatory effects in rat models of acute gouty arthritis and hyperuricemia. However, the mechanism of action remains to be elucidated. Herein, the anti-inflammatory and antioxidative activities of BHA and the targeted signaling pathways were explored with LPS-induced RAW264.7 and an adjuvant-induced inflammation in a rat model. Results indicated that BHA inhibited the generation of pro-inflammatory cytokines TNFα, IL-1β and IL-6, reduced ROS production and down-regulated JAK1-STAT1/3 signaling pathways in LPS-induced RAW264.7. In vivo, BHA alleviated paw and joint swelling, decreased inflammatory cell infiltration in paw tissues, suppressed gene expressions of p38 and p65, down-regulated the NF-κB and MAPK signaling pathways and reduced protein levels of TNFα, IL-1β and IL-6 in joint tissues of arthritis rats. This study demonstrated the pivotal role of BHA in anti-inflammation and anti-oxidation, suggesting the potential clinical value of BHA in the prevention of inflammatory arthritis and is worthy for development as a new pharmacological treatment. 相似文献
12.
A novel thermo-responsive 2,9(10),16(17),23(24)-tetrakis[(3-carboxyacrylamide) phthalocyaninato] zinc (ZnPc)-g-TiO2-g-poly(N-isopropylacrylamide) (PNIPAM) photocatalyst modified with phthalocyanines was prepared. The photocatalyst exhibited thermo-responsive properties due to the introduction of PNIPAM, which performed recovery for reuse above the lower critical solution temperature (LCST, about 26 °C). ZnPc-g-TiO2-g-PNIPAM effectively expanded the light response range to the visible light region and inhibited the recombination of electron–hole pairs, which enhanced the performance of the photocatalyst. As expected, ZnPc-g-TiO2-g-PNIPAM (0.3 g/L) exhibited excellent photocatalytic performance for the removal of Rhodamine B (RhB, 1.0 × 10−5 mol/L) and methylene blue (MB, 1.0 × 10−5 mol/L) under visible light, which reached 97.2% and 88.6% at 20 °C within 40 min, respectively. Furthermore, the influence of temperature upon photocatalytic performance was also investigated. When the temperature increased from 20 °C to 45 °C, the removal of RhB decreased by approximately 53.8%. The stability of the photocatalyst demonstrated that the photocatalytic activity was still above 80% for the removal of RhB after 3 cycles. Above all, this work provided an intelligent thermally responsive photocatalyst based on phthalocyanine for water purification under visible light. 相似文献
13.
A novel sensing chip was designed for MALDI-MS quantitation of acid phosphatase(ACP).The ACP sensing chip was constructed through non-covalent interaction of streptavidin and biotin for the assembly of biotinylated peptide substrate on biotinylated polyethylene-glycol(PEG)modified indium-tin oxide(ITO)slide.In the presence of ACP,the peptide substrate was dephosphorylated under acidic condition to generate a new mass signal.The quantitative assay of ACP was achieved with the mass signal ratio of product to the sum of product and left peptide substrate.Under optimal detection conditions,the ratio was linearly correlated with the concentration of ACP in the range of 0.05–12 g/L with a detection limit(LOD)of 0.04 g/L.The designed ACP sensing chip has been used to analyze ACP in complex clinical samples,which exhibited high selectivity,good repeatability,and admirably anti-interference ability.This work further demonstrates the concept of MS sensing and the application of MALDI-MS in quantitative analysis,and provides a convenient method for the quantitation of proteases in clinical diagnosis. 相似文献
14.
15.
16.
This paper investigates the scattering effect of
domestic 0.5 at{\%} ceramic Nd:YAG. An effective method has been
utilized to measure the scattering and absorption coefficients.
An end-pumped continuous wave (CW) Nd:YAG ceramic laser was also
demonstrated. A maximum output power of 6.7~W at 1064~nm was
obtained at an 808-nm pump power of 32.9~W. Conversion efficiency
and slope efficiency have been achieved. This indicates that
scattering has an important effect on the optical performance of
ceramic Nd:YAG. 相似文献
17.
We develop a model of CA3 neurons embedded in a resistive array to mimic the effects of electric fields from a new perspective. Effects of DC and sinusoidal electric fields on firing patterns in CA3 neurons are investigated in this study. The firing patterns can be switched from no firing pattern to burst or from burst to fast periodic firing pattern with the increase of DC electric field intensity. It is also found that the firing activities are sensitive to the frequency and amplitude of the sinusoidal electric field. Different phase-locking states and chaotic firing regions are observed in the parameter space of frequency and amplitude. These findings are qualitatively in accordance with the results of relevant experimental and numerical studies. It is implied that the external or endogenous electric field can modulate the neural code in the brain. Furthermore, it is helpful to develop control strategies based on electric fields to control neural diseases such as epilepsy. 相似文献
18.
提出了一种新型的基于串行结构的最小频移键控调制技术,产生了相位连续,频谱宽度窄,每码元时间有两次π/2相移,类似于传统最小频移键控调制信号,给出了该调制方案的理论推导,并将其应用于8进制的多维多阶调制系统中。理论和仿真分析了不同的8进制调制方案在频谱特性,残留色散容限,自相位调制容限的不同,还分析了其受到系统滤波带宽的影响。最后仿真实现了通过350km的色散完全补偿的光纤120Gb/s的数据传输。 相似文献
19.
Hua Nan Yuan-Hong Tao Tian-Jiao Wang Jun Zhang 《International Journal of Theoretical Physics》2016,55(10):4324-4330
The construction of maximally entangled bases for the bipartite system \(\mathbb {C}^{d}\otimes \mathbb {C}^{d}\) is discussed firstly, and some mutually unbiased bases with maximally entangled bases are given, where 2≤d≤5. Moreover, we study a systematic way of constructing mutually unbiased maximally entangled bases for the bipartite system \(\mathbb {C}^{d}\otimes \mathbb {C}^{d^{k}}\). 相似文献
20.
高效液相色谱法同时测定生物质乳酸发酵液中有机酸及糖类化合物 总被引:3,自引:0,他引:3
建立了高效液相色谱(HPLC)同时测定生物质乳酸发酵液中有机酸及糖类的分析方法。使用Bio-Rad Aminex HPX-87H色谱柱,以5 mmol/L的H2SO4为流动相,在柱温55 ℃,流速0.6 mL/min条件下,采用示差折光检测器进行检测。结果表明,该方法可在17 min内实现发酵液中各种有机酸和糖类化合物等的完全分离与定量,6种有机酸和3种糖类化合物在0.15~5.19 g/L范围内的线性关系良好,回归方程的线性相关系数在0.9998以上。将该法用于米根霉发酵液的检测,两个水平的加标回收率为96.91%~103.11%,相对标准偏差(n=6)为0.81%~4.61%。该法适用于微生物发酵液中多种有机酸和糖类的快速、高效分离和定量测定。 相似文献