全文获取类型
收费全文 | 2032篇 |
免费 | 317篇 |
国内免费 | 157篇 |
专业分类
化学 | 1381篇 |
晶体学 | 25篇 |
力学 | 147篇 |
综合类 | 13篇 |
数学 | 176篇 |
物理学 | 764篇 |
出版年
2024年 | 7篇 |
2023年 | 35篇 |
2022年 | 80篇 |
2021年 | 86篇 |
2020年 | 73篇 |
2019年 | 60篇 |
2018年 | 76篇 |
2017年 | 67篇 |
2016年 | 98篇 |
2015年 | 116篇 |
2014年 | 125篇 |
2013年 | 165篇 |
2012年 | 191篇 |
2011年 | 201篇 |
2010年 | 114篇 |
2009年 | 123篇 |
2008年 | 128篇 |
2007年 | 122篇 |
2006年 | 103篇 |
2005年 | 77篇 |
2004年 | 41篇 |
2003年 | 33篇 |
2002年 | 36篇 |
2001年 | 33篇 |
2000年 | 37篇 |
1999年 | 35篇 |
1998年 | 25篇 |
1997年 | 29篇 |
1996年 | 34篇 |
1995年 | 15篇 |
1994年 | 18篇 |
1993年 | 12篇 |
1992年 | 7篇 |
1991年 | 15篇 |
1990年 | 24篇 |
1989年 | 16篇 |
1988年 | 11篇 |
1987年 | 11篇 |
1986年 | 7篇 |
1985年 | 2篇 |
1981年 | 2篇 |
1976年 | 2篇 |
1957年 | 1篇 |
1942年 | 1篇 |
1941年 | 1篇 |
1936年 | 4篇 |
1930年 | 2篇 |
1929年 | 1篇 |
1927年 | 1篇 |
1923年 | 1篇 |
排序方式: 共有2506条查询结果,搜索用时 11 毫秒
71.
建立了戊四硝酯粉含量及有关物质的RP-HPLC测定法。采用ODS色谱柱,甲醇/水(70∶30)为流动相,使戊四硝酯与有关物质基线分离,二极管阵列检测器检测波长206nm。本方法操作简便,重现性好。 相似文献
72.
反相高效液相色谱/电喷雾质谱法测定血浆中盐酸舍曲林 总被引:1,自引:0,他引:1
采用反相高效液相色谱-电喷雾质谱法(LC-ESI/MS)测定人体血浆中盐酸舍曲林。以盐酸丙咪嗪为内标,按内标法定量。血浆样品经pH 10.00碳酸钠溶液碱化,加入甲基叔丁基醚萃取,离心分离,取上清液吹干,用流动相溶解进样。色谱柱:RP-Extend-C18(150 mm×4.6 mm,5μm),柱温:40℃;流动相:pH 3.00的三氟乙酸溶液-甲醇(40∶60,V/V),流速0.6 mL/m in。质谱采用选择离子监控模式,检测离子的核质比(m/z)分别是281(丙咪嗪)和159(舍曲林)。舍曲林和丙咪嗪的保留时间分别是5.4 m in和3.8 m in;舍曲林标准曲线线性范围为1~80μg/L;检出限为1.0μg/L(S/N>10);日间、日内相对标准差均小于6.0%,相对回收率为90%~106%;提取回收率在75%~93%范围内。此法适合人体药代动力学的血浆样品的分析,结果准确、可靠。 相似文献
73.
Zhao Wei Xinlei Zhang Huifang Nie Lin Yao Yanqin Liu Zhibing Zheng Qin Ouyang 《Molecules (Basel, Switzerland)》2022,27(3)
A family of novel efficient non-oxime compounds exhibited promising reactivation efficacy for VX and sarin inhibited human acetylcholinesterase was discovered. It was found that aromatic groups coupled to Mannich phenols and the introduction of imidazole to the ortho position of phenols would dramatically enhance reactivation efficiency. Moreover, the in vivo experiment was conducted, and the results demonstrated that Mannich phenol L10R1 (30 mg/kg, ip) could afford 100% 48 h survival for mice of 2*LD50 sarin exposure, which is promising for the development of non-oxime reactivators with central efficiency. 相似文献
74.
75.
A rapid and nondestructive near infrared (NIR) method combined with chemometrics was used to discriminate Ganoderma lucidum according to cultivation area. Raw, first, and second derivative NIR spectra were compared to develop a robust classification rule. The chemical properties of G. lucidum samples were also investigated to find out the difference between samples from six varied origins. It could be found that the amount of polysaccharides and triterpenoid saponins in G. lucidum samples was considerably different based on cultivation area. These differences make NIR spectroscopic method viable. Principal component analysis (PCA), discriminant partial least-squares (DPLS) and discriminant analysis (DA) were applied to classify the geographical origins of those samples. The results showed that excellent classification could be obtained after optimizing spectral pre-treatment. For the discriminating of samples from three different provinces, DPLS provided 100% correct classifications. Moreover, for samples from six different locations, the correct classifications of the calibration as well as the validation data set were 96.6% using the DA method after the SNV first derivative spectral pre-treatment. Overall, NIR diffuse reflectance spectroscopy using pattern recognition was shown to have significant potential as a rapid and accurate method for the identification of herbal medicines. 相似文献
76.
77.
Zhang Z Wang J Tu Q Nie N Sha J Liu W Liu R Zhang Y Wang J 《Colloids and surfaces. B, Biointerfaces》2011,88(1):85-92
The current paper reports the synthesis of a highly hydrophilic, antifouling dendronized poly(3,4,5-tris(2-(2-(2-hydroxylethoxy)ethoxy)ethoxy)benzyl methacrylate) (PolyPEG) brush using surface initiated atom transfer radical polymerization (SI-ATRP) on PDMS substrates. The PDMS substrates were first oxidized in H2SO4/H2O2 solution to transform the Si-CH3 groups on their surfaces into Si-OH groups. Subsequently, a surface initiator for ATRP was immobilized onto the PDMS surface, and PolyPEG was finally grafted onto the PDMS surface via copper-mediated ATRP. Various characterization techniques, including contact angle measurements, attenuated total reflection infrared spectroscopy, and X-ray photoelectron spectroscopy, were used to ascertain the successful grafting of the PolyPEG brush onto the PDMS surface. Furthermore, the wettability and stability of the PDMS-PolyPEG surface were examined by contact angle measurements. Anti-adhesion properties were investigated via protein adsorption, as well as bacterial and cell adhesion studies. The results suggest that the PDMS-PolyPEG surface exhibited durable wettability and stability, as well as significantly anti-adhesion properties, compared with native PDMS surfaces. Additionally, our results present possible uses for the PDMS-PolyPEG surface as adhesion barriers and anti-fouling or functional surfaces in biomedical applications. 相似文献
78.
One-pot synthesis of porous polymer monolith decorated with N-methylimidazolium in a capillary was described. The polymer matrix was synthesized by in situ copolymerization and quaterization of 3-chloro-2-hydroxylpropyl methacrylate (CHPMA), ethylene dimethacrylate (EDMA), and N-methylimidazole (N-MIz). The influencing factors including amount of cross-linkers, composition of porogenic solvents, and polymerization temperature on the formation of the monolithic column were investigated. The monolithic column exhibited high column efficiency for thiourea, up to 135 000 plates per meter, and phenylmethanol, up to 102 000 plates per meter. Different types of compounds including alkylbenzenes, phenols, and inorganic anions were successfully baseline separated by capillary electrochromatography (CEC). The separation of theses analytes on the column indicated typical reversed-phase and anion-exchange chromatographic retention mechanism. 相似文献
79.
Qing Zhang Liangbiao Fan Qiaomei Lu Xiaozhang Yu Meina Liang Jinfang Nie Ningjie Li Lan Zhang 《Journal of separation science》2019,42(16):2687-2695
As signal molecules, auxins play an important role in mediating plant growth. Due to serious interfering substances in plants, it is difficult to accurately detect auxins with traditional solid‐phase extraction methods. To improve the selectivity of sample pretreatment, a novel molecularly imprinted polymer ‐coated solid‐phase microextraction fiber, which could be coupled directly to high‐performance liquid chromatography, was prepared with indole acetic acid as template molecule for the selective extraction of auxins. The factors influencing the polymer formation, such as polymerization solvent, cross‐linker, and polymerization time, were investigated in detail to enhance the performance of indole acetic acid‐molecularly imprinted polymer coating. The morphological and chemical stability of this molecularly imprinted polymer‐coated fiber was characterized by scanning electron microscopy, infrared spectrometry, and thermal analysis. The extraction capacity of the molecularly imprinted polymer‐coated solid‐phase microextraction fiber was evaluated for the selective extraction of indole acetic acid and indole‐3‐pyruvic acid followed by high‐performance liquid chromatography analysis. The linear range for indole acetic acid and indole‐3‐pyruvic acid was 1–100 µg/L and their detection limit was 0.5 µg/L. The method was applied to the simultaneous determination of two auxins in two kinds of tobacco (Nicotiana tabacum L and Nicotiana rustica L) samples, with recoveries range from 82.1 to 120.6%. 相似文献
80.
The LB-DF/FD method derived from the Lattice Boltzmann Method and direct forcing/fictitious domain method is used to numerically investigate the dynamics and interaction of two elliptical particles settling in an infinitely long channel. One particle (EP0) is initially kept horizontal (major axis perpendicular to sedimentation) for all simulations while the other's (EP1) orientation is varied. It is found that if EP1strays away from horizontality, the particles undergo transitions from a steady state to reach a chaotic state. Furthermore, there are two distinct chaotic states for the particle motion when EP1 orientation is varied, in which a turning point is observed to distinguish the two states. 相似文献