全文获取类型
收费全文 | 969篇 |
免费 | 36篇 |
国内免费 | 17篇 |
专业分类
化学 | 747篇 |
晶体学 | 19篇 |
力学 | 26篇 |
数学 | 41篇 |
物理学 | 189篇 |
出版年
2024年 | 2篇 |
2023年 | 9篇 |
2022年 | 17篇 |
2021年 | 102篇 |
2020年 | 39篇 |
2019年 | 39篇 |
2018年 | 60篇 |
2017年 | 35篇 |
2016年 | 64篇 |
2015年 | 52篇 |
2014年 | 64篇 |
2013年 | 69篇 |
2012年 | 108篇 |
2011年 | 104篇 |
2010年 | 64篇 |
2009年 | 36篇 |
2008年 | 25篇 |
2007年 | 24篇 |
2006年 | 17篇 |
2005年 | 18篇 |
2004年 | 8篇 |
2003年 | 10篇 |
2002年 | 8篇 |
2001年 | 4篇 |
2000年 | 4篇 |
1999年 | 3篇 |
1997年 | 2篇 |
1994年 | 5篇 |
1993年 | 4篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1987年 | 3篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1981年 | 1篇 |
1980年 | 3篇 |
1977年 | 1篇 |
1975年 | 2篇 |
1936年 | 1篇 |
1935年 | 1篇 |
1933年 | 1篇 |
排序方式: 共有1022条查询结果,搜索用时 312 毫秒
1.
2.
Umie F.M. Haziz Rosenani A. Haque Shun-Ze Zhan Hassan H. Abdallah Mohd R. Razali 《应用有机金属化学》2020,34(10):e5818
The synthesis and characterizations for a series of dinuclear gold (I)-di-NHC complexes, 1–8 through the trans-metalation method of their respective silver (I)-di-NHC complexes, i–viii are reported (where NHC = N-heterocyclic carbene). The successful complexation of a series of unusual non-symmetrical and symmetrical di-NHC ligands, 3,3'-(ethane-1,2-diyl)-1-alkylbenzimidazolium-1'-butylbenzimidazolium (with alkyl = methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, benzyl) with the gold (I) ions are suggested by elemental analysis, Fourier transform-infrared, 1H- and 13C-NMR data. The 13C-NMR spectra of 1–8 show a singlet sharp peak in the range of 190.00–192.00 ppm, indicating the presence of a carbene carbon that bonded to the gold (I) ion. From single crystal X-ray diffraction data, the structure of complex 6 with the formula of [di-NHC-Au (I)]2·2PF6 is obtained [where NHC = 3,3'-(ethane-1,2-diyl)-1-hexylbenzimidazolium-1'-butylbenzimidazolium]. The photophysical study in solid state of 6 displays an intense photoluminescence with a strong emission maxima, λem = 480 nm, upon excitation at 340 nm at room temperature. Interestingly, the emission maximum at 77 K shows a structural character with a strong peak at 410 nm, a medium at 433 nm and a weak at 387 nm, accompanied by a tail band to about 500 nm. 相似文献
3.
Mat Rasol Awang Hassan Hamdani Mutaat Mohd. Shukri Mahmud Wan Badrin Wan Husain Tajuddin Osman Khomsaton Abu Bakar Asmahwati Kassim Zal U''yun Wan Mahmud Ishak ManafTamikazu Kume Shoji Hashimoto 《Radiation Physics and Chemistry》1993,42(4-6):611-616
In solid state fermentation, Pleurotus sajor-caju has been found to be able to degrade at least 30% oil palm empty Fruit Bunch (EFB) fibre leaving 70 % useful materials. Conditions under which fermentation carried out were investigated. It was found that, in the temperature range between 25– 28 °C, relative ph between 6–8, moisture between 60–70 % and medium composition of CaCO3: rice bran 2 %: 5 % were the optimum conditions. The results showed in fermented products that, there were substantial reduction in cellulosic component such as Crude Fiber (CF, 18 %); Acid Detergent Fibre (ADF, 45 %), Neutral Detergent Fibre (NDF, 61 %) and Acid Detergent Lignin (ADL, 14 %). However, Crude Protein (CP, 10%) increased resulted from single cell protein enrichment of mycelial microbial mass. The mass reductions of substrate in fermentation process corresponds to the CO2 released during fermentation. Hence, attributable to the decreased in content of CF, ADF, NDF, and ADL. The digestibility study has also been carried out to determine the useful level of this product to ruminant. Aflatoxin content was detected low in both the initial substrates and products. Based on nutritional value and low content of aflatoxin, the product is useful as a source of roughage to ruminant. 相似文献
4.
Sulaiman Wadi Harun Nizam Tamchek Mohd Kamil Abd-Rahman Prabakaran Poopalan Harith Ahmad 《Optical Review》2003,10(3):133-135
A multiwavelength Brillouin/erbium fibre laser (BEFL) which operates in the long wavelength (L-band) region is demonstrated for potential applications in an L-band wavelength division multiplexing (WDM) communication system. The laser configuration consists of a long erbium-doped fibre to enable L-band amplification where two 3-dB couplers take a portion of the generated BEFL signal and re-inject it into the single mode fibre to seed a cascaded BEFL line in the same direction as the first BEFL line. A stable and strong laser comb of up to five lines with 10-GHz spacing has been obtained with a Brillouin pump (BP) of 9.2 mW and a 980 nm pump of 92 mW. The BEFL has shown a broad tuning range with a tuning characteristic for line #1 which is flat over a range greater than 9.9 nm. 相似文献
5.
6.
Norimah Yusof A.H. Ainul Hafiza Rozaini M. Zohdi Md Zuki A. Bakar 《Radiation Physics and Chemistry》2007,76(11-12):1767-1770
Radiation at 25 and 50 kGy showed no effect on the acidic pH of the local honey, Gelam, and its antimicrobial property against Staphylococcus aureus but significantly reduced the viscosity. Honey stored up to 2 years at room temperature retained all the properties studied. Radiation sterilized Gelam honey significantly stimulated the rate of burn wound healing in Sprague-Dawley rats as demonstrated by the increased rate of wound contraction and gross appearance. Gelam honey attenuates wound inflammation; and re-epithelialization was well advanced compared to the treatment using silver sulphadiazine (SSD) cream. To enhance further the use of honey in wound treatment and for easy handling, Gelam honey was incorporated into our hydrogel dressing formulation, which was then cross-linked and sterilized using electron beam at 25 kGy. Hydrogel with 6% of honey was selected based on the physical appearance. 相似文献
7.
A total of seven pesticides and eight alkylphenols were monitored using this method for the determination of their trace levels in human cord blood. The pesticides are lindane, diazinon, α-endosulfan, β-endosulfan, endosulfan sulfate, chlorpyrifos and endrin; while the alkylphenols are 4-n-butylphenol, 4-n-pentylphenol, 4-n-hexylphenol, 4-t-octylphenol, 4-n-heptylphenol, nonylphenol, 4-n-octylphenol and bisphenol A. The pesticides and alkylphenols in the cord blood samples were extracted with solid phase extraction IST C18 cartridges and analyzed by selected ion monitoring mode using quadrapole detector in Shimadzu QP-5000 gas chromatograph-mass spectrometer. Trace levels of pesticide and alkylphenols in the range of non-detectable to 15.17 ng ml−1, were detected in the human cord blood samples. This technique of monitoring the levels of endocrine-disruptors in blood samples is consistent, reliable and cost effective while reducing wastage of time and solvents. 相似文献
8.
Syntheses of steroidal heterocycles containing a five-membered N,S- heterocycle attached at the 6,7 positions of the B ring are reported. 5Alpha-cholestane-6-one (1), its 3beta-acetoxy- (2) and 3beta-chloro- (3) analogues reacted with semicarbazide and aqueous sodium acetate in refluxing ethanol to yield 5alpha-cholestan-6-one-semicarbazone 1a and its 3-beta-acetoxy and 3beta-chloro derivatives 2a and 3a, respectively. The reactions of 1a, 2a and 3a with thionyl chloride in dichloromethane at low temperature afforded the cyclized thiadiazole 4 and its 3beta-acetoxy- and 3beta-chloro analogues 5 and 6 in good yields. 相似文献
9.
W. M. Z. Wan Yunus A. B. Salleh A. Ismail K. Ampon C. N. A. Razak M. Basri 《Applied biochemistry and biotechnology》1992,36(2):97-105
Poly(methyl methacrylate) (PMMA) was found to be suitable for the immobilization of lipase fromCandida rugosa. The best result based on hydrolytic activity was obtained by adsorption of the purified unbuffered enzyme solution onto PMMA beads without any modification of the beads. Prolonged exposure of the protein to the beads increased its adsorption but the expressed activity decreased after 1 h of exposure. The magnitude of the immobilized activity also varied with the size of the beads. Immobilization of the lipase shifted its optimal reaction temperature from 37 to 45°C. The immobilized enzyme is also more stable than the free enzyme in solution. The operational half-life of the immobilized lipase packed in a column and assayed in a closed system is 40 d. 相似文献
10.
A
modulated dsc study on the in situ polymerization of cyclic butylene terephthalate
oligomers 总被引:1,自引:0,他引:1
Z. A. Mohd Ishak P. P. Shang J. Karger-Kocsis 《Journal of Thermal Analysis and Calorimetry》2006,84(3):637-641
The polymerization of a cyclic butylene terephthalate
(CBT) oligomer was studied as a function of temperature (T=200
and 260°C, respectively) by modulated DSC (MDSC). The first heating was
followed by cooling after various holding times (5, 15 and 30 min) prior to
the second heating which ended always at T=260°C.
This allowed us to study the crystallization and melting behavior of the resulting
polybutylene terephthalate (PBT), as well. In contrary to the usual belief,
the CBT polymerization is exothermic and the related process is superimposed
to that of the CBT melting. The melting behavior of the PBT was affected by
the polymerization mode (performed below or above the melting temperature
of the PBT product) of the CBT. Annealing above the melting temperature of
PBT yielded a product featuring double melting. This was attributed to the
presence of crystallites with different degrees of perfection. The crystals
perfection which occurred via recrystallization/remelting was manifested by
a pronounced exothermic peak in the non-reversing trace. 相似文献