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991.
Yuqin Yao Zhihui Cheng Haoyu Ye Yongmei Xie Jing He Minghai Tang Tao Shen Jiangman Wang Yan Zhou Zejun Lu Feng Luo Lijuan Chen Luoting Yu Jin‐Liang Yang Aihua Peng Yuquan Wei 《Journal of separation science》2010,33(9):1331-1337
Ansamitocin P‐3 is a potent anti‐tumor maytansinoid found in Actinosynnema pretiosum. However, due to the complexity of the fermentation broth of Actinomycete, how to effectively separate ansamitocin P‐3 is still a challenge. In this study, both analytical and preparative high‐performance counter‐current chromatography were successfully used to separate and purify ansamitocin P‐3 from fermentation broth. A total of 28.8 mg ansamitocin P‐3 with purity of 98.4% was separated from 160 mg crude sample of fermentation broth in less than 80 min with the two‐phase solvent system of hexane–ethyl acetate–methanol–water (0.6:1:0.6:1, v/v/v/v). The purity and structural identification were determined by HPLC, 1H NMR, 13C NMR and mass spectroscopy. 相似文献
992.
Xiao‐Chi Ma Xiulan Xin Bao‐jing Zhang Sha Deng Ji‐hong Yao Chang‐yuan Wang Jian Cui Yan Tian Ke‐xin Liu 《Journal of separation science》2010,33(15):2272-2277
An efficient separation method of using high‐speed counter‐current chromatography was successfully established to directly purify cytotoxic transformed products of cinobufagin by Cordyceps militaris. The two‐phase solvent system composed of n‐hexane–ethyl acetate–methanol–water (4:6:3:4, v/v) was used in high‐speed counter‐current chromatography. A total of 9 mg of 4β,12α‐dihydroxyl‐cinobufagin ( 1 ), 15 mg of 12β‐hydroxyl‐cinobufagin ( 2 ), 8 mg of 5β‐hydroxyl‐cinobufagin ( 3 ), 12 mg of deacetylcinobufagin ( 4 ) and 6 mg of 3‐keto‐cinobufagin ( 5 ) were obtained in a one‐step separation from 400 mg of the crude extract with purity of 98.7, 97.2, 90.6, 99.1 and 99.4%, respectively, as determined by HPLC. Their chemical structures were identified on the basis of 1H‐NMR and 13C‐NMR technology. All products ( 1 – 5 ) showed the potent activities against human carcinoma cervicis (Hela) and malignant melanoma (A375) cells in vitro. 相似文献
993.
The complexation of lysozyme and sodium (sulfamate carboxylate) isoprene/ethylene oxide (SCIEO) at pH = 7.4 and the release of lysozyme from the complexes in the presence of NaCl were investigated. Through electrostatic and hydrophobic interactions, lysozyme and SCIEO form stable complex nanoparticles. The complexation partially disturbs the structure of lysozyme. Some of the hydrophobic residues of lysozyme are exposed to bind with SCIEO. The complexation leads to loss of most of the lysozyme activity. In the presence of NaCl, lysozyme can be released from the complexes. The released lysozyme molecules recover their native structure and activity completely. In the condition of physiological pH and ionic strength, a sustained and extended release of lysozyme was achieved.
994.
Seydou Yao Giancarlo DellaVentura Cyril Petibois 《Analytical and bioanalytical chemistry》2010,397(6):2079-2089
Asbestos is a fiber causing lung diseases such as asbestosis and mesothelioma. Although the process involving these diseases
remains to be elucidated for developing drugs and treatments, direct consequences of fiber exposure in humans have been clearly
demonstrated. These diseases are first characterized by histological heterogeneity and combine chronic inflammation with fibrosis
and cellular alterations. As a consequence, asbestosis is usually diagnosed at advanced stages of the disease and treatments
are usually inefficient to cure the patients. Here, we review the links established between asbestos fiber chemistry and morphology
with the occurrence of associated lung diseases. Cytological and histological aspects of diseases are described with respect
to current analytical capabilities, notably for microscopy techniques. 相似文献
995.
A new photochromic diarylethene (1a) has been prepared. Both its photochromic behavior and nonlinear optical properties are
investigated. 1a shows excellent ring-opening (λmax = 386 nm) and ring-closing (λmax = 652 nm) photoisomerization with UV-Vis light irradiation. With 800 nm femtosecond pulsed laser irradiation, 1a shows two-photon-induced
photoisomerization, and a two-photon absorption cross-section (σ = 423×1050 cm4·s per photon) is obtained by using two-photon induced fluorescence method. The applications of two-photon absorption of 1a
to holographic recording has been also investigated. A two-photon induced micro-pattern is recorded on the diarylethene 1a-PMMA
film with an femtosecond laser of 800 nm, 100 fs, 1 kHz, 50 mW. 相似文献
996.
A new unsymmetrical photochromic diarylethene, namely1-[2-methyl-5-(p-N,N-dimethylaminophenyl)-3-thienyl]-2-[2-methyl-5-(3-methoxylphenyl)-3-thienyl]
perfluorocyclopentene (1a), was synthesized. The compound showed good photochromism, high sensitivity and remarkable fatigue-resistance
both in solution and in poly(methyl methacrylate) (PMMA) matrix with UV/Vis light irradiation. The absorption maximum of its
closed-ring isomer was observed at 624 nm in PMMA amorphous film. It is a nice match for the wavelength of the recording laser
(633 nm). Using this target compound as recording medium, four types of polarization holographic optical recordings were performed
successfully using a He-Ne laser. The results showed that only the orthogonal circular polarization recording could obtain
a hologram with high diffraction efficiency and high signal-to noise-ratio. With multiplexing recording technology, three
types of polarization multiplexing holographic optical recordings, including angular multiplexing, polarization multiplexing,
and angular plus polarization multiplexing holographic recording, were also carried out perfectly based on its photoinduced
anisotropic phenomenon accompanying the photochromic reaction by photoirradiation. The results demonstrate that the multiplexing
recording technology is an effective method to improve recording capacity when using diarylethene 1 as recording medium. 相似文献
997.
A high molecular weight aromatic homopoly(ester‐imide) (homoPEI) was synthesized from homopoly(ester‐amic acids) (homoPEAA), which was obtained from the reaction of bis(trimellitic acid anhydride) phenyl ester (BTAH) with 4‐4'‐oxydianiline ether (ODA). This homoPEI was melt‐processable semi‐crystalline polymer and displayed dual endothermic transitions which were attributed to the different levels of crystal perfection and size in the crystal structures. Four high molecular weight aromatic copoly(ester‐imide)s (coPEIs) were synthesized via copoly(ester‐amic acids)s (coPEAA) from the reaction of 4, 4'‐oxydiphthalic anhydride (ODPA) and BTAH with ODA. The molar percentage of BTAH varied from 10 to 40%. When the molar percentages of BTAH were 30 and 40%, the resulting two coPEIs were crystallinable and their melting temperatures were 361°C and 356/371°C, respectively. Differential scanning calorimetry (DSC) and wide angle X‐ray diffraction (WAXD) results indicated that the crystal structures included short segments of BTAH/ODA and ODPA/ODA. The initial crystallization of the two coPEIs took place during imidization process. Thermogravimetric (TA) and mechanical analysis confirmed that both homoPEI and coPEIs showed almost no weight loss until 400°C in N2 and good mechanical properties. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
998.
A colorimetric strategy based on conjugated polyelectrolyte aggregates has been applied to determine and distinguish anionic, cationic and non-ionic surfactants. 相似文献
999.
This paper reports the synthesis of a perylene-bridged bis(crown ether) through the condensation reaction between primary amine-armed dibenzo-24-crown-8 and 3,4,9,10-perylenetetracarboxylic dianhydride. Pseudorotaxane with a perylene moiety at the wheel and a fullerene unit in the middle of the axle was prepared, which was evidenced by 1H NMR and fluorescence experiments. Subsequent investigations show that the formation and disassociation of the pseudorotaxane can be controlled by the alternating addition of KPF6 and 18-crown-6, following the change of the florescence intensity of perylene.
相似文献1000.
The syntheses and reactivity of the two N‐heterocyclic carbene (NHC)→ silylene complexes 2 and 4 have been investigated. The latter are easily accessible by reaction of the zwitterionic, N‐heterocyclic silylene LSi: 1 [L=Ar‐N‐C(=CH2)CH?C(Me)‐N‐Ar, Ar=2,6‐iPr2C6H3] with 1,3,4,5‐tetramethylimidazol‐2‐ylidene and 1,3‐diisopropyl‐4,5‐dimethylimidazol‐2‐ylidene, respectively. While compound 2 undergoes facile rearrangement above ?20 °C to give the unsymmetrical N‐heterocyclic silylcarbene 3 , the derivative 4 remains unchanged even after boiling in benzene. The remarkable reactivity of 3 and 4 towards cyclohexylisocyanide has been examined which leads in a unique series of C? H, Si? H, and C? N bond activations to the new triaminosilanes 5 and 6 , respectively. The novel compounds 3 , 4 , 5 , and 6 were fully characterized by 1H, 13C, and 29Si NMR spectroscopy, EI‐MS, elemental analysis, and single‐crystal X‐ray diffraction. 相似文献