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991.
用1,4-丁二醇作为络合沉淀剂,通过再结晶活化法将晶型混乱并具有晶格缺陷的纳米级MgCl2晶粒均匀分散在硅胶表面,形成结构化纳米载体.将此载体用于负载TiCl4得到结构化纳米Ziegler-Natta催化剂.研究了醇镁比对载体形貌的影响,以及结构化纳米催化剂用于乙烯聚合的催化特性和产物特点.乙烯淤浆高压聚合结果表明结构化纳米Ziegler-Natta催化剂可用于制备超高分子量聚乙烯,并且温度对催化剂活性和聚乙烯产物的分子量都有很大的影响,在实验条件下催化剂活性可达到1261 kg PE.(molTi)-1.h-1.10-5Pa-1,超高分子量聚乙烯的黏均分子量可达到5.87×106.SEM、DSC和粒径分析等结果表明,结构化纳米催化剂制备的聚乙烯产物结晶度高,在实验考察条件下最高可达到49.5%,而且产物形貌规整,接近球形,平均粒径在68~69μm之间,利于后续的生产加工. 相似文献
992.
18O同位素标记定量肽段串联体蛋白质结合同位素稀释-多反应监测质谱的蛋白质绝对定量新方法 总被引:1,自引:0,他引:1
建立了定量肽段串联体蛋白质(concatamers of Q peptides, QconCATs)结合18O同位素标记-多反应监测质谱的蛋白质绝对定量新方法。首先对QconCAT重组蛋白质进行了纯度表征,十二烷基硫酸钠-聚丙烯酰胺凝胶电泳(SDS-PAGE)表征结果表明重组蛋白质的纯度在99%以上,相对分子质量约为63.4 kDa。对QconCAT重组蛋白质酶切后的肽段混合物进行质谱分析,并经pFind和pLabel软件处理,验证了目标肽段。还考察了QconCAT重组蛋白质的酶切效率和18O标记效率,并对QconCAT蛋白质结合18O标记-同位素稀释-多反应监测质谱方法进行了评价。实验结果表明,采用该方法对腾冲嗜热厌氧菌(Thermoanaerobacter tengcongensis, TTE)中选定蛋白质的肽段进行绝对含量测定时,相对标准偏差小于20%,准确度较高,说明该方法可用于复杂生物样本中蛋白质的绝对定量。更重要的是所建方法不仅解决了细胞培养氨基酸稳定同位素标记(SILAC)技术的重标试剂价格昂贵的问题,也为定量蛋白质组学提供了一种新的方法。 相似文献
993.
研究一维有界区间上粘性依赖于密度且具有奇性、初始允许真空的可压缩非牛顿流.通过正则化奇性项以及逐步迭代构造初边值问题的逼近解,对逼近解取极限得到其局部强解的存在唯一性,进一步推广了相关文献中关于非牛顿流解的存在性结果. 相似文献
994.
Ya‐Chu Hsieh Hau‐Yu Fang Yi‐Ting Chen Rong Yang Chen‐I Yang Pi‐Tai Chou Ming‐Yu Kuo Yao‐Ting Wu 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2015,127(10):3112-3116
The syntheses, structures, and physical properties of dibenzozethrenes were explored. The results thus obtained were compared with those for zethrenes. Dibenzozethrenes were synthesized by the nickel‐catalyzed cyclodimerization of 9‐ethynyl‐1‐iodoanthracenes. The substituents in zethrene and dibenzozethrene twisted their backbones, and remarkably influenced their properties. Unlike closed‐shell disubstituted derivatives, the parent zethrene and dibenzozethrene are singlet open‐shell biradicals, which were studied by variable‐temperature 1H NMR, ESR, SQUID and computational methods. Since substituents were observed to affect significantly the biradical properties, the relevant mechanisms were analyzed. The nonlinear optical performance of each of these compounds depends on its π‐conjugation and biradical properties. Dibenzozethrenes have larger two‐photon absorption cross‐sections than zethrenes, as most strongly evidenced by the parent dibenzothrene [σmax=4323 GM at 530 nm]. 相似文献
995.
The organocatalytic sulfenylation of α-nitroesters mediated by diaryl-l-prolinols was developed. A range of α-sulfenylated α-nitroesters were obtained in good yields with moderate to good enantioselectivities. 相似文献
996.
Benren Liao Libo Ruan Min Shi Nian LiLiang Chang Leping LiuFan Yang Jie Tang 《Tetrahedron letters》2014
An efficient method for preparation of 3-formyl-2-arylbenzo[b]furan derivatives 4 from 3-chloro-2-(2-methoxyaryl)-1-arylprop-2-en-1-one 2 was developed, and the desired product was obtained in good to excellent yields. By converting 2-(2-methoxyphenyl)-3-oxo-3-phenylpropanal 1 to 2, the regioselectivity problem occurring in the reaction when using 1 as the starting material was successfully avoided. Furthermore, a one-pot procedure for the successive demethylation, cyclization, and hydrolysis was evolved, although the intermediate 3-(dibromomethyl)-2-phenylbenzo[b]furan 3a could be isolated. A plausible mechanism was proposed based on some in situ investigations. 相似文献
997.
An expeditious cascade protocol for the synthesis of functionalized imidazo[1,2-a]pyridin-3-ols was developed based on the Petasis reaction. With the availability of commercial reagents and high efficiency in expanding molecule diversity, this methodology is superior to the existing procedures for the synthesis of imidazo-pyridin-3-ol analogues. 相似文献
998.
Shi-Ji Xiao Xin-Xiang Lei Bing Xia Dan-Qing Xu Hong-Ping Xiao Hong-Xi Xu Fang Chen Li-Sheng Ding Yan Zhou 《Tetrahedron letters》2014
Two novel lignans, gymnothespirolignans A (1) and B (2), possessing a rare polycyclic spiro skeleton, were isolated from the endemic plant of Gymnotheca involucrata Pei. Their structures were determined by spectroscopic evidences and the absolute configurations were confirmed by single crystal X-ray diffraction analysis. Compounds 1 and 2 showed promising antiviral activities against RSV with an IC50 value of 31.87 and 17.51 μM, respectively. 相似文献
999.
Yulin He Weina Zhou Xiangcheng Wang Baoliang Bao Guojian Zhang Cheng Wang Chunmei Wang Xuemei Wang Wei Fang 《Journal of Radioanalytical and Nuclear Chemistry》2014,301(2):469-474
In this study, we synthesized and characterized N-[11C]methyl-dopamine ([11C]MDA) for cardiac sympathetic nerve imaging. [11C]MDA was synthesized by direct N-methylation of dopamine with [11C]methyl iodide and purified by semi-preparation reverse high pressure liquid chromatography (HPLC). The total synthesis time was 45 min including HPLC purification. The radiochemical yields of [11C]MDA was 20 ± 3 %, without decay correction. The radiochemical purity was >98 % and the specific activity was about 50 GBq/mmol. The biological properties of [11C]MDA were evaluated by biodistribution study in normal mice. PET imaging was performed in healthy Chinese mini-swines. Biodistribution study showed that [11C]MDA had high myocardium uptake. PET/CT imaging showed [11C]MDA had clear and symmetrical myocardium uptake, which was blocked obviously by injecting imipramine hydrochloride. [11C]MDA would be a promising candidate of radiotracer for cardiac sympathetic nervous system imaging. 相似文献
1000.
TiO2 nanotube arrays prepared by anodization as an adsorbent in micro‐solid‐phase extraction to preconcentrate and determine nitrogen‐containing polycyclic aromatic hydrocarbons in water samples 下载免费PDF全文
In this study, a simultaneous determination method for nitrogen‐containing polycyclic aromatic hydrocarbons including 7‐methylquinoline, acridine, 5,6‐benzoquinoline, carbazole, and 9‐methylcarbazole was developed. This method is based on a micro‐solid phase extraction using TiO2 nanotube arrays as an adsorbent in combination with HPLC. Some factors that had an effect on the enrichment were optimized, such as sample pH, surfactant concentration, ion strength, type of eluent, equilibrium time, and desorption time. Under the optimized conditions, the linear ranges and LODs were in the range of 0.01–100 and 0.0035–0.81 μg/L, respectively. The precisions of the proposed method were <9.51% (RSD, n = 6). The developed method was validated with four real samples, and the spiked recoveries were in the range of 77–109.6%. All these results demonstrated that this novel micro‐solid‐phase extraction technique was a reliable alternative to conventional preconcentration method for the extraction and analysis of such nitrogen‐containing polycyclic aromatic hydrocarbons in complex samples. 相似文献