全文获取类型
收费全文 | 4574篇 |
免费 | 295篇 |
国内免费 | 1111篇 |
专业分类
化学 | 5209篇 |
晶体学 | 16篇 |
力学 | 154篇 |
综合类 | 48篇 |
数学 | 65篇 |
物理学 | 488篇 |
出版年
2024年 | 21篇 |
2023年 | 54篇 |
2022年 | 166篇 |
2021年 | 188篇 |
2020年 | 202篇 |
2019年 | 141篇 |
2018年 | 118篇 |
2017年 | 143篇 |
2016年 | 188篇 |
2015年 | 159篇 |
2014年 | 177篇 |
2013年 | 300篇 |
2012年 | 330篇 |
2011年 | 221篇 |
2010年 | 238篇 |
2009年 | 314篇 |
2008年 | 439篇 |
2007年 | 277篇 |
2006年 | 309篇 |
2005年 | 277篇 |
2004年 | 234篇 |
2003年 | 198篇 |
2002年 | 144篇 |
2001年 | 132篇 |
2000年 | 143篇 |
1999年 | 109篇 |
1998年 | 106篇 |
1997年 | 107篇 |
1996年 | 103篇 |
1995年 | 85篇 |
1994年 | 84篇 |
1993年 | 85篇 |
1992年 | 51篇 |
1991年 | 33篇 |
1990年 | 23篇 |
1989年 | 22篇 |
1988年 | 15篇 |
1987年 | 16篇 |
1986年 | 10篇 |
1985年 | 3篇 |
1984年 | 4篇 |
1983年 | 1篇 |
1982年 | 3篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1976年 | 2篇 |
1971年 | 1篇 |
排序方式: 共有5980条查询结果,搜索用时 15 毫秒
71.
In this study porous glass fiber membranes were modified by reaction with octadecyl-trichlorosilane to form C18 hydrophobic membranes. The contact angle and the CH2 vibration bands at 2855 and 2920 cm(-1) found by FTIR measurements verified the successful immobilization of C18 groups on the glass fiber membranes. The resulting C18 hydrophobic membranes were used to adsorb terpene lactones from crude Ginkgo biloba L. extracts. In batch adsorption processes, the modified C18 membranes exhibited a better adsorption performance than commercial C18 solid phase extraction adsorbents. Different desorption solvents were tested and ethyl acetate was found to preferentially desorb terpene lactones from the modified C18 membranes. In flow adsorption experiments at 1 mL/min, terpene lactone contents higher than 6 wt% (the standardized content) could be achieved in the elution step using ethyl acetate. 相似文献
72.
Zhen-zhong Yang 《高分子科学》2007,(2):137-143
In this review, our recent work in phase inversion emulsification (PIE) for polymer (especially epoxy resin) waterborne dispersions is summarized. Based on experimental results about PIE process, the physical model is proposed which can guide the synthesis of the waterborne dispersions such as polymer/nanoparticle composite dispersion. In the presence of a latent curing catalyst, PIE can give a crosslinkable epoxy resin waterborne dispersion. The dispersions can form cured transparent coatings with some unique properties such as UV shielding. They are promising in functional coatings, waterborne resin matrices for composites, and sizing for high performance fibers. 相似文献
73.
以双[对-酰氯苯基]二甲基硅烷和酚酞、四溴酚酞以及双酚A为原料,合成了三种主链含硅聚芳酯,并对聚合物相关的物理性质进行了表征,制成了均质透明的薄膜.采用低真空法测定这些聚合物对H2、O2、N2、CO2、CH4的气体透过速率,并计算出气体透过系数、扩散系数、溶解系数、分离系数.从气体透过性能与聚合物分子结构关系的角度,按照气体透过的溶解-扩散机制,对聚合物的气体透过性能进行了研究,而且着重讨论了聚合物的堆积密度对气体扩散系数的影响,以及聚合物主链中极性链段的百分含量对气体溶解系数和溶解选择性的影响。 相似文献
74.
消除夹带溶胀的新液膜操作法曹汉瑾,褚莹,何彦涛,吴子生,严忠(东北师范大学化学系长春130024)关键词液膜,油/水乳液,溶胀,夹带,包裹消除液膜操作中的夹带溶胀对液膜的工业化具有重要意义,夹带溶胀分为包裹溶胀和再液化溶胀。前者是乳状液滴上浮时将水相... 相似文献
75.
76.
Poly(4-methyl-1-pentene) (PMP) hollow fiber membranes were prepared by the melt-spun and cold-stretch(MSCS) method. Scanning electronic microscopy (SEM) was used to characterize the section and surface structures of themembranes with special asymmetric structure. The preliminary results of gas permeation measurements indicated that the resultant hollow fiber membranes have the potential ability for oxygen/nitrogen separation. 相似文献
77.
水中酚的膜萃取分离流动注射技术测定的研究 总被引:6,自引:1,他引:6
本文提出了硅橡胶膜在线萃取分离流动注射技术测定水样中苯酚的方法。由于水样中的苯酚透过硅橡胶进入萃取液的萃取量随时间的增加和温度的升高而增大,故采用停流技术及升高温度以降低酚的检出限。 相似文献
78.
79.
A dense-phase latex rubber tube and a polyporous propylene hollow-fiber membrane module (HFMM) were investigated for control
of benzene-contaminated gas streams. The abiotic mass flux observed through the latex tube was 3.9–13 mg/(min·m2) for 150 ppm of benzene at various gas and liquid flow rates, while a 100-fold lower mass flux was observed in the HFMM.
After seeding with an aromatic-degrading culture enriched from activated sludge, the observed removal was 80% of 150 ppm,
corresponding toa mass flux of 45 mg/(min·m2). The observed mass flux through the HFMM during biofiltration also rose, to 0.4 mg/(min·m2). Because the HFMM had a 50-fold higher surface area than the latex tube, the observed ben zene removal was 99.8%. Compared
to conventional biofilters, the two reactors had modest elimination capacities, 2.5–18 g/(m3·h) in the latex tube membrane bioreactor and 4.8–58 g/(m3·h) in the HFMM. Although the HFMM had a higher elimination capacity, the gas-phase pressure drop was much greater. 相似文献
80.
《Electroanalysis》2005,17(11):1003-1007
A novel PVC membrane ion‐selective electrode based on tribenzyltin(IV) dithiocarbamate [Sn(IV)–TBDTB] as neutral carrier was developed for thiocyanate (SCN?) determination. The electrode exhibits a near‐Nernstian response for SCN? with a slope of 62.8±2.0 mV per decade over a wide concentration range 1.0×10?1–2.0×10?6 mol L?1 and a detection limit of 1.0×10?6 mol L?1 in MES–NaOH buffer, pH 6.0, at 25 °C. The electrode prepared with 1.5 wt.% Sn(IV)–TBDTB, 32.5 wt.% PVC and 66.0 wt.% 2‐nitrophenyloctyl ether (o‐NPOE) shows optimal response characteristics. Anti‐Hofmeister selectivity sequence for a series of anions shown by the electrode was as follows: SCN?>Sal?>I?>ClO >phCOO?>CH3COO?>Br?>Cl?>NO >NO >Citrate>SO42?. The useful pH range for the electrode was found to be 3–7 with a response time 30–40 s. The electrode has been used for direct determination of thiocyanate in wastewater with satisfactory results. 相似文献