全文获取类型
收费全文 | 1537篇 |
免费 | 55篇 |
国内免费 | 6篇 |
专业分类
化学 | 1129篇 |
晶体学 | 19篇 |
力学 | 19篇 |
数学 | 84篇 |
物理学 | 347篇 |
出版年
2023年 | 12篇 |
2022年 | 15篇 |
2021年 | 16篇 |
2020年 | 16篇 |
2019年 | 26篇 |
2018年 | 25篇 |
2017年 | 20篇 |
2016年 | 29篇 |
2015年 | 41篇 |
2014年 | 42篇 |
2013年 | 71篇 |
2012年 | 98篇 |
2011年 | 118篇 |
2010年 | 56篇 |
2009年 | 48篇 |
2008年 | 95篇 |
2007年 | 85篇 |
2006年 | 91篇 |
2005年 | 89篇 |
2004年 | 72篇 |
2003年 | 63篇 |
2002年 | 69篇 |
2001年 | 20篇 |
2000年 | 21篇 |
1999年 | 12篇 |
1998年 | 8篇 |
1997年 | 19篇 |
1996年 | 25篇 |
1995年 | 14篇 |
1994年 | 25篇 |
1993年 | 12篇 |
1992年 | 16篇 |
1991年 | 11篇 |
1990年 | 13篇 |
1989年 | 13篇 |
1988年 | 7篇 |
1987年 | 10篇 |
1986年 | 7篇 |
1985年 | 17篇 |
1984年 | 18篇 |
1983年 | 12篇 |
1982年 | 9篇 |
1981年 | 19篇 |
1980年 | 6篇 |
1979年 | 9篇 |
1978年 | 13篇 |
1977年 | 13篇 |
1976年 | 7篇 |
1973年 | 7篇 |
1968年 | 6篇 |
排序方式: 共有1598条查询结果,搜索用时 15 毫秒
11.
Tetsuya Noda 《European Polymer Journal》2007,43(6):2321-2330
Continuous ATRP of MMA was carried out in a flow tubular reactor with varying flow rate, temperature, and [monomer]/[initiator] ratios. Changing the flow rate directly relates to the reaction time. This process produces polymer continuously with the conversion increasing with decreasing flow rate. The molecular weight (relating to the flow rate) increases linearly with conversion which is also observed when the [monomer]/[initiator] ratio was changed. The effect of altering the reaction temperature was studied and the apparent activation energy of the propagation reaction of MMA in this system was calculated to be ∼56.9 kJ mol−1, close to the values reported previously. Preparation of diblock copolymers is also reported with varying comonomers and the conversion, and SEC results suggested that this continuous system is an excellent and facile way to have a continuous ATRP process. 相似文献
12.
Tetsuya Okuyama Masaru Nakayama Yoshitsugu Tomokiyo Omer Van Der Biest 《Microscopy and microanalysis》2002,8(1):11-15
Lattice strains around a platelet oxygen precipitate in Si wafer is studied by energy filtering convergent-beam electron diffraction (CBED) and calculations based on the finite element method (FEM). Local lattice strains are measured from CBD patterns obtained with a probe size less than 2 nm in a specimen thicker than 450 nm. Strains measured are compressive along a direction normal to a plate of the precipitation and tensile along a direction parallel to the plate. Two-dimensional stress fields near the precipitate are obtained with FEM computer analyses by fitting the measured strains. It appears that shear stresses are concentrated at the end of the precipitate edge and the maximum shear stress at an interface between the precipitate and the Si-matrix is 1.9 GPa. It is demonstrated that a combination of the energy filtering CBED and FEM is very useful for the study of local strains near interfaces in semiconductor devices, in particular for the study of stress fields that are too steep for application of the conventional CBED technique. 相似文献
13.
We have developed a sensitive method for the measurement of rhodanese activity in human serum which is based on the colorimetric method for the determination of thiocyanate produced from methanethiosulfonate and cyanide as substrates. Thiocyanate gives a red complex with ferric ion in an acidic condition. The present method is about 70-fold more sensitive than the conventional method using cyanide and thiosulfate as substrates and correlates well (r = 0.997) with the conventional method in bovine liver rhodanese. Within-run precision of the method is 0.91% for 420 units/l serum and the calibration curve is linear up to 1850 units/l. The normal value for human serum, determined by the present method on 31 healthy persons, was 20.9 +/- 20.0 units/l (mean +/- 2S.D.). Rhodanese activity was clearly elevated in some serum samples which were observed at abnormal values in some biochemical diagnostic tests and showed significant positive correlations with guanase activity (r = 0.728, p less than 0.01) and glutamic-oxalacetic transaminase activity (r = 0.625, p less than 0.01). 相似文献
14.
15.
We compute the cyclic homology of the coordinate ring A(SLq(2)) of the quantum algebraic group SL
q
(2). We observe a degeneration of the noncommutative de Rham complex. The results are also verified from the point of view of Connes' noncommutative differential geometry. 相似文献
16.
Tetsuji Kametani Hideo Lida Shinzo Kano Sadao Tanaka Keiichiro Fukumoto Shiroshi Shibuya Haruhiko Yagi 《Journal of heterocyclic chemistry》1967,4(1):85-92
Schotten-Baumann reaction of the amine (X) with 4-benzyloxy-3,4′-oxydiphenylacetyl chloride (XI) gave two amides, (XIIa) and (XIIb), which were cyclized to give the corresponding 3,4-dihydroisoquinolines, respectively. Methylation of the above 3,4-dihydro-isoquinolines, followed by hydrolysis, afforded the compounds having the same composition as berbamine (Ia) and oxyacanthine (Ib), whose structures are under examination. 相似文献
17.
Kazuhiko Matsumoto Tetsuya Tsuda Toshiyuki Nohira Rika Hagiwara Yasuhiko Ito Osamu Tamada 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(3):m186-m187
In the title complex, (C6H11N2)3[LaCl6], centrosymmetric octahedral hexachlorolanthanate anions are located at the corners and face‐centers of the monoclinic unit cell. The ring H atoms of the cations interact with the Cl atoms of the anions via hydrogen bonding, and bifurcation of the hydrogen bonding is observed. Cation–cation interactions via hydrogen bonding between the ring H atoms and π‐electrons of aromatic rings are also observed as in other imidazolium salts. 相似文献
18.
Chowdhury Wasimul Q. Idehara Kenji Maeda Isamu Umeda Fusako Yagi Kiyohito Miura Yoshiharu Mizoguchi Tadashi 《Applied biochemistry and biotechnology》1996,57(1):361-366
Applied Biochemistry and Biotechnology - A marine photosynthetic bacterium,Rhodopseudomonas sp. strain W-1S, accumulated polyhydroxybutyrate (PHB) to 56% of the dry cell weight under microaerobic... 相似文献
19.
A simple synthesis of 3,3,3-trifluoropropenyl compounds by means of the TBAF-mediated Horner reaction is described. The reagent, 2,2,2-trifluoroethyldiphenylphosphine oxide, was readily prepared either by Arbuzov reaction of ethyl diphenylphosphinite with 2,2,2-trifluoroethyl iodide or by treating chlorodiphenylphosphine with trifluoroacetic acid and water. Treatment of the phosphine oxide with aromatic aldehydes in the presence of TBAF at room temperature afforded the corresponding 3,3,3-trifluoropropenyl compounds in good yields. The present method is very convenient for preparing 3,3,3-trifluoropropenyl compounds from aromatic aldehydes in terms of availability of the reagent, operational simplicity, and good yields of the products. 相似文献
20.
Bovine lung thrombomodulin was partially purified, and immobilized on agarose gel (Sepharose 4B). Immobilized thrombomodulin inhibited the procoagulant activity of thrombin, and enhanced the thrombin-catalyzed protein C activation. The plasma recalcification time test showed that immobilized thrombomodulin prolonged plasma clotting time. It is suggested that the immobilization of thrombomodulin will provide an antithrombogenic biomaterial able to convert thrombin from a procoagulant to an anticoagulant enzyme. 相似文献