全文获取类型
收费全文 | 26687篇 |
免费 | 4638篇 |
国内免费 | 4665篇 |
专业分类
化学 | 18804篇 |
晶体学 | 446篇 |
力学 | 1995篇 |
综合类 | 470篇 |
数学 | 3155篇 |
物理学 | 11120篇 |
出版年
2024年 | 84篇 |
2023年 | 454篇 |
2022年 | 918篇 |
2021年 | 1007篇 |
2020年 | 1024篇 |
2019年 | 995篇 |
2018年 | 912篇 |
2017年 | 846篇 |
2016年 | 1167篇 |
2015年 | 1324篇 |
2014年 | 1493篇 |
2013年 | 1983篇 |
2012年 | 2208篇 |
2011年 | 2433篇 |
2010年 | 1734篇 |
2009年 | 1718篇 |
2008年 | 1845篇 |
2007年 | 1656篇 |
2006年 | 1603篇 |
2005年 | 1410篇 |
2004年 | 1229篇 |
2003年 | 855篇 |
2002年 | 835篇 |
2001年 | 797篇 |
2000年 | 735篇 |
1999年 | 624篇 |
1998年 | 485篇 |
1997年 | 407篇 |
1996年 | 418篇 |
1995年 | 391篇 |
1994年 | 362篇 |
1993年 | 316篇 |
1992年 | 304篇 |
1991年 | 241篇 |
1990年 | 232篇 |
1989年 | 191篇 |
1988年 | 129篇 |
1987年 | 120篇 |
1986年 | 96篇 |
1985年 | 92篇 |
1984年 | 65篇 |
1983年 | 67篇 |
1982年 | 53篇 |
1981年 | 37篇 |
1980年 | 23篇 |
1979年 | 13篇 |
1978年 | 5篇 |
1977年 | 6篇 |
1975年 | 6篇 |
1957年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
42.
43.
44.
45.
46.
A study on the ductile deformation domain of the brittle fault in the shallow level ofthe crust is a new probe field for the modern structural geology. Taking the southern Jiang-su Province area as an example the orientation measurement of quartz crystals, the com-positional texture observation of three pressure sensitive minerals and the rheological param-eter determination of dislocation densities, etc. have been demonstrated and analysed basedon typical samples in the present paper. In addition, their generation mechanisms arealso discussed from the cataclastic rheology, the dynamic differentiation and the simpleshearing, specially, from the Ode strength theory. Finally, a generative relationship betweenthe ductile deformation domain of the brittle fault system, in the regional layer--slip andthe formation of the stratabound ore deposit is shown as well. 相似文献
47.
Synthesis, single-crystal structure determination, and magnetic properties are reported for manganese carbodiimide, MnNCN. The presumably unstable but inert phase adopts the trigonal system (R3m) with a = 3.3583(4) A, c = 14.347(2) A, V = 140.13(3) A3, and Z = 3. Divalent manganese is octahedrally coordinated by nitrogen atoms at 2.26 A, and the NCN(2-) unit adopts the linear [N=C=N](2-) carbodiimide shape with two C=N double bonds of 1.23 A. MnNCN contains high-spin Mn(II) with five unpaired electrons and behaves like an antiferromagnet with an ordering temperature below 30 K. 相似文献
48.
Cai H Chen T Wang X Schultz AJ Koetzle TF Xue Z 《Chemical communications (Cambridge, England)》2002,(3):230-231
Reactions of Ta(NMe2)5 with D2SiR'Ph (R' = Me, Ph) were found to give a dideuteride eta 2-imine complex (Me2N)3Ta(mu-D)2(mu-N-eta 2-N,C-CH2NMe)Ta(NMe2)3(1-d2) through C-H activation of an amide ligand via beta-H abstraction, and the structure of 1 was confirmed by single crystal neutron and X-ray diffraction. 相似文献
49.
Separation and determination of podophyllum lignans by micellar electrokinetic chromatography 总被引:2,自引:0,他引:2
A micellar electrokinetic chromatography method was established for the quantitative analysis of seven podophyllum lignans in Podophyllum emodi Wall. var. chinesis sprague. The optimum buffer system was 10 mM NaH2PO4-5 mM borate-100 mM sodium dodecylsulfate-30% isopropanol (pH 7.20). Voltage was 18 kV and detection at 214 nm. The second derivative chromatogram was used to determine a low-content component and those not fully separated from adjacent ones. The RSD values of migration times and peak areas were <2.2 and <5.5%, respectively. The effects of several CE parameters on the resolutions were studied systematically. 相似文献
50.
严继民 《中国科学B辑(英文版)》1990,(7)
An ab initio calculation of the hydrogen bond complex (HF)_2 is given with the 6-311 G~(**) basis set, according to which the potential surface around the balance point of the distancès and the orientations between two HF molecules is obtained. The atomic charges in the system are calculated with the PD/LSF method (potential-derived/least-square-fitting method) and then an analysis of the hydrogen bond interaction between two HF molecules is given with the (exp-6-1) potential function, by means of which it is shown that the main interaction between them is not an electro-static but a charge transfer one. The potential curve between two HF molecules is like a Morse function. 相似文献