全文获取类型
收费全文 | 10675篇 |
免费 | 275篇 |
国内免费 | 31篇 |
专业分类
化学 | 7976篇 |
晶体学 | 37篇 |
力学 | 162篇 |
数学 | 1785篇 |
物理学 | 1021篇 |
出版年
2020年 | 138篇 |
2019年 | 109篇 |
2018年 | 77篇 |
2017年 | 85篇 |
2016年 | 191篇 |
2015年 | 205篇 |
2014年 | 192篇 |
2013年 | 362篇 |
2012年 | 410篇 |
2011年 | 463篇 |
2010年 | 340篇 |
2009年 | 283篇 |
2008年 | 462篇 |
2007年 | 449篇 |
2006年 | 473篇 |
2005年 | 442篇 |
2004年 | 381篇 |
2003年 | 318篇 |
2002年 | 329篇 |
2001年 | 228篇 |
2000年 | 164篇 |
1999年 | 148篇 |
1998年 | 181篇 |
1997年 | 148篇 |
1996年 | 152篇 |
1995年 | 151篇 |
1994年 | 145篇 |
1993年 | 192篇 |
1992年 | 131篇 |
1991年 | 131篇 |
1990年 | 116篇 |
1989年 | 134篇 |
1988年 | 133篇 |
1987年 | 169篇 |
1986年 | 158篇 |
1985年 | 174篇 |
1984年 | 186篇 |
1983年 | 157篇 |
1982年 | 144篇 |
1981年 | 151篇 |
1980年 | 155篇 |
1979年 | 150篇 |
1978年 | 138篇 |
1977年 | 121篇 |
1976年 | 133篇 |
1975年 | 94篇 |
1974年 | 89篇 |
1973年 | 88篇 |
1971年 | 80篇 |
1970年 | 71篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
Zusammenfassung Es werden molekulare Struktur, Energie des Grundzustandes, Bindungsabstände, Bindungsenergie, Ionisierungsenergie und Protonenaffinität der Siliziumwasserstoffverbindungen SiH
n
, SiH
n
+ und SiHn
– (n=3, 4 oder 5) nach der Einzentrenmethode berechnet.
OCE-calculations on some silicon hydrides of the type SiH n , SiH n + and SiH n –
OCE-Calculations are reported for molecular structures, ground state energies, bond distances, binding energies, ionization potentials and proton affinities of the silicon hydrides SiH n , SiH n + and SiH n – (n=3, 4 or 5).
Résumé Calcul par la méthode monocentrique de la structure moléculaire, de l'énergie de l'état fondamental, des longueurs de liaison, des énergies de liaison, des potentiels d'ionisation et des affinités protoniques pour les hydrures de silicium SiH n , SiH n + et SiH n – (n=3, 4 ou 5).相似文献
72.
Wolfgang Nolte 《Journal of Geometry》1980,14(1):1-22
The extended reflection groups of a metric vector space (V,f) are introduced and defined by a system of generators and a set of defining relations. It can be proved that they are isomorphic to certain subgroups of the orthogonal groups. The main result of the underlying paper is that these groups can be characterized by a few properties among which we mention the validity of the transitivity theorem and the property of — intersecting . Finally, we obtain a characterization of the (full) groups O*(V,f) in the case dim V1.
Herrn Professor Dr. Reinhold Baer zum 75. Geburtstag gewidmet 相似文献
Herrn Professor Dr. Reinhold Baer zum 75. Geburtstag gewidmet 相似文献
73.
Wolfgang Weil 《manuscripta mathematica》1981,36(1):1-18
It is shown that there exists a distribution T on n ( unit sphere of Euclidean n-space) such that the mixed volume V(K1,...,Kn) equals
for all convex bodies Ki, where
is the support function of ki and denotes the tensor product. As a consequence, mixed volumes are approximated uniformly by n-fold integrals of the corresponding support functions. 相似文献
74.
The analysis of microbial communities is of increasing importance in life sciences and bioengineering. Traditional techniques of investigations like culture or cloning methods suffer from many disadvantages. They are unable to give a complete qualitative and quantitative view of the total amount of microorganisms themselves, their interactions among each other and with their environment. Obviously, the determination of static or dynamic balances among microorganisms is of fast growing interest. The generation of species specific and fluorescently labeled 16S ribosomal DNA (rDNA) fragments by the terminal restriction fragment length polymorphism (T-RFLP) technique is a suitable tool to overcome the problems other methods have. For the separation of these fragments polyacrylamide gel sequencers are preferred as compared to capillary sequencers using linear polymers until now because of their higher electrophoretic resolution and therefore sizing accuracy. But modern capillary sequencers, especially multicapillary sequencers, offer an advanced grade of automation and an increased throughput necessary for the investigation of complex communities in long-time studies. Therefore, we adapted a T-RFLP technique to an automated high-throughput multicapillary electrophoresis device (ABI 3100 Genetic Analysis) with regard to a precise qualitative and quantitative characterization of microbial communities. 相似文献
75.
Preparation and Crystal Structure of Cadmium Azide Cd(N3)2 Solvent free, binary cadmium azide was synthesized by the reaction of cadmium carbonate and a 24 weight% solution of HN3 in water. Cadmium azide is a colorless, crystalline powder which is highly sensitive to percussion and heat. Caution, the manipulation of Cd(N3)2 is very dangerous! The crystal structure was solved by single‐crystal methods and the phase purity was verified by a Rietveld refinement (Cd(N3)2, Pbca, no. 61; a = 7.820(2), b = 6.440(2), c = 16.073(3) Å; Z = 8, 1174 independent reflections, 64 parameters, R1 = 0.022). Cadmium azide crystallizes in a new structure type. In the crystal there are edge‐sharing Cd2(N3)10 double octahedrons which are further connected to other units by azide bridges. Vibrational spectroscopic investigations (Raman an IR) are discussed with respect to the crystal structure data. 相似文献
76.
77.
78.
The crystalline chiral auxiliaries , and were prepared from camphor-10-sulfonyl chlorides in 2 steps. Their readily accessible acrylates underwent efficient asymmetric diels-alder additions to cyclopentadiene, the topicity of which agrees with X-ray evidence. 相似文献
79.
The mercury perrhenates with the empirical formulas HgReO4 and Hg2ReO5 were prepared by annealing powdered mixtures of mercury(II)oxide and mercury(II)metaperrhenate Hg(ReO4)2 in sealed silica tubes. Their crystal structures were determined from single-crystal X-ray data. HgReO4 crystallizes dimeric with nearly linear O3Re? O? Hg? Hg? O? ReO3 molecular units and Hg2ReO5 has a solid state structure, where Hg(I) and Hg(II) together with oxygen atoms form 14-membered rings, which are condensed to two-dimensionally infinite polycationic nets of composition (Hg22+ · 2 HgO)n. These nets are separated from each other by tetrahedral ReO4? anions. 相似文献
80.
A review with 159 references is presented on the applications of adsorptive stripping voltammetry (AdSV) for determining
trace metal ions in different environmental samples (e.g. water, soil, plant, biological fluids). The analytical applications
of AdSV to biologically active organic compounds (e.g. pharmaceuticals, pesticides, biomolecules) are also discussed.
Received: 18 December 1995/Revised: 8 January 1997/Accepted: 12 January 1997 相似文献