全文获取类型
收费全文 | 1181篇 |
免费 | 50篇 |
国内免费 | 1篇 |
专业分类
化学 | 1002篇 |
晶体学 | 4篇 |
力学 | 9篇 |
数学 | 73篇 |
物理学 | 144篇 |
出版年
2023年 | 7篇 |
2022年 | 20篇 |
2021年 | 21篇 |
2020年 | 28篇 |
2019年 | 16篇 |
2018年 | 14篇 |
2017年 | 11篇 |
2016年 | 37篇 |
2015年 | 22篇 |
2014年 | 44篇 |
2013年 | 46篇 |
2012年 | 83篇 |
2011年 | 85篇 |
2010年 | 59篇 |
2009年 | 34篇 |
2008年 | 57篇 |
2007年 | 63篇 |
2006年 | 51篇 |
2005年 | 61篇 |
2004年 | 45篇 |
2003年 | 36篇 |
2002年 | 51篇 |
2001年 | 15篇 |
2000年 | 8篇 |
1999年 | 15篇 |
1998年 | 11篇 |
1997年 | 9篇 |
1995年 | 13篇 |
1994年 | 10篇 |
1993年 | 6篇 |
1992年 | 8篇 |
1990年 | 8篇 |
1989年 | 5篇 |
1988年 | 5篇 |
1987年 | 13篇 |
1985年 | 12篇 |
1984年 | 15篇 |
1983年 | 5篇 |
1982年 | 12篇 |
1981年 | 5篇 |
1980年 | 9篇 |
1978年 | 10篇 |
1977年 | 9篇 |
1976年 | 13篇 |
1975年 | 7篇 |
1973年 | 9篇 |
1962年 | 6篇 |
1947年 | 6篇 |
1935年 | 5篇 |
1928年 | 5篇 |
排序方式: 共有1232条查询结果,搜索用时 15 毫秒
91.
Inoue S Wang W Präsang C Asay M Irran E Driess M 《Journal of the American Chemical Society》2011,133(9):2868-2871
The first N-donor-stabilized phosphasilene LSi(SiMe(3))═PSiMe(3) (L = PhC(NtBu)(2)) has been synthesized in 87% yield through 1,2-silyl migration of the (Me(3)Si)(2)P-substituted, N-heterocyclic silylene [LSi-P(SiMe(3))(2)]. Remarkably, the latter reacts with dichlorotriphenylphosphorane Ph(3)PCl(2) to give the unprecedented 4π-electron Si(2)P(2)-cycloheterobutadiene [(LSi)(2)P(2)] with two-coordinate phosphorus atoms. The striking molecular structures as well as the (29)Si and (31)P NMR spectroscopic features of both products indicate the presence of zwitterionic Si═P bonds which is also in accordance with results by DFT calculations. 相似文献
92.
Magnesium dicyanamide tetrahydrate Mg[N(CN)2]2 · 4 H2O was synthesized by aqueous ion exchange starting from Na[N(CN)2] and Mg(NO3)2 · 6 H2O. The crystal structure was solved and refined on the basis of powder X‐ray diffraction data (P21/c, Z = 2, a = 737.50(2), b = 732.17(1), c = 971.67(2) pm, β = 98.074(1)°, wRp = 0.059, Rp = 0.046, RF = 0.075). In the crystal there are neutral complexes [Mg[N(CN)2]2(H2O)4] which are only connected via hydrogen bonds. Above 40 °C the tetrahydrate decomposes into anhydrous Mg[N(CN)2]2. 相似文献
93.
94.
We present a new method of measuring the electrophoretic mobility of a particle in a concentrated suspension. The method is used to measure the electrophoretic mobility of PMMA particles (diameter 10 microm) suspended in a mixture of liquid hydrocarbons. The particle volume fraction of the suspension is varied from 0 up to 0.30 and the resulting variation of the electrophoretic mobility is discussed. The suspending liquid is such that its refractive index is very close to that of the particles. Thus the suspension is almost transparent and it is possible to follow through a microscope the motion of one particle. The suspension is subjected to a low-frequency electric field (0.5 Hz). The cell containing the suspension is mounted on a piezoelectric crystal. The displacement that compensates for the particle motion (when the particle image is steady) is determined. 相似文献
95.
Gottfried Heinisch Barbara Matuszczak Elisabeth Spielmann Myriam Witvrouw Christophe Pannecouque Erik De Clercq 《Journal of heterocyclic chemistry》2001,38(1):125-130
Two methods for the preparation of dialkylsubstituted dipyridazino[4,3‐b:3′,4′‐e][1,4]diazepinones and dipyridazino[3,4‐b:3′,4′‐e][1,4]diazepinones are reported. The new compounds were evaluated for their inhibitory effects against the replication of human immunodeficiency virus [HIV‐1(IIIB) and HIV‐2(ROD)] in MT‐4 cells. 相似文献
96.
The morphology/habit of crystals of cold-crystallized poly(ethylene terephthalate) (PET) has been evaluated using scanning
and transmission electron microscopy and using atomic force microscopy. The combination of different preparation and analysis
techniques allowed assessing the structure at the nanometer scale of films of PET at both the surface and the bulk. It is
found that crystals formed on heating the amorphous glass to a temperature higher than the glass transition temperature are
of lamellar shape in the bulk and almost isometric habit at the surface. This finding is explained by different rates of nucleation/crystallization
in the bulk and at the surface, being supported by the observation of nanometer-scale surface heterogeneities after quenching
PET to ambient temperature before crystallization was initiated by heating. 相似文献
97.
Keller Hildegard Langer Elisabeth Lehner Harald Derflinger Gerhard 《Theoretical chemistry accounts》1978,49(2):93-100
The Algebraic Theory of Chirality Functions is derived by means of exclusively qualitative considerations. Hence, the significance of quantitative results is questionable. Moreover the construction of “Näherungsansätze” (”Approximation-Ansatz”), which may be interpreted as semiempirical methods, is achieved on the basis of plausibility and mathematical simplicity. Since physical arguments are not included, the consistency or inconsistency of “Näherungsansätze” with experimental results do not justify direct physical conclusions. 相似文献
98.
99.
Background
Protein kinase C interacting protein (PKCI/HINT1) is a small protein belonging to the histidine triad (HIT) family proteins. Its brain immunoreactivity is located in neurons and neuronal processes. PKCI/HINT1 gene knockout (KO) mice display hyper-locomotion in response to D-amphetamine which is considered a positive symptom of schizophrenia in animal models. Postmortem studies identified PKCI/HINT1 as a candidate molecule for schizophrenia and bipolar disorder. We investigated the hypothesis that the PKCI/HINT1 gene may play an important role in regulating mood function in the CNS. We submitted PKCI/HINT1 KO mice and their wild type (WT) littermates to behavioral tests used to study anti-depressant, anxiety like behaviors, and goal-oriented behavior. Additionally, as many mood disorders coincide with modifications of hypothalamic-pituitary-adrenal (HPA) axis function, we assessed the HPA activity through measurement of plasma corticosterone levels. 相似文献100.
Elisabeth Weber 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》1990,102(6):733-734