全文获取类型
收费全文 | 6016篇 |
免费 | 438篇 |
国内免费 | 15篇 |
专业分类
化学 | 4818篇 |
晶体学 | 36篇 |
力学 | 69篇 |
数学 | 697篇 |
物理学 | 849篇 |
出版年
2024年 | 10篇 |
2023年 | 58篇 |
2022年 | 83篇 |
2021年 | 107篇 |
2020年 | 197篇 |
2019年 | 187篇 |
2018年 | 77篇 |
2017年 | 98篇 |
2016年 | 266篇 |
2015年 | 251篇 |
2014年 | 300篇 |
2013年 | 326篇 |
2012年 | 466篇 |
2011年 | 498篇 |
2010年 | 289篇 |
2009年 | 240篇 |
2008年 | 373篇 |
2007年 | 352篇 |
2006年 | 319篇 |
2005年 | 258篇 |
2004年 | 243篇 |
2003年 | 199篇 |
2002年 | 193篇 |
2001年 | 107篇 |
2000年 | 86篇 |
1999年 | 75篇 |
1998年 | 70篇 |
1997年 | 79篇 |
1996年 | 66篇 |
1995年 | 73篇 |
1994年 | 87篇 |
1993年 | 51篇 |
1992年 | 48篇 |
1991年 | 43篇 |
1990年 | 33篇 |
1989年 | 45篇 |
1988年 | 30篇 |
1987年 | 24篇 |
1986年 | 19篇 |
1985年 | 11篇 |
1984年 | 13篇 |
1983年 | 8篇 |
1982年 | 10篇 |
1981年 | 15篇 |
1980年 | 19篇 |
1979年 | 13篇 |
1978年 | 16篇 |
1977年 | 14篇 |
1976年 | 8篇 |
1975年 | 3篇 |
排序方式: 共有6469条查询结果,搜索用时 31 毫秒
951.
952.
953.
Recknagel Sebastian Koch Matthias Wise Stephen A. Panne Ulrich 《Accreditation and quality assurance》2019,24(3):249-250
Accreditation and Quality Assurance - 相似文献
954.
Evaluation of Fe and Ru Pincer‐Type Complexes as Catalysts for the Racemization of Secondary Benzylic Alcohols 下载免费PDF全文
Dr. Oscar Verho Prof. Dr. Matthias Beller Prof. Dr. Jan‐E. Bäckvall 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(33):11583-11586
Fe and Ru pincer‐type catalysts are used for the racemization of benzylic alcohols. Racemization with the Fe catalyst was achieved within 30 minutes under mild reaction conditions, with a catalyst loading as low as 2 mol %. This reaction constitutes the first example of an iron‐catalyzed racemization of an alcohol. The efficiency for racemization of the Fe catalyst and its Ru analogue was evaluated for a wide range of sec‐benzylic alcohols. The commercially available Ru complex proved to be highly robust and even tolerated the presence of water in the reaction mixture. 相似文献
955.
Matthias Wrsching Sarah‐Kristin Fricke Jn Minr Robin Niklaus Constantin Hoch 《无机化学与普通化学杂志》2019,645(3):278-283
The subvalent nitridometalate Ba6[(Mo1–xTax)N4]N0.86 was prepared from mixtures of Mo powder with Ba, Na, and Ba2N at 600 °C in Ta ampoules. It crystallizes in space group Cmcm with a = 11.672(3), b = 10.177(2) and c = 10.8729(19) Å. Its crystal structure exhibits an orthorhombically distorted Perovskite topology with [Ba6N] building units forming the ReO3‐type lattice via common vertices, and the nitridometalate anions occupying half of the available distorted cuboctahedral interstices. [MN4] anions show statistically mixed occupancy of M by MoVI and TaV. They show no notable deviation from nitridometalate anions in known ionic nitridomolybdates and ‐tantalates, and the metrics of the [Ba6N] octahedra correspond to those found in similar subvalent compounds. The nitrogen atom position centering the [Ba6N] octahedra is underoccupied. Band structure calculations corroborate the subvalent character of the compound and the two individual anionic structural building units. 相似文献
956.
Matthias Lischka Dr. Renhao Dong Mingchao Wang Dr. Natalia Martsinovich Massimo Fritton Lukas Grossmann Prof. Dr. Wolfgang M. Heckl Prof. Dr. Xinliang Feng Prof. Dr. Markus Lackinger 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(8):1975-1983
The interplay between the self-assembly and surface chemistry of 2,3,6,7,10,11-hexaaminotriphenylene (HATP) on Cu(111) was complementarily studied by high-resolution scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS) under ultra-high vacuum conditions. To shed light on the competitive metal coordination, comparative experiments were carried out on pristine and nickel-covered Cu(111). Directly after room-temperature deposition of HATP onto pristine Cu(111), self-assembled aggregates were observed by STM, and XPS results indicated still protonated amino groups. Annealing up to 200 °C activated the progressive single deprotonation of all amino groups as indicated by chemical shifts of both the N 1s and C 1s core levels in the XP spectra. This enabled the formation of topologically diverse π–d conjugated coordination networks with intrinsic copper adatoms. The basic motif of these networks was a metal–organic trimer, in which three HATP molecules were coordinated by Cu3 clusters, as corroborated by the accompanying density functional theory (DFT) simulations. Additional deposition of more reactive nickel atoms resulted in both chemical and structural changes with deprotonation and formation of bis(diimino)–Ni bonded networks already at room temperature. Even though fused hexagonal metal-coordinated pores were observed, extended honeycomb networks remained elusive, as tentatively explained by the restricted reversibility of these metal–organic bonds. 相似文献
957.
Journal of Fourier Analysis and Applications - We prove a sharp general inequality estimating the distance of two probability measures on a compact Lie group in the Wasserstein metric in terms of... 相似文献
958.
Malik Salman Haider Jochen Schreiner Sabine Kendl Matthias Kroiss Robert Luxenhofer 《Macromolecular bioscience》2020,20(1)
Adrenocortical carcinoma (ACC) is a rare tumor and prognosis is overall poor but heterogeneous. Mitotane (MT) has been used for treatment of ACC for decades, either alone or in combination with cytotoxic chemotherapy. Even at doses up to 6 g per day, more than half of the patients do not achieve targeted plasma concentration (14–20 mg L?1) even after many months of treatment due to low water solubility, bioavailability, and unfavorable pharmacokinetic profile. Here a novel MT nanoformulation with very high MT concentrations in physiological aqueous media is reported. The MT‐loaded nanoformulations are characterized by Fourier transform infrared spectroscopy, differential scanning calorimetry, and powder X‐ray diffraction which confirms the amorphous nature of the drug. The polymer itself does not show any cytotoxicity in adrenal and liver cell lines. By using the ACC model cell line NCI‐H295 both in monolayers and tumor cell spheroids, micellar MT is demonstrated to exhibit comparable efficacy to its ethanol solution. It is postulated that this formulation will be suitable for i.v. application and rapid attainment of therapeutic plasma concentrations. In conclusion, the micellar formulation is considered a promising tool to alleviate major drawbacks of current MT treatment while retaining bioactivity toward ACC in vitro. 相似文献
959.
Regina Holm David Schwiertz Benjamin Weber Jennifer Schultze Jasmin Kuhn Kaloian Koynov Ulrich Lchelt Matthias Barz 《Macromolecular bioscience》2020,20(1)
RNA interference provides enormous potential for the treatment of several diseases, including cancer. Nevertheless, successful therapies based on siRNA require overcoming various challenges, such as poor pharmacokinetic characteristics of the small RNA molecule and inefficient cytosolic accumulation. In this respect, the development of functional siRNA carrier systems is a major task in biomedical research. To provide such a desired system, the synthesis of 3‐arm and 6‐arm PeptoStars is aimed for. The different branched polypept(o)idic architectures share a stealth‐like polysarcosine corona for efficient shielding and a multifunctional polylysine core, which can be independently varied in size and functionality for siRNA complexation‐, transport and intra cellular release. The special feature of star‐like polypept(o)ides is in their uniform small size (<20 nm) and a core–shell structure, which implies a high stability and stealth‐like properties and thus, they may combine long circulation times and a deep penetration of cancerous tissue. Initial toxicity and complement studies demonstrate well tolerated cationic PeptoStars with high complexation capability toward siRNA (N/P ratio up to 3:1), which can lead to potent RNAi for optimized systems. Here, the synthetic development of 3‐arm and 6‐arm polypept(o)idic star polymers, their modification with endosomolytic moieties, and first in vitro insights on RNA interference are reported on. 相似文献
960.
Matthew L. Gettings Michael T. Thoenen Dr. Edward F. C. Byrd Dr. Jesse J. Sabatini Dr. Matthias Zeller Prof. Dr. Davin G. Piercey 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(64):14530-14535
This work reports the first compound containing both a tetrazole and an azasydnone ring, a unique energetic material. Several energetic salts of the tetrazole azasydnone were synthesized and characterized, leading to the creation of new secondary and primary explosives. Molecular structures are confirmed by 1H and 13C NMR, IR spectroscopy, and X-ray crystallographic analysis. The high heats of formation, fast detonation velocities, and straight-forward synthesis of energetic azasydnones should capture the attention of future energetics research. 相似文献