全文获取类型
收费全文 | 969篇 |
免费 | 20篇 |
国内免费 | 2篇 |
专业分类
化学 | 697篇 |
晶体学 | 2篇 |
力学 | 7篇 |
数学 | 35篇 |
物理学 | 250篇 |
出版年
2022年 | 7篇 |
2021年 | 13篇 |
2020年 | 9篇 |
2019年 | 11篇 |
2018年 | 5篇 |
2017年 | 6篇 |
2016年 | 14篇 |
2015年 | 16篇 |
2014年 | 14篇 |
2013年 | 50篇 |
2012年 | 39篇 |
2011年 | 72篇 |
2010年 | 34篇 |
2009年 | 42篇 |
2008年 | 52篇 |
2007年 | 64篇 |
2006年 | 51篇 |
2005年 | 48篇 |
2004年 | 41篇 |
2003年 | 37篇 |
2002年 | 30篇 |
2001年 | 30篇 |
2000年 | 23篇 |
1999年 | 13篇 |
1998年 | 12篇 |
1997年 | 8篇 |
1996年 | 12篇 |
1995年 | 11篇 |
1994年 | 17篇 |
1993年 | 8篇 |
1992年 | 13篇 |
1991年 | 12篇 |
1990年 | 13篇 |
1989年 | 10篇 |
1988年 | 14篇 |
1987年 | 11篇 |
1986年 | 9篇 |
1985年 | 19篇 |
1984年 | 11篇 |
1983年 | 4篇 |
1982年 | 7篇 |
1981年 | 13篇 |
1980年 | 11篇 |
1979年 | 12篇 |
1977年 | 5篇 |
1976年 | 5篇 |
1975年 | 6篇 |
1973年 | 8篇 |
1972年 | 3篇 |
1968年 | 2篇 |
排序方式: 共有991条查询结果,搜索用时 0 毫秒
81.
Cylindrospermopsin determination using 2-[4-(2-hydroxyethyl)-1-piperazinyl]ethanesulfonic acid (HEPES) as the internal standard 总被引:1,自引:0,他引:1
Cylindrospermopsin (CYN) was determined by liquid chromatography/electrospray ionization-mass spectrometry (LC/ESI-MS) using 2-[4-(2-hydroxyethyl)-1-piperazinyl]ethanesulfonic acid (HEPES) as the internal standard. In the selected ion monitoring of LC/ESI-MS, m/z 414 for CYN and 237 for HEPES were monitored using the negative mode; the retention times of CYN and HEPES were 12.41 and 14.21 min, respectively. CYN was determined from peak area ratios of m/z 414/237. By the treatment of an anion exchange cartridge using a buffer at pH 10.5, CYN was isolated and condensed. No interfering peak was observed. Linearity of this method was observed at the range of 0.10-31.12 ng. Total coefficients of variation were 5.1 and 2.9% at 104 and 1038 μg CYN L−1. The quantitative limit at a signal-to-noise (S/N) ratio of 10 was 0.16 ng.CYN concentration in natural waters is low. CYN in waters should be condensed for determination. This method including the treatment for isolation and condensation of CYN is useful for determination of CYN in environmental and/or drinking waters. 相似文献
82.
Y Nomoto H Takai T Hirata M Teranishi T Ohno K Kubo 《Chemical & pharmaceutical bulletin》1991,39(1):86-90
A series of 1-(6,7-dimethoxy-4-quinazolinyl)piperidines carrying various 5-membered heterocycles at the 4-position was synthesized and examined for cardiotonic activity in anesthesized dogs. The (4-oxo-2-thioxo-3-imidazolindinyl)amino derivatives showed the most potent inotropic activity. Marked loss of activity was observed in the 2,4-dihydro-3-thioxo-3H-1,2,4-triazolyl, the 2,4-dihydro-3-oxo-3H-pyrazolyl and the (2,3-dihydro-2-thioxo-3H-1,3,4-thiadiazol-5-yl)amino derivatives. The synthesis and structure-activity relationships are discussed. 相似文献
83.
84.
Sonomi Arata Dr. Yuna Kim Prof. Norihisa Hoshino Dr. Keishiro Tahara Dr. Kiyonori Takahashi Dr. Tomofumi Kadoya Tomonori Inoue Prof. Takayoshi Nakamura Prof. Tomoyuki Akutagawa Prof. Jun-ichi Yamada Prof. Kazuya Kubo 《欧洲无机化学杂志》2023,26(12):e202300017
Unsymmetrical gold(III)-dithiolene complexes are potential candidates for molecular materials that exhibit thermal structural phase transitions. In this study, unsymmetrical ppy-gold(III) (ppy−=C-deprotonated-2-phenylpyridine(−)) complexes [AuC5] and [AuC6] coordinated by dithiolene ligands containing tetrathiafulvalene (TTF) skeletons with pentylthio (2-{bis(pentylthio)-1,3-dithiol-2-ylidene}-1,3-dithiol-4,5-dithiolate(2−)) and hexylthio groups (2-{bis(hexylthio)-1,3-dithiol-2-ylidene}-1,3-dithiol-4,5-dithiolate(2−)) were synthesized. Both complexes exhibited a large absorption band at approximately 508 nm, owing to intramolecular ligand-to-ligand charge transfer. One-dimensional columnar structures with head-to-tail molecular arrangements around the metal ions were constructed in the crystals. The flexible alkylthio groups were intercalated into crystalline spaces between dithiolene ligands in the columns. [AuC5] exhibits a simple phase transition at 198 °C between crystalline and isotropic phases irreversibly. The crystalline phase of [AuC6] observed at 25 °C melted at 148 °C. Another crystalline phase grew above 148 °C with a very slow crystallization rate from the liquid phase and was completely transformed into an isotropic phase at 200 °C. 相似文献
85.
We propose an abstract variational inequality formulation of the Cahn–Hilliard equation with a time-dependent constraint. We introduce notions of strong and weak solutions, and prove that a strong solution, if it exists, is a weak solution, and that the existence of a unique weak solution holds under an appropriate time-dependence condition on the constraint. We also show that the weak solution is a strong solution under appropriate assumptions on the data. Our abstract results can be applied to various concrete problems. 相似文献
86.
Masahiro Kubo 《Journal of Mathematical Analysis and Applications》2005,307(1):232-244
We study Neumann problem for a class of nonlinear degenerate parabolic PDE. A typical nonlinearity we have in mind is, for instance, β(u)=−1/u(u>0). We establish a necessary and sufficient condition on given data for existence of solution. 相似文献
87.
Masahiro Kubo 《Journal of Evolution Equations》2007,7(4):701-717
We study an abstract second order nonlinear evolution equation in a real Hilbert space. We consider time-dependent convex
functions and their subdifferentials operating on the first derivative of the unknown function. Introducing appropriate assumptions
on the convex functions and other data, we prove the existence and uniqueness of a strong solution, and give some applications
of the abstract theorem to hyperbolic variational inequalities with time-dependent constraints.
相似文献
88.
Hiroaki Inoue Yuji Arai Tsunao Kishida Masaharu Shin-Ya Ryu Terauchi Shuji Nakagawa Masazumi Saito Shinji Tsuchida Atsuo Inoue Toshiharu Shirai Hiroyoshi Fujiwara Osam Mazda Toshikazu Kubo 《Ultrasonics》2014
The goal of this feasibility study was to examine whether sonoporation assisted transduction of siRNA could be used to ameliorate arthritis locally. If successful, such approach could provide an alternative treatment for the patients that have or gradually develop adverse response to chemical drugs. Tumor necrosis factor alpha (TNF-α) produced by synovial fibroblasts has an important role in the pathology of rheumatoid arthritis, inducing inflammation and bone destruction. In this study, we injected a mixture of microbubbles and siRNA targeting TNF-α (siTNF) into the articular joints of rats, and transduced siTNF into synovial tissue by exposure to a collimated ultrasound beam, applied through a probe 6 mm in diameter with an input frequency of 3.0 MHz, an output intensity of 2.0 W/cm2 (spatial average temporary peak; SATP), a pulse duty ratio of 50%, and a duration of 1 min. Sonoporation increased skin temperature from 26.8 °C to 27.3 °C, but there were no adverse effect such as burns. The mean level of TNF-α expression in siTNF-treated knee joints was 55% of those in controls. Delivery of siTNF into the knee joints every 3 days (i.e., 7, 10, 13, and 16 days after immunization) by in vivo sonoporation significantly reduced paw swelling on days 20–23 after immunization. Radiographic scores in the siTNF group were 56% of those in the CIA group and 61% of those in the siNeg group. Histological examination showed that the number of TNF-α positive cells was significantly lower in areas of pannus invasion into the ankle joints of siTNF- than of siNeg-treated rats. These results indicate that transduction of siTNF into articular synovium using sonoporation may be an effective local therapy for arthritis. 相似文献
89.
Simple modules over the Leibniz pairs are studied. Simple Poisson modules over Poisson algebras of the semisimple associative algebra structure are determined and they are nothing but simple bimodules over simple associative algebras with standard noncommutative Poisson algebra structure. 相似文献