全文获取类型
收费全文 | 1318篇 |
免费 | 53篇 |
国内免费 | 5篇 |
专业分类
化学 | 1068篇 |
晶体学 | 10篇 |
力学 | 6篇 |
数学 | 74篇 |
物理学 | 218篇 |
出版年
2023年 | 11篇 |
2022年 | 14篇 |
2021年 | 17篇 |
2020年 | 16篇 |
2019年 | 24篇 |
2018年 | 16篇 |
2017年 | 21篇 |
2016年 | 29篇 |
2015年 | 29篇 |
2014年 | 42篇 |
2013年 | 87篇 |
2012年 | 68篇 |
2011年 | 102篇 |
2010年 | 48篇 |
2009年 | 40篇 |
2008年 | 91篇 |
2007年 | 81篇 |
2006年 | 76篇 |
2005年 | 77篇 |
2004年 | 80篇 |
2003年 | 71篇 |
2002年 | 75篇 |
2001年 | 13篇 |
2000年 | 20篇 |
1999年 | 13篇 |
1998年 | 16篇 |
1997年 | 13篇 |
1996年 | 15篇 |
1995年 | 6篇 |
1994年 | 4篇 |
1993年 | 5篇 |
1992年 | 3篇 |
1991年 | 10篇 |
1990年 | 8篇 |
1989年 | 5篇 |
1988年 | 7篇 |
1986年 | 4篇 |
1985年 | 14篇 |
1984年 | 13篇 |
1982年 | 9篇 |
1981年 | 13篇 |
1980年 | 10篇 |
1979年 | 7篇 |
1978年 | 4篇 |
1977年 | 12篇 |
1976年 | 6篇 |
1975年 | 3篇 |
1974年 | 4篇 |
1973年 | 3篇 |
1964年 | 3篇 |
排序方式: 共有1376条查询结果,搜索用时 234 毫秒
931.
Nobu Kato Masato Tanaka Tetsuya Fukasawa Soichiro Kyushin 《Journal of organometallic chemistry》2009,694(19):3212-3214
A mixture of tricyclic ladder polysilane 1 and amylose, upon pH adjustment of aqueous media from very basic to neutral, affords a supramolecular complex in which a preferential twisted (helical) conformation is induced on the ladder polysilane to display optical activity. Under the experimental conditions used, 1 assumes a left-handed twisted structure in the left-handed helical channel of amylose. 相似文献
932.
Izuru Kawamura Junko Tanabe Masato Ohmine Satoru Yamaguchi Satoru Tuzi Akira Naito 《Photochemistry and photobiology》2009,85(2):624-630
Structural changes in bacteriorhodopsin (bR) in two different processes of retinal reconstitutions were investigated by observing the 13C and 15N solid‐state NMR spectra of [1‐13C]Val‐ and [15N]Pro‐labeled bR. We found that NMR signals of the BC loop were sensitive to changes in protein structure and dynamics, from wild‐type (WT) bR to bacterio‐opsin (bO), regenerated bR and E1001 bR. Regenerated bR was prepared following the addition of retinal into bO obtained from photobleached WT‐bR. E1001 bR was cultured from a retinal‐deficient strain termed E1001 following the addition of retinal to growing cells. 15N NMR signal at Pro70 in the BC loop in WT‐bR was observed at 122.4 p.p.m., whereas signals were not apparent or partly suppressed in bO and regenerated bR, respectively. Similarly, the 13C NMR signal at Val69 in the BC loop at 172.0 p.p.m. that was observed in WT‐bR was significantly decreased in both regenerated bR and bO. These results suggest that the dynamic structure of the BC loop in bO was substantially altered following the removal of retinal. As a consequence, the correct protein structure failed to be recovered via the regenerating process of retinal to bO. On the other hand, 13C and 15N NMR signals at the BC loop in E1001 bR appeared at positions identical to those of WT‐bR. The results of the current study indicate that the BC loop may not always fold correctly in the regenerated bR, which leads to different properties in the regenerated bR compared to that of WT‐bR. 相似文献
933.
A liquid chromatography-tandem mass spectrometry (LC-MS/MS) method using a high-resolution octadecyl silica column compatible with aqueous compounds was developed for the simultaneous determination of benzodiazepines and their metabolites in human serum. This method enabled us to determine multiple benzodiazepines, including flurazepam, bromazepam, chlordiazepoxide, nitrazepam, clonazepam, flunitrazepam, estazolam, clobazam, lorazepam, alprazolam, triazolam, brotizolam, fludiazepam, diazepam, quazepam, prazepam and their metabolites such as 7-aminonitrazepam, 7-aminoclonazepam, 7-acetamidonitrazepam, N-desmethylclobazam and N-desmethyldiazepam. The analytes spiked into human serum were subjected to solid-phase extraction followed by liquid chromatography coupled with electrospray ionization tandem mass spectrometry. The running time was within 25 min for the measurement of 22 benzodiazepines and their metabolites. The recovery rates exceeded 58.1% for those compounds except for quazepam, which showed a recovery of 45.8%. The limit of detection ranged from 0.3 to 11.4 ng/mL. Linearity was satisfactory for all compounds. These data suggest that the present method can be applicable to routine assay for benzodiazepines in the clinical setting. 相似文献
934.
Nobuhito Maru Takaaki Nomura Joe Sato Masato Yamanaka 《The European Physical Journal C - Particles and Fields》2010,66(1-2):283-287
We investigate Higgs boson production process via gluon fusion at LHC in our six-dimensional universal extra dimension model compactified on a spherical orbifold S 2/Z 2. We find a striking result that the Higgs production cross section in our model is predicted to have 30(10)% enhancement compared to the predictions of the Standard Model (the minimal universal extra dimension model) for the compactification scale of order 1 TeV. 相似文献
935.
Junji Hisano Kazunori Nakayama Shohei Sugiyama Tomohiro Takesako Masato Yamanaka 《Physics letters. [Part B]》2010
We propose an extended version of the gauge-mediated SUSY breaking models where extra SUL(2) doublets and singlet field are introduced. These fields are assumed to be parity-odd under an additional matter parity. In this model, the lightest parity-odd particle among them would be dark matter in the Universe. In this Letter, we discuss direct detection of the dark matter and the collider signatures of the model. 相似文献
936.
Summary In order to evaluate human carcinogenic risks, genotoxicity data such as animal cancer bioassay are often not available. In
this study, to assess the relevance of indicator of carcinogenic risks, we used the “molecular diversity approach” to estimate
the genotoxicity based upon Salmonella genotoxicity test using the umu test and systemic toxicity data of the 82 environmental chemicals predicted by neural network
simulation. The 82 environmental chemicals were randomly selected for this study according to the production and usage in
Japan. Even in this challenging trial for QSTR (Quantitative Structure Toxicity Relationship) study, approaches using artificial
neural networks can account for about 94% of the variation in the genotoxicity results derived by the umu-test. 相似文献
937.
We generalize the experimental success criterion for quantum teleportation (memory) in continuous-variable quantum systems to be suitable for a non-unit-gain condition by considering attenuation (amplification) of the coherent-state amplitude. The new criterion can be used for a nonideal quantum memory and long distance quantum communication as well as quantum devices with amplification process. It is also shown that the framework to measure the average fidelity is capable of detecting all Gaussian channels in the quantum domain. 相似文献
938.
We discuss the cosmological evolution of a brane in the D(>6)-dimensional black brane spacetime in the context of the Kaluza–Klein (KK) braneworld scheme, i.e., to consider KK compactification on the brane. The bulk spacetime is composed of two copies of a patch of D -dimensional black three-brane solution. The near-horizon geometry is given by AdS5×S(D−5) while in the asymptotic infinity the spacetime approaches D-dimensional Minkowski. We consider the brane motion from the near-horizon region toward the spatial infinity, which induces cosmology on the brane. As is expected, in the early times, namely when the brane is located in the near-horizon region, the effective cosmology on the brane coincides with that in the second Randall–Sundrum (RS II) model. Then, the brane cosmology starts to deviate from the RS type one since the dynamics of KK compactified dimensions becomes significant. We find that the brane Universe cannot reach the asymptotic infinity, irrespectively of the components of matter on the brane. 相似文献
939.
Myostatin preferentially down-regulates the expression of fast 2x myosin heavy chain in cattle 总被引:1,自引:0,他引:1
Hayashi S Miyake M Watanabe K Aso H Hayashi S Ohwada S Yamaguchi T 《Proceedings of the Japan Academy. Series B, Physical and biological sciences》2008,84(8):354-362
Myostatin is involved in an inhibitor of muscular growth and differentiation. Myoblasts derived from double-muscled Japanese shorthorn cattle (DM myoblasts) with absence of functional myostatin had higher abilities to proliferate and differentiate than myoblasts derived from normal-muscled cattle (NM myoblasts). In DM myoblasts, mRNA expressions of fetal myosin heavy chain (MyHC) in growth medium and of fast 2a and 2x MyHC in fusion medium were significantly greater than that in NM myoblasts. No significant difference existed in expressions of embryonic and slow MyHC mRNA between DM and NM myoblasts. The expression of MyoD mRNA was suppressed in myoblasts by administration of myostatin. Two cloned DM myoblast strains (DMc) were established. Addition of myostatin for DMc resulted in less myotube formation and suppression of mRNA expression of fast 2x MyHC. These findings suggest that the endogenous myostatin preferentially down-regulates the expression of the fast 2x MyHC and participates in differentiation of myofiber types during early bovine myogenesis. 相似文献
940.
The most annoying problem relating to the sensitivity of mask inspection systems is the encountering of false signals arising
from nuisance defects. In order to overcome this problem, we have previously proposed a new algorithm for die-to-wafer-like
image (D-to-WI) in real time. This paper describes the optimum mask inspection optics for the D-to-WI mask inspection. We
examine the optimum mask inspection optics with numerical simulation for various numerical apertures (NAs) and partial coherence
factors (σ) in these optics. The simulated result shows that the optimum mask inspection optics for the D-to-WI mask inspection has
NA 0.9 and σ = 0.95 for an ArF-6%-phase shift mask (PSM) 260/260 nm line/space pattern on the mask plane, in which the 193 nm-ArF scanner
has NA 0.93, σ = 0.92 − 0.92/0.3 annular illumination, reduction factor of ×4, and circular polarization incident light. 相似文献