全文获取类型
收费全文 | 10621篇 |
免费 | 266篇 |
国内免费 | 48篇 |
专业分类
化学 | 7835篇 |
晶体学 | 116篇 |
力学 | 142篇 |
数学 | 545篇 |
物理学 | 2297篇 |
出版年
2022年 | 73篇 |
2021年 | 84篇 |
2020年 | 114篇 |
2019年 | 150篇 |
2018年 | 98篇 |
2017年 | 80篇 |
2016年 | 186篇 |
2015年 | 176篇 |
2014年 | 234篇 |
2013年 | 519篇 |
2012年 | 542篇 |
2011年 | 629篇 |
2010年 | 346篇 |
2009年 | 385篇 |
2008年 | 639篇 |
2007年 | 591篇 |
2006年 | 649篇 |
2005年 | 585篇 |
2004年 | 559篇 |
2003年 | 443篇 |
2002年 | 448篇 |
2001年 | 225篇 |
2000年 | 221篇 |
1999年 | 141篇 |
1998年 | 124篇 |
1997年 | 123篇 |
1996年 | 125篇 |
1995年 | 96篇 |
1994年 | 99篇 |
1993年 | 130篇 |
1992年 | 121篇 |
1991年 | 107篇 |
1990年 | 81篇 |
1989年 | 72篇 |
1988年 | 96篇 |
1987年 | 103篇 |
1986年 | 116篇 |
1985年 | 157篇 |
1984年 | 139篇 |
1983年 | 60篇 |
1982年 | 121篇 |
1981年 | 127篇 |
1980年 | 110篇 |
1979年 | 98篇 |
1978年 | 81篇 |
1977年 | 90篇 |
1976年 | 75篇 |
1975年 | 54篇 |
1974年 | 61篇 |
1973年 | 47篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
Recently published data on thep T dependence of the angular distributions of muon pairs produced in collisions of negative pions with deuterium and tungsten nuclei reveal an unexpected tendency. We show that the quantum statistical approach involving expansions in terms of coherent states leads in this case to an exact, non-perturbative result which in the lowest order approximation describes the observed trends with sufficient accuracy. In this procedure, the non-vanishing correlations between the coordinates and momenta of dimuons play a decisive role. 相似文献
12.
This paper presents a new scheduling method for manufacturing system based on the Timed Petri Net model and a reactive fast graph search algorithm. The following two typical problems are addressed in this paper. (1) Minimization of the maximum completion time. (2) Minimization of the total tardiness. As for the problem (1), a new search algorithm which combines the RTA∗ and a rule-based supervisor is proposed. As for problem (2), the original Petri Net model is converted to its reverse model and the algorithm developed for the problem (1) is applied, regarding the due date as the starting time in the reverse model. Some numerical experiments are carried out to demonstrate usefulness of our algorithm. 相似文献
13.
14.
Two experiments were conducted to evaluate the equivalence of noise annoyance scales and questions recommended by Team 6 (Community Response to Noise) of ICBEN for English and Japanese, two strikingly different languages. The first experiment was conducted with bilingual subjects in order to test a key assumption of the method established by ICBEN Team 6 for the development of equivalent noise annoyance scales: subjects who speak different languages interpret the concept of “highest degree” of annoyance similarly. The results indicate that English- and Japanese-speaking subjects do interpret the “highest degree” similarly. The second experiment tested for effects of wording differences. English- and Japanese-speaking subjects were presented with noise annoyance questions of one of three format types. The first type was similar to the question format recommended by ICBEN Team 6. It focused on the degree to which a given noise would “bother, disturb, or annoy” the subject. The second asked subjects to evaluate the “bothersome, annoying, or disturbing” quality of the noise. The third asked how much the noise would “worry, irritate, or concern” the subject. No significant difference was found in responses to the three formats when subjects evaluated noise in laboratory conditions. 相似文献
15.
The rate coefficient for the reaction of CCl3 radicals with ozone has been measured at 303 ± 2 K. The CCl3 radicals were generated by the pulsed laser photolysis of carbon tetrachloride at 193 nm. The time profile of CCl3 concentration was monitored with a photoionization mass spectrometer. Addition of the O3–O2 mixture to this system caused a decay of the CCl3 concentration because of the reactions of CCl3 + O3 → products (5) and CCl3 + O2 → products (4). The decay of signals from the CCl3 radical was measured in the presence and absence of ozone. In the absence of ozone, the O3–O2 mixture was passed through a heated quartz tube to convert the ozone to molecular oxygen. Since the rate coefficient for the reaction of CCl3 + O2 could be determined separately, the absolute rate coefficient for reaction ( 5 ) was obtained from the competition among these reactions. The rate coefficient determined for reaction ( 5 ) was (8.6 ± 0.5) × 10?13 cm3 molecule?1 s?1 and was also found to be independent of the total pressure (253–880 Pa of N2). This result shows that the reaction of CCl3 with O3 cannot compete with its reaction with O2 in the ozone layer. © 2003 Wiley Periodicals, Inc. Int J Chem Kinet 35: 310–316, 2003 相似文献
16.
Takashi Kishimoto 《Journal of Pure and Applied Algebra》2007,208(1):189-204
Let X?(T,D) be a compactification of an affine 3-fold X into a smooth projective 3-fold T such that the (reduced) boundary divisor D is SNC. In this paper, as an affine counterpart to the work due to S. Mori (cf. [S. Mori, Threefolds whose canonical bundles are not numerically effective, Ann. of Math. 116 (1982) 133-176]), we shall classify (K+D)-negative extremal rays on T. In particular, if such an extremal ray R=R+[C] intersects K non-negatively, we shall describe the log flips and divisorial contractions appearing explicitly. 相似文献
17.
Endoscopic Observation of Tissue by Narrowband Illumination 总被引:6,自引:0,他引:6
Kazuhiro Gono Kenji Yamazaki Nobuyuki Doguchi Tetsuo Nonami Takashi Obi Masahiro Yamaguchi Nagaaki Ohyama Hirohisa Machida Yasushi Sano Shigeaki Yoshida Yasuo Hamamoto Takao Endo 《Optical Review》2003,10(4):211-215
We propose a new illumination method for a medical endoscope: narrow band imaging (NBI), in which the spectral bandwidth of the filtered light is narrowed. To confirm how the spectral specifications of the filtered light influence a reproduced image, an experiment was conducted observing the endoscopic images of the back mucosa of a human tongue. In addition, the effect of NBI on endoscopic images was investigated through preliminary clinical tests in colonoscopy and upper gastrointestinal endoscopy. It has been shown that NBI can enhance the capillary pattern and the crypt pattern on the mucosa. These patterns are useful features for diagnosing an early cancer. 相似文献
18.
19.
20.
Lasing conditions for He I in a cold recombining helium plasma are numerically discussed including optical thicknesses. A collisional radiative model is used to calculate population densities. We discuss the effect of self absorptions by the background residual gas on the lasing conditions quantitatively. The optical thickness is essential in the calculation and affects the population inversions between level pairs of the singlet state drastically, while those of the triplet state are not affected very much. In the optically thin plasma, the laser lower levels of the singlet state depopulate mainly through radiative transitions. On the other hand, they depopulate mainly through electron collisional deexcitations in the optically thick plasma. Results of the calculations are verified by the spectroscopic observations of an arc-heated magnetically trapped expanding plasma jet generator which we developed. The requirement for the background pressure in which the lasing is possible is discussed quantitatively. 相似文献