全文获取类型
收费全文 | 180128篇 |
免费 | 14032篇 |
国内免费 | 8946篇 |
专业分类
化学 | 73163篇 |
晶体学 | 1385篇 |
力学 | 11031篇 |
综合类 | 310篇 |
数学 | 39405篇 |
物理学 | 43031篇 |
综合类 | 34781篇 |
出版年
2024年 | 512篇 |
2023年 | 2049篇 |
2022年 | 3267篇 |
2021年 | 3658篇 |
2020年 | 3468篇 |
2019年 | 3058篇 |
2018年 | 12735篇 |
2017年 | 12457篇 |
2016年 | 9736篇 |
2015年 | 4896篇 |
2014年 | 5404篇 |
2013年 | 6493篇 |
2012年 | 11497篇 |
2011年 | 18231篇 |
2010年 | 11328篇 |
2009年 | 11359篇 |
2008年 | 12340篇 |
2007年 | 14254篇 |
2006年 | 4996篇 |
2005年 | 5523篇 |
2004年 | 4761篇 |
2003年 | 4583篇 |
2002年 | 3401篇 |
2001年 | 2485篇 |
2000年 | 2509篇 |
1999年 | 3438篇 |
1998年 | 3005篇 |
1997年 | 3032篇 |
1996年 | 2959篇 |
1995年 | 2421篇 |
1994年 | 2095篇 |
1993年 | 1823篇 |
1992年 | 1542篇 |
1991年 | 1373篇 |
1990年 | 1208篇 |
1989年 | 1028篇 |
1988年 | 873篇 |
1987年 | 626篇 |
1986年 | 464篇 |
1985年 | 307篇 |
1984年 | 193篇 |
1983年 | 141篇 |
1982年 | 123篇 |
1981年 | 108篇 |
1980年 | 112篇 |
1979年 | 79篇 |
1978年 | 65篇 |
1977年 | 58篇 |
1976年 | 46篇 |
1973年 | 54篇 |
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
21.
Duan Jinqing Liu Hongbin Zhang Xinian Lu Hongmin Gou Ai Liu Zheng Wang Tao Ge Rili 《中国工程科学》2006,4(2):183-186
Study Objective: To compare and analyze the changes of the pulmonary-artery pressure of the migrants coming from different elevation in the hypoxic environment of 4636 - 4907 m extreme altitude. To explore the susceptibility to hypoxic pulmonary-artery hypertension (PH) in the subjects from different altitude and profession. Methods: By using Color Doppler Ultmsonography (CDU), measuring the pulmonary-artery pressure of 207 healthy men, who had continuously being lived and worked at the extreme altitude for more than six months, and then were divided into three groups according to their profession and the altitude of original living place. Results: There was a significant difference in the outcomes of pulmonary-artery pressure from the 3 groups. Conclusions: Altitude of original living place, labor intensity are some of factors that impact the pulmonary-artery pressure of the people who exposure to a hypoxic environment. The pulmonary- artery pressure of person without strenuously physical work experience was more sensitive to hypoxic surroundings than that of labor workers. It was not always the fact at an extreme altitude that the moderate altitude mountaineers were superior to other migrants from a lower altitude or plain. The higher PH was found in the groups of the moderate altitude mountaineers and labor workers. It is unlikely certain that one with PH would surfer from HAPE. 相似文献
22.
Christiane Albrecht 《Analytical and bioanalytical chemistry》2008,390(5):1223-1224
23.
24.
A two-step swelling procedure was adopted to synthesize mono-dispersed and highly cross-linked poly (St-divinylbenzene) particles
with PSt micro-spheres (1.80 μm in diameter). The PSt micro-spheres were prepared by a dispersion polymerization method and
used as seeds. The effects of monomer concentration, ratio of ethanol to water, swelling reagents, crosslinking reagents,
swelling temperature and agitation speed on particle size were investigated in detail. The morphologies and size distributions
of these micro-spheres were examined by SEM and particle size analysis (PSA). The T
g of the micro-spheres was measured by DSC. The results indicate that the particles (6.20 μm in diameter) exhibit excellent
mono dispersed property and high crosslinking degree when the concentration of the swelling reagent was 25%, the concentration
of the crosslinking reagents was 23%, the swelling temperature was 30°C and the stirring speed was 150 r/min.
__________
Translated from Chinese Journal of Applied Chemistry, 2007, 24(11): 1289–1294 相似文献
25.
J. Song H. Jiang Z.J. Liu D.Y. Khang Y. Huang J.A. Rogers C. Lu C.G. Koh 《International Journal of Solids and Structures》2008,45(10):3107-3121
A finite-deformation theory is developed to study the mechanics of thin buckled films on compliant substrates. Perturbation analysis is performed for this highly nonlinear system to obtain the analytical solution. The results agree well with experiments and finite element analysis in wavelength and amplitude. In particular, it is found that the wavelength depends on the strain. Based on the accurate wavelength and amplitude, the membrane and peak strains in thin films, and stretchability and compressibility of the system are also obtained analytically. 相似文献
26.
Chengzhi Qi Mingyang Wang Qihu Qian Jianjie Chen 《Moscow University Mechanics Bulletin》2008,63(5):113-121
The formation mechanisms for the structural hierarchy in geological media are discussed. It is shown that the formation of such a hierarchy is caused by certain external and internal circumstances. The first ones consist in the fact that, because of external actions, the Earth’s poles continuously execute the translational and rotational motions responsible for a regular structure of rock fracture and for the appearance of the scale factor √2. The second ones consist in the fact that, under the action of many random factors and because of external actions, during the formation of geological media there appear dissipative structures and, hence, some self-similar fractal structures are formed. 相似文献
27.
The title compound, [Cd(SeCN)2(pyCN)2]∞, adopts an extended one‐dimensional chain structure in which the neighboring cadmium atoms are bridged by two selenocyanate ions. The central cadmium atom has a distorted octahedral geometry defined by two isonicotinonitrile and four selenocyanate ions in a 4N2Se fashion. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
28.
In mononuclear HgI2[(C5H4N)3N], mercury is tetrahedrally coordinated by two nitrogen atoms of a tris(2‐pyridyl)amine ligand and two iodides. The coordination moieties are connected by weak intermolecular Hg(II)···I interactions to give a one‐dimensional structure. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
29.
Howard Robinson 《Acta Analytica》2005,20(3):7-10
Nicholas Nathan tries to resist the current version of the causal argument for sense-data in two ways. First he suggests that,
on what he considers to be the correct re-construction of the argument, it equivocates on the sense of proximate cause. Second
he defends a form of disjunctivism, by claiming that there might be an extra mechanism involved in producing veridical hallucination,
that is not present in perception. I argue that Nathan’s reconstruction of the argument is not the appropriate one, and that,
properly interpreted, the argument does not equivocate on proximate cause. Furthermore, I claim that his postulation of a
modified mechanism for hallucinations is implausibly ad hoc. 相似文献
30.
The original article to which this Erratum refers was published in Journal of Graph Theory 47:129–146,2004 . 相似文献