全文获取类型
收费全文 | 11398篇 |
免费 | 373篇 |
国内免费 | 32篇 |
专业分类
化学 | 7572篇 |
晶体学 | 73篇 |
力学 | 332篇 |
综合类 | 6篇 |
数学 | 1450篇 |
物理学 | 2370篇 |
出版年
2023年 | 82篇 |
2022年 | 204篇 |
2021年 | 358篇 |
2020年 | 256篇 |
2019年 | 278篇 |
2018年 | 271篇 |
2017年 | 223篇 |
2016年 | 470篇 |
2015年 | 340篇 |
2014年 | 392篇 |
2013年 | 718篇 |
2012年 | 788篇 |
2011年 | 825篇 |
2010年 | 622篇 |
2009年 | 602篇 |
2008年 | 746篇 |
2007年 | 695篇 |
2006年 | 555篇 |
2005年 | 451篇 |
2004年 | 391篇 |
2003年 | 341篇 |
2002年 | 285篇 |
2001年 | 220篇 |
2000年 | 173篇 |
1999年 | 121篇 |
1998年 | 115篇 |
1997年 | 101篇 |
1996年 | 98篇 |
1995年 | 73篇 |
1994年 | 87篇 |
1993年 | 81篇 |
1992年 | 82篇 |
1991年 | 67篇 |
1990年 | 49篇 |
1989年 | 37篇 |
1988年 | 45篇 |
1987年 | 35篇 |
1986年 | 37篇 |
1985年 | 55篇 |
1984年 | 42篇 |
1983年 | 37篇 |
1982年 | 30篇 |
1981年 | 37篇 |
1980年 | 40篇 |
1979年 | 32篇 |
1978年 | 38篇 |
1977年 | 18篇 |
1976年 | 23篇 |
1975年 | 25篇 |
1973年 | 17篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
171.
Alves GA Amato S Anjos JC Appel JA Astorga J Bracker SB Cremaldi LM Dagenhart WD Darling CL Dixon RL Errede D Fenker HC Gay C Green DR Jedicke R Karchin PE Kennedy C Kwan S Lueking LH de Mello Neto JR Metheny J Milburn RH de Miranda JM da Motta Filho H Napier A Passmore D Rafatian A dos Reis AC Ross WR Santoro AF Sheaff M Souza MH Spalding WJ Stoughton C Streetman ME Summers DJ Takach SF Wallace A Wu Z 《Physical review letters》1996,77(12):2388-2391
172.
173.
Beltrão EI Correia MT Figueredo-Silva J Coelho LC 《Applied biochemistry and biotechnology》1998,74(3):125-134
The phenomenon of altered carbohydrates in transformed cell surfaces has been studied through histochemical techniques using
lectins. Specific binding patterns to normal and transformed mammary tissues were evaluated by Isoform 1 fromCratylia mollis lectin (Cra Iso 1). Protocols using a direct method, incubation of Cra Iso I conjugated to peroxidase (Cra Iso 1-Per) with
mammary tissues, followed by diaminobenzidine and hydrogen peroxidase interaction, were performed. Neoplastic tissues, marked
by Cra Iso 1, showed a higher intensity of staining than normal ones, in comparison withCanavalia ensiformis lectin, Concanavalin A (Con A), conjugated to peroxidase (Con A-Per). The assay with Cra Iso 1 also indicated a possible
utilization of this lectin to characterize normal and transformed mammary cells. 相似文献
174.
The synthesis of tetracyclic polyhydroxyquinones 5a and 5b was achieved through a sequence involving two Diels-Alder reactions with 1-methoxy-1,3-cyclohexadiene: the first with 2-(p-tolylthio)naphthazarin and the second on the resulting tricyclic derivative previously transformed into a (p-tolylsulfinyl)naphthazarin. The success of this strategy stemmed from the efficient remote regiocontrol exerted by the thioether substituent in the first step. 相似文献
175.
Jürgen Bokowski António Guedes de Oliviera Ulrich Thiemann António Veloso da Costa 《Geometriae Dedicata》1996,63(1):25-43
We prove a conjecture of Las Vergnas in dimensions d7: The matroid of the d-dimensional cube C
d
has a unique reorientation class. This extends a result of Las Vergnas, Roudneff and Salaün in dimension 4. Moreover, we determine the automorphism group G
d
of the matroid of the d-cube C
d
for arbitrary dimension d, and we discuss its relation to the Coxeter group of C
d
. We introduce matroid facets of the matroid of the d-cube in order to evaluate the order of G
d
. These matroid facets turn out to be arbitrary pairs of parallel subfacets of the cube. We show that the Euclidean automorphism group W
d
is a proper subgroup of the group G
d
of all matroid symmetries of the d-cube by describing genuine matroid symmetries for each Euclidean facet. A main theorem asserts that any one of these matroid symmetries together with the Euclidean Coxeter symmetries generate the full automorphism group G
d
. For the proof of Las Vergnas' conjecture we use essentially these symmetry results together with the fact that the reorientation class of an oriented matroid is determined by the labeled lower rank contractions of the oriented matroid. We also describe the Folkman-Lawrence representation of the vertex figure of the d-cube and a contraction of it. Finally, we apply our method of proof to show a result of Las Vergnas, Roudneff, and Salaün that the matroid of the 24-cell has a unique reorientation class, too. 相似文献
176.
177.
178.
179.
L. Fernandes C. Pagano Gonçalves da Silva 《Journal of Radioanalytical and Nuclear Chemistry》1993,172(2):313-318
The radiopharmaceutical201TlCl(thallium-201 chloride) is used in nuclear medicine for myocardial visualization. The solution of201TlCl was prepared using201Tl obtained by irradiating a natural mercury target with protons from the CV-28 cyclotron installed at IPEN-CNEN/SP. This solution was subjected to different quality control processes required for its use in medicine. Some of these controls concerned the determination of the radionuclidic impurities:200Tl,202Tl and203Hg; the chemical identification of201Tl+; the hydrazine concentration, mercury contamination and the presence of phosphate. Furthermore. the biological distribution in Wistar rats and tests for sterility, pyrogenicity and toxicity were carried out. It was verified that the solution obtained was in the form of thallous chloride. This radiopharmaceutical gave good heart images in animals but due to the high levels of200Tl and202Tl its use in humans is not possible unless enriched202Hg is used as target in the irradiation. 相似文献
180.
Juan J. Nuño Ballesteros 《Geometriae Dedicata》1993,47(3):241-254
We study the singularities of the tangent developable of a generic curve in 3 and prove that if the curve has no torsion zero points, the number of triple points of that surface must be even. 相似文献