全文获取类型
收费全文 | 10791篇 |
免费 | 561篇 |
国内免费 | 36篇 |
专业分类
电工技术 | 142篇 |
综合类 | 22篇 |
化学工业 | 1801篇 |
金属工艺 | 338篇 |
机械仪表 | 590篇 |
建筑科学 | 169篇 |
矿业工程 | 6篇 |
能源动力 | 371篇 |
轻工业 | 641篇 |
水利工程 | 38篇 |
石油天然气 | 15篇 |
无线电 | 1753篇 |
一般工业技术 | 1874篇 |
冶金工业 | 2677篇 |
原子能技术 | 149篇 |
自动化技术 | 802篇 |
出版年
2024年 | 8篇 |
2023年 | 115篇 |
2022年 | 154篇 |
2021年 | 283篇 |
2020年 | 217篇 |
2019年 | 184篇 |
2018年 | 245篇 |
2017年 | 268篇 |
2016年 | 313篇 |
2015年 | 229篇 |
2014年 | 342篇 |
2013年 | 547篇 |
2012年 | 561篇 |
2011年 | 681篇 |
2010年 | 494篇 |
2009年 | 512篇 |
2008年 | 485篇 |
2007年 | 382篇 |
2006年 | 335篇 |
2005年 | 314篇 |
2004年 | 278篇 |
2003年 | 247篇 |
2002年 | 259篇 |
2001年 | 214篇 |
2000年 | 205篇 |
1999年 | 269篇 |
1998年 | 936篇 |
1997年 | 545篇 |
1996年 | 374篇 |
1995年 | 228篇 |
1994年 | 220篇 |
1993年 | 221篇 |
1992年 | 56篇 |
1991年 | 73篇 |
1990年 | 47篇 |
1989年 | 48篇 |
1988年 | 55篇 |
1987年 | 50篇 |
1986年 | 32篇 |
1985年 | 29篇 |
1984年 | 12篇 |
1983年 | 15篇 |
1982年 | 18篇 |
1981年 | 27篇 |
1980年 | 29篇 |
1979年 | 7篇 |
1977年 | 72篇 |
1976年 | 122篇 |
1975年 | 10篇 |
1974年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
Calculation of Mass Attenuation Coefficients of Beta Particles 总被引:1,自引:0,他引:1
Yi C.Y.; Han H.S.; Cho W.K.; Park U.J.; Jun J.S.; Chai H.S. 《Radiation protection dosimetry》1998,78(3):221-229
32.
33.
34.
MM Haglund MS Grady PM Kanev EG Pavlin TA Mayberg HR Winn 《Canadian Metallurgical Quarterly》1994,11(5):623-627
Using an illustrative case of severe closed head injury that resulted in a posterior fossa epidural hematoma (EDH) and supratentorial epidural/subdural hematomas (SDH), the massive blood losses associated with operative repair of the torn sigmoid sinus and the significant fluid losses associated with refractory diabetes insipidus were treated by the intraoperative use of the Rapid Infusion System (RIS, Haemonetics). The RIS can rapidly infuse warm blood, crystalloid, or colloid at rates up to 1.5 L/min, thereby limiting the commonly associated hypotension, hypothermia, and coagulopathies. During the suboccipital craniectomy for evacuation of the EDH and repair of the sigmoid sinus, the patient required 18 units of blood replacement secondary to a large tear in the sigmoid sinus. During a separate craniotomy for evacuation of the SDH, the patient also developed diabetes insipidus, which increased the operative fluid replacement to 39 L. Despite these massive blood and fluid losses, the RIS limited the hypotension to less than 2 min and prevented hypothermia and the frequently associated coagulopathies. When used in a neurosurgical setting associated with massive blood and/or fluid losses, the RIS accomplishes three important objectives: (1) rapid infusion of intravenous fluids for maintaining perfusion pressure, (2) rapid warming of fluids despite high intravenous infusion rates of cold crystalloids, thereby preventing intraoperative hypothermia, and (3) continuous monitoring of infusion rates and totals. 相似文献
35.
36.
A chimeric dopamine transporter (DAT) cDNA encoding mutant human DAT (hDAT) protein in which the intracellular carboxyl-terminal tail is replaced by that of the bovine dopamine transporter (bDAT) was constructed. The chimeric hDAT cDNA was expressed in COS-7 cells, and [3H]dopamine and [3H]MPP+ uptake and [3H]CFT binding capacities were assessed. Substrate transport and ligand binding of bDAT were reduced by 32-43% as a result of substitution of the carboxyl tail in hDAT, suggesting that the functional characteristics of bDAT arise from differences in the carboxyl tail between human and bovine DAT. Thus, it appears that the sequences encoded within the carboxyl terminal of DAT would be one of the important determinants for its functions. 相似文献
37.
We provide evidence that dopamine receptors differentially modulate tyrosine hydroxylase and aromatic L-amino acid decarboxylase in the mouse striatum. The dopamine D1 receptor family (D1-like) antagonist, R(+)-7-chloro-8-hydroxy-3-methyl-1-phenyl-2,3,4,5-tetrahydro-1 H-3-benazepine (SCH 23390), elevated aromatic L-amino acid decarboxylase activity and protein content in striatum, as well as the mRNA for the enzyme in midbrain. The dopamine D1-like receptor agonist, (+/-)-1-phenyl-2,3,4,5-tetrahydro-(1 H)-3-benzazepine-7,8-diol (SKF 38393), had no effect on aromatic L-amino acid decarboxylase. The dopamine D1-like drugs had no effect on tyrosine hydroxylase. In contrast, the dopamine D2 receptor family (D2-like) antagonists haloperidol and spiperone elevated both tyrosine hydroxylase and aromatic L-amino acid decarboxylase activities. The increase in aromatic L-amino acid decarboxylase activity was accompanied by elevated enzyme protein content but not mRNA. The dopamine D2-like receptor agonists, bromocriptine, quinpirole and (+/-)-7-hydroxydipropylaminotetralin (7-OH-DPAT), all decreased striatal tyrosine hydroxylase. Under the conditions used, bromocriptine and 7-OH-DPAT, but not quinpirole, decreased aromatic L-amino acid decarboxylase activity of striatum. Both the dopamine D1- and D2-like receptor antagonists enhanced the turnover of striatal dopamine to differing degrees, as judged by the ratio of acid metabolites of dopamine to dopamine. Taken together our results indicate that aromatic L-amino acid decarboxylase can be modulated independently of tyrosine hydroxylase. 相似文献
38.
Hoon C. Park Chahngmin Cho Sung W. Lee 《International journal for numerical methods in engineering》1995,38(24):4101-4122
The present paper describes an assumed strain finite element model with six degrees of freedom per node designed for geometrically non-linear shell analysis. An important feature of the present paper is the discussion on the spurious kinematic modes and the assumed strain field in the geometrically non-linear setting. The kinematics of deformation is described by using vector components in contrast to the conventional formulation which requires the use of trigonometric functions of rotational angles. Accordingly, converged solutions can be obtained for load or displacement increments that are much larger than possible with the conventional formulation with rotational angles. In addition, a detailed study of the spurious kinematic modes and the choice of assumed strain field reveals that the same assumed strain field can be used for both geometrically linear and non-linear cases to alleviate element locking while maintaining kinematic stability. It is strongly recommended that the element models, described in the present paper, be used instead of the conventional shell element models that employ rotational angles. 相似文献
39.
40.