全文获取类型
收费全文 | 10111篇 |
免费 | 640篇 |
国内免费 | 230篇 |
专业分类
电工技术 | 423篇 |
综合类 | 1627篇 |
化学工业 | 1357篇 |
金属工艺 | 201篇 |
机械仪表 | 762篇 |
建筑科学 | 522篇 |
矿业工程 | 248篇 |
能源动力 | 124篇 |
轻工业 | 351篇 |
水利工程 | 198篇 |
石油天然气 | 1042篇 |
武器工业 | 208篇 |
无线电 | 372篇 |
一般工业技术 | 366篇 |
冶金工业 | 2938篇 |
原子能技术 | 30篇 |
自动化技术 | 212篇 |
出版年
2023年 | 8篇 |
2022年 | 8篇 |
2021年 | 123篇 |
2020年 | 110篇 |
2019年 | 95篇 |
2018年 | 245篇 |
2017年 | 249篇 |
2016年 | 232篇 |
2015年 | 118篇 |
2014年 | 298篇 |
2013年 | 171篇 |
2012年 | 331篇 |
2011年 | 179篇 |
2010年 | 63篇 |
2009年 | 99篇 |
2008年 | 93篇 |
2007年 | 718篇 |
2006年 | 1088篇 |
2005年 | 575篇 |
2004年 | 831篇 |
2003年 | 1056篇 |
2002年 | 419篇 |
2001年 | 254篇 |
2000年 | 315篇 |
1999年 | 257篇 |
1998年 | 980篇 |
1997年 | 569篇 |
1996年 | 370篇 |
1995年 | 202篇 |
1994年 | 145篇 |
1993年 | 198篇 |
1992年 | 26篇 |
1991年 | 29篇 |
1990年 | 38篇 |
1989年 | 37篇 |
1988年 | 47篇 |
1987年 | 40篇 |
1986年 | 36篇 |
1985年 | 50篇 |
1984年 | 16篇 |
1983年 | 22篇 |
1982年 | 16篇 |
1981年 | 13篇 |
1980年 | 32篇 |
1979年 | 5篇 |
1978年 | 8篇 |
1977年 | 51篇 |
1976年 | 99篇 |
1974年 | 3篇 |
1973年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
22.
M Pomerantz JR Denton GA Huitt JM Brown LA Powell MD Iseman 《Canadian Metallurgical Quarterly》1996,62(4):990-993
BACKGROUND: In a series of 229 patients infected with mycobacterial organisms, we noted a specific female phenotype that involves isolated infections of the middle lobe and lingula. METHODS: Thirteen patients were found to have infections of the middle lobe, lingula, or both. All of them were infected with Mycobacterium other then Mycobacterium tuberculosis, all were women, 12 of the 13 were slender, and most had variable combinations of skeletal abnormalities. All underwent resection of the middle lobe, lingula, or both. RESULTS: There were no operative deaths. Only 2 patients have had reactivation requiring additional antibiotic therapy. All patients have had a decreased number of pulmonary infections in the postoperative period. Anatomic findings at operation included a complete major fissure and at least a partially complete minor fissure with middle lobe resections or an elongated lingula. CONCLUSIONS: Mycobacterial infection of the middle lobe and lingula is primarily a disease of asthenic women and is often associated with skeletal abnormalities and complete fissures or an elongated lingula. We recommend that surgical intervention be performed early once the condition is identified. 相似文献
23.
We tested the hypothesis that adaptations in peripheral arterial vasoreactivity are induced by exercise training. Male rats were trained to run on a treadmill at 30 m/min (15 degrees incline) for 1 h/day 5 days/wk for 10-12 wk. Efficacy was indicated by a 51% increase (P < 0.05) in citrate synthase activity in soleus muscle of exercise-trained (ET) rats compared with that of sedentary (SED) control rats. Responses to vasoactive compounds were examined in vitro using rings of abdominal aorta. Maximal isometric contractile tension evoked by KCl, norepinephrine (NE), and phenylephrine were not different between groups; sensitivity to phenylephrine was also not different between groups. However, sensitivity was lower for both KCl and NE in vessels from ET animals. Endothelium removal did not influence KCl sensitivity but did abolish the difference in NE sensitivity of vessel segments between ET and SED animals. Maximal vasodilator responses induced by acetylcholine (ACh; NE or prostaglandin F2 alpha preconstriction) were greater in vessel rings from ET rats. However, dilatory responses by sodium nitroprusside (NE or prostaglandin F2 alpha preconstriction) and forskolin (NE preconstriction) were not different between groups, indicating that the augmented ACh-induced dilatory response resulted from an adaptation of the endothelium. Blockade of nitric oxide synthase activity diminished ACh-induced vasodilation by 79 and 100% in SED and ET rats, respectively. These results indicate that training alters vasomotor function in rat abdominal aortas through adaptations of both endothelium and smooth muscle. 相似文献
24.
25.
Q Hu M Trevisan Y Xu W Dong SA Berger SD Lyman MD Minden 《Canadian Metallurgical Quarterly》1995,95(6):2530-2538
The growth of human leukemic cells in culture and in vivo is dependent upon the presence of hematopoietic growth factors. Most populations of human leukemic acute myeloblastic leukemia (AML) cells express c-Kit on their surface and respond to Kit ligand (KL) in culture. To determine if this interaction was of potential significance in vivo we used a mouse model system. 32D cells, a murine IL-3-dependent myeloid cell line, were rendered KL responsive by transfection of the murine c-Kit. After injection of 32D or 32D-Kit cells into syngeneic hosts, animals bearing 32D-Kit cells, but not 32D cells, became moribund and were killed. These animals had circulating leukemic blast cells, infiltration of bone marrow, spleen, brain, liver, lung, and kidney. Cells recovered from some of the animals continued to be dependent upon IL-3 or KL for growth while in other cases the cells were factor independent. This model illustrates that the constitutive expression of c-Kit enhances the leukemic potential of 32D cells. The model will be useful for studying the progression of leukemia in vivo and testing whether interruption of the interaction of Kit and KL can affect the growth of leukemic cells. 相似文献
26.
MD Cohen ST Auringer JL Grosfeld CA Galliani NA Heerema 《Canadian Metallurgical Quarterly》1993,23(6):463-466
The purpose of this study is to present three patients with multifocal primary neuroblastoma, to review the literature, and describe the radiographic findings. SUBJECTS AND METHODS: Three children with multifocal neuroblastoma have been identified. The case histories and imaging findings in these patients are reviewed. RESULTS: Two children had synchronous and one child had metachronous multifocal primary neuroblastoma. The primary tumors were both in the abdomen in one patient, both in the chest in another patient, and in the chest and abdomen in the third patient. Evidence for multifocal origin of these tumors, rather than metastatic spread, is presented. CONCLUSION: Multifocal primary neuroblastomas can occur. The tumors maybe synchronous or metachronous. Awareness of this disorder may prevent errors in diagnosis and staging. Although not identified in our patients there is a strong familial incidence of neuroblastomas in those patients with multifocal tumors. 相似文献
27.
28.
Pulmonary surfactant is a complex mixture of lipids and proteins that functions to keep alveoli from collapsing at the end of expiration. Dipalmitoylphosphatidylcholine has been identified as the most important component for lowering surface tension at the air-liquid interface. Hydrophobic surfactant apoproteins, SP-B and SP-C, play essential roles in the biophysical functions of the surfactant phospholipids. Hydrophilic surfactant apoproteins (SP-A and SP-D) that are members of C-type lectin superfamily, interact with phospholipids and glycolipids and modulate host defense functions in the lung. SP-A also plays an important role in regulating phospholipid homeostasis in the alveolar spaces. Recent advances in genetics and molecular biology have clarified the structure-function relationship of surfactant apoproteins. 相似文献
29.
李永春 《湖南纺织高等专科学校学报》2006,16(3):93-97
王光祈的“少年中国”理想,是以“少年意大利”为基础,汲取五四时期社会主义思潮的积极成分而形成的。创造“少年中国”在“人”的方面,是从改造中国少年入手,同时注重青年学生与平民的改造,注重劳动阶级、智识阶级与资产阶级的改造与联合;在“事”的方面,积极开展社会事业和社会活动,且必须经过社会分工与国际分工。可见,他的这种理想是典型的社会改革主张,在早期带有无政府主义色彩,自始至终具有强烈的民族主义情感。 相似文献
30.