全文获取类型
收费全文 | 4003篇 |
免费 | 1篇 |
国内免费 | 1篇 |
专业分类
综合类 | 1篇 |
化学工业 | 11篇 |
机械仪表 | 1篇 |
建筑科学 | 3篇 |
轻工业 | 23篇 |
石油天然气 | 4篇 |
无线电 | 11篇 |
一般工业技术 | 9篇 |
冶金工业 | 3932篇 |
自动化技术 | 10篇 |
出版年
2013年 | 4篇 |
2011年 | 3篇 |
2010年 | 3篇 |
2009年 | 2篇 |
2008年 | 2篇 |
2007年 | 3篇 |
2006年 | 2篇 |
2005年 | 2篇 |
2004年 | 2篇 |
2003年 | 6篇 |
2001年 | 3篇 |
2000年 | 1篇 |
1999年 | 106篇 |
1998年 | 1188篇 |
1997年 | 658篇 |
1996年 | 465篇 |
1995年 | 219篇 |
1994年 | 207篇 |
1993年 | 223篇 |
1992年 | 25篇 |
1991年 | 68篇 |
1990年 | 62篇 |
1989年 | 57篇 |
1988年 | 52篇 |
1987年 | 56篇 |
1986年 | 43篇 |
1985年 | 44篇 |
1983年 | 11篇 |
1982年 | 19篇 |
1981年 | 23篇 |
1980年 | 32篇 |
1979年 | 4篇 |
1978年 | 10篇 |
1977年 | 102篇 |
1976年 | 260篇 |
1975年 | 5篇 |
1972年 | 1篇 |
1964年 | 1篇 |
1955年 | 7篇 |
1927年 | 2篇 |
1923年 | 1篇 |
1918年 | 1篇 |
1917年 | 2篇 |
1916年 | 1篇 |
1914年 | 3篇 |
1913年 | 1篇 |
1912年 | 2篇 |
1910年 | 2篇 |
1909年 | 2篇 |
1908年 | 3篇 |
排序方式: 共有4005条查询结果,搜索用时 15 毫秒
31.
Thiamine and thiamine triphosphate (TTP) values were assayed in various brain regions in 11 controls and 13 patients with subacute necrotizing encephalomyelopathy (SNE, Leigh disease). The TTP values of normal brain were 5% of the total thiamine value. The relative TTP (or % TTP) level was consistently low in the pons, midbrain, and cerebellum of all the SNE brains. Twenty-five percent of the SNE brains had normal TTP levels in the frontal region. The TTP values correlated with the degrees of pathologic involvement in all sampled regions of the brain except the cerebellum. The concentration of thiamine in the mammillary bodies exceeded its concentration elsewhere in both control and SNE brains. The finding of low TTP levels in morphologically abnormal regions supports the hypothesis that TTP deficiency is etiologically related to SNE. 相似文献
32.
Bacteriophage MX-1 is a virulent DNA phage for Myxococcus. The host range includes strains of Myxococcus xanthus, M. fulvus and M. virescens. The phage has a sedimentation coefficient (S degrees 20,w) of 1145S and a density of 1-531 g/ml. By using SDS-polyacrylamide gel electrophoresis, 23 phage proteins with apparent mol. wt. between 10000 and 150000 were resolved. Gel filtration in the presence of non-ionic detergent partially resolved the proteins. The fraction excluded from Sephadex G-100, fraction 1, contains two glycoproteins. Fraction 1 was resolved into three fractions (1-1, 1-2 and 1-3) by chromatography on Sephadex G-200. The glycoproteins were present in fraction 1-2; all the proteins from this fraction were derived from the phage tail. Comparison of the amino-acid, hexosamine and neutral-sugar compositions of the two glycoproteins showed that they are distinct molecular species; the smaller molecule is not a subunit of the larger. The significance of these findings is discussed and compared with the proteins of the tails of T-even phage of Escherichia coli. 相似文献
33.
We report here a model of submaximal spinal cord injury, employing direct thoracic cord compression in ferrets. This yields consistent and reproducible long term consequences on local cellular structure and on locomotive function. We show also that both the anatomical and functional losses can be measured objectively using simple techniques, and that useful long-tract mediated locomotion is preserved after severe axonal losses at the site of injury. 相似文献
34.
35.
36.
37.
Gamekeeper's thumb is due to complete rupture of the ulnar collateral ligament; it should be clinically differentiated from incomplete rupture. Methods of diagnosis and treatment of gamekeeper's thumb are described. The results in 10 cases of gamekeeper's thumb treated by surgery, with more than a one-year follow-up are evaluated. 相似文献
38.
Local and regional recurrences are frequent problems in breast cancer management. Radiation therapy is effective in producing long term remission. This study evaluates the results of radiation therapy of 215 patients with recurrent disease limited to the chest wall and/or regional lymph node areas. The local results showed complete control in 67% of cases (mean and median durations 32 months and 22 months, respectively), partial control in 24% of cases (mean and median 11 and 8 months, respectively) and no control in the remaining 9%. The radiation dose recommended for the treatment of recurrent mammary carcinoma is 5000 rads in 5 weeks for relatively small lesions. Supplementary local doses of 500-1000 rads in 1 week may be given to bulky lesions as necessary for residual disease. Although local relapse indicates a poor prognosis, it is by no means totally hopeless. Of 215 patients treated 44 (21%) survived 5 years and 10 (5%) survived 10 years following radiation therapy of recurrent disease. There were seven patients, or 3%, who were free of cancer at 5 to 15 years. Radiation therapy was valuable in controlling local lesions, and thus, in improving quality of survival, even in those patients who eventually died of metastatic disease. 相似文献
39.
The importance of various unsaturated fatty acid triglycerides to the repair of faulty skin barrier function was studied in essential fatty acid-deficient rats. Following cutaneous application of the pure triglycerides for up to 5 days, the hitherto high rate of transepidermal water loss, characteristic of essential fatty acid deficiency in rats, was reduced by the triglycerides of linoleic and gamma-linolenic acids. Incorporation of the applied fatty acids into the lecithin of the epidermis accompanied these changes in water loss, indicating that cutaneously applied triglycerides may be metabolized by the skin and incorporated into complex lipids. Other fatty acid triglycerides, including alpha-linolenic, dihomo-gamma-linolenic, arachidonic and omega-7-heneicosatrienoic acid, did not lower the rate of transepidermal water loss, although all were incorporated into epidermal structural lipids. The non-essential oleic acid also had no effect upon the rate of transepidermal water loss. These data suggest that of the two main essential fatty acids that occur in skin, linoleic acid and arachidonic acid, the former specifically plays an important role in regulating barrier function whereas the later may have a separate function, such as serving as a precursor of prostaglandins. 相似文献
40.
LA Sharzer CE Horton JE Adamson JH Carraway JB McCraw 《Canadian Metallurgical Quarterly》1976,3(3):495-509
The effect of prostaglandins (PGs) on the hepatic biotransformation of hexobarbital (Hechi) and p-chloro-N-methylaniline (PCMA) was determined in male rats. PCMA metabolism in slices was decreased by all PGs (PGA1, PGB1, PGE1, PGE2, PGF1alpha, PGF2alpha), ranging in concentration from 1 mu M to 1 mM. PGA1, at 1 mM, produced the greatest degree of inhibition, 39%. PG addition to microsomes, however, failed to alter PCMA metabolism. In contrast to PCMA biotransformation, Hechi metabolism was increased by all PGs in slices but not in liver subfractions. PGs of the E and F series were the most potent, producing a two-fold increase in Hechi metabolism at 1 mM after a 20 min preincubation. The increased effect was observed as early as 10 min and lasted for 4 hr. The relationship of PG metabolism and binding to cytochrome P-450 is presented as a possible mechanism to account for the opposite effects on Hechi and PCMA, type I and II substrates respectively, metabolism. 相似文献