全文获取类型
收费全文 | 5674篇 |
免费 | 530篇 |
国内免费 | 305篇 |
专业分类
电工技术 | 575篇 |
综合类 | 437篇 |
化学工业 | 531篇 |
金属工艺 | 364篇 |
机械仪表 | 321篇 |
建筑科学 | 291篇 |
矿业工程 | 176篇 |
能源动力 | 131篇 |
轻工业 | 578篇 |
水利工程 | 158篇 |
石油天然气 | 173篇 |
武器工业 | 32篇 |
无线电 | 428篇 |
一般工业技术 | 324篇 |
冶金工业 | 1400篇 |
原子能技术 | 75篇 |
自动化技术 | 515篇 |
出版年
2024年 | 29篇 |
2023年 | 82篇 |
2022年 | 214篇 |
2021年 | 219篇 |
2020年 | 184篇 |
2019年 | 123篇 |
2018年 | 132篇 |
2017年 | 165篇 |
2016年 | 138篇 |
2015年 | 224篇 |
2014年 | 274篇 |
2013年 | 294篇 |
2012年 | 384篇 |
2011年 | 333篇 |
2010年 | 350篇 |
2009年 | 329篇 |
2008年 | 388篇 |
2007年 | 325篇 |
2006年 | 280篇 |
2005年 | 206篇 |
2004年 | 185篇 |
2003年 | 118篇 |
2002年 | 111篇 |
2001年 | 113篇 |
2000年 | 73篇 |
1999年 | 44篇 |
1998年 | 282篇 |
1997年 | 201篇 |
1996年 | 146篇 |
1995年 | 78篇 |
1994年 | 49篇 |
1993年 | 69篇 |
1992年 | 16篇 |
1991年 | 11篇 |
1990年 | 8篇 |
1989年 | 11篇 |
1988年 | 15篇 |
1987年 | 13篇 |
1986年 | 7篇 |
1985年 | 8篇 |
1982年 | 7篇 |
1981年 | 14篇 |
1980年 | 21篇 |
1978年 | 3篇 |
1977年 | 63篇 |
1976年 | 136篇 |
1975年 | 5篇 |
1965年 | 5篇 |
1958年 | 5篇 |
1951年 | 2篇 |
排序方式: 共有6509条查询结果,搜索用时 0 毫秒
101.
In a study of 80 cases of lymphogranuloma venereum (LGV), minocycline hydrochloride (Minocin) was found to be an effective drug in the treatment of all stages of LGV, including complicated ones. In late cases adjuvant treatment was used in addition to the antibiotic. Healing time in uncomplicated cases was less than 10 days. In complicated cases, both early and late, healing took about 2 to 3 weeks. Reactions to the drug were not significant. 相似文献
102.
The area under the liver was dissected in 27 human autopsy specimens to search for lymph nodes in the fissures. Nodes were present in all instances. They were in the transverse fissure, posterior to the portal vein, posterior to pars transversus of the left portal vein and associated with the left hepatic artery. The size varied from 2 millimeters to 2 centimeters. Each node was histologically confirmed. Nodes were infrequent and small on the right. Nodes were not found between the portal vein, hepatic artery and bile ducts in the fissures. Nodes were found outside the fissures in the fascia between the bile duct and hepatic artery. Occlusion of the portal vein and hepatic artery could be expected before occlusion of the bile duct. Node enlargement in the transverse fissure is anticipated as a rare cause of jaundice. 相似文献
103.
Circulating plasma progesterone (P) has been quantitatively controlled in the rat "model" through highly specific binding by treatment with anti-P (A-P). Knowing the constant, which characterizes the binding of P to A-P in plasma, sequential assays of circulating A-P and A-P bound total P (Pt) revealed the levels of the biologically active unbound P (Pu). The studies showed that at different stages of gestation the mechanisms through which A-P reduces Pu and terminates pregnancy are the same. However, the doses of AP which effectively reduce Pu and also the critical levels of Pu at which pregnancy terminates are different. The moderate and transient physiologic P-withdrawal (Pw) at midterm permits the continuation of normal gestation, but pregnancy is terminated by a drastic and sustained reduction in Pu. In contrast, when Pu is only slightly and briefly reduced below physiologic levels, pregnancy continues and only retarded conceptus growth signals that Pw occurred. Apparently Pw has to be controlled and measured with "razor's-edge" precision to fully expose and define the regulatory significance of this steroid in the maintenance and termination of pregnancy. Short of this precision, the key regulator of the pregnant uterus will remain buried, as it has been during 40 years, in controversial findings. 相似文献
104.
MG Astapenko W Otto TM Trofimowa H H?ntzschel B Tautenhahn D Reinelt H Treutler AI Speranskij NM Mylow WA Duljapin TA Tarasenkowa 《Canadian Metallurgical Quarterly》1976,31(16):641-646
On the basis of own observations of courses the author adopts a definite attitude to the early symptomatology of the rheumatoid arthritis. During the first weeks of the rheumatoid arthritis the following symptoms are found: articular syndromes, more frequently in form of obstinate polyarthralgias, mono-oligoarthritis, accompanied by morning rigidity and accelerated BSR as well as impairment of the general condition. In the majority of the patients only the tentative diagnosis rheumatoid arthritis may be made. After a one to three months' course of the disease the diagnosis becomes more probable. It is above all based on constancy and symmetry, characteristic localisation of the articular process, morning rigidity, radiologically paraarticular loosening of the structure and morphological symptoms of an acute and subacute synovialitis. 6 to 12 months after the beginning of the disease a clinical picture forms which allows to make the diagnosis of a certain or classical rheumatoid arthritis in accordance with the criteria of the ARA. The occurrence of a high activity of multiple affection of the joints (permanent symmetrical polyarthritis including the small joints of the hands and feet), distinctive morning rigidity, high fever and much accelerated BSR, beginning with the first weeks of the disease, speaks for the possibility of the development of an arthrovisceral form of the course of rheumatoid arthritis. 相似文献
105.
106.
OA Kovalev AI Gurbanova SK Sheremetevskaia ON Nepochatov 《Canadian Metallurgical Quarterly》1976,82(9):1045-1047
The authors describe relative changes in the blood filling of 46 vascular areas of the body in rats after a moderate and severe blood loss. Moderate blood loss caused redistribution of the blood from the skin of the chest and from the skin of the posterior limbs, the majority of the abdominal and pelvis minor organs, muscular and bone tissues of the abdomen, pelvis minor and extremities into the brain, heart, lungs, kidneys, stomach and into the muscles of the head and neck. In severe blood loss the changes were analogous, but the blood content in the kidneys and the stomach decreased, and there was also a relative elevation of the blood in the muscles and bones of the chest. The intensity of the redistributive reaction in severe blood loss was less than in moderate blood loss. 相似文献
107.
SG Massry R Stein J Garty AI Arieff JW Coburn AW Norman RM Friedler 《Canadian Metallurgical Quarterly》1976,9(6):467-474
Studies were carried out to investigate the role of 1,25(OH)2D3 in the skeletal resistance to the calcemic action of parathyroid hormone. The change in serum calcium after the intravenous infusion of 2 U of parathyroid extract (PTE)/kg body wt/hr for eight hours was evaluated in thyroparathyroidectomized (T-PTX) dogs before, and one, two and three days after, induction of uremia by bilateral ureteral ligation (11 dogs) or by bilateral nephrectomy (8 dogs). In another six nephrectomized and T-PTX dogs, 0.68 ug of 1, 25 (OH)2D3/day was given on the day of nephrectomy and for two days thereafter. Serum creatinine in each day of the study was not different among the three groups. The study also included the evaluation of the effect of sham operation (five dogs) and the administration of 1,25 (OH)2D3 to dogs with normal renal function (four dogs) on the calcemic response to PTE, as well as the reproducibility of such a response in the same animal. The results showed that 1) the calcemic response to PTE was markedly impaired after one day of bilateral ureteral ligation or nephrectomy, but the impairment was more severe after nephrectomy; 2) the calcemic response to PTE after two or three days of bilateral ureteral ligation was similar to that seen at one day after nephrectomy; 3) 1, 25 (OH)2D3 partially restored the calcemic response to PTE in the nephrectomized animals to levels similar to those seen after one day of bilateral ureteral ligation; 4) sham operation did not affect the response to PTE, and repeated infusion of PTE produced similar changes in the concentrations of serum calcium. The data indicate that (a) a deficiency of 1,25 (OH)2D3 is at least partly responsible for the skeletal resistance to the calcemic action of PTH in uremia; (b) uremia, per se, may also contribute to this phenomenon; and (c) the kidney after one day of complete bilateral ureteral ligation may still produce 1,25 (OH)2D3, but this ability is compromised after two days of ureteral obstruction. 相似文献
108.
Arterial blood pressures were taken by the Doppler ultrasound method in 134 unselected mature neonates (birthweights 2,600-3,900 grams) who were managed in the same manner after birth. Blood pressures were measured at 3-5, 10 and 30 minutes of life and, if indicated, intermittently during the next 24-48 h. Left and right arm pressures were identical or differed by only 1-2 mm Hg. Lower than normal blood pressures were found in 4 groups of infants: those born by cesarean section, those recovering from intrauterine asphyxia, those exposed to maternal anti-hypertensive therapy, and those whose mothers received thiopental within four minutes of delivery. Return of the low pressures to within the normal range was fastest following thiopental induction in the absence of fetal asphyxia and slowest after antihypertensive therapy. 相似文献
109.
AI Shul'mina VIa Cherniak NN Magretova EL Malova LA Dronova 《Canadian Metallurgical Quarterly》1976,41(7):1229-1234
Serine proteases inhibitor with pl-7.3, isolated from potatoe tubers by isoelectric focusing procedure as described previously (V.V. Mosolov et al., Bioorganic Chem., 1, 1449, 1975), was homogeneous under ultracentrifugation, having sedimentation coefficient S20,w 2.8S. Its molecular weight, investigated by sedimentation equilibrium and gel filtration through Sephadex G-100, was found to be 32500 and 31500 respectively. The Stokes radius R and frictional ratio f/fo were found to be 24 A and 1.14. The molecular weight of the inhibitor as determined by sodium dodecylsulfate polyacrylamide electrophoresis was twice as low as determined in ultracentrifuge and by gel filtration procedure. It is suggested that the inhibitor is dimer and consists of two protomers of equal molecular weight. 相似文献
110.
Binding of 17beta-estradiol with histones of calf thymus and the influence of the hormone on heart denaturing of partially reconstructed nucleohistones were investigated. By the degree of the hormone binding histone fractions could be arranged in the following order: F2a greater than F3 greater than F1 greater than or equal F2b. Addition of 17beta-estradiol gave rise to increase of the first and a corresponding decrease of the second melting phase of partially reconstructed nucleohistones F2a, F3 and F2b. Addition of the hormone to the partially reconstructed nucleohistone F1 gave rise to the opposite changes in the heat denaturing profile. 相似文献