首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   2344篇
  免费   15篇
  国内免费   1篇
电工技术   6篇
化学工业   197篇
金属工艺   9篇
机械仪表   21篇
建筑科学   74篇
矿业工程   1篇
能源动力   18篇
轻工业   94篇
水利工程   11篇
石油天然气   5篇
无线电   161篇
一般工业技术   117篇
冶金工业   1515篇
原子能技术   16篇
自动化技术   115篇
  2021年   14篇
  2019年   8篇
  2018年   8篇
  2017年   7篇
  2016年   10篇
  2014年   15篇
  2013年   49篇
  2012年   18篇
  2011年   26篇
  2010年   17篇
  2009年   28篇
  2008年   32篇
  2007年   33篇
  2006年   31篇
  2005年   32篇
  2004年   21篇
  2003年   25篇
  2002年   29篇
  2001年   24篇
  2000年   30篇
  1999年   49篇
  1998年   487篇
  1997年   236篇
  1996年   166篇
  1995年   112篇
  1994年   91篇
  1993年   113篇
  1992年   29篇
  1991年   28篇
  1990年   37篇
  1989年   40篇
  1988年   30篇
  1987年   17篇
  1986年   35篇
  1985年   25篇
  1984年   22篇
  1983年   11篇
  1982年   17篇
  1981年   21篇
  1980年   35篇
  1979年   19篇
  1978年   20篇
  1977年   43篇
  1976年   104篇
  1975年   14篇
  1974年   11篇
  1973年   14篇
  1972年   7篇
  1970年   8篇
  1966年   7篇
排序方式: 共有2360条查询结果,搜索用时 15 毫秒
91.
Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) expression is increased in Dunning R-3327 rat prostatic adenocarcinoma cell lines relative to normal rat ventral prostate tissue. GAPDH expression closely correlates with cell motility of Dunning prostate cancer cell lines and accurately distinguishes cell lines with high metastatic potential from those with low metastatic potential. Increased GAPDH expression in the cancer cell lines is not simply related to increased growth rate, since rapidly proliferating normal prostate tissue did not exhibit elevated GAPDH expression.  相似文献   
92.
Colostrinin: a proline-rich polypeptide (PRP) from ovine colostrum and its nonapeptide active fragment (NP) induce maturation and differentiation of murine thymocytes, formation of helper cells from PNAhigh thymocytes and cytotoxic T cells from PNAlow thymocytes. These processes are accompanied by changes in expression of receptors for peanut agglutinin (PNA), PNAhigh thymocytes were transformed into PNAlow cells, and vice versa. It was shown, in various laboratories, that sialyltransferases are involved in the transformation of PNAhigh thymocytes into PNAlow cells. To find out whether the expression of receptors for PNA on murine thymocytes might also be influenced by other enzymes, we decided to study the effect of PRP and NP on sialidase and beta-galactosidase activities in these cells. The results obtained showed that the most of sialidase activity of murine thymocytes is present in the plasma membrane compartments. Both thymocyte subpopulations PNAhigh and PNAlow, showed similar sialidase activity, which was not affected either by PRP or NP. In contrast to sialidases, most of beta-galactosidase activity was present in the cytosol. PNAhigh, thymocytes showed a higher beta-galactosidase activity than PNAlow cells. Incubation of immature, PNAhigh, thymocytes with PRP or NP enhanced the beta-galactosidase activity in these cells. The presented results suggest that sialidases seem not to be involved in modulation of surface sialic acid content during murine thymocyte maturation. On the other hand, stimulation of activity of beta-galactosidase in PNAhigh, immature thymocytes by PRP and NP suggests that beta-galactosidase in murine thymocytes might be involved in transformation of PNAhigh into PNAlow cells.  相似文献   
93.
Pustulosis palmoplantaris (PPP) is a common chronic skin disease, which is very resistant to treatment. It is not known why the lesions are located in the palms and soles. There are few studies of the disease and in particular studies of the histology. Fifty-nine patients with PPP answered a questionnaire concerning their medical history and 39 of them were clinically examined. Biopsy specimens were taken from involved skin in 22 of the 39 patients and studied immunohistologically for tryptase+ mast cells, EG2+ eosinophils, lipocalin+ neutrophils and CD3+ T lymphocytes. The sweat gland and sweat duct were visualized with AE1/AE3 antibody (cytokeratins 1-8, 10, 14/15, 16, 19). In addition to neutrophils in the pustule and lymphocytes in the upper dermis, there were also large numbers of mast cells and eosinophils in the subpustular area. Numerous eosinophils were present in the pustule. The epidermal part of the eccrine duct was not detectable in any of the specimens from patients with PPP but was present in all of the nine control persons (including two smokers). The results indicate that the acrosyringium is involved in the inflammation and also that mast cells and eosinophils participate in a hitherto unknown way. Of the 39 patients clinically examined, two had previously diagnosed thyroid disease and two had gluten hypersensitivity. Seventeen had one or several abnormal serum concentrations of thyroid-stimulating hormone, thyroxin, antibodies against thyroglobulin or thyroperoxidase and 10 had immunoglobulin (Ig) A antibodies to gliadin. The mean +/- SD for serum IgA and for eosinophil cationic protein was increased. From the questionnaire the most notable finding was that 56 of the 59 patients had been or still were smokers, all of whom had started smoking before the first signs of PPP. We hypothesize that the acrosyringium might be the target for the inflammation and that PPP is linked to autoimmune thyroid disease and smoking.  相似文献   
94.
Metabolic bone disease was diagnosed in an 11-month-old female common marmoset (Callithrix jacchus). It was depressed, reluctant to move, and was cachectic and small for its age. Laboratory findings included anaemia, azotaemia and an inverse calcium to phosphorus ratio. The radiological findings showed simultaneous signs of osteomalacia and soft-tissue calcification. There was decreased bone density with lytic areas in the pelvis and femur, and severe bilateral nephrocalcinosis. Postmortem examination revealed marked focal dystrophic calcification of the epi- and myocardium. Calcium and vitamin D3 deficiency (nutritional secondary hyperparathyroidism) was the most likely cause of the osteomalacia.  相似文献   
95.
The authors present a patient with complete laryngotracheoesophageal cleft and concurrent left lung agenesis and microgastria. Prenatal ultrasound scan showed polyhydramnios and a hypertrophic right lung. The authors propose that the combination of right lung hypertrophy, polyhydramnios, and microgastria in the absence of a competent laryngeal mechanism may suggest that the preferential path for swallowed amniotic fluid was into the lung, rather than the normal route through the stomach. This case illustrates the prenatal findings suggestive of complete laryngotracheoesophageal cleft and lung agenesis, and suggests a potential causal relationship between shunting of swallowed amniotic fluid into the bronchial tree and prenatal lung hypertrophy and microgastria.  相似文献   
96.
97.
Multiple myeloma (MM) is usually characterized by production of a single serum monoclonal protein of constant isotype and light-chain restriction. Multiple Ig isotypes and isotype switches, which are rare in untreated patients, are reported to be more common in patients undergoing myeloablative therapy. These additional protein bands, detected by immunofixation electrophoresis (IFE), could be due to altered paraprotein production by the malignant plasma cell clone or oligoclonal Ig production during recovery of B-cell function after myeloablative therapy. We analyzed abnormal protein bands (APB), distinct from the presenting paraprotein, in 550 patients receiving high-dose therapy with autologous hematopoietic cell transplantation at a single institution. Fifty-five patients (10%) had APB, 48 had oligoclonal bands (OB), and 23 had an apparent isotype switch (IS) on IFE (16 had both OB and IS). Morphologic and flow cytometric examination of bone marrow in 17 patients with IS showed no evidence of a clonal plasma cell isotype switch. Patients with APB had significantly higher complete response to therapy (67% v 37%, P = .001). To assess the independent prognostic relevance of APB, a multivariate analysis was performed among 471 patients surviving at least 12 months from first transplant (all patients developing APB had done so by 12 months from first transplant). APB (in 50 patients) was a favorable feature for both event-free (rank 3, P = .004) and overall survival (rank 3, P = .0005). We propose that OB and IS are likely to be due to recovery of Ig production rather than alterations in the biology of the malignant plasma cell clone.  相似文献   
98.
C3H (H2k) mice received 50 x 10(6) B10 (H2b) bone marrow (BM) cells either alone or with flt-3 ligand (FL) (10 microg/day), tacrolimus (2 mg/kg/day), or both agents for 7 days. Donor MHC class II+ (IAb+) cells were quantitated in spleens by immunohistochemical analysis, and donor class II DNA detected in BM by PCR. Donor cells were rare in the BM alone and BM + FL groups, whereas there was a substantial increase in chimerism in the BM + tacrolimus group. Addition of FL to BM + tacrolimus led to a further eightfold increase in donor cells and enhanced donor DNA compared with the BM + tacrolimus group. This increase in donor cells was almost 500-fold compared with BM alone. C3H recipients of B10 heart allografts given perioperative B10 BM and tacrolimus (days 0-13) exhibited a markedly extended median graft survival time (MST, 42 days) compared with those given tacrolimus alone (MST, 22 days). Addition of FL (10 microg/day; 7 days) to BM + tacrolimus prevented the beneficial effect of donor BM (MST, 18 days). BM alone or BM + FL resulted in uniform early heart graft failure (MST < 8 days). Functional studies revealed maximal antidonor MLR and CTL activities in the BM- and BM + FL-treated groups, with minimal activity in the tacrolimus-treated groups. Thus, dramatic growth factor-induced increases in chimerism achieved under cover of immunosuppression may result in augmented antidonor T cell reactivity and reduced graft survival after immunosuppressive drug withdrawal. With FL, this may reflect striking augmentation of immunostimulatory dendritic cells.  相似文献   
99.
We report an iatrogenic corneal ectasia that developed after laser in situ keratomileusis (LASIK) in a case of forme fruste keratoconus. One month postoperatively, corneal topography revealed a central steep area that showed rapid progression. Visual acuity in the eye decreased from 20/20 to 20/80. Corneas with forme fruste keratoconus may have altered biomechanical properties compared with normal corneas. Forme fruste keratoconus may be a contraindication for LASIK.  相似文献   
100.
Turner syndrome is the complex human phenotype associated with complete or partial monosomy X. Principle features of Turner syndrome include short stature, ovarian failure, and a variety of other anatomic and physiological abnormalities, such as webbed neck, lymphedema, cardiovascular and renal anomalies, hypertension, and autoimmune thyroid disease. We studied 28 apparently nonmosaic subjects with partial deletions of Xp, in order to map loci responsible for various components of the Turner syndrome phenotype. Subjects were carefully evaluated for the presence or absence of Turner syndrome features, and their deletions were mapped by FISH with a panel of Xp markers. Using a statistical method to examine genotype/phenotype correlations, we mapped one or more Turner syndrome traits to a critical region in Xp11.2-p22.1. These traits included short stature, ovarian failure, high-arched palate, and autoimmune thyroid disease. The results are useful for genetic counseling of individuals with partial monosomy X. Study of additional subjects should refine the localization of Turner syndrome loci and provide a rational basis for exploration of candidate genes.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号