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   9329篇
  免费   726篇
  国内免费   423篇
  10478篇
  2024年   22篇
  2023年   79篇
  2022年   236篇
  2021年   391篇
  2020年   271篇
  2019年   282篇
  2018年   316篇
  2017年   254篇
  2016年   374篇
  2015年   561篇
  2014年   617篇
  2013年   708篇
  2012年   802篇
  2011年   736篇
  2010年   465篇
  2009年   341篇
  2008年   476篇
  2007年   396篇
  2006年   380篇
  2005年   313篇
  2004年   270篇
  2003年   229篇
  2002年   225篇
  2001年   170篇
  2000年   187篇
  1999年   137篇
  1998年   84篇
  1997年   81篇
  1996年   77篇
  1995年   59篇
  1994年   63篇
  1993年   48篇
  1992年   90篇
  1991年   76篇
  1990年   77篇
  1989年   61篇
  1988年   47篇
  1987年   67篇
  1986年   45篇
  1985年   37篇
  1984年   33篇
  1983年   21篇
  1982年   25篇
  1980年   22篇
  1979年   26篇
  1978年   19篇
  1977年   21篇
  1975年   18篇
  1973年   21篇
  1972年   17篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
231.
BackgroundDespite availability of clinical practice guidelines for hypertension management, blood pressure (BP) control remains sub-optimal (<30%) even in high-income countries. This study aims to assess the effectiveness of a potentially scalable multicomponent intervention integrated into primary care system compared to usual care on BP control.Methods and findingsA cluster-randomized controlled trial was conducted in 8 government clinics in Singapore. The trial enrolled 916 patients aged ≥40 years with uncontrolled hypertension (systolic BP (SBP) ≥140 mmHg or diastolic BP (DBP) ≥90 mmHg).Multicomponent intervention consisted of physician training in risk-based treatment of hypertension, subsidized losartan-HCTZ single-pill combination (SPC) medications, nurse training in motivational conversations (MCs), and telephone follow-ups. Usual care (controls) comprised of routine care in the clinics, no MC or telephone follow-ups, and no subsidy on SPCs. The primary outcome was mean SBP at 24 months’ post-baseline. Four clinics (447 patients) were randomized to intervention and 4 (469) to usual care. Patient enrolment commenced in January 2017, and follow-up was during December 2018 to September 2020. Analysis used intention-to-treat principles. The primary outcome was SBP at 24 months. BP at baseline, 12 and 24 months was modeled at the patient level in a likelihood-based, linear mixed model repeated measures analysis with treatment group, follow-up, treatment group × follow-up interaction as fixed effects, and random cluster (clinic) effects.A total of 766 (83.6%) patients completed 2-year follow-up. A total of 63 (14.1%) and 87 (18.6%) patients in intervention and in usual care, respectively, were lost to follow-up. At 24 months, the adjusted mean SBP was significantly lower in the intervention group compared to usual care (−3.3 mmHg; 95% CI: −6.34, −0.32; p = 0.03). The intervention led to higher BP control (odds ratio 1.51; 95% CI: 1.10, 2.09; p = 0.01), lower odds of high (>20%) 10-year cardiovascular risk score (OR 0.67; 95% CI: 0.47, 0.97; p = 0.03), and lower mean log albuminuria (−0.22; 95% CI: −0.41, −0.02; p = 0.03). Mean DBP, mortality rates, and serious adverse events including hospitalizations were not different between groups. The main limitation was no masking in the trial.ConclusionsA multicomponent intervention consisting of physicians trained in risk-based treatment, subsidized SPC medications, nurse-delivered motivational conversation, and telephone follow-ups improved BP control and lowered cardiovascular risk. Wide-scale implementation of a multicomponent intervention such as the one in our trial is likely to reduce hypertension-related morbidity and mortality globally.Trial registrationTrial Registration: Clinicaltrials.gov NCT02972619.

Tazeen H Jafar and colleagues present findings from a cluster-randomized controlled trial conducted to evaluate the effectiveness of an intervention designed to manage hypertension.  相似文献   
232.
In view of the important roles played by Kinetochore proteins in mitosis, we believed that they may contribute to the development and progression of human cancers, which has been reported recently elsewhere. Kinetochore-associated 1 (KNTC1) participates in the segregation of sister chromatids during mitosis, the effects of which on non-small-cell lung cancer (NSCLC) remain unclear. Here, we sought to identify the biological significance of KNTC1 in NSCLC. KNTC1 protein expression in NSCLC tissues was investigated by immunohistochemistry. Lentivirus delivered short hairpin RNA (shRNA) was utilized to establish KNTC1 silence NSCLC cell lines. The effects of KNTC1 depletion on NSCLC cell proliferation, migration, apoptosis, and tumor formation were analyzed by MTT assay, wound-healing assay, transwell assay, flow cytometry assay, and in nude mouse models in vivo. After KNTC1 reduction, NSCLC cell viability, proliferation, migration, and invasion were restrained. A xenograft tumor model was also provided to demonstrate the inhibited tumorigenesis in NSCLC. In addition, the downstream mechanism analysis indicated that KNTC1 depletion was positively associated with PSMB8. The findings of the present study suggested that KNTC1 may have a pivotal role in mediating NSCLC progression and may act as a novel therapeutic target for NSCLC.Subject terms: Non-small-cell lung cancer, Cell migration  相似文献   
233.
234.
235.

Background, aim, and scope  

Propagation of parametric uncertainty in life cycle inventory (LCI) models is usually performed based on probabilistic Monte Carlo techniques. However, alternative approaches using interval or fuzzy numbers have been proposed based on the argument that these provide a better reflection of epistemological uncertainties inherent in some process data. Recent progress has been made to integrate fuzzy arithmetic into matrix-based LCI using decomposition into α-cut intervals. However, the proposed technique implicitly assumes that the lower bounds of the technology matrix elements give the highest inventory results, and vice versa, without providing rigorous proof.  相似文献   
236.
1. The L-amino acid oxidase, hyaluronidase, alkaline phosphomonoesterase, protease, phosphodiesterase, acetylcholinesterase, phospholipase A and 5'-nucleotidase activities of 47 samples of venoms from all the six species of cobra (Naja), including five subspecies of Naja naja, were examined. 2. The results demonstrated interspecific differences in the venom contents of phospholipase A, acetylcholinesterase, hyaluronidase and phosphodiesterase. These differences in venom enzyme contents can be used for the differentiation of species of the genus Naja. 3. Thus, our results revealed a correlation between the enzyme composition of venom and the taxonomic status of the snake at the species level for the genus Naja.  相似文献   
237.
Bacterial isolates from two environments, an integrated-farming pond in the university and palm-oil mill effluent (POME) ponds at a local palm-oil-processing factory, were screened for polyhydroxyalkanoates (PHAs). Initially Sudan Black B staining was performed to detect lipid cellular inclusions. Lipid-positive isolates were then grown in a nitrogen-limiting medium containing 2% (w/v) glucose to promote accumulation of PHA before the subsequent Nile Blue A staining. The PHA extracted from positive isolates was confirmed by nuclear magnetic resonance (NMR) spectroscopy. The proportion of PHA-positive bacterial isolates was higher in the POME ponds compared to the integrated-farming pond.  相似文献   
238.
239.
The climate (especially temperature) often plays an important role in the structure, function as well as composition of soil organisms in different latitudes and altitudes. As one of the essential components of soil ecosystem, soil faunal community not only lays their roles as soil engineer in material cycling and energy flow, but also acts as the sensitive bio-indicator to environmental change. However, little information has been available on the responses of soil faunal community to the changed environment at different altitudes and seasons. In order to understand the seasonal dynamics of soil faunal diversity under different forests with varying altitudes, three fir (Abies faxoniana) forests were selected covering a 600 m vertical transition zone. The primary fir forest at 3600 m (A1) of altitude, mixed fir and birch forest at 3300 m (A2) of altitude, and secondary fir forest at 3000 m (A3) of altitude are representative forests in the subalpine and alpine region of west Sichuan. A 2 years study was conducted in the three subalpine and alpine forests from May in 2009 until October in 2010. Soil samples were collected in both the soil organic layer and mineral soil layer. Soil macro-fauna were picked up by hand in the fields. Meso/micro-fauna and damp living fauna were separated and collected from the soil samples by Baermann and Tullgren methods in laboratory, respectively. A total of 74,827 individuals were collected in the 2 years, belonging to seven phyla, 16 classes, 31 orders and 125 families by preliminary identification. Similar dominant groups were detected in different forests at different altitudes, consisting of Spirostreptida, Formicidae, Staphylinidae, Hesperinidae, Onychiuridae, Isotomidae, Oribatuloidae, Alicoragiidae, Secernentea, and Adenophorea. In contrast, the ordinary species of macro-fauna and the ratios of Acarina to Collembolan were obviously different. For instance, the ordinary species were dominated by Cydmaenidae and Mycetophilidae at the A1, Scaphidiidae and Helicinidae at the A2, and Lumbricida and Agelenidae at the A3, respectively. Both the individual density and the number of soil faunal groups were significantly higher in soil organic layer than those in mineral soil layer. The density and group of macro-, meso- and micro-fauna in different forests showed the order as A2 > A1 > A3, but the density of damp living fauna showed the order as A1 > A2 > A3. The functional groups of macro-fauna were mainly dominated by saprozoic. The highest density and group of macro-fauna was observed in August, while the highest value of meso/micro-fauna was detected in October. In addition, the Jacard similarity indices showed that the composition and structure of soil fauna were similar in the different forests varied with altitudes, but the Shannon–Wiener indices were significantly different. The highest values of Shannon–Wiener indices were observed in October at both the A1 and A3, and in August at the A2. The results suggested that soil faunal community kept a high diversity in the subalpine and alpine forests of west Sichuan, and their structures were significantly affected by the variation of altitudes, which provided important scientific evidences for understanding the ecological processes in the subalpine and alpine coniferous forests.  相似文献   
240.
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